Vapour barriers

Bill the Bass

Member
Livestock Farmer
Location
Cumbria
Currently doing some building works on a small cottage, if I use an insulated plaster board with a vapour control layer do I still need to put a vapour barrier between the insulation in the timber frame and the plaster board to comply with building regs?

Spent all morning searching impenetrable sh1te on the planning portal and still no nearer!

TIA
 

Uggman

Member
Livestock Farmer
Currently doing some building works on a small cottage, if I use an insulated plaster board with a vapour control layer do I still need to put a vapour barrier between the insulation in the timber frame and the plaster board to comply with building regs?

Spent all morning searching impenetrable sh1te on the planning portal and still no nearer!

TIA
We never have done vapour barrier and we do I do agree we @br jones thuo with having the air circulating lots of barn conversions over the last few years .But it might different with each inspector private ones are a lot less strict than the council ones but to be honest I still prefer the council ones the private ones are just box tickers and I think it will come back and bite them on the arse!
 

Zedlock

Member
Trade
Currently doing some building works on a small cottage, if I use an insulated plaster board with a vapour control layer do I still need to put a vapour barrier between the insulation in the timber frame and the plaster board to comply with building regs?

Spent all morning searching impenetrable sh1te on the planning portal and still no nearer!

TIA
This might not be very helpful if you have already bought your insulation-backed plasterboard, but...
having just completed similar work at Zedlock HQ, I would recommend using separate insulation, and foil-taping the joints. The foil tape will act as a vapour and radiant barrier. If you are using PIR sheets between the studs use 100mm wide foil tape (Toolstation are good for this) to cover the stud. Using separate insulation and plasterboard will also mean less waste.
 

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Dry Rot

Member
Livestock Farmer
This might not be very helpful if you have already bought your insulation-backed plasterboard, but...
having just completed similar work at Zedlock HQ, I would recommend using separate insulation, and foil-taping the joints. The foil tape will act as a vapour and radiant barrier. If you are using PIR sheets between the studs use 100mm wide foil tape (Toolstation are good for this) to cover the stud. Using separate insulation and plasterboard will also mean less waste.
I've never really followed the logic of that. How much heat is lost through a gap a few millimetres wide that is closed by the timber batten? My head stays warm if I wear a balaclava, despite there being holes for my mouth and eyes.
 
I've never really followed the logic of that. How much heat is lost through a gap a few millimetres wide that is closed by the timber batten? My head stays warm if I wear a balaclava, despite there being holes for my mouth and eyes.

I'm told Thermal Bypass ,gaps around insulation has a massive effect.


Closed loop” convection can result in significant failures in thermal performance. In principle this is driven by stack effect. A range of studies have shown that even narrow air gaps between the (internal) air barrier and the insulation and small gaps in the joints between insulation have been shown to result in significant heat loss. The proportionate impact of the convection increases as the U-value is improved. An increase in heat loss of about 160% greater than the calculated U-value is not uncommon when air gaps exist behind the insulation.
 

HatsOff

Member
Mixed Farmer
Lose a lot more heat via convection (air movement/drafts) than conduction (heat loss through walls).

First thing I told homeowners to do is eliminate drafts then worry about insulation. Although you do need to consider ventilation, there's a big difference between controlled ventilation and a draft...
 

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