Loft insulation all the way up to gable end wall?

DonnyDave

The end joist in the loft is an inch or two from the gable end wall and in that space there is no insulation. In the gap, the top of the plasterboard on the wall is visible, as too is the point where the ceiling meets the plasterboard of the wall.

Is it OK to stuff insulation in this gap or are there possible negative implications? For example, could this possibily result in problems like condensation?


Also, what about insulating under ellevated hot water header and central heating expansion tanks? They're up by about 2 feet (the reason is because it's a bungalow).

phill99

Not sure I'm getting what you are on about with the gable wall issue. A pic would help.

However, never insulate under the tanks. Insulate around and over them, but never under them. This ensures that enough warm air will rise up to stop them freezing in the winter.

27col

I agree entirely, andrew has put it very succinctly.

DonnyDave

Thanks for the responses.

It is a gable roof and the first joist that runs parallel to the gable end wall is an inch or two from the gable end wall. There is some loft insulation already down, but none between the wall and this first joist.

I have checked the ventilation which is under the eaves:


I will ensure that there is a gap between the top of the insulation and the sloping felt lining of the roof. Is a centimetre or two is good enough?

DonnyDave

andrew-b wrote: »

With the recommended amount of insulation now going well beyond the tops of the ceiling joists you'll have to stagger the insulation above the joists a fair bit further back than the insulation between the joists because of the slope of the roof. The insulation between the joist which is below the tops of them ideally should meet the top of the wall plate to meet up with the cavity wall insulation. If you can see daylight through the eaves and can feel a cold draught coming up from the eaves that's good.

Thanks for your help.

The insulation to be installed is perforated in 37cm wide strips whereas the joists are about 60cm apart. This is because it was left over from elsewhere. It is also 20cm thick and covers 38 sq m whereas the loft to be covered is 74 sq m.

From the parts I've looked at, there are two layers of 10mm down (or possibly two 5mm layers and a 10mm one). I propose removing 10cm's worth from half the loft and replacing it with the new stuff whilst putting the stuff I've removed on the other half to bring all up to 30cm.


What about pipes? The boiler flow and return run across the loft (with lagging on) with 10 cm distance between them and the ceiling. Initially I thought about removing the insulation below them and putting it over, but now I'm not so sure. Removing it below will leave a void.


The loft insulation is being looked at because the pipes (and tanks) froze and has resulted in the boiler rupturing. There are a few gaps between the lengths of foam lagging on the boiler pipes. This includes about an inch where the pipes emerge in the loft from the ceiling above the boiler which is at the wall with the eave.

Whilst it is mere speculation, I think that it could have been the pipe frozen by the cold draft in that corner. I am looking for increasing the insulation thickness at that point from 19mm to 25mm.


I think I will box in the ellevated tanks at the bottom, covered by the fibreglass insulation (and remove that below them). The tanks have jackets on, although there is a gap at the top particularly where it goes round the vent pipe. What about wrapping insulation (in addition to the jackets) around the tanks (maybe on top as well)?

themacster

Yes, insulate the narrow gap between the end joist and the gable wall. This should also reduce heat loss from draughts behind the plasterboard wall lining. The place you need to ensure there is a ventilation gap is at the eaves, it isn't as issue at the gable end wall.