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  1. #1

    cold air return vents in the basement (have some input to share)

    Hello guys I have a question concerning installing a cold air return in the basement. I had a HVAC company come to my house and told me the following, taught I would share with you all and maybe get some input on the situation.

    He said DO NOT put any returns in the basement, it is acceptable to open up some supply registry to get some warm air blowing into the basement use a fan to circulate the air but no returns. His response was that he use to put returns in the basement and it works to balance out the pressures but soon realized it did not work the same for every house due to their basement layout and in some cased it lowered the air pressure in the basement causing things such as back draft, increased humidity in the home, excess condensation which all seems to go away when the return was closed off.

    His advise was to be on the safe side and just open up some warm air registry to blow air down and use fans to circulate the air instead of installing a cold air return, he also advised that it is better to have a slightly positive pressure in the basement than a negative pressure.

    Another thing he mentioned that I would like to discussed was that the only way I can have a cold air return in the basement was if I put a 5" dia insulated flex duct from the outside (fresh air intake) and bring it into the basement and loop it up like a "U" this way fresh air is introduced, will balance out the pressures and the cold air return can circulate fresh air through out the house. He also advise do not put the flex duct directly into the cold air return because he has seen frost developed in the inside of walls and he showed me some pictures as well it is never a good idea to have -30 deg C temp passing over your furnace the best was was to do the "U" loop thing and let the cold air return pick it up.

    I don't know if that all makes sense just taught I would mention it and get some feedback.

  2. #2
    Join Date
    Dec 2010
    Location
    Rock Falls IL
    Posts
    33
    Smantha,
    My furnace and water heater are in a sepate area of the basement with a fresh air inlet in the that room. I did have a return duct installed near the floor in my family room area and it is much more comfortable than before the installation. The lower half of the room was always very cold. We used to have to use electric baseboards to be comfortable. Since the new return was installed we have not had the electric heat on one time. I only have one of my supply registers open (in the ceiling) and it is very comfortable. When you think about what warm air wants to do and what cold air wants to do.... You may want to get a second opinon. My HVAC installer said it was a good idea for my layout.
    joe

  3. #3
    thanks for the reply joe, I am going to have another company come in the weekend will be interesting to hear what their response would be.

    samantha

  4. #4
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190
    Your contractor has given you sound advice! Don't put a return grill in the basement with atmospheric (non completely vented appliances) water heater or warm air gas furnace.
    The leakage from the return duct and the unit cabinet will draw, in fact maybe too much. Flue gases could easily be pulled into the basement.
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  5. #5
    Join Date
    Jan 2010
    Location
    Athens GA
    Posts
    1,234
    Your contractor is telling you you the truth.
    It is always bettor to be safe than sorry.If you have even an average home,simply turning the kitchen vent and the bathroom fan on at the same time could exhaust enough air to turn your house into a negative pressure situation.Since air like water will take the path of least resistance to replenish itself,that means down the chimney witch could bring products of combustion into the basement.If you had a return air in the basement it would process that CO into the supply duct into the whole house.
    If you had sealed combustion products or an ERV connected to your duct system that might not be a problem.These things are a very expensive solution to having a return in your basement.Just put one or two supplies in and forget about possibly putting yourself in danger.

  6. #6
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,721
    Ever heard of Darwin awards? The people who put their generator in the basement. The people heating with their oven who threw their CO detectors in the back yard because they wouldn't shut up? If you have antiquated draft appliances, you might just be an applicant.

    The approach you are suggesting is a really good way to cut down on diaper costs (elderly and very young go first) and college costs.

    Are you the type who goes to the doctor and tells him what surgery you need? Do you realize people go to school for hvac and building science? What you might want to consider is stating the PROBLEM you are hoping to solve instead of your half baked solutions and leaving the pro's to wonder what the heck you are hoping to accomplish.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  7. #7
    Join Date
    Jan 2007
    Location
    Coloma MI
    Posts
    214
    My home has 5 Supply Vents and 3 Returns in the basement. As long as you have an equal amount of air going in through the supplys as you do coming out on the returns it will not create negative pressure.

  8. #8
    Join Date
    Nov 2010
    Location
    Canada
    Posts
    59
    samantha77 - sorry but I don't see in your post the reason why you wanted the return in the first place - are you renovating the space, or find it cold ? Proper balance between supply and return is important to overall IAQ ( Indoor Air Quality ), and in many cases the basements were just not designed to be converted to usable space, so adding any ducting in the basement could impact your overall comfort.

    The U shape is a cold air trap, for the combustion air for your appliances - if you have a newer furnace with direct vent and supply it would be less of an issue - also if you have an electric hot water tank, again less of an issue.

    If your furnace and the hot water tank are in an isolated room, a fresh air supply can be installed ( the U duct ), and would supply the needed air, but this needs to be done by a pro that will know the amount of fresh air needed.

    If on the other hand you are after improving the air quality in the house, maybe you should be looking at HRV or ERV depending on your location one works better than other - again this is something best install by a pro, as they need to be pressure balanced to be pressure neutral ( ie. the same amount in as out ).

  9. #9
    kenney t Guest
    sammatha77 listen to your contractor. DON'T do it. he has his reasons he's the pro unlike half the guys on this site,there home owners that don't know any better. get a 2nd opinon from a pro

  10. #10
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Every house I've been in has at least some basement return. By code they can not be within 10' of a nonsealed combustion appliance. I can see not running the basement into a negative pressure but if there is an equal,or greater, amount of supply what's the issue?

  11. #11
    Hello guys thanks for the respondse.

    The reason I asked the question was becasue my basement is cold and I use it mostly as living space. I called in a couple of contractors and some say by installing a cold air return vent in the basement will help warm up the basement and will make it more comfortable. While others say do not put one in, this conflict of information had me really confused to the point I am wondering who to believe.

    You can clearly see my problem as in the forum some say it's "O.K is supplys=return" while others say "its not O.K be on the safe side might pose a problem as with the contractor".

    As for "Tedkidd" comment, what is the point you are trying to make? Seems kinda rude maybe you can tell me who the real professionals are when more than one professionals have two completely but valid opinion.

    The question is quite simple "Do you install a cold air return in the basement". The answers I get are "yes you can" and "no you cannot". So which one is it?

    I don't think I am going to have one install just to be safe, I do have a hi-efficiency furnace that has it's own venting but have a conventional gas water heater that still uses the chimney, so I don't want to distribute any gases through my house.

    I do have more than one CO detector install Mr. Tedkidd does that still make me an applicant?

  12. #12
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Quote Originally Posted by samantha77 View Post
    Hello guys thanks for the respondse.

    The reason I asked the question was becasue my basement is cold and I use it mostly as living space. I called in a couple of contractors and some say by installing a cold air return vent in the basement will help warm up the basement and will make it more comfortable. While others say do not put one in, this conflict of information had me really confused to the point I am wondering who to believe.

    You can clearly see my problem as in the forum some say it's "O.K is supplys=return" while others say "its not O.K be on the safe side might pose a problem as with the contractor".

    As for "Tedkidd" comment, what is the point you are trying to make? Seems kinda rude maybe you can tell me who the real professionals are when more than one professionals have two completely but valid opinion.

    The question is quite simple "Do you install a cold air return in the basement". The answers I get are "yes you can" and "no you cannot". So which one is it?

    I don't think I am going to have one install just to be safe, I do have a hi-efficiency furnace that has it's own venting but have a conventional gas water heater that still uses the chimney, so I don't want to distribute any gases through my house.

    I do have more than one CO detector install Mr. Tedkidd does that still make me an applicant?
    Every basement situation is unique but still must be dealt with. You never want to depressurize any room that has an open combustion appliance. If you installed a direct (sealed) combustion water heater and there is no other gravity vented appliance in the basement then a return is ok.

    As far as condensation or icing; Pressurizing one part of the house will depressurize another part and icing is possible anywhere that air is being pulled back in.

  13. #13
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,021
    Samantha,

    The issue is where will you get the air to burn with the gas in the furnace? Remember that if there is exhaust gasses from burning gas in the furnace going out of the house, the air to replace it must come from somewhere.

    IF (and each house is unique) there is not enough 'combustion air' coming into the basement, the return vent 'could' suck burnt combustion gasses (what is normally exhausted to the outside) backwards into the basement. These gasses include CO (carbon monoxide), which is oderless, colorless, tasteless... but DEADLY!

    The symptoms of CO poisoning are a headache, feeling lethargic, and then you just do not wake up one morning... Not meaning to scare you, but lots of folks are victims of CO poisoning every winter due to furnace and water heater issues... Just trying to keep you and your family safe and healthy...

    My advise: Get someone that is a specialist in building science (or at least someone in the HVAC industry that understands airflow) to evaluate "Adequate combustion air supply" BEFORE you make any modifications to the basement heating.

    Hope this helps.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

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