We are all aware of the importance of conserving energy and natural resources, due to their growing scarcity, rising costs and the potential for permanent environmental harm to our world. Many people are surprised to discover that buildings are responsible for 40% of energy use in the U.S.—more than industry or transportation. That’s just for operating buildings; the number jumps to 50% when we count construction. In fact, buildings account for 68% of electricity used, half our greenhouse gas emissions, 40% of our raw materials, and 30% of our waste output—136 million tons per year. And residences count for over half of building energy expenditures. So what should the home- or small business owner consider when remodeling or building? It turns out that designing with climate can lead to better-performing buildings that are more comfortable and economical to operate, and even beautiful, without necessarily greatly affecting construction costs. This requires a sensitivity to the site and an awareness of building science, but especially calls for a systems approach that takes into consideration the synergies of individual building components, the context of place, and the needs and desires of the owner.
Siting and Orientation
Critical factors—and in a neighborhood some of the most challenging to control—are siting and orientation. In Austin cooling is a significant concern for much of the year. Align the building’s longer axis east-west to minimize intense sun exposure; southern exposure is easy to control and most of the time northern exposure is not a problem. If a lot’s orientation does not cooperate, strategic landscaping of deciduous trees can provide relief. Carefully consider window and glazed door placement not just for viewing, privacy, and egress, but to reduce or eliminate direct solar gain in hot seasons. South-facing glass can be shaded from the high summer sun with an overhang; the low winter sun can still penetrate into the space and warm it. Shade east and west windows with vertically oriented elements, to block morning and late afternoon sun low in the sky. North glass needs vertical shading from early- and late-day summer sun.
Passive Heating and Cooling
In addition, consider other passive measures to help warm or cool the building. I’ve already mentioned southern winter sun; such passive heating is more effective if the interior space has thermal mass, by including exposed concrete, stone, or brick in the sun-warmed space. For cooling, given Austin’s humidity, ample ventilation is appropriate for much of the year. Situate windows and doors to capture prevailing breezes; thermal chimneys can take advantage of warming air’s natural tendency to rise to create vertical ventilation.
Smaller buildings’ energy performance is highly susceptible to the effects of climate. Designing the building envelope—roof, walls, and foundation perimeter—appropriately for their climate is crucial for residences and small commercial buildings. For Austin’s climate, light-colored and/or metal roofs reflect summer heat. Incorporating radiant barriers in the roof design can help performance considerably, but the radiant barrier must have an adjacent airspace to be effective, so don’t let the insulation come in direct contact with it.
Recent remodels and construction are better insulated, thanks to advances in materials and more stringent building energy codes. But the location of insulation is important, not just how much you have. For a cooler attic, place insulation on the underside of the slope of the roof, instead of down among the ceiling joists. While this keeps your storage area more comfortable, most importantly your air conditioning ducts won’t be in a super-heated attic. And as buildings get tighter and tighter, make sure you consider a dedicated outside air intake for your new HVAC system, preferably with a waste heat-shedding air-to-air heat exchanger.
Designing with climate can add little or nothing to construction costs, as it is primarily concerned with the appropriate configuration and placement of building elements. When additional costs are incurred—better insulation or more efficient heating and cooling equipment—the payback period is short. The end result will be greater comfort, lower operating costs, and even perhaps a more beautiful and satisfying building.