Hot/Cold air vents/returns

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OK, no code requirement for residential use. I will be circumspect in my recommendations then.

The joint glue is out of my purvue, but a quick look shows that engineered joist adhesive fails (depending on the adhesive) between 177 and 232 degrees - centigrade - or 350 and 450 degrees farenheit. Is that correct? If so, the fusible link will trigger long before this.
 
Elk -

I won't take issue with the idea that a penetration through the floor should be framed and sides blocked w/drywall to seal up the floor cavity - certainly there are always better ways to do things like this. But as BeGreen points out, you have not produced any code that says this can't be done - just opinions.

I completely repsect your opinion until you cross the line of offering it up as authoritative fact based on codes. It is a worthwhile discussion and ultimately a very personal judgment call. Much like the choice of putting a woodstove in a home when in fact a propane furnace would be far safer. There are 50 people on other forums calling us morons for doing so :)

-Colin
 
I'm still working with the NFPA and the International code committee, trying to have HVAC systems tied into the smoke alarm systems in homes.

In commercial codes this is accomplished one or two ways, with fire dampers or system wide shutdown. In smaller commercial projects, basically the same furnaces are used as residential construction, but pre wired to adapt to the alarm system. This is the cheapest economical way ,really should add less than $100 to a new home.
esidential construction floor walls and ceiling cavities can be used for return. A practice not allowed in commercial construction. They must be hard piped.

Believe me this is not the best way for return routes. Another cost cutting measure that lacks engineered design flows Plus the nature of the installation is they all leak.

There is enough language to require leak or duct sealing balancing and leak testing. This is one area that can improve efficiency plus safety.

This is another did you know:
Houses built with engineered joist present a real danger to fire fighters. It is up to the fire command as to whether he determines fireman can enter a home. The key component of engineered joist is the adhesives. Once they are exposed to heat, some where around 170 degrees centigrade, the common cheap versions, the structural integrity of that floor is compromised. IT is unsafe for them to enter the home. Another factor that 1/2" composite ribbing burns threw 2/3 fasted than common 2/2 construction grade joist . A final note engineered joist spacing between members is usually wider 20" or 24 " on centers ,meaning the are fewer members and it only takes a few to be compromised ,to present an unsafe condition .

My point, is to point out there are risk to be factored,, before one starts cutting holes in floors and ceilings. More so in homes using engineered lumber.
 
Just wanted to chime in that the design I presented was successful. Installed over the weekend and now the upstairs is within 5 degrees of the basement, sometimes less, at one point last night it was 70 upstairs 72 down. Temperatures were in the upper 20's most nights and only climbed into the upper 30's all weekend.

Enord's comment about getting the cold air back to the stove was what I kept in mind the most. Once I started getting the cold air back to the basement, via the coldest and furthest points in the home, it was an amazing difference.

Elk, I appreciate your concern and I think people need to be aware of the possible risks associated with this setup. However, I must say I've lived in several houses with these installed, one built in the 1880's on in the 1980's, and I've yet to get any grief from inspectors. If a fire were to start in my basement, the huge wooden/open stairway to the first floor would be the downfall and not these small holes in the floor.

Locating a stove in the basement does have it's advantages. If you only have one flue and you have living space on both floors it definately provides a cost savings over having to install heat sources on both levels.
 
Glad to hear you accomplished what you wanted. Did you end up using a passive vent or one with an inline fan? Either way, I am curious how the addition of either of these influences your existing supplies and returns in those bedrooms? If they are passive vents, will your return air vents in/outside the bedrooms draw warm air from your basement when your furnace kicks on? And if the vents have an inline fan, will the warm air from your furnace supply vents be drawn down into the basement?



emory said:
Just wanted to chime in that the design I presented was successful. Installed over the weekend and now the upstairs is within 5 degrees of the basement, sometimes less, at one point last night it was 70 upstairs 72 down. Temperatures were in the upper 20's most nights and only climbed into the upper 30's all weekend.

Enord's comment about getting the cold air back to the stove was what I kept in mind the most. Once I started getting the cold air back to the basement, via the coldest and furthest points in the home, it was an amazing difference.

Elk, I appreciate your concern and I think people need to be aware of the possible risks associated with this setup. However, I must say I've lived in several houses with these installed, one built in the 1880's on in the 1980's, and I've yet to get any grief from inspectors. If a fire were to start in my basement, the huge wooden/open stairway to the first floor would be the downfall and not these small holes in the floor.

Locating a stove in the basement does have it's advantages. If you only have one flue and you have living space on both floors it definately provides a cost savings over having to install heat sources on both levels.
 
rmcfall said:
Glad to hear you accomplished what you wanted. Did you end up using a passive vent or one with an inline fan? Either way, I am curious how the addition of either of these influences your existing supplies and returns in those bedrooms? If they are passive vents, will your return air vents in/outside the bedrooms draw warm air from your basement when your furnace kicks on? And if the vents have an inline fan, will the warm air from your furnace supply vents be drawn down into the basement?

I ended up using passive vents, no fans. However, I did experiment with blowing the cold air from rooms without vents towards the vents and that also helped to warm those rooms. Just used a regular box fan, so again, nothing inline. When I first open a cold room, if I do blow air down through the vents it does speed up the heating process of those rooms. The main thing for me is that this system works without electricity.

In the bedrooms, the vents let the cold air sink and suck the warm air from the opposite end of the house, which in turn then pushes the hot air out of the basement.

The major source of hot air is definitely from the the open staircase, however during the daytime when the front of the house (and top of the stairs) are heated by the sun, this convection stops and most of the air comes up via the kitchen vent.

So I guess to summarize, the system works great without fans, however fans speed up the process when opening up cold rooms.

Hope this helps, let me know if you have any other questions.
 
Thanks for the response. Have you had your furnace running while you have your woodstove burning? If so, does this change how the system works?
 
rmcfall said:
Thanks for the response. Have you had your furnace running while you have your woodstove burning? If so, does this change how the system works?
No, I haven't. I'm really not sure how that would impact the convection.
 
Elk, I appreciate your concern and I think people need to be aware of the possible risks associated with this setup. However, I must say I’ve lived in several houses with these installed, one built in the 1880’s on in the 1980’s, and I’ve yet to get any grief from inspectors. If a fire were to start in my basement, the huge wooden/open stairway to the first floor would be the downfall and not these small holes in the floor.

In certain setups the efficiency of air circulation can be enhanced by correctly sized and placed vents. However, Elk is correct that the same vents will feed a fire much needed oxygen in the event of a basement fire. Think of it this way, in the event of a basement fire, the vents are the air control on the basement stove and the staircase is the flue. In that circumstance, not having the vents may buy one a precious minute or two to escape the house.

The fact is, sh*t happens. This is a case for installing fusible links in the vents, smoke alarms in the bedrooms (not just the hallways) and a good exit plan from second story windows. Hopefully you will never have to use a single one of these options, they are an insurance policy. But if you do, you will be thanking yourself for taking extra precautions.
 
BeGreen said:
In certain setups the efficiency of air circulation can be enhanced by correctly sized and placed vents. However, Elk is correct that the same vents will feed a fire much needed oxygen in the event of a basement fire. Think of it this way, in the event of a basement fire, the vents are the air control on the basement stove and the staircase is the flue. In that circumstance, not having the vents may buy one a precious minute or two to escape the house.
What about the fact that most of us have a secondary heating system, oil/gas/etc, in the basement along with our stoves. When I'm using my wood stove that unit is turned off, if there was a fire wouldn't the outside air from that flue be much more of an accelerant ? Even if you didn't have holes in the floor, it would be able to pull in much more air to feed the fire, just like people hook up outdoor air supplies to there stoves to increase draft?
 
Here is another code not considered the cellar door leading to an " unconditioned space" must be either solid filled or a metal insulated door fully weather stripped.

that is found in part of the energy codes. Reason being to prevent heat loss to an unconditioned space. To answer about stairways leading from an unconditioned cellar to an conditioned floor
yes than that stair way is required a door and it is now not an air passage way between floors. Each side of that doorway has to be protected with smoke detectors

Now if the basement is finished and the stairway is within the conditioned space a door is not required.

What provisions have you taken tio satisfy these code provisions

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.

\
 
emory said:
BeGreen said:
In certain setups the efficiency of air circulation can be enhanced by correctly sized and placed vents. However, Elk is correct that the same vents will feed a fire much needed oxygen in the event of a basement fire. Think of it this way, in the event of a basement fire, the vents are the air control on the basement stove and the staircase is the flue. In that circumstance, not having the vents may buy one a precious minute or two to escape the house.
What about the fact that most of us have a secondary heating system, oil/gas/etc, in the basement along with our stoves. When I'm using my wood stove that unit is turned off, if there was a fire wouldn't the outside air from that flue be much more of an accelerant ? Even if you didn't have holes in the floor, it would be able to pull in much more air to feed the fire, just like people hook up outdoor air supplies to there stoves to increase draft?

Good question. Depending on the unit, it might contribute, though not with nearly the same volume. And not at all will high efficiency units, that is until the pvc piping melted. Add it up. 6" round flue = ~28 sq in. versus four 6 x 12 vents = 288 sq in.
 
Well the air pulled though the chimney ends up into a sealed combustion chamber there is some leakage but I really believe not enough to fuel a fire

the whole premise to fighting a fire is containment even the wild fires are attacked that way Containment can allow fire fighter to bring a blaze under controll much easier
it limits the amount and damage less insurance to pay out, buys valuable seconds / minutes ,for safe exit.

you know there is a living space sharing garage walls are required 1 hour protection any door from the living space has to be at least a B labeled fire door.

all these requirements are to provide a level of containment. all fire stopping draft prevention are efforts to provide containment.

you can"t have unprotected holes in your floors and ceilings with out reducing natural containment.. I know stairways defeat containment.

This has been constantly studied, commercial construction has fire suppression systems to cover stairways and exit ways.

On the residential side codes are not nearly as stringent one there is a limited occupant load Out of the studies it was proven that occupants are safer at night when bedroom doors are closed

They determined that bedrooms required more protection Thus the requirement of smoke alarms with in them. Even as I type there are petitions to require dual photo electric an ion smoke detectors. We may not be able to protect the stariways but earlier broader warning systems buys valuable time. If the fire marshals had their way we would have sprinkler systems.

Guess what I have one sprinkler head over my boiler and a heat detector. BTW not a bad idea infact the more you think about it it makes sense
 
Technically, if we want to follow what commercial construction teaches, we should have fire doors throughout our house all on hydraulic self-closing cylinders.

Point is, there are already HUGE pathways to distribute smoke and drafts within a house, and we're not about to "fix" the major problem, so people shouldn't live in fear of adding a distribution duct.

Similar example - suppose you drive a car but you don't wear a seatbelt. Then you decide to not get tire pressure monitors - one could argue you're now less safe. But it's a nit compared to all the risk you're taking without that seatbelt. Same idea here - open construction in homes is already so radically different that commercial learning just doesn't apply until you start self-closing and sealing up each different part of the home, and if you're not going to do that, everything else isn't all that relevant.

In engineering, the concept is often illustrated with a "pareto" chart.

-Colin
 
good point up till 2000 all garage doors entering the living space had to be self closing. A closer or spring mounted hinges.

For some reason that was amended and no longer a requirement

the latest building codes require R19 outer walls. the other major changes have a lot to do with changing wind zones more stringent construction in wind exposures including impact resistant
glass


So what NY soapstone is advising ignore codes you do not want to adhere to because you have an open stair way. Or he is telling you fire blocking and draft stopping is insignificant and that containment is of little concern He thinks stairways justify not following the fire blocking code You asked me to provide code concerning cutting of holes when I do you did not like what is said so your efforts are now focused to discredit the code by doing so you are recognizing what is written.

I have enough code justification to not allow this practice in my jurisdiction. Since it is taken from the international codes every town/city state is governed by the same code body the International codes. The language you ask me to provide is there for all to read.

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.
 
What is the line number for that code? Key word seems to be - around. By my reading, if a metal sleeved floor vent is surrounded by sheet rock and tightly sealed on edges, it passes that code. Is that correct?
 
As Elk posted:

"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.
"

Am I missing something or is this totally irrelevant to the discussion about cutting holes in the ceiling / floor in an exposed area? The way I read this quote is that vertical and horizontal penetrations must be fire blocked if they are concealed, not if they are in the open. I also think BG's point about the metal frame of the vent and proper blocking around it is a good one. Of course a fuseable link also adds to the safety.

It is a bit confusing, hopefully someone can shed more light on this.
 
BeGreen said:
What is the line number for that code? Key word seems to be - around. By my reading, if a metal sleeved floor vent is surrounded by sheet rock and tightly sealed on edges, it passes that code. Is that correct?

Absolutely - and I do not disagree at all on that point. In fact, I think that's how most folks would build it anyway - it would be framed in and finished because it would likely be quite visible through a floor grate.

So no, Elk, I'm not telling anyone to disregard code - I'm telling them they are free to disregard your opinions on this matter that are not backed by codes. There is no way you'd defend this if someone challenged you in your township either.

I'm also taking the time to explain why there is nothing in residential code saying no between-room ducts - because many aspects of containment don't apply to residential construction. If you want to improve, it is completely pointless to start by disallowing ducts - that buys you nothing when you have wide open doors and stairs. You'd be better off by first mandating self-closing firedoors throughout the house. After that is all complete, then you can start to worry about ducts, which is exactly the direction commercial building code seems to have gone.

I do think this thread is valuable and should be distilled into the wiki - it makes it quite clear that residential building code does not prohibit between-room ducting. There has been way too much opinion presented as code on this matter throughout these forums.

-Colin
 
good points I think it really applies to vents cut into floors connected to a sealed duct system that they are required to be fire blocked and isolated

but again all vents have to be protected such that they will not allow transmission of combustion elements. Now if the holes cut in the floor which are vents are adequately protercted to eliminate combustion properties then they would satisfy code If fire blocked correctly and fusible links grills are installed is that enough protection does that satisfy prevention of all combustion elements like carbon monoxide. How mush smoke will pass before heat melts the link? Would carbon monoxide detectors provide additional coverage / more smoke detector locations?

My original intent was to inform people that plan to cut holes there are other factors, safety factors, to be considered and addressed

I'm the messenger One asking as many questions as the next poster. The only real clear cut answer is natural containment has been compromised I do know laundry shutes were removed from residential construction, due to rapid advancement of verticle fire spreading, Holes in natural containment, will allow rapid verticle expansion of fires and reduce containment
 
elkimmeg said:
good points I think it really applies to vents cut into floors connected to a sealed duct system that they are required to be fire blocked and isolated

but again all vents have to be protected such that they will not allow transmission of combustion elements. Now if the holes cut in the floor which are vents are adequately protercted to eliminate combustion properties then they would satisfy code If fire blocked correctly and fusible links grills are installed is that enough protection does that satisfy prevention of all combustion elements like carbon monoxide. How mush smoke will pass before heat melts the link? Would carbon monoxide detectors provide additional coverage / more smoke detector locations?

My original intent was to inform people that plan to cut holes there are other factors, safety factors, to be considered and addressed

I'm the messenger One asking as many questions as the next poster. The only real clear cut answer is natural containment has been compromised I do know laundry shutes were removed from residential construction, due to rapid advancement of verticle fire spreading, Holes in natural containment, will allow rapid verticle expansion of fires and reduce containment

Elk, I completely agree with your points and how you've presented them here - you're saying to be aware of the risks, and code requires that you seal around that duct if you do it.

-Colin
 
Got to agree with Mr Griz on this one... if this is the only code regarding penetrations. Onyl those in concealed spaces are required to be sealed. Wall cavaties or stair wells that can help fire to reach other spaces unseen. Floor penertations with dampers would pass inspection here.

Garett
 
There is a bit more to engineering these vents than just curring holes a little knowledge in air circulations must be planned in advance. ramdom holes poorly planned are useless supply with out return is useless. knowing what a vent will actual transfer comes into play knowing that standard metal grills reduce flow area 25% helps sizing them wooden grates can cut air flow up to 50 % or more. knowing the cfm capability per hole size per grill arrangement takes some real planning the I think it will work approach will be a futile attempt of bad planning without know if the task will be accomplished the only sure thing will be you just reduced you safety factors mechanicall removing combustion air from the stove location is a formular for disaster factoring how to reverse positive pressure gravating towards the holes and trying to overcome it with heat rising has to be considered
 
NY Soapstone said:
Elk, I completely agree with your points and how you've presented them here - you're saying to be aware of the risks, and code requires that you seal around that duct if you do it.

Amen. A lot of the code is quite applicable when there are multiple dwelling units in one building. Then code makes sense to provide the best fireblocking between units, even if serviced from a common basement. I agree with the spirit and letter of these codes. But in a single dwelling unit, there is a whole lot more grey area. In this circumstance, common sense and homeowner safety should prevail.

Face it, if total safety was the ultimate goal, eliminating wood burning would be on the short list. Once wood burning is involved there is a very large human factor introduced. That's why we're here, helping others. Burning wood requires knowledge and a cautious respect for the limits of system because the homeowner becomes the safety systems that are normally built into other heating appliances (limit switches, combustion detectors, etc.).
 
Gosh, these threads always seem to digress away from the initial question "What do you think about this layout?" or "Where should I put my registers".

I've answered my own question by just going ahead with it but if anyone is reading this via a search, my advise is put the cold air returns in the coldest rooms as far away from the stove as possible. Don't just put a warm air vent above the stove. Don't try to blow warm air to the upper floors, instead it is much easier to get the cold air to the stove.

Finally, be aware of the risks from both CO and fire but also keep in mind that people have been doing this to their homes for hundreds of years.
 
emory -

glad to hear you were sucessful with getting the heat up stairs

one question - how did you determine the size of the return ducts
 
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