Wood burning stove combined with MVHR

joekozelka

Has anyone any experience in combining the exhaust of a wood burning stove or fireplace with Machanical Ventilation with Heat Recovery Unit? What are the issues?

tony

soot smoke tar and carcinogens

joe90

I am sure Joekozelka is not proposing to re-cycle smoke through a property!!!! I think it is a good idea in theory, there are some stove chimney heat exchangers for heating water on the market but unless the stove is running for many hours a day (which it would not in a well insulated house) I think the return would be minimal.

Perhaps a better way would be to have large thermal mass around the stove to absorb the heat (as a thermal flywheel) and run the inlet pipe for the MVHR through this mass to raise the temp of the air?

bgp

Back pressure and risks of corrosion and deposits in the flue (from condensation due to the lower temperature on the back side of the heat exchanger)? The exhaust gas from an efficient stove or boiler shouldn't be much hotter than needed for proper venting. Perhaps it's an option if you have an inefficient stove. But I'd be speaking to a heating engineer before I considered something like this. The dangers are serious enough to deter a trial-and-error approach.

joekozelka

A few years back I was lodging with a friend and had managed to source a truckload of wooden pallets for his fire. I noticed that most of the heat was lost up the chimney. Heat exchangers take heat out of the exhaust air and return as much as 90% back into a house. This was back in the early 90's when the concern was the cost of keeping warm.
I would have thought a well-designed system could be used to heat up a whole house with the fire in the front room. "How hard can it be?"
Just off the cuff and I am not a heating engineer but the chimney or wood burner exhaust could be sent through the heat exchanger or have its own separate heat exchanger set up for easy cleaning. The potential is there. How many houses in this country already have fireplaces?

Part of the reason that I asked is because I am currently designing a zero carbon house for a client who has access to all the firewood he needs. I have thought of this years ago when I first read about heat exchangers. I have also seen it on the net. I would like to hear from anyone who has any experience with this.

joekozelka

I like the thermal Mass idea as the heart would be stored longer and it would do away with any problems with fouling the heat exchange unit. Perhaps the thermal store could be made by pouring concrete around the wood burner with air ducting in place. Natural stones could be used as a shutter to retain the concrete when wet as well as offering an aesthetically pleasing surround.
Thanks Jo90!
:bigsmile:

joe90

see
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1169

squowse

i think the exhaust of some modern wood burners is pretty cold. to the extent that you can get get back draughts if you are not careful.