Insulating 1970s dormers

Hi everyone. I’ve never posted on a forum before but I'm having huge difficulties insulating our house and hoped someone here can please help me with some good advice?

Our 1970’s house has a large dormer on the front and on the back, each spanning 3 rooms in width. Internal rooms have a dwarf wall, part sloping ceiling and part flat ceiling. The dwarf walls are silver-backed gypsum board on 75mm timber. The roof joists are 100mm deep and I have a non-breathable roof lining. There is currently no insulation in the walls, floor or roof timbers and none in the loft, which the previous owner has chip-boarded over with approx. 25mm glass wool underneath. This means I have a long void running the entire length of the house on each side, behind the walls which is very windy and cold. Wind blows through the tiles and in where the soil pipe exits the roof and this chills the walls, floors and ceilings. I can access the void in some places through storage cupboards, but there is a large part I can't get to because it's too narrow to crawl down.

My problems started when trying to fit 75mm Celotex between the timbers of the dwarf wall. I started in the storage cupboard because I could reach this part and thought I would remove plasterboard in other rooms later to access the parts I couldn't reach. Problem is there is such a small space to work in, none of the timbers are consistent, there is a soil pipe, plumbing and wonky bits of timber that hold electrical sockets in place. There are so many different angles and impossible places to reach that I can’t fit it accurately enough. I was planning to use 50mm Celotex between eaves roof joists, leaving 50mm ventilation behind. Also planned to put glass wool between and over floor joists in the eaves and stop the wind blowing between the joists with some sort of barrier at the ends.

My worry is that if the Celotex isn’t fitted properly it will be useless. Can anyone recommend a better approach or what materials they would use and where? Multi foil? Glass wool building slabs etc?

Cheers.

 

I had a similar problem when friction fitting celotex to my dwarf walls in my bungalow. In bits with good access I just oversized and trimmed "on site" to fit. In other bits I deliberately undersized them by 10-20mm and foamed them in with minimum expansion expanding foam.

Have to say that it still expanded a fair bit and wear old clothes and gloves!

Hope this helps

Graeme

 

Thanks Graeme - Sounds like a plan. I was doing the same with oversizing and trimming on site. I will definitely try cutting the fiddly bits undersize and use some foam to fill the gaps. There is hope!

 

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