courtyard climate

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    Michael Ermann

    Courtyards ARE a good fit in hot arid climates. You are correct that air movement (cross ventilation) is not beneficial in those climates. Let's go backward for a minute, then we'll come back to courtyards. . . 

    In hot-HUMID climates, air movement helps sweat evaporate from the skin, and evaporation makes everything around it cool so evaporation of sweat is a good thing. In those climates, because the air is already saturated with moisture, evaporation is stymied. The "sponge" that is the atmosphere is already full of water and doesn't want to take any more water in from your skin. Air movement helps overcome the problems with evaporation in humid climates (think of a fan placed to more rapidly dry a wet floor). To promote air movement, we want large apertures on the windward and leeward sides of the building and we want to separate adjacent buildings by a distance at least equal to seven times the buildings' heights. That way, your building doesn't block the breezes available to my building.

    In hot-ARID climates, we have no problems sweating evaporating because the atmospheric "sponge" is dry, and happy to take more moisture from our skin. Our sweat evaporates easily in dry climates, which is why 94 degrees feels cooler in Los Angeles than it does in New Orleans. We actually sweat more in dry climates than humid ones. . . only in humid climates, the sweat STAYS on our skin. We don't need air movement to promote evaporation in dry climates, so we don't need large openings; large openings only bring in hot air, which will increase the temperature inside our building. To your original question courtyards are beneficial in hot-ARID climates because they position the other half of the building, on the other side of the courtyard, close to our half of the building. This blocks the breezes because typically, the distance across a courtyard is far far less than seven times the height of the building. It also helps with shading because the courtyards are typically small relative to the building mass, so the other half of the building shades my half of the building. Shading is important in warm humid climates and very important in warm arid climates.

    Below is an excerpt from my Amber Book Panic Notes, summarizing thermal approaches to different climates.

    Hot-arid climate: use thermal mass, shade, small windows, thick walls, water features, courtyards, low-e windows, the bottom of a valley and the south of a pond are the best locations to build.

    Hot-humid climate: use large openings for breezes, long east-west dimension, orientation to breezes, tall ceilings, ceiling fans, sprawling building form, the top of a hill and the south of a pond are the best locations to build. Vapor control layer on outside (warm side) of insulation

    Temperate climate: use long east-west dimension, insulation, south-facing windows, buffers for winter winds, minimize north face of the building and maximize south face of the building, plant deciduous trees on the south side of the building, ¾ of the way up a hill is the best location to build. Where to put the vapor control layer in temperate climates? That's a super-complicated topic for a future blog post.

    Cold climate: compact building form to minimize heat loss (with a little longer in the E-W dimension), insulation, low-u-value windows, air-tightness, plant evergreen trees on the windy side of the building as buffer, ¼ of the way up a hill and the north side of a pond are the best sites to build on. Vapor control layer on the inside (warm side) of the insulation.

    **of course, much of this assumes that the building is not air-conditioned and the windows are open, which is often not true of our smaller buildings and almost always not true of our larger ones. I'm not sure why the profession, the academy, and NCARB don't point this out more often. It is a pretty significant caveat.

     

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    Yi Li

    thank you so much for the detailed explanation ! that covers the topic really well!

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    Rebecca Duncan

    This was really helpful, thanks! Now I have a logic for why evaporative cooling is good in hot-arid climates and not hot-humid. By adding a pool in that courtyard, you get evaporative cooling, which helps to introduce moisture into the inside air. You wouldn't want any more moisture in the air in a hot-humid climate. Instead of capturing natural winds for cross-ventilation as you would in a hot-humid climate, you capture the cooled air from the courtyard.

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