Ducting heat to other rooms

[brider]

I'm sure I'll get the 'ol "try the SEARCH button" responses, but I DID, and wasn't able to use the right buzzwords to get any meaningful info...

I haven't posted in over 4 years, but this site was ESSENTIAL to my successful installation (all by myself, I might add) of my Harmon Oakwood stove. Stourrent dilemve has paid for itself many times over by now.

Current dilemna: The stove is in a room with vaulted a vaulted ceiling, and "vaulted" face of (1) wall is just my open attic on the other. It's a small, standard ranch house, and I've often thought it would be AWESOME if I could duct all that hot air thru that vaulted face thru the attic, to the (2) end bedrooms. I have room to do this easily, but what I need is the proper in-duct blower and thermostat or switching schematics.

Can anyone steer me to the discussion on this subject? I'm sure it's been done before.

 

[Backwoods Savage]

Just remember that it is always difficult to try to move the warm air by forcing it into the cooler air. This is why most will use a simple and small desktop fan. The trick is to set it on the floor, like in a hallway or doorway. Run it on the lowest speed setting and blow the cooler air into the warmer room. Of course as you move the cool air into that room, some has to move out and it is the warm air that will move out. The denser cool air moves a lot easier into the less dense warm air. For sure, there is not a lot of difference in the denseness of the cool vs warm in the house but there is a difference. Work with it rather than against it. It is the same with the ceiling fans. In winter, blow the air up rather than down. Reverse it in the summer.

 

[brider]

Since there's no practical way for me to put a floor or box fan anywhere to blow the cold air down the hallway, I put a pedestal fan near the "stove room" door to draw the heat at about head-level out of that room and distribute it down the hallway. Seems to work.

However, in the vaulted "stove room", the heat up against the ceiling gets trapped until it washes down the walls. One upper wall has an A/C vent in it, coming from my attic-mounted A/C air handler.

Why couldn't I run an ADDITIONAL vent mounted in the same wall, and duct it thru the attic to the back bedrooms, where the A/C ducts also emerge? This would move the superheated air in the stove room that's trapped against this wall. It would require an in-line fan and thermostat, but this HAS to be HVAC 101.

Has anyone done this?

 

[begreen]

Running a duct through the cold attic is bound to have heat loss. The ducts need to be very will insulated. You would be better to suck air out of the cold bedrooms and blow it into the stove room. Warm air will replace the displaced bedroom air via the hallway as long as the bedroom doors are open to allow air to convect.

 

[Backwoods Savage]

Since there's no practical way for me to put a floor or box fan anywhere to blow the cold air down the hallway, I put a pedestal fan near the "stove room" door to draw the heat at about head-level out of that room and distribute it down the hallway. Seems to work.

However, in the vaulted "stove room", the heat up against the ceiling gets trapped until it washes down the walls. One upper wall has an A/C vent in it, coming from my attic-mounted A/C air handler.

Why couldn't I run an ADDITIONAL vent mounted in the same wall, and duct it thru the attic to the back bedrooms, where the A/C ducts also emerge? This would move the superheated air in the stove room that's trapped against this wall. It would require an in-line fan and thermostat, but this HAS to be HVAC 101.

Has anyone done this?

Once again, moving the cool air works much better than trying to move the warm air into the more dense cool air. Not sure why you could not set a small fan on the floor. This is what we use:

It is a 7 1/2" diameter so the footprint is very small. We also run it on low speed.

 

[westkywood]

I did this very thing. I put ducts going to 2 bedrooms. I have a thermostat behind the stove , which I reversed the wires on, that kicks on when the stove gets good and hot, then turns off when it cold down so its not blowing cold air. The draw vent is directly over the stove. One 10" duct that branches off into two 6" vents. One 10duct fan and two 6" duct fans at the end of each run. It actually works very good. Blows good hot air. I have the ducts buried in loose insulation. I know I'm bound to loose some heat through the ducts.
Since my daughter moved out and its just me here, I havent used it. I keep that bedroom door cracked now to get just enough heat in there to keep it like 55 degrees. On really cold nights I just put an oil filled heater in there to compensate rather than blowing my wood heat in there.

 

[begreen]

A return vent directly over (or within 10 ft.) is against code.

 

[Minnesota Marty]

Here is a link to a small company that I have used when clients have had the inbalance of hot to cold on various levels. Specifically I have used the Balance Booster system. Always use insulated ductwork and Begreen is 100% correct, minimum of 10 feet from the stove or fireplace. Better yet the other side of the room
www.tjernlund.com/newproducts.htm

Works well in the summer, too but just the opposite. Remember, "insulate tight and ventilate right"

 

[Lumber-Jack]

A return vent directly over (or within 10 ft.) is against code.

Is that under the(broken link removed to http://publicecodes.cyberregs.com/icod/ibc/2012/index.htm) or(broken link removed to http://publicecodes.cyberregs.com/icod/irc/2009/index.htm)

 

[begreen]

I think it is under the mechanical code, but would have to verify.

 

[Lumber-Jack]

Apparently (broken link removed to http://www.inspectorsjournal.com/forum/topic.asp?TOPIC_ID=17521).

 

[begreen]

I don't recall that being stipulated, but it's been awhile since I read the full code. We went over this several years ago and the actual chapter and verse was posted.

Edit - found it:
R602.8 Fireblocking required. Fireblocking shall be provided
to cut off all concealed draft openings (both vertical and horizontal)
and to form an effective fire barrier between stories, and
between a top story and the roof space. Fireblocking shall be
provided inwood-frame construction in the following locations.
1. In concealed spaces of stud walls and partitions, including
furred spaces and parallel rows of studs or staggered
studs; as follows:
1.. Vertically at the ceiling and floor levels.
2. At all interconnections between concealed vertical and
horizontal spaces such as occur at soffits, drop ceilings
and cove ceilings.
3. In concealed spaces between stair stringers at the top and
bottom of the run. Enclosed spaces under stairs shall
comply with Section R311.2.2.
4. At openings around vents, pipes, ducts, cables and wires
at ceiling and floor level, with an approved material to
resist the free passage of flame and products of combustion.
5. For the fireblocking of chimneys and fireplaces, see Section
R1003.19.

2.3. Return-air inlets shall not be located
within 10 feet (3048 mm) of any appliance
firebox or draft hood in the same
room or space.
3. Rooms or spaces containing solid-fuel burning
appliances, provided that return-air inlets are
located not less than 10 feet (3048 mm) from
the firebox of such appliances.

 

[westkywood]

A return vent directly over (or within 10 ft.) is against code.

I called everyone I could think of before doing this. Codes enforcement, insurance etc. They all said they saw no problem

 

[begreen]

I'm not surprised. Some inspectors are weak on parts of code. Ask if IRC R602.8.2.3 and R602.8.3 apply in your county.

 

[Lumber-Jack]

I don't recall that being stipulated, but it's been awhile since I read the full code. We went over this several years ago and the actual chapter and verse was posted.

Edit - found it:

2.3. Return-air inlets shall not be located
within 10 feet (3048 mm) of any appliance
firebox or draft hood in the same
room or space.
3. Rooms or spaces containing solid-fuel burning
appliances, provided that return-air inlets are
located not less than 10 feet (3048 mm) from
the firebox of such appliances.

OK, I did some research and got it straightened out. The part you are quoting is just a portion of the Return Air code, and is taken out of context. It is not a rule in itself, but rather part of the exceptions to a rule #5.
I'll quote the whole section here and explain it. The red text is my explanation and not part of the code.

SECTION M1602 RETURN AIR

M1602.1 Return air.
Return air shall be taken from inside the dwelling. Dilution of return air with outdoor air shall be permitted.

M1602.2 Prohibited sources. This is the portion that list the 6 prohibited locations of return air sources, both indoor and outdoor. #3 has one exception, #4 has one exception, and #5 has three exception, but the second exception list three separate requirements.
Outdoor and return air for a forced-air heating or cooling system shall not be taken from the following locations:

1. Closer than 10 feet (3048 mm) to an appliance vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.
2. Where flammable vapors are present; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.
3. A room or space, the volume of which is less than 25 percent of the entire volume served by the system. Where connected by a permanent opening having an area sized in accordance with ACCA Manual D, adjoining rooms or spaces shall be considered as a single room or space for the purpose of determining the volume of the rooms or spaces.

Exception: The minimum volume requirement shall not apply where the amount of return air taken from a room or space is less than or equal to the amount of supply air delivered to the room or space.

4. A closet, bathroom, toilet room, kitchen, garage, boiler room, furnace room, unconditioned attic or other dwelling unit.

Exception: Dedicated forced-air systems serving only a garage shall not be prohibited from obtaining return air from the garage.

5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air. This line applies to return air vents being in the same room as solid fuel burning appliances, note it only applies to rooms where the space serves as the sole source of return air. The portion of the code that you quoted is cited below, and is the exception to this rule.
Exceptions: The following exceptions apply to # 5
1. The fuel-burning appliance is a direct-vent appliance or an appliance not requiring a vent in accordance with Section M1801.1 or Chapter 24.
2. The room or space complies with the following requirements:
2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning appliances therein.
2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.
2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of a draft hood in the same room or space or the combustion chamber of any atmospheric-burner appliance in the same room or space.
3. Rooms or spaces containing solid-fuel burning appliances, if return-air inlets are located not less than 10 feet (3048 mm) from the firebox of those appliances.
6. An unconditioned crawl space by means of direct connection to the return side of a forced air system. Transfer openings in the crawl space enclosure shall not be prohibited.

So what you quoted is not a rule or code, but rather and exception to rule #5.
So to sum up what they are saying is You are prohibited from having a return air vent, that is the sole source of return air, in the same room as a solid fuel appliance. Except if the said return air vent is located 10 feet away from the firebox of the appliance.
In cases where the return air vent is located in the same room as a solid fuel burning appliance, and the return air vent is not the sole source of return air, there are no prohibitions, and thus no exceptions are necessary.

 

[Lumber-Jack]

I forgot to stress that if the return air vent is the sole air return source (no other return air vents in the house), then the portion of the code you quoted requiring the return vent to be at least 10 feet away from the wood stove does apply. Certainly nothing wrong with quoting the code, or a portion of the code, to people, but just be sure to include it in it's full context.

M1602.1 Return air.
Return air shall be taken from inside the dwelling. Dilution of return air with outdoor air shall be permitted.

M1602.2 Prohibited sources.
5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.
Exceptions
2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of a draft hood in the same room or space or the combustion chamber of any atmospheric-burner appliance in the same room or space.
3. Rooms or spaces containing solid-fuel burning appliances, if return-air inlets are located not less than 10 feet (3048 mm) from the firebox of those appliances.

 

[begreen]

A single return in a room is the more common configuration.

 

[Lumber-Jack]

A single return in a room is the more common configuration.

5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.

This means the sole source or return air period, not the sole source in that room or space only.

Most larger house have multiple return air vents in a house simply because the of the size vent that would be needed to satisfy the system. My 1500 sq ft home has two return air vents, but the HVAC guy who installed the system admitted to me that a house my size should actually have at least one more, but because all the ducting was installed after the house was built it just wasn't feasible to run more than the two return vents.
Determining how many, or what size, the return air duct there should be is based on the volume of air being circulated. A forced warm air duct heating/cooling system should have a Return "area" that is at the LEAST equal to the Supply area. In other words, if the Main Supply duct is 8x20 (160 sq in ) then the Return size should be at least 160 sq in or even approx 10 % more.

That being said some very small homes can get away with one return air vent though, and if that solitary return air vent is in the room with a solid fuel device then they should observe those exceptions listed after #5, including the two portions that you often quote.

 

[hoverwheel]

My 130 year old balloon framed home has 130 year old registers in six... No... Seven rooms. I do plan to eventually install fire dampers in them though.

 

[Minnesota Marty]

lumber-jack,
Nice explanation in simple terms. Thanks for the clarifications.

 

[begreen]

First, CL, thanks for spending the time on this. Building code is complex. The code quoted is mechanical code correct? That is not the same as residential code though they overlap, correct? There a multiple concerns code tries to address. Fume and fire spreading are one section. Another code concern is depressurization. For example I read that there is 6.2.3.20? Return Air System Subsection (2) Return Air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a fuel-fired appliance.

In spirit the safer approach it seems is to not have a return in the same room as as stove if the room can be closed off by doors and this is the only return. If the room is open the return still should be kept away from the stove to reduce the chance of flame, smoke, CO spreading through the hvac system.

 

[Lumber-Jack]

First, CL, thanks for spending the time on this. Building code is complex. The code quoted is mechanical code correct? That is not the same as residential code though they overlap, correct? The code is taken from the(broken link removed to http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_16_sec002.htm)
There a multiple concerns code tries to address. Fume and fire spreading are one section. Another code concern is depressurization. For example I read that there is 6.2.3.20? Return Air System Subsection (2) Return Air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a fuel-fired appliance.
In spirit the safer approach it seems is to not have a return in the same room as as stove if the room can be closed off by doors and this is the only return. If the room is open the return still should be kept away from the stove to reduce the chance of flame, smoke, CO spreading through the hvac system.

There will always be a chance of safety issues with any in home heating device, whether it be electric, gas, oil, or wood. In fact, just this morning a friend related to me that he had the gas furnace serviced in a house that they had bought and have been renovating. The heating guy did a carbon monoxide level test on the room heating vents and detected levels of 70 ppm and rising before they finally shut the furnace down. Fortunately they haven't been living in the house, but they have been working in there.
As a side note in regard to this. I have heard of this a few time before with gas and oil furnaces. What usually happens is the metal wall between the flames and the venting system in the heaters develops a small leak and the exhaust from the combustion chamber leaches into the venting system in the house. I sometimes wonder how many people who are afraid of using their wood stoves while they sleep or go away from their home, and feel safer turning on their furnaces, ever think about the possibility that their furnaces might also have some hidden problem they should be more worried about.
.
With regard to the depressurization, a well designed HVAC venting (ducting) system should be balanced with a output vent into the same room as a return air vent so that there is no imbalance in pressurization in the room. Equal amount of air flowing in as is being sucked out. Hopefully there aren't too many people foolish enough to install and use wood stove in a small room with a tight sealing door, no OAK, and a return air vent sucking the air out of the room. That would be a perfect disaster scenario no mater how far away the return air vent was from the stove.
As for the spreading of CO inside a home, HVAC venting systems are not the only way CO can spread through a house. People in the forum often talk about the best way to circulate heat from a wood stove around the house, and one of the most often recommend ways is to use fans on the floor to blow cold air from the cooler rooms in the direction of the wood stove to help the warm air recirculate back into those rooms. It is often said this works better then using your HVAC blower to circulate air around the house. If this is true and you did happen to have CO leaking from your stove for some reason, then this use of floor fans to circulate the air around the house could also become a very efficient and effective way of spreading that CO throughout the house as well (better even then using your HVAC blower and ducting, some say). Point being, there is no system that is perfectly safe.
Personally I think the best thing you can do, and the best thing you can recommend to people, if you or they are concerned with these kinds of safety issues, is to equip your home with as many smoke alarms, CO monitors, and CO2 monitors as you can afford. And this applies to people who don't own wood stoves too.

 

[begreen]

Exactly right and that is my concern. We constantly hear of folks unbalancing their system by closing off supplies and returns, often not knowing the difference. This is a case where a little knowledge can be a deadly thing. I choose to err on the side of caution when folks talk about installing a return right over the stove, especially if it is a dedicated ventilation system and this is the sole return.

 

[Lumber-Jack]

Exactly right and that is my concern. We constantly hear of folks unbalancing their system by closing off supplies and returns, often not knowing the difference. This is a case where a little knowledge can be a deadly thing. I choose to err on the side of caution when folks talk about installing a return right over the stove, especially if it is a dedicated ventilation system and this is the sole return.

I guess that is where we differ, I believe the more knowledge you have the better equipped you are to safeguard yourself against the dangers inherent in wood heating. A little knowledge is good, a lot is better.
The thing that generally separates wood stoves from other home heating devices is they require a much more hands on approach then other heating devices, often requiring the user to have a much better understanding of not only how to operate and maintain the device, but the type and quality of the fuel that goes in it. There is no denying that wood heating is not for everyone. The safest approach for some who might need to "err on the side of caution", and might be apt to get themselves into trouble with too little knowledge, may very well be to not to bother heating with wood at all. I think a lot of homes and families would have (and could) be saved if some people took this realistic approach.
On the other hand there are people out there who are willing, able and ready to understand the dynamics involved of wood heating, and fully realize that there is more to it then flipping a switch or calling the heating guy once a year to service the furnace. People who are eager to learn all they can about the fuel, the operation, and about all the dynamics of getting the most heat and efficiency out of their wood stoves. Perhaps that is where a forum like this has it's benefits. Before you can learn a lot though, you have to start by learning a little. I know that's maybe not exactly how you meant to apply the statement I underlined in your quote, but if you look at it with a broader view it makes sense . I know of many who people have incorporated return air vents into their wood heating systems to help circulate heat from their wood stoves, not one of them has died yet, so for sure it can be done safely, but yes, it is not with out any risks, and you should understand what those risks might be.

BTW, how do you feel about the possible risk of spreading CO2 or CO from a leaky stove around the house by using floor fans to circulate the air? Is that a risk you are willing to take or recommend?

 

[begreen]

I said a little knowledge. A lot of knowledge is the opposite.

Why would anyone have a wood stove and not have good working smoke alarms and CO detectors?