Loft insulation alternatives

[Handy Andy]

Good evening all, 

 

270mm is the recommended height for loft insulation.

 

Is there an alternative? Use 75mm Kingspan/celotex? Etc

 

I don't want to loose height but still want to be compliant with building regs.

 

Tia

[Radian]

You've got quite a challenge on there. Yes you can use insulation with lower thermal conductivity but unlike glass fibre or mineral wool, PIR sheets aren't vapor permeable. So you would need to start by putting down a vapor barrier and that's difficult to get right unless you are boarding the ceiling. Even then all penetrations (pipes, cables, downlights etc.) must be vapor tight. You might think you could just lay a vapor barrier over the attic joists but that's asking for condensation to form around the timbers when moist air finds its way up under the barrier and condenses. Without airflow it will be a 'hot mess' between the barrier and ceiling.

 

This is all assuming you have a ventilated loft. If the airspace in the loft was conditioned, i.e. a room-in-roof then I doubt you'd be asking about alternative insulation.

[DevilDamo]

What u-values are you needing to meet… building regulation application submitted before 15th June 2022 or after?

 

Where are you insulating… ceiling or rafter level?