SHED/SUMMER HOUSE INSULATION

[iNf]

I'm in the process of turning the SIL's summer house into a home office. The roof joists are 5" deep, the original plan was for 50mm insulation but we have enough left over for double depth. Will a 25mm air gap be enough? Width between joists approx 500mm, length 2.6m with vent holes each end. Any advice welcome.

 

[Cuthy246]

I'm in the process of turning the SIL's summer house into a home office. The roof joists are 5" deep, the original plan was for 50mm insulation but we have enough left over for double depth. Will a 25mm air gap be enough? Width between joists approx 500mm, length 2.6m with vent holes each end. Any advice welcome.

What type of insulation?

 

[iNf]

What type of insulation?

Foil backed rigid PIR (Kingspan type)

 

[gaz1]

I'm in the process of turning the SIL's summer house into a home office. The roof joists are 5" deep, the original plan was for 50mm insulation but we have enough left over for double depth. Will a 25mm air gap be enough? Width between joists approx 500mm, length 2.6m with vent holes each end. Any advice welcome.

1" is at the bare limit even with normal insulation so you will be fine

but please note insulation board dosnt breath so in effect you are trapping moisture at the beams where it touches them

 

[Cuthy246]

As gaz says 25mm/1" is absolute minimum you could go. If there is plenty of ventilation then crack on