If you’re building a new home or looking to retrofit an existing property there are lots of good reasons to consider targeting Passivhaus standards. Not only are you getting a much better quality of building but it will be more comfortable, healthy and energy efficient. The heating bills will be low and it will be a tranquil space.
You may well be sold on the idea already and have heard the feedback countless times of the many benefits of building a Passivhaus. What if you don’t achieve these outcomes, however? What guarantees are there that if you embark on this journey you will get to the end and still be singing the praises of this approach?
The good news is that there’s a well-trodden path and the Passivhaus Institute, who roll out the standard, has built in some safety nets that make it hard to go wrong. This is called certification and it can apply to people, products and projects. When we think about certification in relation to our homes it is a compliance check that everything is in order and that we’re on track to meet the performance criteria. This is not something to tag on at the end, however, it starts when you begin to develop your designs and finishes when your building is complete, you’ve had the final airtightness test and the MVHR unit has been commissioned.
An audit of your home
The best way of thinking of Passivhaus certification is as a useful audit, which is independent from the design team. If your architecture firm is new to Passivhaus then you could even treat this as training, because it gives them a deeper understanding of how the decisions they make impact the energy performance of their buildings.
In the UK, there are about a dozen certifiers at present, from single person outfits to much bigger companies, and they will review the project at various stages and offer feedback, carry out the as-built assessment, and submit information to the Passivhaus Institute for authorisation to issue a certificate.
The first step is to pick up the phone and speak to your chosen certifiers, share some project details and find a good fit for your project. Some certifiers will charge by the size of the project whereas others might be considering the level of experience on the team and hence the time they will have to dedicate. As an example, for a modest-sized detached dwelling the fee might be in the region of £2,000-£3,000.
The large kitchen diner was central to the plans for Ben’s Passivhaus(Image credit: Darren Chung Photography)
Design and construction review
Once they are part of your project team, the certifier will want to look at the PHPP model (Passive House Planning Package) from your Passivhaus designer or consultant to check everything has been filled in correctly and that you are on track. Rarely does the performance get better with different iterations, so starting with a conservative goal (for example 12kWh per m2 instead of aiming for 15kWh per m2 on a project aiming for Passivhaus standard) is a good idea.
Before the designs go to your local planning department for approval, the Passivhaus certifier will want to review the orientation, form of the house, complexity and glazing, and offer feedback. Optimising these elements at this stage can lead to cost savings, help buildability and improve summer comfort.
After the initial review and design review, there will also be a construction review. This confirms that everything from the design phase is being executed on site so there is no downgrading of materials or sloppy workmanship. Your certifier will not be coming to site, unless this has been built into the fee as an extra, so photographic evidence will be needed at key stages, checking things like the continuity of insulation and airtightness layer.
Finally there will be the as-built checks which will gather together the evidence for the Passivhaus Institute, including the airtightness test results and the MVHR commissioning report.
Benefits of certification
Certification is a mixture of making sure you’re following the formula and having another set of eyes and experience on the project. Working with a certifier almost guarantees you will finish up with a certified home. In rare cases the struggle might be with reaching the airtightness target. The other danger is that you conclude that you can save a couple of grand by dumping the certification, and just following the principles. While this may work, particularly if your team has built several certified Passivhaus projects before, you could easily be way off the mark with a huge performance gap.
It’s also worth reflecting on the resale value of your home. Over time certified Passivhaus homes should become more valuable than an uncertified Passivhaus. Your plaque by the door is backed up by the paperwork! So don’t begrudge certification. See it as an important step and an investment into your home.
If you want to find out more about what it is actually like building and living in a Passivhaus, our expert Ben Adam-Smith talks through his experience in detail in our piece on the topic. He explains what he discovered, including why mould and condensation really did become a thing of the past as well as if the lofty claims made about airtightness really are true or not.
View the original article and our Inspiration here
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