10 Questions to Ask a Window Replacement Contractor
The 10 Questions — and Why Each One Matters
A contractor who answers these confidently, with specifics, is demonstrating the transparency and competence that separates good work from mediocre work.
“Are these windows Energy Star certified, and what are the U-factor and SHGC ratings?”
Why this matters: U-factor measures heat transfer (lower = better insulation). SHGC measures solar heat gain (lower = less heat in summer, higher = more passive solar in winter). Energy Star minimums vary by climate zone — ask for the specific values for the window being quoted, not just "Energy Star certified."
“What is the frame material, and what are its maintenance requirements?”
Why this matters: Vinyl requires no maintenance but can't be painted. Fiberglass is more dimensionally stable and can be painted. Wood-clad offers aesthetics but requires periodic exterior maintenance. Each has different thermal performance. Make sure you know what you're getting.
“Do you manufacture your own windows, or are these a third-party brand — and which product line?”
Why this matters: Many installers sell proprietary window lines with limited external reviews. Ask for the brand name, series, and model. Research it independently. Manufacturer warranties vary significantly — 10-year vs. lifetime, transferable vs. non-transferable.
“How do you handle discovery of rotted framing or damaged rough openings?”
Why this matters: Rot in the rough opening framing is common, especially in older homes. Ask what happens when they find it: fixed price per LF of framing replacement, or hourly? Get this in writing before demo begins.
“What does your installation warranty cover, and for how long?”
Why this matters: Product warranties cover glass and hardware defects. Installation warranties cover the contractor's workmanship — flashing, sealing, trim finishing. These are separate. Ask: if water infiltrates around the frame in year 3, is that a product claim or an installation warranty claim, and who handles it?
“Are you pulling permits for this installation, and are you a licensed contractor in my state?”
Why this matters: Window replacement usually needs a permit, especially where structural changes are involved — confirm with your local building department. Permits mean inspections — a safeguard for you.
“How many windows can your crew complete in a typical day?”
Why this matters: Rushing a window installation leads to flashing shortcuts. A professional crew should complete 6–10 standard windows per day. Very high numbers (15–20/day) suggest minimal attention to flashing and sealing detail.
“What is your process for protecting interior finishes — floors, walls, trim — during installation?”
Why this matters: Window installation creates dust, requires temporary weather exposure, and sometimes damages interior trim. Ask specifically: do they use floor protection, how do they handle interior trim removal and replacement, and who patches drywall?
“Do you offer financing, and what are the terms including APR?”
Why this matters: Many window companies offer 0% financing for 12–18 months. After the promotional period, rates often jump to 25–29%. Know the full terms before using contractor financing.
“Are you a certified installer for the window brand you're selling?”
Why this matters: Manufacturers like Renewal by Andersen require certified installers for warranty validity. Ask to see the certification for the specific brand. An uncertified installer may void the manufacturer warranty.
Red Flags to Watch For
Any of these during your contractor search should prompt closer scrutiny or disqualification:
- Same-day pricing pressure with a deadline
- Won't provide U-factor/SHGC in writing
- Offers to skip permits to "save you money"
- Vague about who specifically will do the installation
- No written warranty terms — "we guarantee our work" verbally only
- Significantly lower bid without explanation of what's different