Window frame materials

Material choice affects three things: price, how much maintenance you sign up for, and how the frame behaves as temperature swings. Frames that expand and contract a lot put stress on the glass seal over time.

Vinyl is the default in most of the US because it is cheap and needs no painting. Quality varies enormously between vinyl lines — welded corners, wall thickness, and internal reinforcement matter more than the word "vinyl" on the brochure. Dark colors absorb more heat and move more.

Fiberglass moves very little with temperature and can be painted. It costs more up front and fewer local installers stock it. Wood looks best and can be repaired indefinitely, but it needs refinishing and it rots if flashing fails. Clad wood puts an aluminum or vinyl skin on the outside to cut that maintenance.

Aluminum without a thermal break conducts heat and invites condensation. It is common in warm climates and in commercial work; in a cold climate, check the NFRC U-factor before you consider it.

How to choose

Compare the NFRC label, not the material name

Every certified window has an NFRC label listing U-factor, solar heat gain coefficient, visible transmittance and air leakage. Lower U-factor and lower air leakage are better. That label is comparable across brands; marketing copy is not.

Match SHGC to your climate

ENERGY STAR criteria vary by climate zone. In hot, sunny climates a lower solar heat gain coefficient reduces cooling load; in cold northern climates some solar gain is useful. Check the ENERGY STAR zone map for your area.

Ask about the specific product line

Most manufacturers sell a builder-grade line and a premium line. "We install Brand X" tells you almost nothing. Get the line name and the NFRC numbers.

Weigh maintenance honestly

If repainting wood every several years is not going to happen, do not buy wood. Clad or fiberglass is a better fit.

Don't pay for triple glazing reflexively

Triple pane helps most in cold climates and for noise. In mild climates the added cost often buys little. Ask for the U-factor difference and the price difference side by side.