Heat Gain
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.
💡 Key Takeaways
- ✓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.
- ✓Solar exposure and building orientation strongly affect heat gain.
- ✓Internal loads from people, lighting, and equipment add heat year‑round.
- ✓Lower heat gain means smaller cooling equipment and lower costs.
Heat Gain
/hiːt ɡeɪn/
Definition
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
Quick Facts
How Heat Gain Works
Reducing heat gain lowers cooling load and energy use.
Real-World Application
An office building installs shading and low‑E windows to cut solar heat gain, reducing air conditioning costs.
Pro Tip
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.”
Important Things to Keep in Mind
- Solar exposure and building orientation strongly affect heat gain.
- Internal loads from people, lighting, and equipment add heat year‑round.
- Lower heat gain means smaller cooling equipment and lower costs.
Did You Know?
Even small air leaks can introduce significant heat gain during hot weather.
FAQ
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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