Baby, it’s cold outside, and you need to save money on your heating bill. But hang on before you lower that thermostat too much.

A few years ago, researchers at Cornell University found that when employers lowered office temps from a toasty 77 degrees to a chilly 68 degrees, they also lowered worker productivity.

It seems being too chilly puts the brain in a deep freeze. A very deep freeze. Mistakes among the test subjects increased 74 percent and group output decreased 46 percent when workers were chilled to the bone. So you need to weigh the amount you’ll save lowering the thermostat against what you’ll lose in alertness and effectiveness.

Rather than going for the igloo effect, try lowering the thermostat to 70 or 71 degrees. You’ll cut back on your heating bill without paying more in other ways.