Passivhaus is one of those terms that you may come across in the world of self build and have absolutely no idea what it means. But with its exacting standards and principles, it is no mean feat to achieve Passivhaus certification.

Many think it is just what the Germans call an eco house, but this would be doing the Passivhaus standard a disservice. It is the creme de la creme when it comes to low energy homes, and is only achieved when thorough guidelines and criteria are met.

Here are some important things about Passivhauses that you probably didn’t know.

1) The Movement Started as a Research Project

The idea of low energy homes is not new. Many had tried to achieve low energy builds, but failed when it came to delivering on the promises made at the design stage. The Passivhaus movement started as a research project on why these previous attempts to build low energy homes had failed and lead to the creation of detailed, thorough and exacting guidelines on how to get it right.

2) You’ll Need to Use a Software Package

With such exacting guidelines to be met with the standard, the Passive House Institute devised a software package called the Passive House Planning Package.

Also known as the PHPP, it allows you to feed in all the construction details of your project and it calculates a predicted space heating demand. You then adjust your design and specification details until the predicted space heating demand meets that required.

3) Certification Costs

It can cost around £1,500 to get your house certified (and without the certification, you cannot technically call your house a Passivhaus). And that’s not to mention the certified products you may need to invest in to achieve this standard.

If you have gone to all that effort to build to Passivhaus principles then it’s likely you are going to be pretty invested in the certification step. But if your budget just can’t stretch to it, then you can still build to the design principles using the PHPP.

4) You Can Apply Passivhaus Principles to Existing Homes

Passivhaus is a standard for new build homes. It is very difficult to apply this standard to existing homes, as elements such as the orientation are already fixed. You may also have thermal bridges that are difficult to completely eliminate.

With this in mind, the Passive House Institute developed the EnerPHit standard. EnerPHit recognises this difficulty and sets the required performance at a lower level to accommodate working with existing buildings.

5) It’s About Low Energy Demand Rather Than Renewables

With a Passivhaus, the onus isn’t on using only the most efficient renewable technologies. It is about designing a home that requires much less energy usage than the standard house, especially when it comes to heating.

5) They are not Easily Adapted

It is worth taking your time when designing a Passivhaus as once they are built you have very little scope for change without undermining the stringent guidelines. As airtightness requirements are so ambitious, even drilling a hole for a cable from satellite dish is frowned upon and could revoke your certification.

6) You Must Learn How to ‘Drive’ Your House

In order to achieve the standards required, Passivhauses often feature various technologies, such as an MVHR system and perhaps renewables, that may require some getting used to in terms of operation. 

7) Cat Flaps

For cat owners, a catflap might seem like a simple requirement for the home. But in a Passivhaus, it is not as straightforward as it would be in a standard home. As Passivhaus airtightness standards are so exacting, you would need to choose a certified catflap (and, believe it or not, there are options available!)

8) They are Really Comfortable to Live in

Building a Passivhaus is a lot of trouble to go to if you don’t respect it’s integrity and use the incorporated tech as intended. That aside, the year round comfort of the internal environment (without having to rely on energy-hungry heating systems) is well worth it. Just ask anyone who lives in one!

Main image: Jon Martin and Noreen Jaafar have built a Passivhaus-certified treehouse in the centre of a Cotswold market town, taking advantage of a woodland site.

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