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  • HPH365: Becoming a housing activist – with Cypren Edmunds

    HPH365: Becoming a housing activist – with Cypren Edmunds

    Cypren Edmunds, a housing activist and advocate for bio-based building materials, describes the challenges he has faced living in social housing in London, and the health benefits and energy efficiency that can be achieved through building with straw.

    Interview with Cypren Edmunds

    Cypren is the Chairperson of Strawbale Building UK and the President of the European Strawbuilding Association, and is working to increase the use of straw and other bio-based products within the construction industry.

    Cypren has first-hand experience of living in UK housing that is not fit for purpose and the affect this has on family life and the wider fabric of society. He believes we need much more education within the construction industry and society at large to enable us to build healthier and more energy-efficient homes.

    Activism begins with a burning desire to make a difference

    Cypren describes how living with his family in a property that had damp and condensation became distressing, and drove him to become a housing activist and ultimately to change his career. He started by re-igniting the Residents Association for his housing estate, but quickly realised that collectively they didn’t really have the knowledge of the built environment, planning and housing regulations to get to the core of the problems they were all facing. Cypren, a qualified carpenter, was working in fitness training at the time, but decided to change direction and see what he could do.

    Activism requires upskilling and plenty of time

    Cypren knocked on doors to find out just how bad the situation was for residents. In one of the worst cases, water was dripping from the light bulb above the resident’s head and as you walked through his flat, every single wall was dripping with condensation and mould. The resident had complained to both the Housing Association and Local Authority, but nothing had happened.

    A wall riddled with damp and mould

    The fabric of the buildings is concrete and steel (with fan heating) with no apparent strategy for dealing with ventilation, so moisture becomes trapped. The Housing Association didn’t have any solutions, apart from leaving windows open or putting in noisy dehumidifiers, neither of which worked well for residents.

    Keep communicating and stay engaged with all parties

    Rather than getting aggressive the Residents Association genuinely wanted to stay positive and work with the Housing Association and the Local Authority to identify solutions. As the Housing Association had already carried out surveys of the building, they too realised how bad the situation was and that it needed addressing. However they admitted they didn’t have the money for a full retrofit, so after much consultation tenants voted for regeneration.

    Cypren outlines the role of the Residents Association in explaining the wider picture to residents and wading through the multitude of facts and information provided by the authorities. Many people didn’t understand the bigger picture, only how things related to them, and this is a political problem that needs to be addressed.

    “We don’t have enough skilled professionals, at all levels, in the construction sector to undertake the kind of retrofit work necessary for these types of properties.”

    Council houses in North Kesteven

    Low carbon bio-based materials have many benefits

    Whilst straw was rejected as a material for the regeneration of Cypren’s housing estate it is being used widely across Europe in the construction of a variety of public and private buildings.

    As President for the European Straw Building Association and chair the Strawbale UK, Cypren is working to get the message across politically and digging into policy and regulations to increase use of bio-based materials in construction.

    A firestation in Colombey Les Belles, France

    Meliana day care centre in Valencia, Spain

    Countries like Lithuania and France are way ahead of the UK in recognising the value of straw and other bio-based materials. The French have entrenched this methodology into their regulations. For example policy RE 2020 is an environmental regulation that came into effect in 2022 with the goal of improving energy efficiency and reducing greenhouse gas emissions. Cypren points out that we just don’t have this in the UK, and whilst groups like ACAN are doing a great job of delivering that message we need much more.

    STBA and SPAB hold a joint conference

    We need more education around the use of straw

    Cypren is clear that in the UK we need a significant drive to enable people to understand the value of using straw and other bio-based materials within the construction industry and that this drive should come from Government. There is a lack of education within the construction industry itself and many myths around straw that make the public wary of its use.

    Get input from experienced natural builders

    As with any material or methodology it’s essential to understand how you work with bio-based materials and how it differs to other approaches so make sure you’re learning or engaging with experienced natural builders. The good news is that straw is not a difficult material with which to work, particularly if you’re already a plasterer or carpenter, etc. The skills necessary are just the same as you would need if you were going to build a timber framed house. And now with prefabricated straw panel systems it is even easier, with construction on site taking just a few weeks.

    Highly engineered straw panels at Old Holloway

    Cypren believes we need to be building more with straw panels and developing factories to produce them. This would be good for the economy and generate jobs. We’re told the construction sector is struggling, so let’s train young people to work with materials that are helping us to move forward in life. It’s up to the government to give the appropriate incentives to those large housing developers to incentivise them to build in that way. We should take inspiration from France. Cypren tells us of a conference last year, where the French were saying they’d just built over 10,000 homes with straw. He couldn’t say how many we have built in this country.

    Intelligent activism could help create better homes and communities

    Cypren feels that if we are not happy with the situation within our community, we need to work together to create change. For him it’s not about going on marches or rallies it’s about engaging with the authorities, commenting on consultations, and making sure your voice is heard. He believes we have a tendency in England to sit back and expect others to sort things out. Instead, he suggests we find like-minded individuals, share ideas, speak to experts to get the information needed and become active with our community.

    For us to have a healthier society, we need to be thinking of everyone. There is a knock-on effect for example for young people living in poor housing, who are ashamed to take friends home, with no youth centre to go to, and so they hang around outside and potentially become involved in anti-social behaviour. If homes are comfortable and inviting people will want to be there instead.

    Keep an open mind to bio-based materials

    Cypren’s overriding message is to keep an open mind to bio-based materials. He says there is massive potential to scale up and that it would enhance all of our lives.

    From all of the data and all of the reports Cypren has seen, people who live in straw buildings or own bio-based buildings tend to be happier and healthier.

    Querbeet Housing Project in Lüneburg, Germany

    Find out more

    Sustainable Traditional Buildings Alliance

    European Straw Building Association

    Straw Bale Building UK

    The Society for the Protection of Ancient Buildings

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

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

    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

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  • HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    Ben Adam-Smith shares his own experience of living with a mechanical ventilation system. While he’s clocked up a few error messages on the unit and had more problems than most, he explains why he wouldn’t want to go back to natural ventilation.

    MVHR is a key component of low energy buildings

    In case you’re wondering what MVHR is, well, it stands for mechanical ventilation with heat recovery.

    As buildings become increasingly airtight, a good ventilation strategy becomes all the more important.

    But there’s a clever twist: by controlling the ventilation you can recover the heat when you want to (transferring it to the fresh incoming air).

    Hopefully that’s clear, but if not we made a documentary about airtightness a few years ago!

    Since this documentary was made I have moved into my own Passivhaus.

    Error messages are warnings

    I am a big fan of MVHR (pun intended) but that doesn’t mean I’ve had the best relationship with my MVHR unit.

    I’ve had 3 sets of errors on the machine in the two and a half years I’ve had it.

    The first errors might have been in connection with a silencer that was retrofitted a year after we moved in. I suspect the machine was clever enough to notice something had changed. The errors resolved themselves!

    About a year later, an external pressure message cropped up a number of times.

    The fan status readings on fan speed two which should be 200m3/hour are:

    Supply fan – Speed 550rpm, Duty 15%, Flow 93% ( a noticeable drop in air flow)

    Extract fan – Speed 1900rpm, Duty 48%, Flow 0% ( air flow can be detected from the extract air valves when a piece of tissue is held up to them )

    Error messages can be reset

    Interestingly, these errors can be reset while you’re investigating the cause… but they usually return, even if that is weeks later.

    Apparently there was a known issue with the humidity sensors on my particular unit. This was changed and again it was business as usual.

    However, at the beginning of the year a new error cropped up!

    Nobody likes seeing a flashing red light on their control panel because it means something needs fixing (or at least investigating).

    At this particular point we’d been getting night-time temperatures between -2C and -5C, which is the coldest we’ve experienced since we built the house.

    When the temperature warmed up a little I was able to reset the error and everything would return to normal (or until I could get the machine looked at).

    However, that trick didn’t work the next day.

    The machine completely died and I couldn’t get it to come back on. There was also a light burning smell inside the house.

    I had a couple of concerns at this point:

    • How long will it be until I get my machine back up and running?
    • Might I get a build up of mould somewhere in my system if I can’t get it fixed soon?

    Fortunately when it comes to mould, I was quickly reassured by my friends in the know.

    So, now whilst the problem was investigated we had to survive without the machine.

    With no MVHR running, we resorted to opening windows!

    Not that I’d choose to do this experiment but it was quite interesting to see the impact of living in a Passivhaus with no MVHR running.

    Firstly, the house remained nice and warm inside (the insulation has gone nowhere). Perhaps the heat wasn’t as even; I don’t know. But it wasn’t a terrible experience.

    It was however, a right faff to have to open the windows every few hours… not to mention the heat we must have wasted… and the family complaining at having the windows open when it was freezing outside.

    Perhaps the most interesting impact of no MVHR was the instant lingering smells. My wife noticed that each room had its own smell! And it was definitely harder to shift cooking smells.

    Eliminate the simple stuff first

    On a chat with Steve Clarke at Green Building Store trying to diagnose the problem, we double-checked that power was getting to the unit.

    Embarrassingly I hadn’t even checked the trip switches. In fact, we’d managed to cover them up with a shelving unit so that I’d forgotten they were even there!

    With the machine humming to life, I had a massive sense of relief. Whatever the issue is it’s not quite so urgent when the system is at least on.

    The preheater needs to be replaced

    It didn’t take long to diagnose the problem (the burning smell was the preheater working for the last time) but British wisdom of leaving the EU meant the new preheater took several weeks to get here.

    The warranty period on MVHR units is typically 2 years

    For an essential item for Passivhaus dwellers, this does seem short.

    The clock also starts ticking when you buy it.

    Mike Coe, the self-builder behind Portree Passivhaus, bought his unit in advance and subsequent delays have meant it will already be out of warranty.

    My own unit was out of warranty, too, but the manufacturers kindly supplied the new part free of charge.

    I installed my new preheater!

    With Steve Clarke from Green Building Store on the phone, I was expertly talked through what I needed to do.

    Buying through a company with good customer service was a great move.

    We’ll have to wait for more cold weather to check it has done the job.

    ‘MVHR needs to be as reliable as a fridge’

    I was interested to see whether other people had had trouble with their units and so I posted up on social media.

    I don’t believe many Passivhaus owners have actually had problems, which is a good sign. As Fionn Stevenson says ‘good quality assurance is essential’.

    Andy Simmonds, Chief Executive of the AECB, stressed it is such an important piece of kit. The emphasis needs to be on durability, reliability and repairability.

    He likened an MVHR unit to a fridge.

    Having bought a new fridge when I built the house I have noticed that even fridges have got more complicated.

    In the past it’s normally the plastic door seal that has failed before anything else, but on the new more complex models water dispensers get jammed on and ice trays freezer up, and don’t get me started on the plastic water filters!

    I would not go back to ‘natural ventilation’

    Despite the inconvenience of investigating different error messages, my MVHR unit has never stopped! Yes, I was a bit slow to check the trip switches, but if there’s a next time I won’t make the same mistake.

    If the machine is still operating, you haven’t got a big problem

    If your machine is not working at all – i.e no ventilation whatsoever – then I would really be looking for a speedy repair.

    As with anything in life that breaks, it normally takes a little while to fix it.

    So it would be lovely to have the option of a 24-hour repair service in the years to come.

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  • HPH297 : Why retrofit a Victorian terraced home to Passivhaus standard? – with Guy Hargreaves

    HPH297 : Why retrofit a Victorian terraced home to Passivhaus standard? – with Guy Hargreaves

    Guy Hargreaves explains why he wanted to renovate his Victorian terraced house to Passivhaus standard and how this is going to be achieved.

    Interview with Guy Hargreaves

    Guy Hargreaves is originally from New Zealand, but he met his wife Susan in Australia.

    While living in Sydney they bought and renovated a Federation style house in which to bring up the family. When the children were in their early teens, they relocated to Hong Kong with Guy’s work. And after 11 years there, they followed their children to the UK (where they had gone to university and settled).

    As Susan was doing a masters in Oxford that became the obvious place to set up home and in October 2019 they bought a Victorian terraced house. Initially they planned to live in the house for a couple of years to get a feel for it, but it quickly became clear that it would need a lot of work to make it liveable. So they started planning a renovation straight away.

    The building is set over four floors and includes a self-contained basement flat and converted loft.

    A visit to the National Self Build and Renovation Centre was a great starting point

    While Guy and Susan were able to lean on the experience of their previous renovation, they were keen to upgrade this property to be a high performance home.

    After seeing several Passivhaus homes on Grand Designs over the years they had become interested in the concept, but it was a visit the National Self Build and Renovation Centre (NSBRC) that acted as a catalyst for targeting Passivhaus standard. This is also where they met Alan Budden from Eco Design Consultants, who they would later hire as the project’s architects.

    Having studied mechanical engineering at university, Guy felt that discovering the Passivhaus standard was a bit of a homecoming.

    “The Passivhaus concept itself really grabbed my imagination, to be honest, and I was hooked.”

    Working remotely caused minimal delays

    Having gained planning consent (in January 2020) with help from a more ‘traditional’ architect, Guy realised that they needed a specialist for the Passivhaus refurbishment. So they hired Eco Design Consultants to take over the project.

    This coincided with the beginning of the global pandemic and consequently the project was progressed during lockdown.

    Despite this challenge Guy believes it made little impact on the project’s timeline.

    Preserving the ‘period’ feel is important

    As part of a three terrace development, Guy was keen to keep the heritage feel of the property at the front.

    “We don’t want to replace Victorian sash windows with anything that doesn’t look like the Victorian sash windows that are there now.”

    The rear of the building is less important because most houses have been extended over the years and they all look different.

    Sketch perspective of the how the rear will look after the refurb

    Passion is a driver for targeting the Passivhaus

    This renovation will be to Passivhaus standard rather than the slightly less stringent retrofit standard, EnerPHit.

    Guy is hoping that it’s not going to be a much heavier lift.

    “It’s the passion I have for the Passivhaus certification more than anything. I’m not sure that the internal feel of the property will be much different if it was renovated to EnerPHit certification.”

    First floor plan

    There are different insulation strategies for different elements of the building

    The historic brick facade will remain at the front and back, but it will be insulated internally.

    At the back of the house the ground floor will be dug out and a new concrete slab will be set on top of insulation.

    In the basement, the top of the floor will be taken off and a Diathonite screed will be laid down.

    Interestingly, the party walls will not be insulated at all.

    The windows need to be replaced

    All windows and doors need to be high performance, so these will be upgraded to triple-glazed products.

    The whole building will also be ‘wrapped’ internally for airtightness layer. This layer will come in the form of various materials.

    ‘Futureproofing’ the building justifies the cost

    Guy admits that there are significant costs attached to a renovation of this quality and performance.

    However, he bought at a price that reflected that the property needed a full renovation. Also, part of retrofitting this home is to futureproof it against the impact of climate change and rising energy costs.

    On top of that, there is no doubt that the comfort levels of the house will be vastly improved and this too, along with Passivhaus certification, may be reflected in what the property will be worth in future.

    Their builder was keen to develop skills

    Finding a builder with Passivhaus experience was really hard.

    So Guy has hired a firm who have considerable renovation experience but also demonstrated a desire to tackle a project of this nature.

    PHPP adds another dimension to the project

    In addition to balancing cost, quality and speed, Guy says you must always think about performance.

    “You’re always trying to balance what you want to do stylistically with what the PHPP model will let you do! So that becomes a fourth dimension. Everything you do has an impact in terms of, will the building perform the way you want it to perform?”

    Find out more

    Visit the website of Eco Design Consultants

    Follow Eco Design Consultants on Bluesky

    We are filming every step of this build for our Hub members. Find out more.

    Transcript

    Download a transcript of this episode.

    National Self Build and Renovation Centre

    Guy and Susan started their renovation journey at the UK’s only permanent exhibition centre for self-builders and renovators – the National Self Build & Renovation Centre.

    Located just outside Swindon it’s a one-stop shop for learning about the build process and sourcing potential suppliers.

    They also offer a range of courses and workshops. Find out more by visiting their website.

    A tour of Carrstone Passivhaus Plus project

    Eco Design Consultants were also behind Carrstone Passivhaus.

    Check out this video tour for more information about the house and its design.

    Please connect with us

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  • HPH289 : Retrofitting period properties – with Roger Hunt

    HPH289 : Retrofitting period properties – with Roger Hunt

    Author Roger Hunt explains why period properties need treating differently when it comes to achieving successful retrofit projects.

    Interview with Roger Hunt

    Roger Hunt co-authored Old House Handbook back in 2008, about repairing old buildings, at a time when retrofit was barely on the agenda. Not long after, people started to recognise the importance of retrofit and sustainability which led to their companion book, Old House Eco Handbook. It has since been updated with a second edition, incorporating new thinking on how to make buildings energy efficient, and the surge of new materials available that can make it happen.

    Not enough progress is being made

    Roger recalls attending a conference not long after Old House Handbook was published where, to meet targets, it was claimed that a city the size of Coventry would need to be retrofit every week.

    “We’re nowhere near that. We haven’t scraped the surface. We are so far behind in terms of retrofitting old buildings that there is absolutely no way we’re going to meet the targets we need to meet as far as I can see. And we can’t build new homes to solve the problem because we can’t build them quick enough; there isn’t the land to build them on. And the environmental impact of knocking all the old ones down to build new ones isn’t sustainable either.”

    Typical UK housing stock – Copyright Roger Hunt
    Copyright Roger Hunt
    Copyright Roger Hunt

    Pre and post-1919 buildings need treating differently

    Roger defines old buildings as being anything from medieval through to Victorian and Edwardian terraced houses. They were houses typically made from breathable materials, such as lime mortars, renders and plasters.

    Getting the retrofit techniques wrong in a breathable type of construction can store up problems for the future in terms of damp and condensation.

    It is important to make the distinction between those breathable buildings, and ones from around 1919 onwards, when construction methods changed to concrete and cement being used with a focus on keeping water out. Those buildings need to be treated differently, as getting the retrofit techniques wrong can store up problems for the future.

    Start with a plan for the whole building

    It might be that you won’t intend to do a full retrofit straight away, just elements of it to begin with and the rest spread over several years, but it’s important to think of your long term plan of everything that will need doing.

    For example, starting by draft-proofing all the windows and floors will cut down air movement within the house and cause a build up of condensation and poor air quality, if controlled ventilation isn’t considered. That might be achieved by controlled opening of windows, or a mechanical ventilation system.

    Using controlled ventilation – Copyright Roger Hunt
    Opening windows as a form of controlled ventilation – Copyright Roger Hunt

    Roger says that some sort of mechanical ventilation is almost inevitable, particularly for kitchens and bathrooms, but heat recovery systems don’t necessarily work well in old buildings.

    Reducing drafts is as important to comfort level as insulation

    Drafts actually make you feel colder than the building really is, so introducing secondary glazing or draft proofing around windows can make a big difference to comfort levels.

    Other uncontrolled ventilation can come from gaps in floorboards. If they can be plugged and a window opened when required then you can have controlled ventilation.

    Copyright Roger Hunt

    Buildings must be properly maintained

    Roger stresses that maintenance is particularly important for old buildings. Blocked gutters for example can lead to thermally inefficient wet walls, and a slipped roof tile can lead to leaks, rotten timbers and water coming through ceilings. The repair job is going to be costly and a lot less sustainable than just maintaining the building properly.

    Copyright Roger Hunt

    Reduce energy use within the house

    Before even thinking about how to heat or light the home, you should be thinking about a fabric first approach of how to insulate, cut drafts, and increase daylight. From there you could incorporate solar arrays or air and ground source heat pumps. The heat pumps won’t work so well if it is a leaky building, so these all need to be considered as part of the bigger project.

    “You have to think of the best solution for heating combined with all the other things you’re doing. So, an air source heat pump is not necessarily going to be the solution until you have tackled some of the other issues with the building.”

    Simple things that can be achieved quickly with an instant impact include changing high energy bulbs to LEDs and putting in loft insulation.

    Copyright Roger Hunt
    Copyright Thermafleece

    EnerPHit projects can be incredibly successful

    With fairly disastrous consequences to getting it wrong, one way to have a successful outcome is to work towards the EnerPHit standard. This will probably mean employing an architect or other specialist with experience of what they’re doing. It might not be cheap or easy but will deliver on energy efficiency and comfort.

    There is a delicate balance between sustainability and retaining character

    A risk of coming in and doing a complete retrofit of an old building is that it can lose some of the character which makes us love them in the first place.

    “I’m passionate about trying to make buildings sustainable and cut our carbon but at the same time we’ve got to have places that are accessible, enjoyable and important to people.”

    Roger says it’s a complex subject as we have to embrace the value of the building in terms of beauty, aesthetics and our love for them, along with the monetary value.

    Take time to understand your building

    Roger’s tips for tackling a renovation of an old building are:

    • Don’t rush in. Live in an old building for a year, through each of the seasons, to really understand the damp and the light. That will also help with your interior decoration.
    • Don’t try and use modern materials that are incompatible with an old building. Particularly don’t use an insulating material that is going to stop your building from breathing.
    • Do your research, talk to people, go to events, look at products, don’t trust everything you read on the internet. Cross-reference everything to check that you have the right solution. What might be right for one building isn’t necessarily right for another, even in the same terrace.

    Find out more

    Visit Roger’s Huntwriter website

    Transcript

    Download a transcript of the interview with Roger Hunt.

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  • HPH287 : A beginner’s guide to retrofit – with Russell Smith

    HPH287 : A beginner’s guide to retrofit – with Russell Smith

    Russell Smith of Parity Projects explains why a whole house plan is the best way forward for tackling a renovation.

    Interview with Russell Smith

    Russell is a chartered civil engineer whose interest in renovation began after a secondment with the charity Forum for the Future. He began to understand the gravity of climate change and learn about the impact of energy and carbon emissions attributed to the housing stock. This led him to tackle his own housing renovation project, around 16 years ago, at a time when most of the talk was about new builds.

    The renovation of his Victorian property managed to get his heating bills down to around £50 per year. He opened his house up to around 3,000 visitors during the three years he worked on it and was honest with them about what he had discovered, how hard it was and how much it cost.

    Russell realised there was a business opportunity in it and started his own company, Parity Projects.

    A ‘whole house retrofit’ is something of a misnomer

    Russell describes retrofit as being the bits and pieces that are retrospectively fitted. A whole house retrofit is actually a deep refurbishment where everything is done at once.

    “Provided you’ve got a game plan right at the start knowing how everything should fit together in the long-term then your retrofits should add up to a whole house refurbishment in the long-term.”

    Too much information can scare off new customers

    Providing full and detailed calculations and drawings at the outset is likely to overwhelm the majority of people, as they wouldn’t be aware that quite so much was needed.

    Instead, Russell starts by using just enough data to help a customer understand the size of the problem and the opportunity of what is possible with the house. By displaying what the priorities are, they can agree on an appropriate package of measures before moving to the next phase. This would involve much deeper analysis and calculations for every element of the building.

    Phasing a renovation over time takes extra consideration

    Russell explains it can be particularly difficult to get all the elements to fit together if they’re not carried out together in one plan.

    “If you’re only installing some of the measures or you’re only tackling some of the things that you would want to do upfront, really you want to make sure that those things don’t have to be undone to do the next things later on.”

    So ideally it makes the most sense to carry it out in one go if possible. It’s the least costly way of doing it, materials can be bought in bulk, it can all be carried out while no one is living there, it doesn’t have to be tidied away completely at the end of each day, and the airtightness layer and ventilation can be considered for the whole building rather than just room by room.

    Russell does acknowledge that this won’t always be possible as people might not have somewhere else to stay or the finances available all at once.

    Ultimately we want to reduce our demand for heat

    The first step therefore is looking at where heat is being lost. Using the example of a three-bedroom semi-detached property, he explains the different areas:

    Solid walls

    The biggest proportion of heat loss will be through the walls, and without a cavity the insulation will need to either go on the outside or the inside of the building. Careful consideration needs to be given into the way the building was designed to behave, and whether there is already moisture in the brickwork that needs to dry out before any work can start. External wall insulation can be relatively straightforward provided it’s designed properly.

    Windows and doors

    This involves heat loss both through the windows and doors themselves, as well as infiltration around the outsides where they have been installed. If they’re not going to be replaced then the gaps around the structures need to be dealt with very well.

    Under-floor

    Russell says typically around 15% of the heat loss can be through the floor so it’s important to address it early on.

    Roof

    The roof makes up a large part of the surface area of the house and there are plenty of elements which make each unique, such as the different type, orientation, and rainfall.

    Ventilation

    Once the building has been made more airtight and insulated, you need to ensure a good level of ventilation so that the air quality for the occupants is of a high standard.

    “Once you’ve got all of those things dealt with in combination, you’ve resulted in a much lower energy demand than you would have done in the first place. And that’s the point to start considering your heating system and how you would put some heat into the building.”

    The Passivhaus standard deals with these elements

    It is important to ensure that you are ventilating and insulating in combination to get to such low levels of heat demand where a heating system can be virtually unnecessary. But while that’s an aim for every property, the restrictions of budget, priorities and logistics will mean that not every building will be able to reach that.

    There needs to be government backing

    Russell believes there needs to be a government campaign to make people understand the potential of their property and where it can get to provided that strong decisions for a whole house plan are made.

    “It’s got to happen. We’ve got no choice. That is going to happen so that when they are planning their shiny new kitchen, the new bedroom or they’re just redecorating, they can incorporate those things into their thinking.”

    There also need to be low-interest finance options to enable people to move forward.

    Quality depends on good communication

    Quality starts with the design, putting the right list of things together and communicating it properly to the contractor.

    “I think people tend to bash contractors in the first instance for poor quality but the bottom line is, if the contractor’s not been told what to do very well then it’s never going to work.”

    Something Russell has been working on for the last seven years with a cooperative he set up called RetrofitWorks, is bringing those disparate parts of the industry together as part of one organisation. The aim is to give everyone tools at their disposal to do the design, communicate with each other and implement the work so that they can all check anything at every step of the way.

    Cosy Homes Oxfordshire is a manifestation of the key partners they have built up in that area. With some central government funding buying into the model they have been able to define the marketing, clearly describe the approach they think their customers want, design their processes as a cooperative, push forward with the advice, the whole house plans, the detailed design and putting a tender process in place so the right contractors are selected and they can make sure their work is done well.

    Charlie Luxton visits a deep retrofit in central Oxford

    Charlie Luxton visits a refurbishment of a listed barn

    Charlie Luxton checks out a retrofit of a semi-detached property

    They have also used their established supply chains with the creation of the Warmer Sussex scheme, and Ecofurb which will be launching in London soon.

    There aren’t enough skilled workers to meet government targets

    Parity Projects have used modelling tools to identify that the current workforce of around 160,000 in the sector would need to be virtually tripled in order to achieve the government’s target of every house in the UK hitting a minimum EPC score of C by 2030.

    Russell sees this time as a massive opportunity to be training people up from other industries for working in managerial roles as well as the labourers. He thinks that all students in the building sector should complete the same one year course before branching out into their specialities. That way there might be more respect and understanding on site.

    Select a team that is willing to learn

    Russell’s advice to a homeowner considering a renovation project would be to contact a local retrofit coordinator. They will be able to give you advice and technical knowledge to put a plan in place for your property.

    He stresses that if you’re going to do your home up you will probably need to accept that some people working on it might need to learn something new, so ensure that you team up with people that have the right attitude, a genuine interest and are keen to help. Even if they don’t necessarily know it, they will learn and find out.

    There are also free resources available on the AECB website in their Knowledgebase section, and from the Centre for Sustainable Energy.

    Find out more

    Visit the website of Parity Projects

    Learn more about RetrofitWorks

    Follow Russell Smith on Twitter

    Check out our previous episodes with Parity Projects, about what to expect from a detailed energy assessment, and how an assessment can inform retrofit measures.

    Parity Projects carry out an energy assessment at Ben’s parents’ house

    Transcript

    Download a transcript of the interview with Russell Smith.

    Please connect with me

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  • HPH277 : The importance of building performance evaluation – with Professor Fionn Stevenson

    HPH277 : The importance of building performance evaluation – with Professor Fionn Stevenson

    Professor Fionn Stevenson explains why building performance monitoring and post-occupancy evaluation should be mandatory on new homes.

    Interview with Fionn Stevenson

    Having spent eight years in practice as a chartered architect, Fionn was finding that the housing wasn’t performing as well as she had designed it to do. This led to her interest in building performance and eventually she became a researcher and academic in the subject, as Professor at University of Sheffield – School of Architecture. She has now been involved in building performance for over 20 years.

    Six simple action points in a light touch review

    A light touch post-occupancy evaluation involves going into a home to check how well it’s performing against its design intentions.

    The first step is for the expert to spend around half a day studying the original drawings and specifications for the project, as these are what will be checked against during a tour of the home. They provide the baseline of what is supposed to have been done.

    This is followed by a half day tour of the home with the occupants, plus the designer and contractor. The occupants will explain about living in the house for the evaluator to see what’s going on and check that against the original design intentions.

    The occupants will also complete a simple two-page survey which provides a lot of further information.

    A half day thermographic imaging survey is then carried out to see how the fabric of the building is really working.

    Next is looking at how the building is performing in terms of energy used and water consumption. This can be done at the simplest level of looking at utility bills, or recorded through smart metres.

    And finally, there will be a spot check where, during the half day tour, the evaluator will use a hand-held 4-in-1 metre to check on the room temperatures, plus levels of light, sound and humidity.

    UK housing doesn’t perform as it should

    Given the nature of unique sites and being very contextual, Fionn says UK housing does not perform as it is expected to do. She says that research shows that on average new homes in the UK use at least twice the amount of energy they’re supposed to use. That can be down to the design but also the quality of construction.

    Another concern is the indoor air quality results, with high levels of carbon dioxide build-up, low-level toxins from off-gassing of new materials, and air fresheners which are supposed to make the air quality better but can actually make it worse. New homes need to have good ventilation strategies, but often they have been poorly designed, constructed or commissioned.

    Building evaluation should be mandatory

    As well as post-occupancy evaluation, there can also be building performance evaluation. This involves starting the evaluation process from as early as developing the brief, and right through the complete cycle of the project.

    Fionn says it’s amazing that there is no mandatory requirement to carry out post-occupancy or building performance evaluations, and that is something she is lobbying to get changed. The RIBA is now producing new guidance and in the future is looking to mandate its practitioners to make it a part of their service. But there’s no mandatory requirement to carry it out as currently it requires consent from the client.

    “If it was mandatory there would be an automatic performance feedback loop because people would have to automatically report what is actually going on in the housing. That reporting would then go into databases and everyone could see what was going on.”

    Fionn has worked with a number of volume housebuilders, and says that although they carry out extensive customer satisfaction surveys to see how well their buildings are performing, they are not asking the right questions. They don’t drill down into why the house is or isn’t working for them, and this is because they haven’t had to be accountable for the performance in mandatory terms.

    “What they’re interested in is selling the home. They’re not as interested in how well the home is performing once they’ve sold it. They just want to make sure the customer is happy, they want to make sure that they get their NHBC scorecard with the highest number of stars, and that’s all about reputation. And their reputation rests on the initial customer satisfaction survey, not the overall performance of their homes.”

    There needs to be databases of results

    Fionn mentions the Building Performance Network as being a group of organisations and experts who are spearheading the drive to make building performance evaluation and post-occupancy evaluation routine. They are collecting data and setting up a UK database.

    And Fionn says that this is what needs to be happening. She says there should be two databases: one a private one where people can access their own data, and the other a public one with anonymised results to give a national picture of how everyone is doing and enable people to benchmark and compare against others.

    A culture shift is required

    Fionn explains that at the moment the process for architects and clients is “let’s design a home.” In fact what it should be, is “let’s design and evaluate the performance of a home.” The majority of architects don’t go back to really evaluate how well their buildings are performing. Fionn says the key message she is trying to get across in her book is that this should be routine.

    Be energy sufficient, not just energy efficient

    Fionn is in the process of starting her own self build project. But rather than design it herself, as she has been out of practice working as an academic for so long now, she is using the networks she has built up to find the best team to deliver her project.

    She has prepared her brief and will be looking for people that will champion her wants, needs and follow the details of the brief throughout.

    A fabric first approach will be used to make sure the house is properly insulated, airtight and ventilated. With that is the importance of getting the size of the home right. She explains that it’s not enough just to be energy efficient, but we need to think about whether we are being energy sufficient. In other words, having the house optimally sized and not any larger than it needs to be.

    “There’s a bit of a misnomer about zero-carbon because of course you can make your home automatically zero-carbon if you go onto a renewable energy supplier. But that doesn’t mean your home is actually being very good for the environment. We’ve got very large self-built homes that are claiming to be exceptionally low energy or carbon zero but actually the embodied energy, the amount of materials that are being used in them is huge.”

    Keep the buildings simple

    Fionn says that there is a temptation with self build to have the house of your dreams and put in a lot of unnecessary kit. Her own research has found that often in homes that were using heat pumps together with PV and solar-thermal, often they were contradicting each other as they weren’t designed to work together. Also, solar renewable energy installations hadn’t been installed correctly or on the wrong orientation, meaning they weren’t performing as they had been designed to do.

    Another thing the post-occupancy evaluations have thrown up, is how important it is for any mechanical ventilation system to be well designed, brilliantly constructed and have the minimum duct runs possible. It must have vents perfectly positioned and be ergonomically designed in a way that is accessible for the occupant to interact with it.

    There isn’t enough data to help self-builders with decision-making

    Fionn explains that we’re still flying blind with a lot of modern building systems as there just isn’t enough data from post-occupancy evaluations to see how well they perform. Being laboratory tested can only do so much.

    “Who is going out there, outside of the laboratories, into the homes with the thermal imaging camera, doing the walkaround, seeing the little bits of mould that are appearing in the corners? If we move on to service systems, we’ve got loads of mechanical ventilation heat recovery systems. But who went out there and actually asked the occupants whether they can use them? That’s been the issue, that it is difficult for self-builders to choose systems and know that those systems have been not just rigorously tested in the laboratory where the products are developed but that they’d been systematically tested around the country in every city, in every town, as a routine part of post-occupancy evaluation which is then fed back into the industry. This is exactly why the housing industry performs so badly.”

    An investment worth making

    Fionn stresses that you should be alert throughout the whole design, build and occupancy process, but there are key points where attention particularly should be paid.

    The first is at the outset of the project, where post-occupancy evaluation is included in the brief, and budget allocated for it. Typically it might cost around £5,000 for a light touch post-occupancy evaluation, but it could be saving you tens of thousands in identifying hidden risks and defects.

    Other benefits are that you’re also future-proofing for climate changes, ensuring there won’t be overheating as UK summers continue to get hotter, and also improving health issues with better air quality.

    The second critical stage is the commissioning of the home. When the services, heating and ventilation systems are commissioned is a crucial time for there to be an independent evaluator checking whether they have been set up properly, to avoid a lot of problems down the line.

    Find out more

    Follow Fionn Stevenson on Twitter

    Check out Fionn’s book:

    Transcript

    Download a transcript of the interview with Fionn Stevenson.

    Facebook Group

    If you’re on the self build journey and would like to connect with other like-minded people in our private Facebook group, then apply to join at talkselfbuild.com.

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  • HPH270 : What is the WELL Building Standard? – with Olga Turner Baker from Ekkist

    HPH270 : What is the WELL Building Standard? – with Olga Turner Baker from Ekkist

    Olga Turner Baker describes the WELL Building Standard and explains how the principles can be applied to improve health and well-being on individual projects.

    Interview with Olga Turner Baker

    Olga is a chartered surveyor by training. She first came across the WELL Building Standard back in 2016, and was surprised to find it wasn’t being adopted more widely in the UK. She quickly became passionate about it and started her own business, Ekkist, to specialise in design-led buildings, with a specific focus on health and well-being within.

    Ori House

    The WELL Building Standard is based on medical research

    Launching in the United States in 2014, the WELL Building Standard took all the medical research that had taken place around the world that looked at how buildings impact our health, collated it over a seven year period and turned it into a building code.

    Olga explains it as being a review of all the best practice and best guidance, of all the different components of building design. It covers the best guidance on air quality, water filtration, the safe use of building materials, and even through to management of buildings and how to operate them. It also touches on things like mental health and sense of community.

    While there are criteria that must be met in order to achieve the minimum certification, there are also optimisations which are points that can be earned to get to a higher level.

    Olga describes it as a very technical standard, where you submit documentation and are also tested in practice through performance verification testing. It is a robust procedure which assesses the building in use as well as in design.

    There are ten core areas of buildings that the standard covers:

    Air

    This looks at air filtration and ventilation, keeping the worst of the chemicals and particulate matter and dust out of the buildings, so as not to exacerbate things like allergens or asthma.

    Water

    In much the same way as air filtration, this is to keep out anything that could be harmful, such as coliforms, public water additives, agricultural contaminants, and by-products of disinfectants. It’s about ensuring that the water has been filtered to a high quality, which can be through a carbon filtration system or reverse osmosis.

    Nourishment

    Probably more relevant to buildings that have an operator providing food on site, but also adaptable to our own homes, this looks at the kind of food that is provided within a building. It considers portion sizes, allergen labelling, and reduction of added and refined sugars and any kinds of additives. It encourages healthy food messaging by promoting ethical sourcing of products and eating as much fruit and vegetables as possible.

    Light

    Ensuring we have the right light in buildings helps keep the circadian rhythm and body clock functioning as well as possible. The standard has guidance on sufficient distances from windows, making sure rooms aren’t too deep for the windows provided, and that the right colour quality is being used in relation to the time of day or night.

    Movement

    This thinks about how we encourage activity in the building to improve health. It can be about connection with the outdoors to make it easy for children to play, or in larger buildings it may be about ways of encouraging staircase use rather than lifts.

    Outside of the WELL Standard, but another idea that Olga suggests, is making outdoor space that is usable throughout the seasons, which will naturally encourage more outdoor activity for longer periods of the year.

    Thermal comfort

    Keeping buildings within comfortable thermal parameters is important for not aggravating conditions like asthma, eczema and stress, and making sure that our skin, eyes and organs function properly. Achieving this might be through shading and natural ventilation or mechanical cooling and ventilation systems.

    Sound

    Although not a mandatory part of the WELL Standard, acoustics make up an optimisation which far exceed UK building regulations.

    It looks at both transference of noise between rooms and also transference within a room. Olga says there are plenty of products on the market which can help absorb noise, and materials she particularly likes using for this are cork and clay plaster.

    Materials

    Firstly this looks to avoid materials that we know to be toxic, such as asbestos, mercury, lead and PCBs. In the optimisations of the standard it also considers VOCs and how they can be released from furniture, varnishes, paints and glues. When you’re designing a home you should be trying to reduce these levels by looking at natural sealants and products like sheep’s wool as a furnishing fabric and natural oils.

    As well as reading the specifications on the products, Olga suggests looking for external accreditation that any product you are using has been tested for a health component. Examples of these include Cradle to Cradle and Oeko-Tex.

    Mind

    This looks at how buildings impact our mental health, and what can be done to encourage better mental health through building design.

    Much of this can be down to access to nature, whether that be views across to green spaces or incorporating greenery in and around your rooms.

    Ori House

    And even using wood and other natural materials has been found to have calming effects.

    Community

    The WELL Standard looks at access to community services, community programmes, and how you’re incorporating the wider community as part of your building and initiative.

    Olga also recommends looking at the new NHS Social Prescribing Guidelines, which emphasise how our personal health can really gain from spending time with others, whether that be in group activities, gardening, etc.

    Innovation

    Olga describes innovation as being the most fun part of the WELL Standard. It is where you can be awarded points for coming up with new ideas that help increase health and wellbeing within buildings, that aren’t already covered by the standard. This could be anything like different lighting or having pets on site, as long as there is medical research to support the benefits.

    WELL Standard principles can be applied to individual projects

    While it is not possible to certify a single building, (there must be a minimum of five units and they have to have a common structural element) the principles and good design practice can be applied to individual projects.

    While some designers might be doing these things intuitively anyway as good design practice, for others the standard can just push them a bit further and support them with the scientific research.

    Ori House applies the principles

    Ekkist have worked on a conceptual standalone dwelling, Ori House, where they have applied the principles and taken on the parts that really resonate to homeowners, such as the daylight, air quality, water filtration, and using space better for social interaction but also to encourage privacy within the home.

    “We’ve tried to really think about that and create our own version of what it means to be a community but on an individual building level.”

    Ekkist are currently looking for sites to build this on, and are also working on an urban version, which Olga sees as being important as cities become ever more urbanised.

    “We want the quality and the health benefits of a rural home delivered in an urban environment. That’s our next big goal.”

    Find out more

    Visit the website of Ekkist

    Follow Ekkist on Twitter

    Find out more about the WELL Building Standard

    Check out our episode with Elinor Elisa about how she created a healthy home for her family.

    Transcript

    Download a transcript of the interview with Olga Turner Baker

    Please connect with me

    Subscribe, rate and review the podcast in iTunes

    Rate and review the podcast on Stitcher

    Like our Facebook page

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  • HPH256 : What makes a well designed MVHR system? – with Tom Heywood

    HPH256 : What makes a well designed MVHR system? – with Tom Heywood

    Tom Heywood from Green Building Store explains why we need mechanical ventilation with heat recovery in high performance homes and why it needs to be well designed.

    Interview with Tom Heywood

    Tom studied architectural technology at university and was disappointed not to have been taught anything there about efficient building. So when it came to doing his dissertation he wanted to do something different, and decided to write it on Passivhaus principles.

    Tom is now the MVHR design manager at the Green Building Store.

    Airtight buildings need mechanical ventilation

    Natural ventilation tends to be unreliable. The supply levels might depend on how windy it is, with areas of the building in the path of the wind receiving more than elsewhere. There isn’t a way of delivering a particular amount according to the requirements of a specific area.

    With the increased ability to make buildings more airtight, comes the reduction of natural ventilation through trickle vents and leaky building fabric. At this point mechanical ventilation is required to provide enough fresh air to keep CO2 levels down and prevent dangerous build-ups of volatile organic compounds and other indoor pollutants.

    With a properly commissioned MVHR and an airtight envelope, you can deliver the right amount of fresh air to different spaces, ie more for a double bedroom than a single. The MVHR unit will also extract as much heat as it can from the exhaust air which will in turn drive down the heating load.

    Tom suggests that, as a rough guide, when you get to less than five air changes per hour, that’s when you should start introducing some form of mechanical ventilation, such as Mechanical Extract Ventilation (which is just extracting, not supplying or recovering any heat).

    Once you get down to three air changes per hour an MVHR starts to make sense, because then there’s not as much cooling going on with natural ventilation coming in.

    The MVHR supplies clean, fresh air

    An MVHR unit has two fans – a supply and an extract, and a heat exchanger. Stale, moist air (such as is produced in bathrooms, kitchens and utility rooms) is extracted and goes back to the heat exchanger, which is where the fans are.

    The heat is transferred to the incoming fresh air that is then supplied to the habitable rooms, such as the bedrooms and living areas. The air is also filtered, ensuring a clean, fresh air supply to the rooms.

    Concentrate on getting the design right

    “People often focus mainly on the specification of components, which is right, but at the same time you can spend as much money as you want on the specification of components; if it’s not designed right, they’re not going to work anyway. You’re going to have to turn it off because it will be too loud and it will be inefficient.“

    Rather than someone who provides a schematic of some ducting on a piece of paper, you want someone who is going to design it around the structure to make sure when you get to site that it will work efficiently and that the air supply will actually make it all the way along the ducting route to the required rooms.

    Tom says key information to ask from a designer at the design stage is for sound data and pressure loss data. Pressure loss is the resistance that the duct is providing to the airflow. If pressure loss is too high the fans will have to work harder to push the air through. And when the fans are working harder, it will increase energy consumption and the noise will be louder. Likewise, if you never change the filters, the fans will have to work harder to drive the air through.

    Tom says it’s always good to oversize the unit so that it’s not running too hard.

    He stresses how important it is to get the system designed early. Even as soon as the architects and engineers are doing their drawings you should be getting your plans submitted to a designer to get their opinion on unit location, duct sizing, where they need to run and what sized joists are needed to accommodate them.

    There are branch and radial systems

    Tom likes the branch systems (of rigid ducting) because it’s easier to get a low pressure loss with careful sizing of ducts.

    “A lot of people think that the radial system saves space, but if it’s done properly, instead of having one one-hundred mill. duct to, say, a bedroom, you’d have two ninety mill. ducts. Because those ducts are carrying the same amount of air but they’re smaller, so there needs to be more of them to compensate for that.”

    A radial system, also called an octopus system, has a main manifold at the start which is a box with lots of small spigots on it. The semi-rigid plastic radial ducting plugs into that and goes off to the rooms. Each room would have its own branch (or two or three), all the way from the manifold at the start to the air valve in the room. It is a good system for preventing any cross-talk sound travelling from room to room because the sound can’t make it all the way along the ducts.

    Tom believes radial systems do have their uses, especially in retrofits where the rigid ducts of a branch system would just be too big to get in.

    Whatever system is used, Tom stresses that the component parts should be on site when the joists are being put in place, so they can be installed as the joists are being erected.

    Commissioning a system takes a lot of toing and froing!

    Tom explains the method of commissioning a branch system. The unit is told what it is running at, eg 300m³ per hour on fan speed 2. If the supply to a master bedroom was to be 35m³ per hour then they would go into that bedroom and adjust the damper to allow more or less accordingly until it was at the required amount. An anemometer over the air valve measures how much air is coming out.

    But as that valve is closed down it will drive the air into another air valve somewhere else. So the next room would need to be checked to see if it has been impacted and needs adjusting. Any changes to one mean going back and checking all the others again, as it’s all on one system.

    Carefully consider external vent placement

    Ideally you want the intake and exhaust ducts on the north elevation. That way they’ll be shaded from the sun in the peak summer heat. The system will work more efficiently because you’re bringing in cooler, shaded air.

    You should also avoid placing them right next to a window or facing onto a neighbour’s garden, because they could be blowing quite hard and at audible levels.

    Too close to the ground and they could drag up leaves, debris and animal hairs into the intake duct, which will block up the filters more quickly. Ideally they should be 1.5m above ground level.

    If incoming smoke from neighbouring properties is a problem, then you can get active carbon filters which filter out the smell and smoke even better than the F7 pollen filters would.

    The controls should rarely need using

    The idea of the controls is to have them as simple as possible and generally left running on fan speed 2. They may only really need changing if you’re going to be away from the house for a long time, in which case you could drop it down to fan speed 1. And if you have a large gathering and are going to be doing lots of cooking, then hit the ‘party button’ which increases it to fan speed 3 for 45 minutes, before automatically dropping back down to fan speed 2.

    Generally there would be one main controller which would usually be in the kitchen for convenience to boost it if required. Alternatively you could have the main controller somewhere else with just a remote boost switch in the kitchen. Tom doesn’t recommend having it in a bathroom as boosting the system while showering early in the morning and late at night could become audible in the bedrooms and disturb the occupants. The fan is designed anyway to remove enough moisture whilst showering without the need to boost.

    Only a small amount of maintenance is required

    There shouldn’t really be too much maintenance required, other than changing filters every three to six months (depending on indoor and outdoor air quality, and whether you have children and pets).

    After five years it might be worth unscrewing the air valves in the bathroom and giving them a clean as they could collect dust and towel lint over time.

    And depending on the MVHR unit specified, the extract fan may need very careful cleaning, preferably by someone who has done it before.

    If the unit is turned off for more than two or three days there could be a risk of mould growth in the ducts. There shouldn’t however be any danger of that happening if the system is left on and each branch to each room has air flowing through it.

    Find out more

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  • HPH247 : Two radical retrofits that use an internal wall insulation strategy – with Bill Butcher

    HPH247 : Two radical retrofits that use an internal wall insulation strategy – with Bill Butcher

    Bill Butcher from Green Building Company, the construction division of Green Building Store, explains how they tackled two radical retrofit projects in West Yorkshire. Each took a ‘whole house’ fabric first approach in order to improve comfort levels and reduce the heating bills.

    Having been Passivhaus pioneers in the UK with their Denby Dale project, the building team at Green Building Company has kept honing their approach.

    There was Golcar new build project and Stirley Community Farm retrofit. Now we look at two of their radical retrofit projects, Cumberworth and Lower Royd, and how they embrace the same philosophy but still require bespoke solutions.

    Cumberworth retrofit after the work was completed

    Cumberworth radical retrofit

    Initially this was part barn conversion and part 1990s extension, so there needed to be two different strategies for this project.

    The existing property was hard to heat

    The owners were spending £3,500 a year on LPG trying to keep this 150m2 property warm but they were still cold!

    A whole house ‘fabric first’ strategy was adopted

    In order to make the house more comfortable and reduce heating bills they embarked on a deep retrofit. This embraced the Passivhaus methodology of making the house draught free, increasing the levels of insulation, reducing thermal bridging and introducing mechanical ventilation with heat recovery.

    The designs were modelled in the Passive House Planning Package (PHPP).

    Insulating internally maintained the natural stone facade

    While a lot of retrofits use external wall insulation, there are a few reasons why they didn’t. Cumberworth is at the top of the Pennines and it is exposed to a lot of moisture. The natural stone works well in these parts.

    Bill continues: “To build in any other way is totally out of character for this region. And that’s what the customer wants.”

    The three moisture risks had to be addressed

    The moisture risk depends on the wall build-up. The ex-barn wall had two stone leaves which were filled with rubble! Being a Victorian barn it was also susceptible to rising damp because there was no damp proof course.

    In this high exposure region on the Pennines rain driven damp through the porous stone was another risk.

    The third moisture risk is interstitial condensation which is the condensation of internal moist air reaching the dew point where it turns to water as it meets a cold wall.

    This section of the building was insulated was a product called TecTem, which is vapour open and breathes like the original building would have done.

    WUFI was used to model the moisture risks

    A German software package called WUFI was used to look at the moisture risks. To increase accuracy it requires a lot of information first.

    Bills gives a few examples: “It takes into account where you are, the orientation of the wall – obviously a West wall up here is in more danger than the East wall because most of our rain comes from the West – the rising damp, the type of stone it is, which quarry it’s from, the mortar joints and so forth, and then obviously the insulation.”

    Moisture sensors in the walls help monitor the situation and allow Bill to assess the accuracy of the program. “I might say that all of the buildings are performing fine.”

    Insulating the extension was simpler

    As the 1990s part of the Cumberworth project is a cavity wall construction it should be less susceptible to rain-driven damp. And it’s got a damp proof course which should deal with rising damp.

    A ground source heat pump is the heat source

    For a new build Passivhaus the energy demand would be so low that underfloor heating would not be appropriate. In a retrofit situation it becomes more relevant.

    Also the clients had a field in front of the house which they were keen to use for a ground source heat pump.

    Bill explains: “Air source and ground source heat pumps work most efficiently at delivering 35C water, hot water if you like, for your central heating system. And that suits underfloor heating more than radiators. That then informs how you do the floor. Because we don’t want to be heating up masses of concrete in a floor because of the slow cooling and heating – it doesn’t respond. “

    So it’s only 75mm of heating screed on top of the insulation.

    The insulation follows the line of the roof

    As with most of Green Building Company’s retrofit projects they have gone for a cathedral roof. This means the insulation is within the structural timber roof and that the loft space is inside the thermal envelope.

    Bill says: ” What we tend to end up doing is having a studwork parallel with our rafters. So we end up with insulation between the rafters, insulation again, and then within the studwork which is between the purlins more insulation. So, we would use more rigid bats between the rafters – a mineral wool in our case – and the studwork, and then just ordinary loft fibreglass insulation between.”

    MVHR duct runs were down corridors

    As this is a low energy retrofit a mechanical ventilation with heat recovery was specified. It goes without saying that these are fairly intrusive, requiring a plant room for the unit and ducting around the house.

    While a new build Passivhaus might use posijoists in the intermediate floor, in a retrofit situation you have to come up with other solutions.

    Bill explains that they ran the ducting down the corridor because this was an area where a lower ceiling is not so noticeable.

    Vaccuum insulated panels were used around some window reveals

    Green Building Store had already supplied outward-opening triple glazed windows to this property five years previously and hence they were keen to keep these!

    One challenge they faced was in maintaining the continuity of insulation.

    Bill explains: “If you do it [insulation] well in ninety percent of your building, for example, the ten percent becomes very vulnerable to condensation and cold bridging. So, the reveals between the very good wall insulation we were doing, in to the window frame, only allowed for a ten millimetre insulation.”

    To maintain that u-value at this thickness they needed to use vacuum insulated panels, custom made to fit!

    Lower Royd after retrofit work

    Lower Royd radical retrofit

    Much like Cumberworth, this project had two different parts. One was a virgin barn and the other was an existing farmhouse that hadn’t been touched since the 1960s. So it was ripe for a retrofit.

    A connection to mains gas helped inform the project

    Despite it’s fairly remote location Lower Royd had a mains gas connection.

    The clients had envisaged using a ground source heat pump to heat the house, but in terms of economics, their money could be better spent on insulation!

    Bill comments: “A ground source heat pump may cost you twenty-grand to get into the building as opposed to gas and the standard boiler – and we’re talking about the smallest condensing boiler, off the shelf from your local builder’s merchant – costing, installed, fifteen-hundred, two-grand. You’re better off with that saving of fifteen-grand, say, to be put into your fabric. The cheapest energy is the energy you save.“

    And of course this doesn’t rule out changing the heating system to an air source or ground source heat pump further down the line.

    A spray-on lime based insulation saved flattening the walls

    On the Cumberworth project they used a rigid insulation called TecTem. However, they had to invest a lot of time in flattening the walls to be able to apply it properly. So they were keen to consider other alternatives at Lower Royd.

    So they trialled a spray-on internal wall insulation from Italy called Diathonite Evolution.

    Not only is it airtight, but it is vapour and capillary open to address any moisture issues.

    And being a lime product, it naturally inhibits mould growth.

    Airtightness is the most important factor for comfort

    Having carried out a few deep retrofits, Bill believes that when it comes to energy and comfort, airtightness is the most important factor. Then insulation comes next.

    In fact they may experiment with reducing the insulation levels a little on future projects and look at the impact.

    Find out more

    Visit the website of Green Building Store

    Follow Green Building Store on Twitter

    Follow Bill Butcher on Twitter

    Transcript

    Download a transcript of the interview with Bill Butcher.

    Please connect with me

    Subscribe, rate and review the podcast in iTunes

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