Heat gain is the increase in indoor temperature from external and internal sources such as sunlight, warm outdoor air infiltration, occupants, lighting, and equipment. It drives cooling load and affects HVAC sizing, comfort, and energy use. Managing heat gain with insulation, shading, and ventilation improves efficiency.
/hiːt ɡeɪn/
Heat gain is the increase in indoor temperature from external and internal sources such as sunlight, warm outdoor air infiltration, occupants, lighting, and equipment. It drives cooling load and affects HVAC sizing, comfort, and energy use. Managing heat gain with insulation, shading, and ventilation improves efficiency.
Why does heat gain matter for HVAC?
It determines the cooling load needed to keep indoor spaces comfortable and efficient.
Source: The Cooling Company
Reducing heat gain lowers cooling load and energy use.
An office building installs shading and low‑E windows to cut solar heat gain, reducing air conditioning costs.
Use smart shading, window film, and air sealing to reduce heat gain without sacrificing daylight.
“Use smart shading, window film, and air sealing to reduce heat gain without sacrificing daylight.”
Even small air leaks can introduce significant heat gain during hot weather.
What is the biggest source of heat gain?
Solar heat through windows is often the largest contributor, especially on west‑facing glass.
How do I reduce heat gain without blocking light?
Use low‑E glass, reflective films, or exterior shading devices.
Does heat gain affect HVAC sizing?
Yes. Higher heat gain requires larger cooling capacity.
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