Loft Insulation....is there any reason why....

aliasojo

....I can't put the usual rockwool stuff between the rafters/trusses and staple netting over it to hold it in?

I know you can get boards specially for this purpose that stay in themselves through compression only but they are a lot more expensive than the bog standard loft rolls.

ormus

rockwool and netting is a pretty standard industry fireproofing technique. so you should have no problems there.
with normal fibreglass ive seen installers use string across to hold it in, while they place ie hardboard or PB over the top.

27col

When I converted my garage to a flat I did the wall insulation inside my newly built stud-work inner skin by using string wrapped around nails. It seemed to hold the insulation in place quite well until it was covered by plasterboard.

Chippy_Minton_2

aliasojo wrote: »

....I can't put the usual rockwool stuff between the rafters/trusses and staple netting over it to hold it in?

Why would you want to do this?

Are you converting the loft?

If not why insulate the loft, it's designed to be cold. Insulation on the floor is for the rooms below.

How will you ensure free airflow between the roof and insulation doing it your way?

The_Pedant

I'm assuming you're talking about hanging this on the underside of the roofing, rather than between ceiling rafters? It's recommended to have something like a 50mm airgap to allow free ventillation under your roofing.

I did something similar once, on the roof rafters, just using string and a staple gun. I didn't want to push the insulation all the way in, as this would not allow sufficient airgap under the roofing. The string, tacked loosely, allowed the insulation to hang down a little, to leave an airgap without having to compromise on the amount of insulation.

David_Aldred

Please see the Rockwool library:
http://guide.rockwool.co.uk/building-elements/roof/pitched-roofs.aspx?page=2846#section_2852

http://guide.rockwool.co.uk/tools/cad-library.aspx?cat=1891

Kindest regards, David Aldred Independent damp and timber surveyor

aliasojo

Chippy_Minton wrote: »

Why would you want to do this?

Are you converting the loft?

If not why insulate the loft, it's designed to be cold. Insulation on the floor is for the rooms below.

How will you ensure free airflow between the roof and insulation doing it your way?

No, loft is not being converted.

There is already some insulation there from when the house was built but it's got thin and torn over the years so I was going to replace it since the npower offer was available and it could be done very cheaply.

We have condensation issues and have had roof vents put in, put in a more efficient bathroom extractor fan and are increasing the loft floor insulation. By putting more insulation on the roof at the rafters, it will put yet another barrier between the cold outside air and any warm air that does manage to rise from the rooms below.

The existing insulation is between the trusses so it's touching the underside of the roofing felt, in fact it's actually stuck to it as if it's been glued. Neighbours confirm all these houses are the same.

tomfun

I would use insulating foil,it costs more than Rockwool but less than Kingspan,it is brilliant stuff ,some are equivilant to 150mm of Rockwool,you just staple it to the rafters and tape the joints with ductape ,plus it will be alot cleaner in the loft without the loose fibres floating around in the air..
When it is taped correctly all drafts are kept out not like with Rockwool

Mankysteve

I would bother as you'll so much fresh air flow though your loft as there would be no real extra saving in loft. You'd better placing another layer on top of the loft floor.

andrew-b

I agree with Chippy (blimey..there's a first lol!!!) . Unless your converting the loft into a heated space then don't put insulation between the rafters (and then you would remove the insulation between/on ceiling joists) ...i've seen tales here of someone putting foil insulation between the rafters and then wondering why there roof is pouring with condenstation. Told them to take it down..problem solved. Your loft *should* be cold and well ventilated. Your money would be better spent laying additional insulation on top of the ceiling joists.
I would pull down any existing insulation between the rafters. Also check that the current insulation between/on ceiling joists doesn't go right upto the edges of the eaves and pull back if needbe..you need to leave a gap to let air enter the roof through the eaves and should be able to feel a draught coming in around the eaves.

aliasojo

I've been in the loft this morning sorting stuff out and I've checked the existing insulation. It runs across the top of the trusses....so it was put over the timbers from the outside and the roofing felt laid on top. As I said earlier, it seems glued to the felt.

I haven't got a hope of pulling the exisiting stuff down.