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HPH335 : Designing an intentional community – with Anne Thorne

HPH335 : Designing an intentional community – with Anne Thorne

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Anne Thorne talks through the architectural design process of Cannock Mill Cohousing community.

Interview with Anne Thorne

We first featured Cannock Mill Cohousing in a podcast with Phil McGeevor, the Chair of the group, who explained how the group formed and the process they followed. Another key member of that group, Anne Thorne, is not only the architect who designed the scheme but also a resident of their cohousing community. Anne became an architect at a time when only 5% in that profession were female, and felt that as well as a lack of representation in the studio, there was generally a lack of consultation with women in the design process. She emphasises the importance of consultation, really listening to and understanding people's ideas and designing in an environmentally conscious way.

Cohousing is an intentional community

It is a community where people come to live together, but in their own independent homes. There is a common house where residents can meet, cook, watch TV together, party etc. It also has bedrooms where guests can stay. By sharing lots of facilities, the intention is that residents can have a smaller home of their own.

Beyond the common house, they also grow produce together and have a travel club for car and lift-sharing.

Discreet spaces are as important as shared ones

Each house or flat owner has their own outdoor space, whether that's a balcony or a small terraced garden. Discreet spaces have also been designed into the community areas, with seating in parts of the garden if people are looking for privacy.

10 years of looking for a site will see people pull out!

Searching for a suitable and mutually agreeable site can be a lengthy process, but the point at which they selected the site (10 years on) was actually the point at which several people decided to pull out. Reasons included location, risk and budget.

“And in fact, eight of us bought the site, eight households that is, which cost 1.2 million. That was a really big step for everybody to put up that money. People got mortgages on their houses, did all sorts of things in order to make that happen, which was a fantastic leap of faith really, and one that lots of people couldn't make.”

A particular risk at that time was that only eight households paid for the site: a site which had planning for 23 homes, and would need to be developed with 23 homes.

A series of sub-groups report to the main board

These sub-groups included legal, finance and building. They would all report to the main board which was responsible for decision-making.

Once Anne Thorne Architects had been appointed, Anne distanced herself entirely from the committees and groups that dealt with finance or decision-making around anything that might affect her tenure as the architect. Luckily for her, many people on the building sub-group, which acted as the client, had experience of being clients in big organisations and understood what her role was and the complexities of keeping that separate from her involvement as a member of the community. Both she and the building group for example, were very clear that she wouldn't be involved in any of the voting around building matters.

The building group were also insistent that if anyone wanted changes making to their houses, that they raise it with the group and Anne directly, rather than the builders on site. It would have been easy for a member to tell a builder that they didn't like the flooring, and the builder then to assume that meant the flooring was changing for everyone!

Developers will be competing to buy the same site

One of the reasons that the search was protracted, was that as soon as they found a suitably flat and workable site, it would be snapped up by a developer. What held them back as a group was they couldn't move fast enough with their finances. They also lost out on sites because developers and housing associations already had links with the local authorities.

They didn't want an isolated site

The group's main criteria for a site was that it should:

  • have planning for between 15 and 30 dwellings
  • be located within an hour and a half from London
  • be well located for local facilities without needing a car

After 10 years of searching, they found the Cannock Mill site on Right Move. They knew it would have its challenges (it was steep and fairly waterlogged), but it also housed a lovely mill, was a 20 minute walk into Colchester, with countryside walks, village shops and a bus stop at the doorstep.

The houses were designed to Lifetime Home Standards

With the original eight households needing to decide what size and layout future members might want, they decided to design the houses to Lifetime Home Standards, and the minimum housing sizes of the Greater London Authority standards.

This meant that they were more generously sized than developer homes, but perhaps not as generous as if a private client might build for themselves.

Accessibility was a key consideration and all the three-storey houses have space for a lift to be installed. Bathrooms are large enough to be accessible, with the adaptability of being able to install a hoist if necessary in the future.

Standardised finishes were used across all the houses

This meant they all had bamboo flooring, were painted white, and had the same baths/showers, taps and basins. By all agreeing to have the same finishes, they understood it would be a lot cheaper and more sustainable. Members would be free to redecorate if they wanted to afterwards.

Prices exceeded the contingency sum by 1%

With such a long time between concept and delivery of the scheme, budgets inevitably changed considerably. Prices on site also went up, not least because building work overran by a year.

There was also a very steep learning curve with builders and sub-contractors having never worked on a Passivhaus scheme before. In hindsight for example, Anne says that they should have insisted on the suppliers of the triple-glazed windows and doors doing the installation.

The scheme is on piled foundations

With spring water and a pond on the site, a lot of work has been undertaken to direct the water. Being so wet and with variable ground conditions, the scheme uses piled foundations over 25 metres deep in places. A concrete slab, insulation and screed sit on top of the foundations.

The timber frame is faced on both sides with either wood fibre board or plywood. The inner face has an airtight layer of smart ply with newspaper insulation blown through. It is finished with a wood fibre panel and coloured render. With a colour palette to choose from, residents had to negotiate with their neighbour to make sure they didn't have the same colour!

The roof construction is designed to absorb almost as much water as the site did before the houses were built. This also means that they have a reduction in their water bills because no water goes into the surface drains from the houses.

Upside-down living takes advantage of the daylight

With a steep north-facing slope, everyone had concerns that the living rooms wouldn't have enough daylight. So, the houses were designed with open plan kitchen / living rooms on the top floor. They all face the communal house too.

Listed status on the mill prevented it from being a Passivhaus retrofit

The conservation officer wouldn't allow any changes of the windows. Instead, they've used secondary glazing. The larch timber boarding was removed and insulation fitted between the studs. An airtightness layer was added to allow the structure to breathe, before insulated board was put on top and the cladding returned. The wood burning stove they fitted has been largely redundant, because it's so well insulated.

People have invested in the community, not just the scheme

Because people have been involved from the beginning, they have also been invested in their faith and understanding of each other. They have got to know and trust one another. They have had to develop ways of working together. Although Anne acknowledges, being such a consolidated community can make it slightly harder for newcomers.

Find out more

Visit the website of Anne Thorne Architects

Get information about cohousing from the UK Cohousing Network

One to check out from our archives: Can a straw bale house reach Passivhaus standard? – with Fran Bradshaw from Anne Thorne Architects

Transcript

Download a transcript of the interview with Anne Thorne

Other podcasts about cohousing

The benefits of joining a cohousing development (Marmalade Lane Cohousing)

How to make a cohousing scheme a reality (Cannock Mill Cohousing)

Setting up a cohousing scheme (Marmalade Lane Cohousing)

Low impact living affordable community (LILAC)

How cohousing helps build a community (Lancaster Cohousing)

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Subscribe, rate and review us on Apple Podcasts

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HPH331 : What is a mechanical services engineer? – with Alan Clarke

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Alan Clarke explains the role of a mechanical services engineer on a low energy house build, in designing a heating and ventilation system that works efficiently and is affordable.

Interview with Alan Clarke

We've been fortunate enough to have Alan Clarke on the podcast before. Back in episode HPH062 we discussed with him whether a Passivhaus needs a heating system. In a later episode, he also explained the designs for the heating, ventilation, and hot and cold water systems for Ben's own self build.

Today, we welcome him back to conclude our mini-series, looking at different professions that we may need on our self build or retrofit project. Alan is a mechanical services engineer, with particular expertise in Passivhaus buildings.

Most mechanical services engineers will have a background in engineering

A mechanical services engineer will cover the design of the heating and ventilation systems of a building. Some practices would also do M&E (mechanical and electrical) or MEP (mechanical engineering and public health) work, which would cover all of the building services. As well as the heating and ventilation, that will be the electrical services, drainage and plumbing too. The majority of people practicing it professionally would come from an engineering training background.

Relevant parts of the building regulations are Part L and Part F

Part L of the building regulations covers the energy of the house as a whole, including the heating system. An electrical installer would be expected to be qualified and understand how to install a system that is going to be in line with the wiring regulations and building regulations compliance. This might include energy modeling of the building too.

Part F of the building regulations is to do with ventilation. Ventilation systems in houses are relatively new, and there isn't quite the same level of qualification and supervision.

Pre-planning is the ideal time to involve your mechanical services engineer

Not all architects will be familiar with integrating a mechanical ventilation system so that it works efficiently and is easy to maintain. There would be some spacial requirements at Stage 3 of the RIBA Stage of Works, but pre planning is the ideal time for an engineer to come in and think about where the main items of equipment are going to be located, and how the distribution through the building will work. Consideration also needs to be given in the design to accommodate the ductwork, although the detailed design for that would come later. If it's for a Passivhaus, there will also need to be PHPP energy modeling at this stage, before the planning application goes in. This will have an impact on the form of the building, window sizes, etc.

It is important to make sure the overall system is efficient

The energy efficiency of the overall system can be broken down into separate parts:

  • The MVHR unit – this must be an efficient piece of kit with good heat recovery efficiency and quiet, efficient fans. If the fans aren't quiet, people won't use it.
  • Good ductwork design – fan performance can be scuppered by putting in ducts that are too small, which means the fans have to work harder. They use more energy to run, and you get more noise. A good approach to the design of the ductwork is therefore important.

A further consideration in the Passivhaus analysis is heat loss, looking at how long the ducts are, and also how well insulated they are. Ideally, these should be as short as possible, just one or two metres length, which has implications on where to position the MVHR.

An MVHR unit also needs to have regular filter changes. Therefore, there's no point putting it somewhere inaccessible, where you can't see what you're doing!

There are two main ducting systems

The basic principles of a balanced mechanical ventilation system, are to bring in and supply fresh air to the rooms where we spend the most time, and take out stale air, particularly from the smelliest and wettest parts of the building. The extracted air passes through the MVHR which has a heat exchanger. This transfers practically all the warmth from that extracted air to the incoming air. Ductwork connects the ventilation unit to the rooms in the house.

A radial system uses lots of separate ducts that run to each room. If you want more air to go to or from a particular room then you run two ducts. Also, if it's got a long way to go, you might increase the number of ducts to a distant room to make it easier to get air from there to the MVHR.

The other system used is a branched system. You start with the biggest duct at the MVHR and run to the first room. At this terminal, it tees off to another room before branching off again, and so on. The duct size reduces as you go along.

Generally, the radial system ducts will have a diameter of 75 or 90mm, which is easier to thread through than the branched system, but you do need more of them. The branched system starts off at around 150-160mm, before dropping down to 100mm for individual rooms.

Space for the ducting will need to be allowed for in the structural and architectural design of the building, so it's good to know what system is going to be used as early as possible.

Air should be supplied into the rooms in a way that you don't feel a draft

For a flat ceiling, there would normally be a disc in the ceiling that spreads the air horizontally so that you don't feel it blowing on you.

The other type of supply valve is designed to go in a wall. This also spreads the air horizontally. The air flows are relatively small and mix with the room air quite quickly, meaning it's unnoticeable to occupants.

Around 2.5 litres of moisture is generated into the house per person per day

This is produced in a number of ways, such as:

  • Breathing and perspiration – this accounts for around a fifth of the moisture that we put in the house
  • Bathing – not just the hot water steam but also the towel and bath mat will continue drying back out into the room too
  • Water evaporation from the dishwasher drying cycle
  • Cooking – such as steam from boiling water
  • Laundry – drying washing indoors can mean there are several kilos of moisture that have to go somewhere

Without some way of extracting all this moisture, that's a lot of water that is just sitting in our houses. It can however be extracted through ventilation. Even on a wet day, the water vapour content of the external air is relatively low, and much less than the air indoors. Simply by bringing it in and exhausting the same volume of inside air, you can expel the water vapour.

Part F of the building regulations has guidance for calculating the ventilation flow rate that's needed. This is inferred from the number of bedrooms. A Passivhaus calculation is more specific and done on a per person basis.

It is more efficient to run the ventilation constantly

Many houses in the UK have intermittent extract fans, which just draw the vapour out when you have a bath or shower. Evidence shows however that this isn't effective in reducing humidity levels enough, leading to condensation and mould potential.

A house with an MVHR does focus on the wet areas, but has the ventilation running all of the time. There's not much to be gained by turning it off, as you're not losing any heat through it. Keeping the low power fans running continuously, rather than being off and then having to work hard for a while, is more energy efficient.

The primary benefit is to our health

Through living in an enclosed space, we generate a number of pollutants, some of which are a side effect of the moisture. The condensation and mould can be extremely detrimental to our health. Even at lower humidity levels dust mites can prevail, causing allergic reactions and asthma.

By ventilating a building we can also dilute and remove the VOCs and chemicals in the air that inevitably come out of the products.

Heat pump systems need to be designed carefully

Traditionally, a gas boiler with radiators has been a fairly resilient system for heating. Also, it's one which doesn't need too much oversight from an installer or heating engineer.

Although a Passivhaus only requires a small amount of heat, this will need to be delivered somehow. Alan commonly specifies heat pumps these days, however, he stresses that they must be designed and installed well.

Put a hot water cylinder where you are going to be using your hot water

It sounds obvious but is an important consideration. Positioning the cylinder centrally to where the hot water will be needed in the kitchen and bathrooms, means that you can have shorter pipe runs. Subsequently, there will be less heat lost through the pipes, and the hot water will reach the taps more quickly.

Most of a mechanical services engineer's work is before construction

A typical day for a mechanical services engineer might involve:

  • A discussion with the client to understand their requirements and how they might live in their house
  • A review of architect's designs
  • Planning the building services, distribution, emitters, ventilation terminals and key bits of plant on the layout drawings
  • Drawing up a specification. This is the shopping list for the contractors for the equipment needed. Also, it's the particular requirements for the installation, workmanship and commissioning
  • Working on the drawings/revisions – looking at where ventilation and hot water kit will go, positioning a heat pump, and considering any constraints around where that might go

When a client is building a house for the first time, the plans can sometimes evolve later in the process as they think more about what they really want. Ideally you should be executing the plans you have developed in the design stage during the construction stage, not altering them. This will make it harder for the whole team and more expensive for you.

Your mechanical services engineer needs to understand your priorities

They should listen and understand what their brief is. It's not helpful to have someone come in with preconceived ideas of a technically complicated piece of engineering, when the client just wanted something simple. It's a waste of their time and money.

Ideally, you also want your engineer to have enough experience to be able to look back on other projects to see what has and hasn't worked well.

Find out more

Follow Alan Clarke on Twitter

Transcript

Download a transcript of the interview with Alan Clarke

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

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HPH330 : What is a planning consultant? – with Andy Moger

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Andy Moger, from Tetlow King Planning, explains the role of a planning consultant and the benefits they can bring to a project.

Interview with Andy Moger

Andy is a planning consultant for Tetlow King Planning: a planning and development company based in Bristol that operates nationwide.

A number of years ago he worked on the government's first pilot scheme for self and custom build – the Heartlands project in Cornwall. Following that, he became more involved in the self and custom build sector, primarily doing work for the Right to Build taskforce. Nowadays, this sector is all he works on, dealing with applications, appeals and site promotions, ranging from single dwellings to larger developments and appeal work for some of the big house builders and strategic land promoters.

Not all building projects will require planning approval

It is possible to use ‘permitted development' rights for work like small extensions and loft conversions, depending on the extent of the area you're adding to your property.

The ‘prior approval' process typically applies to larger extensions. You inform the council who will notify your neighbours. If there haven't been any objections after a period of time then you're deemed to have consent.

Local plans control development in each area

Each council has to have a local plan; sometimes called a district plan or core strategy. These set out a strategic approach for that area for the next 15-20 years, and contain the policies that control development. If you're looking to get planning permission on a particular piece of land you will need to check your local plan to see how you fit with those policies, or how you might overcome any potential issues.

All of these plans will work on the basis of concentrating the development in the most sustainable locations, which will tend to be the largest settlements within an authority area. The settlement hierarchy is:

  • Towns and cities
  • Larger villages with a broad range of services
  • Smaller villages that have some facilities but still place a degree of reliance on higher-order settlements
  • Hamlets and open countryside where the presumption generally is against development happening unless there are specific circumstances, such as for essential agriculture

Start with a site appraisal

A planning consultant can carry out a site appraisal before you get to the application submission stage. This looks at a number of areas that might be a barrier to getting planning approval:

  • What the local policy position is
  • What the chances of adhering to those policies is
  • Site constraints, such as flood zones, ecological designations, conservation areas, nearby heritage assets, etc

This would be followed by a number of surveys and reports

Providing that the planning consultant thinks they can demonstrate that the project complies with the local plan, a number of surveys need to be carried out to support the planning application. These will depend on the scale of the development but it is likely that some will be requested.

An ecological report will typically be required to identify whether there are any protected species on the site and sometimes these can only be carried out at a specific time of year. If you miss a survey calendar window, you may need to wait until the following year before trying again.

Additionally, a transport statement will look at visibility splays and traffic generation from your scheme. Depending on where your site is, there could also be heritage reports, ground contamination reports and archaeological investigations.

Local validation requirements will tell you what you need to submit

Local validation requirements supplement the national validation list, with what the local authority considers as appropriate for their area. It tells you what information you need to provide with your application when you submit it. Once you have submitted all the required information on the Planning Portal, and paid your fee, you wait for the council to validate it.

There are two routes to a planning decision

If there haven't been objections to the scheme, or if they've been addressed and the case officer is satisfied, then there are two routes to planning approval that might be taken. The first is their delegated decision, which tends to be on smaller, non-contentious schemes. This is where the officer has been given the power to grant or refuse planning consent.

The other route is where it is put forward to a committee. This might be because it has been called in by a local councillor, or because it is more contentious with a number of objections.

You have six months to appeal a decision

If the case officer or committee refuse the application, you have six months in which to appeal. There are three routes for this.

The first is called written representations, which is the easiest and cheapest. In your statement you would set out your case and submit it to the planning inspectorate. The council does the same. The planning inspectorate reviews both statements and makes a decision as to whether the appeal should be allowed or dismissed.

The second route is a hearing. Both sides set out their case as above, but then attend a hearing together in person. The planning inspectorate will listen to both parties before making their decision.

And thirdly, it can go to a public inquiry. This is the most expensive and time-consuming and is run very much like a trial. There are barristers and witnesses, and the inspector will sit as judge. They make their decision based on the written evidence and what they've heard in the cross-examinations.

Choose a planning consultant based on their relevant experience

If you're looking for a planning consultant to work on your case with you, it is sensible to choose one with relevant experience of the appeals process that you are using. They should be a member of the Royal Town Planning Institute (MRTPI) and have a good track record locally. Don't be afraid to ask for examples of cases they've won, so that you know you're going with someone who is familiar with local policy and has relationships with councillors and officers in the area.

Councils have a statutory duty to make self build land available

Putting your name on the Right to Build register means that the council has a legal duty under the Self-build and Custom Housebuilding Act to issue the same number of permissions as there are names on the register.

Andy has been involved in appeals where they have been able to argue that because the council have failed in their legal duty to issue enough consents for self and custom building, then land which might be outside of settlement limits should be permitted for development.

Andy has also found that although some councils claim to have met their obligations by granting the same number of single dwelling permissions as there are people on their register looking for a plot, further investigation shows that actually, the majority of them aren't for self or custom build at all. Some of these can be planning permissions for up to 9 dwellings, where they're clearly developer-led models with no ability for customisation.

Self Build and Custom Housebuilding Supply in Braintree

8 out of 10 people aren't aware of the Right to Build Register

In one appeal that Andy worked on, although the council had met its obligations, they were able to argue that secondary data sources showed the register was actually a massive underestimation of the numbers of people in the area that wanted to self-build. Many of these were people that weren't even aware of the self-build register. The inspector in that case allowed the appeal, even though the council had met its statutory duty.

Andy would encourage anyone to add their details to this register though, as this will increase the number of self build plots the council legally has to make available.

Outline planning permission is less risky

A full planning permission provides all the details about your scheme, including layouts, landscaping, scale and massing. If you were to then get planning consent, all you would have to do is discharge the conditions against it, such as material samples, working hours on site etc.

What a lot of people do is seek an outline consent with access only. This is an illustrative plan showing what you intend to put on the site. With outline approval you have to get subsequent reserved matters approvals for all the elements that you haven't included at that stage. Outline permission is cheaper, so is therefore considered less of a risk.

Andy stresses the importance of discharging any pre-commencement conditions, prior to starting work on site.

Self builders can apply for CIL exemption

CIL is the Community Infrastructure Levy that some councils have implemented. It is a per square metre charge on development and is intended to pay for strategic infrastructure. Self builders can apply for an exemption, but it is incredibly important to follow the process correctly, and within the timeframes, as failure to do so could lead to a bill running into thousands of pounds.

Find out more

Visit the website of Tetlow King Planning

Follow Tetlow King Planning on Twitter

Transcript

Download a transcript of the interview with Andy Moger

HPH329 : What does a structural engineer do? – with Beth Williams

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Beth Williams from Build Collective outlines the role of a structural engineer and explains what tasks might be undertaken on a house build.

Interview with Beth Williams

Beth had wanted to be an architect since she was a teenager, and graduated from university with a degree in architecture and structural engineering. However, at the time she graduated, the UK was in the grip of a recession and the only job opportunities she found were in structural engineering. Part of the reason she has since gone on to work in the low-energy space, is that she enjoys the close working relationship with the design team.

Beth is a Chartered Civil Engineer and Certified Passivhaus Designer. She is an associate at Build Collective; a bespoke engineering consultancy in Bristol.

Structural engineering is a sub-discipline of civil engineering

Civil engineering sits at the top of the hierarchy. It covers things like highways and drainage.

Structural engineering is a specialism within that, but can still be quite broad. Structures can mean a focus on things like bridges and masts, or it can be for buildings.

So if you're looking for a structural engineer for your project, you can either opt for a chartered civil engineer (with a specialism in structures), or a chartered structural engineer. Beth explains that there isn't really any difference in terms of insurances and liabilities. The qualifications to look for are: the MICE (Chartered Member of the Institute of Civil Engineers), and the MIStructE (Chartered Member of the Institute of Structural Engineers).

They work as designers, under the principal designer

If there is no architect on the project, such as for a small domestic knock-through, then the structural engineer may take on the required role of principal designer looking after health and safety.

For most other projects though, the architect is the principal designer. They coordinate the flows of information between the design team members, and produce a pre-construction pack. That is all of the information from all of the designers, and all the health and safety risks. This is then passed on to the principal contractor to take as their responsibility once the construction phase gets underway.

Small projects might not need a structural engineer

If you are redecorating or moving an internal wall that isn't structural then you probably don't need a structural engineer.

Part A of the Building Regulations gives a generic outline of the structural principles, which could be used by an architect to design a very limited building such as a garage or an extremely basic house.

It used to be the case that people doing architectural work would have cover in their professional indemnity insurance for designing small structures. However, since Grenfell and a number of basement collapses in London, a lot of them have lost those insurances so the work has come back to the structural engineers.

Domestic clients will usually pay a fixed fee

Larger projects tend to be costed up on a percentage basis, whereas domestic clients are likely to pay a fixed fee for the defined scope of works. Beth's advice is to always check what is on the scope of works, and the number of passes included.

A lot of engineers base their fee on responding to a set of drawings once. Build Collective however, do a two-stage pass. This involves some rough sizing and layouts as a preliminary design. The architect uses that to develop their details before returning to the structural engineer for their detailed design. Having that extra pass allows for tweaks to be made based on new knowledge that might be acquired during the process, such as ground conditions for foundations.

Many factors impact on the structural system

Corner windows, fancy overhanging roofs, and flat roofs are just a few elements that will impact the structural system. This all feeds into the “Have I got enough wall?” question, which is for the structural engineer to answer. Things like large glazing and an open plan design will all obviously limit the amount of wall that they have. So it's about how much wall there is to make the structure stand up, and evenly distributing it throughout the building. Large stair openings and double-height voids mean there is less floor area to be able to distribute the loads.

Where there aren't walls, it might mean putting in portal frames or goalpost frames to give stability.

It's not just the vertical loads that need to be considered either. They also need to factor in whether the walls can withstand the horizontal load when wind is blowing on them.

Local structural engineers may have better knowledge of ground conditions

One advantage of hiring a local structural engineer is that they will be familiar with the area and its challenges.

For example Beth says that there are many cheap building plots in Bath because the ground conditions are often horrendous. It has a lot of historic landslip material that is volatile to work on. And Bristol has lots of coal mining areas and slope stability issues that will prove challenging.

Beth suggests a good use of money would be to pay a structural engineer for a few hours to look at geographical maps for your site and provide advice.

She would also recommend having a proper geotechnical survey for a new build, which costs around £3,500-£5,000. This involves a specialist geotechnical engineer doing bore holes or trial pits. They will log the findings and send samples away for lab testing, and report on the different structural and chemical properties of the ground.

If you can get a good ground investigation early on, you mitigate a lot of potential risks that could occur later on.

Your foundations will depend on your ground conditions

There is a range of sizes of ground particles, from large rocks down to gravels, sands, and clays.

  • Rock – For rock at depth, you might be able to pile down onto it, and lock onto the top surfaces
  • Gravel – Can be very flexible and have good bearing capacity
  • Sand – These can be good because they don't have the same volume change potential you get in clays
  • Clay – Clay heave can be an issue. The clay will swell and shrink over the seasons as it takes on more or less water. To get around that, you dig deeper to where the clay isn't affected by the heave. That may then be too deep to dig safely, so would need piling

Concrete may be something that you're keen to avoid but it does have its place.

Beth uses a lot of insulated raft slabs on low energy projects. It's a good solution for timber frame projects because you need some weight in the building to hold it down. If you are going to use concrete the important thing is to use it efficiently.

Another foundation option could be screw piles. They have some tension capacity in order to do the uplift for a timber frame. However, they're not going to be possible in every scenario, and Beth warns against clients fixating on them before knowing whether their ground conditions will be suitable.

(AECB members can access a webinar recording of Beth discussing alternatives to concrete foundations.)

The design starts with the roof

Beth uses a top-down approach, starting with the roof design. This is followed by any suspended floors, then the walls and lintels in the walls.

Even before she does these vertical load takedowns, she will look at overall stability. This incorporates the wind and snow loads.

A surprising level of information is needed to do the structural design

There are lots of things that feed into the structural design that may not be immediately obvious.

Staircases are a good example. Where there's a stair opening going up through the floors there needs to be a stair trimmer. There may also be a balustrade to prevent falls. What that balustrade is made out of will impact the structure. Glass obviously has more significant limitations on the deflection it can take before it cracks, than a lot of other materials. It has different fixing requirements too. Another consideration is how the balustrades for the stair itself join onto the rest of the balustrade.

When clients arrive with a specific product that they want to use, Beth sources all the data from the supplier in order to do the design. She has developed her foreign language skills because often the technical information isn't supplied in English!

Don't be afraid to involve an engineer early on!

This is especially the case if there is a specific product or system that you want to use. Get advice early to see how that might impact what the structure looks like, where the windows might go, and how many walls you might need inside. Beth would then do preliminary rough structural layout markups, ahead of planning, to show where the beams and frames could go. The architect can feed this back into their designs.

Find out more

Visit the website of Build Collective

Follow Beth Williams on Twitter

Transcript

Download a transcript of the interview with Beth Williams

Calling future engineers

Water expert Cath Hassell has featured on the podcast several times before (discussing topics such as saving water, rainwater harvesting and dealing with sewage). However she is also the creator of the Frankie the Flamingo series of books for children. So if you have a budding engineer on your hands perhaps The Mysterious Case of the Elephant that Forgot is a good place to start.

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HPH328 : Insulating internally with a thin layer of wood fibre board – with Martin Twamley from Steico

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Martin Twamley from Steico explains how to use breathable internal insulation, while avoiding the risks of condensation and mould.

Interview with Martin Twamley

Martin Twamley is Technical Director of Steico UK. Steico have been producing timber-based materials, predominantly structural timber and insulation materials, since the 1960s and selling them across Europe. Using only pine and spruce they make a number of different products, and will always provide guidance as to what the correct product would be for the required application.

“Once people start using timber and understanding it, it's a sort of material that you fall in love with, and you then change your building process.”

The products have low embodied energy

Structural products like I-joists were first used in the USA and the motivation was that it was the most sensible use of the raw material. However, as a natural material and one that goes through little processing it also has a low embodied energy, and will even lock up carbon.

Laminating the veneers strengthens the product

The I-joists are created from Laminated Veneer Lumber. They are made by peeling a tree, creating 3mm veneers, and then bonding them back together. This means that individual weaknesses are removed and spread across the whole product. The strength-to-weight ratio on engineered timber is then much greater than it is for solid section timber as you're getting a much stronger product for less raw material.

There is very little manufacturing waste

Martin explains that the good thing about producing both structural and insulation products is that there is very little waste. For the structural timber they use the de-barking and peeling process. For the insulation materials they use chipping and milling. Therefore, what they can't use for the structural timber they can use for the insulation. What they can't use for the insulation they can use for producing their own pallets. And if they can't use it for pallets they have a biomass power station where they can use it for electricity generation.

UK housing stock has a need for internal insulation

The UK housing stock is some of the oldest in Europe and is in desperate need of retrofitting. With a reluctance to insulate externally and change the appearance of this historic solid wall housing, internal insulation may be a better solution.

The traditional way of doing this is with systems that try to block the moisture, rather than being able to control it. When you try to block moisture there can be an issue with getting it trapped inside the building instead. This potentially adds risk to the fabric of the building, because of mould and condensation problems.

The Steico wood fibre internal insulation system allows water vapour in, controls it, holds it, and then lets it out again.

Standard insulation installations are vapour closed

These typically are the foil-backed polyurethane type materials that are either on a frame system or dot and dabbed onto brickwork. In theory they don't let any moisture in, which is a good thing for the fabric. This can however lead to high moisture levels internally, so you might need to consider an MVHR for example. Mould will happen when warm air gets behind the plaster board and hits the cold wall surface. It might not even be until years later that the mould shows itself on the internal surface.

“When people think about air quality, they generally think about external air, but we spend 90% of our time indoors. It's the internal air that we're breathing. So that's what's impacting our health.”

These are the kinds of systems that tradespeople and DIYers are most likely to use, because they're readily available. Also, homeowners are primarily just thinking about thermal performance in the winter. But actually, when you consider a holistic approach that takes into account all the possible issues, the material choice is incredibly important.

Internal insulation doesn't have to significantly impact on the room size

Martin talks about applying a thin layer, typically an optimum amount of 40-60mm. Even in relatively small rooms that's an amount that won't really be noticed.

What works for one building, won't work for every building

What works for one elevation of a building might not even work for a different elevation of the same building, because of different weathering exposure. This is why it is so important to have an assessment done, particularly if you're looking for a really low U-value. Martin explains that generally speaking a 40mm or 60mm board on standard brick will work in the majority of situations.

Take the wall system back to bare brickwork if possible

The wall system should be as breathable as possible. That means that you don't want anything on the internal side that hinders water vapour movement, such as impermeable layers, cement-based plasters and renders, and paint layers.

The external face is also important to consider (such as renders and re-pointing), because this is where the majority of the water is coming from.

With this natural, breathable approach, there is a full bonding layer (typically a lime based product) between the insulation and the wall. This is in contrast to a traditional approach that would have a cavity. The fact that there is no cavity means that there is no collection of liquid water, which is what leads to mould and condensation issues. Instead, any moisture is either passed onto the brickwork and out the front, or it can go back to the inside.

Pay particular attention to the critical areas

Window reveals are particularly important. If you have a warm wall surface, then the window reveal will be the coldest area. If you don't insulate into that reveal then that is where all your condensation will form. Martin suggests that with a 40mm or 60mm on the wall, a 20mm board on the reveal will be fine.

Another critical area that could be overlooked if somebody is insulating ground and first floor, is the void where the floor joists connect into the wall. These can be cold spots where condensation will be much more of an issue than it was before. To prevent this, you can tape around the junction of the joists to the existing wall. This stops the route for convected airflow into the wall.

Where you have internal walls connecting with external walls can also be problem areas. If you're insulating the external wall, then the corner of that internal junction can be quite cold. Steico make a wedge-type product of thinner insulation that can go into the corner to stop the condensation risk.

There are useful resources available

Martin makes reference to The Guide for Sustainable Renovation, by The Pebble Trust, as being a valuable resource for anyone taking on a retrofit project. It gives advice with a holistic approach that considers all of the moisture risks involved.

The carbon storage element of materials is often overlooked

A frustration for Martin is that in the UK he thinks we tend to be quite product agnostic. It is very much that if you achieve a certain performance level then it doesn't matter what you use to to get there. He compares this with Bavaria, Germany, that has a new system brought in by local government. They are offering a 500 Euro grant for every cubic metre of biogenic carbon locked up within the fabric of the building. In the UK we have U-value targets, but nothing that looks at the amount of carbon stored within the fabric, or the type of material that is used.

Find out more

Visit the website of Steico

Follow Steico UK on Twitter

See Steico wood fibre insulation being used on Buckinghamshire Passivhaus (a PH15 project). Join The Hub to access our in-depth video case study.

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HPH327 : Upskilling in DIY during a home retrofit – with Es Tresidder

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As someone with no previous interest or skills in DIY, Passivhaus Consultant Es Tresidder explains why he went about changing that for his own deep retrofit project.

Interview with Es Tresidder

After getting a degree in ecology Es's journey to low-energy buildings incorporated time working in an earthship, and teaching children in schools about recycling. There then followed an MSc at CAT (Centre for Alternative Technology), and a PhD on optimisation of low energy building design at De Montfort University.

Initially sceptical about Passivhaus, his interest grew upon interacting with the ‘Passivhaus community' on Twitter. He then completed the Passivhaus Designer course, which he credits with teaching him more about building physics in two weeks than he learnt about in the entire duration of his MSc and PhD.

Es Tresidder now has his own consultancy Highland Passive and is in the final stages of retrofitting his home in Fort William, Scotland.

We caught up with him in the early stages of his EnerPHit project.

A good location can lead to a more sustainable lifestyle

Es and his family moved to the area so they could pursue their love of outdoor activities – climbing in particular – and they bought this 1970s timber frame house as a temporary measure until they could find a property to retrofit or a plot on which to build from scratch. It was however in a perfect location for them: walking distance to both primary and secondary schools, a 5-minute walk to the train station, safe cycling routes into town, and facing out to Ben Nevis.

If you want to retrofit, seek a property that needs work doing anyway

Normally if you're planning to take on a retrofit project, you'd look for a cheaper property with obvious signs of dilapidation. However, this house seemed on the face of it to be in a fairly good condition, which made it difficult to justify any extensive works. But once they started scratching away at the surface they discovered some bigger issues with damp and mould. They had also outgrown the house as it was and needed more space. So the decision was made to stay put, extend upwards and retrofit the whole house to EnerPHit standard.

Part of the reason for Es getting hands on was that he was interested in upskilling as a professional. He wanted to learn more about the practical side of tackling a retrofit so that he could help other people who were going to do it.

Never be afraid to get input from people with more experience

Beyond wiring a plug, unblocking a sink and changing a light bulb, Es had very little inclination or ability when it came to DIY.

In order to learn and upskill, he sought out people who knew more than he did and asked for guidance. His father, a retired carpenter, and a neighbour who was an experienced DIYer were regulars to call upon. Beyond that, YouTube tutorials were extremely helpful. While Es lacked practical skills and experience, he did have plenty of theoretical knowledge and a logical brain for working out sequencing and consequences of doing something.

Jobs he tackled himself included tearing things down, pulling floorboards up, putting in the insulation and doing the airtightness, and doing the MVHR installation. He did however leave the complicated work, such as building walls and taking off the roof, to the builders!

Make sure you have the right tool for the job

One of the things Es learnt early on was how important it was to have the right tools for the job. Investing in a good quality drill early on for example was essential.

Having spent a couple of weeks taking down half of a fake stone wall, initially with a lump chisel and hammer and then an impossibly heavy drill, he borrowed an SKS drill that finished the job off in an afternoon! From that point on he decided that if it was clear that there was a tool he needed, and he didn't have it or wasn't able to borrow it, then he would buy one. If he didn't need it at the end of the project then he would sell it.

Be prepared that some things may not go to plan

On one occasion Es mistakenly cut through a mains water pipe, rather than a radiator pipe!

A particularly difficult time was when they removed the roof, shortly before an incredibly wet May. Sadly, all the insulation Es had laid in the floors, together with the original floorboards that he had painstakingly taken up and re-laid, were destroyed and had to be replaced.

Working alongside a building team presents challenges

For the bigger structural changes Es engaged a local building contractor.

As Es was keen to do the airtightness and insulation work himself, he soon realised that he couldn't keep up with the builders.

For example, Es hadn't finished the insulation when the builders were ready to put up the plasterboard. The knock-on effect was jobs were done out of sequence and they were unable to do an interim air test.

The alternative would have been to spend time upskilling the builders in how to do the airtightness and insulation to Passivhaus standard.

“The difficulty with that, is that because this was a retrofit project, some of the airtightness was just unbelievably fiddly. And even a motivated contractor is not as motivated as the homeowner. I spent so long doing it that I find it hard to imagine that they would do it to anything like that level. But I might be wrong.”

Another option might have been to project manage everything himself. This would mean he could book and pay for services as and when they were required. It might have got round some of the scheduling issues, but would undoubtedly have taken longer.

This radical retrofit will lead to a healthier home

A suggestion from a builder friend was to just put foam backed plasterboard on the internal walls. But once Es started taking the walls apart it became clear how mouldy and damp they were. Using rigid insulation wouldn't really do anything about airtightness. It would also exacerbate the problem by making the damp areas colder and more damp.

Es often felt during the process that what he was doing was radical. Doing it any other way though would result in inferior performance and an unhealthy home.

Removing the roof was radical

Taking the roof off was an expensive move, and one that Es still isn't entirely sure was the right thing to do.

The upstairs rooms in the one and a half storey house had very low head height due to the eaves, which meant there was a lot of space being wasted. Another problem they had was because of where their windows were located, they also missed out on incredible views to the south. Instead of looking at Ben Nevis, they faced a neighbour's gable wall and a not particularly attractive tree.

While the alternative might have been to extend the house rather than raising the roof, Es felt the layout wouldn't have worked as well. They also could have knocked it down and rebuilt, but even with the VAT reimbursement, Es thinks it would have been a more expensive option.

Raising the roof has given them comfortable internal heights of 2-2.4m, and gained useable floor area that they didn't have before.

DIY is time-consuming and exhausting

Es has reached the point where he is so busy with work that, in order to get the project over the finish line, he has handed over some of the traditional DIY jobs to the builders. He has also had enough of doing them! This has included fitting the kitchen and bathrooms, and also the painting and laying flooring.

Generally speaking though, Es quite enjoyed getting hands-on with the project and acquiring new skills. He quite likes the idea of combining a bit of manual work, or the teaching of it, with his desk-based job in the future.

Top tips

  • Practice your new DIY skills somewhere where it's not too critical first, in case they need refinement.
  • If you're a keen DIYer and have knowledge of building physics then you could do a lot of the work yourself. Doing it without that theoretical knowledge though would be risky. Most people would need professional input to do a deep retrofit safely.
  • Don't panic! Keep calm and methodical – particularly when using the very expensive and very sticky airtightness tape.
  • Have a mantra reminding yourself how dangerous power tools can be.
  • Ask lots of people for help, and don't be afraid to use YouTube.
  • It would be worth doing a Passivhaus contractor course. It gives a good grounding of the theory, and also of some of the skills.

Find out more

Visit the website of Highland Passive

Visit the website of John Gilbert Architects

If you enjoyed this episode, you can also listen to some of our other interviews where industry professionals have taken on their own projects:

Transcript

Download a transcript of the interview with Es Tresidder

Get access to our in-depth video case study of the Kinver retrofit in The Hub

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

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HPH326 : Is it worth upskilling your knowledge of Passivhaus? – with Simon Bell

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Landscape Architect and Director of HLM Architects, Simon Bell, explains why he decided to upskill when it came to building his own house.

Interview with Simon Bell

HLM Architects are an award-winning practice with offices in England, Ireland, Scotland and Wales. As a Director, Simon was familiar with one of the projects designed from their Glasgow studio – Tigh na Croit – and knew that he wanted the same architect (Ross Barrett, who is also a friend of his) to design his own home.

Copyright HLM Architects

A Passivhaus doesn't need to be a simple box

Something that Ross proved with the L-shaped design of Tigh na Croit, is that a Passivhaus doesn't have to take on the simplest form. Yes, it can be at its most efficient as a straightforward box, but it is also possible to create buildings with architectural merit and beauty as well, it just might take a bit more effort to make the standard work.

The panoramic beauty of the site created Passivhaus challenges

Based in the centre of Northern Ireland, the stunning site is near a small village called Broughshane, close to Ballymena. They are up in the hills, with fantastic views to the east and west, and also panoramic views to the south. This meant they were always going to be faced with the challenge of balancing those out with solar gain, shading and window ratios, and is why they now have framed views of the landscape, rather than a huge expanse of panoramic glass.

The value of an architect is to bring a different vision

Having given Ross a brief around how they wanted to live in and use the house, it naturally lended itself to a long house type arrangement, which would have been far simpler from a Passivhaus perspective. With further design iterations they found that it wasn't quite going to work as they would like. Ross then presented a new design where the walls weren't parallel. It widened out as it got to the centre of the house, and then narrowed down at the ends. This was the design they decided to move forward with.

He wanted to be an informed client

Being the kind of person that likes to learn and understand how things work, and know the right questions to ask, when it came to the design and build of his own Passivhaus Simon was keen to develop his knowledge further. He took inspiration from Tomas O'Leary who had a similar background as a landscape architect, and has gone on to be internationally respected in Passivhaus circles with MosArt. This gave him the confidence to take on the Passivhaus Designer course himself, which he found to be intense and challenging, but also appealed to him with its methodical processes and attention to detail. Doing the course at the same time as working on the final stages of his own house design, meant that he was able to experiment in PHPP and take a lot more time to test things out for himself and understand the impacts that various changes made.

Quality control and education became part of his on-site role

In resisting his desire to be a hands-on self-builder (which he accepted fairly early on was going to be unrealistic if they wanted to be living in a house within 5 years!) Simon decided he wanted to take on the role of informed client, and work very closely with everyone on the team. Building through covid restrictions meant that he took on much more of the site role, as Ross wasn't able to be present as often as he would have liked. Simon was able to educate everyone that came to work on the site about Passivhaus, and how things that seemed insignificant would actually be important to the overall performance of the finished building.

Contractor attitude was more important than Passivhaus experience

When it came to selecting a main contractor, they found that there was a very limited number that had Passivhaus experience. Instead, they focused on their attitude, attention to detail on other builds, and evidence of where they had gone above and beyond building regs before.

They established a no-blame culture

Due to the pandemic restrictions, Simon ended up being more hands-on that he had originally intended. Living nearby meant that he could visit the site daily and be there to highlight issues or anything that needed particular care. This included setting up a no-blame culture, so that if anything was damaged they would all be informed, affording the opportunity to rectify it, rather than having it covered up and becoming a bigger problem later on. The contractor responded well to this and had come into the project wanting to learn and understand, and deliver it to the best of their ability.

Having a live project helped his understanding of the course

Even with the Passivhaus training course, Simon found that so many things you just have to learn about on the job. This was true for him particularly around the detailing, and finding the optimum solution for a heating system.

Trust in your consultants

Although it isn't necessary for clients to take the Passivhaus training course that Simon did, he does recommend that they do some reading to get a good understanding of the standard and how it works. The Passivhaus Trust has plenty of guidance available which is ideal for this and is pitched at different levels. Simon also believes that it's important to put your trust in your consultants too, and give them a degree of freedom to come up with the solution.

“Perhaps not get too involved in some aspects and more involved in focusing on how they're going to use the building and communicating that, but not necessarily getting too hung up on the actual technical solutions.”

The pandemic presented the biggest challenges

The main concern for them was getting the required level of airtightness, but the Covid pandemic brought about the greatest challenges. It impacted on materials, getting people to site, and causing delays and knock-on effects to the programme. It left the structure open for longer than they would have liked, which again had further implications.

Each build presents a learning opportunity

It's about good design, good practice and attention to detail. Simon's advice is to embrace upskilling and have the confidence to do it, whether you're a client, designer or contractor. And when a project has been delivered, go back and review what could have been done better, and what do you need to upskill in the future.

“It's a continuous process. We're always learning, we always need to learn, and that should be the mindset rather than trying to maintain a status quo where we always do things the way we've always done them. Let's challenge ourselves to always improve and do better.”

Find out more

Visit the website of HLM Architects

Follow HLM Architects on Twitter

Transcript

Download a transcript of the interview with Simon Bell

Video of HLM's Tigh na Croit

Please connect with us

Subscribe, rate and review us on Apple Podcasts

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HPH323 : Can I heat my home with an air source heat pump? – with Nathan Gambling

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Influential podcaster and heating systems expert, Nathan Gambling, explains why choosing the right installer is even more important than selecting the heat pump.

Interview with Nathan Gambling

Nathan comes from a family of heating engineers and he followed suit, completing his apprenticeship with the MOD in 1991. In 2006, he started teaching, including running City and Guilds courses in a prison, before also teaching in colleges.

With his unique background in heating systems and teaching, Nathan now runs the BetaTalk podcast; a highly respected source of content and information for engineers and those interested in the heat pump industry.

We teach people to be qualified, not competent

This is Nathan's assessment of the vocational education system in the UK. Having come out of that, but still wanting to facilitate learning, he got into podcasting where he was able to use his skills and connections to disseminate and amplify the voices of quality heating engineers. He is a firm believer that the starting point of any installation should be finding a competent engineer, but this isn't always straightforward for a homeowner or self-builder to identify.

Using a quality engineer should be a priority

Heating is a complicated business, yet anyone can set up a plumbing company without any qualifications at all (unless you're also dealing with gas, which would need the necessary certification). As an engineer, you don't need certification to install a heat pump, unless you're doing it under the Microgeneration Certification Scheme (MCS) which is where you're getting a government grant. Something to be mindful of, is that the MCS accreditation applies to the company, rather than an individual engineer, so it could even be possible that that person has left!

According to Nathan, the best engineers are those that engage in peer-to-peer learning and are constantly talking to each other about different techniques and best practice. These are the people that are on social media networks looking to learn from one another. It's not just about training but familiarisation with what's current in this quickly changing industry.

Nathan says that the range and quality of heat pump units on offer, whether supplied by the HVAC world, specialist heat pump manufacturers or traditional boiler companies, are actually pretty similar. It's having a good engineer that will be the difference and make the unit work very well.

Heat pump technology exists all around us already

Yet, much of this is technology that most of us wouldn't even normally associate with heat pumps, such as in vending and slushy machines. We also commonly confuse it with air-conditioning, but actual air-conditioning is quite rare. The systems in place in office buildings, cinemas, and retail centres, are much more likely to be something called comfort cooling, which heats us as well as provides cooling.

Heat can be extracted from even the coldest air temperatures

Essentially, a heat pump is something that moves energy from an evaporator to a condenser, and uses vapour compression to do that. It uses a refrigerant to compress it and extract more heat.

Unless you get down to -273.15 degrees celsius, which is the temperature at which atoms stop moving, you can extract heat energy. That energy is compressed, before being released out with a condenser.

In most domestic situations this would be an air to water system, where you're extracting the energy from the air and emitting it to the rooms via water running through radiators or underfloor heating.

Your power demand changes according to the outside temperature

All homes will leak, some more than others, and if there's a temperature difference between indoors and outdoors, then heat will move.

Systems tend to be designed to be able to cope with the average coldest day in the UK, which is around -3 degrees. Most homes need 8000 joules of heat per second to be able to maintain 21 degrees inside when it's -3 degrees outside. That's 8 kilowatts.

When it's 5 degrees outside it will need 5.5kW.

When it's 10 degrees outside it will only need 3.6kW.

Your power demand is therefore constantly changing depending on what the outside temperature is, because heat will move more quickly if there's a greater temperature difference between inside and outside.

Unfortunately, most gas boilers work on fixed temperatures, whereas they need to be modulating their temperature around the radiators according to what the outside temperature is.

The trick to getting a really efficient air source heat pump installation is to match the temperature that is flowing around your radiators as closely as you can to the temperature outside. So if it's -3 degrees outside and you can maintain 21 degrees inside with 40 degree water in your radiators, that's going to be more efficient than a system that is running 50 degree water around your radiators when it's -3.

“So if you design your system to be able to reduce that flow temperature in your emitters, for the colder temperatures, that's when you start to see these really good what they call COPs – coefficient of performance.”

The way to do that is with the size of the emitter. A good engineer will design a system that gives you the lowest flow temperatures possible for the coldest temperatures, which could mean both underfloor heating and radiators to increase the surface area.

There are few constraints on where to site a unit

Planning laws in England dictate that the external unit should be installed at least a metre from the boundary. Although they do make some noise, Nathan says they're generally no worse than standard oil boilers or gas flues. However, it's still wise to distance units from the neighbours' windows.

Some people aren't keen on the aesthetics of the heat pumps on their properties so try and cover and disguise them. However, as the pump needs to extract air from the outdoors, you don't want to be restricting its ability to do that.

It is critical to size a heat pump accurately

Too big and you're paying too much for a system that won't run efficiently. Too small and it won't meet the energy demands of the home.

Traditionally, heat loss calculations were used for sizing heating systems. These take data about the fabric of your home from SAP/RdSAP reports, so are more of a prediction about how it should perform, and assume that every square metre of your home is performing the same, which doesn't happen in the real world.

There are now new methods that can accurately measure the speed of heat going through your fabric. This heat transfer coefficient means you know what power you then need for any external temperature. Nathan says there are two different approaches that would achieve the same result.

Veritherm – this is an overnight test that uses heaters to increase the internal temperature of the property, while fans distribute the heat around evenly. Halfway through the test the heating is turned off. Temperature sensors inside and outside record measurements throughout the night. The algorithm knows how much power has been used to heat the property and monitors the speed at which that heat leaves through the building fabric to give you the heat transfer coefficient.

Heat Pump Survey – this uses several data loggers placed strategically around the home where they are left for three weeks. Their algorithm takes into account metred energy consumption along with weather data to give the heat transfer coefficient.

So tools like this are incredibly useful when designing a heat pump system.

Swapping a boiler for a heat pump may require infrastructure changes

That's not always the case and is something that will be individual to each property, but is often why a heat pump installation will cost more than just swapping out an old gas boiler for a new one. Switching to a heat pump may need new radiators and pipework.

There is currently help for homeowners wanting to purchase a heat pump, with up to £5,000 being offered under the Boiler Upgrade Scheme.

The boiler market has traditionally been incentivised

This has meant that installers may have been incentivised with loyalty schemes, cashback, holidays etc by the big four manufacturers to buy larger systems than many homeowners would actually need.

Nathan explains that a marketing tactic now being used with heat pumps, is advertising new refrigerants that can heat water to 60 degrees, which sounds great to customers. However, what's not so great is that this will actually put up their electricity bills, because the most efficient way of running a heat pump is to get the lowest temperatures as possible around your radiators.

There are key questions we can ask to help find a quality engineer

  • What flow temperature are you going to design my system for? – you want them to be saying the lower temperatures.
  • Do you weather compensate your heat pump systems? – they should be automatically adjusting the flow temperatures going around your emitters, according to what the outside temperature is.
  • What centres do you put your underfloor heating down? – you should really be wanting your underfloor down at 100mm centres as this increases the surface area and means you can run lower flow temperatures through it.

Nathan's final advice is to not get too caught up in researching the actual product and things like decibel levels and SCoP. SCoP is a theoretical prediction of the performance that each manufacturer will give in their literature. It doesn't necessarily mean that it will perform like that, because again that will come down to the installation. Instead, focus mostly on working out who is doing good things in this space and is going to provide you with a quality system that will accurately and efficiently meet your needs.

Read more about the Verithem method of measuring heat loss, and its uses, in our interview with Tom Fenton.

Find out more

Check out the BetaTalk podcast

Follow Nathan Gambling on Twitter

Transcript

Download a transcript of the interview with Nathan Gambling

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

Like our Facebook page

Follow us on Twitter

HPH321 : How do you make an existing home energy efficient? – with Paul Ciniglio

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With price hikes being caused by the volatile energy sector, Paul Ciniglio from the National Energy Foundation explains what we can be doing to our homes to reduce our energy consumption and be better protected from rising bills.

Interview with Paul Ciniglio

Paul Ciniglio is refurbishment lead at the National Energy Foundation, where he spends much of his time being involved with their SuperHomes network. With a background in building surveying, he has over 30 years experience of working in the built environment sector, with a particular focus on sustainable development.

Renewable energy plays a key part in the UK energy mix

On some days England is able to produce over half its electricity needs from offshore wind turbines. As renewables are intermittent, however, an energy mix is necessary to keep the lights on. At a domestic level we could be making even more of a contribution with solar PV panels and heat pumps.

Energy bill rebates would be better spent on improving energy efficiency

Paul says that the UK government's plans to issue rebates to households for their energy bills isn't sustainable in the long term. The only way to bring our bills down to reasonable levels is to use that same money to improve the energy efficiency of our homes and cut out the waste. In order for us to achieve net zero carbon we are going to need to aspire to Passivhaus type approaches and super-insulating homes.

NEF is an independent charity

A common problem for people wanting to undertake a home retrofit is knowing where to start and who to trust. As an independent voice, NEF is able to bring that level of trust and support to those embarking on a retrofit.

Start with a whole house retrofit plan

NEF can arrange a whole house retrofit plan and this is carried out in accordance with the British Standard BS40104. It entails a survey of your property by a retrofit coordinator, who will then produce an options appraisal as to everything you could do to improve the energy efficiency of your home. It will show the benefits, so the predicted running costs and reduction in household emissions, as well as the estimated cost savings for each retrofit measure.

There are also risks involved in taking on a retrofit project but these will be flagged up in the retrofit plan at the start, so they can be managed.

By looking at the whole house view, it is possible to make decisions on what can be done now and what can be done in the future.

Fabric performance should be the first consideration

When using a whole house holistic view there is an energy design hierarchy, and the place to start is with the fabric performance of the home.

  • Cut out the heat losses through the fabric of the building, so the doors, windows, insulation in the roof, walls and floors
  • If making the house very airtight, it's important to factor in the ventilation to prevent damp and poor indoor air quality
  • Look at efficient heating systems – it is likely that we will move towards electrification in the UK which really implies heat pumps
  • Then consider other renewables, such as solar pv to generate clean electricity

By using a phased plan such as this it means that work is carried out in a logical order, and also that you don't unwittingly do something that prevents you from adding another measure in your plan later on.

The risks need to be managed

This is to ensure that retrofit maintains a good name, is worth doing, and is not going to cause lots of problems.

With the retrofit plan, each home is assigned a risk pathway, A, B or C (A being the lowest risk, and C perhaps being a historic building).

A suitable ventilation strategy is absolutely key, as condensation and damp can lead to mould issues. When insulating it's important to consider moisture, so that it doesn't get trapped in the fabric of the building and cause bigger problems.

To get rid of condensation you need three things:

  • insulation
  • heating
  • ventilation

Without those you are likely to get black mould forming.

NEF run a best practice retrofit network

This paid membership is operated by SuperHomes, and gives you access to events and seminars around retrofit issues. You can also then be assigned a retrofit coordinator, who will be someone that is an accredited professional that has achieved a diploma through the Retrofit Academy. These typically are architects, surveyors, and energy managers who have all been through this training.

The SuperHomes initiative also has a rating scheme, which is a benchmark for retrofit achievement.

A lot of retrofit can be done with residents in situ

Sometimes retrofit can be done on a room-by-room basis if it's carefully managed, but it can be very disruptive. Generally it's only for the deepest, most challenging projects that residents might need to temporarily move out, although all projects can be carried out more efficiently and easily without the residents living there.

At House Planning Help, we have followed a deep retrofit in Oxford. Get access to our in-depth video case study in The Hub

Look out for TrustMark and MCS certification

Paul explains that there is a massive skills shortage to deliver the amount of retrofit that is needed. Traditional builders are already busy and the energy efficiency market needs to be made more appealing to them so they can upsell skills.

The government's TrustMark scheme shows that contractors have been vetted, with the idea being to put the public's faith in the contracting sector. And if you're having a heat pump or solar PV installed, then make sure your contractor is accredited to the Microgeneration Certification Scheme (MCS).

Paul is re-retrofitting his own SuperHome!

Paul lives in a 1989 mid-terrace cottage, which he retrofitted and became a SuperHome back in 2009. He upgraded the insulation, including putting it in cavity walls where builders were supposed to have put it when it was first built, but hadn't. He also upgraded the loft insulation, installed an air source heat pump, solar pv, solar thermal, and new windows.

“My comfort has gone up and I've got my own energy security protecting me to a certain extent with these price increases.”

At the time there were some things he wasn't able to do, so now he's taking on a further retrofit, including putting in ground floor insulation. He has also stripped out the solar hot water panels. They worked okay for the first seven years, then only intermittently until eventually being decommissioned. A preferred option now is solar pv that diverts the solar electric into an immersion cylinder to provide the hot water.

The reason Paul's solar thermal didn't work very well he says was because it was too efficient for the size of cylinder he had. By 10am it would be up to temperature and if water wasn't being drawn off or he was away on holiday, it would stagnate and get really hot, causing damage to the valves.

The Energy Performance Certificate isn't up to scratch

In the wake of the energy crisis, it seems natural that when people are looking for a new home they will be asking how much it costs to run, and this is something the EPC isn't very good at. NEF is doing some research working with a team of chartered valuation surveyors to carry out property valuations pre and post retrofit. It makes sense that a more energy-efficient home should command a higher price, and Paul says there is emerging evidence that this does seem to be the case.

Once a SuperHomes retrofit has been completed, they install monitoring equipment for 12 months to gather and evaluate data about household emissions to see how well the property is performing. It's on that basis that they certify the SuperHome and what level it has achieved. The metrics they use for this are the space heating demands (which are a proxy for the fabric performance and tell you how well insulated your home is), temperature (including checking for overheating in the summer and making sure it doesn't get too cold in the winter) and humidity and indoor air quality levels.

Know where you're going to “get the biggest bang for your buck”

Having a whole house retrofit plan will mean that you know what improvements are going to make the biggest difference and save you the most amount of money. It's important to note however that you don't always get a payback with every retrofit measure, just as you wouldn't with a new kitchen, car or conservatory.

Insulation is the most cost-effective way to retrofit, and is simple for lofts and cavity walls. It's much more of a challenge for the 7 million homes which have solid walls.

But where funds are limited, Paul explains there are government grants to help private homeowners insulate their homes. There was a local authority delivery grant program administered through regional energy hubs that can help households with incomes of less than £30,000. There is also a new Energy Company Obligation (ECO4) which is another source of funding. Sometimes there are local grants available too.

Find out more

Visit the SuperHomes website

Follow National Energy Foundation on Twitter

Check out the Tape Notes podcast

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HPH320 : Precision-cut timber frames – with Antoine Costantini from Kithurst Homes

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Antoine Costantini explains how Kithurst Homes has embraced modern cutting technology to increase efficiency and minimise waste.

Interview with Antoine Costantini

With a background in physics and trouble-shooting in the construction industry, Antoine has always loved working with timber. He explains that engineered timber is a great way of using the material responsibly and with less waste.

There are 4 main types of engineered timber that Kithurst Homes use

These are:

  • Laminated Veneer Lumber (LVL) – “Like a plywood on steroids”
  • KVH – Finger-jointed soft wood
  • Cross Laminated Timber (CLT) – A cross lamination of timber in opposing directions
  • Glulam – Soft wood glued together

Automating the process is faster and produces less waste

Previously they would use a large chop saw to cut frames by hand, which meant manually changing the direction each time a different angle was needed. This would get repetitive and there was the risk of human error so they looked for a way of automating the process.

The Hundegger machine they now use is a five axis saw which enables them to make cuts at any angle and inclination. It has also reduced the time it takes to cut, mark and pack a 200 square metre frame from two and a half weeks, down to three hours! On top of this there's now only 3% wastage.

The Hundegger software reads and cuts from various file types

One of Kithurst's customers is Passivhaus Homes with their PH15 method of construction. They send over their completed BVX file of the timber frame design, which gives the machine all the information it needs.

Get access to our in-depth video case study of Buckinghamshire Passivhaus, a PH15 build, in The Hub

Kithurst Homes also work from DWGs or can convert a hand drawing into a 3D image that the saw will then read.

The machine software creates a picking list

This will tell the operator the amount of I-joists, glulams and LVL that will be needed. These are then manually placed in order of size and fed into the machine.

The machine is clever enough to recognise the material that is being fed in, and will alert the user if the geometry of the material doesn't match with what it has been asked to cut.

Using I-joists is an efficient way of building

They use less timber than a traditional stick frame approach, and also reduce cold bridges because of their size and geometry. They arrive at the factory in 13 metre lengths, with Antoine estimating that an average frame would use around one kilometre of I-joists.

The combination of the web of the I-joist with incredible shear strength and the lamination of the flange gives the I joist its strength and load bearing capacity. The regularity of the timber makes it predictable, and that is a good thing in engineering. They know how it will react on strength, density, bending, modulus, and shear.

If it's not compostable or recyclable they won't use it

Once the timber has been cut, numbered and marked, it is packed together by wall. Steel bands are used to secure them, as these can then be recycled whereas the plastic alternatives can't. They are then stacked and transported to site by curtain sided trucks. Once on-site there is no need for a skip, as everything fits and there is no wastage. This complies with the company ethos of trying to preserve the environment as much as possible, and not using PU or polystyrene foams for example.

It just takes common sense and DIY skills to put it together!

Kithurst Homes will always provide training, whether that be on site or at their factory, in how to construct the frame. With everything being marked, it's a case of needing to be bound together, and Kithurst Homes provide all the fixings, the screws, the staples, the membranes, the plywood.

Antoine says that anyone with good DIY skills can put together their flat pack systems. Some of the parts can be heavy so may need extra pairs of hands, but generally because the I-joists use so much less timber they can be quite manageable.

Their full wall systems however require craning in and a team of carpenters to put together.

All their timber is PEFC certified

The timber comes from two or three manufacturers, with Steico in Germany being where they get their wood fibre insulation, LVL and I joists. It is fully certified to European regulations and Kithurst know their suppliers are using the timber properly, with everything on the tree being used and documented.

Find out more

Visit the website of Kithurst Homes

Transcript

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