Walls and Roofs can have an important effect on interior comfort conditions in both the residential and non-residential sectors. Walls and roofs come into direct contact with the exterior environmental conditions. The effect on the interior of the building can be seen in HVAC run time, interior temperatures, energy use. As an answer to these concerns, FSEC can help determine what is useful for both energy efficiency and comfort.
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Walls
Several factors can be utilized to reduce energy consumption and improve
interior comfort conditions. Light colored exterior walls can help
to reduce interior temperatures by reducing solar heat gain. In addition,
shade trees and bushes can reduce this heat gain.
The portion of the air conditioning and heating use due to gains and losses through walls in most commercial buildings is small compared to internal gains. Therefore, going to extremes on wall insulation is not usually of the highest priority. However, some minimal insulation is recommended to reduce peak loads. For buildings in very cold climates, more heavily insulated walls and windows are generally necessary. Windows are important features of walls. You may want to look at our recommendations for energy-efficient windows.
Roofs
Insulation: Insulation in the attic is important because the attic is a large source of heat gain from the roof. In addition, many buildings have their ducts located in the unconditioned attic space.
Color: Light colored roofs in such a hot and humid environment is highly recommended. Testing has revealed that a white ceramic tile or white metal roof is best. These types of roofs will last 30-40 year compared to the 15 years that is typical of asphalt shingle roofs. These white reflective roofs can lower attic temperatures by up to 25-30 degrees F. Many commercial buildings with central AC have ducts in the attic where there is a significant amount of heat gain. The white roof lowers the attic temperature greatly increasing the air distribution efficiency of the HVAC system.
Skylights are often made a part of roofs. For our recommendations regarding skylights and other roof top lighting, see http://www.fsec.ucf.edu/en/consumer/buildings/commercial/windows.htm.
Overhangs
Before the advent of air conditioning, the typical Florida "cracker" home
had large (up to 8 feet) overhangs over surrounding porches to reduce solar heat
gain through the walls and windows. With the advent of air conditioning,
contractors desired a reduction in first cost by reducing the size
of the overhangs. This is also the case with nonresidential buildings.
The effect of this has been an increase in solar heat gain and an increase
in interior temperatures and thus the need for mechanical cooling.
Though some of the added heat gain can be rejected through new high
performance multiple pane windows with low-solar-gain coatings and
tints, it is still recommended that overhangs be lengthened in order
to again reduce the solar heat on walls and windows.
Related Publications:
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University of Central Florida.
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