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  1. #1
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17

    Cold Air through Fresh Air Vents

    I hope this isn't a recent duplicate, I've been searching a while and can't find good answers.

    Info:
    Just built new house in Michigan with 92% efficiency furnace, gas power vent water heater and gas clothes dryer. They put a fresh air vent in the laundry room (main floor), fresh air vent into furnace return (basement), and two into the utility room (1 at the ceiling and one at the floor)(Basement). I know the two in the utility are for water heater, furnace has its own intake for the combustion through the PVC. I checked all of them tonight and cold air is flushing in through all of the vents. The basement is constantly colder than it should be, and the house always feels drafty, I know fresh air is important in the the house but its killing comfort and the whole point of efficiency. My parents have had two high efficiency furnaces and gas water heater and gas dryers and the HVAC contractor didn't install the fresh air vents. Their house is 30 yrs old, larger than ours, feels much more comfortable and I bet they will be spending less on heating costs each month than we will in our 1 month old house.

    Question:
    What are my options for stopping the cold air from the vents? Do I need so many vents?

    Options I've found online but not much info on each
    - Have vent go into bucket
    - Put elbows on vents to hold cold air
    - Dampers

    I know an HVAC guy that I will contact sometime next week, but would like some other opinions.....I saw our gas bill for the last month tonight and not happy for an "Energy Star" house...hense the reason for asking tonight.

    Any help will be greatly appreciated!!

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,369
    The fresh air intake for the return air side of the furnace should have a motorized damper on it so it only admits fresh air when the furnace blower is running.

    The other fresh air vents you mention...you should check with your builder if these are needed since you have combustion appliances (furnace and h/w heater) with dedicated combustion air inlets. Code may require a fresh air vent in the laundry room since it has a gas dryer...that also should be verified with your builder, and with the building department of the city you live in.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #3
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17
    Thanks for the reply

    If they have to stay... is there a way to block some of the cold air?

    Does putting 90 degree elbows into a J or U at the bottom of the vent work to block the cold?

    Thanks

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,369
    90 degree elbows won't do anything to stop cold air entry (especially if the inlet is low in the house, such as first floor or basement), especially if the house has any stack effect going on.

    I know I'm going only on scant info in your OP, but sounds to me like someone did not do their homework in regard to the design of how fresh air should get into your house. What you should consider doing, regardless that this is a new house, is get it blower door tested, with the extra intakes temporarily blocked (all of them). You want to see how leaky the house itself is. Just because a house is labeled an "Energy Star" house does not mean it meets the airtightness of an Energy Star specification for your size house. Lots of mistakes can occur in construction concerning air sealing of a structure.

    The amount the house leaks under a blower door test can give an indication how much natural or fresh ventilation is required to maintain proper indoor air quality. You may have too much ventilation, but only by testing and working with professionals who understand this will you get the answers you need.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #5
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,274
    x2 what shophound posted.
    I usually use barometric dampers on the fresh air
    intakes we do.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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