Window and door companies on Exchange
Windows and doors are the openings in an otherwise continuous building envelope, and almost every performance problem a building has — heat gain, heat loss, air leakage, water intrusion, condensation, noise, forced entry — concentrates at them. The trade covers residential replacement and new-construction window installation, entry and patio doors, storefront and commercial glazing, curtain wall, automatic entrances, garage and overhead doors, and the shutters and impact glazing used in high-wind regions.
Two numbers describe a window's thermal behaviour and they are not interchangeable. U-factor measures how readily heat conducts through the assembly and governs in heating-dominated climates. Solar heat gain coefficient measures how much of the sun's energy passes through and governs in cooling-dominated ones. A window that is excellent in Minnesota can be a poor choice in Houston. Both figures, along with visible transmittance and air leakage, appear on the NFRC label, and in Australia the equivalent is the WERS rating. Building energy codes set minimums for each by climate zone, and the label is what an inspector checks.
Installation is the product
A high-performance window installed without correct flashing and integration into the wall's water-resistive barrier will leak, and the manufacturer's warranty will not cover it. The recurring failure points are the sill pan, the sequence in which flashing laps shed water outward and downward, the perimeter sealant joint and its backer rod, and the shim and fastening pattern that keeps a unit square and its sashes operating. On commercial glazing, air and water performance is tested to AAMA and ASTM standards and larger projects specify field water testing during construction rather than trusting the shop drawing.
Code requirements that decide the specification
Safety glazing - tempered or laminated - is required in hazardous locations: doors and sidelights, glazing close to walking surfaces and stairs, and glazing near tubs, showers and pools. Bedroom windows must meet emergency escape and rescue opening dimensions, which a retrofit insert window can quietly defeat by reducing the clear opening. In hurricane and windborne-debris regions, glazing must be impact-rated or protected by approved shutters, evidenced by a product approval number. In bushfire-prone areas in Australia the equivalent is the BAL rating and AS 3959 compliance.
Related trades
Window and door companies work alongside building envelope contractors, renovation contractors, carpenters, general contractors and roofers — or list your own firm free through the Add a Listing page.
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Frequently asked questions
What is the difference between U-factor and SHGC?
U-factor measures how readily heat conducts through the window assembly and matters most in heating-dominated climates. Solar heat gain coefficient measures how much solar energy passes through the glass and matters most in cooling-dominated ones. Both appear on the NFRC label along with visible transmittance and air leakage, and energy codes set minimums for each by climate zone.
Do I need a licence to install windows and doors?
It varies by jurisdiction. Some states and provinces license it under a general or specialty contractor licence; others, including Texas, have no state licence at all and rely on municipal registration and permits. Australia requires a builder or trade licence in most states. Where no licence exists, verify insurance, manufacturer certification and local permit registration instead.
Why do new windows sometimes still leak?
Almost always because of installation rather than the window. The recurring failure points are a missing or incorrectly formed sill pan, flashing lapped in the wrong sequence so water is directed inward, a perimeter sealant joint without backer rod, and integration with the wall's water-resistive barrier. Manufacturers exclude installation defects from the product warranty.
Can a replacement window fail egress requirements?
Yes. Bedrooms need an emergency escape and rescue opening meeting minimum clear area, width, height and sill height. A retrofit insert installed inside the existing frame reduces the clear opening, so a window that only just complied before can fall below the minimum after replacement - a defect that surfaces at inspection or at resale.
When is impact-rated glazing required?
In designated windborne-debris regions - coastal Florida, the Texas coast, and comparable zones elsewhere - glazing must be impact-rated or protected by approved shutters, documented by a product approval or notice of acceptance number for the specific assembly. Insurers frequently offer premium credits for compliant opening protection, and some require it for coverage at all.
How long should windows last?
Frame and glass are separate questions. A well-installed vinyl, fibreglass or clad-wood frame commonly lasts 25 to 40 years, while the insulated glass unit's seal typically fails earlier - visible as permanent fogging between the panes, which is a glass unit replacement rather than a whole-window one. Hardware and weatherseals are consumables and are usually the first thing to need attention.
