Window and door installation doesn’t carry its own regional trade licence the way electrical or plumbing does — which means the barrier to entry is lower and the range of operator quality is wider. That makes verification more important, not less. A window contractor without proper insurance working at heights on your home, or one without manufacturer certification who voids your product warranty through improper installation, costs you significantly more than the “deal” you thought you were getting.
“The window industry in many regions has a significant number of operators who are registered businesses on paper but have no manufacturer training, no workers’ compensation coverage, and no meaningful insurance. The homeowner finds this out when something goes wrong — a worker falls, a window leaks two years after installation, or a warranty claim is denied because the installer wasn’t certified. Two phone calls before hiring prevent all of that.”
— Theresa Huang, certified window and door installer and building envelope consultant with 16 years of experience in residential fenestration in the local area
Table of Contents
Business Registration and Credentials
Are you a registered business with a valid tax-registration number?
Any contractor performing renovation work above a de minimis threshold must be registered as a business and registered for sales tax. Ask for the company’s business registration number and tax-registration number. A contractor operating cash-only with no tax-registration number has no formal accountability and leaves you with no meaningful paper trail.
What a good answer looks like: A registered business name, a verifiable business registration number, and a tax-registration number — all easily confirmed.
Are you a member of any professional associations?
The Window and Door Manufacturers Association (WDMA), the Canadian Window and Door Manufacturers Association (CWDMA), or regional home builders’ associations all maintain codes of conduct for members. While membership isn’t a licence, it signals a company that takes professional standards seriously.
What a good answer looks like: Active membership in a relevant association, verifiable on the association’s website.
Are you certified by the manufacturer to install these products?
Manufacturer installation certification is one of the most important credentials in this trade. Most major window manufacturers — Pella, Andersen, Marvin, JELD-WEN, Durabuilt, Gentek, and others — offer certified dealer or installer programs. Certification typically requires:
- Completion of the manufacturer’s installation training
- Meeting minimum installation volume requirements
- Agreement to follow the manufacturer’s installation specifications
Why this matters: Most comprehensive window warranties — the ones covering both product defects and installation-related failures — are only available when the window is installed by a certified installer using the manufacturer’s specified installation method. An uncertified installer may use the same window but you won’t qualify for the enhanced warranty.
What a good answer looks like: Confirmed certification for the specific product being installed, with the certifying manufacturer named and documentation available.
Insurance Questions
Do you carry general liability insurance?
Window and door installation involves removing heavy glazing units, working at heights, cutting through the building envelope, and handling tools that can cause significant damage. If a window breaks during removal, if a tool damages exterior siding, or if water infiltrates during the gap between removing the old window and installing the new one — liability insurance is what covers the repair.
Ask for a certificate of insurance showing current coverage with adequate limits. For residential window work, a minimum of $2 million in general liability coverage is reasonable.
What a good answer looks like: A current certificate of insurance provided within 24 hours, with adequate limits and a policy covering the dates of your project.
Do you carry workers’ compensation coverage for your installation crew?
Window installation involves ladder work, overhead handling of heavy glass units, and work at varying heights. Falls and injuries happen. If a crew member is injured on your property without workers’ compensation coverage, you may face liability for their medical costs and lost income.
Request a workers’ compensation coverage Clearance Certificate and verify it at your workers’ compensation board’s website. Don’t accept a verbal assurance.
What a good answer looks like: A current workers’ compensation coverage Clearance Certificate verified independently at your workers’ compensation board’s website.
Are subcontracted installation crews covered under your insurance?
Many window companies sell and supply the windows but subcontract the installation to separate crews. Ask whether those crews are covered under the company’s liability policy and workers’ compensation coverage, or whether they carry their own verified coverage.
What a good answer looks like: Written confirmation that all installers on your job are covered — either under the company’s policy or through independently verified coverage.
How to Verify What You’ve Been Told
Business registration: your local business registry at your local business registry. Search by business name.
Tax-registration number: your national tax authority’s business registry.
Workers’ compensation coverage clearance: your regional workers’ compensation board’s clearance verification tool using the company name or account number.
Insurance: Call the insurer listed on the certificate and confirm the policy is active and covers your project period.
Manufacturer certification: Check the manufacturer’s website — most have a “find a dealer” or “certified installer” lookup tool.
Association membership: Search the relevant association’s member directory directly.
A Note on your region’s consumer-protection law
Window and door sales in many regions are regulated under the applicable consumer-protection law, which provides specific rights to homeowners purchasing these products. These include:
- A 10-day cooling-off period for contracts signed in your home following a direct sales approach
- The right to a written contract before any deposit is taken
- Specific disclosure requirements for the product, price, and warranty
Ask your contractor whether the applicable consumer-protection law applies to your purchase and what your rights are under it. A contractor who can’t answer this question should prompt follow-up.
Related Questions
- Questions to Ask a Window and Door Contractor Before You Hire One
- Questions to Ask a Window and Door Contractor About Warranties
- Red Flags When Hiring a Window and Door Contractor
- What to Do If a Window Contractor Does Bad Work
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