Since having a new roof fitted with breathable felt the loft seems a lot more drafty. Ive been thinking of insulating the roof then plasterboarding it, whats best insulation as not to create condensation, i would fit kingspan but its so expensive, will polystyrene boards do the job.
Insulating a loft roof.
- Thread starter timmy74
- Start date
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How much insulation do you have at the moment? it should be 270mm min.
Andy
Andy
hi bud
the stuff on the floor is minimum, i was thinking about the ceiling rafters, insulating between them then plasterboarding over. ive got a big drop down loft hatch with ladders on so its letting a draft down to the main house.
the stuff on the floor is minimum, i was thinking about the ceiling rafters, insulating between them then plasterboarding over. ive got a big drop down loft hatch with ladders on so its letting a draft down to the main house.
A drafty roof is a healthy roof.
Fit 300mm fibreglass insulation at the ceiling level i.e. 150mm between joists and 150mm at 90 degrees across and above the first layer.
Fit a decent loft hatch or at least draft proof the existing hatch.
Fit 300mm fibreglass insulation at the ceiling level i.e. 150mm between joists and 150mm at 90 degrees across and above the first layer.
Fit a decent loft hatch or at least draft proof the existing hatch.
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Which is fine if you don't want to use the loft ever again.
A slightly better solution would be to fit 100mm Loft insulation at ceiling level, between the joists. Overboard this with 100mm Celotex GA4000 or Kingspan TP10. Then you can put some ply, or hardboard, or chipboard flooring down and still be able to use the loft.
To insulate at rafter level, I'd need to know the depth of the rafters and at what centers they were at.
You'll have those weirdo sparkies chomping at the bit if that celotex goes anywhere near any cables.
According to them your home will spontaneously combust if you so much as waft any foam board insulation near a live cable.
You'll have those weirdo sparkies chomping at the bit if that celotex goes anywhere near any cables.
According to them your home will spontaneously combust if you so much as waft any foam board insulation near a live cable.
Which is exactly the same as putting another layer of 150mm / 170mm / 200mm loft insulation on top of the existing. Which every loft insulation contractor does anyway.
The only way round this is to insulate between and under the rafters - which can be a costly exercise.
1) Expanded polystyrene must not touch PVC sheathed or insulated cables as the plasticiser will leach out of the PVC leaving a sticky mess, and causing the PVC to shrink, crack and go brittle. You can imagine that cracked electrical insulation is not a good idea
2) you must not lay insulation over downlighters that project through the ceiling, but you can make a plasterboard box to put over them
3) You can lay insulation over the cables for ordinary domestic lighting circuits, because they are so lightly loaded. You must not insulate over cables for immersion heaters or electric showers since they usually run near their maximum capacity so will overheat if surrounded by insulation. Cables which on one side are in contact with the plaster or brickwork may be acceptable depending on factors you can ask about on the electrical forum.
2) you must not lay insulation over downlighters that project through the ceiling, but you can make a plasterboard box to put over them
3) You can lay insulation over the cables for ordinary domestic lighting circuits, because they are so lightly loaded. You must not insulate over cables for immersion heaters or electric showers since they usually run near their maximum capacity so will overheat if surrounded by insulation. Cables which on one side are in contact with the plaster or brickwork may be acceptable depending on factors you can ask about on the electrical forum.
You have to leave a gap of 50mm between the top of the insulation and the underside of the tiles.
don't install it between the rafters.
Put it between/over the ceiling joists, and properly seal and insulate the loft hatch.
Your just asking for trouble insulating the rafters for not a huge benefit (the loft still has to be ventilated).
Put it between/over the ceiling joists, and properly seal and insulate the loft hatch.
Your just asking for trouble insulating the rafters for not a huge benefit (the loft still has to be ventilated).
of course you can.
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