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  1. #1
    Join Date
    Feb 2008
    Location
    Montreal, Quebec
    Posts
    2

    Cool 100% Return in the Basement

    Basic Picture, Montreal, Quebec, 3 Story House (Main Floor + Upstairs = 2500SF, basement about 1200SF) Built 1976.
    I had a blower test done, ACH = 8.06 @ 50 PA (about .34 under normal conditions)

    I have cold / hot spots on my third floor due to improper duct work/sizing.

    Contractor's Solution:
    Run 1 vent to the attic and new registers in the ceiling of each room: Plus balance the system. I agree with this. AND
    Cancel all the existing air returns and make it 100% return in the basement.
    To do this he will need to install 3 sets of transfer grills (2 walls and 1 door). BTW, we leave our bedroom doors open, so that's not a concern.

    QUESTIONS
    1) Does it make a difference where the returns are located?

    2) Obviously he feels the current returns are insufficient, but why does he want to cancel the existing? Why not just add.

    3) Sorry I can't quote verbatim: But he told me that 100% return in the basement will be more efficient in winter and summer. In summer it will draw in the already cooler basement air first, and in winter draw in the ___ air, and this is the ideal system.

    4) I have read a lot in the forums about zoning.
    I'm confused as to it being good or bad. Now I could easily add motorized zoning, 1 zone for my 3rd floor and 1 zone combined basement and main floor. Please answer, if installed correctly is this good or just a sales pitch. (2 stage, VS)

    Cheers,
    Andrew

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,818
    Without knowing the full path for the return air. Can't say how well it will or won't work .

    Sounds like you need balancing no matter which way you go.
    Zoning is most likely your best option.

    Get another estimate or 2.
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  3. #3
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,896
    Twilli says in most places pulling return from the basement would be.....


    No Heat No Cool You need Action Fast

  4. #4
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    A duct to the attic, new 3rd floor ceiling registers, and balancing all sound like good ideas.
    Without seeing the house, I don’t know how easy it would be to zone. Providing 100% return air back to the heater is a definite must. The same effect of transfer grills can be achieved by cutting something off the bottom of the doors, just in case they get closed.

    You’d have to ask the guy why he wants to remove the existing returns. It sounds like a waste of time and money, but maybe that’s the only way you can get 100% return air. In most cases, you shouldn’t pull the return from the basement. Depending on the heater, it could cause odor problems.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,818
    Quote Originally Posted by bobb25 View Post
    Providing a minimum of 100% return air (I like 120% of supply) back to the heater sounds like another good idea.
    Where does the 20% excess go.
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  6. #6
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,510
    pulling just cold air back can cuase problems also. You want a mixing of the air from the living area of the house. Cold air from the basement alone can cause odors and if the air is to cold it will cause ice up problems and or other problem with heating.

    if you need more return the try to get more from the living space.

    zoning is a good option but not knowing you house all is just guess work

    call a couple others for options

  7. #7
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,896
    Twilli agrees and wonders why anyone would remotely consider that? Plus it may not pass inspection unless certain circumstances are met.
    No Heat No Cool You need Action Fast

  8. #8
    Join Date
    Aug 2003
    Location
    Central Kentucky
    Posts
    6,247
    If you have fuel fired appliances in your basement this suggestion of 100% return air from the basement could have some deadly side effects.

    You would be better served to find some areas that ducts can be run for return also.
    Have you set up a Google alert for Carbon Monoxide yet?
    Click here to find out how.

  9. #9
    Join Date
    Feb 2008
    Location
    Montreal, Quebec
    Posts
    2
    First Thank you for some very helpful info.

    Getting a 2nd opinion was my first choice. I went through the yellowpages and could not find one other company that would do a load calc. They all just use the rule of thumb method, and a few even told me over the phone the size heat pump I need for 2500 SF.
    DOES Anyone have a referral in Montreal?

    Not sure if it makes a difference, my basement is a fully furnished apartment, complete with kitchen and my mother-in-law lives there (sympathies accepted!)

    I have a Gas Furnace, with a Heat Pump. The system also has an electric duct heater (the duct heater helps avoid starting the gas furnace because I pay VERY cheap electricity when outside temp is above 10 F. Below 10 the system switches to gas only)

    Currently I have 2 vents coming out of the furnace. 1 supplies air to the basement and main floor. The second suppliers air to the 3rd floor. Motorized Zoning is very easy. It also has 1 duct coming in for the return air.

    Therefore, after running new ducts up through the attic, I will not be using the existing 1duct that used to supply air to the third floor. WHY not use the old air supply ducts as air returns? Each room already has floor registers, and it would be very easy to adjust in the furnace room to make it an air return...just seems so simple to do.
    Last edited by awhe; 02-24-2008 at 09:51 PM.

  10. #10
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,510
    maybe take the ducts you have feeding the floors alreading and zone them and the duct you run to the third floor make return

    return on the top floor would be better served if in the cieling rather then in the floor

    as long as the exsisting ducts are able to be zoned.

    a v-drive airhandler would also be best served for this type zoning

  11. #11
    Join Date
    Apr 2002
    Posts
    11,808
    Don't do it.

    In the summer yes, it would cool the house, in the winter it will increase your infiltration well above 0.34

    A major component of that 0.34 air changes will be stack effect. Hot air rises, pressurizes the upper levels and escapes the home. Lower levels go negative and draw in cold air from outside. You will be accelerating this process with all the return from the basement and increasing your heating bill.

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