I'm trying to insulate my roof space while it's still warm up here, abd while 70% of the roof structure is open and accessible, part of the roof is not. The upper rooms are partially chamfered along the exterior walls by the roof. This means that, from the loft, you can see the top of the exterior walls about 2m down a 100mmx400mm cavity that follows the roof angle. I'm trying to get some insulation down those gaps because when it's -20 outside like last year the chamfered ceilings literally have cold air rolling off them and there radiators/boiler struggle to keep up. I could of course install bigger rads (I think we're fairly low on radiators WRT boiler output) but I'd much prefer just not to lose the heat so I started slipping space blanket down the gaps. Problem is the gaps are riddled with nails and it's REALLY difficult to get the insulation down there - took 2 of us about 3 hours to get 4 gaps done, there's about 20 more to go and the last one won. We were using two super-long pizza shovels made from ply and 1x1/2 to trap the insualtion and shove it down, but thats practically impossible when the nails get in the way.
Our two remaining options are blown insulation (££) and pulling the glass from the space blanket and stuffing it down manually with a long rod 
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Any other thoughts?
