Insulate lounge ceiling

stuart45

The glazed area will still lose more heat than the rest.of the house. The SAP rating means that the rest of the house makes up for the loss. You might need some more heat in the room.

ThisIsWeird

The only unknown, then, is the size of this rad. It does sound like quite an ask for it, but it could well be correctly sized.

Whether to insulate the ceiling is a tricky one to answer - there is certainly no harm in doing so, and I suspect it'll help to some degree. But most such internal ceiling/upstair floor voids are not insulated in houses, afaIk, which I have to say surprises me, as I bet most/all are actually quite draughty, with the joists going through the inner wall skin with wee gaps around them, so ventilated to the chilly cavity. That's my understanding anyways.

stuart45

Nowadays joists are usually supported by hangers when going into the external walls. If not, extra care is taken to seal them properly.
When the ceiling is down it's worth checking the joists are well sealed if they are built into the wall.

FreeBear

ThisIsWeird said: Whether to insulate the ceiling is a tricky one to answer - there is certainly no harm in doing so, and I suspect it'll help to some degree.

Having insulated the space between ceiling & upper floor in two rooms here, I feel well placed to offer an opinion. In terms of making either room warmer, it has made no noticeable difference. If there were any energy savings to be had, it would be minimal at best. Putting the insulation in has made a minor difference in perceived noise transmission, but double thickness of a sound blocking plasterboard would have probably been a better solution for that non-issue.

If the OP is to fill the void with insulation, may as well stuff it full with 200mm of glassfibre/rockwool - 50mm, if you can still get it, isn't going to make any difference.

ThisIsWeird

Thanks, gents - useful info.