Passivhaus: What's in a name?

If the UK is to achieve an 80% reduction in carbon emissions by 2050, the quality of the buildings that are constructed and refurbished need to be vastly improved. At the moment there is often a massive divide between the energy performance of the designs on an architect's computer screen and the completed building. Recent research by Leeds Metropolitan University has found that both low energy homes and even those built to meet current Building Regulations are not performing as promised.

It's not an issue unique to the UK. Back in 1983 Sweden developed an energy performance standard that limited the space heating to 50-60 kWh/m2 per year - that's the theoretical performance to the UK's current Building Regulations. In mainland Europe the Germans took note and, recognising that the average for their homes was closer to 200 kWh/m2 per year, realised that adopting the Swedish energy target would slash their energy consumption; what followed was the largely unofficial voluntary “low energy standard”.

However, what this eventually led to was a tendency for architects and builders to make claims about having built low-energy houses simply because they orientated the house in a southerly direction or applied an extra couple of centimetres of insulation. After a while newspaper articles began to crop up with statements such as “family uses more energy in their new low-energy home than in the old heritage building they previously occupied”. The German research that followed found that their low energy buildings did not always perform as expected. An eerily familiar message to the one by Leeds Metropolitan University.

The point to all this is that the focus for low-energy buildings is often on design targets. Whereas what might be a better approach is to focus on the process used to deliver the building. Ultimately what is needed is some form of quality assurance.

The problem was overcome in Germany with the development of RAL 965 for Low Energy Buildings. This simultaneously created a definition for low-energy buildings, protected the design standard from abuse and, as a basic term and condition for delivery and sale, provided the people requiring low energy buildings with a quality assured product.

Interestingly the most recent version of RAL 965, issued in 2009, also includes the Passivhaus Standard and requires that both low energy buildings and Passivhaus buildings are designed using the Passivhaus Planning Package (PHPP).

By way of explanation, the PHPP is a simplified design tool and a means of ensuring that all the requisite aspects of the comfort criteria and building physics are addressed in the appropriate way and in the necessary detail. It carefully considers heat losses and gains associated with airtightness, ventilation, thermal bridging, solar gains, internal gains and the like.

For a Passivhaus the use of PHPP is the most fundamental aspect of the quality assurance process. One of the principal benefits that PHPP offers is that the designer does not have to return to first principles. In addition, not only does the tool include all the necessary aspects of building physics that need to be considered, but it also establishes a datum that allows one Passivhaus to be compared to another. The PHPP conveniently establishes a number of conventions that can simplify the design process and enable validation.

Recently I have had the issue of quality assurance in mind when I've read various articles in the press where journalists, clients, architects or builders have made claims about schemes that have been designed to the Passivhaus standard. At first I always find the reports of a new Passivhaus very encouraging, but after a while, as I read the article, I repeatedly find telltale signs - errors and omissions - that suggest that the projects are not actually Passivhaus buildings at all. Worst of all, in some cases, there are even claims of building in accordance with Passivhaus “principles” - these projects are certainly not Passivhaus buildings. While they are no doubt designed and built by well-meaning individuals, the projects have not been subjected to the same level of rigorous analysis (leading to inappropriate specifications), they have not used the correct design tools (leading to erroneous assumptions) and they have not been subject to the same standard of quality assurance both on and off site (which means that errors can creep in and as a consequence theory and reality will not converge).

Now, I can hear you say “Do such claims matter?” To me the obvious answer is a resounding “yes”. For instance, imagine if someone claimed to have a BREEAM “outstanding” office. Would you expect them to have certification to prove it, or would you think it okay for them just to pass it off without actual substantiation - just because they say that they tried harder than usual?

At the moment what I have witnessed is that this kind of thing is happening with the Passivhaus standard. Here and there people are making ill-informed, often unsubstantiated, and false claims. While energy efficiency is the focus of the Passivhaus standard, it is an over simplification to suggest that it is “simply” an energy standard. It is in this respect that it should be recognised that Passivhaus is also a quality assurance standard. In order to deliver buildings that perform as predicted, as a quality assurance system, Passivhaus works on a number of levels and includes; certifiers, designers, components and ultimately buildings.

Is all this quality assurance required? Well, there is mounting evidence to suggest that buildings that are being designed to achieve thermal performance standards, including the Building Regulations, are in some cases consuming in excess of 70-100% more energy than the predicted values. In light of the recent discussions at Copenhagen, if there was ever a need for quality assured construction it is now. The old adage “you can not manage what you cannot measure” would seem particularly true here.

The rise of standards such as the Code for Sustainable Homes has led to a dearth of “innovators”, each with their own untried and untested super product or concept. While it is great that the UK construction industry is finally thinking, there is an inherent danger of reinventing the wheel at great expense. Perhaps we could in fact be learning from projects that have already been developed, trailed, tested, verified and proven to work.