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Having a loft conversion done. I have queried the amount of insulation in the dormer roof with my builder and he said it is enough, because there is more on top plus another 25mm to go on the ceiling. I looked up some building regs / U value info for wooden dormers, and it suggests a minimum if 120mm, so if there is 50mm on top, this will be a total of 125mm, and "enough". (I guess the roof is a bit like this: http://www.acutecarpentry.co.uk/our-services/grp-roofing/ - I asked for fibre glass instead of felt).
But, there seems to be plenty of room for more, and still leave a space for 50mm air gap - see photo. The board there is 50mm, and the space from the bottom of the board to the top is 170mm, so if I had 100mm in there, there is still lots of space for ventilation. This will give 175mm insulation in total (assuming there is 50mm above that I cannot see).
Should I ask to have more - I will have to pay for the extra (he said only if building regs request a change, it will be free), but I am happy to pay for a few more boards, or thicker boards, if it means a warmer future with lower heating bills. It just seems a bit silly to not put in as much insulation as possible. But, am I being silly to think that?
But, there seems to be plenty of room for more, and still leave a space for 50mm air gap - see photo. The board there is 50mm, and the space from the bottom of the board to the top is 170mm, so if I had 100mm in there, there is still lots of space for ventilation. This will give 175mm insulation in total (assuming there is 50mm above that I cannot see).
Should I ask to have more - I will have to pay for the extra (he said only if building regs request a change, it will be free), but I am happy to pay for a few more boards, or thicker boards, if it means a warmer future with lower heating bills. It just seems a bit silly to not put in as much insulation as possible. But, am I being silly to think that?
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