Tag: PHPP

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

Transcript

HPH345-Transcript-Sarah-Lewis Download

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February 14, 2024
HPH332 : How accurate are Energy Performance Certificates (EPCs)? – with Tom Gwilliam
Tom Gwilliam explains what Energy Performance Certificates (EPCs) are, how they are created and why they are unlikely to be a useful measure of how energy efficient a building is.

Interview with Tom Gwilliam

Tom is a sustainability consultant at Etude, with a background in structural engineering, energy assessment and whole life carbon analysis. This episode was inspired by a previous episode, Should we celebrate architecture that performs poorly?, which relied heavily on EPC data.

EPCs are a legal requirement when selling or renting a home

Energy Performance Certificates give a rating between A and G, and a number between one and 100, of how energy efficient the home is. This is the main output, but there’s also other information about what you might do with the home and how the home is performing at the moment.

A domestic energy assessor carries out a SAP assessment on new-builds, or an on-construction domestic energy assessor carries out a ‘reduced data’ SAP (RdSAP) assessment on an existing building. The two are different, but both rely on entering information into a computer model, which outputs the EPC.

SAP assessments make assumptions about how a building operates

SAP stands for the Standard Assessment Procedure. It measures heat loss, domestic hot water use, energy associated with pumps and fans, and the energy associated with lighting. It also estimates what people might use for appliances (‘unregulated energy’, because it varies by number of occupants and their behaviour).

The assessment makes various assumptions and boils them down to a single number for total energy use in kilowatt hours. On top of that, it superimposes carbon emissions, primary energy, and other metrics used for building regulations compliance.

EPCs also measure the cost of operating the building

The EPC process takes the total energy figure and puts a cost on it for the resident. But the accuracy of that cost all depends on the accuracy of the assumptions made earlier in the calculation.

SAP is used to drive policy decisions

There’s an aspiration for every property in the UK to be at least EPC C by 2035. Part of the problem is that studies show the EPC rating doesn’t correlate well with the energy use of a building. You’d expect that moving from A to G would see increased energy use, but there isn’t much change in general.

Even if all homes are a C by 2035, we’re unlikely to see much change in energy use in buildings. We’ll still have high energy homes and it will be too late in 2035. There’s a real incentivisation issue, and no strong grasp of how to improve buildings through the EPC process.

Five different assessors would probably come up with five different EPCs

Another major problem with EPCs is consistency – there is none. The EPC industry is not well-moderated, and assessors are paid quite poorly. Plus, there’s pressure at government level from house builders not to increase the cost of assessments and EPCs.

The process relies on a person to interpret a physical characteristic of a building. People might measure things differently or inaccurately, or even completely wrong. Assessors also have to make a judgment on how old a building is, and how it’s constructed. They don’t have the time or money to investigate what’s actually in the walls, so a lot of their work is guessing and being as quick as they can.

There’s proven evidence of getting an EPC for a new-build house, then sending an RdSAP assessor to do an assessment the next day, and the two producing completely different results.

Example of an Energy Performance Certificate

EPCs aren’t really about your home, even though they look like it

An EPC is presented in a way that makes you think that it’s about your home, but it isn’t. If you had identical buildings in Cornwall and Durham, and carried out identical assessments, you’d get the same EPC. But we know the space heating demands for buildings in those two locations will be very different. That fundamentally undermines the EPC process.

SAP doesn’t have the ‘as built’ check that Passivhaus does

It’s possible to game the system, particularly with new-builds. SAP assessors don’t get paid well and they have to take the word of the developer or people on site. Assessors don’t have the required understanding of how a building is going to perform in reality. They don’t see all the detail, so they have to simplify things and make assumptions.

When you have that disconnect between what’s happening in reality and what the computer model says, there’s a big incentive for developers to be unrealistic with what they’re saying. By contrast, two people carry out the Passivhaus process. There’s a designer and a certifier, and a peer review process going on all the time. It makes it a better-quality process.

Simply adding a requirement for the SAP assessor to go to site at the end of construction would make a big difference.

Thermal bridging is a particular issue

Thermal bridging is a big source of heat loss in new-build properties. SAP has categories for thermal bridges, but they don’t cover everything. It’s hard to have a 3D understanding of a building when working off plans, so if you’re not on site and seeing where thermal bridges are occurring then they’re not getting picked up at all. There’s no way of quality checking that process because nobody is overseeing the SAP assessor.

There are lots of assumptions about heating system performance

The technology behind boilers and, in particular, heat pumps has lots of nuances. SAP doesn’t require the level of detail that influences whether heat pumps perform really efficiently or very poorly. The model doesn’t ask for a lot of information about the system, so it can only make a simplified judgement about how it will perform.

A way to improve it would be to break the system down into more component parts, understand each part better, and reflect that in the calculation with evidence. If we’re going to shift to low carbon buildings, SAP assessments should reflect a need for more information and understanding to incentivise developers as part of the building regulations compliance process.

Some people advocate for adopting Passivhaus

It’s a proven system. With Passivhaus and PHPP, there’s a clear link between designed on-paper performance and in-use performance. It’s a tick box exercise in some ways: being detailed in how you assess the building, understanding what is built on site, and making sure that’s reflected in the calculation.

Doing more testing would reduce cost for the whole industry

We need to be able to survey our building stock at a level that gives us a better understanding of the energy performance of buildings, and not accept RdSAP as a minimum requirement. There is testing available, but it’s costly – and the only way to bring the cost down is to do more of it.

You can’t judge a building’s quality by its EPC

There is no information about indoor air quality, or other sustainability metrics. This is another area where Passivhaus excels. A Passivhaus is a good quality building that is pleasant to be in. We can’t tell from an EPC how good a building is going to be, so it’s impossible to compare one A-rated building to another A-rated building.

Studies are highlighting the issues with EPCs

Etude carried out a research project looking at EPCs versus metered energy use. And UCL Energy Institute has just published a paper looking at buildings they’ve been monitoring over a long period of time. The conclusions all come back to the issue of assumptions made in the SAP assessment.

In addition, there are formulas within the SAP calculation that have been ‘locked in’ for years and they don’t change. The development of SAP over the last 20 years has been slow and it doesn’t reflect modern buildings. People know there’s an issue, but there’s no process for SAP to be regularly updated. When changes are proposed they have to be consulted on, so it’s all very slow.

The Future Homes Standard is expected to change things

Because people know there are issues, an overhaul of SAP is expected alongside introducing the Future Homes Standard in 2025. If SAP changes, that obviously changes how EPCs are generated. It’s not clear how the government would reconcile the difference between existing EPCs and the future EPC system.

Home buyers can try to get hold of the SAP assessment behind the EPC…

…but it requires a bit of knowledge in order to sense check it.
- Make sure ventilation systems have been entered correctly.
- If a default value has been used for thermal bridging, you could try and work out if that’s a fair assumption for your kind of building. Maybe ask on forums if it is a suitable way of measuring thermal bridging.
- You could dig into the heating system and make sure what has been selected is what is actually in the building. Has the assessor selected all the right drop down boxes? Has a weather compensator been installed, for example.
- Also look at what the assessment assumes for the occupancy of the building, because that drives a lot of energy use. You can see if it’s related to how many people are going to live in the building.
If the numbers in the assessment don’t seem right then it’s up to you whether you appoint someone else to look at it. PHPP, or an open-source version of SAP, is available so it’s an option to try and do it yourself, if you want to.

You’ll always need a SAP assessment because of building regulations…

…but it’s interesting to do a PHPP calculation as well and compare the two. Etude has worked with local authorities to help them understand how SAP differs from reality.

The local authority can’t mandate PHPP calculations, so Etude helps them to convert the SAP result to a more realistic number that can be measured against a policy target. The SAP inputs are still limited, but Etude can correct for known errors in the assessment.

Getting EPC ratings wrong is a problem for retrofit policy

Something needs to be done with RdSAP to make sure ratings are in line with what is expected for a building. As more homes are retrofitted, assessors will need to understand the age of the building, how it’s constructed, and where retrofit measures have already been put in place, in order to have confidence that improvements being made are actually going to make a material difference.

Find out more

Visit the website of Etude

Check out the UCL Energy Institute’s research

Download the Passivhaus Trust’s research report on EPCs

Transcript

Transcript of House Planning Help podcast – episode 332 (Tom Gwilliam)

What are the UK Passivhaus Awards?

If this award ceremony is not on your radar then you need to invest some time following the competition and delving into the archive. There have been some outstanding self build and retrofit projects in the hall of fame, so we recommend a lazy Sunday morning checking out the fact-files on the Passivhaus Trust website and watching some of the videos.

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May 3, 2023
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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Transcript

Download a transcript of the interview with Simon Bell

Video of HLM’s Tigh na Croit

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February 1, 2023
HPH147 : A Passivhaus standard Q & A – with Elrond Burrell
Architect Elrond Burrell provides answers to a few common questions that people have about the Passivhaus standard.

Interview with Elrond Burrell

As part of Ben Adam-Smith’s video work, podcasts and meeting with other self builders, he is often asked questions about the Passivhaus standard that he doesn’t know how to answer. He recently took the opportunity to put those questions to Elrond Burrell.

Born in New Zealand, Elrond has been working in the UK for the last 18 years. As well as being a qualified Architect and Associate at Architype, he writes a plain speaking and successful blog about Passivhaus, which has a global following. Before he returns to New Zealand we caught up with him to tap into his Passivhaus expertise, and also find out what his plans are for the future.

Is it necessary to have a heating system in a small Passivhaus?

This will depend on the specific heating demand of the project. It is possible on a very small project to get away with just a portable electric heater, bathroom heated towel rail or similar.

A risk of doing this is that if the house is sold or has different occupants they might not be fully aware of this and find that they do get a little cold on rare days of the year. Elrond suggests a more robust approach is to just put in a very small heating system.

Another thing to consider is that heating is only one part of the equation in terms of power consumption, and actually in a Passivhaus building, providing the hot water can quite often be a bigger heating load than providing the space heating.

“And so you tend to design a system that can provide all the hot water needs for the year, and have enough capacity in that to provide the small amount of heating that you might need in the cold days of the year.”

Why might you not want the heat source to be incorporated into the ventilation system?

Firstly, air only has the capacity to carry a certain amount of heat. Water and solid surfaces can carry and radiate much more heat than air can. If you need more heat than the air can provide then you can’t do it all through the ventilation system.

Secondly, you need fresh air all of the time! In order to guarantee good quality, fresh, filtered air all year round, then you need the ventilation system running all the time. You don’t necessarily want the heating system running all the time though. There may also be times when you want more heating than the ventilation can provide. Although there is some logic in combining them, they are two quite separate systems in a way.

To avoid overheating, can you integrate a cooling system into the house?

The Passivhaus standard allows for 15kW annually of heating per m², and likewise allows for the same of cooling if required. In a relatively mild climate like the UK you shouldn’t need cooling if you’re designing the building well. In much warmer climates you would expect that in a very efficient Passivhaus you may have a small amount of cooling, the same way you have a small amount of heating. Like the heating, it can be provided by the ventilation system or separately through a radiant or other cooling system.

In a Passivhaus project you wouldn’t put something in as a ‘just in case’ measure, because using the Passive House Planning Package (PHPP) software you can very accurately design and predict how the building will perform.

“So you shouldn’t be putting in stuff just for the eventuality that it might be needed and you should be designing it to get it so you don’t have that need.”

Does it make sense to have mechanical blinds to give you a sense of control?

More commonly used in Europe and the US than they are in the UK, Ben says that some of the people he comes across like to have the mechanical blinds to give them an extra bit of control. Elrond suggests that it is important for people to feel in control of their environment and that they can modify and change things if they wish to. They shouldn’t feel that they’re living in a house which they’re not allowed to touch or interact with, so if people feel strongly about having the blinds then they should go with it.

Something to be wary of is if they’re built within the window it can be an expensive operation to fix or replace them if something goes wrong.

“So it’s not something specific to Passivhaus but it’s more the approach a lot of people that come to Passivhaus want to take is really simplification and trying to avoid moving parts and things that might go wrong at a later stage.”

The power consumption and how they get detailed and built into the building will also need to be accounted for in the Passivhaus modelling.

How adaptive can the house be in terms of comfort?

Regarding temperature, this will come partly come down to the design of the building. The upstairs rooms are likely to be a little warmer so personal preference about whether to sleep in a cooler or warmer room may be a contributing factor to the design. And if heat is being delivered by the ventilation system then wherever the air is being delivered is going to be warmer than where it’s being extracted from. If you’re heating through a radiant rather than ventilation system, then these can be located in areas where you would want to feel warmer.

Another thing about adaptive comfort, which is in the Passivhaus Institute guidance, is ensuring that all occupied rooms have got windows that can be opened.

Future Projects

When Elrond returns to live in New Zealand in the near future he will be continuing with his blog at elrondburrell.com. He has also set up a new company, VIA architecture, and will be offering a ‘PHeasibility’ service.

It is important to Elrond to embody his own personal values in the work he does. “So not just what looks like sustainability but what really counts in the details and in the putting it all together.” VIA architecture is based on the idea “that particularly using the Passivhaus standard we should be able to use architecture to transform the quality of peoples’ lives and so it’s really a process of using architecture to get to a good outcome. Whether it’s a really healthy, comfortable home, or a school or a business or what-have-you. And so architecture is kind of the process to get there rather than the end product in itself.”

The PHeasibility service involves Elrond taking early designs and running them through the PHPP in a basic way, before a commitment to employ a Passivhaus designer has been taken. It will give an indication for self builders or architects without Passivhaus experience, as to what might be involved, taking into account constraints and design, for the building to achieve the Passivhaus standard. It will look at the key aspects which determine if the fabric, orientation, windows etc are going to be of the required standard. They will then be better informed as to whether to pursue the certification.

Find out more about PHeasibility

Visit the PHeasibility website

Special offer: subscribers to Elrond’s blog can get Pheasibility for £495 instead of the standard £745 if they book it in September or October. To subscribe to the blog (direct link to subscribe: http://elrondburrell.com/hph_subscribe) and then send an email to PHeasibility@elrondburrell.com

Find out more about VIA Architecture

Visit the VIA Architecture website

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Relevant Articles

5 things to know about Passivhaus

Passivhaus Overheating: Design it out

Passivhaus: Solar Orientation Doesn’t Matter. Or Does It?

Transcript

Download a transcript of the interview with Elrond Burrell.

The Hub update

The Hub has now been going for a year and we’d like to thank the founding members who have put their faith in us. We’re always looking at ways to improve what we are offering and in the coming months we’ll be trying to make the modules even more step by step and easy to follow.

Our second case study is now under way, the Buckinghamshire Passivhaus, headed up by architect Janet Cotterill from CTT Sustainable Architecture. The project first started out as a retrofit so find out why it didn’t continue that way, and went on to be a new build.

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September 21, 2016
HPH103 : Is Building a Passivhaus Expensive? – with Geoff and Kate Tunstall
Geoff and Kate Tunstall explain how they were able to create a fantastic Passivhaus in Denby Dale with a budget of around £150,000.

Interview with Geoff and Kate Tunstall

When Geoff and Kate decided to self-build and downsize for their retirement, their first idea was to build a dormer bungalow with a conservatory. Following a conversation with Green Building Store, they were encouraged to explore Passivhaus as an option.

Back in 2008 there weren’t any examples of Passivhaus in the UK that they could visit, so they travelled to Austria. After visiting two properties there which had temperatures of 20/21 degrees, despite outside temperatures of -4 degrees, they made the decision that if they could afford it, this was how they wanted to build.

Paying a Ransom Strip Demand Used Up Their Contingency Budget

The plot for their build was at the bottom of the garden of their existing house. Unfortunately a builder had bought the plot of land behind this and, based on the value of the plot, demanded £30,000 for a six inch ransom strip that they needed to provide them with access from their building to the road behind. After a year of fighting this, and the builder realising that the money was their contingency so it was this or nothing, they eventually agreed to pay a total of £18,000, which used up their contingency before the build had even started.

During that year however, the designs for the house were all researched and finalised to the extent that as soon as the ransom strip issue had been resolved they were able to progress straight away with the build.

Making a 3D Model Helped Their Understanding of the Scale and Spaces

Originally they wanted to build a bungalow but the plot size didn’t make this feasible. Kate found it useful to create a 3D model out of balsa wood to get a better idea of how well furnishings would fit and how comfortable the spaces were likely to feel. They also found using the model was a helpful way of explaining their ideas to the building team throughout the process.

An Important Feature was to Have Light and Warmth Throughout the Fabric of the House

Particularly because their last property was a dark and draughty cottage, Geoff and Kate were keen to build a warm and contemporary home with lots of natural light. They had to abandon their original conservatory idea after running it through PHPP, but instead they remodelled it to feature a two-storey solar space which beams the light throughout the house.

Using Kate’s 3D model they realised that one of the bedroom windows seemed uncomfortably small. Again using PHPP the design could be changed to accommodate a larger window by adding higher performance floor insulation to compensate.

Keeping Within Budget was a Collaborative Process

From the outset, everyone knew the budget was only around £140,000. With regular meetings between themselves and the design team throughout the design process and the build, they were able to keep on top of what was happening, when, and how much things were going to cost.

Living on site was a help because they were able to spot any little details that needed changing before the build progressed too far and became too expensive to amend.

Geoff explains that on a Passivhaus there are certain non-negotiable things that need to be budgeted for and for which there are no short cuts, such as triple glazing and the ducting for the MVHR. Where they saved money was by spending time researching things like inexpensive lighting and kitchen units.

“But it was a good discipline for the Green Building Store and ourselves to actually work to a figure, a limited figure, because it proves that Passivhauses can be built to a reasonable budget. And the budget for our house isn’t a lot for what we’ve got.”

The Build Wasn’t Without its Challenges!

One of the biggest challenges they faced was building throughout one of the coldest winters in a generation. It was too cold to use the paint they had planned, mould spores started showing on the clay plaster and they had to put up a screen so they could continue working in the howling gales and snow.

A further challenge was the corner windows of the solar space, both from a Passivhaus point of view but also a structural one. They needed to make sure there wouldn’t be too much solar gain, and also ensure that the structural support would be inside the thermal envelope.

The House Exceeds Expectations

Geoff and Kate have been living in their house for around five years. They wanted a house that could be kept clean easily, that would provide warmth when needed, that would be energy efficient and not amass big fuel bills during their retirement. It has achieved all of these and something which Kate hadn’t focussed on before they started was how important it is to have a healthy house. She describes it as being a calm, tranquil and healthy place which will benefit them in their old age!

One of the Passivhaus buildings they visited in Austria had some underfloor heating so Geoff and Kate assumed they should put it in their kitchen and bathroom. In hindsight they didn’t need to as it’s actually never been used.

Geoff is adamant that anyone embarking on a self-build project should go and visit a Passivhaus. Once they’ve experienced it he’s quite sure that’s how they will then go on to build. He says that even if the initial outlay is a little more expensive, it will pay for itself within three or four years, and be future proofed against rising fuel prices.

Find Out More

Find out more about Denby Dale in the Green Building Store blog.

Transcript

Download a transcript of the interview with Geoff and Kate Tunstall.

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October 13, 2015
HPH097 :What Do You Get for Passivhaus Certification? – with Peter Warm from WARM

Peter Warm from WARM: Low Energy Building Practice explains why building to Passivhaus standard is desirable, how certification comes into the equation, and what steps will increase your chances of reaching certification.

Interview with Peter Warm

Peter has been an energy engineer all his working life and is fascinated by high performance buildings. Through his involvement with the AECB he got into Passivhaus certification, and this is now a key service offered at WARM: Low Energy Building Practice.

“Glass Boxes are a Huge Problem”

One of the biggest challenges WARM face is communicating to architects that vast quantities of glazing in a Passivhaus actually create a “solar cooker”. While the glazing is expensive it also creates a problem which will need remedying with the additional cost of solar shading.

“Glass boxes” are effectively huge energy consumers, either for heating or cooling.

Passivhaus Certification is a Form of Training for Designers

Peter thinks of the certification process as a form of training because it gives designers a deeper understanding of how the decisions they make impact on the energy performance of their buildings.

If the designer hasn’t reached the Passivhaus standard before then inevitably there is a learning curve. However, the certification process provides support throughout, in order to iron out any issues before they occur.

For designers that WARM have worked with many times before they will be offered a greatly reduced quote because they need far less hand-holding throughout the process. In these cases, it’s really all about the documentation.

“Passivhaus Certification…It’s Just About Building Buildings Sensibly, Doing it Properly”

Peter suspects that in 20 years time the current quality of a Passivhaus will be the norm for a new build. Although much of the UK construction market is currently lagging far behind in terms of build quality and low energy standards, Peter sees retrofits as being a greater challenge for the future. There needs to be more education about the dangers of getting insulation wrong which – if not done properly – can cause mould, condensation and rot as well which in turn can impact on the occupants’ health.

The Steps to Certification

The Quote – This is based on the plans and sketches, an idea of how long the process is going to take and the level of support the designer is likely to need.

Design Review – It is important to review the designs before planning to look at the impact of things like the form factor (on insulation and airtightness) and fenestration (on solar gains).

Checks Before Going On-Site – WARM will usually do their own PHPP calculations to check thermal bridging, airtightness, heating, ventilation, etc.

On-Site Checks – This doesn’t usually apply to small projects. On large ones there can be a high turnover of tradespeople so the checks are helpful in identifying any problems at the time.

The Air Test – Along with the air test they check the commissioning report for the MVHR and make sure the system is working properly and quietly. If they’re happy with everything the information is sent to Germany for the authorisation to issue the certificate.

Reasons Why Buildings Fail Certification

Airtightness – Failing to test while there is still access to the airtightness layer can be a big issue in one-off houses. This needs the doors and windows to be put in at an earlier stage than a builder would normally like.

Building Services – This usually applies more in larger buildings. In particular it is poorly designed or installed ventilation units. When this happens the fan has to work harder which means greater noise.

Not Consulting Throughout – Less common is when people just build their buildings and then approach WARM for certification once it’s complete. In this instance it is likely they will not reach the standard.

As Passivhaus is about the comfort of the occupants, failing certification will mean that it may not be as comfortable as they would like, perhaps living with draughts and MVHR noise. Peter says: “Comfort is one of those strange things where, if you notice it, it’s not comfortable.”

Airtightness was the Biggest Challenge for WARM’s Own Office Retrofit

Built in the 1960s, they have transformed a draughty first floor flat into an EnerPHit standard office.

They achieved this by insulating externally, filling the cavity, insulating between the office and the shop, and putting in roof insulation at rafter level.

Deciding where the airtightness layer was going to go was the biggest challenge, particularly as the shop below was not part of the retrofit.

All the windows were also replaced with high performance triple-glazed windows and an MVHR system was installed.

Inevitably Building Regulations will Catch Up with the Passivhaus Standard

Peter considers Passivhaus as being such common sense that he believes it is inevitable that regulations will eventually meet the standard. With building regulations changing every few years to require more insulation for example, by choosing Passivhaus now your project won’t date.

Peter says: “It will happen. You’re just making it happen a little earlier.”

Find Out More

Transcript

Download a transcript of the interview with Peter Warm.

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September 2, 2015
HPH053 : An Introduction to the Passive House Planning Package (PHPP) – with Mark Tiramani

Mark Tiramani, the self-builder behind the UK’s first certified Passivhaus, shares his experience of building Y Foel and how this got him interested in the Passive House Planning Package (PHPP). He explains what PHPP is and why it’s a valuable tool.

Interview with Mark Tiramani

Mark and his wife Shirley first came up with the idea of building their own house when they were working in New York, USA. While backpacking in Upstate New York at the weekends, they met somebody who really impressed upon them the idea of treading lightly on the planet.

Initially they dreamed of a straw bale build but on returning to the UK they came across the concept of Passivhaus.

The plot had an abandoned cottage on it

Their Designer/Builder Introduced Them to the Concept of Passivhaus

John Williamson from JPW Construction mentioned Passivhaus to Mark and Shirley.

Mark, who had spent 13 years living in Germany, immediately warmed to the idea: “I thought, it’s actually a way of working out how much energy you would require to heat a house and run it. That got me interested.”

The plot was cleared and new foundations were laid

PHPP is a Sophisticated Set of Integrated Spreadsheets

PHPP is an Excel workbook, and accompanying user guide, for optimising the thermal performance of a building.

Mark did the PHPP calculations for his windows

Using PHPP Helped Dispel the Myths and Mystery!

As this was very early days for Passivhaus in the UK when the project started (at the end of 2002), a lack of resources and expertise meant that Mark decided to do some of the PHPP work himself.

However, having taken this step, it helped him reach a much deeper understanding of what was going on.

PHPP is simply a tool to work out what a building is going to do thermodynamically. Using building physics it joins up all the dots.

You Need the Specifications of the Products You’re Using

In order for PHPP to produce meaningful results it needs reliable data going in.

Mark gives an example of how he added in the required specifications of a window by doing finite element analysis (with software called Therm).

The window has to be broken down into all its elements, such as the glazing, the coating, the spacer and the actual frame, etc. Precise measurements are required at every stage of the process or accuracy will decrease. The numbers that come out of this step go into PHPP.

*This stage was only necessary because the windows Mark talks about were not certified.

PHPP Has a Database of Certified Products

PHPP has a database of products that have been tried and tested. So if you are using one of these products you are already a step ahead because the specification data will be on a drop down list and just needs to be selected.

PHPP Also Takes into Account Factors Including Climate and Shading

The PHPP calculations go beyond just using product data. It needs specific information on the climate, shading, properties of the ground, thermal bridges and so on.

Mark says: “It’s calculating a whole bunch of things. The things that people know about are the specific space-heating requirement. That’s the famous 15kWh per m2 per year. You can pass on that alone plus overheating plus total primary energy consumption. So there’s basically those three things but you can also pass on the heat load or heating load. That’s calculated based on climate data.”

The PHPP climate data for Mark’s house

Recently Mark Has Redone All PHPP Calculations for his House

Although Mark did the PHPP calculations for his windows in 2009, recently he decided to start from scratch and do the whole house!

Now that he’s much more familiar with PHPP the process was a lot easier and he is confident that the figures are extremely accurate now.

There are some elements that can never be 100% accurate though. Mark says: “A couple of things are very difficult to do in PHPP, really. Shading is one. It’s a bit down to guesswork, so it’s that artistic licence.”

Every Iteration of PHPP Potentially Reduces Errors

Mark knows that he made some minor mistakes when he did the PHPP calculations in 2009 but as it goes into so much detail and in so many areas, small errors or incorrect assumptions may not skew the overall calculations too much.

PHPP is also getting better at spotting user errors. For example, if you accidentally misplaced a decimal point it might realise and flag up that this is an unrealistic figure.

Find Out More

Visit Mark’s website on Y Foel

Transcript

Download a transcript of the interview with Mark Tiramani.

What’s it Like to Live in a Passivhaus?

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May 14, 2014