Achieving energy efficiency & preserving historic buildings... to good to be true?

Joseph Little will be addressing this challenge in the lecture organised by The Green Register in London on 27th June (see pages of brochure below).

The talk flows from research work that he and his team have done alongside Fergal McGirl Architects (focusing on conservation) and IHER Energy Services (focusing on BER and energy systems). The title of the talk surely sets out one of the challenge of our times for the built environment, because most domestic energy retrofit rarely involves construction professionals, the value of what's present is often under-rated, and while the replacement (for instance a window) may far perform better Day 1 it often results in a decline in architectural quality and may not last as long. We need to be clear not only on what we hope to gain (in this case energy savings) but what we could lose.

Looking at the two photos of a Dublin 1930s house below we can see that the timber of the canted bay window's mullion (exposed by cutting away a section) is composed of three sections of high quality, slow growth pine. It is clear that in 2014 (when the cut was made) that the timber was still in the same sound condition as it was in 1930. The steel bar or other structural support that was assumed to be present is nowhere to be seen: with a shock one realises the bay window itself is a key structural element taking the vertical load. That is to say the main frame and mullions of the first floor bay window are transferring the load of the gable roof, the gable to ground. The ground floor bay window also carries the load of the first floor window and the spandrel: and it has done so without a problem for 84 years. In replacing these windows the builder now has to hold the roof and spandrel in place while the windows are being removed and provide new structural supports before installing new windows: two unforeseen additional costs. If only the sashes had been repaired or replaced (either way upgrading to high quality double glazing) and the robust main frames and mullions retained!

In general we propose that measures be considered that make a traditional (previously uninsulated) dwelling much more energy efficient than it is now (i.e. 50-70% more efficient) but resist making the kind of changes that are needed for super-low energy retrofits (i.e. 70-90%). By doing so we can save heritage and architectural character but also emodied carbon and energy. Ironically in doing so we may also be retaining features that will outlast the measures that would have replaced them otherwise: while that may seem a crazy thing to say - consider the example above: how long could that 1930s bay window have continued to perform if it hadn't been sawn and removed. Will the aluclad or uPVC window that replace it last even 25 years?...

It's time we spent more time focusing on the full range of values that existing dwellings and their components have and propose measures that, whenever possible, align with their inherent functionality and characteristics: in historic dwellings new may not be better at all. 


Tuesday, June 17, 2014