kingspan sloped roof insulation?

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problemchild75

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i have just had a ground floor extension built with a vaulted ceiling and have today insulated between the rafters installed kingspan, i have pushed this right up to the membrane below the tiles and i fear i may have done the wrong thing and should have left an air gap. do i need to rip it all down or will it be ok. if i do need to leave an air gap and have not what problems might i expect. i still need to install another layer of 30mm could i leave the air gap between the 100mm and the 30mm.
your promt responses would be appreciated before i start boarding.
TIA
Jamie
 
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I would assume that any new extension would have a breather membrane not felt so in that case you must leave a 50mm gap between the membrane and insulation. Total thickness of insulation should be 130mm so depending on the thickness of your rafters you can work out what you require.

Should have used tri-iso!!
 
the use of breathable membranes is now becoming common practice and according to the manufactures information ventilaton is not required in warm roof construction, however many house builders still prefer to ventilate. unless you put the insulation on top of the rafters.

Many breathable membranes now have the BBA certiication. see kingspan nilvent.

However the membrane must be insalled correctly and in a non ventilted situation with insulation tight to u/s of membrane. i.e top of rafter the membrane should be fully tort and counter battened. if it isn't the membrane should be allowed to drape 15mm between the rafters to allow surface water to run below the tiling battens.

Personally i would always ventilate in which case 50mm required above insulation.
 
tri iso is no longer up to current building regs , needs 25mm celotex etc to bring up to acceptable current requirements.
 
the jury is still out on breathable meb's.

they are fine as long as the whole roof has b.m.

it is when you build an extension and cut into an existing roof without b.m. that the problems start.

building control (staffs) will not accept a situation whereby one section of roof is regular underslaters felt and the other or new addition is breathable, whereby the air is free to flow betwixt the two.
 
obviously a typo 50mm, tri iso is back in use in certain parts of the country ie sw London for sure as we have just done a couple of lofts up there.
 
Sorry guys - incorrect to say tri-iso no longer conforms - we have just used it on 3 house extensions.

People need to check with local BCO as it varies from county to county!!
 
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