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Programmable Thermostats
By Ken Sheinkopf
Q: I know that you have recommended adjustable thermostats in the past, but I just read something about a study that showed they were not as effective in saving energy as people once thought. Do you know about this?
A I do. I have seen the research reports on a study completed recently by the Pacific Northwest National Laboratory that concluded that the energy savings from programmable thermostats are significantly less than what has been advertised.
The researchers looked at 150 homes in the Pacific Northwest ö 25 homes with programmable thermostats, and the rest with the conventional manual models. They used a data logger to monitor energy and temperature in each house, giving them thermostat set points and timing. As you noted, their study basically found that the value of programmable thermostats has been greatly overestimated in the past ãbecause the mere presence of the thermostat doesnât necessarily alter the homeownerâs behavior.ä It is clear that the attitude of the occupants of the home was the major factor in the operation of the thermostats.
The value of programmable thermostats is that they can be set to reflect the lifestyles of the occupants of the home. The thermostat can be adjusted to raise or lower the temperature when the occupants go to sleep, when they leave the homes for the day, when they are on vacation or away on weekends, etc. While any homeowner can do this manually, the programmable thermostat can be set so that the timetable is followed exactly as desired. The thermostat never forgets, never goes on vacation, and never takes a day off from its work.
However, this study found that people used the thermostats in widely varying ways. Some homeowners adjusted the thermostats carefully to move the settings several times every day. Some didnât make any adjustments at all. In many cases, even though the thermostats can be pre-set and then left alone, homeowners kept adjusting them frequently. The results showed that people with adjustable thermostats basically followed the same manual adjustments made by people with conventional thermostats.
So do I change my views on the value of these products? Nope. I still think they can be a great tool for saving energy, assuming the homeowner follows the directions, makes the settings and leaves the machine to do its work. The potential for significant savings is there if the product is used properly.
Energy Tip: Plant tall trees around
your house to provide shade in hot weather. Keeping the walls
and roof cool will help lower energy bills during the air-conditioning
season.
Bibliography:
Note: Ken Sheinkopf is Associate Director of the Florida Solar Energy Center. Write to him at 1679 Clearlake Road, Cocoa, FL 32922, or e-mail Sheinkopf@fsec.ucf.edu
Photo credit: NREL photo library
NREL efficient home
PIX number: 08417
This low-energy home built by Tierra Concrete Homes of Pueblo, CO, participated in NREL's Exemplary Buildings Program and High-Performance Buildings Research Project and
uses about half of the energy of a typical new home built in the Pueblo area. The home features large, south-facing windows and is made from concrete forms, which is a high-mass material. The mass acts to absorb the solar energy during the winter, which lowers heating bills. It also helps keep the temperature constant during the cooling season, so much so that air conditioning is not required. As a result, this low-energy home costs only slightly more, about 10% more, to build than a conventional home.
Credit: Stone, Dwight
Publications: CADDET newsletter (December 1999)
Date: 11/1/1999
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