Spray Foam Insulation on Converted Attic

JMR

Hi,

Looking for some independent advice on this please.
Our attic is converted and in use as a bedroom but quite cold in the Winter, so looking to get it insulated as the builder who did the conversion did not insulate it properly (before we owned the property)

A spray foam contractor has quoted us for open cell spray foam insulation.

The thing I'm not so certain about is that he maintains the slope from the outside of the house up to where it merges with the ceiling inside the attic is all that needs to be insulated.
I was expecting them to spray up between the ceiling and the outer felt, right up to the apex of the roof or as near as they could get to it?

He says when the foam expands that the ceiling might cave in, if they were to do this!

He also says that what he is proposing is a perfectly acceptable solution as no heat is lost directly through the top of the roof, if he prevents cold air coming in from the eaves the attic will no longer be cold.
Sounds a bit odd to me, any opinions?

Thanks

BryanF

Sounds a bit odd to me aswell.
Insulating existing dormer bungalows/attics is pain full.

Take of the ‘sloped’ plasterboard, install vent cards to ensure continuous ventilation from eaves to ridge, install foam from eaves to ridge and re-slab. VApour barrier/air-tightness continuity will be difficult. Unless you fancy taking down korenplaster board or roof tiles, you may aswell foam the whole roof surface area.

Ensure you leave vent space between felt and insulation. you may need roof vents. Don’t trust installers, ring and seek consultation from product suppiler, if their not bothered seek third party advice from arch or Engineer.

Calahonda52

The spray foam guy has no idea really. You had best not progress any further with him.
..
As BF says its a very tough project to retro insulate a attic conversion.
Two options are either rip out what is there along the slope and flat part inside or else work from the outside:
strip off tiles, batten, felt, work from outside,with an A/T layer on the inside, insulation and replacing felt with a breathable windproof membrane, battens and counter batten and tiles.

This wont work if its a semi D
Look here for ideas
http://www.ecologicalbuildingsystems.com/Ireland
including running insulation over rafters on outside

in passing: is it now a 3 storey with the attic

JMR

Thanks for the replies guys, much appreciated.
the suggestion to remove ceiling and walls, install insulation and re-do the ceiling and walls was our first thought but a quote of nearly €9k from a builder put that to bed!
The builder himself, suggested a simpler and more cost efficient solution would be the spray foam route and would provide a result that would be good enough for our needs at less than a quarter of the price.
I don't know anything about insulation, as you can probably gather, so just wanted to be sure I wasn't taking on a total cowboy

Cheers

Calahonda52

JMR wrote: »

Thanks for the replies guys, much appreciated.
the suggestion to remove ceiling and walls, install insulation and re-do the ceiling and walls was our first thought but a quote of nearly €9k from a builder put that to bed!
The builder himself, suggested a simpler and more cost efficient solution would be the spray foam route and would provide a result that would be good enough for our needs at less than a quarter of the price.
I don't know anything about insulation, as you can probably gather, so just wanted to be sure I wasn't taking on a total cowboy

Cheers

You are, per your first post