Hi
I'm in the midst of getting a builder to build a hip to gable loft conversion.
As our house has solid wall construction and is not very airtight we are keen that the new construction performs well with respect to energy efficiency.
I've been reading various websites about roof construction and I have some questions.
Some sites states that you must maintain a 50mm air space between the insulation and the roof tiles for ventilation.
Another site states that with a breathable roof membrane, building control will allow this air space to be reduced to 25mm. This would allow for increased insulation.
Anyone able to confirm?
The rafters in our roof are 89mm x 44.5mm so there would be less space for ventilation compared with the rafters that would be used for the dormer construction which I understand to be 145mm x 47mm.
So the air space in the pitched section of roof will significantly affect the amount of insulation that could be fitted between the rafters.
Are these breathable membranes good enough to allow a reduction in the air space without issue? Any particular brand I should insist on being used?
Previous experience has taught me to spec as much as possible to prevent the tradesmen fitting a worse performing alternative.
Many thanks
I'm in the midst of getting a builder to build a hip to gable loft conversion.
As our house has solid wall construction and is not very airtight we are keen that the new construction performs well with respect to energy efficiency.
I've been reading various websites about roof construction and I have some questions.
Some sites states that you must maintain a 50mm air space between the insulation and the roof tiles for ventilation.
Another site states that with a breathable roof membrane, building control will allow this air space to be reduced to 25mm. This would allow for increased insulation.
Anyone able to confirm?
The rafters in our roof are 89mm x 44.5mm so there would be less space for ventilation compared with the rafters that would be used for the dormer construction which I understand to be 145mm x 47mm.
So the air space in the pitched section of roof will significantly affect the amount of insulation that could be fitted between the rafters.
Are these breathable membranes good enough to allow a reduction in the air space without issue? Any particular brand I should insist on being used?
Previous experience has taught me to spec as much as possible to prevent the tradesmen fitting a worse performing alternative.
Many thanks