How to set thermostat in a two story house in summer

Temperatures Upstairs and Downstairs

Here at D-N-D Services, we are often asked how to set thermostats in a two story home. For two story homeshow to set thermostats for two story home balancing the air temperature is a little more complicated than in a single story home. Almost everyone knows heat rises and cold air falls. This is called thermal convection and can cause comfort issues when setting up thermostats upstairs and downstairs. We often see homeowners set upstairs and downstairs thermostats to the same temperature. Sounds right, but is usually wrong. For example, in the summer, if both thermostats are set to 74 degrees, the upstairs unit usually does most of the work and runs most of the time. The reason is the conditioned air settles to the lowest point..the first floor.

When the first floor is set to the same temp..the first floor tends to stay below the setpoint from the cold air falling,which in turn will cause less conditioned, clean air in the downstairs. The heat from both floors rises to the second floor, thus the upstairs air conditioning unit will run almost constantly. The opposite effect happens in the winter time.

Improperly Set Thermostats Cost More

House with two air conditioners are supposed to work together and maintain comfort inside the entire home. When the thermostats are set where they do not complement each other, you will not only have poorer air quality and uncomfortable areas, but it can cost more, as one system is carrying more of the load.

How To Properly Set Thermostats For A Two Story

A simple solution , and the first place to start is set your thermostats up allowing for thermal convection. Two degrees is the standard.

This means if you prefer the temperature to be 72 degrees in the summer,set your downstairs thermostat to 71 degrees, and set the upstairs to 73 degrees. This will work in the winter also. Just remember you want the upstairs thermostat to be set two degrees higher than the downstairs. Dont forget if you are using programmable thermostats to change the programming in each to match the two degree differential.

Other Temperature Balancing Considerations

If you set your thermostats as described by DND Services , you should notice increased comfort in your home.  Some other considerations that can affect your comfort and energy usage are, type of insulation, duct system including the return air which in many cases is undersized, and  properly sized equipment along with the efficiency of the system. Today’s high efficiency systems such as the Carrier Infinity are designed two maintain comfort while reducing energy usage.

If changing your thermostat settings does not help you can always change them back. We want your air to be clean,comfortable, and energy efficient.
If the need arises contact D-N-D Services for any of your air quality and comfort issues.

 

Comments

  1. Thanks for the tip dnd services.
    Our two story home in rockwall is much more comfortable in heating and air conditioning by setting our thermostats by your recommendations.

  2. Thanks Amy. DND Services has been a BBB Accredited Business since 07/05/2007 because we have a genuine concern for heating and air conditioning repair and comfort solutions.
    Feel free to call D-N-D Services at 972-771-9898 for any furnace or air conditioning repairs or concerns.

    We also work with Complete Home Energy Services(CHES) that specializes in home comfort.
    https://www.facebook.com/pages/Complete-Home-Energy-Services/459286857544510

  3. Anonymous says:

    We had two units of ac replace our single unit for my two stories house. But they install two thermostats at the same place next to the return van on the 2nd floor open hallway. No matter what temperature we set, the downstairs will be always lower and both units seen always on. We complained to the installer that the thermostat should not be at the same place, they should be at two different floor. One should be the 1st floor and the other one should be inside the master bed room since they are suppose to cool the all the bed rooms. Themostat at the hallway won’t sense how the bed room temperature especially people closed their door when sleeping . Does it make sense to you guys?

    Thanks,
    CW

    • You have a good point. While it is a good idea to put the thermostat near the return air vent, it should be near the return air vent for the area it is servicing.
      In addition, while putting a thermostat in the ,master bedroom is a good idea, there is a big possibility of different room temperatures even if the bedrooms have their own returns. Zoning is a possibility. Zoning is where you have a main thermostat, and up to 3 more smart controllers with dampers and a zoning control board that will monitor temperatures and airflow in the different areas as needed.
      You can read more about using two thermostats in a two story home here

  4. My upstairs is very hot. It is set at 78 but is actually 85. The motor outside kicks on sometimes. I’m very concerned about the cost of whatever the problem is. Would it be feasible to just use the downstairs AC as we rarely ever go upstairs (bonus room)?

  5. Will it be more efficient to turn off 2nd floor thermostat and only have 1st floor thermostat since master bedroom is in first floor?
    Or is it more efficient to have both on at same temperature setting?

  6. But my question is at night. should I leave the downstairs unit 2 degrees below at night too ?. we like to keep the downstairs 82 during the day and 84 in the upstairs when at work. when at home we lower the downstairs to 78. At night we like upstairs at 72-73 and usually just put downstairs 82. We had the capacitor of the upstairs blow up. the Hvac guy said we need to keep both unit on for higher efficiency and lengthen the life of the unit. then Should we keep the downstairs at 70 at night ?

    • The goal is comfort..keep the area you are in at night, to the temp you desire and then it gets more complicated( you liking temperatures at certain degrees doesn’t give me much to go on..
      Especially since your day and night temperature swings do not jive(correalate).

      Capacitor has nothing to do with the temperatures of your home.

      Lucky for you, “the hvac guy”(the technician that has paid money for education and devoted his time in learning how to make people and spaces comfortable) was correct in telling you to keep both units on. I find many instances where this is not true. Good news to hear you found a technician with the knowledge.

  7. Stacy Gill says:

    Hi we live in an area that can be very hot, in the day but often can have a cooler breeze in the evening. We installed a Whole House fan, that pushes the hot air out and brings the cool air in. But sometimes we dont get this cool evening breeze. And if we are downstairs all day, is it still important to use both air conditioners. Or just the downstairs unit, until evening and then turn on the upstairs unit ??

    • It is still important to use both air conditioners.
      You can read more about using the

        downstairs unit and the upstairs unit by

      clicking here

  8. We have a bonus room upstairs which has a thermostat. We like the down stairs to be 74-75 during the day and at night 71-70. We keep the door closed upstairs as well. How should we handle our thermostat upstairs and should we leave the door open or shut? I know it’s hot but our last two bills have been crazy expensive.
    Thank

  9. I have a 2 story. I have one AC unit but two thermostat controllers. The master is downstairs. Ins the summer we burn up in the master while the rest of the house is cool. In the winter we freeze while the rest of the house is warm. The thermostats are set 2degrees apart. (71 down and 73 upstairs). Please help!!!

  10. After reading the PROPER settings, I was way off lol. I live in a 3 story home. Basement, main level, and 2nd level. The main level is set to 73 and the upstairs is set to 75 but I was burning up. Thermostat says it was 81. What do I do to just feel comfortable?

    • You have an issue that cannot be solved without a detailed diagnostic inspection of the living space by a licensed heating and air conditioning contractor.

      Ask around your peers and neighbors to find a reputable company in your area to get an honest evaluation and options.

  11. I was wondering why it is not a good idea to close certain supply vents in order to balance the temperature between upstairs and downstairs? I live in a two-story house with one thermostat (downstairs) and the upstairs is always several degrees warmer than downstairs. In order to remedy this, I thought it would make sense to close off a couple of the upstairs vents? Thanks for your input.

    • Good question. We find in air conditioning many problems are the result of poor airflow. Here is what can happen by closing off vents.
      Closing off the vents reduces the amount of air that coming off the supply side of the indoor evaporator coil.
      This means the cold air coming across the indoor evaporator coil stays in the system getting colder and colder until the system can freeze up thus further reducing airflow, thus freezing up more, and so on, until no air is allowed across the coil into the area needing to be conditioned.

      In addition, environmental air is constantly trying to come to a common temperature, including the air in your home. We use insulation to try and maintain temperatures in our home, warmer in winter and cooler in summer.
      Now, simply put, cold attracts heat. Thus, the area you closed the vents to will be warmer but, the cooler air in your home is trying to mix with it which results in the spaces you want conditioned not maintaining their temperatures as well as they could thus increasing inefficiency.

      Hope this helps.

  12. We have a 4000 sqft 2 story home with 2 master bedrooms. Parents live downstair’s and the kids are upstairs. Parents get cold easily and and the kids burn up. Is it horrible to run the heat downstairs and the ac upstairs? Two 3+ ton units.

  13. I am new to a multi system 2 story home. As I research ways to set the heat better, I am noticing some contradictions. You say set the downstairs 1 degree below target temp and upstairs 1 degree above target temp while others have it set 2 degrees below and above. Would either one work?

    Also, in the summer will I switch…higher temp downstairs and lower temp setting upstairs. Also noticing contradictions there.
    Thanks!!

    • As far as 1* versus 2* should not matter much. The idea is for both units to complement each other. We find upstairs units often set way different from the downstairs because of not being occupied much. The topic here was to set the temperatures close so that one system doesn’t overwork and keep the entire home conditioned.

      In the summer same thing. If you do not occupy the upstairs as much you should still set the temperatures fairly close to maintain comfort for the entire home. 1 or 2 degrees should be fine, some prefer 3 degrees. Remember, not only is the summer sun beating down on the upstairs, but heat rises also. So if you do occupy the upstairs often ..set it to your comfort but remember to let the downstairs unit run also to reduce the amount of heat rising.

  14. I live in a 2 story house and if I want a temperature of 73 during the summer, I followed your advice and set my downstairs thermostat to 72 and the upstairs to 74. But I notice that once it reaches those temperatures and the unit shuts off, it will stay off for like 10 min, and it will turn back on again, even if the temperature in both thermostats is still matching the respective set temperatures. For example: the upstairs is set to 74 and it reaches that temp. and the downstairs is set to 72 and it reaches that temp. But the unit still turns on even if the temperature did not rise at least one degree. Is that normal?

    • I dont think you have anything to worry about. It is normal. Today’s digital thermostats actual can measure in tenths of a degree. For example it may be 72.6 degrees and this causes a call for cooling. Today’s air conditioners are designed to try and maintain temperatures, not have extreme variances of temperature. Many thermostats and high efficiency communicating air conditioning systems have logic boards that enable them to learn recovery time also. I have seen systems normally cycle up to 9 times per hour under normal conditions with a smart thermostat.

      Poor insulation could be the reason for the cycle times, outdoor temperature ,house infiltration, etc. Many variables in how many times the ac system is turning on and off. In many of today’s high efficiency air conditioners, the units run for longer periods of time at low speeds to remove humidity and increase comfort. It has higher front end costs but actually reduces energy consumption by running longer and have fewer start ups.

  15. Beverly Jones says:

    I turned my parents insulated attic into a one bedroom flat. Summer months it gets extremely hot winter its cold. I purchased a 12,000 btu window heat and air unit. The room is parallel in shape with a stairwell entrance.. My first question is… Should I block the staircase entrance? My second question is… What setting is best recommended to keep my insulated attic apartment cool?

    • I dont like the idea of blocking an entrance. We prefer to look at the entire structure as an envelope.
      The proper setting is whatever makes you comfortable. There are so many settings because people have different ideas of what comfort is. If your hot turn it down, etc…and vice versa.

  16. Latisha Odell says:

    Hi. I’m looking at installing a window unit in my masterbedroom on the 1st floor. We have a two story home with a unit for both floors (unfortunately the builder did not use the proper size and by the time we realized it, we were out of warranty). Will installing the window unit be a smart move?

    • It is an option. Ideally you would want the efficiency and comfort of the properly sized unit. Be sure it is undersized. We have seen many systems properly sized but not properly ducted. Incorrect duct work can cause many comfort issues and affect your air conditioning system operation.

      • Latisha Odell says:

        Yes, the duct work is correct, because they had to come back and redo it. Our house is 2902 square feet. Each unit is the 13 instead of the 15.

        • We actually would need to see the area to make correct assessment, unfortunately our air conditioning repair service area is in Rockwall Texas. But, with the information you have given it could possibly be something as simple as needing a return air duct to the bedroom.

          In general, bedroom doors are closed most of the time, this does not allow the air to exchange ideally. If the system is properly sized and the duct is sized properly, I would put a return air vent in the space. We have solved many room issues of uneven temperatures with return ducts to the rooms. Including my own ! Our master bedroom was about 3 degrees warmer than the rest of the house until I added a return duct to the room. Problem was solved with the addition of a return to the bedroom.
          Zoning is something you might consider also. Zoning allows a separate controller in the bedroom and dampers at the unit to allow for different settings for different areas. Its a little pricing and not always an option. You would need a professional to look at it.

          Start with a return to the bedroom, it should not be overly expensive, and no added electricity usage from a window unit or the noise

  17. Belinda says:

    I have one unit two thermostats on 2 story home does the 2 degrees difference still apply?

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