# Fresh Air Intake for Furnace Room. Help Needed



## kenmac (Feb 26, 2009)

Fresh air intake on the furnace return is brought in to add fresh air to the home. It sounds like he wants to bring in fresh outside air for combustion of the wh. Some areas require this & some don't . The ones that don't require fresh outside air, require that the area which the appliance is installed has enough combustion / dilution air. Could be that canada requirs this.. There is a guy from canada on here. Maybe he can provide some info for your area when he checks in


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## samantha.77 (Oct 14, 2010)

Thanks kenmac, so the line that runs into my cold air return mixes fresh air with the furnace but the additional 4" dia duct to the Furnace Room is for combustion of the water heater ONLY since the Hi-Efficiency furnace is vented outside?? But my water heater is only 32400 BTU does it really need a 4" dia pipe how did he size that unless he is considering the furnace BTU's as well but I would probably think you would not use the BTU of the Furnace since it is a Hi-Efficiency. Am I right in my thinking, I just think this pipe is not necessary?


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## rayf01 (Jan 1, 2010)

Samantha,

I am in Edmonton Alberta so I undestand your pain. From talking with contractors I believe it is code to have a seperate pipe in to the furnace room with a pot on the bottom. This lets fresh combustion air in to the furnace room. My friend has a High Efficiency furnace in his place and his conctractor said the same thing, it is still required by code even though the furnace is outfitted with a direct outside line for combustion air. With how cold it gets outside I would say it has something to do with the draft in the chimeny for the water heater, you wouldn't want back draft in to your house.

I was concerned as well with the cold air coming in, I watched it last winter and it does let in cold air however it isnt overly noticable. If you are really concerned, Hoyme manufacturers electric dampers for both the fresh air in take to a combustion pot as well as to your cold air return. These are apparantly certified to meet code. They open up when the furnace comes on and close when it is off, preventing a lot of that cold air from entering the home.


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## kenmac (Feb 26, 2009)

samantha.77 said:


> Thanks kenmac, so the line that runs into my cold air return mixes fresh air with the furnace but the additional 4" dia duct to the Furnace Room is for combustion of the water heater ONLY since the Hi-Efficiency furnace is vented outside?? But my water heater is only 32400 BTU does it really need a 4" dia pipe how did he size that unless he is considering the furnace BTU's as well but I would probably think you would not use the BTU of the Furnace since it is a Hi-Efficiency. Am I right in my thinking, I just think this pipe is not necessary?


 
The outside line to the return air is only to bring / circulate fresh air into the home. It has nothing to do with combustion
If your furnace uses a 2 ( PVC) pipe system . 1 is for exhaust & 1 is for combustion air. If that's the case , outside air may be needed for water heater .. It all depends on what's required in your area


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## yuri (Nov 29, 2008)

Where do you live Samantha and how old is your house. The Hoyme damper will not work with a gas water heater as it needs to be interlocked to the gas valve electrically with a furnace. Impossible with a water heater.

Your contractor is talking about a combustion air supply pipe which you may or may not need depending on age of house etc.


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## biggles (Jan 1, 2008)

if the HWH is a regular burner with no induced draft as the furnace the rooms temperature will make a natural draft up th heaters flue in the off cycle .then when it runs it will get the basement air and pull nothing fron the furnace ID setup.any outside ducts dropping below the ground level into the basement will chill it out with those temps in the winter


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## samantha.77 (Oct 14, 2010)

I live in Winnipeg, Manitoba and the home is 50 years old with poured concrete foundation but has been updated extensively over the years has an energy rating of 78, good windows, sealing etc. I do have a gas conventional water heater that is the only thing venting through the chimney. I think the 4" diameter insulated duct he wants to run into my furnace room is for the water heater combustion, he says it will also help reduce the humidity in my home. I don't know how the pipe will reduce the humidity but that is the information he is telling me. I guess if I need it then I will let him install it.


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## kenmac (Feb 26, 2009)

It depends on haw large the room is. You need xxx amount of combustion air for xxx btu. If it's a small room & no air to get in for combustion. Then you may need the vent


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## yuri (Nov 29, 2008)

A Hometown gal eh,:thumbup:

I doubt VERY much that you need that pipe with the age of your house. I have installed high eff. units for 32 yrs in Wpg and we very rarely had to add a combustion air pipe in your age of home. Reason being that the vapor barrier in homes then was poorly installed, not glued to the joists like they do now so you will always have enough air infiltration to take care of a small BTU appliance like a water heater. Only if you have a large powerful JennAir cooktop fan and central vacuum running at the same time can you depressurize your house. Houses built in the last 20 yrs have to have that pipe by code as they are tight. With the installs we do now 98% of the people convert to a electric water heater and cap off the chimney to make the house more airtight. Costs the same to heat water here with elec as gas. Gas tanks last 6-8 yrs and cost close to a grand installed. Elec last longer so that is what I would suggest. Get 2 new CO detectors. Put one in the basement stairwell and 1 by your bedroom and you should be safe.

If you have the outside of your house redone with Tyvek wrap or have the stucco elastomerically sealed (rubberized spray on stucco paint and coating)then your house will be tight and you may need some combustion air.


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## hvac benny (Dec 29, 2009)

Based on the information you have provided no outdoor air supply is required. Code states that water heaters under 50 MBTUH don't require an air supply (B149.1 section 8.2.3).


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## kenmac (Feb 26, 2009)

hvac benny said:


> Based on the information you have provided no outdoor air supply is required. Code states that water heaters under 50 MBTUH don't require an air supply (B149.1 section 8.2.3).


 

That would depend on location.. IFGC 304.1 - 304.12list combustion, ventilation, dilution air requirements that we have to follow


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## hvac benny (Dec 29, 2009)

kenmac said:


> That would depend on location.. IFGC 304.1 - 304.12list combustion, ventilation, dilution air requirements that we have to follow


OP is in Canada, hence the use of B149.1.


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## yuri (Nov 29, 2008)

I wonder who supersedes who in the Great White North. Local building codes or gas code? I don't get involved in new home construction but know that in Calgary the furnace has to be interlocked by building code to run the fan with a fresh air intake if the kitchen exhuast fan is over 100 cfm or some such size. That may not be in the gas code?


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## kenmac (Feb 26, 2009)

hvac benny said:


> OP is in Canada, hence the use of B149.1.


 
I had no idea what B149.1 was. That's why I said all areas are different . I don't even know who all goes by the IFGC. Most of the towns around aren't even up to date on the IFGC. some still use 2003 while others use 2006. I don't know of any that are using 2010 code


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## hvac benny (Dec 29, 2009)

yuri said:


> I wonder who supersedes who in the Great White North. Local building codes or gas code? I don't get involved in new home construction but know that in Calgary the furnace has to be interlocked by building code to run the fan with a fresh air intake if the kitchen exhuast fan is over 100 cfm or some such size. That may not be in the gas code?



Building codes as well as provincial acts and regulations supersede code, but not if the requirements aren't up to the standards of the gas code. Basically whomever has the tougher requirement (eg. code says that combustion air vents must be 12 inches from finished grade, but the BC and Alberta acts and regulations require 24 inches). In BC we've gotten rid of requiring a fresh air intake into the return, but some inspectors still ask for it, or just that the furnace fan runs on low 24/7, or is timed to run 8 hrs of everyday. Again, this all depends on what city it's in.


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## yuri (Nov 29, 2008)

Yeah, and the climate. You probably have more humidity problems and mold issues than we do. We use a motorized Hoyme damper in our fresh air intakes as 95% of our sales are 2 or 3 stage units with continuos running ECM motors. Don't want to be sucking cold air in all the time or hot humid air in during the Summer.


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## beenthere (Oct 11, 2008)

National/international code is min requirements. Local jurisdiction can make tougher guide lines, but not lessen national/international code.


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## samantha.77 (Oct 14, 2010)

Thank you all for the information is it most appreciated. I just came across another decision I have to make. Another HVAC Technician told me that he wants to remove my fresh air intake which is hooked up directly to my cold air return (about 10' away from the furnace), he informed me that by bring the cold air from the outside directly into the cold air return is not a good idea since that cold air will be hitting the furnace fins and causing condensation. He told me to remove the fresh air from the cold air return and seal the hole in the cold air return and patch the concrete wall.

What do you think do I need to remove the fresh air duct from my cold air return I taught it was to provide fresh air to the furnace and duct work????? Now I am really confused...


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## yuri (Nov 29, 2008)

Have a motorized Hoyme damper installed in the fresh air pipe. Have it wired in so that it gets energized by the W (heat) terminal on the circuit board. That way it opens and mixes fresh air with the return air and does not shock the heat exchanger or cause condensation on it when the heat is off.

http://www.hoyme.com/


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## SPS-1 (Oct 21, 2008)

samantha.77 said:


> ... he informed me that by bring the cold air from the outside directly into the cold air return is not a good idea since that cold air will be hitting the furnace fins and causing condensation. .....Now I am really confused...


Condensation is caused by warm, moist air hitting a cold surface.


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## samantha.77 (Oct 14, 2010)

Thanks Yuri, I could mention the damper to the HVAC tech, but to my understanding he wants to remove it completely. What do you think do I need one or should I listen to him and have him remove it completely??


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## yuri (Nov 29, 2008)

If he removes it and you have a humidity problem or stuffy feeling then you will have to pay him to re-install it. You could try it an find out. If you have a problem then I would get the Hoyme installed (5" and pipe upsized) and if he does not seem interested then call some other contractors and ask to have one installed and enlarge the hole and upsize the pipe. Ideally that pipe should be 5" to do any good. 3" is useless and 4" not recommended. Does not sound like this guy knows what he is doing IMO. Probably looking at $500-$750 to recore the hole larger and install the damper. Less expensive if we don't have to pay a diamond driller/corer and can just enlarge the hole if it is just a stucco wall.


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## silver_flash (Sep 28, 2012)

I think the contractor is talking about makeup air. So when you turn your bathroom fan on. It pushes air outside and then air has to come into the house from some where. If the chimney is open the air will come from the chimney where your water heater co2 is vented. So new houses require a makeup air vent witch is a pipe that runs fresh air into the house. Newer houses need these because they are efficient. old windows and old houses have drafts and air can enter them easy. New houses are more air tight. Make up air vents are separate from air exchangers that you described on your furnace.


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## techpappy (Jul 8, 2012)

b 149.1 IS THE CANADIAN GAS INSTALLATION CODE which is adopted in most Provinces. Sometimes local authorities will add extra provisions but usually follow the B149. But as per other comment from "Winter Peg" said NOT Required

AND YOU DO NOT REQUIRE SEPARATE COMBUSTION AIR FOR THE HW HEATER AS STATED. unless your tank ios in a virtually hermetically sealed room ..air infiltration from rest of house should be sufficient for combustion..Is the room tightly closed up. Is it open to basment? If not you can put an air grill in the door to be sure OR just undercut the door to allow indoor air into the room.


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## beenthere (Oct 11, 2008)

This is a 2 year old thread.


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## silver_flash (Sep 28, 2012)

beenthere said:


> This is a 2 year old thread.


thank you. I'm new here.


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## beenthere (Oct 11, 2008)

We wee all new here at one time. 

Lot of people miss the date of the post.


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## samantha.77 (Oct 14, 2010)

As a follow up.

I had the cold fresh air intake which hook up to my cold air return removed and sealed up the concrete wall. I had a 95% efficiency furnace installed which has it's own combustion air and there is enough air for the water tank.

so far I have no problem, I just air my house out everyday to get rid of humidity if needed.


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