I live in a 2-story rental townhome (basically an apartment with 2 stories). Our central air/heat system isn't really the best at keeping the upstairs and downstairs the same temperature whether in winter or summer.

I think this is partially because the thermostat is downstairs but also due to a not well insulated upstairs.

Winter is not as big of problem because space heaters are cheap to buy and operate. Summer is harder because portable AC units are more complicated in rental units.

We have tried closing vents downstairs but generally speaking this has not worked well.

Now that it is becoming warmer again I am hoping to find ways to determine where our unit loses its coolness upstairs to target them more directly, but am not sure how to best do this.

  • Kind of a crappy setup for the tenant that they can't even control the temperature. Not even sure this is legal in a lot of areas.
    – DMoore
    May 18 '13 at 18:43

Whether for heating or cooling, your goal is to limit the amount of heat going through the building envelope, it's just the direction the heat is moving is reversed. Cooling loads are complicated by radiant heat gain which is not much of an issue for heating loads. Thermal imaging can identify areas of high heat conductance, indicating where more insulation is required.

Other than that, simple inspection can indicate where the heat is getting in (or out). Are there any gaps in windows and doors allowing air to leak in or out? If the windows are singled glazed, that will be the largest single cause of heat gain. How much insulation is in walls and ceilings? What's good for heating is good for cooling. In addition for cooling, how is the sun allowed to radiate heat into the building. Lack of shading devices, window tints, draperies or shades, etc. all contribute to heat gain.


get a thermal imaging camera and point it at the outside of your house when the temp difference inside and out is significant (though it works best is the outside is cold and inside is warm)

there are people you can hire for this type of service

  • Also good for finding problems in leaky buildings. The type where water is coming in. My parents house was a leaky home and they got thermal images given to them by a company specializing in leaky buildings. Pretty cool images.
    – hookenz
    Jul 18 '13 at 3:30

The surfaces near the heat-leaks will be at a different temperature than surfaces in other areas of the room, all of which can be measured with a digital IR thermometer.



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