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  1. #27
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Ultimately, the best approach to the widespread problem of temperature imbalance between floors of a multi-story house is to thermally and hermetically isolate the attic from the house interior as much as possible. Doing so will minimize the following drivers behind the temperature imbalance:

    Summer: reverse stack effect, where sinking air caused by cooling it draws hot, humid outdoor air from the attic through multiple ceiling penetrations

    Winter: stack effect, where rising air caused by heating it (and escaping into the attic through the same multiple ceiling penetrations) draws in cold, dry outdoor air through multiple penetrations/gaps/holes in the lower floor walls, windows, and etc.

    If the envelope can't or won't be fixed, the only alternative is to improve the design of the HVAC to compensate for a crappy envelope design. If we insist on staying mired in the 20th century, when fossil fuel energy was cheap and abundant, with our thinking on how residential building envelopes should be built and perform, we're facing a potential situation where many homes may become unfeasable for their owners to remain comfortable year round, as energy costs continue climbing over time.

    21st century approaches to residential structures should be more thoughtful design efforts toward the envelope AND the HVAC. But alas, we're mired in a "get 'r dun" culture, and until that changes we will continue seeing monumental stupidity in how we build and control residential building environments.
    • 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.

  2. #28
    Join Date
    May 2004
    Posts
    595
    Quote Originally Posted by Shophound View Post
    Ultimately, the best approach to the widespread problem of temperature imbalance between floors of a multi-story house is to thermally and hermetically isolate the attic from the house interior as much as possible. Doing so will minimize the following drivers behind the temperature imbalance:

    Summer: reverse stack effect, where sinking air caused by cooling it draws hot, humid outdoor air from the attic through multiple ceiling penetrations

    Winter: stack effect, where rising air caused by heating it (and escaping into the attic through the same multiple ceiling penetrations) draws in cold, dry outdoor air through multiple penetrations/gaps/holes in the lower floor walls, windows, and etc.

    If the envelope can't or won't be fixed, the only alternative is to improve the design of the HVAC to compensate for a crappy envelope design. If we insist on staying mired in the 20th century, when fossil fuel energy was cheap and abundant, with our thinking on how residential building envelopes should be built and perform, we're facing a potential situation where many homes may become unfeasable for their owners to remain comfortable year round, as energy costs continue climbing over time.

    21st century approaches to residential structures should be more thoughtful design efforts toward the envelope AND the HVAC. But alas, we're mired in a "get 'r dun" culture, and until that changes we will continue seeing monumental stupidity in how we build and control residential building environments.
    How are your testing the envelope? Or better yet, how are you finding the leaks.
    I know you can use a duct blower to pressurize a house and then use smoke on the outside looking for where its leaking out. Which worked back when windows and doors were the #1 issue. Now with low e-windows and companies that install them have plug that leak. I'm very much would like to learn more about what others are doing with envelope testing. I think we have some good info going here.
    Were are you finding leaks when you exclude windows and doors.
    Thanks

  3. #29
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    The best solutions are proper sizing and/or zoning and either automative zones or manual summer/winter dampers. It would also help if homes had cool roofs, were tighter, and had enough upstairs shading and mass to minimize stack effects and reduce diversity between seasons.

    It is possible to build homes than have minimal convection, low diversity, and good insulation values and low solar gain and tight construction and still have lots of naturla light without tons of foam, High dollar triple pane windows, or special construciton methods like SIPS, ICF, etc. Those are great alternatives, but these homes wer ebeing built in the 1920's, 30's 40's and 50's. It wasn;t until tract home and centrla air became popular that we walked away from better construction methods and focused on cost , features and size.

    Sealing the attic and iwndows has probably the best impact from my limited experience so far. DO NOT ASSUME that you brand new, fancy triple pane low-e windows are sealed all that well. IF you use them very much, the seals can start to wear after only a couple years. Actually I'll bet after opening and closing them more tha na dozen times, you air leakage jumps rapidly.

  4. #30
    Join Date
    Feb 2012
    Location
    central Florida
    Posts
    154
    I Lived in an apartment with same issue. I closed the downstairs vent and left upstairs vent open. This did not resolve the underlying problem,from a technical repair standpoint. It did however solve the problem (which was the same as you described).I believe that r290 is correct it is most likely a duct issue. This is a problem in most every home I have seen down here(bad duct design or install)

  5. #31
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Quote Originally Posted by r-290 View Post
    How are your testing the envelope? Or better yet, how are you finding the leaks.
    I know you can use a duct blower to pressurize a house and then use smoke on the outside looking for where its leaking out. Which worked back when windows and doors were the #1 issue. Now with low e-windows and companies that install them have plug that leak. I'm very much would like to learn more about what others are doing with envelope testing. I think we have some good info going here.
    Were are you finding leaks when you exclude windows and doors.
    Thanks
    Several pro members here do envelope testing for a living. Tipsrfine, energyrater la, Tedd Kidd, etc. All of them are familiar with blower door testing, infrared cameras, duct blasters, etc.

    When you exclude windows and door leakage, you are then focusing on structural leakage via penetrations through what's known as the structure's "pressure boundaries". A pressure boundary is defined as a border between conditioned air and outdoor air. The ceiling directly below a ventilated attic is a pressure boundary. If you poke a can light through that ceiling and into the attic, and do not seal it, you have compromised the pressure boundary at this location.

    Personally I've had a lot of success in reducing overall building leakage by concentrating my efforts on the ceiling beneath attic pressure boundary. If you make it harder for air to escape into the attic via stack effect, or push into the house from the attic via reverse stack effect, the forces that determine the rate of overall building leakage are reduced.
    • 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.

  6. #32
    Join Date
    May 2013
    Location
    Houston, Tx
    Posts
    17
    Simple and cost effective..... make two zones ,one up one down. Honeywell offers some nice solutions i have used.

  7. #33
    Join Date
    May 2004
    Posts
    595
    Thanks, working a change out job and since next year whole house leak testing will be mandatory. Need to start figure out easy ways to find and plug the big holes. I don't have a metered fan, so its hard to quantify the amount of the fix. But can use a box fan to find some of the easy leaks.

    One issue is attics have insulation that hides a lot of those penetrations. I was at a house that was flipped and the attic was 2' deep in insulation. Bet you 100 to 1 they did not seal any openings. I feel lucky if they don't cover up the eve vents. It's a $1.00 sq foot to suck out the old stuff, that's when the sealing needs to take place.

    The house with the change out is a "fancy" home with lots of different ceiling heights, some even vaulted so forget even doing anything there.
    I think I will just concentrate on the Plumbing vent/s, Chimney penetration, registers and attic access. Most attics here are very low in height and you can't even get with in 8' of the eve. But see a lot of wires going down the walls.

    Back to the question at hand, post up the size of the system and the size of the return duct/s

  8. #34
    Join Date
    Jul 2007
    Location
    Delaware
    Posts
    3,824
    Quote Originally Posted by Bobe5531 View Post
    Can you guys give me a bit more insight on trouble shooting a system when customer complaint is 1st floor cools well but 2nd floor is hot during cooling season.
    Thanks,
    Bob
    More info would be required. You the OP have made two posts, we have made 30. It's just running on with no actual solution.

  9. #35
    Join Date
    Jun 2013
    Location
    Cleveland Ohio
    Posts
    30
    Quote Originally Posted by n-e-w Jerz! View Post
    Easiest solution: cut first floor dampers down to force more air to second floor(air takes the path of least resistance). Better solution: Arzel zone system.
    Even with a properly designed system there's only one thermostat for the whole house , it only knows what the temperature is in "that" room , combined with load shift , the sun beating down on the east side in the am , the second floor all afternoon and the west side in the pm , different loads moving around and not evenly spread throughout the entire space . This combined with all the other things mentioned here like insulation , stratification of air , etc.... and you can certainly have an uncomfortable 2nd floor , and yes , one good way to combat this is with zoning .

  10. #36
    Join Date
    Feb 2007
    Location
    Central NJ
    Posts
    533
    Quote Originally Posted by ZoneRider View Post
    Even with a properly designed system there's only one thermostat for the whole house , it only knows what the temperature is in "that" room , combined with load shift , the sun beating down on the east side in the am , the second floor all afternoon and the west side in the pm , different loads moving around and not evenly spread throughout the entire space . This combined with all the other things mentioned here like insulation , stratification of air , etc.... and you can certainly have an uncomfortable 2nd floor , and yes , one good way to combat this is with zoning .
    Good point

  11. #37
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    802
    I'm a big fan of a sealed (foam at deck) attic.

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