Passivhaus: The experts speak

In a previous article, we looked at the Passivhaus specification. This time, we talk to three leading figures from the Passivhaus movement about their work and views on the future of sustainable building.

First we spoke to Bill Butcher, Director of the Green Building Store.

Green Building Store manufacture and supply sustainable building products as well as providing technical support. In 2009, they received the Queen's Award for Enterprise in the field of Sustainable Development.

Bill, of the projects you encounter, what percentage are actually certified to the Passivhaus standard?

“I don't have an exact figure but a 'guesstimate' would be 20% overall. Having said that, our MVHR (mechanical ventilation with heat recovery) products are mainly supplied for Passivhaus projects, so in their case the figure is more like 90%.”

What sorts of Passivhaus buildings are your clients making?

“We've supplied a large number of new builds and retrofits across the UK. They include community centres, co-housing schemes and private self build projects.”

How about windows?

“One type of window that was less common on Passivhaus projects was the outward-opening casement type. But we've recently introduced a range of Passivhaus-certified timber windows and this includes a casement. It means architects and designers can now choose a cost-effective window with a very impressive U value of 0.68 W/m2K.”

What about other things that are needed for Passivhaus – are a lot of your products to do with insulation and air sealing?

“Absolutely. We've a lot of specialist brand products for low energy buildings. Things like grommets, membranes, tapes and adhesives, all specially designed for the job.

“There are also products such as basalt fibre wall ties with low thermal conductivity and rigid foam insulation, used to reduce thermal bridging around window and door thresholds.”

Are there product groups for which the Passivhaus specification has been particularly challenging?

“MVHR systems are relatively new to the UK and it has to be said it's taking the industry a while to get used to them and ensure optimum installation and performance.”

What's your view regarding Passivhaus in the UK? How do you see the future?

“Passivhaus is growing exponentially in the UK. There has been great impetus from forward-looking local authorities, housing associations and private self-builders.

“In my view, it now needs to be embraced by national government to help it grow even more rapidly. One simple way, relatively easy for politicians to implement, would be to give Passivhaus ‘Deemed to Satisfy’ status within the Building Regulations. This would provide further recognition of the quality assurance the specification provides and really help move sustainable construction forward.”

We then got on the phone to Nick Grant of green building consultancy Elemental Solutions.

Nick has been a long-term supporter of the Passivhaus specification in the UK. He is a trustee off the AECB (Association for Environment Conscious Building) and Technical Director of the Passivhaus Trust.

Nick, why Passivhaus?

“Because it gives us a ready made tool that works out of the box. It lets us focus on the design rather than worrying about how far to go on each project in light of various ever-changing codes and regulations. I’m not saying Passivhaus is perfect, but it works – and that is also the conclusion of most of my long term colleagues in the field.”

You've worked on some Passivhaus schools. Can you tell us a bit about them? Do they present challenges different from a residential home for example?

“In fact the first three Passivhaus projects that I worked on were schools. I would have preferred a single family house to get started with, but you have to take what comes along!

“One was in Leeds, the other two in Wolverhampton. All were designed by Architype and I worked closely with my fellow Passivhaus collaborator Alan Clarke. With schools there are many more complexities so it is even more of a challenge to try and keep things simple.”

Is it true that the kitchens presented the biggest challenge?

“Yes, indeed. Passivhaus is of course mainly German in origin. The thing is, German schools don't usually have full kitchens, so there was little previous data to go on. We had to work out most of the solutions ourselves.

“The team did an excellent job of providing comfort with minimal energy use. Alan used it in a presentation to the International Passivhaus Conference in Hannover, so we were really proud of that.

Do you live in a Passivhaus yourself?

“Well, my partner Sheila and I did build our own house, but sadly this was before I knew about Passivhaus. We got a lot wrong but that is the only way to progress and a lot of the details we worked out 15 years ago have found their way into current projects, even the schools.”

Can you give us an example?

“Sometimes we want to do things and are told they won’t work. The only way to move forward is to try and prove they do. We wouldn’t have dared suggest using 10mm hot water pipe, to reduce the wait for hot water, on other people’s projects if we hadn’t tried it first on a test rig and then our own house. Thanks to John Cantor for the inspiration on that one.

Wasn't there also something about spray taps?

“Yes, we were told we couldn’t use spray taps in the latest school because of the aerosol creating a legionella risk. We set up an experiment to compare the aerosol from the sprays with that from a standard outlet and found that there was actually less risk with a spray tap.

“To cut a long story short, the latest school has small bore hot water pipes and spray taps.”

In your view, has Passivhaus been taken up in the UK as fast as it should have been? How do you see the future?

“I don’t believe anything we are doing is fast enough but nothing can be forced without the will.

“In terms of the future I’m an optimistic pessimist. I know most problems are not technical but political and I’m pessimistic about politics. But what else can we do other than do what we think is right?”

Last but certainly not least, Elrond Burrell, associate of Architype.

Elrond is an expert in the areas of Passivhaus and timber construction. He's also a strong advocate of Building Information Modelling (BIM) and speaks regularly on sustainable design to international audiences.

He has recently played a major role in the design of Chester Balmore, a mixed tenure housing scheme in Camden that is the largest residential Passivhaus project in the UK to date.

Elrond, as an architect how did you get involved in the Passivhaus movement?

“Architype have always designed sustainable, high performance buildings and Passivhaus seemed a natural next step for us. We like to stay on the leading edge and there was very little built to the Passivhaus standard in the UK at the time.

“Many people were beginning to realise that with most buildings designed to be energy efficient, there was a “performance gap” – the difference between the designer's predictions and the “real world” efficiency.

“Passivhaus had all but eliminated this gap and we wanted to bring this significant benefit to our clients.”

A lot of the Passivhaus buildings made so far in the UK are schools and homes. What about commercial buildings – is Passivhaus suitable?

“Commercial buildings are a very good fit for Passivhaus – they are generally larger and so it makes it much easier for the building to be energy efficient because the ratio between the volume of the building and the area of the external envelope is more favourable.

“Cost-wise, the increased fabric performance requires a smaller proportion of the overall budget. Also, the financial benefits for larger buildings are accordingly greater.”

You do a lot of "myth busting" regarding Passivhaus, so obviously there are still quite a few misguided views around. Which do you encounter most often?

“The belief that 'you can’t open the windows' is a typical myth. We design all our Passivhaus buildings to be ventilated naturally in the summer and encourage occupants to open windows as much and as often as they like.

“Even when mechanical ventilation is in use during the heating season, we still encourage people to open windows as and when they wish – it’s really not a problem!

“Another incorrect one is, 'You need a lot of south-facing glazing'. This is probably due to people confusing Passive Solar Design philosophy with the Passivhaus standard.

“Actually, on larger buildings you really don’t want too much south facing glazing as it means more external shading will be needed to avoid overheating. Passivhaus is a whole building physics approach: solar gains, internal occupancy and equipment gains are all accounted for.”

How do you feel about the progress of Passivhaus in the UK?

“I am very excited about the progress of Passivhaus in the UK. There seems to be news every month of new projects. There is a real feeling of it going mainstream.

What would you like to see happen next?

“Personally I would like to see a high-rise office building in the UK delivered to Passivhaus standard. It would be a clear demonstration of the immediate and long term commercial benefits of Passivhaus – and the ability of the UK industry to deliver quantifiable high quality construction.

“We know Passivhaus has environmental and health benefits, but to fully break into the mainstream the commercial questions need to be answered more definitively.

“It's a fact that we have delivered Passivhaus schools at no additional construction cost and with significant operational cost savings. So with the right approach it is definitely possible.”

Many thanks to Bill, Nick and Elrond for their time in making this article so informative.

The Passivhaus movement is hugely active on social media, especially Twitter. You can follow our three contributors at their own accounts:

Bill Butcher – @billbutch
Nick Grant – @ecominimalnick
Elrond Burrell – @ElrondBurrell


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