Chris Parsons from Parsons + Whittley architects shares his experience of the costs behind Passivhaus.
Interview with Chris Parsons
Chris Parsons from Parsons + Whittley architects has always had a focus on making buildings as efficient as they can possibly be. With the issues around global warming and trying to reduce carbon emissions, this is why they found a great synergy with Passivhaus.
Achieving Passivhaus in Larger Buildings Can Have Less Impact on Cost
The larger the building, the more efficient form factor you have and the less impact there is on cost.
However with smaller buildings, such as the domestic dwellings being delivered by Parsons + Whittley in the social housing arena, there is always an impact on cost.
N.B. This episode (from this point onwards) is specifically talking about smaller residential buildings.
Costs Will Increase Because There's More in the Fabric of the Building
There are practical reasons why a Passivhaus will cost more than a traditionally built house:
- There is often a lot more insulation being used
- Windows and doors are much better specification, and hence cost more
- The ventilation strategy often uses mechanical ventilation with heat recovery (MVHR)
- Addressing airtightness will require certain additional products
On the flip side, there is likely to be a simpler mechanical infrastructure in the house because there will be a reduced heating requirement.
There are Big Benefits for a Comparatively Small Extra Cost
By investing a little extra to create a building that reaches the Passivhaus standard, there are numerous advantages:
- The building will use less energy, thus reducing running costs. This also means there are fewer carbon emissions.
- The building will be more comfortable and have a healthy environment (improved air quality).
- The building will cost less to maintain because it has been built to a higher quality.
Legislation is Needed to Improve the Quality of All Housing
If the capital cost of housing is divorced from the running costs (as is currently the case in the UK) there is little incentive for developers to build to a high quality, particularly if they can already sell their houses! For this reason Chris believes building regulations should be tightened up.
There's a 15% Uplift for a Passivhaus Scheme
Chris shares information from his Passivhaus schemes.
This was Chris' first scheme, 14 dwellings in Essex. At the time the construction industry (in the UK) hadn’t delivered Passivhaus in a multi-unit arena before and as a consequence procurement was a challenge. A cost exercise with another 14 unit (Code for Sustainable Homes – Level 4) revealed that they paid a 12% premium to reach Passivhaus standard.
Wimbish Passivhaus scheme in Essex
The Ditchingham scheme was built at a time when the housing market was going through a downturn. With the same contractor they were able to secure it for a 6% increase.
However, over the course of the project they realised that perhaps this was more to do with negotiation than actual cost.
Ditchingham Passivhaus scheme in Norfolk
Burnham Overy Staithe
More recent schemes have generally been shown to be around the 12-15% uplift.
Burnham Overy Staithe Passivhaus scheme in Norfolk
Chris concludes: “At the moment we are around about 15% more for a Passivhaus scheme over and above the standard we would otherwise deliver.”
There is a Cost Attached to Risk
Chris explains that there is a difference between cost and price.
A contractor will always build in a contingency to cover the unexpected (and in the early days Passivhaus was an unknown!). So even if the contractor believes the cost is X, they will assess the risk and add Y.
This means that the price to the client will be X + Y.
Chris believes that if the client were prepared to take on the risk, they would reduce their costs in the long run.
Embracing Simplicity Will Keep Costs Down
What Chris likes about the Passivhaus standard is that it comes down to a set of numbers.
He says: “As a designer you can start with a pencil sketch, run it through the software [PHPP], make sure that you are somewhere near those numbers and then continue to develop the scheme. Every time we’ve done that, simplicity has been the easiest way to achieve the target.”
This is about simplicity in terms of detailing and how the space is used.
A Passivhaus is Worth More in Europe
If there is demand for buildings that meet the Passivhaus standard and people recognise the value of it, then it may get to the stage where people are prepared to pay a premium for it.
In parts of Europe this is already the case, where that premium is 3 – 5% more.
Chris concludes: “If I was going to pay some extra money for a Passivhaus, I would want to be sure it was one so I would like to see certification adopted as a means of quality control and a means of quality assurance.”
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