Insulation Advice

pete6296

Hi all,
Got prices for insulation today,
300mm fibreglass for 91 sq. metres at a cost of 494 euro excl vat. for between ceiling joists.
200mm Kingspan TP10/100mm board for a cost of 2500 euro excl vat.
For the sloped roof in house, 1300 euro for TP10/100mm with TW56 35mm/12.5mm slab along sloping rafters.
A company suggested metac but this would result in no 50mm air gap for sloped roof.

What do people advise, there is a significant difference in price especially for fibreglass against Kingspan but which is the best option, hard in my opinion to cut sheets to exact size for between ceiling joists.

Rest of house already with a 60mm Kingspan Kooltherm in cavity with Kinspan insulation board inside on external walls.

Any advice appreciated

Thanks,
Pete

No6

Pete Kingspan insulation is expensive but it gives a good performance. For flat ceilings if you have the room use the 300mm fibreglass, you dont need kingspan unless you want to walk on the ceiling joists and board out the attic, you could also consider a tw56 under the ceiling joists & 200mm fibreglass. You've not got much choice with the sloped roof, try getting prices for xtratherm similar to kingspan but supposedly cheaper.

RKQ

pete6296 wrote: »

"A company suggested metac but this would result in no 50mm air gap for sloped roof".

Use breather felt & counterbatten!

"There is a significant difference in price especially for fibreglass against Kingspan but which is the best option, hard in my opinion to cut sheets to exact size for between ceiling joists".

Use circular saw or table saw for perfect cut, use blade or hand saw for accurate cut, then rub sheet on conc floor to smooth sides!

As No.6 says use 300 fibreglass if not walking in attic. Insulate, insulate, insulate.