combustion air

Jim Davis_3

Bringing air into the return should only be the equivaent of .5 air change an hour which I think the ASHRAE standard is .4 an hour. Exfiltration is much better than infiltration, should create more comfort, indoor air quality, safety and should have minimal affect on fuel usage if any. Not sure why it would increase your fuel 30%?? Unless it was way too much!!

ryan_7

combustion air, new construction

I was just wondering how everyone brings in combustion and fresh air into a new home? For our warm air homes, we bring outside air into the return duct and also air for combustion into the furnace room for the water heater.
What are you guys doing for a hydronic heated home, for fresh air?

[Deleted User]

Easy...

we use sealed combustion appliances and don't have to mess with it:-)

Our Code requires 1 square in per 4000 btuh input for combustion air, AND ventilation air on atmospherically vented appliances.

Make up air requirements vary by jurisdiction and locale.

I never quite understood that part of the code that allows you tiners to introduce the make up air into the return. Doesn't that cause mechanically induced exfiltration?

I know I had that on my home with the original FAF, and when I replaced it with hydronics, I dropped my gas consumption by 30%...


ME

Rely_2

Venmar

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ryan_7

we do that too, but

I have had inspectors want fresh air brought in mechanicaly, just wondering what others do when faced with the same challange.
Generally we install central air too, so be bring in our air to that unit, but not every job gets air.

Weezbo

keep them seperate.

i would not consider bringing make up air into the envelope through the HRV. thanks anyway...appreciate the thought and all... basically the hrv should be a seperate Sealed unit with sealed seams and fittings and while it may be In the mechanical room/s zero exchange with that room through it would be the only acceptable means of installation.

try Venmar.. Lifebreath..for controlled ventilation requirements. excellent information may be found at HealthyHeating.com

Dirk Wright

Field Controls MAS

I installed a field controls MAS in my forced air system and the air in the house is so much nicer! I have not noticed that the system runs any longer than normal, but obviously I'm paying a little bit more to heat the fresh air coming in.

jeff_51

we are required to bring in a fresh air duct the same size

as the flue, with a min of five inches, unless everthing is closed combustion. We usually run a fresh air hood, run fle into the mechanical room and then trap it, so you only pull out air during a negative pressure situation. Alot of contractors leave the flex about a foot off the floor and put a five gal bucket under it which also causes a trap which prevents cold air from spilling all over the floor. Cheap and easy and usually done in older homes that are not that tight. In new class one homes, it of course has to be mechanical. We are not allowed units like the little scuttle, and anytime we see it in the return, we usually change it out.

Bob W._3

Jeff, I had just started a similar thread with my question about using an 8" flex duct down to an open barrel for combustion air in the boiler room (my boiler will be replaced soon, and will go from a 10" flue to an 8" flue). This is what was suggested to me by the gas company. Apparently our Minnesota state codes are not as specific about this, at least in older homes?

[Deleted User]

It was...

built in 1953, had an unobstructed 8" vent coing into the RA duct, and it was WAY too much. Probably not typical by todays standards, but nonetheless, it was there.

Makes me wonder how many other tract homes (THOUSANDS) in my neighborhood have the same scenario.

ME