We recently caught up with Dr Daniel Lash to talk about Passivhaus design.

Daniel is a Senior Research Fellow at the Centre for Energy and the Environment at the University of Exeter. He formed part of the design team, acting in the role of sustainability adviser and energy modeller, for Passivhaus building projects such as the Montgomery Primary School.  The school became the joint first Zero Carbon Passivhaus building in the country, producing all its energy needs from photovoltaic cell panels housed on the roof.  The building has been broadly running at net zero carbon since its completion in 2012.

Daniel has also worked with Gale & Snowden, architects on the St Sidwells Point swimming pool development.

Daniel, could you tell us about Passivhaus buildings and some of the benefits of this type of design?

The first thing about Passivhaus is that not everyone has heard of it, and those who have, may have heard of it as an energy standard.  Actually, its evolution started as a comfort standard.  It’s something that came out of Germany; the first Passivhaus development was built as a scientific exercise, in around 1990, but it has been occupied ever since.  The philosophy behind the design means that it focuses heavily on reducing heat losses through the fabric and the ventilation of the building. 

‘This means that compared to a typical building, the internal surfaces of things like the walls and the windows are at a higher temperature and are consistent throughout the space.  A Passivhaus home feels different to a typical building, as they are more thermally comfortable.   The ventilation system captures the heat as it’s escaping, which means that the building is adequately ventilated all year and has good levels of fresh air’.

How does that compare to a regular building?

People are often reluctant, especially in the UK, to do things like open windows in the winter.  They end up having to make a difficult choice between opening a window and incurring higher running costs.  The alternative is having it closed which leads to poor air quality; having moisture build up because of the high heat loss which leads to things like damp and mould.

These are issues that you don’t have in a well-designed Passivhaus building because they’re designed for human comfort.   A useful side effect of that is that the energy consumption is extremely low, so it’s a ‘win win’ situation.  To give you an idea of how efficient they are, a typical living room could be heated by five candles in the middle of winter. They are generally healthier buildings which use less resources, and these are things that we should be prioritising now given the climate change declaration for zero carbon in Exeter and Devon’.

Are there any drawbacks to Passivhaus Buildings?

‘I’ll focus on housing to answer this.  To deliver a new Passivhaus building generally costs more than delivering the equivalent minimum regulation standard building.  That cost has to come from somewhere and generally in the UK, most of the housing is delivered by volume house builders who are reluctant to commit to anything that ends up costing more per house. There are, however, housing developments in and around Exeter that have taken the Passivhaus approach. Exeter city Council have been very proactive on the social housing side of things.   We are starting to see more open market private housing coming forward in terms of Passivhaus too.   They can cost a bit more, but the costs are coming down and people need to recognise the benefits of reduced lifetime running costs, the healthier living space and the benefits to the environment’.

Final thoughts on Passivhaus in Exeter:

‘Exeter is quite ahead of the curve, because the council has been so proactive and because we are starting to get non-residential buildings, like the swimming pool and care homes; you don’t see them a lot across the country.  Exeter, as a city, has ploughed on ahead and is in a very good position, which is exciting’.