MVHR & Wood Stove

[Marko]

I live in a standard terraced house, and my MVHR intake and extract terminals are located about four tile courses below the ridge on the side opposite the chimney. I am considering recommissioning the existing chimney for a wood-burning stove, and I am concerned about whether smoke might be drawn back into the house through the MVHR system. If anyone has dealt with a similar setup, I would appreciate any insights into whether its worth the hassle or not.

[Alan Ambrose]

It probably depends on the exact geometry, prevailing winds direction etc (you don’t say whether the chimney is on the ridge or further down) but I would think yes it may well be a problem. Not too tricky to move vents elsewhere? I guess you could rough test it using a smoke source and then see whether the MVHR draws in smoke in practice?

 

Also, FYI there’s an issue with internal MVHR vents in the room with the stove - the idea being that you don’t want the MVHR to pull the smoke into the room. The latter issue is discussed in several threads here on BH.

[Andehh]

Our MVHR vents come through the same roof as our wood burner insulated chimney. Probably 3m horizontal and 2.5m vertical for seperation?

 

Rarely do we get wood smoke pulled through, but it does happen when the prevailing wind is just right!

[Marko]

Thanks for info both. The intake, on the left is fairly close to the chimney so unsure what to do. Might be that smoke blows over and past.

 

 

[G and J]

18 minutes ago, Marko said:

Thanks for info both. The intake, on the left is fairly close to the chimney so unsure what to do. Might be that smoke blows over and past.

 

 

Which direction does that window face?  
 

Also, are there any other houses in the terrace that current use their chimney?

[Marko]

1 minute ago, G and J said:

Which direction does that window face?  
 

Also, are there any other houses in the terrace that current use their chimney?

That window is north facing. No none else in the street seems to use their chimney. What do you reckon? 

[G and J]

1 minute ago, Marko said:

That window is north facing. No none else in the street seems to use their chimney. What do you reckon? 

Then your chimney is downwind of westerly winds, and I think the vast majority of the UK enjoys westerlies as their prevailing wind.   Assuming your MVHR unit is loft mounted you could also perhaps fit an additional carbon filtery thing in case of easterlies and other peeps bonfires.  
 

How airtight is your house and are you looking at direct air?

[Marko]

1 minute ago, G and J said:

Then your chimney is downwind of westerly winds, and I think the vast majority of the UK enjoys westerlies as their prevailing wind.   Assuming your MVHR unit is loft mounted you could also perhaps fit an additional carbon filtery thing in case of easterlies and other peeps bonfires.  
 

How airtight is your house and are you looking at direct air?

Thanks for the insight. I’ve been looking at carbon filter solutions on here, seems most diy them.

 

The house isn’t particularly airtight at the moment but it’s a work in progress Yes, I’d be looking at direct air with a duct to either outside or from under the suspended floor. 

[G and J]

30 minutes ago, Marko said:

direct air with a duct to either outside or from under the suspended floor

Anyone want to offer an opinion as to whether is a good idea to take combustion air from under a ventilated floor?