155) A Myth: Turn down heat at night

by Gail on December 12, 2011

Heat pump

In a previous post I reported on a green building forum presented by the Sunshine Coast Regional District.

I didn’t tell you one of the most important things I learned from Murray Frank, the speaker from Constructive Home Solutions.

He told a story of his British father-in-law, whose lifelong habit was to turn down the heat every night, to save energy. After his home heating system was updated to an air-to-air heat exchanger (or heat pump), he continued to turn down the heat each night before going to bed. His son-in-law advised him not to turn it down, but he continued to do so, while steadfastly denying that he was. When s-i-l saw him turning it down, he devised a plan. He installed a fake thermostat in place of the thermostat f-i-l adjusted each night. Then, he installed the functioning thermostat in a hidden location, set it to f-i-l’s daytime temperature. F-i-l continued to turn down the fake, but reported to s-i-l that the system was finally fixed, because his heating bills were considerably lower!

What gives?

Well, the heat pump works on the differential between the air inside and the air outside. If the thermostat needs to jump 2 or 3 degrees suddenly in the morning the (necessary) back up heating system (a furnace) jumps in to get it to the higher temperature quickly.

The furnace - back up heating system

Last winter, I observed the “auxiliary heat on” notation on the thermostat every morning, and was frustrated because the outside temperature wasn’t very cold. Wasn’t our heat pump working as promised?

Now that we’re not turning down the thermostat every night, the heat pump doesn’t have to raise the inside temperature suddenly, and our heating bills have gone down. (An aside: Since last winter, we have installed a simple electric heater with a blower fan in the studio, so there are additional electrical demands, too. Our heating bills should be higher, not lower.)

So, I conclude that turning down the heat at night doesn’t save energy. Take that to the bank.

At least, if you have a heat pump!

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