Can I use outside air?
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  1. #1
    Join Date
    Aug 2005
    Posts
    9
    I have a forced air heating and cooling system. My house had an addition put on a few years back and the contractor added vents for heat/cool air but no new returns. I need to add some. Do these systems ever get return air from the outside (through wall vent)? I also use a woodstove which vents a great deal of air out of my house through the chimney.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Air in always equals air out from a fan,and the return needs to be in the conditioned space.

    Why do you think you need more return in that area,as opposed to more supply??

  3. #3
    Join Date
    Aug 2005
    Posts
    9
    What replaces the air lost to the outside through the wood stove chimmey?
    Why does the return need to be in the conditioned space?

  4. #4
    Join Date
    Feb 2005
    Posts
    344

    Infiltration

    What replaces the air for the wood stove? Good question. Unless you have a wood stove that has provisions to bring in outside air for combustion, the replacement air is coming in through the cracks of your windows and house construction.

    This is why the "old" style wood stoves and fireplaces are more for looks than actually being practical heat sources. The air that is leaking in is unconditioned and will require more energy to temper it.

    To answer your second question; Take a plasic bag and blow into it. At some point the bag will be holding all the air that you have the lung power to provide. This is the same thing that happens to your house. If all the air was taken from the outside, the house would be like that plastic bag and the furnace blower would be overcome just like your lungs.

    Besides the pressure problem, how much are you willing to spend to have your heating/ cooling equipment running constantly. That is what it would take to temper that constant influx of unconditioned air.

    IMHO

    Best regards...

  5. #5
    Join Date
    Aug 2005
    Posts
    9
    Thanks for your responses. The reason that I am researching this whole thing is that my current serviceman claimed that without new returns, my system was not getting enough total air flow through the system. To remedy this, he added a vent on the side of the furnace to bring in extra air from the basement. This seems bad to me. What is your opinion?
    Also, I do use my wood stove a fair amount and it is located on an internal wall in my living room with no provisions for getting external air for combustion. Do you know of any ways to get external air to the intake opening of the stove?


  6. #6
    Join Date
    Oct 2004
    Posts
    3,400
    Originally posted by cobra888
    Do you know of any ways to get external air to the intake opening of the stove?

    Open a window.

  7. #7
    Join Date
    Feb 2005
    Posts
    344

    Open a window...

    That is the handiest way, but, not the best. If you want to do it economically you need to check into an ERV/HRV ventilation system.

    The only comment about taking a return at the furnace is beware of possible furnace and water heater venting problems. If the basement is tight enough the cut in return could upset the natural draft. If the drafts are mechanically induced- no problem.

    Goo luck...

    ps- really need retruns in the areas that are not getting air.

  8. #8
    Join Date
    Aug 2005
    Posts
    9
    I understand your point about blowing into a bag, but isn't that the case if their are no returns from the conditioned area? What if most of the returned air was from the conditioned area and only one return was from external air. Wouldn't the system only bring in extra air that it needed to replace air lost (as in out the chimney)?
    Also, would a simple vent between the first floor and the basement solve the problem of negative pressure and drafting because of the intakes on the side of the furnace which is bringing in basement air?


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