Heritage Restoration, Inc.

To Leave Or Not To Leave Your Thermostat Alone

“I have a programmable thermostat that changes the temperature in a 24 hour cycle.  Can you provide me with the information the heating people recommend?

Could you please elaborate?  Are programmable thermostats obsolete?”


Every building is different.  Some buildings can’t help but get cold fast so they need blasts of heat. Others keep air in and insulate well and like a steady, even heat.  Then there is everything in the middle.  Our own field-testing, trade journals, as well as various heating professionals seem to agree that heating the mass rather than the air can be more comfortable and efficient than cranking your thermostat up and down.  But what is the most efficient?


A mass can warm a space quicker than a radiator or baseboard.  When a door opens for a bit, the mass will recover the room faster than the radiator.  So if you lower your heat too low, your mass gets cold and makes the heat work harder to get it warm again.  Even if you can heat the air is quickly, the mass will be sucking heat from the air.


Several plumbing and heating professionals have suggested only moving the thermostat 2-3 degrees when you are gone for more than 24 hours.  You should set the heat at your comfort level, then turn it up when you want more.  But there are factors to consider in what is best for you, your house and your heating system, as well as methods to see if in fact you are saving money either way.

  1. Air Infiltration. Too much negates the effect of heating, too little is unhealthy.
  2. Building efficiency.   How does the heat escape?
  3. Heating system.  Delivery system, maintenance cycles, heating zones and efficiency make a big difference.
  4. Building use intervals.  When and how many people, and how often.
  5. Building construction type.  Materials and building techniques.
  6. Building age.  Can you do anything?
  7. Building exposure.  On a hill, shaded, lots of sun.


As you can see, many factors affect how a building heats up and how it holds it. But there is hope.  Take a bit of science, mix it with some experience and most importantly, read the building.

  1. Get a FULL Energy Audit.  Observe and document the building variables.
    1. Computing energy use.   The ever changing New England weather can be leveled out by using Heating Degree Days(HDD).  HDD are developed through calculating the difference between your desired interior temperature and the outdoor temperature.  It may be on your heating utility bill or you can find it on the web.   Calculate your efficiency by dividing your fuel consumption units (gallons for oil and CCF for gas) into the HDD for that period.
    2. A blower door test tells you how much air your house is losing and where.  This is critical.  An air-sealed house will perform better than an insulated house that is not air sealed.  Stopping drafts helps keep the mass warm.
    3. Insulation needs.  Insulation should always be used where it is most critical, and least impactful to the building’s health.  Blowing in insulation to areas where air and moisture are present is worse than doing nothing.  Air seal first, then insulate.  Basements do not need to be insulated if the basement is well air sealed.  Attics are the first choice.
    4. Calibrate your heating system over time.  See what is the most economical. Keep the thermostat at a constant temperature for a month.  Compute your energy use.  Compare that to the months previous when you were adjusting your thermostat. If you do not touch your thermostat and change nothing on the building, that calculation will stay the same during the heating season.  If you turn the thermostat up and down, you are now gambling that you know when and how much to turn it up and down.  So do some testing, and find out what your building’s ideal temperature and setting are.


The suggestion that all buildings are the same and turning the thermostat up and down is the most efficient do not consider all of the factors.  The reality is keep the thermostat as low as comfortable and only move up if you are cold.  Otherwise, leave it alone.



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