Question on Fresh air ducting

I have a quick question on whether the fresh air ducting for a water heater is done correctly so I am asking all the great minds out there!

The house is a 5 year old ranch style home with no basement and the furnace is in the attic but the hot water heater is in a closet off the garage. The fresh air vent for the water heater room feeds up through the ceiling into the attic and terminates a couple of feet above the insulation and about even with the top of the furnace. The attic ventilaiton is adaquate there are several roof and soffit vents. My question is whether it iwould be appropriate to terminate the vents inside the attic?

Yes terminate the vent to exterior.

Raymond Wand
Alton, ON

Thanks, I agree it should go to the exterior. I have another issue for the furnace so I just wrote it up to have the HVAC tech evaluate the venting and let him make the call!

It is perfectly acceptable to terminate the combustion air ducts in the attic, I think the rule is 12" above the insulation and no screen on it though.

Would that only apply when the furnace is in the attic or could that apply any time the fresh air is vented?

I have always seen exterior venting but it makes sense if the furnace is vented through the normal roof and soffit vents that it would expell the gases from the water heater as well but I have never seen this before.

Robert, we may mixing metaphors here. Let’s make sure we are calling the various ducts and vents the same thing. I say it is permissible to provide dilution air and combustion air to a gas appliance (furnace, water heater) from the attic as described above. The exhaust gases must, of course, be vented to the exterior of the home, i.e. roof jack or other similar method. The attached sketch is not the one I’m looking for but should suffice for now.

Clarification: We are talking about the dilution air only and not the exhaust or intakes for the furnace or water heater. That would make a big differance…

OK, I had to reduce the photo to get it small enough to load. Check my prior msg attachment.

I have attached a crude drawing that should make it clearer. The question is with the vents indicated by the arrows. These are vent tubes that supply the fresh air to the room itself. The tubes are as shown a straight open pipe from the hot water room to the attic.

fresh air vent example.jpg

fresh air vent example.jpg

I think it is ok with that setup. The Code Check drawings as well as the IRC drawings M1703.2(3) are really close to what you are showing in your drawing.

Basically, the size of the size of the fresh air ducts will determine if you need two vents. Another way to say that is you may only need one if it is large enough. That doesn’t appear to be the case in your situation so they used two smaller ones.

Being that two are used and pulling the air from the attic, one must be low i.e. within 12" of the floor and one high i.e. within 12" of the ceiling.

Andrew thanks for the information. I always figure when in doubt it is better to ask… Great information everyone thanks.