There is a common question when installing a furnace in most residential units. If the specific location is not located on the drawings (in most residences, these are not located in builders drawings but frequently are in commercial drawings), the thermostat should be near the return air and central to the area that it serves. The return air pulls air from all over the house to it to take it back to the furnace. (Spoiler from the reading below, as a general rule Thermostats are placed at about 48" above finish floor).
In other words, put the thermostat in the middle of the house. There are considerations to this, however. There are many different layouts of houses, including multiple levels, basements or second or third floors. Even multiple furnaces need to be considered or multiple zones on different units.
one level house or apartment
In most cases, especially in dense urban areas, homes and houses are limited to less than 2,500 square feet. Most apartments being much smaller than that, around 1,000 to 1,200 square feet. They can be even smaller in larger cities.
In almost every house or apartment that does not have a basement or any other floors the furnace will be placed in the center of the dwelling.
Minimal return air ductwork will be used which would put the return air very close to the location of the furnace. So when considering the questions, "Where Should I Put The Thermostat In My House", This would put the thermostat in the general area of the return air at about 48" off the finished floor.
multiple zones
If your dwelling has multiple zones, a thermostat will be central to those zones. This type of system is common with a mini split system. Zones are controlled from one location in that zone.
These types of systems are convenient for houses with poor insulation. However, mini split systems are not very common in the United States in residential dwellings. They are more expensive to install and most people steer away from them.
In this instance when considering the questions, "Where Should I Put The Thermostat In My House", the thermostat would go typically in one room that the zone covers. If your team wants to install a mini split system, be sure that the thermostat is in the room or area that represents the most moderate condition.
I will give you an example. If there are four bedrooms on a mini split system and two of them are on the north side of the house and two are on the south, the rooms on the south are going to be hotter in the summer and the two on the north are going to be colder in the winter. The thermostat should go on a partitioning wall between the north room and the south room.
Your set up may be different, so be sure to consult with a local professional if this is an option for you.
Multiple Furnaces
If your dwelling has multiple levels, either split level or a basement with additional floors, there is a chance that you may have two or more furnaces. This type of layout is not uncommon and, depending on the size of the dwelling, two or more furnaces may be required. A furnace does well to serve an area of up to 2,500 square feet. Any bigger and most residential furnaces become very inefficient.
You may also want to consider installing a separate furnace for the basement and an individual furnace for the other floors. Basements area often much cooler than the other levels and the same heating and cooling requirements vary greatly from basement to other floors.
In this instance, the basement would have a thermostat central to the area at or near the return air and the other floors would have one as well (close to the stair way between floors for one furnace or central to each floor if there are multiple furnaces).
Where not to put a Thermostat
Never put a thermostat next to a supply air vent. Here is why. When the Thermostat asks the furnace or Air Conditioning to come on, it has left its set range on the thermostat. A typical range for a thermostat is plus or minus 1.5 degrees. (So if you set the thermostat to 75 degrees in heating mode, it will kick on around 73.5 degrees and turn off around 76.5 degrees.)
If the thermostat is placed at or near a thermostat there are two factors that are acting on the thermostat. The first is that the thermostat would typically be on an exterior wall and the thermal transfer of heat or cold from the outside affects how fast the thermostat changes. Exterior walls are colder than interior walls, even with insulation.
The second factor is that the air from the supply vents are blowing on the thermostat and fluctuating the measurement of temperature very quickly. Imagine taking the hair dryer and blowing it on your face on High and Hot. It would immediately warm up, it may even burn you (don't try that). The furnace is basically just a really big hair dryer. Placing the thermostat too close to a vent is going to leave the dwelling hot or cold all the time.
The thermostat in the wrong location will lead to higher electric bills. If you need additional help, ask you local HVAC technician when they are there for the annual furnace tune up.
Conclusion
"Where Should I Put The Thermostat In My House?" has now become an answered question. Consult with a professional if needed but we hope that your now know where to put a thermostat or at least where not to put a thermostat.
