Tag: Passivhaus Trust

HPH345: Why is the Passive House Planning Package (PHPP) such a useful tool? – with Sarah Lewis
Sarah Lewis, the Research and Policy Director at the UK Passivhaus Trust and author of PHPP Illustrated, explains what the Passive House Planning Package (PHPP) is and how it is used during the design process.

Interview with Sarah Lewis

Sarah Lewis is the author of PHPP Illustrated and an architect with a wealth of experience when it comes to Passivhaus building. In 2004, whilst at university, Sarah wrote her thesis on the Passivhaus standard at a time when there were no Passivhauses in the UK. Her first job was working for a firm that were beginning to look at building to Passivhaus standard and it was here that she became a consultant on London’s first Passivhaus. From then on, Sarah has worked on an array of Passivhaus projects and now with her current role as the Research and Policy Director at the UK Passivhaus Trust, it is safe to say her knowledge of Passivhaus and the Passive House Planning Package (PHPP) is extensive. In this chat, Sarah guides us through the PHPP, offering tips and tricks that will optimise the user experience and shares a bit about her own retrofit project.

Carrowbreck Meadow by Hanson Barron Smith

PHPP is a part of the quality assurance process

Passivhaus is a whole building approach to construction that aims to deliver healthy, comfortable and energy-efficient buildings. It focuses on high quality construction and through an exacting quality assurance process, provides clear and measured targets. Although there are different targets for new build and retrofit, the process remains the same; it’s about understanding and embracing building physics.

“It’s a really good standard to look at if you just want to have good quality, low energy buildings.”

The Passivhaus Trust has useful resources for both professionals and self-builders

Targeting the Passivhaus standard can seem daunting if you are not familiar with the process, but the Passivhaus Trust has lots of excellent resources to help you:
- The Benefits Guide highlights the advantages of Passivhaus – from reducing our environmental impact, to reducing energy usage/bills and just generally providing a comfortable living environment.
- The How to Build a Passivhaus Guide is aimed at those who have already decided to embark on a Passivhaus project. The guide includes top tips from experts in the construction industry and helps you to avoid the mistakes that are often made on first projects.
- The Passivhaus Designer Course teaches construction professionals to deliver projects to the Passivhaus standard. It includes training in PHPP as well as considerations and methodologies for meeting the standard on site.
PHPP helps you make better predictions about the energy performance of a building

The Passive House Planning Package (PHPP) is a modelling tool that is used in the design process of a Passivhaus. What makes it work so well is that it considers a wide range of variable characteristics which affect heat loss, energy use and internal comfort. This means that the predicted energy use is much, much closer to the real-world performance.

PHPP is an ‘energy balance’ tool

PHPP is not a dynamic modelling tool. Dynamic models might use data points at 30-minute intervals, for example, but it doesn’t mean it would be more accurate than a simplified model. Dynamic modelling’s strength is when you are moving into unknown territory and don’t know whether a simplified model will be accurate.

So PHPP is powerful because it has a simple way to do the energy calculations. It’s based on the average monthly data which allows us to get annual energy demand. All this is quick. The data entry points are reduced to the essentials.

Sarah’s book: PHPP Illustrated is a comprehensive guide to PHPP that aims to break down the steps within the PHPP and provide clarity through her range of diagrams and flowcharts.

In every building there are heat gains and heat losses

All buildings will have heat gains and heat losses at various points throughout the year. In a Passivhaus, these losses are less noticeable because of the higher quality fabric but they will still occur at a lower rate through the walls, the roof, the windows, the ventilation system, etc. It is therefore essential to balance these losses with your heat gains. In a Passivhaus, there are three main categories of heat gain:
- Internal heat gains – This is the energy that is created when people move around the house or use equipment, such as an oven.
- Free heat gains – this is the solar gain, where sunlight passes through windows and creates a warming effect.
- Supplementary heat gain – Once you have calculated the internal heat gains and the free heat gains, whatever is still needed to balance the heat loss becomes the heating demand for the building.
“The number that you often hear in Passivhaus being quoted 15 kilowatt hours per metre squared per annum. So that’s your space heating demand for the building. There’s also an alternative metric, which is the peak heat load, which is 10 watts per metre squared. But the PHPP is constantly reworking that balance.”

It can be useful to visualise the heat loss and heat gain as a seesaw that needs to be balanced. The exact figures and components will be different for every building, so the solutions will need to be specific to your design.

“If you have a bungalow with a huge roof, you’re going to have a lot more losses through the roof than if you had a tower block, which has a very small roof, but much more walls. So you can see how each building will end up with its own bespoke set of losses, and therefore its own bespoke set of gains as well.”

Lots of different ways to use the PHPP

The PHPP is a giant Excel book with many different sheets that you work your way through inputting the specific details of your project. The PHPP has built in assumptions that are based on general data and can help to provide an estimate without having to input into every single section. However, Sarah did highlight that these assumptions are often on the conservative side, and as you begin to input more of your own data, you will see your PHPP improve little by little.

“For example, there’s a default assumption for how much the windows are shaded until you actually have your site set. And then you can work out how much those windows are actually shaded and put that information in.”

In the early stages of your planning using the PHPP you will want to provide information on the fabric of the house: how big the envelope of the building is, the orientation of that building and the size of the roof, walls and floor. From there you can play around adjusting elements, for example adjusting the orientation and seeing the impact that that has on the energy performance.

There are also a wide range of plugins that can supplement the PHPP and help to analyse certain aspects of your design:
- Design PH – A sketch up plugin that allows you to create a fast model which can be exported into the PHPP.
- The AECB PHribbon by Tim Martel – This helps model the embodied carbon of the building.
- Bim2PH – Allows you to export your BIM model into PHPP.
- PassivLink – Lets you export your Revit project data directly into PHPP.
Avoid design by ExCel spreadsheet!

Although PHPP is an excellent tool for predicting and testing the performance of a building, it should not become a replacement for actively making your own design choices.

“The PHPP, as an architect, allows you to go: okay, what if my building was orientated slightly differently? How does that affect the energy balance? Or if I have a big window here? Do I have a summer comfort issue? Or is that really good for my thermal performance of the building? What we don’t want to do, is encourage design by Excel spreadsheet. People should be using their design intelligence, first and foremost, they need to make those intelligent design choices.”

Form factor, glazing ratios, complexity and orientation will all have a massive impact on a project and these can be optimised early in the design process.

“A common mistake is to use a model and then just tweak the entries. For example, window sizes, just to get the desired number to that 15. So while yes, of course, you could just increase your free gains, solar gains, in this case, by making your window bigger and bigger and bigger. You need to be smart and think about summer comfort, embodied carbon usability, and other things.”

As more Passivhaus projects have been delivered around the UK the key learning around window design is to focus on excellent daylighting, rather than maximum solar gains (which can lead to summer comfort issues).

PHPP gives us a ‘whole picture’ of space heating, energy use and delivery

The bulk of the PHPP looks at the form factor, airtightness, insulation, windows, ventilation system and orientation of the building. All of this information combined will provide you with the space heating demand or cooling demand of the building. Then within this, the PHPP goes further than the general UK standards and metrics by looking at both regulated and unregulated energy. In the UK this is referred to as the EUI (Energy Use Intensity) which aims to look at the whole picture of energy use. This takes into account all the heating and cooling systems, the pumps, the lighting, the electrical equipment/plug loads, all the cooking that’s happening in the house and all the hot water being used. All of these combined make up the EUI, which provides the overall energy performance of house.

PHPP includes where the energy comes from

PHPP is not only concerned with the energy that is used in the building, but also the energy that is created and delivered to the building. This includes all the storage losses and distribution losses of transporting a kilowatt of energy from a wind turbine or solar panels, into your building (Primary Energy Renewable). All of these combined create a very comprehensive picture of how energy flows around the building, including where it is generated and where it is lost.

The PHPP looks at components in more detail than standard UK metrics

Take the example of windows. Manufacturers will provide the U value of their windows which measures how effective the overall product is as an insulator. This measurement is not enough for the PHPP because windows are made from a range of different materials. In order to get an accurate understanding of the window’s overall performance, it needs to know the performance of each material used in the window. Manufacturers who sell Passivhaus rated windows will often have this data available, even for products which aren’t certified, but it can sometimes to be difficult to get the necessary data from suppliers who are not used to working on Passivhaus projects. Heat pumps can also be difficult because you need to input a variety of test points both externally and internally, it has been challenging to get the enough information for the PHPP to accept it. However, Sarah believes this is changing and that the more Passivhauses that are built in the UK, the more accessible this information will become.

PHPP can be used for a quick check

People who are experienced with PHPP can make a mock-up in a couple of hours, especially if they are also familiar with the project. One way to upskill is on the Passivhaus Designer Course where you will learn to use the PHPP tool over a couple of days. Because the system is based in Excel, which is a familiar software for most of us, once you have learnt how to input data, it isn’t that difficult to use. It is very common for designers to tailor the process and create their own base PHPP, which has all the values of the construction systems they usually work with already pre-programmed.

“It makes it a bit quicker the next time around, maybe your favourite Windows already input, or the air source heat pump you like working with. All these things you can put into the PHPP and then use for future projects”

Your PHPP can provide a lot of useful information that you can take away

Because there are a lot of people who use the PHPP, there have been number of different plugins developed to help you get the most out of the software and analyse the data it provides.
- The Passivhaus Trust Summer Comfort plug in assesses your PHPP and creates a summary of anything that could be a point of risk, for example, a large temperature swing over the course of a single day. The plug in would then ask for a justification of why this is happening and if there is an adequate control strategy. By highlighting these areas, it helps to minimise an oversight in design that could effect the performance of the building.
- The DeltaQ plug in analyses your data and determines whether your building will comply with the RIBA 2030 challenge and the LETI climate emergency design guide targets. This therefore aligns the building performance with UK metrics rather than just the Passivhaus specific ones.
- There is also a section of the PHPP which can analyse the data to calculate an estimate of the running costs for your Passivhaus.
PHPP is a core principle of Passivhaus design

Completing the PHPP is an essential step in creating a Passivhaus.

Sarah says that there is a common misconception that Passivhaus principles only refer to the fabric characteristics of the building such as super insulation, triple-glazed windows, MVHR and so forth. However, these alone do not create a Passivhaus. The quality assurance comes from the certification process and PHPP is a big part of this.

There must also be attention to detail on site, otherwise we may not close the performance gap as much as we expect to.

PHPP can be used by anyone!

You don’t necessarily need to work with an architecture firm that is experienced in Passivhaus design. The PHPP should be easy enough for any architect to use and its always great to get more consultants to come on board.

“I would certainly say that if you’ve got an architecture team or consultant team who haven’t worked with it before, it’s something where the Passivhaus certifiers can bring a lot of value. So we always recommend that the certifiers are appointed somewhere around RIBA stage two or maybe the beginning of RIBA stage three once you really understand what the building is going to be so the certifiers have something concrete to price. At that point, they can come on board, they can do design checks on the PHPP to really highlight if there’s been any early errors or omissions and then they can do construction assistance… And then obviously, they’re doing the certification at the end as well. So they can really help if a project team are new to Passivhaus.”

However, Sarah also highlights that the PHPP isn’t just exclusive to architects and that if you are keen to give it a go yourself, the manual and wealth of other supporting documents can help you along in that process.

Looking back on one of our previous episodes, Mark Tiramani undertook the PHPP process himself.

“I think anyone can do it. The very first PHPP I ever did, I had to just use the manual and fill it out because there was no English courses at that point. I was self taught in that sense. I would say it took me a bit longer to fill out. You have to be quite experienced to be able to do in a couple of hours. And I think the main thing is orientating yourself. There’s a lot of spreadsheets to work through. But the manual comes with a flow diagram. And you can follow through the sheet by sheet and you can fill out everything. But it is definitely helpful to have gone on a course before trying to delve in. I didn’t have that luxury when I did my first PHPP, which is why I ended up writing the book.”

The PHPP has had a few changes over the years

In 2016, the formula for how the Primary Energy was calculated was changed, which also allowed the Passivhaus Institute to bring in different classifications: Classic, Plus and Premium. These classifications are based on both the usage and generation of primary energy.

“So rather than just standard Passivhaus, it brought in Plus and Premium, which were ways to acknowledge projects which are generating energy, so renewables as well as being very energy efficient.”

Primary energy hadn’t been a massive focus in UK Passivhaus practices and this change to the PHPP helped formalise a shift in mentality towards renewable energy generation and promoted including these aspects in the designs. Before, it could have been considered acceptable to fit a gas boiler into a Passivhaus, but this change shifted the intention of Passivhaus to also work towards a future grid supplied primarily by renewable energy. Apart from this, the majority of other changes have only been minor tweaks or improvements to the interface, to make it more user friendly.

Sarah’s Retrofit Project

In 2018, Sarah bought an ex-local authority, 1950s terraced house in East Lothian, Scotland. She has since been renovating the house with the aim of ultimately getting it to reach EnerPHit standard.

“I would probably say, we had exchanged and had the keys for about a day before I got into the house, measured everything and started inputting it into PHPP. The main reason for that is I wanted to see what the heat loss from the building was, so that I could plan what we’re going to do to improve the building. So that’s one of the ways that you can use PHPP in a retrofit, you model the existing building and then you can see where all the heat loss is, and you can see where you should focus your money to save that energy.”

Sarah’s retrofit has not quite reached EnerPHit standard yet as it does not meet the airtightness requirement. This is one of the largest challenges in a retrofit project and Sarah says that it is the roof of her project that is not currently up to spec.

“There’s some air leakage in the roof, which is just really difficult. We didn’t replace the roof so it was just really difficult for us to address all of that. I think when the roof comes up for its replacement, so it’s a 1950s house, but might have another 20 years in it, at that point, I hope we can get the airtightness down.”

For Sarah, retrofits can really challenge you to think creatively with your design because there are so many constraints for you to work within. A challenge arose in her project when it came to insulate the floor, as to add insulation to the floor would reduce the clearance height of the room. Sarah worked around this by taking the ceiling right back to gain some extra headroom, which in turn exposed the beams, adding a lovely design feature to the room. This shows that with a creative mindset, constraints can be turned into intentional design choices that add character and detail to a home.

“You can plan out a retrofit and you can do that over a few years or you could do over a few decades”

Create a ‘long term’ retrofit plan for your home

So long as we have a comprehensive, well thought through retrofit plan it doesn’t all have to be completed all at once. PHPP could be used to help us break down a retrofit into steps.

“The EnerPHit retrofit plan encourages you to design all of that upfront, and it almost sits as a kind of retrofit passport with your building, which can be passed on to future owners if you move or if it’s an asset, which is owned by like a local authority, or a council, or housing association or someone, they can also sit with that asset as people in the company change. And then people always know what’s the next plan for any particular building.”

This procedure could be revolutionary in the UK and PHPP will be a really useful tool to analyse the existing housing stock and work out the best way to get as many houses as possible to higher standards.

“Going for a full EnerPHit retrofit is probably not the right solution for all buildings. We’ve got a huge job in the UK to retrofit our existing stock and we need to take the easy buildings and go as far as we can. And then we need to recognise that some buildings will never get to go that far and planning out a lesser retrofit design for those projects is also really important and can also be done in a really robust tool like the PHPP.”

Find out more

Visit the website of the Passivhaus Trust

RIBA Books – PHPP Illustrated

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February 14, 2024
HPH326 : Is it worth upskilling your knowledge of Passivhaus? – with Simon Bell

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

Interview with Simon Bell

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

Copyright HLM Architects

A Passivhaus doesn’t need to be a simple box

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

The panoramic beauty of the site created Passivhaus challenges

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

The value of an architect is to bring a different vision

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

He wanted to be an informed client

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

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

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

Contractor attitude was more important than Passivhaus experience

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

They established a no-blame culture

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

Having a live project helped his understanding of the course

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

Trust in your consultants

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

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

The pandemic presented the biggest challenges

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

Each build presents a learning opportunity

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

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

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Visit the website of HLM Architects

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Transcript

Download a transcript of the interview with Simon Bell

Video of HLM’s Tigh na Croit

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February 1, 2023
HPH280 : A beginner’s guide to the Passivhaus Standard – with Jon Bootland

Chief Executive of the Passivhaus Trust, Jon Bootland, explains the processes and benefits of building your house to the Passivhaus Standard.

Interview with Jon Bootland

When Jon Bootland finished his university degree he began his employment first as a building services designer, and later working on good practice for sustainable low energy buildings, now with nearly 30 years experience. He has also been involved with the Passivhaus Trust since it was formed back in 2010. With initially very slow progress since the first Passivhaus was completed in the UK in 2010, numbers are now increasing rapidly at around 1,200 completed buildings (of which around 200 are individual owner-occupied homes), with another thousand already in the pipeline.

Carrowbreck Meadow – Image copyright Jefferson Smith

There’s nothing hugely complicated about Passivhaus

The origins of Passivhaus come from Germany, where the physicist Wolfgang Feist wanted to find a way of making sure that high performance buildings actually delivered on their claims, and performed the way that they were designed to do.

“It’s all about building physics. There’s nothing hugely complicated about it. It’s just what do we need to do to actually make it work and do what we said it was going to do.”

High in comfort levels, low in energy use

The fundamentals of a Passivhaus are:

Insulation – This is an important part of reducing the energy required to heat the building. A typical Passivhaus might have up to 30cm of insulation, meaning that the walls will be very thick.

The building fabric and airtightness – The other parts of the building will also need to have a very high performance. Windows for example will need to be triple glazed with good quality frames and careful detailing about how they fix together. The airtightness of the building is important with the aim being to stop draughts coming in and heat leaking out.

Ventilation – Because the building is now free of draughts, attention then needs to be paid to how to ventilate it. A mechanical ventilation system is used (MVHR) to bring fresh air into the building, while recovering the heat from the outgoing air.

As well as dealing with keeping the house warm in winter, Passivhaus formulae also look at the sun and other heat sources coming into the building and how the ventilation and insulation can work to keep it cool in the summer.

Old Holloway – Image copyright Juraj Mikurcik

Have a Passivhaus expert in your team

Jon says that building a Passivhaus is harder to do than a normal house, but that doesn’t necessarily mean you have to employ a team of specialists. He would however recommend having someone in your team that does have Passivhaus training, and preferably experience. It doesn’t have to be the builder, but could be the architect or a consultant.

The Passivhaus Planning Package does the calculations

You will need someone who knows what they’re doing to fill in the Passivhaus Planning Package (PHPP) and work out the answers to the calculations with you. It is a tool that takes a holistic approach to making all the elements work together, to make sure you end up with a building that has the performance and comfort that you are looking for.

There are benefits to having certification

PHPP should be used right from the beginning to look at the size and shape of the building, the window locations, balconies or anything else that might penetrate into the building etc. A certifier is able to check what is being put forward and advise on whether what you’re suggesting is actually going to work in the way it is intended.

Without having a certifier on board you will not be able to call it a certified Passivhaus, which does have some value in being able to sell the project. Certification is the best way of ensuring that your building will meet the required standards and provide the comfort and energy performance that you are looking for. If you’re not planning to use a certifier, then Jon recommends ensuring your team of architect, builder and consultants have plenty of Passivhaus experience between them to give you confidence it will perform as intended.

There are health and cost benefits

Jon outlines some of the key benefits of a Passivhaus:

Lower energy bills – The extra insulation and airtightness means less heat is escaping from the house, and therefore less energy is needed to heat it. Typical heating bills for a standard sized Passivhaus might be around £100, compared to several hundred for a non-Passivhaus equivalent.

Health benefits – Jon says there are research projects planned in the next few years looking into this, but there is still plenty of anecdotal evidence from occupants talking about the health benefits of living in a Passivhaus. As well as thermal comfort, the air that comes in can filter out air pollution and pollen, and people have reported improvements in asthma conditions. The mechanical ventilation also reduces moisture levels in the building which prevents condensation and mould.

Some construction methods will be harder than others

Jon says that although you could achieve Passivhaus with any construction type, it will be harder to achieve with brick and block for example than with timber panels. Although it’s possible to do, it will just need to be approached differently.

The extra outlay is money well spent

Jon uses social housing to get comparable benchmarks for how much more a Passivhaus will cost to build over a standard form of construction. Typically the additional cost of building a Passivhaus will be around 4-8% higher. Jon says that probably half of that is just on better quality building, which actually should be applied to all new buildings anyway, regardless of whether they’re Passivhaus.

So on a £200,000 – £400,000 build cost, that’s likely to add on just £8,000 – £16,000 extra.

“So, say you’re going to get a much better quality building that will make you more comfortable, more healthy and will perform better for 50, 100 years or more, it’s a very small amount of money in my book and it’s a much better way to spend your money than on a super flashy designer kitchen.”

There are ways to keep costs down

The shape and form of your building is crucial in keeping the costs down. Adding on multiple wings, outlying parts, differing floor levels, balconies additional roofs, lots of corners and odd shapes, will all make it more difficult to make a Passivhaus work, and will be more costly.

Jon wouldn’t recommend everyone try and build a square box as being the answer, but the closer you aim to a square box shape the easier it is to achieve Passivhaus.

Another way to keep costs down is to bring in your Passivhaus expert as early as possible. Don’t wait for the design to be finished and then call them in to do the calculations, but involve them at the design stages to help develop the building shape, window sizes and locations etc.

Multiple heating sources are not needed!

Jon explains that it can be challenging mentally to think of a house not needing multiple heat sources in it, but really they’re not needed.

Commonly though, people might put a radiator by the front door so that as you walk in there is a perception of extra warmth, while your body adjusts from the cold outside to the comfortable 20-21 degrees inside. A heated towel rail in a bathroom is also quite popular.

The design needs to minimise overheating risk

With homes becoming more energy efficient, the risk of overheating in the summer is becoming more significant and has to be planned for.

The main source of heat coming into the house in the summer will be from the sun, mostly in the late afternoon and evening. To stop the heat coming in without losing the views, Passivhaus buildings will often have some kind of shading or overhang on the west or south facing walls which keeps out the heat until later in the evening when the temperature drops.

There are also other heat sources to take into account such as the occupants and appliances, which heat the house slowly during the day. This data also feeds into PHPP to calculate how much heat will need to be taken out of the building to keep it cool. This can be done using the mechanical ventilation, or by opening the windows, particularly overnight. The temperature fluctuation in a Passivhaus will only be a few degrees, compared to 10-15 degrees in other houses.

“But the extra insulation and the extra performance of the windows, the doors and so on helps in the summer. Just as much as it helps in winter in keeping the heat in, in the summer it keeps the hot air out.”

The Passivhaus Trust oversees the standard in the UK

The standard was invented and developed in Germany, but in the UK it is looked after by the Passivhaus Trust. Their job is to look at how to apply and make the Passivhaus work in the UK, with our differing weather patterns and culture. Jon gives an example of these different considerations being parts of Scotland, where people don’t want to open their windows for night-time cooling because of midges coming in, so different approaches have to be developed.

The second aspect to their work is promote the adoption of the standard, by engaging with central government, local authorities and trying to get people on board.

Jon accepts that while it’s a great standard it’s not perfect, so the third part of their work is carrying out research on specific aspects that can be changed and improved over time.

There are different levels of Passivhaus standard

There are two main standards: Passivhaus Classic for new build and EnerPHit for refurbishment. The criteria for achieving EnerPHit are slightly less stringent because it is that much trickier to do a retrofit. Certain aspects of the building are fixed and can’t be changed, so an allowance is made that if you can’t change those things you can still get Passivhaus.

The Barrel Store – an EnerPHit Standard youth hostel. Image copyright Mac McClure

In addition there are also two new standards: Passivhaus Plus and Passivhaus Premium, which are effectively the Passivhaus Classic but with renewables. Passivhaus Plus is where the energy generated by the renewables will exceed the energy demand of the house and reach zero carbon. So the energy generated will be equal to or more than your energy used during the year.

Passivhaus Premium takes that a step further with enough renewables to create an energy positive house, so you’re generating more than you need and reclaiming money back from the grid.

PHPP can be used to calculate embodied energy

Within the planning tool they are now looking at add-ons which consider the embodied energy of the materials that you use and form part of the Passivhaus calculations. This will benefit people who are keen to use natural materials or who are just interested in understanding how much embodied energy there is. Jon stresses it is not a requirement for achieving the standard, it’s just developing the capacity to do it for those that would like it.

Find out more

Visit the Passivhaus Trust website, and learn more about their Passivhaus goes Personal campaign

Transcript

Download a transcript of the interview with Jon Bootland.

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March 4, 2020
HPH246 : Self build mortgages that promote sustainable living – with Paul Ellis from Ecology Building Society

Paul Ellis, Chief Executive of Ecology Building Society, explains their approach to mortgages that reward energy efficiency and sustainability.

Interview with Paul Ellis

Paul Ellis was an early investing member back in 1981 when Ecology Building Society was formed, and has been Chief Executive since 1995.

Founding members had a shared interest in environmental causes

The ten founders had met through their involvement with the Ecology Party; the forerunner of the Green Party, and had a shared interest in self-sufficiency and low-impact living.

They were individuals looking to buy properties to renovate to reasonable energy efficiency standards, and without doing too much work. What they found was lenders were very restrictive and uninterested in providing support. They would demand certain works such as ripping out stone floors and putting in damp-proof courses that weren’t really needed, but that they felt would minimise their risk.

“So, they’d often say they’d lend the money, but only once all the work is done, which wasn’t the point because everybody wanted to do their own work, be self-sufficient and learn building skills. So, they would be forced immediately into trying to get others to do the work and they were probably not going to have those kinds of funds available.
So, the building society was setup to really encourage that ability to take properties and bring them back into good use to a reasonable standard, but not to provide expensive kitchens.”

They are the youngest building society

At the time they decided to set up a building society, there hadn’t been another done for quite a while beforehand, and they are still the youngest in the country. Paul believes a change in the regulations is the reason for this. In 1981 they only needed ten investors with a maximum of £5,000 to actually start the building society. The authorities caught wind of it and changed the rules to increase that amount. Luckily they managed to get the paperwork signed with five minutes to spare before the rules came into enforcement!

Building their own premises seemed a natural step

With the business growing it was necessary to find new premises, and after considering renovation they decided that building their own offices would be the best way forward. It could incorporate some of the techniques they were asking their borrowers to consider, and be a bit of a test to see what the issues were. And while the building has largely been successful, there are certain things they would now do differently.

The building dates back to 2003, before Passivhaus was well-known in the UK. If they were to do it again, or when they extend it, they would use Passivhaus concepts.

Paul says they were fortunate at the time to have the advice of eminent energy efficiency experts, although they had to compromise some of the ideas slightly to create a warm, welcoming space to live and work in.

There are two distinct elements to the building. One part focuses on long-term energy use, with large amounts of concrete but highly insulated and built to a good level of airtightness.

The meeting room area of the building was entirely constructed from straw bales, with a clay plaster render on the inside. Some of their members even came along to help with the construction while learning the techniques of building with straw.

Throughout the building they have tried to make as much use as they can of recycled, reclaimed and other materials that have low embodied energy.

Get early advice

Paul would encourage anyone at the beginning of their self build journey to take a look at their website or give them a call to discuss their plans. While they wouldn’t immediately be able to give approval, they might comment on their ideas of budget and whether they think it could be viable for what is being proposed.

In some cases they can be communicating with people for years who haven’t yet found their plot, but the majority of time people will already have a deposit and a plot.

“For us to make a decision, we have to be sure that there is something here which is going to work in terms of energy efficiency or wider environmental considerations, and so it’s hard for us at the outset to give more than a rough picture of what we can contemplate because we don’t know the nature of the building.
For us as a lender, the actual nature of the building, the finished product, is quite important to us. For other lenders, it would be more of a focus on the finances. For us, it’s what the building will achieve.”

During initial discussions they would ask about the techniques and materials the borrower plans to use, and take a view on whether or not they think it’s a project that will work, by getting an understanding of whether the individuals understand those techniques and whether it will work in practice against their budget.

Paul says that a good development has been more borrowers these days employing architects who have a strong knowledge of these techniques.

Payment stages are flexible

Typically, their projects will have staged payments, although they aren’t set at a predetermined, fixed stage. Instead the borrower contacts them to say they’ve done a certain amount of work, at which time they will get it valued and release money against that.

“That introduces a certain level of flexibility. Obviously, internally, we do track and monitor the progress of the building to make sure that it’s remaining on track. And that’s because we’re looking after our members’ money. We’re making sure they’re secure. But within that, we can be quite flexible when those releases will happen to suit the circumstances of the borrower. And that might be that they’re tying into other financial resources as well. They might have monies that are not quite available or whatever, so we’ll take that into account.”

Understand your plot

Paul advises buyers to know their site well, to avoid unexpected costs and delays. Understanding issues with boundaries, hidden structures and general groundworks will be an advantage.

He also recommends a budget contingency of ten percent, which is something they will look for in the costings.

Renovation projects are encouraged

Ecology have a varied client base, but not too many first-time buyers. Those they do get tend to have been gifted a plot or had help with their funding, and more commonly are carrying out renovations.

While Ecology like to support renovation projects, which was mostly their emphasis in the early days, the tendency now has been for more self builds.

“And you can see why, in some respects, because there’s been a lot of development in green building techniques, in products, and you can start with a blank sheet and design in energy efficiency from the start.”

From an environmental point of view, Paul sees the need to improve the existing housing stock. They are working with companies, cooperatives and government departments to find a way they can create models to encourage more people into taking on renovations and retrofits, by providing systems of support and information, and making it easier for people to engage.

Their self build clients tend to already be fairly well informed and have carried out research and engaged with organisations like the Passivhaus Trust or AECB. And for those less well versed they might question certain aspects, for example, whether they need all the renewables when they haven’t really considered insulation.

Another form of construction they are keen to encourage are kit homes that are semi-constructed off-site. They often come with some guarantee of energy efficiency and avoid many of the pitfalls that can occur on site.

Financial benefits for the most energy efficient

Ecology provide discounts for the full term of the mortgage, based on the property’s standard of energy efficiency upon completion, with Passivhaus giving the maximum discount.

Progress is being made

Paul believes in their early days they were lone pioneers, but gradually now they are seeing advances in the green building components industry, with exciting new products and more companies trying to do the right thing.

“So, it’s almost like despite the drift of government policy, business, companies, individuals, cooperatives are leading the way on this because they know it’s not only good for the planet, it’s good for society, it’s creating sustainable jobs, and it is beginning to happen.”

He is also seeing a push on the Green Finance Initiative, looking at ways to increase the flow of funds to green investment products.

Something that Ecology are doing to assist with this is they’re working on a project to create an energy efficiency mortgage model that would be available across Europe. It would enable more mainstream organisations to create preferential financing for mortgages on properties that are making a difference to our carbon footprint.

Find out more

Visit the website of Ecology Building Society

Follow Ecology on Twitter

Transcript

Download a transcript of the interview with Paul Ellis.

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April 17, 2019
HPH212 : What challenges does an ‘L’ shape Passivhaus present? – with John Fenwick
John Fenwick discusses the challenges of building his award-winning Passivhaus with an atypical form.

Interview with John Fenwick

It was around eight years ago that John and Jeanette Fenwick sold their house in order to retire to the West Highlands of Scotland. The idea for a self build only came about when they couldn’t find anything on the market that they wanted to move into. The large plot they bought looks out onto Ben Wyvis and was originally crofting land that was overgrown with birch, and quite boggy in places.

Their intention had been to build a kit home but weren’t sure how they would get a builder for it or how to take it to planning. It wasn’t until they attended a Housing Expo in Inverness in 2010 that they came across Passivhaus buildings. After speaking with the consultant there, and later the architect that had designed the Passivhaus Terrace for the Expo, they decided that this would be the route forward.

A modern interpretation of a traditional style

Key to their plans for Tigh na Croit was a single storey dwelling that would reflect the traditional steading style of building in the area. The ‘L’ shape of the design came naturally with one length of the house incorporating daytime accommodation and the other length housing the bedrooms.

Getting the ventilation strategy right was the biggest challenge

John explains that ideally an MVHR unit would be at the centre of a house so that the system is balanced, with everywhere being treated equally when it comes to ventilation, heat recovery and heat distribution. In Tigh na Croit, the ventilation equipment is at the corner of the ‘L’. John has installed sensors so is aware of the temperature differential between the recovered heat that is distributed closest to the ventilation equipment (30-35 degrees), and those rooms at either end of the building (23-24 degrees). To get through the harsh winters the living room at one end of the ‘L’ has a Passivhaus certified stove, and the main bedroom at the other end of the house has a heated mirror-like far infrared panel. Together with a water-based post heater supplied by an air-source heat pump, they provide the main heating to the house. Additionally the air-source heating circuit powers three small towel rails in the bathrooms.

Tigh na Croit uses a Passive Wall system of construction

OSB panels are pre-filled with insulation, pre-membraned and put together like a timber frame to create the airtight envelope. The finish gives clean lines inside the house and with three double-height spaces within the floor area they were able to achieve an attractive effect using the closed panels for the walls and for the roof.

Frequent site visits would have been advantageous

Building in the Highlands anyway was a big challenge with there not being a great many builders to choose from, and the fixed-price contract deterred a few from tendering. One local company agreed to take on the contract and sub-contracted out many of the trades.

As they were living 300 miles away, they employed the architect on a traditional contract where he would visit the site once a month.

“We thought once a month would be sufficient, but clearly, when you’re building a house using principles perhaps not familiar to the builder, I think being on site for the build would have been hugely advantageous. The build wasn’t without its issues, let us say.”

Being able to communicate with the builder and know which days he had been on site was very difficult to monitor from such a distance away. With the builder invoicing monthly, and John only able to visit every six weeks or so, he would sometimes arrive wondering what work had actually been carried out since his last visit.

The contractor’s lack of attention to detail and knowledge of what was required to achieve the Passivhaus standard meant there were some frustrating delays.

“So, the first air test was actually a waste of time apart from telling us really that the builder hadn’t understood that attention to detail as far as taping and stuff like that, was absolutely paramount.”

They found a fist-sized hole where air was getting in and in areas where airtight foam had been specified, the builder had used standard building foam because he hadn’t been able to get the correct one at the local builders’ merchants.

The harsh climate is a challenge even for a Passivhaus

John and his wife did debate whether or not to install underfloor heating, and believe they made the right decision not to go ahead with it. Being a Passivhaus would have a beneficial effect in that the underfloor heating wouldn’t be worked as hard as in a standard home, but the problems arise when the house is suddenly flooded with sunshine and can become difficult to cool down, as underfloor heating takes a few days for the effects to wear off.

Even being a Passivhaus there are times when the heating needs to have a bit of a boost. This is particularly the case if the house hasn’t been occupied for a period of time. Generally though they manage to maintain a temperature of around 18 degrees which, without drafts, they find comfortably warm.

Perhaps the one thing they would change if they did it again would be their bedroom window. It’s a very large picture window that is triple-glazed, but despite the quoted u-values, isn’t as insulated as a wall would be so does feel cool and will inevitably lead to a temperature decrease in the room. Finding blinds to fit it has also been one of the biggest challenges they’ve faced!

Copyright HLM Architects

John thinks the house naturally settles at a temperature of around 15 degrees warmer than outside.

“So, if it’s minus eight outside and you’ve got a mechanical ventilation running, the air that’s coming in is at minus eight whatever happens. You can put a defroster on the system to make sure that the whole system doesn’t freeze up, but you’ve still got pretty cold air actually going into the mechanical unit. Five degrees is often the air going in, and you’ve only got so much heat from the extracted air mixing with that. So, the colder it is outside, the more challenging it is for the house full stop.”

John has experimented with switching the MVHR unit off overnight in the winter and found that it doesn’t make a great deal of difference.

“You have to be aware that if the temperature goes up a few degrees outside, you do notice the difference inside. So, the house reacts to the temperature outside, there’s no doubt about it. And where we are, the challenges are pretty extreme really.”

Find out more

Visit the website of HLM Architects.

Transcript

Download a transcript of the interview with John Fenwick.

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April 4, 2018
HPH111 : How value engineering could benefit a house build – with Nick Grant from Elemental Solutions
Nick Grant of Elemental Solutions explains what is meant by value engineering and how it can be used in the house building process.

Interview with Nick Grant

Nick was a Trustee of the AECB and is Technical Director of the Passivhaus Trust. He is a sustainable building consultant with a background in engineering and, stemming from a childhood ‘make do and mend’ mentality, a lifelong passion for doing more with less.

Giving maximum value through engineering

As an engineer, one of the modules that most inspired Nick was one about value engineering.

Value is defined by Nick as being performance divided by cost. If you maximise performance, or reduce cost, it increases value.

Nick cites as an example the trend of smartphones having fewer buttons than ever before. An iPhone has been very value engineered in that “it manages to deliver a lot by doing very little and it takes a lot of effort to get to that”.

In engineering it’s an incredibly positive thing and what is strived for, however when Nick started working in the construction industry he discovered that people were using the term to mean cost-cutting in a negative sense:

“So I went from this thing being something I thought was inherently a great thing and a real challenge and exciting, and for me defined really good design, to this thing that people say “it’s been value engineered, they’ve ruined my project, they value engineered it.”

Value engineering has to happen at the beginning of a project

It needs to happen right at the start when the design is being developed. Decisions about the size, shape, orientation, etc all have an impact on the final value, cost and challenges that are going to arise. If the correct steps haven’t been taken at the beginning then it is likely that contracts in the tender will come back over budget, resulting in a cost-cutting exercise which will inevitably see the removal of features that you liked about the design.

Dempsey Decourcy Architects – Vowchurch

It should be integrated in the house building process

Nick feels that everything he does is value engineering, but that people can be reluctant to pay for something which leaves them feeling like they’re actually getting less. It may be that they’ve been told about something which they didn’t need to do, thus saving money, but they haven’t actually got anything tangible for it.

Typically in architecture it tends to be cost cutting and might be carried out by a Quantity Surveyor. Nick feels however that it should be completely integrated, with everyone on board and led by the lead designer. There should be encouragement, whether for the structural engineer, landscape architect, energy consultant etc, to find better, cheaper and easier ways of doing things.

Example of VE interior detail – polished concrete floor / foundations

Example of VE interior detail – Kitchen cupboards made of shuttering ply and surplus stainless steel washers

Having constraints on a project can be a positive

Nick says that rather than having to make compromises if they’ve run out of time or budget, it should be the case that if the correct work has been put in during the process they should be able to come to something “where it kind of all works.”

Having constraints can in some ways make the job easier. There can be fewer choices needing to be made and subsequently less things that they can get wrong. It can free the designer to focus on other things as well.

“So the more constraints we have, I think as a designer I take that as, I like that. So if we’ve got a very small budget, limited palate of materials, I quite like the challenge of that.”

By establishing a budget early on you can immediately realise that there are things that might not need to be considered, such as the indoor swimming pool and fancy finishes!

Dempsey Decourcy Architects – Cae Duff

“So you’ve got to do the value engineering, you’ve got to find a better way of doing things, find more clever materials, but you’ve got to also set a budget and then work to that budget. Otherwise everything will just expand to meet it.”

You can do things cheaply, quickly or well: you can’t do all three!

Nick and his partner designed and built their own home, blowing their original £30,000 budget and spending £40,000! While they like to think they did it well and cheaply, it did take them a long time to complete. They took inspiration from Christopher Alexander’s book A Pattern Language, but by doing that they did end up with a house that has a very complex form (a form factor of around 5) and which was a lot more time consuming to build.

It’s not easy to do simple!

By working on repeat projects Nick has been able to invest the time into working out details that appear to be simple, but if they were that easy everyone would be doing them! The process can evolve very slowly but benefits are reaped by the experience gained, thus making things easier on the next projects.

Dempsey Decourcy Architects – Cae Duff

Give a great deal of thought about the number and function of windows being used

Nick is currently doing some work on overheating for the Passivhaus Trust. He explains that in our climate we tend to want to let the sunlight in and aren’t used to going out and putting the shutters down, whereas in warmer climes this is something people do automatically. It therefore shouldn’t be a surprise when we return home and find them overheating!

So firstly it’s important to have enough glass for views and letting daylight in, but without having too much.

Glazing is expensive so, coming back to value engineering, make the window do as much work for you as possible. Thinking of function, if there are windows that can’t easily be accessed and opened, then consider a fixed rather than openable one, which typically you could pay 30% less for.

Nick gives this example of his own window behind the kitchen sink which they can’t easily reach to open, and suggests that actually a fixed, single frame view would probably have been better.

Have a guess what percentage of glass there is to frame, and find out the answer in the podcast. The answer may surprise you!

Ensure also that if your windows are to open, that they open enough to get the airflows. Often they open in a restricted reveal which doesn’t allow enough air in. Evolving over many buildings, Nick has learned to step the reveals in a way that when the window is tilted it still allows good airflow. It’s this repetition, and going back to review previous jobs, that is critical to learning and making improvements next time.

Decide what matters and work to your budget

Deciding what matters and working to your budget is Nick’s key piece of advice.

“Everything isn’t possible. But again that shouldn’t mean there’s a compromise necessarily. What you end up with you shouldn’t be thinking oh I really miss the little Victorian fake windows, you should think oh thank God I didn’t do that!”

Find out more

Follow Nick Grant on Twitter

Find out more about Elemental Solutions

View Nick’s presentation: Value Engineering, What’s not to love?

Find out more about Charles Grylls and Dempsey Decourcy Architects

Transcript

Download a transcript of the interview with Nick Grant.

Inquiry into the Quality of New Build Housing in England

Towards the end of last year, Ben was part of a panel at the Inquiry into the Quality of New Build Housing in England, at the Houses of Parliament. Presenting to a handful of politicians and construction professionals, those contributing included:
- Phil Waller, who has previously worked for a major house builder. His opinion was that they could be doing much better, and he has set up a website to try and advise potential purchasers what they should be looking for if they’re intending to buy from a developer.
- Geoff Peter from Wingrove Law is a solicitor who represents owners of new builds who have ongoing issues with their homes.
We know what a lot of the issues are and a lot of good questions were being asked, but it just comes down to whether anything will actually get done.

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January 13, 2016