Advice on roof insulation?

[eljay]

I am renovating our attic bedroom in our terraced house and have taken out all of the plasterboard to reveal the slates and 75mm deep joists where i am considering putting kingpin Kooltherm K7 insulated board. As the depth of the beams is only 75mm, I believe I need to leave about 50mm clearance between the board and the bare slates where there are battons about 20mm thick.

 

Should I simply put in 50mm Kingspan or add extra wood to the beams (say 25mm) and insert 75mm Kingspan boards. I keep seeing conflicting information about this but is 50mm kingpin board equivalent to 100mm rock wall?

 

Any advice would be greatly appreciated.

Thanks

[dan2802]

You need 25mm air gap so 50mm Kingspan is the way to do it.

[per1]

I am renovating our attic bedroom in our terraced house and have taken out all of the plasterboard to reveal the slates and 75mm deep joists where i am considering putting kingpin Kooltherm K7 insulated board. As the depth of the beams is only 75mm, I believe I need to leave about 50mm clearance between the board and the bare slates where there are battons about 20mm thick.

 

Should I simply put in 50mm Kingspan or add extra wood to the beams (say 25mm) and insert 75mm Kingspan boards. I keep seeing conflicting information about this but is 50mm kingpin board equivalent to 100mm rock wall?

 

Any advice would be greatly appreciated.

Thanks

 

As Dan states 50mm Kingspan is the way to go.

Make sure the 25mm air gap is above the insulation.

Yes 50mm kingspan is equivalent to 100mm rockwool but dont fit this between the joists.

[eljay]

Thanks guys,

So that means that if I pin another 25mm of wood onto the joists, I can actually insert 75mm Kingspan board to make it equivalent to 150mm rock wool which should then comply with building regs/energy saving etc. I know it will be more work and more expense but probably worth it.

 

Am i making unnecessary work and expense for myself or would this be a good idea? I am no DIY fan but learning quickly.

Cheers

[biotechpete]

Building regs say to insulate to best practical standard when recovering the roof; I've got 50mm foil backed kingspan board and it's thick enough to stop the snow melting on the roof and it gets really hot in the summer.

 

I'd guess that the energy gain you'd get from the extra 25mm board would be lost to the neighbours poorly insulated roofs or cancelled out by the lack of cavity wall insulation anyway so not worth the hassle.

 

Edit to add: You can also get insulated / foil backed plasterboard which will give you more thermal insulation if you want it.

[eljay]

Thanks, that is great advice. I will stay with the 50mm kingpin board so there will actually be about 45mm airspace between the insulation and the slates. I have looked at insulated plasterboard with reflective coating and seems like a good idea swell.

Thanks a lot.

[dan2802]

To bring your roof up to current regs (say you were having a loft conversion), you'd have to fit 100mm KS !!!!

You'll be fine with 50mm.

[Steve51]

Thanks, that is great advice. I will stay with the 50mm kingpin board so there will actually be about 45mm airspace between the insulation and the slates. I have looked at insulated plasterboard with reflective coating and seems like a good idea swell.

Thanks a lot.

 

Id have a dust mask, goggles and gloves when cutting and fitting kingspan.. not a nice job

[biotechpete]

Id have a dust mask, goggles and gloves when cutting and fitting kingspan.. not a nice job

 

Kingspan is just a trade name for polyurethane foam board isn't it? It cuts and snaps fairly cleanly in my experience. Not like fitting rockwool.

 

AFAIK polyeuthane foam is totally inert; you could eat it without toxic effect.

[Steve51]

Kingspan is just a trade name for polyurethane foam board isn't it? It cuts and snaps fairly cleanly in my experience. Not like fitting rockwool.

 

AFAIK polyeuthane foam is totally inert; you could eat it without toxic effect.

 

Fitted loads of Kingspan.. If its 25mm you could use a stanley knife. 50mm use a handsaw [jetcut].. Theres loads of dust with it that makes you itch,especially when your fitting it above your head.. Ive never eaten it..