Vents in basement
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  1. #1
    Join Date
    Jan 2011
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    42

    Vents in basement

    I have a finished basement, with 3 original vent down below and one return vent on ceiling around 1000SQF

    I am dividing a room in there , so I called an HVAC person to help add extra vents

    he added one in and one return in that new room
    he also added another one from the main duct in the living space, so now I have total of 4
    He told me that code says not to have a return in the basement if the room is not enclosed?
    is this true. Will this cause positive pressure in the basement and could cause mold and other issues?

    Thanks

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,231
    Check for high humidity and condensation to avoid mold. Attempting to get some positive pressure in the basement is usually a good thing. Monitor the %RH in the basement. Best to maintain <50%RH in the basement. In green grass climates, a significant dehumidifier is needed for when the a/c is not running 10-12 hours a day.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  3. #3
    Join Date
    Jan 2011
    Posts
    42
    Thanks a lot for your prompt reply

    So you think having good humidity level (I have a dehumidifier) and no return vents in the open space in the basement should be ok?
    I only have one return vent in the basement for an enclosed room, is that sufficient.
    And last question when the HVAC person added two supply vents in the basement from the main , he drilled through the drywall and through the duct and put a register through the drywall, is that the proper way of doing it? as there is some gap between the register and the duct work (not sealed).

    Thanks again


    Quote Originally Posted by teddy bear View Post
    Check for high humidity and condensation to avoid mold. Attempting to get some positive pressure in the basement is usually a good thing. Monitor the %RH in the basement. Best to maintain <50%RH in the basement. In green grass climates, a significant dehumidifier is needed for when the a/c is not running 10-12 hours a day.
    Regards TB

  4. #4
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,841
    Returns should not be placed where there is the danger of drawing in odors, or in an area where harmful vapors (CO) could be drawn in. A negative pressure situation in any area is undesireable, basements included.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
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    5,058
    "room not enclosed" Was he referring to a mechanical room with your furnace and water heater?

  6. #6
    Join Date
    Jan 2011
    Posts
    42
    He was referring to the open space in the basement.
    I have a combustion register for the enclosed room for the furnace
    one return in the enclosed bed room in the basement
    and about 4 supply vents in the basement
    Do I need another return in the open space in the basement

    Thanks


    Quote Originally Posted by second opinion View Post
    "room not enclosed" Was he referring to a mechanical room with your furnace and water heater?

  7. #7
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
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    5,058
    Do you have one or two transfer grills for the combustion air for the mechanical room, and what is the size of the room and size of equipment?

  8. #8
    Join Date
    Jan 2011
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    42
    I have one combustion grill for the room around 6*6 feet
    I have 98% furnace (110BTU)
    50 Gallon water heater (40BTU)

    Quote Originally Posted by second opinion View Post
    Do you have one or two transfer grills for the combustion air for the mechanical room, and what is the size of the room and size of equipment?

  9. #9
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
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    The furnace if piped to the outside with two pipes will not be in the equation for the grill sizing. You need an upper and lower transfer grill sized for the water heater unless the mechanical room is large enough.

  10. #10
    Join Date
    Jan 2011
    Posts
    42
    Ok how about another return vent in the open space?

    Quote Originally Posted by second opinion View Post
    The furnace if piped to the outside with two pipes will not be in the equation for the grill sizing. You need an upper and lower transfer grill sized for the water heater unless the mechanical room is large enough.

  11. #11
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
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    Is there a door to the basement at the stairs?

  12. #12
    Join Date
    Jan 2011
    Posts
    42
    Yes

    Quote Originally Posted by second opinion View Post
    Is there a door to the basement at the stairs?

  13. #13
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,058
    From what you have discribed I see no reason not to ad a return to the open area to accomidate the supplies.

    I do have concerns about the single combustion air grill and its size. There should be two one within 12 inches at the top and bottom. They should both be a minimum of 40 square inches net area. An 8x8 would work

    The second issue would be the registers that where cut in and have gaps.

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