ᐅ Combustion Air Supply / Wood Stove – Thermo-Air Draft or Floor Slab
Created on: 26 Mar 2017 10:49
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Cruiseaddict
Hello community,
In the next few days, we will need to decide how to manage the fresh air supply for the wood-burning stove planned for our yet-to-be-built single-family home without a basement, built to KfW 55 standard.
Currently, a single-flue chimney with a thermal air supply (from Schiedel) is planned. The stove will be installed against an exterior wall. Stove installers frequently point out that supplying combustion air through a thermal air duct is not ideal and that using an intake through the floor slab would provide better results and could also save money.
Now we are wondering if this might cause problems that we actually want to avoid. Also, replacing the stove later could be complicated since the new one would have to have the exact same dimensions if the fresh air comes through a floor connection, right?
After already having to accept that we will need a pressure monitor, the fresh air supply issue is making us a bit uneasy. At times, we are even considering abandoning the whole stove idea. After all, we do have a heating system.
What are your opinions on these two fresh air supply options?
Regards
In the next few days, we will need to decide how to manage the fresh air supply for the wood-burning stove planned for our yet-to-be-built single-family home without a basement, built to KfW 55 standard.
Currently, a single-flue chimney with a thermal air supply (from Schiedel) is planned. The stove will be installed against an exterior wall. Stove installers frequently point out that supplying combustion air through a thermal air duct is not ideal and that using an intake through the floor slab would provide better results and could also save money.
Now we are wondering if this might cause problems that we actually want to avoid. Also, replacing the stove later could be complicated since the new one would have to have the exact same dimensions if the fresh air comes through a floor connection, right?
After already having to accept that we will need a pressure monitor, the fresh air supply issue is making us a bit uneasy. At times, we are even considering abandoning the whole stove idea. After all, we do have a heating system.
What are your opinions on these two fresh air supply options?
Regards
C
Cruiseaddict27 Mar 2017 18:40I feel misunderstood. We have a heat pump with underfloor heating, not a warm air heating system. The mechanical ventilation with heat recovery is installed for basic ventilation and because we want that level of comfort. Dust should be less of an issue as a result.
Nevertheless, we would like to have a small wood-burning stove. The mechanical ventilation with heat recovery should address the concern about local overheating that was mentioned earlier.
My concern here is the supply air, not whether radiant heat would feel more comfortable.
In the end, I have already read some arguments against draft from under the floor slab, and the disadvantages of draft through the chimney seem negligible in comparison.
Thanks to everyone who has provided helpful answers here.
Nevertheless, we would like to have a small wood-burning stove. The mechanical ventilation with heat recovery should address the concern about local overheating that was mentioned earlier.
My concern here is the supply air, not whether radiant heat would feel more comfortable.
In the end, I have already read some arguments against draft from under the floor slab, and the disadvantages of draft through the chimney seem negligible in comparison.
Thanks to everyone who has provided helpful answers here.
Sorry, my fault! You already mentioned earlier that you want the fireplace not for heating, but for aesthetics and coziness. Then everything fits.
I just wanted to point out that a fireplace is generally not suitable for heating. It’s possible that people reading this now or later might want to use a wood stove for heating. That’s why I made the comment.
I just wanted to point out that a fireplace is generally not suitable for heating. It’s possible that people reading this now or later might want to use a wood stove for heating. That’s why I made the comment.
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bierkuh8327 Mar 2017 22:43Bamue89 schrieb:
Our chimney specialist recommended a LAS chimney system for the new build. As mentioned before, this is a chimney with a “double flue.” Reasons:
Since air passes through the floor slab, a kind of draft constantly occurs due to the air exchange. This is usually prevented by a pressure flap installed in the wall at the fresh air duct outlet.
The air coming through the floor slab is much colder in winter, which can cause condensation below the combustion chamber and negatively affect the chimney’s lifespan.
!I would be interested in a brief explanation of how that is supposed to work.
Otherwise, from my experience with chimneys so far, I can only say that the chimney really heats the house well. That’s what it’s supposed to do; for me, it’s part of the overall feeling. If it gets too warm, we just crack open the patio doors briefly.
The only thing that bothered me was the very dry air caused by convection. We don’t have a mechanical ventilation system.
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Cruiseaddict28 Mar 2017 05:23All right. Thanks for the clarification.
Bierbrauer8417 May 2017 10:05Hello everyone,
Although this topic is a bit older, we are currently facing the same issue.
We want to build a single-family house meeting the KfW55 reference standard. We will install a ventilation system with heat recovery (mechanical ventilation with heat recovery) and are considering, or would like, to have a masonry fireplace (fireplace kit) installed in the open kitchen/dining/living area (about 53 m² (570 sq ft)).
Our architect pointed out that this fireplace must be certified as airtight with room-air independence to avoid any surprises during the later blower door test and to ensure that the limit values are not exceeded if the fireplace is not airtight.
We recently visited a stove maker and expressed our wish for a masonry, room-air independent fireplace. He recommended a "LAS fireplace" and mentioned that he regularly installs these in new builds and KfW houses.
Does anyone here have experience with the interaction between a "LAS fireplace," blower door testing, and KfW standards? Does this work as expected, or is there a risk of failing the blower door test and potentially losing KfW funding?
Thank you very much.
P.S. A pressure monitor is included in the planning.
Although this topic is a bit older, we are currently facing the same issue.
We want to build a single-family house meeting the KfW55 reference standard. We will install a ventilation system with heat recovery (mechanical ventilation with heat recovery) and are considering, or would like, to have a masonry fireplace (fireplace kit) installed in the open kitchen/dining/living area (about 53 m² (570 sq ft)).
Our architect pointed out that this fireplace must be certified as airtight with room-air independence to avoid any surprises during the later blower door test and to ensure that the limit values are not exceeded if the fireplace is not airtight.
We recently visited a stove maker and expressed our wish for a masonry, room-air independent fireplace. He recommended a "LAS fireplace" and mentioned that he regularly installs these in new builds and KfW houses.
Does anyone here have experience with the interaction between a "LAS fireplace," blower door testing, and KfW standards? Does this work as expected, or is there a risk of failing the blower door test and potentially losing KfW funding?
Thank you very much.
P.S. A pressure monitor is included in the planning.
B
bierkuh8317 May 2017 23:36The BDT is not necessarily related to the chimney... It could also be done before the chimney is installed. In that case, the chimney connection is sealed off. Otherwise, everything you need to know about controlled residential ventilation and chimneys is described here...
The risk of failing the BDT is low. In the worst case, troubleshooting and fixing the issue will be necessary.
The risk of failing the BDT is low. In the worst case, troubleshooting and fixing the issue will be necessary.
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