Constructing facades for different climates

For a building to have a facade that maximizes energy efficiency while providing a comfortable environment for its occupants, each facade may be designed in a way that is best suitable based on the climate. In the United States, these climates are divided into zones and are generally described as either hot, cold, or mixed. The sun's seasonal movements, such as midday sunlight hitting a low angle during winter and a high angle during summer, are some factors that should be taken into consideration when designing a building's facade.

Hot Climates

Buildings in hot climates need protection from the sun, provide shade, and oriented to reduce solar heat gain. To do this, external shading devices such as overhangs or vertical exterior louvers may be used on all four sides of a building to keep the heat and energy from being absorbed into the building and thereby helping to keep the building cool. A high-performance curtain wall, which is available from a manufacturer or customized, may also be used to reduce solar heat gain and allow daylight into a building while decreasing its impact on the cooling load. Facades may be designed to exclude most sunlight and instead make use of reflected light to reduce energy consumption. Moreover, ventilated, or double-skin facades, allow air to flow by natural or mechanical ventilation and also have sun-shading properties.

Cold Climates
Buildings in cold regions should minimize east and west sun exposure while maximizing sun exposure from the north and south. Facades may be designed with a higher window-to-wall ratio to increase heating loads. In cold climates, the window-to-wall ratio on the south facing side of a building should be maximized to allow sufficient daylight in and to absorb the sun's heat energy to warm a building during the winter. Selecting the right amount of glazing on windows, which adds solar heat, keeps a building well insulated, allows natural daylight into a space, and can help to keep the overall facade insulating value as low as possible to slow the transfer of heat during winter. Although north-facing windows may not be hit with direct sunlight, high solar gain glazing is important because these windows can gain heat from reflected and ambient light. It is important to know which building facade will be most affected by strong winter winds, windblown and sliding ice, the direction rain storms will impact the building most frequently, and where hazardous ice and snow accumulations are most likely to form on the facade to reduce the risk or falling ice and snow.

Mixed climates
The main concern in mixed climate zones is having a balance between exposure to the sun and access to daylight. Facades should be able to keep heat out of the building, except during mild winters when you want solar heat gain and warmth inside. The east and west facades need stronger sun control, especially in the morning, and may be designed with high-performance windows that allow natural ventilation and an external shading system like an aluminum rain screen, awnings, shutters, or vertical sunshades. To block the midday sun, the south facade may have a glazed curtain wall, tinted glass windows, and horizontal shading devices. The north facades, which hardly need shading because during the summer the sun only hits this side early in the morning or late in the afternoon, should have smaller windows with high thermal resistance for better insulation and high solar gain glazing.

What are other important factors for facades in different climates?