HPH353: 12 tips for a successful Passivhaus project

Speakers from the Passivhaus workshop event at the National Self Build and Renovation Centre in Swindon each share a top tip.

Ben Adam-Smith caught up with various people who were involved with the Passivhaus workshop event and asked them for a piece of advice that could be applied to a Passivhaus project. These tips are in no particular order.

1. Put ‘Passivhaus standard’ on the brief on day one

Anna Carton from Passivhaus Homes recommends integrating the Passivhaus standard as early as possible into your build, preferably pre planning. Passivhaus is a holistic approach and all aspects of the design influence the performance of your home. Anna suggests that it is possible to take a standard design and make it into a Passivhaus design, but warns that aesthetic choices or use of certain materials, etc. might introduce challenges around thermal performance. Therefore, starting with clear intentions from the beginning can lower your costs and save you the headache.

To find out more about Passivhaus Homes, head over to episode HPH341, where Jae Cotterell debates whether embodied carbon or energy efficiency should be our priority.

2. Consider the placement of your services early on

Gordon Bunker, owner of Worcester Renewables, recommends taking some time to work out where best to locate your ventilation, heating and power generation systems. Gordon explains that building services can be overlooked in the design stages or assumed to be smaller than they are, so proper consideration early on will ensure they are allocated enough space and therefore easily accessible for maintenance. Gordon mentions that 3-5% of your total floor space should be put aside to house these systems.

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

3. Budget for thorough airtightness testing

Neil Turner, the UK Technical Manager for Ecological Building Systems, highlights the importance of intermediate airtightness testing during a Passivhaus build. Neil suggests undertaking an airtightness test once all of your membranes, tapes and boards are in place to identify if you have missed any areas around windows, doors or pipes. If there are some leaks, address them and test again to make sure the airtightness has improved. Then you can start on your finishes. Doing this will ensure that you seal up any leaks at a point where they are still easy to fix.

If you’re one of our Hub members we’ve got a live training session with Niall Crosson from Ecological Building Systems. He explains all the important aspects of airtightness.

4. Be prepared to fully commit to Passivhaus

Rob Bohm, Head of Energy and Sustainability at CLPM, explains that Passivhaus principles will impact the design of your house so you must be prepared to fully commit. Rob says that Passivhaus projects are “not for the faint hearted and can have severe limitations on what your choices may be”, but if you undertake the journey it will repay you in numerous health, lifestyle and financial benefits.

5. Keep it simple

Mike Shufflebotham from 21 degrees highlights that when it comes to high performance windows and doors the simpler the design, the less it will cost and the better it will perform. This is because the glass is a much better insulator than the frame. By introducing mullions and transoms into your window design, you increase the proportion of frame to glass, which as a result lowers the performance, whilst increasing the cost through the additional labour and joinery. The final product performs worse and costs more than the original simple version.

Embracing simplicity is a common theme in Passivhaus building. We explain why in episode HPH350.

6. Take a fabric first approach

Robin Miller, Director of Beco Wallform, explains that “if you get the right fabric, the right quality and the right performance, it makes the rest of the project so much easier”. Through the fabric, you can minimise the energy requirements of your home and create a much more comfortable living environment. Robin therefore recommends taking some time to identify which building material aligns with your self build values and overall goals for your home.

7. Optimise the form (or shape) of your home

Alan Budden, Architect and Passivhaus Designer from Eco Design Consultants, advises keeping the overall shape of your house as simple as possible (achieving a good form factor). By doing this, you minimise the heat loss area relative to the floor area, making it perform better and also enabling you to reduce the amount of insulation you need to meet Passivhaus (which in turn makes it cheaper!). This doesn’t mean that the building has to be boring, in fact many classic architectural styles use simple shapes and get the proportions right. The structure is also a blank canvas and you still have the freedom to be creative with materials and internal finishes.

8. Check your window frames for insulation

When it comes to high performance components, Vasilis Giannopoulos from Internorm highlights the importance of checking that your window frames are well insulated. For example, if you choose composite windows identify whether there is insulation in between the external and internal layers, rather than just an air gap.

“When you go into the market for Passivhaus windows, always focus on the frame of the windows. It’s going to be easy for any window supplier to match the performance specifications you have for the glazing units. So please focus on the quality and the performance of the frame.”

9. Make sure you research your future ventilation system thoroughly

Ben Collins from Air Flow suggests researching the ins and outs of your ventilation system at the planning stage. From talking to installers to identifying which add ons you may require, you will be able to get a clearer picture of which ventilation system may work best for your future home and offer you the best energy efficiency. There are many bolt on options out there that offer different features and benefits, but they must be brought in and designed during those early stages.

10. Understand your budget

Iga Panczyna, Architect and Passivhaus Designer for Allan Corfield Architects, believes that it is crucial that self-builders have a realistic understanding of what they can achieve with their budget. Iga highlights that there are ways to achieve a Passivhaus on a restricted budget, but this relies upon good design and clear planning from the start. Additionally, those whose budgets will not quite get them to Passivhaus standard, can still follow the principles to get the home as close as possible.

11. Practice any skills you intend to use during your build

Paul Jennings from Aldas recommends practising your skills ahead of when you will need them for your own build. This is particularly important for insulation and airtightness because there needs to be attention to detail to ensure the finished performance.

“My top tip is plan ahead, prepare, practice, look at what you’re doing, think about the design, look for joined up-ness, is your airtightness line consistently joined up? Is it practical? If you’re doing any sorts of fancy tapes, you’re doing preformed corners, practice! Don’t practice on your build, practice before you get to your build.”

A few years ago we made a documentary with Paul Jennings

12. Don’t mess with the formula

The final tip from Ben was to not mess around with the tried and tested approach. It can be tempting to go off piste and just do the bits you like, but Passivhaus building is a holistic process and by messing around with one aspect there could be unintended consequences.

“That’s one reason why I like certification, because it shows that you’ve done all the bits and that it should work at the end of the process, because it’s a quality assurance process.”