Passivhaus Consultant and Designer, Bristol.  Very Low Energy Buildings.  Domestic and non-domestic.  New build and refurbishment. 

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Bristol, UK


Entries in Passivhaus (17)


New 26 Unit Passivhaus Development in Bristol

Piers has been appointed as Passivhaus Consultant on a scheme to build 26 Passivhaus dwellings on the site of the former bingo hall in North Street, Bristol.  The project team for the development, known as Picture House Court is as follows:

Developer - North Street Investments

Architect - Origin 3 Studio

Passivhaus Consultant - Piers Sadler Consulting

Passivhaus Certifier - BRE Certification

Structural Engineer - Hydrock

M&E Engineer - Hydrock

Project Manager - Aecom

Main Contractor - Speller Metcalfe


Construction work started on site in 2013, but was stopped whilst a new team was appointed for the project. Work is about to start on site agin, and whilst Passivhaus work was done before the original start on site with Origin 3 working with BRE, there is still a lot to be done to confirm the suitability of the designs and performance through PHPP.  

These are relatively complex buildings, so there is a lot of work going into thermal bridge free and airtight design.  Airtightness is clearly going to be the key challenge.  To get up to speed with the project quickly and aid the smooth running of the Passivhaus consultancy Piers was co-located with Origin 3 Studio for about 6 weeks at the start of the work.






Passivhaus Bristol Conference a great success

Bristol Green Capital Place Group, put on a Passivhaus Conference in Bristol on 17 November 2015 entitled:

" How can we build greener and better buildings?  The case for Passivhaus development"

Piers Sadler led the organisation of the event supported by Place Group members and gave a presentation entitled: What is Passivhaus? which is available for download

A packed audience at Arup's Bristol office heard high profile speakers from around the country explaining why their organisations have adopted the Passivhaus Standard and the difficulties, solutions and benefits that they had encountered.  There were great presentations on Passivhaus schools and social housing and on how Exeter and Norwich City Council's have adopted and are encouraging Passivhaus development in their areas.  We were particularly privileged to hear about Exeter City Council's ground breaking leisure centre and swimming pool project, the first of its kind outside Germany.  This building will save about £200,000/yr on energy costs which will pay off the additional costs of Passivhaus in about 12 years.  We also heard about Bristol's much more modest plans which do involve Passivhaus, but we are hoping that events like this will encourage Bristol City Council to up its game when it comes to low energy, healthy housing which works as it's supposed to ie Passivhaus.





Passivhaus and the Law of Increasing Returns

I was recently discussing Passivhaus with an architect with strong green credentials, who argued that the Law of Diminishing Returns meant that Passivhaus was not the mainstream answer to our need to reduce building energy demand.  This got me thinking...

I concluded that Passivhaus turns this law on its head - hence the title of this blog post.

The law of diminishing returns can be illustrated by considering solid wall insulation:

  • uninsulated solid wall of U value 2.1W/m2
  • add 100mm of generic insulation of k=0.03 W/mK and achieve a U value of around 0.3W/m2
  • add another 100mm of insulation and achieve a U value of 0.15W/m2K

So the first 100mm insulation achieves a reduction in U value of 1.8W/ m2K and the second achieves a reduction of 0.15W/m2K.  The first part of the insulation therefore achieves 10 times more energy benefit than the second.  [Of course the second 100mm gives us other benefits around comfort and condensation risk which are a subject in their own right].

But Passivhaus isn't only about increasing the thickness of the insulation.  I prefer to think of the uninsulated house as a leaky bucket.  Mend it badly and it is still full of holes.  Mend it well and it works properly.  The benefits or returns are maximised and increased only when all the holes are completely filled.  This isn't a perfect analogy, but I still believe it is a useful one.

Passivhaus is about attention to detail during design and construction, particularly continuity of insulation and airtightness at junctions.  With the right team these things come relatively cheap.  If we take a similar example but for a new build:

  • 200mm insulation on the wall meets Building Regulations with a bit to spare;
  • thermal bridging at junctions is worth an additional 0.15W/m2K on the U value if the junctions are not well designed (according to SAP - and in my opinion, a useful approximation for this example)
  • air leakage at junctions could be worth the difference between 0.6 air changes per hour (ACH) and, for example 6 ACH
  • based on a house of wall surface area 150m2 and volume 350m3 in Bristol with 68kKhrs annual heating degree hours with the air leakage through the wall junctions accounting for a quarter of the total, the heat loss through the poorly detailed wall is 3885kWh/yr, whilst the heat loss through the well detailed wall is 1612kWhr/yr.  

So paying attention to those junctions, which requires little more in the way of materials, lots more in the way of design consideration and more skilled workmanship results in a 60% reduction in annual energy use.   This is the Law of Increasing Returns in the context of Passivhaus.  





Four Oaks Passivhaus Project in the news

The Passivhaus Trust website featured the Four Oaks Passivhaus project in it's news section.

We are now at Building Regulations submission stage and planning to go to tender in March.  Lots more to be done on detailing the timber frame construction, glazing and heating, hot water and ventilation in coming weeks. 

For more information see projects.







BS10 Passivhaus

@Markleach @georgefergusonx Enjoyed a good meeting with BS10 (Southmead) Planning Group yesterday with @REFurnival. Residents very receptive to #Passivhaus - cheap to run, sustainable, comfortable healthy homes #Bristol.