Dormer Crawl space draughts and insulation

boatbuilder

Hi, I'm looking for some advice on how best to (a) insulate and (b) draft proof my house around the crawl space area.

I've attached a drawing of the crawl space in my house.
Its detached, built in 2005 and very drafty (shocked when I realised how badly insulated it is)

Some details:
All plasterboard is simply 12mm paper-backed.
Knee wall has fibreglass insulation pushed between the studs (75mm thick at a guess)
Ceiling joists have no insulation at all.
Rafters in the crawl space area have kingspan rigid insulation pushed between them (not very well fitted with some gaps along edges, held up roughly by nails)
Plywood floor in crawl space nailed down with nailgun.
I've removed one sheet of plywood to see whats under there and I can see right out to the pvc fascia and soffett. So there is massive cold air coming in there through the vents.
The arrows show where the cold air is going, can feel it coming up through the floor in the upstairs rooms, also blowing in around sockets etc in the upstairs rooms.

Just wondering where I go from here?
Have applied for SEI insulation grant but want to find out the best way to do this before I approach a contractor (or maybe do it myself to make sure its done properly this time)

boatbuilder

Anyone have any ideas on this?

mikehunts

We had the same issue as this, our house was built in 2004. We got the grant for the beads in walls and insulation in attic and crawl spaces.
They insulated all along the crawl space floor, but did not cover the vents for air.
There was the rigid white insulation on the walls but the insulated over that again with the rockwool. Big difference i have to say.

meercat

BING ......... BONG

PADDY147 TO RECEPTION PLEASE ,PADDY147

http://www.boards.ie/vbulletin/showthread.php?p=71765022

boatbuilder

meercat wrote: »

BING ......... BONG

PADDY147 TO RECEPTION PLEASE ,PADDY147

http://www.boards.ie/vbulletin/showthread.php?p=71765022

I know that spray foam is the best of the best but is way beyond my budget even with the grant.
I was thinking more along the lines of fibreglass or rock wool. Is it worth trying to retro fit vapour barriers or other breathable membranes? And if so, where should they go?

paddy147

meercat wrote: »

BING ......... BONG

PADDY147 TO RECEPTION PLEASE ,PADDY147

http://www.boards.ie/vbulletin/showthread.php?p=71765022

Thanks.:)

MicktheMan

boatbuilder wrote: »

1. I know that spray foam is the best of the best but is way beyond my budget even with the grant.
2. I was thinking more along the lines of fibreglass or rock wool. Is it worth trying to retro fit vapour barriers or other breathable membranes? And if so, where should they go?

1. Is it? I don't want to derail this thread but, imo, the jury is still out on this form of airtightning/insulation.

2. Insulation generally does not cut out draughts. It role is to slow down the conduction of heat through solid materials such as walls. Air will still make its way around the insulation and into the house through gap/cracks if no air barrier is installed. I have attached below where the insulation (yellow) and air barrier (red line) should be installed.
Dormer attic airtight & insulation diagram.png

Irish Steve

MicktheMan wrote: »

1. Is it? I don't want to derail this thread but, imo, the jury is still out on this form of airtightning/insulation.

The jury is back out again on things like greenhouse gases, among other things, but I've not seen any reduction or removal of the taxes that were supposed to encourage the use of "green" fuels, whatever they are, they seem to be in very short supply here in Ireland, and the few that are about are surprisingly close in price to the non green alternatives, or even dearer, which when the price of conversions is considered, makes the total cost of being green a lot more than most can afford right now.

2. Insulation generally does not cut out draughts. It role is to slow down the conduction of heat through solid materials such as walls. Air will still make its way around the insulation and into the house through gap/cracks if no air barrier is installed. I have attached below where the insulation (yellow) and air barrier (red line) should be installed.

From reading the thread that's been linked, the installer would have to be pretty incompetent for this system not to provide a very good level of air movement restriction or protection. No, it's not impermeable, but it for sure does present a serious barrier to draughts and the like because of the manner of application and the way it then expands to close up gaps.

If I could afford it, I'd be looking to put something like this system in, but right now, it's not an option, even though it would save some serious money. Such is Life.

boatbuilder

I'm thinking of more along the lines of fitting a polythene vapour barrier at the back of the existing plasterboard and up and down over the joists, sealing it as much as possible , then insulating over that with a decent thickness of fibreglass.
Problem I can see with that is there would still be a draft blowing in the vents and into the insulation itself....Would a breathable membrane on the cold side if the insulation fix that?