Cold walls and heat loss

[roofless]

Hello. I own a 1930's metal-framed, asbestos tile roofed, single-walled bungalow. Yes, exactly. Walls are cladded with some rendering on mesh outside, and plasterboarded inside. Last winter really exposed how poorly it retains heat. External walls are very cold, and I'm hoping to get some improvement with 60 mm phenolic foam backed boards stuck straight onto the existing boards on selected walls. Is that likely to help appreciably?

Some of the coldest spots on external walls seem to relate to flaws and gaps in the rendering around windows and gaps behind the bottom edge. What would you suggest as the best filler and the best way to get it into gaps as far as possible?

Sorry to ask well-used questions: I've read a lot of threads, but I thought maybe someone else might have overcome some of the issues of this type of house.

Any advice gratefully received.

 

[ajrobb]

Hello. I own a 1930's metal-framed, asbestos tile roofed, single-walled bungalow.

Sounds like a prime candidate for redevelopment! I'd be surprised if buyers could get a mortgage.

If you only insulate selected walls, you'll still need to keep the place well ventilated to prevent condensation on uninsulated portions. It would be better to insulate all external walls and include a vapour control layer (VCL). This allows you to reduce the ventilation to just what is needed by the occupants. You'd need at least 20mm of insulation behind the VCL in order to prevent condensation.

You might want to consider external insulation as this will also get you a new rendered exterior without losing space inside. The original walls and metal frame would then be kept warm and dry and you won't need a VCL inside.