# Climate and efficiency notes

This sample brief begins with the heating load, not the equipment label. Insulation, air sealing, window area, floor plan, and local winter design temperature determine how much heat the home needs. A contractor should measure or calculate that load before choosing capacity.

An air source heat pump moves heat instead of creating it through combustion. Its delivered heat and efficiency change with outdoor temperature. A cold climate model should be compared at the temperatures the home will actually see, including its capacity and coefficient of performance near the local design point.

A gas furnace creates heat by burning fuel. Its rated efficiency describes conversion at the appliance, but the whole system also includes duct leakage, fan energy, and the condition of the distribution system. Existing ducts may need work for either replacement.

A heat pump can provide both heating and cooling. A furnace comparison should therefore include the separate air conditioner the home would otherwise need.