Glossary · Insulation & windows
Solar heat gain coefficient (SHGC)
Also called: solar heat gain
The share of the sun's heat a window lets into the house, from 0 to 1; lower keeps homes cooler, higher adds free winter heat.
What it means
An SHGC of 0.25 means about a quarter of the solar heat hitting the window gets through. In hot climates a low SHGC cuts air conditioning; in cold climates a higher SHGC on sunny windows can provide useful heat. Low-e coatings can be chosen to raise or lower it.
Why it matters in an audit
Choosing the right SHGC for your climate and window orientation affects comfort and both heating and cooling bills, and it's part of the ENERGY STAR window criteria.
Typical numbers
Reference values with their sources. Your auditor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| ENERGY STAR windows, US (Version 7.0) | Northern zone SHGC ≥ 0.17 (trade-off options allow U 0.23–0.26 with SHGC ≥ 0.35–0.40); North-Central ≤ 0.40; South-Central and Southern ≤ 0.23 | energystar.gov ↗ |