Neil Turner | EBS
In November I attended a series of four half day Passivhaus ‘bitesize’ courses run by The Green Register (TGR), Warm and AECB CarbonLite in Bristol. Based on my career background (previously with Warmcel and now with TGR partners EBS: www.ecologicalbuildingsystems.com) I was fully aware of the typical building envelope insulation and airtightness requirements for Passivhaus construction but wanted to learn more about other aspects and also gain a perspective from other construction professional attendees such as architects and building companies.
Peter Warm delivered the first training session on the principles of Passivhaus construction. Pete very clearly explained the five key aspects of Passivhaus - building shape (form factor), glazing, airtightness, ventilation and envelope insulation/thermal bridging at junctions. What struck me most is the simple and straightforward principles adopted in Passivhaus construction – I had previously imagined that it would be far more complicated and complex and that there would be some major design restrictions and limitations. This is not the case, although some very high performance targets need to be met in terms of building envelope U values and air tightness, additional care needs to be taken regarding non repeating thermal bridging at junctions and also window size and orientation can limit design options.
The second bitesize session from Bill Butcher, one of the directors of the Green Building Store covered some the construction detailing aspects of Passivhaus. As an experienced builder, Bill was able to explain key elements such as how to achieve airtightness (products and construction sequencing), non-repeating thermal bridges at junctions, proven construction build-ups and the correct fitting of insulation in a very practical, accessible way.
Bill brought along lots of samples of building materials and products for us to look at which further reinforced the really practical aspects of this training course.
What I gained most from this section was the relative flexibility in construction types that can be used for Passivhaus construction although Bill emphasised the need for careful planning and sequencing during the construction phase. Based on my experience in the field I have found that running practical site toolbox talks is an invaluable way of educating contractors in these concepts – something that is sorely lacking in the UK. (see http://www.ecologicalbuildingsystems.com/UK/training for information on installer training courses)
Alan Clarke, a building services engineer, provided the third session. Building Services for Passivhaus. This is the area where I had the least amount of previous knowledge and experience and so I was hoping for a more in depth understanding of ventilation and water heating systems (which types to use, where to locate in a building etc). Alan’s main focus was placed on mechanical ventilation with heat recovery (MVHR) systems, hot water and heating. I was fascinated by aspects such as optimum places to store MVHR, water tanks and hot water combi units and how much heat can be lost from water pipes if they are located too far away from the heating units.
One of the most intriguing parts of the first three courses were the ‘break out’ exercise sessions where delegates were able to work in groups with each other to apply the knowledge learned in each session. One of the projects where achieving Passivhaus standard would prove to be difficult was a proposed extension, where the initial design involved having a large square meterage of glazing, but facing north. Another project was a new build block of flats and much of the discussion focussed on whether to have a communal MVHR system or several individual ones.
I found the fourth and final ‘crit’ session extremely informative where many of the delegates brought in drawings of their own projects and we discussed ideas as to how some design modifications could be made in order to achieve the Passivhaus standard. The range of delegates’ projects was diverse, from the design of a new school (perhaps an awkward shape with not such a good form factor), an extension to an elderly persons care home (which would have to have most of the windows north facing) and a new block of flats. The dilemma for this project was whether there should be individual MVHR units for each flats or a communal MVHR unit. What was particularly useful was that the ‘crit’ session allowed the delegates to apply some of the principles discussed in the Bitesized sessions to real projects. It was clear from the discussions amongst delegates that they had absorbed and could already apply the knowledge learned in the previous three sessions.
The quality of the material presented by the speakers was excellent and all of the speakers were extremely knowledgeable and experienced in their particular spheres. These Passivhaus Bitesize training courses are a must for anybody who is interested in Passivhaus or other types of low energy construction projects but may not be able to attend the full two week Passivhaus training sessions.
Indeed this training would be a valuable tool for anybody involved in construction in general - many of the principles discussed, if followed by the whole industry, would lead to a dramatic improvement in the overall quality of UK construction, reduce energy consumption in buildings and help to mitigate against climate change.