Stay active and beat the heat with passive cooling
With summer in full swing, we’ve put together a few design tips to help you beat the heat and save energy in both tropical and temperate climates. These techniques, drawn from first-hand experiences designing and building from our studios in Colorado and Nicaragua, will help you to stay cool throughout the hot summer months whether you live in a four-season climate or a year-round tropical one.
1. Create air movement, especially in tropical climates. A breeze moving through an indoor space enhances evaporative cooling. Air movement is created inside a structure by positioning low windows on the windward side in conjunction with high windows on the leeward side. This allows the natural breeze to enter the building and push warmer air, which rises, out of the higher windows.
2. Use temperature differentials between night and day to maintain cool interior temperatures on hot summer days. For temperate climates, well-insulated walls and roofing in combination with a high mass slab or floor that is protected from direct summer sunlight are ideal. The slab, which drops in temperature each night, will continue to cool the air throughout the day while the walls and roofing insulate the interior from hot daytime temperatures. Using the cool of the night is much easier in temperate zones such as Colorado where temperature variations are greater – summer night temperatures in Colorado can drop considerably more than night temperatures in Nicaragua. In hot and humid climates it’s important to avoid absorbing the sun’s heat during the day because night temperatures are rarely cool enough to effectively mitigate the heat gain.
3. Avoid heat gain and direct sun, especially in tropical climates. Certain building materials, such as concrete, readily absorb and store heat. To be effective, these types of materials should be integrated in your design out of direct sunlight. For walls and roofs that must be in direct sunlight, be sure to have enough insulation on the inside to avoid transferring heat to interior spaces. A shaded buffer area with vegetation and ground cover surrounding the structure will work best to maintain cool indoor spaces. The buffer will help mitigate the heat radiating from surrounding non-shaded, heat storing surfaces such as walkways, roads and parking areas.
4. Use efficient materials, green roofs, and color to buffer and reflect heat and light. Materials such as strawbale or thatch roofing, with high insulation, provide better heat protection than materials such as tiles and corrugated metal, which radiate heat from outside to inside spaces. Green roofs are a great eco-friendly way to mitigate heat radiation from roofs and provide an effective layer of mass between outside and inside. Choosing lighter reflective colors such as light grays will also help deflect sunlight, allowing less light to be transformed into heat.
5. Integrate overhangs in your design as a highly effective way to block direct light from heat retaining materials and minimize direct light indoors. It’s best to design overhangs so the sunlight is blocked before it has a chance to come through windows. In temperate climates like Colorado, where seasonal changes are accompanied by a shift in the earth’s position relative to the sun, overhangs can be used to provide both passive cooling and heating. They block out the hottest mid-day sun in the summer months when it is higher in the sky, and allow the lower winter sun to radiate its heat directly inside the house in the cooler months.
To see photos of overhangs and insulation techniques for passive cooling (and heating), take a look at our Strawbale Getaway and Scotch Pine Residence projects. Check back this fall for our follow-up post on passive heating.
Gettliffe Architecture is a Boulder, Colorado architecture firm offering green design servicesfrom straw-bale homes to eco lodges around the globe. We believe that beautiful architectural design begins with careful consideration of earth, culture and community. Working with your ideas and vision, our team of green architects brings inspiring spaces to life that are kind to the planet and a pleasure to be in.