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dankelly · 18th March 2010

Ok John, thanks.

I was under the impression though, that as well as sealing my inner room airtight, for maximum TL I should also be making my outer leaf as effective as possible? As an exaggerated example, if my roof were to not be there at all, I would not have a room within a room, but merely just a room. I could beef up walls and beef up the underside of the roof between the rafters but if i then have gaping holes for ventilation then it seems pretty pointless?
As everyone says on here, there is no point in putting 5 layers of drywall on the walls to then only put 2 on the ceiling as the ceiling will let the walls down. So surely by beefing up and making the best of my outer leaf, then the ventilation is going to let the whole isolation down?

Im sure this is one of those things that just has to be accepted, but of my options I am trying to make the right decision for the best possible results. So here is my question. Am I better to :

A) Leave the outer leaf (roof) as it is (corrugated sheet on top of plywood), then double drywall my new isolated, inner ceiling and insulate the void between.

B) Beef up the outer leaf between the rafters, then do the same as (A) with the internal ceiling.

C) Drywall to the existing trusses then do the same as (A) with the internal ceiling, insulating both voids. This creates a triple leaf but there will now be a perfectly sealed room, within a perfectly sealed room, underneath a ventilated loft space. I'm trying to understand the effects of the triple leaf. I know its bad, but is it worse than not having that extra layer of isolation?

Thanks a lot for the help guys.

18th March 2010	#6
dankelly Gear maniac Joined: Mar 2009 Posts: 188 Thread Starter	Ok John, thanks. I was under the impression though, that as well as sealing my inner room airtight, for maximum TL I should also be making my outer leaf as effective as possible? As an exaggerated example, if my roof were to not be there at all, I would not have a room within a room, but merely just a room. I could beef up walls and beef up the underside of the roof between the rafters but if i then have gaping holes for ventilation then it seems pretty pointless? As everyone says on here, there is no point in putting 5 layers of drywall on the walls to then only put 2 on the ceiling as the ceiling will let the walls down. So surely by beefing up and making the best of my outer leaf, then the ventilation is going to let the whole isolation down? Im sure this is one of those things that just has to be accepted, but of my options I am trying to make the right decision for the best possible results. So here is my question. Am I better to : A) Leave the outer leaf (roof) as it is (corrugated sheet on top of plywood), then double drywall my new isolated, inner ceiling and insulate the void between. B) Beef up the outer leaf between the rafters, then do the same as (A) with the internal ceiling. C) Drywall to the existing trusses then do the same as (A) with the internal ceiling, insulating both voids. This creates a triple leaf but there will now be a perfectly sealed room, within a perfectly sealed room, underneath a ventilated loft space. I'm trying to understand the effects of the triple leaf. I know its bad, but is it worse than not having that extra layer of isolation? Thanks a lot for the help guys.