Loft insulation help please

[Broadback]

I know this is frequently asked, but bear with me please. I live in a bungalow, all the electric and alarm wiring runs across the floor of the loft both in line with and at right angles to the beams, also the loft is partially boarded and there are no vents. How effective would it be to insulate the roof of the loft rather than the floor, if I did this would I still need air bricks? Also any other material than Kingspan good? If I have to insulate the floor is there any practical solution bearing in mind the cables and partial flooring?

[RedOnRed]

If you insulate the roof area itself you could either spray something on or use polystyrene panels or other equivalent panels.

The better your loft area is insulated the more condensation will increase so you will have to use airbricks. I had my loft insulated this year and they used special plastic things which wedged open a gap on the inside of the roof tiles which now give plenty of ventilation without having to use airbricks.

[Peter Taylor]

This is not true if the insulation is at rafter level, in fact the reverse is the case. The warmer the air in the loftspace, the more vapour it can hold and so the condensation will be less.

Cold roofspaces (with insulation at ceiling level) require ventilation to guard against damp timbers and rot. Warm roofpsaces (with insulation over the rafters) do not need ventilation. Yours will be a hybrid because the top surfaces of the rafters will not be insulated. Therefore you need to provide a vapour barrier on the warm side of the insulation and 50mm air gap above the insulation to allow airflow. You will need to install plastic ventilators in the soffits and ventilated ridge tiles to allow through ventilation.

Yep, good idea as long as you have breathable underfelt.