Load Calculations

To save money on first cost as well as operating and maintenance of the HVAC equipment, it is important to size the systems according to the heat loss of a building in the winter and the heat gain of a building in the summer.  For most houses, a standard method is recommended for estimating this loss/gain (referred to as the heating and cooling "loads”). This method is called Manual J, and is published by the Air Conditioning Contractors of America (ACCA).  Load calculations provide the builder/HVAC contractor with an accurate measurement for the HVAC sizing requirements – eliminating guesswork and “rule-of-thumb” assessments.

Manual J models how the house will perform on a relatively hot or cold day, using outdoor conditions that are almost “worst case”.  These design temperatures will be used to determine the temperature difference (and calculate the heat transferred) across each component -wall, floor, window, etc.

How We Can Help

Southface offers ACCA approved Manual J load calculations for residential building projects. The analysis can be done "whole house" on a floor by floor basis or room-by-room.  Unless the house is particularly large or has unusual architectural features, the whole house method is usually adequate for estimating sizing purposes.  If the house will have multiple heating/cooling zones (areas that have independent temperature control) then room-by-room analysis may be needed. Use the service request form to contact us about load calculations.

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