Wednesday, 18 September 2013

Why aren't building regulations based on the PassivHaus standard?

Last week I attended a seminar on building homes and other buildings to the Passivhaus standard. This is an extremely rigorous energy efficiency standard for buildings which is now common in Germany and Austria but there are examples in the UK too [1]. In parts of Belgium and Germany the Passivhaus standard will soon be the norm for many buildings: in Freiburg it is required for residential buildings, in Hamburg only Passivhaus homes receive municipal subsidy, in Brussels it will apply to new buildings of all types from 2015 [2]. Passivhaus homes are certainly cheap to heat. A gas heated PassivHaus standard home of 70 m2 could be heated for only £42/year (assuming 4p/kWh) [3]. So what is this standard and how does it compare to our own building regulations? Should we have it here too?


There are relatively few Passivhaus homes in the UK but we saw several examples in the seminar which debunk some of the reasons usually given against the Passivhaus standard.

  • Passivhaus homes are not necessarily expensive to build - for example two developments of affordable housing by Hastoe Housing Association (at Wimbish and Ditchingham) have cost only 12% and 6% more to build than the current normal Code for Sustainable Homes (CSH) level 4. The Ecological Building Society gives preferential rates to Passivhaus new build projects [4].
  • Passivhaus homes are comfortable to live in (as demonstrated by monitoring of temperature and internal humidity at Ditchingham) [5].
  • Passivhaus homes don't have to use particular materials and can be made to fit into most landscapes. The Ditchingham estate is next to listed buildings. They houses are faced with brick and they even have 'chimneys' although these are not actually connected to fireplaces - they act as inlet and outlet for the ventilation system. (See picture here). In Yorkshire there is a Passivhaus faced with stone (picture here).
On the other hand there are some truly horrific stories about Passivhaus homes using more energy than they are supposed to and even making people ill. This is usually because someone has cut corners during the building stage and not stuck to the design specification.A particularly bad case in Belgium was built without the specified airflow vents: not surprisingly problems quickly developed with high moisture and poor air quality [6]. The frequency of failiures like this should diminish as the standard becomes better known and understood by the industry. In the mean time, you had better make sure your design team keeps a close eye during construction.

Even though everyone wants energy efficient homes comparing the Passivhaus standard with building regulations is like comparing apples and oranges.

  • The Passivhaus standard specifies energy use whereas our CSH standard is based on carbon emissions. (This encourages UK developers to install gas heating because it is low carbon at the moment compared to electricity, thus locking us further into reliance on imported gas supplies.)
  • The CSH standard allows some carbon emissions to be offset by generating renewable electricity from solar panels. This is arguably not a sustainable solution because no amount of PV panels is going to make much of a dent in your electricity use on long winter evenings - and the National Grid has to handle the problem of balancing supply and demand through the days and seasons. There is nothing to stop you putting PV panels on your Passivhaus home but it won't help you get the certification.
  • The Passivhaus standard gives a limit to the energy use per unit of floor space whereas the CSH standard is relative to the notional carbon emission of a 2006 house of the same size and shape. The trouble is that long thin houses, L-shapes and other forms tend to have more envelope to lose heat through for the same size of house. Passivhaus homes tend to be boxy because it is difficult to achieve the standard any other way. If you were given the choice between an amusingly rambling family house and a box which had a quarter the energy bills which would you choose? And would you give the same answer in 50 years time?

Not surprisingly it is very hard to reach the Passivhaus standard by retrofitting an existing house, though it can be done, even to a draughty old Victorian terraced house as demonstrated by Green Tomato Energy - see the video here. This sort of 'deep' renovation is very expensive and recognising this the Passivhaus Institute has set a slightly less stringent standard called EnerPHit for refurbishments. The limits for air tightness is 1.0 air changes per hour compared to 0.6 and the limit for heating demand is 25 kWh/m2/year compared to 15. It is still a pretty good standard.

It concerns me that our housing stock is becoming more and more polarised, with many old homes effectively being left out of normal building regulations. The exemptions are not just for listed buildings - they include anything in a conservation area or of 'traditional construction' which includes all buildings with solid brick or stone walls) [7]. The exemptions could include 40% of our current housing stock. It isn't that you can't upgrade that stock, just that no-one will badger you to do so. Are today's conservation areas going to be tomorrow's slums?

Instinctively I tend to support the highest achievable energy efficiency for all new buildings but our carbon based building standards do have one redeeming feature. As from 2016 all new homes are supposed to be zero net carbon but some of the savings can be through 'allowable solutions' which can be off-site carbon saving projects - potentially that could mean carbon saving retrofits to other buildings [8].

The Passivhaus standard demonstrates how efficient buildings can be with careful design and build quality. However, if our goals are to save carbon emissions and reduce fuel poverty across the whole building stock, arguably the flexibility in our current building regulations has some benefit too.

[1] Graph of growth in numbers of Passivhaus standard houses across Europe from www.pass-net.net
[2] Passivhaus legislation International Passive House Association
[3] The Passivhaus Standard (www.passivhaus.org.uk)
[4] Ecology Passivhaus Mortgages (www.ecology.co.uk)
[5] Ditchingham Passivhaus (www.passivhaustrust.org.uk)
[6] Belgium report raises questions on Passivhaus (CM magazine)
[7] Energy efficiency and historic buildings: application of part L of the building regulations to historic and traditionally constructed buildings (English Heritage)
[8] New Build Homes (UK Green Building Council)

5 comments:

  1. www.inbuilding.org are running a free online Q&A on Building Regulations for architects and architectural professionals. Come and have a look.

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  2. I live in the ditchingham passivhaus and my bungalow is freezing cold, my electric bill is through the roof and i have had nothing but problems, in really not happy, they cut corners and take ages to fix things, not happy :(

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    1. I'm very sorry to hear that. Is the temperature monitoring ongoing? Can you be specific as to how they have 'cut corners'. Do you think this is a fundamental design problem or just shoddy workmanship? The quality of work can make a huge difference (see also http://energy-surprises.blogspot.com/2013/11/what-can-go-wrong-with-mvhr.html)

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  3. This comment has been removed by a blog administrator.

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  4. People can save on their energy bills by getting their house and organizational buildings assessed by a certified BER assessor .

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