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High-efficiency ventilation question

Shaun Member Posts: 1
I had four contractors (all on Con Edison's list of approved installers) come to my house to talk about replacing my 40 year old gas hot water boiler (it's around 100k btu output but I think a smaller size will be fine because it has a hot water coil we're not using, and the house is much better insulated now than when it was built).

One told me it was okay to vent through the existing flue because it's a straight run (less than 20 feet).

One told me they had to go through the wall but it was okay to terminate under my deck.

One said no, you can't dump hot moisture under the deck, but he could continue the pipe past the deck.

One said no, once the pipe is outside you have to terminate there, can't continue it, so he'd have to go through a different wall, farther away (requiring going through two different concrete blocks).

I'm afraid to ask a fifth guy!


  • Steamhead
    Steamhead Member Posts: 16,888
    What type of boiler

    are they going to install? 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Tim McElwain
    Tim McElwain Member Posts: 4,628
    You do not want

    to terminate a vent under a deck. Extending it out past the deck may cause extreme cooling and possibly freeze.

    Old chimneys can be used as a chase provided no equipment is vented into the chimney.

    All this depends on the equipment you are going to install and its specifications.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Best bet...

    Defer to the appliance manufacturers installation instructions. If they don't say, then defer to the National Fuel Gas Code.

    None of the manufacturers I have read would allow it to be vented below a deck.


    There was an error rendering this rich post.

  • jp_2
    jp_2 Member Posts: 1,935
    edited May 2010
    heck with code and manufacturer guildlines

    how about some plan old common sense?

    why would you  "want " to dump combustion gases where people normally sit or gather?   do you put a picnic table next to a septic tank vent?  do you huddle next to the car exhaust to get warm in winter?

    click on "Find a professional" at top of screen.

    and keep asking  questions so you can learn more about what is needed in an installation, you'll be headed in the right direction then.

    or if you have a boiler in mind, find their web site and look at the installation guidelines, lots of good pictures on where and how to vent properly......

This discussion has been closed.