Heating and cooling load calculations determine the amount of energy needed to change the climate in a structure to a certain desired point. The load is influenced by heat gains, heat loss and air infiltration. To determine the correct load for heating and cooling, taking into account those gains and losses is crucial to accurately calculate the correct HVAC system size.

Cooling load, as well as home heating load calculations are a function of the “Manual J” from the ACCA or Air Conditioning Contractors of America. To calculate this number you need to know design conditions, thermal enclosure and internal loads of the structure you’re calculating for. Design Conditions are the location and architectural make-up of the building. Thermal enclosure is the type of insulation and materials around the house, protecting it from heat loss and gain. Internal loads are things like ovens, refrigerators, lights and appliances that will add to the heat of a house.

The difference in calculating these numbers is that for heating installations, the majority of the heating will be done at night, when internal loads will be at a minimum. On the contrary, internal loads for cooling are going to be higher because the main time the cooling system will be working is when people are in the home doing activities. That is why a rule-of-thumb or “educated guess” will not work for home heating load calculations. Even if the Manual J has been performed before for cooling systems, when getting ready to install a new furnace or heating system, re-calculating the Manual J for heating is extremely important. This will save you money in energy bills as well as keep your system from being over-burdened and requiring frequent repairs.

For more expert information on installation and load calculations, contact us, we are happy to answer any questions you may have. At Apollo Home Heating, Cooling, and Plumbing, we’ve been proudly serving the Cincinnati area for over a century.

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