HVAC
HVAC Load Calculator
Estimate whole-house heating and cooling loads from area, construction and window area.
Result
This is a preliminary sizing estimate using industry rules of thumb. Actual equipment selection requires a room-by-room load calculation (ACCA Manual J) and duct design (Manual D) by a qualified professional, oversized equipment short-cycles, dehumidifies poorly and fails early. Windows are frequently the single largest load component, which is why glazing area is separated out here.
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About this calculator
Why does window area matter so much?
Glass has a fraction of the insulating value of an insulated wall and admits solar gain directly. A wall of south-facing glass can dominate a house's cooling load.
Should I get a real Manual J?
Before buying equipment, yes. It costs a few hundred dollars and routinely finds that a house needs a smaller system than the rule of thumb suggests, which saves more than the calculation costs.
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