When It Comes to Heating and Cooling Systems, Size Matters

Size may not matter for some things. But when it comes to your heating and cooling equipment, it not only matters, it is critical – both to the wellbeing of your home, and your wallet.

If you choose a heating unit that’s too large, it will turn on and off more often, create hot and cold spots, and generate high noise levels. An oversized air conditioning unit will likely run long enough to cool, but not to dehumidify. In both cases, incorrect sizing will increase your fuel consumption and operating costs, and contribute to premature part failure.


Under-sizing of equipment will be equally problematic, causing a number of comfort problems and an inability to keep up with demand, especially in temperature extremes.

How to avoid these scenarios? Make sure your contractor does a complete “heat loss and heat gain calculation” on your home. Only by reviewing all the variables with these calculations – and there are many variables – can the appropriate size be determined.

This requires both an onsite assessment of the home, as well as an in-depth discussion with the homeowner about lifestyle and future plans. Changing windows, upgrading insulation levels, finishing the basement, air-sealing or adding a new addition – all these upgrades will impact a sizing calculation.

The contractor will also take into account:

  • Local climate conditions;
  • Existing hot and cold spots;
  • Size and number of windows that let in heat from the sun;
  • Existing insulation levels;
  • Number and lifestyle of a home’s occupants; and
  • Predicted or known air exchange rate of the home

Beware of contractors who fall short of performing a full calculation. Warning signs include a calculation made over the phone or within a brief 15-minute visit. A good estimate takes upwards of an hour – sometimes more – and examines all variables. If the points outlined above are not part of the discussion, this should also raise warning flags, and ditto for contractors who indicate it is sufficient to just replace old equipment with new equipment of the same size.

Do not agree to a simple “rule of thumb” calculation (e.g., X amount of BTUs per square foot), and be sure to request a “heat loss and heat gain calculation” as part of your purchase process. Any piece of HVAC equipment constitutes an expensive, and important, purchase. Make sure you get it right, and you will have years of comfort ahead.

To find a qualified contractor, visit the HRAI Contractor Locator or call the hotline at 1-877-467-4724.

All HRAI Member Contractors have been prescreened and have the required trade licenses, technical certifications and insurance coverage to work on your system.




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