Anyone put in their own loft insulation and boarded out their loft?

bigpappa

I need to update the loft insulation but I am not sure how to proceed.

The ceiling joists are 9cm high and are 35cm apart. I am planning to remove the old insulation which looks compressed and dead.

If I add loft legs that are 17.5cm in height then I will get 26.5cm clearance (9+17.5) but the recommended insulation thickness is 27cm - so the insulation will be compressed by 0.5cm once I add the loft boards.

I am loathe to go for the 30cm loft legs as that would create a space of 39cm under the boards and I will lose about 12cm in height.

I am not boarding all of the loft- only the central part - about 20sqm.

Having looked online it seems fairly straightforward but I am not sure how to proceed re the height of the loft legs.

Ganga

Check that you can not get loft insulation fitted for free ,google free insulation and check .

bigpappa

Ganga said:

Check that you can not get loft insulation fitted for free ,google free insulation and check .

I am not on benefits - so its going to have to be the DIY method.

grumbler

IMO 26.5cm is more than sufficient if done neatly. Cavity walls are 30cm with 10cm cavity - and bricks are more conductive than any insulation.

pramsay13

A slight compression of 0.5cm won't make a massive difference although you can get insulation that is 20cm thick.
Basically the more the merrier. 
Removing the old stuff is a bit of a pain as it will irritate so you need gloves and masks etc. 
Most people would just lay new stuff on top of the old stuff, at right angles.

twopenny

I've done this, it was the government firm that laid the old on the new and it worked fine.

I also put up boarding with no problems and some of the insualtion had to be squished a bit, old house so big joists, and it all worked fine.

One thing I wished I'd done was a layer of light waterproof material over the insulation. When we had the big March snows it blew under the roof tiles along our streets and even removing snow some melted through the insulation giving ceiling stains that had to be dealt with. Also just general dust from the clay tiles.

bigpappa

Can anyone recommend loft insulation - mineral or glass? Knauf EKO or earthwool - there are so many options.

bigpappa

pramsay13 said:

A slight compression of 0.5cm won't make a massive difference although you can get insulation that is 20cm thick.
Basically the more the merrier. 
Removing the old stuff is a bit of a pain as it will irritate so you need gloves and masks etc. 
Most people would just lay new stuff on top of the old stuff, at right angles.

Do I need some extra height under the loftboards for ventilation. If I compress the loft insulation that means there is no air circulation?

grumbler

twopenny said:

One thing I wished I'd done was a layer of light waterproof material over the insulation.

A word of caution. Fully waterproof membrane can cause condensation under it potentially damaging the joists.

FreeBear

bigpappa said: Do I need some extra height under the loftboards for ventilation. If I compress the loft insulation that means there is no air circulation?

If you are just boarding the central part of the loft, no need to worry about leaving a gap.

Insulation - Makes little difference whether it is rockwool, fibreglass, or what ever. They all have virtually the same rating, so go for which ever you can get the best price on. Just do not ever use that spray on foam being pushed by the disreputable "expurts".

100mm roll laid between the joists - Do make sure you get it right up under the eaves to avoid any cold spots. Lay 170mm at right angles to the 100mm layer, again making sure it is pushed well in to the eaves.

Most rolls of loft insulation come pre(partially) cut to suit standard spacing of joists of 400mm or 600mm - If you have 90mm x 50mm joists with a gap of 350mm between, then you have joists on a standard 400mm centres.

Homer_home

FreeBear said:

bigpappa said: Do I need some extra height under the loftboards for ventilation. If I compress the loft insulation that means there is no air circulation?

If you are just boarding the central part of the loft, no need to worry about leaving a gap.

Insulation - Makes little difference whether it is rockwool, fibreglass, or what ever. They all have virtually the same rating, so go for which ever you can get the best price on. Just do not ever use that spray on foam being pushed by the disreputable "expurts".

100mm roll laid between the joists - Do make sure you get it right up under the eaves to avoid any cold spots. Lay 170mm at right angles to the 100mm layer, again making sure it is pushed well in to the eaves.

Most rolls of loft insulation come pre(partially) cut to suit standard spacing of joists of 400mm or 600mm - If you have 90mm x 50mm joists with a gap of 350mm between, then you have joists on a standard 400mm centres.

Not forgetting to leave an air gap at the eaves so the roof space can breathe