Help with Twinwall Flue Detail Through Timber Frame

[Stratman]

Apologies if this has been concluded elsewhere on the forum - I've trawled and was unable to find a solution.

 

My timber frame is up, windows in, roofing on, cladding commenced.

 

I understand the sentiment surrounding log burning stoves being an expensive folly in a well insulated home, but we are determined nevertheless.  The issue is that I cannot seem to find conclusive advise on the detail to pass a twinwall flue through the external timber frame wall at a 45 degree angle that satisfies building regulations and hopefully prevents the insulation from melting and the house bursting into flames ...which would be a bad thing!  I've found Schiedel products such as the Ignis but the diagrams and discussions never seem to match my build up which is:

 

 

AI helpfully suggests a gap between the flue and combustibles left completely empty with no insulation or airtightness!!!

 

Can anyone help, please?  Preferably with a solution that has actually been installed and signed off by building control.

 

Thanks

[ProDave]

I found an "insulated sleeve" for the purpose when I bought my flue.  It is designed to clamp onto the outside of twinwall flue so must be non combustible to be able to do that, and is 50mm thick which then leaves anything that is combustible >50mm from the flue.

 

 

The reality is my 5Kw stove even burning full tilt, the outside of the twin wall flue where it passes through the roof is barely warm to the touch.  

[JohnMo]

3 minutes ago, Stratman said:

AI helpfully suggests a gap between the flue and combustibles left completely empty with no insulation or airtightness!!!

I framed out where the hole for the flue went through our roof (your wall in this case), using PIR insulation. The size was slightly larger than the distance required from combustible material. This left a closed void. Then filled the void after flue installed with Rockwool as it's a none combustible insulation.

 

Then to get the airtightness back I used a flanged flue rubber diaphragm and taped to the the airtight membrane.

 

 

[Stratman]

Both useful suggestions. Thank you.

 

Does the insulated sleeve get cut back to the external face of the OSB then taped?  What happens as the twinwall passes through the battening void and then the timber cladding?  Presumably there would have to be a 50mm gap from the edge of the flue to the combustible cladding.

[JohnMo]

You can get trim plates to cover gaps