Seeking airtight stove pipe advice

[BUBBLES67]

Hi

Our new build home is now in the final few months but issues cropping up every day.  We are ‘aiming towards’ passive house without going all the way. Triple gazing. Ultra insulated with additional Passive Purple membrane to enhance airtightness. At first fix stage. UFH pipes & screed down. Most MVHR pipes in place. ASHP in place.   Will also have 22  Pv solar panels. 

 

We are installing a wb stove (external air supply only) but stove company said they need 50mm around flue pipes to be A1 non combustible & had talked about this being a space around the flue exit. Obviously this won’t work with our airtight plans. Can’t find any A1 rated fire mastic. How do others seal the flue into wall exit?

 

I know from many previous threads many have views on necessity WBS in airtight home. Understand but it’s going in anyway. 

 

Advice would be appreciated. 

Thx. 

[Tom]

Hi - I was researching similar things on here recently and was helpfully pointed in the direction of this https://www.schiedel.com/uk/products/additional-ranges/protect-box/

Might do the trick for you.

Annoying that most installation companies seem to have absolutely no idea what you are talking about when you try and discuss airtightness etc.

[ProDave]

When I bought my flue pipes the manufacturer sold an insulating sleeve for this purpose.

 

 

That's a test run with the angle cut to match the roof.  

 

The sleeve is obviously non combustible or it would not be sold for that purpose and the outside is >50mm from the flue so your insulation or combustible materials can touch the outside of the sleeve.

[nod]

Job done 

[BUBBLES67]

8 hours ago, Tom said:

Hi - I was researching similar things on here recently and was helpfully pointed in the direction of this https://www.schiedel.com/uk/products/additional-ranges/protect-box/

Might do the trick for you.

Annoying that most installation companies seem to have absolutely no idea what you are talking about when you try and discuss airtightness etc.

Thanks Tom.  I’ll take a look.

[BUBBLES67]

8 hours ago, ProDave said:

When I bought my flue pipes the manufacturer sold an insulating sleeve for this purpose.

 

 

That's a test run with the angle cut to match the roof.  

 

The sleeve is obviously non combustible or it would not be sold for that purpose and the outside is >50mm from the flue so your insulation or combustible materials can touch the outside of the sleeve.

Thanks ProDave.  That makes sense, and it is the >50mm from combustible materials (or rated A1) that is causing the issue.  All the Fire Mastic and sealants seem to be max B1 rated.  Just don’t want them cutting massive holes through my mega insulated walls and Passive Purple membrane!  

[zzPaulzz]

@BUBBLES67 Did you find a good solution in the end?