Heat loss through roof

Kashkai

I was waiting in the car this morning for my kids to come out for the school run when I noticed that on my heavily frosted slate roof, there was a line down from the ridge to the gutter where the old existing house met the new end extension. I surmised that this is where the old double walled gable met the new extension and that there was heat loss from the house up through the double wall where it was escaping through the tiles and thus melting the frost leaving the visible line on the tiles. During the build, I noticed that the original house had only glass wool insulation in between the inner and outer block work for insulation.

Is there a way to eliminate this heat loss? Could I use expandable foam to cut down on this heat loss, i.e. drill holes in the attic at regular intervals along the old gable wall and inject the expandable foam or would this lead to water retention from condensation in the walls and cause more bother?

soldsold

I don't think you would ever see the payback from the cost of the cans of foam at a rennet a go, in any case I'm pretty sure the amount you would inject in before you would throw your hat at it would not be effective. If you could dryline the inside of both walls for about a meter down from the ridge you would stop the heat loss through this wall. Otherwise you will have to live with it. Maybe use a bit more rolled out insulation or draughtproofing to make the rest of the house lose less heat overall, it would most likely be more effective in the long run