insulating a stone walled cottage (moved)

[MarkSSL]

Hi All,
We bought a circa 1880 stoned walled cottage back in April with a barn annex. So far we have replaced both slate roof's. Now we're looking to insulate both. The main house roof will be a trapezium shape, I.e. angled across, then flat and back down. The flat part will be filled with insulation blanket. Its the angled parts I'm a bit confused with. BTW building regs aren't involved as its a refurb. I've looked at insulation boards and their huge prices. And the cheaper Rockwool, Isover Metac etc etc. I'd rather not use boards as it will affect our budget. It's not a huge property the internal roof area being about 60m2 on both. The rafters are only 3" x 2" sitting on purlins and A frames.
Can anyone please offer an advice on the best cost effective solution?
Thanks

 

[IWalkLikeHimaMartian]

Insulation between rafters (with the required air gap to membrane) then insulated plaster board under rafters.
You have little choice for under the rafters. And the available space between rafters leaves you with little alternative choices.

An alternative would have been to insulate over the rafters with a foil type insulation. But that still requires something like 50mm celotex or similar between rafters.
You could also use the foil under rafters.

I suspect Building regs' ought to be involved. just because it is a refurb' does not mean that BRs are omitted.

https://www.specifiedby.com/quinn-therm/between-below-rafter-insulation

https://www.just-insulation.com/ref...-pitched-roof-wall-multi-foil-insulation.html

 

[MarkSSL]

Insulation between rafters (with the required air gap to membrane) then insulated plaster board under rafters.
You have little choice for under the rafters. And the available space between rafters leaves you with little alternative choices.

An alternative would have been to insulate over the rafters with a foil type insulation. But that still requires something like 50mm celotex or similar between rafters.
You could also use the foil under rafters.

I suspect Building regs' ought to be involved. just because it is a refurb' does not mean that BRs are omitted.

https://www.specifiedby.com/quinn-therm/between-below-rafter-insulation

https://www.just-insulation.com/ref...-pitched-roof-wall-multi-foil-insulation.html

Thanks for your reply.
Firstly regarding BR’s we initially applied to the local planning department for clarification on what was required in terms of planning and building regs prior to purchasing the property. A visit was carried out by their planning officer who confirmed in writing that we did not need either as it was classed as a refurb not rebuild. Since then we have contacted the local building inspector and informed him of what we’re doing and he also stated he didn’t need to involved. Either way we are using a local builder on some jobs who works to BR’s.
I’ve read in a period property manual that we have to use only breathable insulation materials otherwise we will end up with a warm damp house.