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  1. #1
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    Default split level house is freezing upstairs in summer

    Have a split level house and second floor is freezing in summer and cold air can,t get down on first floor because staircase is too narrow?

    I have a huge fujitsu split ceilling unit installed and deflector are throwing air in direction of bedrooms.

    Anyway to force air on first floor?

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  2. #2
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    Default Re: split level house is freezing upstairs in summer

    Cold air is heavy, it will naturally go down the stair case, however if the stair case is narrow you may want to try a floor fan at the top of the stair case and blow the air down the stairs.

    Once the air is at the first floor it will likely stay down to towards the floor and the hot air will most likely stratify at the ceiling level given hot air is less dense and buoyant.


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    Default Re: split level house is freezing upstairs in summer

    Quote Originally Posted by Raymond Wand View Post
    Cold air is heavy, it will naturally go down the stair case, however if the stair case is narrow you may want to try a floor fan at the top of the stair case and blow the air down the stairs.

    Once the air is at the first floor it will likely stay down to towards the floor and the hot air will most likely stratify at the ceiling level given hot air is less dense and buoyant.
    That's not how it works.

    The real problem is the stack effect and the solution is to seal and insulate your attic better. This will stop the warm air from being drawn up into the attic and out of the dwelling, being replaced by colder air being drawn into the structure on the first floor.


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    Default Re: split level house is freezing upstairs in summer

    I think this is how it works, or at least authoritative sources say.

    Stack affect 3.3.1
    https://docs.google.com/viewer?a=v&q...C7miIbCHBG-tXg

    Summertime Stack Effect 3.2
    http://www.civil.uwaterloo.ca/beg/Do...%20Control.pdf

    The stack is reversed in the summertime. Cold air is heavy, it can't sink down the stairway because its meeting a warm light air trying to come up.

    Sure there may be some air leakage occurring but a lot depends on other factors, such as insulation levels, age of house, ventilation systems, heating type, ventilation type, basement, humidity levels, sunning of house...


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    Default Re: split level house is freezing upstairs in summer

    Quote Originally Posted by Raymond Wand View Post
    Sure there may be some air leakage occurring but a lot depends on other factors, such as insulation levels, age of house, ventilation systems, heating type, ventilation type, basement, humidity levels, sunning of house...
    In both the summer and the winter the remedy is better insulation and sealing in the attic (and the whole house, if possible). The goal is to reduce the pressure differentials that induce the stack effect.

    And to be clear, it's not a question of the cold air not sinking down the stairs - when I said "that's not how it works" that's what I was referring to. A house is too small a system to induce temperature and humidity gradients large enough that air masses will move past each other. What happens instead is that the air moves generally in through the bottom and up and out through the top. If the stack effect were "reversed in the summer" as you suggest, it means air would be drawn in through the top and escape out the bottom. But if that were the case, the OP would not have asked the question as the conditioned air would already be drawn downstairs.

    Instead what happens is the solar heat gain through the walls causes a pressure gradient that induces the warm air to move up and through the attic. Localized cool air on the second floor is drawn up with it (while the temperature gradient is more or less equalized through mixing). Any air infiltration is likely to be warm air, therefore we're not aware of how the air currents are moving.

    Installing a fan to circulate the cool air down the stairs will do that, but it won't have any effect on the amount of cooling wasted as it escapes through the attic. Air sealing and insulation will help reduce the solar heat gain and convection, making any cooling system more efficient and reducing the amount of directional convection up and out of the structure.


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    Default Re: split level house is freezing upstairs in summer

    Leaving the AC out of the equation and any other factor such as mechanical ventilation et ceteras, the article states the reverse stack affect occurs in the summer.
    You opined,
    What happens instead is that the air moves generally in through the bottom and up and out through the top.
    However the article states,

    In warm climates and during warm weather, stack effect reverses and air is often drawn in at the top and pushed out at the bottom. Infiltration of warm moist air in warm weather can cause many problems as exfiltration of warm moist air in the winter.

    I agree as does the article state that improvements with air barrier systems and sealing go along way in reducing stack affect. Insulation is another factor but not predominant in the article.

    More information is required of the OP in order to determine other than a slide split, the age the insulation levels, and heating means, et ceteras.

    The question of the original poster was how to get the cold air down the stairs.
    Since he did not mention how the house is heated, no air circulation is going to create temperature difference between the top and basement as well as humidity.

    If there is no circulation other than the fan in the split then relying on the stack affect to move the air is not going to be a quick fix in cooling the lower areas of the house.


  7. #7
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    Default Re: split level house is freezing upstairs in summer

    Turn the thermostat up (warmer set point temp.).


  8. #8
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    Default Re: split level house is freezing upstairs in summer

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Turn the thermostat up (warmer set point temp.).
    That was my thought too.

    Pascal,

    Where is the thermostat/where are the thermostats? One a/c system or two a/c systems?

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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