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  1. #1
    Join Date
    Nov 2002
    Posts
    31

    Huge combustion air vents are making my house too cold!

    I've just bought a house, custom built in 2006, Colorado.

    The utility room has two 50-gallon gas hot water heaters in it, the room also houses fire sprinkler system with massive water vessel, well pump pressure tank, water softener, etc.

    My issue is that the builder put in two huge combustion air vents to the outdoors, each 8" diameter (one high, one runs close to the floor). I understand that the hot water heaters need combustion air, but these large openings into my house are basically turning the utility room into the outdoors, so when it's freezing outside, it's @#$ cold inside, too. Thus the adjacent rooms in the basement are cold, as are the living spaces above the utility room.

    Note that there is no insulation in the room other than on the exterior side, above the concrete slab wall in the space between that and the ceiling joists there's maybe 1-2 feet of fiberglass insulation. I've thought about adding 3/8" rigid foam to the concrete walls where I can (there's electrical boxes, plumbing, gas, etc. touching the concrete so it's not possible to add it uniformly) and I plan on insulating the interior walls with fiberglass insulation to help the adjacent rooms stay warmer.

    But - this just doesn't seem right. I'm concerned about letting the room get so darned cold - that can't be good for the water softener, the hot water heaters, etc. It certainly isn't efficient to basically have the water heaters sitting in a room that could be 40 degrees in the winter (or colder?).

    I've done some rudimentary calculations - There are 2 x 40,000 BTU water heaters in the utility room, which is 160 square feet, ten foot ceiling height = 1,600 cubic feet.

    So my question is - given that this room is becoming a walk-in freezer all winter, how do you keep an outdoor vented space from becoming so cold? Two huge holes into my house is the opposite of efficiency and I'm seriously concerned about the heaters and softeners operating in potentially below-freezing conditions!

    Thanks for your help. If you ultimately recommend I have a professional come out, I'd love a specific type of expert who would really know what the heck they're talking about. I feel like I certainly could have a local HVAC guy out to look at it but I would want someone who knows what they're talking about.

  2. #2
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    14,305
    interesting? so this Utility Room is on the exterior of the home? It's not in a basement or Garage?

    I would get all the pipes (or any pipes) off the cement walls. Use "stand-off" or nail a couple 2x4 to the cement and attach the pipes to the 2x4.

    Next insulate the crap out of that room. then I would get some heat in there. sounds like the only way to do that would be electric baseboard heat? or if you have a boiler run that room on it's own zone.

    the 8" vents have to stay, period.

    p.s. you say the hot water tanks are 50gal? and only 40K btu's? could you check that again, cause that sounds a little small---thanx
    The Last four letters


    American = I Can, Republican = I Can, Democrats = Rats


    any questions

  3. #3
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    518
    You could convert to high eff. equipment which will directly pipe in its combustion air then you could cover those vents?

  4. #4
    Join Date
    Nov 2002
    Posts
    31
    Quote Originally Posted by jmac00 View Post
    interesting? so this Utility Room is on the exterior of the home? It's not in a basement or Garage?
    Sorry if I wasn't clear - the utility room is an unfinished room in a finished basement.

    Quote Originally Posted by jmac00 View Post
    I would get all the pipes (or any pipes) off the cement walls. Use "stand-off" or nail a couple 2x4 to the cement and attach the pipes to the 2x4.
    I don't think I can really move anything - the water heaters are all but 1/2" from the cement wall and there's a 1" copper pipe running outside for the landscaping line which hugs the wall tightly. The electrical and gas is attached to the cement wall as well. So I can put up maybe 3/8" rigid foam on this wall but I'd have to cut around a bunch of things. (And I'm not sure the rules about putting it so close to the water heaters)

    Quote Originally Posted by jmac00 View Post
    then I would get some heat in there. sounds like the only way to do that would be electric baseboard heat? or if you have a boiler run that room on it's own zone.
    the 8" vents have to stay, period.
    I've got direct-vent furnaces in the home so I guess putting an electric heater in there is my only choice? I'm really bummed that I'm basically forced to heat a room with two huge holes to the outside - that just seems whacky to me. And expensive.

    Quote Originally Posted by jmac00 View Post
    p.s. you say the hot water tanks are 50gal? and only 40K btu's? could you check that again, cause that sounds a little small---thanx
    Yep, 2 x A.O. Smith GCV-50 Residential Water Heater, Natural Gas, 50 Gallon, ProMax, Tall, 40,000 BTU


    Quote Originally Posted by mechanical'al View Post
    You could convert to high eff. equipment which will directly pipe in its combustion air then you could cover those vents?
    That's something I've thought of but would cost a few grand to replace 100 gallons of hot water capacity...

  5. #5
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    14,305
    Quote Originally Posted by randyl712 View Post
    Sorry if I wasn't clear - the utility room is an unfinished room in a finished basement.
    how many square feet is the basement? why not pull combustion air from the basement?

    Put a 10" holes in the utility room door (use a 12 x 12 return air grill, so it looks nice)
    The Last four letters


    American = I Can, Republican = I Can, Democrats = Rats


    any questions

  6. #6
    Join Date
    Nov 2002
    Posts
    31
    I've totally thought of that - the basement is large at around 1,500 sq ft and is open to the rest of the house (no doors closing it off) so technically it's much larger still. Looks like 2 x 12x12 vents from the basement to the utility room would supply the air necessary and allow me to close off those exterior intake vents. Any reason NOT to do this? I'm on the fence about which way to go. I just want a comfortable house without insane HVAC bills.

  7. #7
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    14,305
    Quote Originally Posted by randyl712 View Post
    I've totally thought of that - the basement is large at around 1,500 sq ft and is open to the rest of the house (no doors closing it off) so technically it's much larger still. Looks like 2 x 12x12 vents from the basement to the utility room would supply the air necessary and allow me to close off those exterior intake vents. Any reason NOT to do this? I'm on the fence about which way to go. I just want a comfortable house without insane HVAC bills.
    knockyourselfout, I would plug those holes right after I put the 12x12 grills in the door, there is no reason you can't draw combustion air from the basement.
    The Last four letters


    American = I Can, Republican = I Can, Democrats = Rats


    any questions

  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    2 X 50 gallon water heaters = 1 tankless with room to spare. Probably wouldn't cost much more either and free up a ton of space.

    Natural draft and single pipe appliances should be banned in new construction. No need for them anymore except for replacements. Too many issues and potential risk with proper tight home construction.

    But for now +1 on combustion air form the basement. It will reduce the point source cold drafts, but remember the actual air requirements and heat lost doesn't change.

  9. #9
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    518
    ya you can do that though it will induce infiltration as you will be placing the whole structure in a slight negitive the air must come from some where possiblely causing other cold drafts

  10. #10
    Join Date
    Mar 2006
    Location
    Denver/Boulder
    Posts
    2,289
    Quote Originally Posted by randyl712 View Post
    I've just bought a house, custom built in 2006, Colorado.

    The utility room has two 50-gallon gas hot water heaters in it, the room also houses fire sprinkler system with massive water vessel, well pump pressure tank, water softener, etc.

    My issue is that the builder put in two huge combustion air vents to the outdoors, each 8" diameter (one high, one runs close to the floor). I understand that the hot water heaters need combustion air, but these large openings into my house are basically turning the utility room into the outdoors, so when it's freezing outside, it's @#$ cold inside, too. Thus the adjacent rooms in the basement are cold, as are the living spaces above the utility room.

    Note that there is no insulation in the room other than on the exterior side, above the concrete slab wall in the space between that and the ceiling joists there's maybe 1-2 feet of fiberglass insulation. I've thought about adding 3/8" rigid foam to the concrete walls where I can (there's electrical boxes, plumbing, gas, etc. touching the concrete so it's not possible to add it uniformly) and I plan on insulating the interior walls with fiberglass insulation to help the adjacent rooms stay warmer.

    But - this just doesn't seem right. I'm concerned about letting the room get so darned cold - that can't be good for the water softener, the hot water heaters, etc. It certainly isn't efficient to basically have the water heaters sitting in a room that could be 40 degrees in the winter (or colder?).

    I've done some rudimentary calculations - There are 2 x 40,000 BTU water heaters in the utility room, which is 160 square feet, ten foot ceiling height = 1,600 cubic feet.

    So my question is - given that this room is becoming a walk-in freezer all winter, how do you keep an outdoor vented space from becoming so cold? Two huge holes into my house is the opposite of efficiency and I'm seriously concerned about the heaters and softeners operating in potentially below-freezing conditions!

    Thanks for your help. If you ultimately recommend I have a professional come out, I'd love a specific type of expert who would really know what the heck they're talking about. I feel like I certainly could have a local HVAC guy out to look at it but I would want someone who knows what they're talking about.
    Quote Originally Posted by randyl712 View Post
    I've totally thought of that - the basement is large at around 1,500 sq ft and is open to the rest of the house (no doors closing it off) so technically it's much larger still. Looks like 2 x 12x12 vents from the basement to the utility room would supply the air necessary and allow me to close off those exterior intake vents. Any reason NOT to do this? I'm on the fence about which way to go. I just want a comfortable house without insane HVAC bills.

    Where in Colorado? What is your altitude?

    You zero in on the water heaters, but you mention nothing about space heating equipment for the home. What heats the home? Where is that system? How many BTU's is that rated at? Does it have combustion air piping as well?



    Quote Originally Posted by motoguy128 View Post
    2 X 50 gallon water heaters = 1 tankless with room to spare. Probably wouldn't cost much more either and free up a ton of space.
    I disagree. One tankless would rarely give the same preformance when a contractor thought that two 50's were appropriate. Custom homes usually mean more bathrooms than typical and high end tubs/ multi-head showers, etc. On top of that you are almost certainly not accounting for the reduced BTU capacity that goes with most locations in Colorado, a fatal thing to disregard in this state. That being said, niether of us knows without more information.
    What lies behind us and what lies before us are small matters compared to what lies within us.


    Two pressures, four temperatures = SUCCESS!


    Boulder Heating Contractor


    For Consumers:

    For HVACR Professionals:


  11. #11
    Join Date
    Nov 2002
    Posts
    31
    Quote Originally Posted by darctangent View Post
    Where in Colorado? What is your altitude?
    South metro area, under 6,000 ft.

    You zero in on the water heaters, but you mention nothing about space heating equipment for the home. What heats the home? Where is that system? How many BTU's is that rated at? Does it have combustion air piping as well?
    There are direct-vent gas furnaces in the home also but not in this utility room. They are in other little rooms with direct venting to the outside. They aren't nearby right now but I believe them to be 75,000 BTU units.

    I disagree. One tankless would rarely give the same preformance when a contractor thought that two 50's were appropriate. Custom homes usually mean more bathrooms than typical and high end tubs/ multi-head showers, etc.
    Spot on - it's a large home, 5 bathrooms, whirlpool tub in the master, two shower valves/showerheads in the master shower as well.


    I think we may be inclined to try and insulate the utility room on the interior walls and add a small space heater to keep the room from freezing. It's not ideal but my wife is not sold on the idea of putting holes in the walls for the return registers to open the room to the basement... and the water heaters aren't going to last forever so conceivably we could replace them with direct-vent or tankless down the road and seal up the ducts at that time? Sigh. Wish there was a better solution right now.

  12. #12
    Join Date
    Mar 2006
    Location
    Denver/Boulder
    Posts
    2,289
    Honestly Randy,

    The steps you outlined are more likely to be a treatment for the symtpoms you report, not the actual problem. You need a real professional opinion, not the guesses you will get with the information we have. There are some aspects of the information you have provided that don't line up well with the general design principles that a good contractor would follow, so I think there pieces we are missing. Only an on-site visit from someone properly qualified will be able to deal with your situation. I don't service your area, but I am likely to know of someone who does. If you forward your contact info to me (email address in profile, just click on my name, then the about tab), or alternately post you email adddress in your profile (NOT HERE!!) I will put you in touch with someone. You may also click on the link in my signature line and then fill out a contact form if you wish. Any of the three methods will work.


    PS- I have an idea how one might reduce exceess air moving through the combustion air piping, and I will pass that along to my contact.
    What lies behind us and what lies before us are small matters compared to what lies within us.


    Two pressures, four temperatures = SUCCESS!


    Boulder Heating Contractor


    For Consumers:

    For HVACR Professionals:


  13. #13
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,582
    I would not seal the openings unless a pro confirms you can.

    I would ventilate the room with specially made make up air units that run only when making water. (Fan in a can)
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

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