How thick can i go with loft insulation?
Discussion
Anyone know how deep i can lay the nasty loft insulation? I have currently got a layer of what i can only describe as approx 50mm of 'yellow s
t' and a layer of 100mm over that which i layed.
I am aware that 270mm is the current depth to comply with building regs but is it safe (obviously leaving a breathing space) to put a further 170mm top layer on what i have making a total of 320mm ish?
t' and a layer of 100mm over that which i layed. I am aware that 270mm is the current depth to comply with building regs but is it safe (obviously leaving a breathing space) to put a further 170mm top layer on what i have making a total of 320mm ish?
270mm is in indication only. It is a figure dreamt up so that if an average rated product is used then it should give the required U value.
You need to be careful of a couple of things..
1) Don't block the ventilation to the loftspace - i.e. don't cram it in to the eaves.
2) cross lay
3) you could purchase higher rated rock wool, such as the products from Kingspan (Crown Dritherm 32 rated or possibly lower).
Fill it as much as you like, but don't block the ventilation.
You need to be careful of a couple of things..
1) Don't block the ventilation to the loftspace - i.e. don't cram it in to the eaves.
2) cross lay
3) you could purchase higher rated rock wool, such as the products from Kingspan (Crown Dritherm 32 rated or possibly lower).
Fill it as much as you like, but don't block the ventilation.
We had to put loads in our new extension loft because the main house is listed. The Fat Controllers wouldn't let us put in (sympathetic) double glazing but the regs state you have to make up a total 'u value' for the area of the extension. So we put loads in the loft. Seems to be OK two years on.
TooLateForAName said:
If you do a search, there was a similar question asked a while ago with interesting feedback from Sam_68 (i think) - too much rockwool type can cause problems - iirc you can get condensation in the insulation which then never dries out.
Yep, 'twas me.We're still not completely sure what's going on ('we' being the volume housebuilding industry and the Building Research Establishment), but there is good evidence to suggest that it's not just interstitial condensation that's the problem any more.
Put simply, if you use too much insulation, it seems likely that it works too well: because very little heat is leaking through the ceiling, the air temperature in the loft falls much lower than it used to at night and a 'dew' forms on top of all that nice, absorbent insulation quilt.
There are other mechanisms at work too, though, and it is proving very difficult to predict or analyse the problem.
mk1fan said:
Never said it was easy or cheap - just simple!!!
Simple is debatable too, I think? Simple to suggest or to show on a drawing; rather more difficult to actually implement:
In what way is it 'simple', compared to draping another layer of fibreglass quilt over what's already there?
For the benefit of anyone who doesn't know the difference (and to avoid Fatboy burning his house down): A 'cold roof' is the traditional form where you have insulation at ceiling level and a ventilated, uninsulated loft space above it. A 'warm roof' is one where you put the insulation up against the underside of the roof slope itself, with the loft space being part of the heated and insulated envelope of the house.
At risk of stating the obvious, you also need to bear in mind that unless you're actually using the roof space for living accommodation, with a 'warm roof', you'd be wasting money heating the loft for no benefit.
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