insulating my attic rafters

ajw08

This is a very basic question as I'm a bit clueless! I am thinking about turning my attic space into a bit of a man cave(dart board, tv, etc). The attic floor is already insulated and boarded but between the roof rafters isn't. The space between the rafters is 350mm and they are 150mm deep. I'm looking at using 150mm earthwool. Will this be ok? Do I need to do anything else apart from just putting it between rafters and plasterboard over? The house is a 7or 8 year old semi detached.

spcw

I'm no expert but there are different roof types (cold roof) and some cannot be sealed or filled in or the timbers will rot. I would get advice from the builder or an engineer

BryanF

ajw08 wrote: »

This is a very basic question as I'm a bit clueless! I am thinking about turning my attic space into a bit of a man cave(dart board, tv, etc). The attic floor is already insulated and boarded but between the roof rafters isn't. The space between the rafters is 350mm and they are 150mm deep. I'm looking at using 150mm earthwool. Will this be ok? Do I need to do anything else apart from just putting it between rafters and plasterboard over? The house is a 7or 8 year old semi detached.

You need to leave at least a 50mm gap for ventilation underneath the felt with ideally some tile/slate vents at the ridge and ensure vents are open to the eaves. fit 100mm pir insulation between the rafters and a vapour barrier taped & sealed underneath, then plasterboard.

ajw08

BryanF wrote: »

You need to leave at least a 50mm gap for ventilation underneath the felt with ideally some tile/slate vents at the ridge and ensure vents are open to the eaves. fit 100mm pir insulation between the rafters and a vapour barrier taped & sealed underneath, then plasterboard.

Thanks for the response.
So, rafter vents the length of each rafter? Do I need to use pir insulation instead of earthwool?

BryanF

ajw08 wrote: »

Thanks for the response.
So, rafter vents the length of each rafter? Do I need to use pir insulation instead of earthwool?

If you go with earth wool you might want to add more insulation underneath

ajw08

BryanF wrote: »

If you go with earth wool you might want to add more insulation underneath

Sorry, but by underneath where do you mean? I'm just thinking the earth wool because it is reasonably cheap.

BryanF

ajw08 wrote: »

Sorry, but by underneath where do you mean? I'm just thinking the earth wool because it is reasonably cheap.

ok back to the start again

I am thinking about turning my attic space into a bit of a man cave(dart board, tv, etc). The attic floor is already insulated and boarded but between the roof rafters isn't.

will this space have a stairs and will it be heated?

ajw08

BryanF wrote: »

ok back to the start again
will this space have a stairs and will it be heated?

Sorry.
Just folding attic stairs. Not sure if I will get a rad in or just an electric one.

Zaph

OP, I've deleted the other two threads you've started on this topic. Please don't create multiple threads for the same thing.

BryanF

ajw08 wrote: »

Sorry.
Just folding attic stairs. Not sure if I will get a rad in or just an electric one.

50mm vent gap, 100mm PIR, Vapour barrier taped & sealed, 25mm insulated plaster board - to get you below the 0.25w/m2k (slope roof, column 2, table 5, p26, for upgraded building fabric in a existing dwelling)
BuildingStandards 2011 part L

Gumbo

OP, will the timbers be safe for use?
ie are the strong enough to take the extra dead load (any furniture) and live loads (people) put onto them?

I would have a professional view to make sure, it shouldnt cost too much.

Lombardo86

Hopefully this thread isn't too old to be brought back up.

Aiming to insulate the attic (somewhat properly) and looking for some advice from those more knowledgeable than myself.

Wondering is it worth my while insulating between the rafters rather than just the floor, which i then plan on covering with boarding to help with storage.

The attic has air coming into it from outside due to new guttering, fascia and soffits - So would there be much benefit to insulating above the already freely flowing cold air?

Thanks

MicktheMan

Lombardo86 wrote: »

So would there be much benefit to insulating above the already freely flowing cold air?

None

air

Having just done this I'd recommend 2 layers of 50mm instead of a single 100mm layer.
The 100mm stuff is difficult to handle & cut square, also rafters are often twisted and you will get a better seal & fit with 2 layers.
The 100mm boards are marketed as floor insulation & my own experience would suggest that this is with good reason.