When does 71 not equal 71?


Is it just me or does 71 degrees feel vastly different in summer and in fall?  In August, I was thrilled if it was only 71 in the house without air conditioning.  And very comfortable in shorts and a t-shirt.  But now that it’s fall, 71 has me running for a fleece.  Why is that?

2 thoughts on “When does 71 not equal 71?

  1. I believe the different experience of 71 degrees air temperature within your house during the summer and fall is due to ‘passive’ radiant heat. People who live in houses with (active) radiant heat generally set the thermostat for air temperature 5 degrees colder than conventional heating systems (hot air or hot water) and experience the same comfort. That’s because the structure of their house is warmer than with a conventional system and less of a human body’s heat is radiated to a cold house structure. Is your home built on a concrete slab, like your garage floor? During the summer I conjecture that the structure of your house is warmer: walls, floors and ceiling due to being heated from outside. You can have the same inside air temperature of 71 but the structure is at a different temperature. In the fall, with your house structure colder, heat is radiated from your body to your house and you need to grab your fleece.

    Air does not hold/store much heat, (compared to water or stone) and air temperature is less important than we think. Remember how a room with sunlight can feel warm in the winter from the sun’s radiation despite a cold temperature outside.

    Josh, from north of Boston.

    1. There is a gap between our floor and the earth below, of several feet I think. I suppose if I never ventured far from the thermostat (which is on an internal wall) it might feel the same when it reads 71 in summer or winter. It’s probably that the temperature varies near the external walls according to the season. But I see what you mean about the direction of the heat radiation depending on which side of the outside air temperature we are on.

      Thanks for the explanation! I’ll think of you and smile next time it’s 71.


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