A self build house project diary
by Oliver Cannell
Tuesday 6th January 2015
(published/edited Tuesday 16th February 2016)

Getting picky with the house insulation

Maximising the roofing insulation before the plasterboard is installed.

The house has been designed and built to maximise the benefit of sunlight coming in through the large south-facing windows, which will warm the house up during the day. Combined with the copious amounts of wall, floor and roof insulation that has been installed, to retain the heat after sunset, the overall heating energy bills should be quite low.

So, you can imagine how disappointed (and surprised) I was to see 6-8 inch screws being used to construct the roofing layers (boarding and insulation foam), so that 2 inches in length of each steel screw is pertruding into the house. As this is a warm-roof structure (ie. there is loft space between our heated roofs and the outside world) this means some heat will be lost directly through these screws. Although it's only a small amount, it seems crazy to give heat such an easy chance to escape.

In much the same way as the wall ties in the exterior walls - which I swapped from standard stainless steel to GRP (glass reinforced plastic/resin) which have a much lower thermal conductivity value - I wanted to find a way to reduce the heat transfer through the roofing screws.

So, as there are piles of insulating foam left over and laying around the building site, I thought we could make use of it - instead of putting it straight into landfill - to help insulate the roof. We've been cutting it up into approximately 2 inch square chunks so they fit nicely over the end of each screw thread. As you can imagine and see from the photos, there are a few hundred screws pertruding through whole roof, so it's taken a few days to get them all done, during the evenings.

I'm hoping this will make a difference to the efficiency of the heating - although tiny I'm sure - but every little helps as they say. Especially over the whole lifetime of the property.

Next entry: More 1st Fix Plumbing and Electrics (Thursday 8th January 2015)

Previous entry: 1st Fix Plumbing and Electrics (Tuesday 6th January 2015)

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