ᐅ Combustion Air Supply / Wood Stove – Thermo-Air Draft or Floor Slab
Created on: 26 Mar 2017 10:49
C
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
B
bierkuh8326 Mar 2017 23:40What kind of fireplace are you planning to have? Since you have talked to a fireplace installer, I assume you want them to build it for you? The reason I ask is that such a fireplace is not something you replace after 5 years...
The air supply can also be provided through a core drill/hole sleeve in the exterior wall and built in during construction.
The thermal air draft will work as well, although in bad weather conditions (storm) it might lead to reduced draft performance...
So just relax for now. None of the decisions you make will lead to disaster.
Do you have a controlled ventilation system because of the pressure sensor?
The air supply can also be provided through a core drill/hole sleeve in the exterior wall and built in during construction.
The thermal air draft will work as well, although in bad weather conditions (storm) it might lead to reduced draft performance...
So just relax for now. None of the decisions you make will lead to disaster.
Do you have a controlled ventilation system because of the pressure sensor?
D
Deliverer27 Mar 2017 10:38May I ask all "new build + wood stove" owners briefly how it is even possible to operate a chimney in the currently very well-insulated houses?
Due to the inertia of underfloor heating and the good insulation of the building envelope, I almost can’t imagine it working properly. I would first have to heat up a lot to get the stove to draw properly without sooting up the entire neighborhood. But until then, wouldn’t the indoor temperature already be at least four to five degrees higher? And only then would I be able to slowly burn individual logs for the ambiance, under low oxygen conditions. And then the temperature would rise even further, since the underfloor heating can’t shut off quickly.
On top of that, today very few people build large enough homes to maintain a distance of three or four meters from the stove permanently. And within that range, such a stove still emits quite a bit of heat by radiation. That would quickly become uncomfortable for me...
Do you then ventilate the excess heat out again? Or are there such small stoves that barely warm up the house? Where would I get small logs for those?
2Topic: Because of these concerns, I would currently avoid installing a chimney. At most, if you build about 200 square meters (2150 square feet), just meeting energy-saving regulations, with a gallery up to the roof AND the target temperature of the underfloor heating around 18°C (64°F). But I’m happy to be proven otherwise.
Due to the inertia of underfloor heating and the good insulation of the building envelope, I almost can’t imagine it working properly. I would first have to heat up a lot to get the stove to draw properly without sooting up the entire neighborhood. But until then, wouldn’t the indoor temperature already be at least four to five degrees higher? And only then would I be able to slowly burn individual logs for the ambiance, under low oxygen conditions. And then the temperature would rise even further, since the underfloor heating can’t shut off quickly.
On top of that, today very few people build large enough homes to maintain a distance of three or four meters from the stove permanently. And within that range, such a stove still emits quite a bit of heat by radiation. That would quickly become uncomfortable for me...
Do you then ventilate the excess heat out again? Or are there such small stoves that barely warm up the house? Where would I get small logs for those?
2Topic: Because of these concerns, I would currently avoid installing a chimney. At most, if you build about 200 square meters (2150 square feet), just meeting energy-saving regulations, with a gallery up to the roof AND the target temperature of the underfloor heating around 18°C (64°F). But I’m happy to be proven otherwise.
K
Knallkörper27 Mar 2017 12:38My experience after having lit the stove a few times, although we have not moved in yet, can be briefly summarized. Our living area is 56 m² (600 sq ft) with a ceiling height of 2.6 m (8.5 ft). We use softwood for heating. The stove has a large heat storage, so it warms up rather slowly but retains heat for a longer time:
- When the room has been at 22°C (72°F) from the underfloor heating beforehand, it becomes uncomfortable.
- Ideally, you should decide around midday whether to fire up the stove in the evening or not.
- When the whole house has cooled down to 14°C (57°F), the open living room door allows the upper floor to warm up as well. This does not take longer than 2 hours. The warmth is then very pleasant.
- If the stove has been heated for several hours and the heat storage is sufficiently warmed, the room remains warm the next morning.
- A clearance of 2 m (6.5 ft) should definitely be maintained; this has always been the case.
Regarding combustion behavior: Any properly functioning stove should draw well immediately. At the beginning, the stove is not fully loaded, so less combustion air is needed. Also, you should never regulate the output so much that the fire suffers from a lack of oxygen and burns inefficiently. This damages the stove. The output can reasonably only be varied by adjusting the amount of firewood.
Two reasons that do not justify the chimney for me, but explain it:
- Independence from the energy supplier (district heating), during power outages, etc.
- After a longer absence (heating off), fast reheating is possible.
- When the room has been at 22°C (72°F) from the underfloor heating beforehand, it becomes uncomfortable.
- Ideally, you should decide around midday whether to fire up the stove in the evening or not.
- When the whole house has cooled down to 14°C (57°F), the open living room door allows the upper floor to warm up as well. This does not take longer than 2 hours. The warmth is then very pleasant.
- If the stove has been heated for several hours and the heat storage is sufficiently warmed, the room remains warm the next morning.
- A clearance of 2 m (6.5 ft) should definitely be maintained; this has always been the case.
Regarding combustion behavior: Any properly functioning stove should draw well immediately. At the beginning, the stove is not fully loaded, so less combustion air is needed. Also, you should never regulate the output so much that the fire suffers from a lack of oxygen and burns inefficiently. This damages the stove. The output can reasonably only be varied by adjusting the amount of firewood.
Two reasons that do not justify the chimney for me, but explain it:
- Independence from the energy supplier (district heating), during power outages, etc.
- After a longer absence (heating off), fast reheating is possible.
C
Cruiseaddict27 Mar 2017 15:04Thank you for all the opinions.
In fact, we only want a wood-burning stove.
The ventilation system is intended to ensure that the living area of about 45 sqm (480 sq ft) does not overheat and that the warmth is distributed throughout the entire house. Primarily, the stove should provide a bit of “romantic” coziness. That it also heats is secondary for us.
The more interesting question for us is whether to use the combustion air supply via the thermal air duct in the chimney or, as the stove installers generally prefer, to draw the fresh air through the floor slab.
As some have mentioned here, condensation seems to be primarily a problem with fresh air supplied through the floor slab. The thermal air duct in the chimney, however, may cause difficulties when lighting the fire.
Does anyone here have a wood-burning stove operating with controlled living space ventilation and can share experiences regarding the draft through the chimney?
We are also not very comfortable with having a hole in the floor through which cold air—and in the worst case even pests—could enter our highly insulated home.
Thanks for your support,
In fact, we only want a wood-burning stove.
The ventilation system is intended to ensure that the living area of about 45 sqm (480 sq ft) does not overheat and that the warmth is distributed throughout the entire house. Primarily, the stove should provide a bit of “romantic” coziness. That it also heats is secondary for us.
The more interesting question for us is whether to use the combustion air supply via the thermal air duct in the chimney or, as the stove installers generally prefer, to draw the fresh air through the floor slab.
As some have mentioned here, condensation seems to be primarily a problem with fresh air supplied through the floor slab. The thermal air duct in the chimney, however, may cause difficulties when lighting the fire.
Does anyone here have a wood-burning stove operating with controlled living space ventilation and can share experiences regarding the draft through the chimney?
We are also not very comfortable with having a hole in the floor through which cold air—and in the worst case even pests—could enter our highly insulated home.
Thanks for your support,
Deliverer schrieb:
May I briefly ask all owners of "new builds + wood stoves" how it is even possible to operate a chimney in today’s highly insulated houses?Not at all. That’s why, in new builds, only a small masonry heater makes sense if at all. Of course, this costs significantly more.
Cruiseaddict schrieb:
The ventilation system is supposed to ensure that the living area of about 45 square meters (484 square feet) does not overheat and that the heat is distributed throughout the entire house. Our energy consultant and architect strongly advised against this approach. Generally, I am rather skeptical of all warm-air heating systems because, first, a lot of heat accumulates near the ceiling, and second, convection stirs up and spreads dust. In addition, radiant heat is considerably more comfortable.
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