on the outside is a cold air register cover, on the inside this line extends from the duct line of the furnace
Im thinking that this was to bring fresh air into the home?
this line extends to the exterior right above a dryer vent
The dryer vent is to close to the supposed fresh air vent, as fresh air vents in our area usually have a different cover when outside, not an interior cold air return register cover, which is pictured and was under an over hang on a house resently inspected.
according to the N.B.C. outside air is supposed to be brought in to the main pleum, and not to a distribution duct, as done in the picture.
Repair what? It appears that it was determined by someone that the amount of fresh air entering the home was insufficient and fresh air has been introduced into the home through the efficient means of drawing it through the return duct to heat/cool it prior to distributing it.
The dryer vent is to close to the supposed fresh air vent.
The fresh air vent should be below the dryer vent and 6 feet away.
There are rules as to proper locations, size and installation.
That being said first thing is to check the distance for exhaust of the dryer.
6 feet apart is considered OK by F326, but I recommend if possible to not be on the same wall.
Every IAQ inspection that had crossover happening was always on the same wall and affected the health of individuals.
Is that fresh air intake connected to a return duct (e.g. drawing air in from the furnace blower), and what is the clearance between the intake and the dryer exhaust?
It looks as if it is, and I believe that is Eragorn’s concern. It it allowed to be a direct connection? Also, is it allowed in Canada, where Eragorn is operating?
Looks like a pretty small duct for a typical residential return, unless there are multiple returns, which is why I asked. If it’s drawing in air from a furnace blower it’s more of a concern.
According to what you have stated this will not provide the added ventilation to all rooms. It needs to be changed to a proper hood and designed supply by a Certified Installer and designer of residential ventilation following the F326 not the NBC.
Eragron, Your original post states in the last line that it is a distribution duct not a return duct is this correct, if so they would be pushing conditioned air outdoors, the 1st picture appears to have a boot on it like a floor register might have is this correct. I will have to talk with an HVAC guy I know, I am at a loss with the need to introduce fresh air directly into the duct system, would not fresh air be provided to increase the requirements for the combustion appliances, if your are introducing fresh air directly into a system this (my thinking) changes the performance of the system as designed, it has been a ruff day maybe I am just not getting the picture correctly, thanks.
As you have amended your original post to say that this connection is to a supply duct, it is definitely wrong for that reason … no matter where the dryer vent is located.
Canada has requirements for mechanical ventilation of houses, which means that outside air needs to be brought into the house. If there is a ducted heating system the outside air (make-up air) is typically mixed with return air to provide the ventilation. However that can also pressurize a house leading to interstitial condensation problems. So there needs to be provisions for exhausting some indoor air also.
It’s possible that to relieve some interior pressure, they connected a small exhaust duct running to the exterior off of a heating supply trunk. Which is why I asked if that was connected to a return duct. If it’s a relief duct there would be no clearance issues with the dryer exhaust.
Is that a return duct that is tapped to bring in outdoor air? Or is air brought in somewhere else, and that is a relief duct?
P.S. If the prescriptive requirements of the Canadian NBC for mechanical ventilation are followed, then a site specific design following the more technical CSA F326 performance standard is not required.
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needs to be connected to the return duct and needs a motorized damper that opens when the furnace fan turns on this lQQks to be a home made make shift duty cycler
If they did, that is about the dumbest thing I have ever heard.
It’s possible that to revieve some interior pressure, they connected a small exhaust duct running to the exterior off of a heating supply trunk. Which is why I asked if that was connected to a return duct. If it’s a relief duct there would be no clearance issues with the dryer exhaust.
I got a good idea! Lets heat the patio with some of the supply air from the furnace. That should cost very little since it is only a small 6 inch duct blowing at 100 cfm.:shock:
I would love to see there heating bills in MooseJaw.
For whole house ventilation, you are generally trading off indoor air quality for energy efficiency. Under a prescriptive design a whole house ventilator near the roof would have to come on whenever the furnace blower comes on (yes, you would be blowing heated/cooled air outside), or pressure relief has to be designed into the system. You would be loosing energy either way, but are improving indoor air quality.
The US has not yet mandated whole house ventilation like Canada because of concerns over energy losses with these systems. However with how tight construction requirements have become for better energy efficiency, indoor air quality and the health of occupants has become a real concern. And building ventilation is required for all commercial construction. I think it’s only a matter of time before the US institutes similar requirements for houses.
One option for house ventilation that I usually recommend clients consider for higher end construction locally is to use a heat recovery ventilator (aka Energy Recovery Ventilator, or ERV). It transfers much of the heat between the intake and exhaust for better energy efficiency, but they are more expensive to install.
