The Effect of Building Orientation on HVAC System

Function

• The position of a home in relationship to the sun, wind direction and surrounding trees affects the HVAC system. Houses in optimal orientation for the prevailing climate can reduce homeowners’ heating and cooling costs. For example, smaller heating and air conditioning units that consume less energy can be installed in homes positioned to absorb the most heat from the sun in winter and maximize exposure to cool breezes in summer.

Ideal Orientation

• A house is in an ideal position when the longest part of its foundation lies in an east-west orientation, according to the California Energy Commission. That orientation can reduce demands on a heating system. It generally causes a home’s longest wall to face south to absorb the most heat in winter, when the sun sits low in the sky. An overhang above the same south-facing wall would shade the house from heat in summer, and cut cooling costs, when the sun sits high in the sky.

Landscaping

• A building's proximity to specific types of trees also affects its energy demands. The Arbor Day Foundation recommends positioning large, deciduous trees on the east, west and northwest sides of a house. Deciduous trees shade a home in the summer, but their loss of leaves in the fall allows a home to absorb the sun's heat during colder months. Air conditioning costs can drop 35 percent when a home is in proper orientation with trees, according to the Arbor Day Foundation. Heating costs can fall 30 percent when a row of pine, spruce or fir trees block winter winds on the north and northwest sides of a house.

Considerations

• The effect of a home's orientation on an HVAC system is impacted by local climate differences. The California Energy Commission notes that Sacramento's climate is significantly different from San Francisco's climate, but the cities are just 100 miles apart. Therefore, you may need to consult with a builder who specializes in solar and wind energy if you want to determine the best orientation for a new home. Nonetheless, the commission indicates the total energy use at U.S. homes could drop 30 to 40 percent by positioning homes to rely more on the sun and wind for heating and cooling needs.