Insulating between the rafters

[whoami]

Hi,

1900 Vic Terrace, currently no (well very little and very old!) installation. I would like to insulate between the rafters rather than the joists as at some point we will be converting the loft. I'm planning to use either the space insulation or foil insulation to a U value or 0.2 or better (as I believe this is acceptable to Building Regs). From what I've read I need to leave a 50mm air gap between the roof felt and the insulation using counter battens (I'm assuming the felt is non breathable). Do I also need to leave an air gap between the insulation and the plasterboard covering that we will (eventually) be enclosing the loft space in? Eave ventilation will not be covered or blocked by the insulation. The insulation will be stapled to the rafters and foil tape used to seal any joints in the insulation.

Does anyone have any suggestions for products or a better way of doing this? Open to suggestions.

Thanks Mark

 

[bikerm4]

look on the celotex website, all details of between and over rafter insulation specifications. http://www.celotex.co.uk/downloads.php http://www.celotex.co.uk/pitched_roofing/under.php

 

[ChippyDan]

i have just completed a loft newbuild including loft conversion and we had to 80mm celotext inbetween the raters and the choice of eiter 50mm over the rafters or a type of bubble wrap that you roll out and fix on with tax (havent used it yet) obviously with the 50mm of cellotex you loose a bit of head room

 

[CyberStGeorge]

You might not be doing yourself any favours trying to predict for a roof conversion.
Mine was built under building Regs last August.
I have completed the Roof Dormers etc. Completely Reroofed etc.
I have not gone into the roof space at the time of writing to Insulated yet.
Building inspector informs me I do not need to bother about new regs as app was made prior to these being introduced.
Point is anything you do now will undoubtably be changed by the time you do your roof conversion.
Regs now are 100mm Celotex between rafters.
50mm celotex accross underside of rafters.
It will be unlikely that they will increase regs in thickness between rafters as most rafters are 75-100mm anyway.
That does not stop them from making new materials for new regs anyway.
Point is celotex may be a new product alltogether by the time you do a roof conversion.
Apply for building regs now if you intend to do a roof conversion.
You have three years to start the project.