Insulating attic

pclive

im looking to insulate my attic and I'm looking for some advice

The attic currently has a small bit of old insulation. The insulation is under flooring suitable for storage. I want to keep this flooring.

The joists are 100mm deep.

I'm going to temporarily remove the flooring and add the insulation

Should I keep the old insulation and add new 100mm insulation on top of it or should I remove the existing insulation and squash 150mm or 200mm in and put the flooring back on top of it?

OU812

It's my understanding that the more squashed down insulation is, the less effective it is.

I've seen a support system for loft flooring in B&Q that allows you to maximise the insulation & still have the flooring.



I think they're €20 for 12

Sleeper12

Dump the old insulation. Use fresh insulation. 150 or 200 mil depending on how thick the joists are. Not a good idea to cram in too much. Also don't insulate under the water tank, this helps stop the tank freezing over in winter. Don't go all the way into the eaves. You need space here to let the attic breath.

the_pen_turner

definetly dont squash it in. its the air that is trapped that is creating the insulation.
take out the plywood and put 6 - 8 inchs of poli iso (kingspan) down then the ply.

the_pen_turner

Sleeper12 wrote: »

Dump the old insulation. Use fresh insulation. 150 or 200 mil depending on how thick the joists are. Not a good idea to cram in too much. Also don't insulate under the water tank, this helps stop the tank freezing over in winter. Don't go all the way into the eaves. You need space here to let the attic breath.

very important not to put the insulation out into the eaves. air flow is very important.
make sure you go out over the ceiling thow or you will create a cold area and will create a mouldy ceiling.


dont insulate under the tank. wrap the tank with insulation . i usually build a frame around the tanks to hold in the insulation. 2x2s and 2x1s will do.
go out and buy the proper lid for your tank , it is well worth it.
if you dont want to buy the proper lid you can use sheets of kingspan to insualate the top

VladamirP

If the existing insulation isn't damp/wet I'd keep it. When cutting the insulation (fiberglass) cut it 50mm wider than the gap between joists so it fits snug.

When taking up the boards I'd do a row at a time and put the board straight back down so you always have a base under you. Start at the furthest point from the access and work back.

I'd cut the required width outside because doing it in the attic is a pain in the hole with the fibers floating everywhere and getting everywhere.

Have a look at this.

https://www.isover.ie/sites/isover.ie/files/assets/documents/7101_isover_attic_notebook_lr_1.pdf