Regs for insulating loft

[LordFrederickIII]

I'm looking at getting the loft insulated at the ceiling level.

From the various threads I've read, it appears there needs to be a gap of 50mm between the tiles and insulation material in the eaves. Is 50mm the minimum value and is it a legal requiremnt?

However as our house is over 200 years old, there is no felt or any other material beween the rafters and tiles. There's also plenty of openings between the tile layers for the air to circulate. Does that mean the 50mm requirement doesn't apply as I've been told it depends on the build of the house?

Secondly, is 100mm of Kingspan the recommended size for insulation? Are there any benefits of going thicker? Assuming the 50mm restriction doesn't apply, I can put 90mm of kingspan between the rafters, and then add 40mm of Celotex insualting plasterboard, giving 130mm in total.

 

[freddiemercurystwin]

Your Lordship,

So there is a room in the roof? If you have no felt or other membrane then a 25mm gap is acceptable. So put in as thick insulation as you can, retaining a 25mm gap, then underlay a continuous layer of insulation. If you hit somewhere around 130mm insulation in total you will do a grand job. Separate insulation and plasterboard works out cheaper than using insulated plasterboard, if DIY. Seal up any gaps between the rafters and the insulation with expanding foam. Tape the gaps between the insulation with foil tape. Getting left over lots or factory seconds off ebay can be a cheaper source for insulation than merchants or the sheds etc. I wouldn’t worry too much about being ‘legal’ as technically the works you are proposing may require Building Regs approval if it is cost effective to do so.

 

[LordFrederickIII]

Thanks for the reply.

The loft is massive and would make a lovely chill out area when I get around to it.

Because I may convert it later, I asked building regs for their opinion and it would have to be 50mm.

So I'll be able to fit in 50mm between the rafters, and then 80mm on top, or maybe even 100mm.

With this old house the more the better I reckon