Insulation in Roof of New Extension

[excited]

Just had the drawings back from the architect and they have specified 100mm of Kingspan K7 between the rafters and 53mm of K18 below the rafters. Rafters are 150mm deep.

Now if I increase the K7 to by 50mm and also increase the rafter depth by 50mm to maintain a 50mm air gap above the insulation. Will i notice the difference in temp and the heating bill being lower.


Thansks

 

[freddiemercurystwin]

Negligible on both counts. Prolly take several years to get payback of the additional cost.