Archive for April, 2010

Thermostat Setback – Confusion but not Fiction

Sunday, April 4th, 2010

With recent Earth Hour on March 27 and upcoming 40th Anniversary of Earth Day on April 22, 2010, Hannah, a student at Lincoln Middle School in Mount Prospect, Illinois working on a journalism project contacted us to ask about setting back thermostats and the potential energy savings. She had done much research and became confused on multiple messages from a variety of sources, and as a friend of the family, contacted us to see if we could help her understand the benefits of Thermostat Setback. As she pointed out, the Department of Energy estimates a household “can save 10% a year on … heating and cooling bills by simply turning back [the] thermostat back 10-15 degrees for eight hour setback periods.” Where the confusion came in were thermostat types and system types that she said, “it is almost like it isn’t simple and clear cut. Some sources say they do not recommend you setback your thermostat, and if they do, they recommend a temperature range of 5 degrees.” She brought up a very good question: Why?

Well, you do not need to be a Heating and Cooling expert to understand the disparity in advice. Thermostat setback is a concept that was extensively studied first in 1976. The systems typically installed in homes at the time were single fuel source (such as natural gas or fuel oil) and if had cooling, utilized straight air conditioning as opposed to heat pumps. The thermostats that controlled the on and off operation of these systems were usually mercury type manual thermostats or electromechanical thermostats that offered rudimentary setback capabilities. What this study and subsequent studies found is that for setbacks of 10-15 degrees for eight hours, a household could save 1% for every 1 degree they set back their thermostat. But the question came up: In cold weather, doesn’t the furnace have to run longer cycles to heat the space? What the studies found is that the energy savings realized by the temperate setback outpaced the energy consumed in bringing the home temperature back up to temperature. It should also be noted that what they did find at the time, that certain systems such as Electric Baseboard Heat, Radiant Floor Heat and Boilers had a slow response time in heating the space. What this means, by their very definition, the way they heat a home is by warming up objects in the room (radiant heat) and after an amount of time air will start circulating to make the room comfortable. In the case of these systems, the energy utilized to heat the space back up to comfort level actually was not cost efficient. Hence, the advice that these systems should not be setback.

But with the passage of time comes progress, and as the popularity of heat pump systems grew in the Southeast, more studies had to be done. Most heat pump systems utilize electric resistance heat as a backup heat source. The early thermostats, including the early programmable thermostats, would utilize the electric backup heat when setback of 10-15 degrees cancelling out any energy savings. However, it should be noted that the energy savings from previous studies was realized when in cooling mode and setting the thermostat up to warmer temperature during setback period. Again, another conflicting rule of thumb being introduced: Do not utilize setback in heating season but should do so in cooling season.

Today’s systems and thermostats, introduce “Smart” technology. And although the systems are many and varied (as well as the thermostats), they are equipped with computer boards and communicate with all parts of the system, doing complex math equations to control system response. These “Smart” systems overcome the problems reported in earlier studies, including whether or not electric backup heat is utilized or not. Even today’s Radiant Flooring and “Smart” Boilers eliminate some of the concerns introduced in previous studies. Advanced Programmable Thermostats have even been introduced for electric baseboard heat.

But even with today’s advanced choices, there does exist a learning curve whether it be your “Smart System’s” computer learning your home or if utilizing a setback on older systems. As the Department of Energy points out, “with a little trial and error you can still save energy while maintaining a comfortable home.” Thermostat setback is not fiction, and while not straight forward, worth spending time to learn your system and utilizing even if for four hour periods or temperature setbacks of smaller increments than 10-15 degrees. As the studies point out, because we live in a milder climate, we can realize a greater percentage than 1% for each degree than those who live in extreme cold or hot climates.

For additional information, contact us today!