I need to clear up a myth. A Passivhaus is not just for rich people. And actually a small, simple Passivhaus could be a perfect solution for people on really low incomes.
“A building that demands as little as possible” Adam Dadeby
Passivhaus certified houses are affordable to live in. They can cut space heating energy use by 80% or 90% without sacrificing comfort or fresh air. Usually these will be new homes, but there are a few examples of people who have refurbished older housing to Passivhaus standard. This is the story of Adam Dadeby and his wife Erica, who turned an ordinary 40 year old house into a fully certified Passivhaus.
After studying at The Centre for Alternative Technology in Machynlleth, Adam and Erica decided to refurbish their existing house instead of building a new passivhaus. It was an ambitious decision, made on the grounds that it seemed more sustainable to do this than start again from scratch and that it was important to pioneer this approach. They made a start in 2009:
“Week two has been quite eventful. The old windows are out and much progress made in digging trenches for the external insulation and preparing the foundation for the new build element to the side of the house.
All (I hope) of the shortcomings of the existing building have now been exposed and this week I have found myself questioning why we are bothering to refurb and not demolishing what is left and starting again. If we had chosen to demolish it, we would have been able to do away with many hours of difficult design work. The problems of thermal bridging between the ground floor concrete slab and the structural walls would have gone away in an instant.”
For any Passivhaus build, the design choices focus on minimising energy / house fuel requirements, but this is balanced by the budget and other external constraints. In a refurb, the external constraints are greater, because the existing building isn’t designed for purpose.
For example, the original floor in Adam and Kate’s house consisted of pine boarding, felt underlay, 70mm of screed, 150mm of reinforced concrete slab and a hard-core base. To raise the floor design to Passiv standard, they considered removing the entire concrete slab to create the space needed for decent insulation. However, the added cost and risks of structural damage led to a compromise in which the concrete stayed, whilst the screed was replaced with 80mm of highest performance insulation, 20mm of wood fibre insulation and a wooden flooring with a total thickness of 17mm. This compromise worked, but it increased the finished floor height by about 20mm and a new build could have done better at less cost.
This house was only the third in the UK to be refurbished to Passivhaus standard and has made quite an impact, winning awards and attracting plenty of interest. Adam points out that, rather surprisingly, the financial odds are not yet stacked in favour of refurbishment: you can claim back the VAT on a new build but not on a refurbishment. That’s another constraint we need to bear in mind until the law can be changed.
A simpler, cheaper, but still very worthwhile option for people who are currently building or refurbishing to a higher energy performance, might be to opt for EnerPHit or AECB Silver. This is still above and beyond minimum regulations for energy performance … a sort of Passivhaus on a budget.
Basics for energy saving
- Concentrate on the building itself: windows, walls, floor, roof and the junctions where they meet – “fabric first”
- Get the insulation right and that means nice and thick and with no gaps, because gaps let the whole insulation thing down
- Reduce (and test for) air leakage, make sure doors and windows are well fitted and that the manufacturers made them up to spec
- Eliminate cold-bridging i.e. places where poor thermal insulators such as concrete slabs or metal joists come through the insulation layers
- Ventilation for fresh air without the heat loss in winter
Adam Dadeby kindly helped in the preparation of this article. The build team are pictured above and their experiences during the project lead Adam and the architect on the scheme to co-write The Passivhaus Handbook. As clients, Adam and Erica wanted to try Passivhaus before committing to it. At the time there was nowhere to do this, so they offer Passivhaus bed and breakfast accommodation in their home.