New codes are going to address using HVAC systems to circulate solid fuel burning appliances

[elkimmeg]

Many posters here have expounded about using the returns to circulate heat from their wood stoves. If I get time tonight I will produce code language limiting or prohibiting this practice. There are real dangers present. Individuals have not factored or taken preventive measures to insure safety. The current heating ducts are never exposed to an open flame appliance or the possibility of exhaust gasses they produce heat in a sealed heat exchanged compartment. Doors are not constantly being opened in the compartment likewood-stoves . As much as we may want to believe wood stoves are not all that tight not compared to a sealed combustion chamber and sealed exchanger compartments. One of the first code aimed at this practice, is no flexible ducts can be used to extract or transmit heat from a solid fuel burning appliance. Floor joist pan bays cannot be used because all ducting has to be non combustible, the wood of the joist is combustible. To be safe a smoke-damper would have be installed within the system, also a monoxide sensor or alarm . The monoxide sensor or smoke detector operated damper, would either be activated and close down the system to eliminate further spread of smoke and monoxide.

I have ASked NSF to look into this. Expect more codes to address usage of systems not listed for this purpose or designing compliant safe systems.

 

[MountainStoveGuy]

Elk, i dont realy get it. Are you saying its not safe to turn your fan on your furnace and let is suck the heat from the room that the stove is in and distrubuite it? Sorry, i havent fininshed my coffe yet, i can be dense in the morning.

 

[elkimmeg]

That is correct. Can you produce specs that your system was designed for that purpose and has the built in safety precautions?
Another way of looking at it ( your brand new stoves excluded) say after a few year usage the gaskets seals are not quite as tight as they were. The re-factory joint's might have moved a bit with heat and expansion. That stove is not air tight never was . Now you are extracting air from the area of the stove operation, air that may be needed for combustion. How can you be sure you are not extracting exhaust? Say weather conditions are not favorable to draft, strong winds, warmer temps, that low fog dense heavy air. Is one willing to take the risk of drawing carbon monoxides into theirsleeping areas? Remember it is smokeless and odorless.

Me, I just as soon see it go up the chimney. For the same reason one can not modify a prefab in wood fireplace., What do you think using the HVAC system, to do a function it is not designed to do, and without proper safeguard's to protect it use.
. Should an incident occur, guess what you just put your self and family in graver danger, that transmission just increased the rapid spread of smoke to other areas. All efforts of draft stopping fire stopping have been negated. Why? Containment, buys time to safely exit.

 

[MountainStoveGuy]

Trying to understand this, so bear with me.
Your furnace fan kicks on and doesnt create negative pressure, so how can your stove be leaking carbon monixide when there is a normal draft established? THe furnace wont suck it out. And if your stove is all leaky then it just drafts that much harder taking the carbon monixide with it?

 

[Mike Wilson]

Elk,

Do me a favor... when you get some time, post a link or the exact text of the proposed code.

-- Mike

 

[begreen]

How does this differ from having a woodstove burning and the furnace comes on because it's -20 outside and the woodstove is not enough to keep the house warm? Is this change strictly pertaining to the direct ducting of a wood heating appliance?

 

[wahsega]

So does that mean no charming fire in the fireplace while the furnace is runnin? There is probably a section in Homeland Security just waiting to do some warrentless chimney sniffing:coolsmile:

 

[Marcus]

Based upon that idea, then one should also not use any regular fans/ceiling fans in the house to circulate any woodburning stove/insert heated air because it could spread smoke or carbon monoxide? Isn't that why we have lots of smoke and carbon monoxide detectors through the house???

 

[elkimmeg]

Much of the fire prevention of air transmission by duct work is addressed and in place on comercial levels.
Systems are designed to pressurize stairways and exit-ways. The pressurization suppresses the spread of fire or helps contain it.
Another system is, the use of smoke and fire dampers tied into the alarm-system that automatically closes the dampers to halt the air flow. The system itself may be alarmed to shut down by the alarm system.
First smoke detectors were required, then they were expanded to bedroom locations as well. Next are carbon monoxide detectors and not too far away sprinklers. We have entire subdivisions where sprinkler systems are required by the Fire dept, due to excessive distances to the nearest hydrant. Parts of our town is not covered by town water, the further reaches have wells. A domestic sprinkler system is designed, factoring the well's volume and gal per minute. Pressurized storage tanks, most 300 to 500 gallons, are installed to support the sprinkler demand, x minutes of time.

Codes already state that return air can not come from kitchens or bathrooms. Language also exist that returns can not be in
the same room of the fuel burning appliance. I do not know how one rationalizes code enforcement of returns, in a room with a fireplace. I can see the language pertaining to having a return in the boiler room

Ceiling returns are ineffective for heating. They return the warmest air and never draw the cooler heavier air, but better than no returns in an upstairs bedroom. Far superior to having just one hall return for the entire up stairs. Actually the worst placement of a furnace or exchanger, is the attic location, completely outside the insulation envelope. Energy Star Green Homes, has documented this claim. Yet codes do not address this. They do recognise the heat loss, by requiring proper sealing of the ducts and insulation requirements.

 

[Mike Wilson]

Elk,

Nothing I have read thus far restricts the use of using HVAC ducts to move warm air from a solid fueled appliance, so long as the HVAC ducting in question is not directly connected to said appliance. Or, in layman's terms, if the ducts don't touch the stove, you're fine. Using your home's primary HVAC ducts to move air is currently legal within the code. We had this debate 6 months ago, and that was the definitive resolution to this issue. If something has changed, please cite and quote it. I don't mean to be a pain in the a$$ again, but I think you are unnecessarily scaring the unknowing. If you can point to a line in a "proposed" code, then fine, but otherwise its just not true.

Thanks

Mike

 

[elkimmeg]

Perposed code is not not available at this time on a web site or in print the discussion really is focused towards actually making it safer to do just what is occuring. Moving air from a solid fuel heat sourse. Prevention of flow will be the code should a circumstance arise that it should be closed off.

Naturally you are allowed to move air that is what it is designed to do

Currently flexible ducts have a clas A fire rating but that is the outside material. The inner materal is polyehtlene and very combustiable.

Here is some code alread on the books taked from the Hearth Handbook for building Officials Solid Fuel Hearth Systems

Page 47

W3.9.3 Hot Air Duction

One has to go back to the furnace manufacturer specs to see if the furnace is listed for this purpose

* hot air cannot be drawn back into the furnace unless the manufacture list the furnace capable of doing so

* no use of insulated flexible ducting


Mike you are 100% on with using monoxide detectors. If employing moving air with your duct systems I would recomend installing monoxide detectors in your bedrooms after all sleeping is when we are most vunderable

I do not see all the drafts of code revisions espectally on the national level. This is the first time I have been contacted for imput,

I can tell you splinklers are being pushed for residencial use. Since 9-11, fire depts are leveraging there position and influencing codes concerning life safety issues. One issue being talked about is monoxide. Soon all garages attached to and adbutting living spaces will require monoxide detectors In April all home sales will require the installation of monoxide sensors to be inspected by the fire dept ( just like smoke detectors certificate of compliance is required now) so will monoxide sensor be required in MA.
Soon their locations will be expanded to include bedrooms just like smoke detectors and wired in to alarm with battery backup.

Expect more energy codes. In MA. we already adopted a higher r-value assigned to esposed ducts and hot water pipes, than on the national level. Ducts on the national lever require r-4.2 in Ma. r-5.0. Industry does not make a flexible duct r-5.0 but r-6.0
R-6.0 has been in use in MA since late 1998. Expect more emphasis given to preventing duct leakage, and less use of stud bay and floor joist returns bays.