Windows and doors have specialized vocabulary, and using the wrong term leads to wrong quotes and wrong products. Double-hung is not the same as casement. U-factor is not the same as Solar Heat Gain Coefficient. Full-frame replacement is not the same as pocket replacement. This glossary owns the terms so the how-to and cost pages can stay at the system level. For the broader windows and doors context, the windows and doors guide, the double-hung vs casement comparison, and the energy ratings page are the anchor pages.
Window Terms You Need to Know
| Term | Definition | Why it matters |
|---|---|---|
| Double-hung | Two sashes that slide vertically | Most common residential window type |
| Casement | Hinged at side, cranks open | Better seal, better ventilation |
| Single-hung | Fixed top sash, operable bottom | Lower cost, less ventilation |
| U-factor | Measure of heat loss, 0.20 to 0.30 typical | Lower is better for insulation |
| SHGC | Solar Heat Gain Coefficient, 0.25 to 0.80 | Lower blocks heat, higher admits heat |
| Visible Transmittance | Amount of visible light transmitted | Higher lets in more natural light |
| Full-frame replacement | Removes old frame and sill | Allows flashing and insulation repair |
| Pocket replacement | New sash into existing frame | Faster, cheaper, does not address frame rot |
Door Terms You Need to Know
| Term | Definition | Why it matters |
|---|---|---|
| Entry door | Exterior main entrance door | Security, insulation, curb appeal |
| Sliding door | Glass door on track, slides open | Patio access, natural light |
| Storm door | Secondary exterior door | Weather protection, ventilation |
| Deadbolt | Locking mechanism beyond knob | Security requirement for most codes |
| Weatherstripping | Seal around door edges | Prevents air and water infiltration |
| Threshold | Bottom edge of door frame | Water management and transition |
| Pane | Individual piece of glass | Double-pane is standard for efficiency |
Performance and Code Terms
| Term | Definition | Why it matters |
|---|---|---|
| Energy Star | _certification for efficient products | Meets regional U-factor and SHGC thresholds |
| Low-E coating | Microscopic metallic layer on glass | Reflects infrared heat, improves U-factor |
| Argon gas fill | Inert gas between panes | Improves insulation over air fill |
| tempered glass | Safety glass required in hazardous locations | Required in doors and near bathtubs |
| IRC | International Residential Code | Baseline code for residential windows and doors |
| Egress | Minimum opening for emergency exit | Required in bedrooms and basements |
For owners still learning the trade, the interior door installation guide and the energy ratings page show these terms in practice. For material choice, the window comparison and the doors guide map terms to decisions.
Frequently Asked Questions About Windows and Doors Terms
What is a good U-factor for windows? Below 0.30 is good. Below 0.20 is excellent for cold climates.
What is the difference between full-frame and pocket replacement? Full-frame replaces the entire unit including frame. Pocket replaces only the sash in the existing frame.
Do I need tempered glass? Yes, in all doors and windows within 24 inches of a bathing fixture.
What is E-gress? Minimum window size for emergency exit. Bedrooms and basements require it by code.
What does Low-E mean? Low-emissivity coating that reflects heat. Improves energy performance.
