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Design for Passive Solar Orientation
In Austin we have long, hot summers and mild winters. Humidity holds heat in the atmosphere, preventing temperature drops after the sun goes down. So evenings do not cool down as they do in dryer climates. During warm months (70% of the year), air conditioning is needed for comfort. A large part of green building in Austin is focused on keeping solar heat outside.
Passive solar home design for Austin works with the natural orientation of the sun. Control and use of solar heat is the guiding principal. This means facing the broad side of the house to the north or south, to avoid solar heat gain when the late afternoon sun moves low in the west horizon. Deep overhangs and structural awnings over windows help to shield glass areas from direct sun. Ideally, the garage will be on the west side.
During cool weather, cross ventilation can be used to cool down the house without the use of AC. Breezes in Austin come from the south, so windows on the north and south sides are most effective in bringing air through. Lower inflow windows and higher outflow windows keeps air naturally moving through the house, since hot air rises.
During cold months (about 30% of the year), solar heat should be allowed to come into the home.
Use Double Pane-Low E Glass
Double paned windows with Low E glass are now required on new windows and glass doors. The metal oxide coating on Low e (emissive) glass helps to keep heat out.
Adding solar screens on west facing windows and trees for natural screening and shade improve on the cooling efficiency of the home. Skylights should be avoided because they allow too much heat gain.
Cool Down Attic Spaces
Attic spaces can accumulate tremendous heat, and transfer it to living areas below. AC ducts in the attic absorb this heat also. Attics can be cooled down by the use of vents under roof eaves and on ridge peaks. As heated air naturally rises, a moving flow of air will ventilate and cool the attic.
Reflective heat barriers under shingles help to reduce heat gain. And, lighter colored roof materials absorb less heat. On the attic floor, high levels of insulation are crucial for comfortable and efficient use of air conditioning inside the home.
Properly Size AC Systems
The AC system removes humidity from the air as it works to cool down the temperature. An oversized system will cool too quickly, and leave the room clammy.
A smaller system will run long enough reach the desired temperature and, at the same time, clear the air of humidity. A smaller system lasts longer since it does not cycle on and off frequently, and costs less to purchase. Make sure the system meets the minimum standard of at least SEER-13.
Re-check Homes for Energy Efficiency
Tightly sealed homes that depend on air conditioning need ongoing maintenance to keep them working efficiently. Leaks can develop in duct work, as well as around doors, windows, exhaust vents, recessed lights, electric outlets, and attic access. Leaky ducts and worn out weather stripping can undermine homes that were originally built for energy efficiency.
Programmable thermostats help to regulate energy usage. Quality filters keep air clean. Pleated-Media Filters in AC return-air grills remove particles as small as mold spores from the air that is drawn back into the AC blower.
Austin is a warm weather city with enough humidity to need air conditioning for comfort most of the year. Passive solar design, low-e glass, cooler attics, smaller AC systems, and annual checkups are five common building and remodeling techniques for Austin's climate.
Roselind Hejl, Realtor
Coldwell Banker United,br> Austin, Texas
Phone: 512-327-0385View Profile