Spray foam insulation in a loft

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Hi,

I've purchased a 1915 house and look at insulation. I've already started to replace the loft insulation but I was wondering about spray foam insulation on the inside of the roof but not sure what needs to be done first.

I've attached a couple of pictures showing the make up of it, not sure if it needs a breathable membrane before the spray foam and whether it's better for me to do this or the insulation company.

Many thanks
Mark
 

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Don't do it, the wood won't be able to breath, risks damp and rot. And you'll never be able to check the timber in future either.
 
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Spray foam is about the worst thing you could do to that roof. It won't let the wood breath and you won't know you've got a leak until the rot is so bad the whole roof needs replacing.

Secondly, if you insulate the underside of the roof all you are doing is allowing heat to escape into the loft space. The insulation should be on the top of the ceiling of the room below the loft so that the heat remains in the house, not in the loft space.
 
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Thanks for the replies.

I did forget to mention that we will at some point be extending into the loft so will have to do something at some point.

Looks like it's a big no no for spray foam insulation then.
 
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Thanks for the replies.

I did forget to mention that we will at some point be extending into the loft so will have to do something at some point.

Looks like it's a big no no for spray foam insulation then.
Worry about it when you are living up there. (y)
 
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