You work hard to manage energy costs by paying attention to the systems in your facility. However, factors beyond your control affect how much energy you use. Your challenge, then, is to maintain optimal interior conditions while acknowledging that many exterior factors, such as climate, topography and building orientation, are out of your control.
Climate conditions influence a building designer’s choice of building orientation, configuration and envelope, as well as a building’s energy requirements for heating, cooling, ventilation, and illumination.
Learn how you can use these to bring efficient solutions to your facility.
Variations in daily or seasonal temperatures, in addition to peak temperatures, affect the size and type of mechanical and electrical equipment you choose for your building. Daytime variations tend to be closely related to the topography of a building’s location. For instance, a building situated at the base of a mountain might have a wide range of temperature variations resulting from different temperature air masses moving up and down the mountainside.
Extensive temperature variations also occur in areas that have a high percentage of clear skies and sunshine. Such is the case in desert regions where, during the day, the ground heats up from the sunlight whereas, at night, this heat is lost because there are few clouds to trap the heat close to the ground.
While such wide temperature variations may require you to install larger mechanical and electrical equipment, these same variations can also afford you the opportunity to implement a heating and cooling storage system, such as active or passive solar heating, that can reduce how much energy the building consumes.
Quantity of Sunlight
Two buildings in different geographic areas experiencing similar temperatures, but different amounts of sunlight, can vary in annual energy consumption in excess of 30%, according to ENERGY STAR
Solar loads must be accurately calculated every month to determine the amount of sunlight that strikes a building at different times throughout the year. Approaches for controlling solar loads include:
- Outdoor cooling ponds
- Solar panels for heating or cooling air
- Heating water in residences
- Generating power through the use of photovoltaic cells
Upgrading glazing can also help a building meet today’s building and energy codes with U-values and solar heat gain coefficients (SHGC) set to exceed minimum standards. Exterior shading can be considered and take the form of frames that support exterior sunshades, horizontal fins or vegetated walls.
Encourage occupants to close interior blinds on warm days to reduce the level of heat uptake. You might also consider adding window films with low SHGC while ensuring high visible light transmissions.
Consider the color of outside surfaces. Dark colors should be used for absorption on north walls or roofs in cold climates, while light colors should be reserved for reflection on roofs in warm climates.
By implementing these controls, you can help your building maximize sunlight’s heating capabilities in the winter months and minimize them in the summer.
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Wind Velocity and Direction
The speed and direction of wind can affect the strategic configuration, orientation and envelope of a building, in addition to the amount of energy it consumes. Wind disturbs the film of motionless air that surrounds and insulates a building, which, in turn, increases heating and cooling loads.
Add to this the fact that wind can evaporate moisture on wet surfaces of a building, causing the surfaces to cool to below the ambient air temperature.
In the northern hemisphere, the north and west sides of buildings are exposed to the strongest winds. Buildings should have their most vulnerable areas, like entrances and glazed areas, located away from the highest winds to mitigate air leakage around windows, doors and other openings.
If an entrance is built on the north or west side of a building, it should be adequately shielded from the wind. Otherwise, low temperatures and high winds throughout the winter months could cause high infiltration, which leads to high energy consumption.
Though high winds often result in increased energy consumption, in some locations they may actually lower consumption if the wind’s natural cooling properties can be harnessed and used throughout a building.
In regions where snowfall is consistent and heavy in the wintertime, snow that accumulates on the roofs of low-rise buildings can serve as a natural insulator for buildings constructed to retain it.
Furthermore, the manner in which ground snow reflects on adjacent low buildings can potentially enhance the illumination level of a building, thus increasing the efficiency of solar collectors, as well as decreasing the need for artificial lighting.
The topography of a building’s site, including both natural and man-made features, can affect its energy consumption by diminishing or enhancing the effects of climatic influences.
For instance, the trees located around a building can lessen the intensity of sunlight or lower the velocity of wind. Additionally, if planted close enough to the building, trees can modify outdoor humidity in the immediate building area.
Building Orientation and Configuration
The direction a building faces, as well as its configuration, determine how climatic and topographic factors impact its energy consumption.
Orientation affects the power required for lighting systems by influencing the amount of ambient sunlight that may be used for indoor illumination.
Configuration affects heat gains or losses. A building with a round configuration, for example, has less surface area than other building shapes and therefore experiences less heat gain or loss than other configurations with equal floor space. A building with a square configuration has less surface area than a rectangular one and likewise experiences less heat gain or loss.
Understanding the external factors that affect interior building conditions will help you as you endeavor to develop an effective energy management program, taking into consideration the demand on building systems and the building envelope.
This article is excerpted from the BOMI International courses Energy Management and Controls, part of the SMA and SMT designation programs, and High-Performance Sustainable Building Practices, part of the High-Performance Sustainable Buildings (BOMI-HP) designation program. Sign up for these or other BOMI International classes today and begin to work toward your professional designation. More information regarding these courses and BOMI International’s education programs is available by calling 1-800-235-2664. Visit BOMI International’s website, www.bomi.org.
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