is my high efficiency furnace vent installed properly? I'm based in Toronto, Canada. In some recent cold winter weather, the exhaust is causing a lot of ice buildup on the surrounding brick. To my limited knowledge, lots of freeze / thaw cycles for brick is a bad thing, which can cause brick to deteriorate rapidly. So is this an issue? If so, is it worth correcting and are there any easy DIY solutions that you would recommend?

Could I change the venting to just be one vent, instead of two (right now the exhaust vents both up and down)? And maybe aim the exhaust a bit further from the brick?

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I am a Local HVAC Tech in the Toronto area. As stated, this exhaust is not installed according to local codes and the manufacturers installation instructions. There is no surprise that you are getting freezing condensation on the brick of the house. The reason for having the vent terminate straight out and away from the building is to avoid this. The facing of the brick will chip off after a few years of this. Another issue i see is that any exhaust for a high efficiency gas appliance must be insulated when being run in an unconditioned space (such as in a garage or running under a deck). Now if the termination is 2ft or less, you do not need to insulate the exhaust. However, in your situation there is a long termination, which requires it being insulated to prevent freezing.

My solution would be to cut off the tee at the end of the termination, slide on armaflex pipe insulation around the exhaust. You should have from where the tee started, to where the pipe enters the house fully insulated. Then using system 636 PVC glue and primer if doing it in cold weather, glue a system 636 PVC elbow onto the end of the termination so that it is blowing the exhaust straight away from the house. Then cut a 6" piece of system 636 2" PVC pipe and glue that into the elbow to help throw the exhaust further away from the structure. Doing all of the above would solve all the termination issues, and bring it back up to code.

  • Thank you Mnc123. What would an HVAC technician typically charge for that type of repair? It's freaking me out. Dec 30 '13 at 2:17
  • 1
    Your welcome. It would cost around $200 to have repaired. The 2" pipe insulation is quite expensive. Its not an incredibly hard thing to fix. At the same time you should get whoever repairs it to change the strapping used to hold the vent pipe. It will rust soon and may stain the white brick. Either wrap it in electrical tape, or have them use nylon coated strapping.
    – Mnc123
    Dec 30 '13 at 3:49
  • I thought that strapping looked a little unusual, thanks for the tips. I'll see if I can attempt it myself and if not, will pay someone (let me know if you'd be interested in helping if so). Dec 30 '13 at 3:58
  • Mnc123, I installed it myself. It wasn't that hard to do! Thanks. Jan 15 '14 at 16:43

The exhaust pipe discharge is too close to the house. It should extend 8 to 12 inches from the wall if using tee on vent end. The exhaust might have been placed in its odd position because of a gas regulator vent. I see the pipe exits near the gas service. From a survey of high efficiency furnace installation manuals, and my own experience installing my furnace, the exhaust vent termination must meet the following conditions (although the installation instructions may vary):

  1. Be at least 6 inches from operational window openings
  2. Be at least 3 feet horizontally from service regulator vents, extending 15 feet vertically (Applies to Canada, not US.)
  3. Extend 8 to 12 inches from walls if using tee vent. (This doesn't seem to apply if venting perpendicular to wall).
  4. Be at least 3 inches in the horizontal and 12 inches in the vertical from the intake pipe
  5. Be at least 12 inches off the ground or anticipated snow level (if applicable , definitely applies in Canada).

The tee at the end is optional unless your instruction manual says otherwise.

Although there is a limit on the number of 90 degree turns you're allowed to put in the vent, in your case, I'd cut off the tee and put an elbow that directs outward from the wall.

You must make sure that you maintain the slope so that the condensate drains back to the furnace.

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    Are these your rules, or are they rules/codes from a reputable source? If they are from a reputable source, can you please cite the source?
    – Tester101
    Dec 19 '13 at 18:19
  • Having the pipe 8-12 inches from the wall will likely put it in harms way, especially if it's sticking out right at head height of a small child on a bike.
    – Tester101
    Dec 19 '13 at 18:23
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    @Tester101, Primarily I used an installation instruction manual for a high efficiency Goodman furnace with Canadian instructions (since the OP is in Canada). I crossed referenced with other instruction manuals I found online. These manuals site CSA B149.1, Natural Gas and Propane Installation Code. I didn't post them because of possible copyright issues. I also did extensive research when I installed my own furnace. As for the pipe being in harms way, I'm sure the OP will take that into consideration.
    – Edwin
    Dec 19 '13 at 19:05
  • I've found some additional information and updated my answer to include the possibility of replacing the tee with an elbow that points perpendicular to the house.
    – Edwin
    Dec 20 '13 at 3:20
  • Adding a link to an online version of the instruction manuals you're working from is likely not a copyright issue. Also, it's typically not a problem to quote code, as long as you're not releasing the entire document.
    – Tester101
    Dec 20 '13 at 11:06

There are two things you need to look at to get an answer.

  1. Local Building Code
  2. Manufacturer's installation manual

Both of those will probably address how far away from a window or door and how far away from certain building materials the exhaust vent must be. So make a phone call to your local code authority and find the installation manual for your furnace.

The manufacturer installation manual will dictate the maximum length of the exhaust vent. It will also dictate things like slope and end treatment of the exhaust.


You'll probably have to maintain the Tee exit - it serves a couple of purposes - harder to block, and less prone to backdraft. Should be able to move it a bit further from the building.

That installation looks dubious (to me) as it stands in part due to the vent-end proximity to the window. Different codes in different places - the gas meter right next to the electric would not fly here, either - 10 foot minimum. Obviously that's OK with the Gas and Electric services in Toronto.

  • Thanks Ecnerwal, I guess the bar is lower in Toronto for safety then :) Dec 20 '13 at 14:59
  • Or the electrical folks have the sense to sniff for leaking gas before making sparks at the electric service ;-) These rules purport to be safety-caused, but often have other baggage and old turf wars behind them as much as anything. The window and carbon monoxide concern me more, really.
    – Ecnerwal
    Dec 20 '13 at 19:37
  • Ecnerwal, you were the only one who mentioned carbon monoxide as a potential hazard. What distance from the window do you feel the vent would be considered safe? I have a carbon monoxide detector in the house, but if I'm knowingly letting carbon monoxide fumes into the house unnecessarily if a window is open, I'd have a problem with that. How would I measure the carbon monoxide entering the home to determine if it were an issue? Would I just place my carbon monoxide detector right at the window, open it, and see if it eventually starts beeping? Dec 30 '13 at 4:01
  • @Mnc123 presumably knows your local code on the matter. CO is always present in exhaust gasses to some extent, and my recollection of vent placement advice down here was that it's 4 feet to the side or below - but I may well be but of date, as several things seem to think 12 inches/30cm is fine for DV. As for checking, a CO alarm with a digital display (as opposed to the alarm only types) is more likely to tell you anything useful if you're trying to see whether any is coming in (it may be at a level too low to alarm) but having the alarm-only type in the house covers the major problem.
    – Ecnerwal
    Dec 30 '13 at 17:01

Wow, everything looks wrong. The contractor that built your house needs to read a little book called "uniform building code."

  1. Like you noticed, your HVAC vent is wrong. Cut off all that PVC on the wall and install a vent/intake box.

  2. Your gas and electric are too close, UBC says your natural gas vent should be no less than 3 feet from electric service.

  3. There are no poles or "bollards" protecting your gas meter.

  4. I could keep going...

This is not only a poor install but it is against gas codes. You cant have combustion air vented into your appliance within 4 meters of your gas meter. If there is ever a leak, and you're burner is on, you're appliance becomes a bomb. I would have this looked at. Sorry man.

  • 2
    Can you give us a Code cite for that rule? (It makes sense, but a Code cite would make this a far better answer) Jul 13 '18 at 4:42

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