redtop Posted March 19, 2020 Share Posted March 19, 2020 Need a shed load for the roof, its a flat roof but we are putting ply on top of the insulation before the EPDM (so joists, OSB, VPL, insulation, ply and then EPDM. So don't need the mega expensive roof insulation, just normal PIR. Anyone know who is doing good deals at the moment, alternatively I am willing to take spare of anyones hands ? Link to comment Share on other sites More sharing options...
Moonshine Posted March 19, 2020 Share Posted March 19, 2020 Slightly off topic but are you putting ferrings in to get the 1:80 fall? Link to comment Share on other sites More sharing options...
scottishjohn Posted March 19, 2020 Share Posted March 19, 2020 just me maybe --but don,t like edpm for roof after I saw result of seagulls peckinbg at food(bones chucked out for dog ) they brought up to roof --made holes inthe apdm would be GRP for me Link to comment Share on other sites More sharing options...
wozza Posted March 19, 2020 Share Posted March 19, 2020 I bought a load of 120mm PIR a few months ago for our floor, (think It was 32 boards). Best price was local builders merchant (Jewson) they beat all of the online places by a few quid per board. It arrived direct from the supplier. If it doesn't have t be exactly 120mm you could try one of the seconds places. Link to comment Share on other sites More sharing options...
redtop Posted March 20, 2020 Author Share Posted March 20, 2020 firings:- yes to get the fall. It will have a sedum covering so gulls wont get to it; but that's a very good point as they would otherwise! will try Jewson, got a trade account there Link to comment Share on other sites More sharing options...
Delicatedave Posted March 20, 2020 Share Posted March 20, 2020 I just done this merry go around and found Insulation Superstore by far the cheapest and you can use TCB to get 3.2% back. But in the end I ordered Steico Therm Woodfibre because it had 3 time the R value. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted March 20, 2020 Share Posted March 20, 2020 10 hours ago, Delicatedave said: I just done this merry go around and found Insulation Superstore by far the cheapest and you can use TCB to get 3.2% back. But in the end I ordered Steico Therm Woodfibre because it had 3 time the R value. Woodfibre has an R value that's a fair bit poorer than PIR, but the best measure is to look at the U value, as that tells you how much heat will be lost through a given thickness of any insulation. Very roughly, PIR will need to be between 1/2 and 2/3rds the thickness of woodfibre in order to get the same level of insulation, or flipped the other way around, woodfibre needs to be at least 50% to 100% thicker to give similar performance to PIR. Link to comment Share on other sites More sharing options...
ADLIan Posted March 20, 2020 Share Posted March 20, 2020 It’s not the R value that should compared as this is thickness dependant - 300mm of woodfibre will have a better (higher) thermal resistance (R value) than 120mm of PUR! Comparator is the thermal conductivity (lambda value) as this is an inherent physical property of the material and is not thickness dependant. The U value refers to the total build up of a wall, floor or roof. The U value of insulation alone is meaningless. it must have been costly obtaining wood fibre with 3x the R value of PUR, approx twice the thickness and twice(?) the price Link to comment Share on other sites More sharing options...
Onoff Posted March 21, 2020 Share Posted March 21, 2020 On 19/03/2020 at 20:23, scottishjohn said: just me maybe --but don,t like edpm for roof after I saw result of seagulls peckinbg at food(bones chucked out for dog ) they brought up to roof --made holes inthe apdm would be GRP for me I worry about similar as we have the sparrowhawks here take pigeons that land on our currently felted dormer roofs. The birds are attracted by all the moss and puddles where there's barely any fall. Link to comment Share on other sites More sharing options...
Delicatedave Posted March 21, 2020 Share Posted March 21, 2020 (edited) 9 hours ago, ADLIan said: It’s not the R value that should compared as this is thickness dependant - 300mm of woodfibre will have a better (higher) thermal resistance (R value) than 120mm of PUR! Comparator is the thermal conductivity (lambda value) as this is an inherent physical property of the material and is not thickness dependant. The U value refers to the total build up of a wall, floor or roof. The U value of insulation alone is meaningless. it must have been costly obtaining wood fibre with 3x the R value of PUR, approx twice the thickness and twice(?) the price Are well perhaps I've (expletive deleted)ed up then but I checked the specs and the product by brand -one was given as 1 something and the other was 3 sorry if I misled anyone. Mine was only 20m so doesn't really matter that much it's only extra insulation on 2 external walls. I just wanted to post the link to the cheapest option I found Woodfibre was about 30% more but more environmentally a choice. PIR Thermal conductivity/ λ (lambda) W / m . K = 0.023–0.026(18) Thermal resistance at 100mm K⋅m2/W = 4.50 Specific Heat Capacity J / (kg . K) = n/a Density kg / m3 = 30 – 40 Thermal diffusivity m2/s = n/a Embodied energy MJ/kg = 101 (17) Vapour permeable: No Wood Fibre Thermal conductivity/ λ (lambda) W / m . K = 0.038 Thermal resistance at 100mm K⋅m2/W = 2.5 Specific Heat Capacity J / (kg . K)= 2100 Density kg / m3 = 160 Thermal diffusivity m2/s = n/a Embodied energy MJ/kg = n/a Vapour permeable: Yes Edited March 21, 2020 by Delicatedave Link to comment Share on other sites More sharing options...
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