Makeup air from downstairs bedroom

[dougstove]

Hello;
I am running a Pacific Energy Super27, nearly 24/7 for Dec-March, and often in the shoulder seasons.
I have a long ranch house.
The stove is in a big room that takes up 1/3 the house.
28 ft from the stove location, there is a 2 story section, with a lower level, with 2 bedrooms (below an upper level with 2 bedrooms).
The stove heats the entire house well, except the lower level.
I have been wondering about running a 28 ft duct from the lower level to provide make up air to the stove. The duct would be level (or nearly so) and nearly straight (no corners), running through a heated basement that underlies the section of house between the stove and the down stairs bedrooms (sounds confusing...but actually simple).

The goal would be to take cool air from the bedrooms, use it for combustion air, and encourage a net airflow down to the bedrooms.
But, reading other posts, I am starting to guess this is a bad idea? Risks of CO backflow to the lower bedrooms???

My house is 40 years old, and rates about 75 on a Canada air-tightness scale from 0 (twig hut) to 100 (for R-2000 construction).
cheers, Doug

 

[fossil]

Hello;
I am running a Pacific Energy Super27, nearly 24/7 for Dec-March, and often in the shoulder seasons.
I have a long ranch house.
The stove is in a big room that takes up 1/3 the house.
28 ft from the stove location, there is a 2 story section, with a lower level, with 2 bedrooms (below an upper level with 2 bedrooms).
The stove heats the entire house well, except the lower level.
I have been wondering about running a 28 ft duct from the lower level to provide make up air to the stove. The duct would be level (or nearly so) and nearly straight (no corners), running through a heated basement that underlies the section of house between the stove and the down stairs bedrooms (sounds confusing...but actually simple).

The goal would be to take cool air from the bedrooms, use it for combustion air, and encourage a net airflow down to the bedrooms.
But, reading other posts, I am starting to guess this is a bad idea? Risks of CO backflow to the lower bedrooms???

My house is 40 years old, and rates about 75 on a Canada air-tightness scale from 0 (twig hut) to 100 (for R-2000 construction).
cheers, Doug

It's OK for you to run a duct from the lower bedroom area and exhaust it into the room in which the stove is located. This would undoubtedly require an inline fan to achieve any sort of effectiveness. It's NOT OK for you to run that duct from the downstairs bedroom area up and somehow directly connect it to the stove. You would risk reversing the airflow through the stove, whereby it would draw its combustion air down the flue and exhaust its combustion products down the duct into the downstairs bedroom area. Rick

 

[Backwoods Savage]

Doug, before you go to that work, have you tried blowing the cool air into the warm room? I'd try sitting a small fan right by the bedroom door and blow towards the heat.

It does work! Blow the cool air towards the warm room and that cool room will warm. Sounds contrary but it works.

 

[LLigetfa]

The volume of combustion air drawn would not provide the air changes needed. Draw the combustion air from outside to limit air infiltration and blow cold air from the room up to the stove.

I draw outside air for combustion and I suck cold air up from my crawlspace to the stove. The warm air gets drawn down into the crawlspace and warms the floors.

 

[oconnor]

Doug

Your basement is a relative negative pressure zone compared to your other floors. You would risk the issues Fossil descibes. Give the Woodburning Guide in my signature block a read - lots of detail on that and other issues associated.

 

[begreen]

I'd get an electric heater for that bedroom. It will give better results. If the walls and floor are not insulated, that is where to invest.

 

[dougstove]

Update on the project:
Summary: a cold air return cut our winter electricity consumption by 1/3.
Details:
In December 2008 we were using 2 electric wall mount heaters to heat the downstairs bedrooms. Our electric consumption for that month was 2100 kWh. We were burning the PE Super27 nearly 24/7 in that month, and used about a cord of wood.

In Fall 2009, I installed a simple cold air return; a Y-shaped 4" duct system that takes cold air in from the floor level of each of the downstairs basements, connects the 2 lines to a common Fantech FG4 inline fan, and then exhausts the cold air to the floor beside my stove; total duct distance about 35' through an insulated basement, with a rise of about 3'.

In December 2009, our electric consumption was 1300 kWh. We again burned the PE Super27 nearly 24/7. The weather conditions in the two years were similar. Wood consumption in 2009 was similar, perhaps a bit lower.
The differences were:
-downstairs electric heat turned off (the savings)
-running the Fantech FG4 nearly non-stop (minor new cost).
-running a dehumidifier in the downstairs most days (not directly related to the project, but solving a design flaw in the house that caused condensation problems in the cooler lower levels.).

So, the entire house is enjoying more even heat; previously, the stove room got uncomfortably hot, and the downstairs was frigid, with fairly bad drafts through the main part of the house. Now, we have a more comfortable, gentler gradient. The downstairs bedrooms are dry, due to the dehumidifier.

At my electricity rates the project should pay for itself in about one winter/spring (net saving $60-70 per month; project material cost was about $300).
Thanks for the various advice.

Drawbacks: There is a moving air noise that is noticeable if the house is quiet. Although, setting the fan to 'low' drops the noise to almost nothing.
Ideally, I would have preferred 6" ducts, which probably would have been quieter, but the duct installation was more feasible with 4"; I had 3 tight spaces to snake through.
A well-connected scrounger probably could have done it for quite a bit less.