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CoolScientist,

Insulation for lofts tends to be Glasswool or rockwool mineral fibre wool anywhere from 150-250mm thickness.

Am an architectural designer Post part 2 in practice at the mo.

But there are alternatives.

You can ask your builder to look into Celotex with foil (vapour barrier) as its a rigid board. Obviously its more expensive, but it also means you could have, whats called, a floating floor (fixed to the top of the ceiling joists) of chipboard over the top.

Or you can create a warm roof. Glasswool between the rafters and over isulate the underside of the rafters with celotex. This will give you the necessary U-value, remove the fibre leakage, and create a warm loft. But you will need to have a breathable roof membrane (Tyvek) under the battens and tiles as well...... But your builder will be able to explain it better than a message.

Or a thinner (but probably more expensive still) is a product called tri-iso super 9 by actis (enigma insulations).....
Now this product is a seriesof layers, of foils etc etc.... thats about ten millimetres thick - equivalent to about 200mm of rockwool insulation.... however it is a fairly new material.....

Any way hope this helps

Kind regards
Peter
 

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CoolScientist,

Sorry did the previious message before reading your long won thoroughly regarding turning the insulation 90 degrees.

The NHBC trend and B Regs stipulate, that the better way of insulating the loft is to run the insulation between the joists first to the full depth of the ceiling tie. Then apply an additional layer of insulation running over that and the ceiling ties in the opposite direction. Hence 90 degree.

Firstly find out if this is the case?

If so, then I wouldn't recommend it, you may end up contravening the NHBC certificate if you rotate the insulation. if you then have a later problem, it could be your doing, and so therefore up to you to resolve the matter.

Second, speak to your builder again, they will have years of experience and ask there advice. There is always more than one answer when it comes to construction.

Third, look into where you would want to place the rooflights, in regard to sun patterns. North facing you get a gentle light, without the burning heat. You may also require planning and further building regulations approval. The heat and light you get from a rooflight is considerably more than from a vertical window, and heat could effect the track.

Fourth, check with the builder, as to what thickness rigid insulation you propose to add to the underside of the rafters, as it sounds like its a cold roof situation. And you do not want to penetrate, or disturb the roofing felt. If the roofing felt comes into contact with the insulation it could allow condensation build up and subsequent water damage.

Again I hope this helps you, and please let me know how you get on if you need any further advice via. email [email protected]

Kind regards
Peter
 
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