Loft Insulation

quackers

quackers

quackers

Soldato
Joined
18 Oct 2002
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Hi all,

when we bought our first house last year, we found out we could have free insulation from British Gas. The loft already had insulation in the rafters, but not knowing any better I cleared out some old bits and pieces from the loft and got it done.

Forward to now and we've had the loft boarded, when I was getting a couple of quotes one joiner said that's it's a bad thing to have insulation between the joists and in the rafters as it can cause condensation. I've heard the term cold and warm loft spaces?

The question is can I leave the old insulation in the rafters or is it advisable to get rid?
 
What sort of roof/rafter insulation? Is there an air gap between it and the felt/tiles?

You need air flow up there, but having both insulated is not necessarily an issue if there is sufficient airflow to prevent damp problems.
 
the fibreglass roll type of stuff, It's been placed in the rafters, I wouldn't exactly say there was an air gap between it and the back of the slates that I can see
 
I always thought you should insulate the loft floor (under your boarding) or in the loft beams/rafters (under your roof tiles), but not both. I think this is what you've heard about hot and cold loft space. Cold would be insulating the loft floor and hot would be insulating the roof. But I'm not a professional and only have experience of DIYing my own insulation (loft floor).
 
quackers said:
the fibreglass roll type of stuff, It's been placed in the rafters, I wouldn't exactly say there was an air gap between it and the back of the slates that I can see
Click to expand...

this insulation is very likely to just get damp and not perform at all - if you are doing it this way you want to leave a good air gap between the insulation and the surface of the roof.

In a new construction you usually end up with insulation at ceiling level, or if you want to use the loft space as a room you would insulate between the rafters (with a rigid insulation board, sometimes with an insulated plasterboard over…)
but you would still have roll insulation at ceiling level for sound transmission.
 
One or the other, not both. You could get condensation up there now, unless you have really good airflow.

Just to do the floor, it's more efficient. Otherwise you're insulating your loft as well, which should be well vented, and would be a waste.
 
Rossi~ said:
One or the other, not both. You could get condensation up there now, unless you have really good airflow.

Just to do the floor, it's more efficient. Otherwise you're insulating your loft as well, which should be well vented, and would be a waste.
Click to expand...

Or you could do it properly and have a very useful loft space, which wouldn't be a waste at all
 
Hi and thanks for the replies, no the loft is just going to be for storage it's not high enough.

I think I'll probably remove the old insulation from the rafters as you guys have echoed what I thought
 
Just to make sure, don't forget to leave the floor underneath the tank (if you have one). Don't insulate under it in case it freezes over winter. Also, if you have any left overs, put it onto/around the tank, even if you have a jacket on it, may as well.
 
Bringing back the most recent thread I can find on the subject, but has anyone seen any good deals on loft insulation for self installation recently?

Ideally want to try and put another 200mm in the loft - but think I have too much already to qualify for the free BG offer.

Chris
 
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