Tag: U-value

HPH279 : A beginner’s guide to building terminology – with Lee Fordham from Architype
Lee Fordham from Architype simplifies some of the terminology you might come across if you’re thinking about doing a sustainable self build.

Interview with Lee Fordham

Shortly after qualifying as an architect in 2004, Lee spent time travelling and working for architecture practices in New Zealand and Australia. When he returned to the UK he decided to pursue his passion for sustainable design and started working at Architype, one of the UK’s leading sustainable architects, where he is now an Associate Director.

A beginner’s guide to terminology

For those that are just setting out in their self build journey there can be an overwhelming array of technical terminology used that can be baffling to anyone outside of the industry. Lee takes us through some of the common terms that you might come across in a sustainable self build.

Passivhaus / Passive House

Passivhaus (Passive House in the United States) is a building standard that was developed in Germany around 30 years ago. Using physics, the aim is to reduce the performance gap between how the building is designed to perform, and how it actually performs.

The aim is to make the building more comfortable for the occupants and reduce how much energy the building uses, which is done with a better quality of build.

Liz and Mike Hill’s Passivhaus – designed by Architype

The experts will use the Passivhaus Planning Package (which you’ll hear referred to as PHPP), which essentially is a very complicated spreadsheet of data that allows them to design a building that will meet the Passivhaus criteria. The contractor will use that information to construct the building, and a certifier will guarantee the work and certify it if it meets the required standard.

Passivhaus plaque

MVHR

You’ll commonly hear a Mechanical Ventilation Heat Recovery system referred to as an MVHR. They’re most likely to be used in Passivhaus buildings, but not exclusively. It is a ventilation system which extracts the used air from inside a building. It takes the heat from that air and mixes it with fresh air which is being brought into the building from outside, to provide every room with fresh, pre-warmed air.

The air is filtered coming into the building, and different filters can be used according to whatever is in the external air in that area.

A key benefit over natural ventilation is the element of control over any given space, ie removing moisture from bathrooms etc.

An MVHR for a domestic dwelling is roughly the size of a combi-boiler and will need to be incorporated into the building’s design.

MVHR unit at Landsdowne Drive Passivhaus – Green Building Store

Foundations / Footings

These will usually be designed by a structural engineer and are what sit under the building to evenly transfer the weight of the building to the earth. The type you use might be dependent on what your ground conditions are like, but some examples are pile foundations, deep strip foundations and raft foundations.

U-value

A complicated one to explain, but essentially it’s a way of measuring how thermally conductive a component or a series of components (like a piece of glass, wall or roof) is. It is the rate at which heat travels through. The lower the U-value, the better it is.

The aim is to have fairly consistent U-values across all the components in a building. Having just one element that isn’t consistent could act as a magnet for moisture and potentially damage the structure. This can partly be achieved by better insulation, triple-glazed windows etc.

The U-values form part of the data that feeds into the PHPP system.

Airtightness

At a very basic level, this is about eliminating drafts in a building. It’s relatively easy to achieve but needs to be thought about at the design stage. At Architype they denote the airtightness layer on their detailed drawings using a red line, which shows the contractors where to take particular care in the construction so as not to damage it.

To meet building regulations, when the building is finished an air test will be carried out. The building has a giant fan attached to it and is either positively pressured, ie blowing air in, or negatively pressured, ie extracting air. The rate at which the air leaks gives you your air test result. It is a measure in pascals of the pressure of an internal area. Building regs require you to get a result of 10 or less.

The method in a Passivhaus building is slightly different. This takes an average reading from the building being both positively and negatively pressured, to give an n50 value which is how many volumes of air changes there are in an hour. The Passivhaus requirement is that it should be less than 0.6, so significantly better than building regulations.

Build system / construction method

This is a way of describing what method you are going to use to construct your building. Examples include timber frame, masonry, brick and block, insulated concrete formwork (ICF), pre-cast concrete, in-situ concrete, and cross-laminated timber.

Pre-fabrication

Pre-fabrication is where components, or indeed whole buildings, are made off-site. This could be from wall panels, to timber frames, to bathrooms that are fully plumbed and tiled, to entire houses.

MAKAR production facility

You can even go to the factories and choose your handles, paint finishes, floor finishes etc. When they reach the site they are connected together. The advantages of building the elements off-site is it can be quicker, they’re not subject to delays or damage from the weather, and often it can result in better quality and working better when brought to site.

Huf Haus

Zero carbon

Lee says that this is a difficult one to explain as there are many different interpretations of what it means.

Generally it refers to off-setting the energy use in a building. So the better your building is, ie a Passivhaus, the less carbon you have to off-set because you’re not using as much energy.

Looking deeper into it, some people will be referring to zero carbon in use, which is the energy that is used starting from the point of when it’s been built, through to its end of life.

But there’s also embodied or sequestered carbon, which takes into account everything to do with the design and construction of the building, together with the in-use energy and sometimes through to the demolition. This is more complicated to account for, although there are tools which can help explain for instance, how much energy is used in getting a tree from Germany to the UK to use in a timber frame.

Custom build

Whereas self build has many decisions for you to make, whether or not you’re doing it in the purest sense of building it yourself, or whether you’re commissioning someone to carry that out for you, custom build can take some of those decisions away from you. There will be an offering from the custom build company, but with options for you to customise it. That could be in terms of the style of the house, the layout or the finishes. It might not be as individual as you would get with a self build, but it can take away a lot of the headaches!

Potton Homes design

Solar shading / brise soleil

Effectively the same thing, brise soleil or solar shading would be used on the south facing side of a building to limit the sun coming in during the summer months when you don’t want the building to overheat, but allowing it to come in during the winter when the heat is required. Generally it would be a horizontal component that sits over the south facing glazing, whether that be a roof overhang, external canopy or series of louvres.

External louvres – Charlie Luxton Design

Wimbish Passivhaus Scheme – Parsons & Whittley

Ditchingham Passivhaus Scheme – Parsons & Whittley

On an east or west elevation you would usually have a vertical component, and that’s just to do with the angle of the sun at certain times of day and certain times of year. Windows on the east and west elevation can be harder for dealing with glare and overheating issues.

Lee says the ideal situation is to have the building facing south where the solar gains can be controlled more easily.

Design team

The core members of a design team are likely to include: an architect, structural engineer, civil engineer, mechanical and electrical (M&E) engineer, and possibly a project manager.

Beyond that, depending on your site and your level of involvement and interests, you might also have: landscape architect, ecologist, arboriculturist, quantity surveyor, Passivhaus designer etc.

Renewables

Renewables refers to technology that generates energy. This could be photovoltaics, wind turbines, hydro power etc.

Air source and ground source heat pumps

An air source heat pump takes energy from the temperature in the air. Any air above zero degrees has energy in it and this can be taken and transferred into heat or hot water for your house. Similar in size to a washing machine, they’re put on the outside of a building.

The ground source heat pump works in much the same way but will take the energy from the ground. They have pipes which can either be spread horizontally in the ground which will require a lot of space, or as a vertical spread of pipes, which need less space but are a lot more expensive.

Plans, elevations, sections and details

These are examples of the different types of design drawings, created by Parsons and Whittley for Ben Adam-Smith’s house:

Plan – This is an aerial view, looking down onto the building. You can have different plans to show each floor of the building, but they can show the roof, doors, walls and windows, together with the internal layout.

Elevation – An elevation is a drawing of what the outsides of the building look like from where you’re standing. A south elevation for example would be the side of the building that is facing towards the south.

Section – This is like slicing down through a building to show what’s inside. It will show the components of the walls, floors, roof etc.

Details – By taking a section drawing and zooming in you will create a detail. They can be various scales, such as 1:2 or 1:10, and are an in-depth analysis and instruction for the contractor showing how to construct that part of the building. It would show them where the airtightness line is, where the insulation is, and how wide cavities would need to be.

Soft landings and performance monitoring

A soft landing is about making sure that once the building has been constructed, that the operator of that building knows how to use it. Obviously if you’ve built it yourself then this wouldn’t be necessary, but if you’ve largely commissioned other people to complete the project then you should have someone tell you how it all works.

Performance monitoring can take place throughout the build process but in particular Lee refers to monitoring once the building is complete. This uses sensors to check on things like the internal temperature, humidity and CO₂ levels, to make sure the building is performing as it was designed to do.

Tender

The way you tender will depend on what kind of contract you will have, but essentially a tender is a set of information that is put out to someone for a response. They will price up the aspects on the tender and return it with their figure and requested documentation. It can be a tender for a design team or for a contractor. The returned tender documents are then scored and weighted according to whatever your priorities might be. For some that might be 80% of the marks will be based on how competitive the price is, but for others they might weight it more heavily in favour of quality and not necessarily who is the cheapest.

A key thing is to make sure the information and drawings you are sending out are as comprehensive as possible. That way it can be priced accurately for what you will be needing. Without that detail they will be adding an element of price risk to their response which will invariably make it much more expensive.

Window parts
- Sill – The ledge at the bottom of the frame.
- Head – The top of a window where it meets the wall. It can be internal or external.
- Jamb – The side of the window
- Reveal – The part next to the jamb. Can be internal (usually plasterboard) or external (usually timber or brick). If the reveals are set very deep into the thickness of a wall they can provide some shading to the window
- Mullions and transoms – Found on traditional Victorian style windows, the mullions are the vertical bar in the middle of the window, and the transoms are the horizontal bar.
Roof parts
- Trusses – The pieces, usually made of wood, that actually make the roof structure
- Joists – A horizontal structural element that supports the floor and/or ceiling
- Eaves – The part of the roof that overhangs the wall. Usually if it’s a sloping roof it would be the part which overhangs the gutter
- Soffits – Underneath the eaves, the soffits are the horizontal section that you can see
- Ridge – The point right at the top of the roof, usually where two pitches come together
- Verge – The part at the side of the house. Usually there would be a bargeboard or piece of wood that goes down the side
- Parapet – Usually a piece of wall that protrudes up above a flat roof
Roof trusses

Roof joists

Find out more

Visit the website of Architype

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Transcript

Download a transcript of the interview with Lee Fordham.

The Hub

If you’re new to self build and looking for more information, then be sure to check out The Hub. It’s full of great resources, video diaries and support from a community of like-minded self-builders.

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February 26, 2020
HPH186 : Choosing windows for a Passivhaus home – function versus aesthetics
Ben and Kay Adam-Smith have a difference in opinion over which windows to specify for their new build Passivhaus home. While Ben is keen to minimise mullions, transoms and window frames, Kay believes this takes away from the aesthetics of the building.

A visualisation of Ben and Kay’s house

Today’s episode is really a short story about aesthetics. Life would be boring if we all liked the same thing. However, what happens when you’re working with your other half on a self build and you strongly disagree about something? How do you move on? Well we haven’t answered that one yet, but we can share the disagreement and let you know what happens over the course of time!

I (Ben) also feel like I might have said what my wife is saying a few years ago. I believe I’ve grown in my understanding since then and so now my opinion has changed.

Mullions, transoms and window frames

Firstly what are mullions and transoms? Well, they are the structural elements that divide up sections of a window. Mullions are vertical while transoms are horizontal.

There’s no denying that the use of mullions and transoms can make some beautiful windows (as in the stained glass window above, where it’s taken to an extreme).

In the past it was just not possible to manufacture large single pieces of glass and so to achieve a big window, a number of small ones needed to be ‘stitched’ together.

Large glazing is now possible

Probably a window’s most important function is to provide that visibility from one side to the other.

Windows without mullions and transoms therefore do a better job of connecting the inside to the outside (and obviously bring in more light).

As we spend 90% of our time indoors, you could argue that the view out is more important than the aesthetic appearance of the window from the outside.

Large single pane windows are still not the norm

In a country where our period properties make up a large proportion of the housing we live in today, it is hardly surprising that we gravitate towards their features.

That’s perhaps why Kay would like two of three ‘lights’ (subdivisions) in each window.

She also thinks that a lot of houses that use large panes of glass just don’t look right; they look like they need to be sub-divided.

Reducing the amount of glazing in a window affects its performance

The frame is generally the weak point of the window.

Chris Parsons of Parsons + Whittley says: “We want more glass and less frame in the way, because the more glass we have the better the performance of the window. When you start dividing them up with mullions and transoms, you now can’t insulate that part of the frame by wrapping anything around it.”

How much glass is actually in a window?

PHPP models the amount of glass and the amount of frame

Even if a window has a good central pane U-value (a measure of how effective it is as an insulator), it is only referring to the glass. Therefore the Passive House Planning Package (PHPP) requires information on both the amount of glass and the amount of frame in every window. This is the only way to produce an accurate model of the thermal performance.

The ease of opening and closing windows depends of their size

While performance is important when creating a Passivhaus, it must also be balanced with practicality.

When windows get too big, they take a bit more manoeuvring so this could become a valid reason for introducing different lights in certain windows.

Aesthetics will always be a key driver in window choice

There is no doubt that windows with mullions and transoms produce a pretty pattern on the window.

It is also possible to get Passivhaus sash windows, for example. However, for new build, does it make sense to specify sash windows (given all the arguments above)?

This is a choice you’ll have to make . . . and a choice we have to make on our build!

Keep an open mind

This can be a great attitude to anything in life and it’s just the same with architecture.

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August 11, 2017
HPH128 : Closing the performance gap – with Helen Brown from Encraft
Helen Brown from Encraft explains the ‘performance gap’ – what it is, why it happens and how we can avoid it on our projects.

Interview with Helen Brown

Helen has been working at Encraft for nearly 9 years and is currently head of their building physics department. When she started she was interested in renewable energy and micro generation, but she gradually became drawn to low energy construction in new build housing, with Passivhaus being a particular focus.

Encraft are renowned for their research projects

Previous research projects have included:

Warwick Wind Trials – Funded by Pilkington Energy Efficiency Trust and BRE Trust, this looked at the performance of building-mounted micro wind turbines.

Retrofit for the Future – The programme announced by Technology Strategy Board (now Innovate UK) aimed to achieve deep cuts in carbon emissions by retrofitting existing homes.

OWLs – A project using Beattie Passive TCosy system to refurbish a block of 6 flats.

I-LIFE – A current project funded by Innovate UK, to develop an insurance product that would guarantee a home’s energy performance.

A possible future research project, likely to take several years in order to obtain a meaningful and large enough dataset, would be looking at the indoor air quality in homes by considering the effectiveness of different ventilation systems.

‘Performance gap’ is the difference in actual energy consumption compared to the designed intent

The range can be from as little as zero gap, which means the house is performing exactly as intended, to as much as 200% where the house is actually consuming double the energy that was expected.

The main performance gap causes:

As identified by Zero Carbon Hub –
- Quality of workmanship on site
- Quality in the design stages
- Lack of skills, knowledge or understanding either in the design stages or during construction
- Using the wrong materials and products, not following the specification or not having a clear enough specification from the outset
Effective monitoring is required to assess how well a building is performing

Most new buildings aren’t properly monitored to see how well they’re performing, so clients aren’t well informed about how the in-use performance relates back to the design stage targets.

If monitoring is to be performed effectively, it requires someone to review the data and feed the results back to the occupants, builders and designers.

In the case of Encraft’s insurance product idea which sets out to guarantee a home’s energy performance, monitoring would be required in order to verify that the performance targets are being met.

An airtightness test is an easy way to see if a building is performing according to its design intentions

All buildings will have an airtightness target, though not all homes are required to have an airtightness test. In large developments it may be only 10% of them that are tested.

Encraft have found that there is a correlation between airtightness and construction type. In situ concrete is an inherently airtight construction method which seems to consistently meet or exceed its airtightness targets, whereas masonry construction is much more likely to fail the airtightness targets that have been set.

In situ U-value measurements can be compared to performance targets

Testing whether insulation has been well installed can be achieved by measuring the temperature gradient across a wall and calculating its U-value.

Encraft have been looking at this data from the Building Performance Evaluation programme which shows a clear performance gap between the target U-value and the actual measured U-value in the houses that it studied. Their data included Passivhaus and non-Passivhaus developments and found that the performance gap within the Passivhaus subset was much smaller than the performance gap measured across the wider dataset.

‘People factor’ affects the correlation between airtightness and total energy consumption

Encraft have found that when they’ve tried to map airtightness with total energy consumption they’ve found no correlation, which seems like it should be wrong because in terms of building physics there should be a direct correlation.

The reason why there is no correlation is purely down to the building occupants, which drives the variation from home to home in terms of energy use. Encraft would like to be able to somehow normalise the data to eliminate the affects of occupancy, because the people factor is the most complex and difficult to account for, while having the biggest influence on total energy consumption.

Transcript

Download the transcript of the interview with Helen Brown.

Find out more

Visit the website of Encraft

Follow Helen Brown on Twitter

The Hub Update

Something new that we’re going to be offering our members is a quarterly progress call. This will be a private conference call for any members that want to be involved, to provide encouragement, share and resolve challenges, and perhaps even bring in a guest or two to give us some extra inspiration.

The progress call will join our existing offerings, which include our video case study of Long Barrow, monthly modules – the latest of which is about sweat equity – and access to our Facebook group.

The price is just £99 for the year and this is a lock-in price for as long as you stay a member. Find out more.

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May 11, 2016
HPH105 : How Far Should You Go with a Low Energy Retrofit? – with Bob Prewett from Prewett Bizley Architects
Bob Prewett, a director of Prewett Bizley Architects, shares his approach to low energy retrofits and explains why he sets energy targets on a project by project basis.

Interview with Bob Prewett

Prewett Bizley Architects specialises in low energy architecture and Bob has a particular interest in retrofit. He explains that housing is responsible for around 27% of the UK’s carbon emissions, so buildings of all ages and styles have a part to play in terms of energy efficiency.

There is a Distinction Between Retrofit and Renovation

Bob’s partner, Marion Baeli, defines renovation as being smartening things up to make them look good and dealing with the top 3mm of construction. Retrofit on the other hand is about getting under the skin of things and sorting them out at a fundamental, architectural and building physics level.

What to Consider when Commencing a Retrofit Project:
- Get advice at an early stage
- Create a whole house plan which identifies where the energy savings might be, along with the risks associated with tackling them, and how these might be actioned
- Form a clear strategy of how these will be dealt with, either all at once or as stages over an extended period
- Be aware that there is no ‘one size fits all’ when it comes to retrofit.
“It’s not for the faint hearted, either in spirit or in finance”

“Understanding What the Quality of the Building is and Then Designing and Planning Very Carefully to Not Upset That Balance”

Bob is concerned by evidence of the careless nature of works being carried out to some buildings which, with moisture being allowed in and then trapped, can actually be causing damage. He looks at the example set by Germany on the other hand which takes a more considered approach, doing gradual, quality improvements over time, instead of trying to do multiple houses quickly and cheaply.

“Germany still have a confidence about the future and progress and a belief that just doing things well now is an investment for tomorrow. “

“We’re Interested in Taking the Building to Where it’s Going to Sit Happily”

Rather than starting off with a target value in mind, Bob believes that it is important to understand the building as a whole and take it to where it’s going to sit comfortably, and not push it too hard. Some buildings will get to a U-value of better than 0.15 or 15kWh per square metre relatively easily, but for others, such as historic solid wall construction, they are probably not going to want to go there. Bob explains that they are interested in taking the building to where it sits happily, even if those values are a little higher. He would expect most buildings that don’t have insulation or good quality windows to easily achieve a 60% energy reduction, and perhaps even going up to 90% in some cases.

Significant energy savings will be achieved by using a holistic approach to deal with insulation, airtightness, cold bridges, windows, walls, roofs and floors. It is important to understand the building and how these elements interact and work together.

“Some buildings will be predisposed to very high energy savings, some will be predisposed to doing a bit less.”

Be Strategic About What You Purchase if You’re Actively Looking to Retrofit

Bob has purchased a 1960s small terrace house which should leave them with enough money left over to do a good retrofit. He deliberately decided against listed properties and those with planning restrictions as he felt it would be a higher risk approach with energy savings being more difficult to achieve.

They intend to take advantage while the roof on this property is being done to pass brushes between the cavity walls and give them a good clear out before adding cavity wall insulation.

Changes being made to the roof at Bob’s own house

Internal wall insulation and airtightness measures

New light slot

Airtightness results of 0.6

Carefully Consider Your Insulation Options

External Insulation – This can seem like the most simple option. There is potentially very little disruption and you are likely to be able to continue living there while the work is being carried out. You’re cloaking the building, keeping it warm and dry and therefore less likely to suffer moisture problems. The biggest drawback is that it completely transforms the building architecturally, which may not be to yours or the planners liking. In terraced houses you can end up with cold bridges left over through party walls.

Internal Wall Insulation – This has the benefit that it does not have an impact externally so there aren’t the same planning issues as above. There will be far greater disruption inside however and possibly not be in a livable state. The process can be quite slow and be impacted by various pipes, electrics and other services. There are also cold bridge issues when getting to things like window junctions.

Cavity Wall Insulation – If you have cavity walls then filling them can be a good option. Bob however advises caution and not always accepting the claims of the installer that it is suitable for the wall, without following up with further questioning. There may be some situations, such as bad pointing or a coastal property with porous bricks, where it might not be an appropriate choice.

The 80% House was a Defining Project

This was one of Prewett Bizley Architects’ first deep retrofit projects. The client wanted excellence and was prepared to pay to achieve it. During the closing stages of the project, in an extremely hostile winter and before the heating system had been commissioned, Bob would visit the house which maintained a temperature of around 18 degrees. Even though the systems weren’t all running, he was struck by the quality of the environment. Even leaving aside the benefits of energy efficiency, it was the feeling of the house that made a huge and defining impact on him and was the reason why they continue doing these kinds of projects.

80% House

Specific Heat Demand

Year 1 Gas Results

“If you do it really well you just get this amazing quality of environment as a backdrop to our life.”

Find Out More

Transcript

Download a transcript of the interview with Bob Prewett.

International Passive House Days

As Bob Prewett explains, it’s really about the feel of the house and the quality of the environment, which is why the International Passive House Days are the ideal opportunity to experience it for yourself. Each year Passive House residents fling open their doors and invite people in to have a look around and ask questions. This year they will be taking place around the world on 13-15 November 2015. Keep an eye on the International Passive House Association website to find out which buildings near you will be open to view.

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October 27, 2015