cavity insulation

smulldoon · 29 Jun 2009

Hi,

I'm building a cavity wall conservatory which will be used as a kitchen. The walls will be constructed using red fletton bricks on the outside and thermal blocks inside. The height of the walls will be 1200mm. What is the minimum cavity width, and therefore the thickness of Celotex that would achieve the insulation required by regs? The structure will be under regs because I will be putting heating and drainage in too. Cheers

noseall · 29 Jun 2009

I'm building a cavity wall conservatory which will be used as a kitchen.

The structure will be under regs because I will be putting heating and drainage in too. Cheers

A conservatory currently does not fall under building regulations.

It is possible to have a polycarb' roof and still satisfy reg's but it may mean having solid walls!

You need to design a hybrid that will satisfy reg's, not impossible but it may mean a compromise.

jeds · 29 Jun 2009

If it is heated, for building regulations purposes it would be treated as an ordinary extension. Minimum U-value of new walls would therefore be 0.30W/m²K. You would get that with 50mm Celotex in a 100mm cavity or 75mm full fill cavity batts with lightweight internal block.

You might run into some tricky questions if your glazed area is more than 25% of the floor area. Although I find this rule is often completely ignored by building control.

freddiemercurystwin · 29 Jun 2009

I've found to get round the 25% rule and avoid SAPs you need to up the U value of the glazing. You'll have to see what BC ask for and a bit of negotiation will be in order.

noseall · 29 Jun 2009

jeds said:
if your glazed area is more than 25% of the floor area.,............I find this rule is often completely ignored by building control.

I rarely find this rule completely ignored in Staffs. In fact i would say it is zealously obeyed. However i will agree that it is a rule that can be interpreted/overcome in several ways, particularly if you have a sharp designer/architect/draughtsman.

mikric · 29 Jun 2009

Glazing can normally be overcome in some form of trade off. What kind of roof are you going to use glazed or plastic or tiled, you are calling it a conservatory when it will actually be an extension with kitchen installed. 25% rule certainly not ignored in my area.

Shytalkz · 29 Jun 2009

Mud huts have glass in them these days, Mik?!

mikric · 30 Jun 2009

Shytalkz said:
Mud huts have glass in them these days, Mik?!

Yeh but they are usually less than 30m2 so exempt

Shytalkz · 30 Jun 2009

Touché

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cavity insulation

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