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Cost effectiveness of atrium to passively cool?

dfloyd5646 | Posted in Green Building Techniques on

I am narrowing my building plan design options for hot, humid Georgia climate. Because nature has deemed the emphasis be heavily placed on cooling here, I am hoping to obtain some ‘free’ cooling and effective daylighting through design.

Considering the cost involved with a south facing, 2 story, basement to upper floor solarium/atrium 8″ x 15″, am I barking up the wrong tree?

I recently became aware of solar chimneys, and wondered if that design (or something else) may be more cost effective?

Prevailing winds are northwest, 5-7 mph. Another factor would be allergy concerns and keeping windows closed during pollen season.

Any insights from the contributors here, would be greatly valued.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    David,
    Before homes had access to electricity or air conditioning, solar chimneys were used to develop an indoor breeze. One hundred years ago, this was a tactic used in hot climates by people who had no other way to keep cool.

    In a hot, dry region, this approach might still make sense for an off-grid home. Maybe.

    In a hot, humid region where electricity is easily available, however, the approach doesn't make much sense.

    Install an air conditioner. Minimize the area of your windows facing east, south, and west. Choose low-solar-gain glazing. Make sure that your windows are shaded. Take measures to ensure that your envelope is as airtight as possible. These details will make you much more comfortable than a solar chimney with lots of glazing.

  2. user-2310254 | | #2

    David. Are you in the mountains at a high elevation? Otherwise, why suffer during our extended cooling (and pollen) season.

    If you are building new, you can construct a well insulated and air sealed home that will greatly reduce your energy usage. See this article on "The Pretty Good House" (https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/pretty-good-house) for more guidance.

    If you want to offset your AC usage, consider installing solar voltaics to make your home Net Zero.

  3. Expert Member
    MALCOLM TAYLOR | | #3

    David,
    In our dry PNW climate where even on hot days the air cools considerably after dusk, I often incorporate a very modest version of a solar chimney into my designs. That is some low operable windows on the south side of the house and a few high clerestory ones near the ceiling.

    This works quite well here, but from what I have gleaned from posters who live in the humid south, admitting moist, colder air isn't a good idea. So, although alluring, forgoing the solar chimney and following Martin's advice is the way to go.

  4. dfloyd5646 | | #4

    Thank you for your feedback Martin, Steve and Malcolm!

    I realize now that I should have indicated that yes, I will be installing an HVAC system, but was hoping for some 'assistance' from mother nature. I am grateful for the wealth of knowledge found here and I did read all of the 'PGH' articles. (amongst many others), I am learning to restrain my enthusiasm for theoretical methods that don't function as stated in the real world. Martin, you probably saved me from capping off moldy earth tubes in the distant future.

  5. GBA Editor
    Martin Holladay | | #5

    David,
    If you are the kind of homeowner who likes to keep track of the outdoor dew point -- so you can tell the difference between days and nights when opening the windows is beneficial (because the outdoor weather is cool and dry enough to make ventilation cooling logical) and the days and nights that are so humid that it's counterproductive to open the windows -- then you might want to install a whole-house fan.

    For more information on whole-house fans, see Fans in the Attic: Do They Help or Do They Hurt?

  6. Expert Member
    Dana Dorsett | | #6

    For the cost of the solar chimney you can probably buy a mini-split heat pump and enough PV solar to run it, and get the latent cooling benefit, just as if it were a 21st century building.

    High humidity is something that needed to be tolerated before air conditioning, but it's not very healthy for either the house or for the humans. Given the high average summertime dew points in GA, it's really better to skip nighttime ventilation as a cooling strategy. That only works well on the left half of the country where average mid-summertime dew points are under 55F.

    In GA the July-August average dew points run around 70F, and don't drop to the 55F range until half past October (and on through the end of April.) The number of summer nights per DECADE where the dew points are below 55F and nighttime ventilation would be probably be fewer than 100. An investment in architectural features to enhance nighttime ventilation, or whole-house fan type equipment would be pretty much wasted, unless you can tolerate a higher than recommended (for human-health) range. It's one thing if you're off grid with parsimonious power and have little choice, but if you have enough power to run it, high efficiency AC and smart architecture to lower the solar gain (particularly the PM gain) is a better bet.

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