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  1. #1
    Join Date
    May 2007
    Posts
    7

    Cycling cold air from basement all through the house

    Greetings:
    I am planning to run an 8" round conduit from basement to attic and in attic - split that into four 6" conduit and take it into the middle of 4 bedrooms in the 2nd floor.
    An inline duct fan near the bedroom ceiling vent will pull and an 8" duct fan in the basement will push. I will need to figure out how to have a valve system in place so that only the valve to the 6" duct will only open when the fan on that duct works. Then I can time (take turns) to run the fans in each bedroom. Basement push fan always runs.
    This will bring the cold air from basement into the 2nd floor and keep the house cooled.

    In winter I will reverse the process so that hot air is brought down to the basement and will naturally rise again to keep the house warm (rather than escaping through the attic

    is this a good plan.

    Thanks
    SJ

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Is there somebody out there putting this idea into people's heads? I think this is the second time that I know of someone has proposed this idea to this forum. My answer is still the same...it will not cool your upper floors in summer.

    Reasons?

    a) If you move air from one region to another, you must displace the air in the region air is being introduced into

    b) Where is that air to be displaced to? Outdoors?

    c) Duct heat gain. By the time the air reaches each area, it will have warmed to where it will have little to no cooling effect where it is desired

    d) Duct booster fans can't move enough air to satisfy intended heat load. Low velocity of air through ducts will only aggravate heat gain mentioned in previous bullet

    e) Basement must continuously replenish the cold air in order to continue cooling effect for upstairs areas. If warmer air is to be returned from upper floors to be cooled by the basement, then pumped back upstairs again, the basement will quickly cease to be a source of cooling. As walls, floor, and ground surrounding basement warm up, what little cooling effect there is will be lost entirely

    I hate to burst your bubble but in the end I can save you a lot of frustration and disappointment if you'll mull over the bulleted items.
    • 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
    May 2007
    Location
    Colorado
    Posts
    101

    Wink

    1.) Get a cardboard box and cut a whole in one side of the cardboard box and then a corresponding whole on the other side. Make sure to leave the bottom intact.

    2.) Take some aluminum foil and line the bottom of the box.

    3.) Place a box fan on one side of the box so the air blows through the holes you cut in step one.

    4.) Fill the bottom portion of the box with ice, but not past the point of the aluminum liner.

    5.) ENJOY A/C!

  4. #4
    Join Date
    May 2007
    Posts
    7

    Smile

    Thanks Shophound.

    I have an Suncourt HE150 air exchanger in the basement that brings in fresh air - ( still cooler than the 1st floor and 2nd floor air ) into the basement. To answer your question:

    >>b) Where is that air to be displaced to? Outdoors?

    My understanding - since the basement air is forced down from the 2nd floor ceiling - colder air being heavier will waft downwards and the hotter air will waft upwards into the attic and the attic fan will force it out

    >>c) Duct heat gain. By the time the air reaches each area, it will have warmed to where it will have little to no cooling effect where it is desired

    What if I insulate this proposed duct ?

    >>d) Duct booster fans can't move enough air to satisfy intended heat load. Low velocity of air through ducts will only aggravate heat gain mentioned in previous bullet

    Is there a fan that you could recommend? It doesn't have to be inline duct fan - I can mount it outside and connect it to the duct

    >>>e) Basement must continuously replenish the cold air in order to continue cooling effect for upstairs areas. If warmer air is to be returned from upper floors to be cooled by the basement, then pumped back upstairs again, the basement will quickly cease to be a source of cooling. As walls, floor, and ground surrounding basement warm up, what little cooling effect there is will be lost entirely

    We spent 55% time in 1st floor, 35% time in 2nd floor and 10% in basement.

    A brief overview of the house - it is about 4500 square feet in two floors - plus basement is 1900 square foot. Basement is only partially finished, I only have a little game room/exercise room there now
    I have two HVAC units - one in basement and another one in 2nd floor utility room. All brick home - very well insulated - built in 2005

    Thanks for your time

    SJ22

  5. #5
    Join Date
    May 2007
    Posts
    7

    Smile

    Jasruby79, Thanks, I will keep your suggestion as Plan B

    ;-)
    SJ22

  6. #6
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    I think the biggest weakness of this plan is a low amount of BTUs available from the basement for heating or cooling. My amateur opinion is that is even more of a problem than duct losses or fan CFM, but nobody I know has approached this idea using measurement of heat/cool available.

    If you insist on trying this, you might consider a fan from Fantech. Look for a CFM vs. static pressure table, with decent CFM at 0.2-0.4 inch (water column) static. You will find some good numbers with Fantech and some other non-cheap brands. Panasonic makes some inline fans which meet this goal too.

    Is your air quality in the basement good enough that you want to supply that air throughout the living area?

    I have myself had some original thoughts about conserving AC usage, but usually when I get enough info from professional sources on the subject, I see some fatal flaw in my invention. Better to either research thoroughly first, or slap together a 1st trial version and be ready to scrap the idea if it disappoints (or re-do it). Best of luck if you try this.

    Hope this helps -- Pstu

  7. #7
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    Sounds like a good idea to circulate any residual Radon in the basement throughout the house.

    paul

  8. #8
    Join Date
    Jul 2005
    Posts
    717
    [QUOTE=tecman;1495052]Sounds like a good idea to circulate any residual Radon in the basement throughout the house.

    paul[/
    ************************************************** ****
    Hey, tecman,what makes you say that? do you have any proof there actually is radon in the posters (sj22) basement?

  9. #9
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    Hey, tecman,what makes you say that? do you have any proof there actually is radon in the posters (sj22) basement?
    Just a thought. There is likely Radon in everyones basement to some degree, in many parts of the country. Just too small to be a problem for many. I would have it tested, if not already done.

    paul

  10. #10
    Join Date
    Apr 2007
    Location
    Philadelphia
    Posts
    2,193
    your gonna run 4 fans in the bedrooms?? one fan in the basement?sound like alot of work.
    why not run a a/c?

  11. #11
    Join Date
    May 2007
    Posts
    7
    Paul/Tecman - there is no radon in the basement - I had tested it out

    d_griff - I have two air HVACs. The fans I mentioned are duct fans that don't consume too much electricity. May be all I need is one big fan (need not be in the duct) to push the basement air through the duct into the 4 rooms in 2nd floor. The challenge is how do I make sure that all rooms gets almost equal air from basement?

    pstu - I have an air exchanger in basement - that brings in fresh air from outside - still it is 6 degrees colder than 2nd floor.
    I do not have radon in the basement

    To run the conduit from basement to 2nd floor is not difficult - I have closets through which I can shoot the duct straight to reach the attic and then do two 90 degrees to bring it right on the 2nd floor ceiling facing down

    how do I make sure that all rooms gets almost equal air from basement?


    Thanks
    SJ22

  12. #12
    Join Date
    Aug 2006
    Location
    NY
    Posts
    230
    Quote Originally Posted by sj22 View Post
    Greetings:
    I am planning to run an 8" round conduit from basement to attic and in attic - split that into four 6" conduit and take it into the middle of 4 bedrooms in the 2nd floor.
    An inline duct fan near the bedroom ceiling vent will pull and an 8" duct fan in the basement will push. I will need to figure out how to have a valve system in place so that only the valve to the 6" duct will only open when the fan on that duct works. Then I can time (take turns) to run the fans in each bedroom. Basement push fan always runs.
    This will bring the cold air from basement into the 2nd floor and keep the house cooled.

    In winter I will reverse the process so that hot air is brought down to the basement and will naturally rise again to keep the house warm (rather than escaping through the attic

    is this a good plan.

    Thanks
    SJ
    A 8" duct to feed (4) 6" outlets??!!!

    @ .1 static a 8" duct will push approximately 225 cfm. One 6" duct given the same static will push 125 cfm.

    225 cfm split by (4) 6" ducts???, ....do the math.

    Granted, most inline fans move more than .1 static, but you're not going to move adequate air flow into (4) 6" ducts from 8" main unless your fan is moving .4- .5 static.

    What's the square footage of the rooms that you're feeding? What is the temperature/RH% of the basement? The quality of the air you're drawing from the basement determines your BTU per lb of dry air. If your RH is high, your free cooling effect from latent heat of evaporation is non existence. Read a psychometric chart and see for yourself.

    I know what you're trying to accomplish. I always recommend to my customers that have basement returns, to run their fans continuously to move cooler air from the basement thru out the whole house.

    But, their basements are dry due to the fact that they have mechanical cooling to begin with, and they have the CFM capacity moving thru all the ducts, since the ducts were properly size for every room.

    I'm not trying to discourage your idea, I'm only pointing out a few tips.
    Thank you for reading, and have a nice day

  13. #13
    Join Date
    Aug 2006
    Location
    NY
    Posts
    230
    Quote Originally Posted by pstu View Post
    I think the biggest weakness of this plan is a low amount of BTUs available from the basement for heating or cooling. My amateur opinion is that is even more of a problem than duct losses or fan CFM, but nobody I know has approached this idea using measurement of heat/cool available.

    If you insist on trying this, you might consider a fan from Fantech. Look for a CFM vs. static pressure table, with decent CFM at 0.2-0.4 inch (water column) static. You will find some good numbers with Fantech and some other non-cheap brands. Panasonic makes some inline fans which meet this goal too.

    Is your air quality in the basement good enough that you want to supply that air throughout the living area?

    I have myself had some original thoughts about conserving AC usage, but usually when I get enough info from professional sources on the subject, I see some fatal flaw in my invention. Better to either research thoroughly first, or slap together a 1st trial version and be ready to scrap the idea if it disappoints (or re-do it). Best of luck if you try this.

    Hope this helps -- Pstu
    pstu,

    I agree with your post 100%
    Thank you for reading, and have a nice day

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