gilesm

What is the temperature of the actual floor? A floor at 27C would be pretty hot, and should result in your air temperature easily reaching 21C. So I would say it's a reasonable floor temp limiting probe temp. Many engineered woods can go fairly high, but I'd prefer to not go higher than 45C on the mixing valve, even if the supplier says it's ok. Perhaps try 45 and see if you see a difference.

Jeremy, do you think a workshop "chip extractor" would work for blowing it? They are designed to suck large volumes of wood chips/dust, so cellulose should be fine to put through them. It is somewhat frustrating how the US shows hiring these machines to be easy/common/cheap, yet here in the UK they are not available! I already have a wifi/Alexa remote switch on my chip extractor, so the remote control aspect is covered.

I have flexible solar panels on my campervan. The reliability is atrocious - I need to replace them every few years. I'm not sure of the true reasons, but it might be due to the overheating (due to lack of metal in the flexible construction, to sink the heat?) or the quality is generally less than rigid models? They have a "warranty", but it's easier to just buy and fix another one when the current one dies. I don't know if the experience is transferable, but check the failure rates carefully.

Thank you ProDave. From reading up some more about warm/cold roof construction on https://www.designingbuildings.co.uk/wiki/Warm_roof then yes it looks like a warm roof. The insulation is in line with the rafters, and the space between ceiling/rafters should be warm (and not ventilated to the outside). I don't yet know where the air tightness layer is supposed to be. My plan of attack now is to put in a loft access hatch to get into the roofspace (there's up to 5ft of headroom so should be easy to look around more thoroughly). The joists are circa 14" apart and there are two layers, so I'll get our friendly builder to do it! Will report back when I know more. Thanks for the help so far...

Thanks for the great replies! Ferdinand: yes, I have taken thermal photographs from the outside during a recent cold, still day. No significant heat patches from the vertical brickwork, but there are some obvious patches on the sloping slate roof. Hence my assumption those are the areas to focus on. Scottishjohn, I think we have a "cold roof". I have the construction drawings, and have tried to sketch out the roof structure, attached. I assume there's a vapour barrier somewhere but I'm not sure where. There is some heavy transparent plastic sheet right behind the plasterboard in our upstairs laundry room, but maybe that's just for the laundry area. [Edit to add: this is probably the vapour control layer?] ProDave, the triangle "combe" section is within the insulated area, as the diagram should show. There are plenty of cables and the UFH pipes going through it (see picture, looking horizontally outwards through a small hole from first floor laundry, at vertical insulation before the roof slope starts). From what you and the others say, I could pump spray foam or cellulose/alternative into this area through holes in the plasterboard. Any future wire/pipe repairs would be hampered, but it would (I think) fix the draught problem. I don't think this would affect ventilation, as it would all be within the insulation envelope?

Hello everyone. Recently joined the board, but have been a lurker for a while! A couple of years ago we moved into a 10-year-old timber-frame house with GSHP. Brick outer & slate roof. All well and good, except there is a significant heat loss problem. We're living in a "plasterboard tent" and hope you can help me with some ideas?? Lots of detail below. I've had a look through some of the holes behind sockets etc, and I can see that on the sloping roof areas, Celotex-style insulation is fitted between the rafters but some of the sections (circa 24x18" perhaps?) have tipped in & down, allowing air through. There is a wind blowing behind the plasterboard (obvious without smoke pen). The GSHP is working efficiently I believe, but the UFH simply cannot cope with the heat loss and we cannot keep rooms consistently above 20C when it's zero outside. Bills are of course rather higher than expected, though we are on the Wiltshire/Dorset border so fairly mild. Rooms upstairs have sloping ceilings down to about 3ft high, when the plasterboard becomes vertical. So each top-floor room has a wind tunnel along-side it, within the thermal envelope. I've bought a FLIR C3 thermal camera and have found 3 cold patches in one room's sloping ceiling. Checked with a borehole camera, saw the fallen insulation, and squirted in plenty of low-expansion foam. This fixed the local problem there, but there are clearly more gaps which are not close to the plasterboard so the thermal camera can't easily spot it. I assume/hope the problem is only with slipped insulation on the sloping roof and that there are a reasonably small number of failures, which will not increase in time. But this targeted approach only works for the holes in the insulation which I can see. I've put smoke bombs into the area within the insulation to hopefully see gaps around slates, but the smoke egresses over a large area of the slates. Presumably due to intact fabric between slate and insulation. How to fix this? One intense approach would be to remove all of the tiles (attached with wire hooks, so do-able) and look for problems; or to remove chunks of plasterboard inside and go hunting with the thermal camera. Any other thoughts on techniques to find and fix the gaps? Is there some sort of blown insulation to fill up all of the eaves within the thermal envelope??