I am building a new 2 storey house with attic trusses so I have the use of all the attic space.
1. I have used 100mm Xtratherm rigid board between the trusses following the pitch of the roof and slabbed with foil backed 12.5mm plasterboard.
2. I have used 100mm rockwool between the trusses which make up the floor of the attic and the ceiling of the 1st floor and slabbed the ceiling also with foil backed slabs.
I have also used 100mm rockwool between the joists that make up floor of 1st floor and ceiling of ground floor.
I used 100mm rockwool in the studding upstairs.
I used 75mm Xtratherm rigid board insulation in the cavity and a 32mm insulated slab on the inside walls.
I'm hoping I'll be snug as a bug in a rug.
Hope this helps
ned its very possible that the two constructions highlighted above do not meet minimum regulations, especially the 100mm rockwool on the flat ceiling of the 1st floor.
By my calculations the 100mm rockwool would only give a u value of 0.39... and thats assuming a TC of 0.036 which i doubt it has.. it probably has a TC of 0.38-0.4.
You should have at least 300mm here, and you should have slabbed all the ceilings with 47.5 mm composite plasterboard.
Your walls should be fine but your ceilings are severely under insulated. Sorry!
I have used 100mm rockwool between the trusses which make up the floor of the attic and the ceiling of the 1st floor and slabbed the ceiling also with foil backed slabs.
I have also used 100mm rockwool between the joists that make up floor of 1st floor and ceiling of ground floor.
I used 100mm rockwool in the studding upstairs.
Syd ... I am only insulating between the ground floor and the first floor, not a flat roof. If I had to put in 300mm of rockwool between the joist, i'd have a hard time getting all the pipes and wiring in. As for putting the composite slab for the ceilings ... I don think so ... I have zoned heating so think it will work out ok. I guess I'll have to wait and see.
Bobby, I used rockwool between floors because it has better sound insulation properties than fibreglass and has similar thermal properties.
the principles of energy efficiency and solar gains etc allow for as much free air flow within the building envelope. The idea of insulating floors is one i dont agree with, because you are basically accepting the fact that your house isnt insulated correctly.
You should aim to hold the heat within the building envelope once its generated, you should allow this heat to freely transmit through your house.
To go back to your original question. If you have 9in joists in the attic (as indicated in a later post) I would fill them with 200mm fibreglass insulation, and lay another 200mm across this at right angles. I would use better quality fibreglass with a thermal conductivity of .40, instead of the .44 sold in DIY stores.In the middle of building a new house and getting the inside ready for plastering. I'm very anxious that I insulate the house properly.....what would people recommend for the ceiling i.e-how much insulation?
Also what would you recommend for the attic? I heard somebody mention about adding a foil back plastering slab for external walls....could you please post me on any suggestions.
Thanking You
Phkk --- You dont really need to insulate between ground floor and upper floor. It helps from an acoustic perspective but from a thermal perspective, logically thinking it impedes heat from moving up through your ceiling to the first floor.
Syd .... Both myself and my very experienced engineer are more than happy with the level of insulation installed.Perhaps I didn't fully explain the design of the house which calls for more insulation in some areas and lessin others.
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