Passing flue through wall / roof

[markocosic]

Hello,

 

 

We have a wall / roof buildup as listed below.

 

My wife insists that we some holes ( ? ) though the wall/roof for a little log burner. 

 

I assume this will be double wall stainless and would like it through the wall if possible. I'm sure she'll want a vertical chimney through the roof instead. Constructions are much the same though.

 

 

How does one detail the air / water sealing on these?

 

The plasterboard won't give a stuff

The internal 12mm OSB is our airtightness and vapour retarder. The sticky tape used for taping those joints will turn to mush if used on a flue

The mineral wool won't give a stuff

The external wind barrier will likely melt if close to a flue

The board on board cladding (rough cut pine) needs water directing away from the end grain but should otherwise be ok with double wall flue

 

 

No building regs apply (summerhouse) but don't want to burn the place down or die either.

 

 

These "liners" for sale seem to be mineral wool in a metal sleeve:

https://www.topline.ie/plumbing-heating/plumbing/flue-pipe-accessories/flue-pipe-accessories/mi-flues/system-2/twin-wall-45-insulated-sleeve

https://www.schiedel.com/uk/products/additional-ranges/ignis-protect/

 

As most of the wall is mineral wool do we think a hole in the OSB with one of these in, and a hole in the wind barrier (backed up with some 6 mm OSB )with one of these in, would be appropriate?

https://www.flue-pipes.com/rubber-aluminium-flashing-184.html

 

Do you need to worry about water running on the outside surface of the flue tracking past the EPDM?

 

Photo examples of these through roofs and walls would be helpful!

 

 

A metal flashing for the wood cladding to redirect the rain from "under" the uphill board to "on top" of the downhill boards should be enough for diverting bulk water around the flue.

 

 

 

Buildup:

 

- 25 mm (double layer) plasterboard

- 45 mm service void with horizontal battens and soft mineral wool infill

- 12 mm OSB

- 195  (wall) / 245 (roof) mm stud/rafter with soft mineral wool infill

- 45 mm rigid mineral wool overlay

- 100 x 25 mm vertical wood strapping to hold mineral overlay

- Wind barrier (Jutadach 85 from memory)

- 50 x 25 mm vertical battens to hold wind barrier

- 45 x 45 mm horizontal battens (to hold cladding)

- 150 x 25 mm board on board cladding to roof/walls

 

 

Heat loss calculator - Cabin.xlsx

[Iceverge]

Looks fine to me. 

[ProDave]

Most twin wall flue manufacturers will specify a "distance to combustible materials" typically 50mm.  So your hole through the roof / wall needs to leave that clearance.

 

The supplier we used, flue-pipes-com supply an "insulated sleeve"  for that purpose.  The sleeve clamps to the pipe and is the required thickness, so the outside of the sleeve can by definition touch combustible materials.  It is also reasonable to assume since it was sold for the purpose the sleeve is not combustible so it can be in contact with the outside of the flue pipe.

 

So you cut your hole in the wall or roof to match the diameter of the sleeve and seal the joint between the sleeve and the wall / roof.

 

Use a standard flashing to prevent water ingress.

 

Here is my insulated sleeve being prepared to fit:

 

[markocosic]

Thanks - hole dia +50mm through the OSB and wind barrier; seal the gap to the flue with those flashings then.

 

They don't seem to sell those mineral wool sleeves any more ProDave - only the flashing collars that I linked above. I assume it's literally a hunk of mineral wool with a band around it; so little point in adding this if the flue is already passing through mineral wool (albeit one layer of rigid and one layer of squishy) 

 

I'll kick off the argument as to whether it goes through the wall or the roof next then ?

 

[dpmiller]

I used Ignis Protect on our build and it's a pretty handy way of filling a hole in the frame.