Insulation

Insulating a cold loft with rigid insulation boards.

Anonymous user 28/02/2024 - 3.58 PM

Good morning all. So, state of play is, that I have a flat that was built somewhere around the 1920/40’s. It was Originally the back end of a mid terraced house (with 2 exposed external walls) which was then converted into 2 flats which I’ve owned for 6 years, rented out for 5 and lived in for 1. In the last 12 months I have ripped out and replaced every part of what I originally bought and turned the place into a beautiful livable space. However, the last 2 winters have thrown up some issues with regards to keeping the place stable and warm. Last year was hellish, so investigating the cause of the chillyness revealed just 100mm of old glass fibre insulation in the loft, in places none at all, so 200mm was added. All double glazed units were replaced with thermo efficient planetherm glass, front door replaced with modern upvc item, t&g inside front door had zero insulation at all and so was celotex’d and over boarded. Job done!! (Or so I thought) The flat is heated by smart electric rads so no central heating. This is the part where I could find no info on whatsoever but was advised should be ok to do. I Decided to reinulate the loft space as things were still pretty chilly down below, noticeably better considering this winter has been a colder one. I Purchased 70mm celotex/kingspan and removed the 100mm of old glass roll, cut the insulation boards to fit between the joists and laid flat to the ceiling boards, the 200mm was then laid over the top, I have only done a 3rd of the length of my pad so far and a little tester last night seems to suggest that the place is now colder than what it was before. The walls were certainly chillier to the touch too. The walls are pretty thick with a cavity that has NO insulation, my pitched roof is pretty low too which means that I have curved edge ceilings on both sides of the outer perimeter walls. The insulation boards were run up to the point where the the board runs down to the soffit/fascia board ventilation, and a little earth wool tucked in those little voids to allow ventilation but also stop heat from being lost in those areas. At this point in time I’m now slightly nervous that I have decreased the thermal efficiency of my pad and quite possibly opened up opportunities for condensation/mould growth to form because of hot internal warmth meeting cold external walls. I think I may have just undone what I set out to do so really would like some good solid advice from an insulation expert on the best way to achieve a more thermally efficient pad & roof space given the type of property that I have. I will also add that my window reveals get bloody freezing as the cavity walls and window sills below have no insulation and therefore do cause a condensation/blackmould issues despite using a dehumidifier. Any advice is greatly welcome. Thank you.