Lofts: insulating underside of roof?

Jun 09, 2005 6 Replies
70s bungalow. I am currently topping up the insulation on the loft floor, putting a new layer over the manky old stuff.

The Wickes leaflet also recommends insulating the underside of the roof, by use of polystyrene blocks in between the roof timbers. They also sell aluminium foil stuff for the same job. A side effect is that it will also cut down on dust blown into the loft.



Is this overkill for a loft which is just used for storage purposes. All pipes etc. are lagged and it seemed warm enough when I was up there last evening!



Bruce



Insulation will not only reduce cold, but warmth too. Make solar gain through the roof lower and keep the house a little cooler in the summer.

But how cold is it in winter. Doubt if you can have too much insulation so I'd do it but remember you need to leave 50mm airgap above the insulating blocks.

What's the point of leaving a 50mm gap between felt underlay and insulation, unless you introduce an air flow vent at eaves and ridge.

8" or 200 of insulation quite adequate.

It's a 70s bungalow so it most probably has air flow at the eaves. You need to either open the ridge or bridge it to allow the airflow to pass through.

Assuming you mean fibre or Rockwool, that doesn't even meet the current building regs, let alone actually make a real attempt to save energy. 265mm is needed so regard 300 as a min.

Wickes charge =A313 for a roll of aluminium foil insulation to staple onto the underside of the roof. At those prices, it would cost quite a bit to cover the whole roof...probably more than I would save on heating.

Bruce

Not sure of the size but £100 should see the average house roof done. Remember it isn't just the insulation but the air trapped below it which also insulates so you should see sizeable reductions in heat loss. Of course the rest of the house needs to be brought up to scratch otherwise the heat will find another route out but for insulation is generally one of the few home improvements that really do pay back quickly.

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