PGT Home Additions & ADU Nationwide

PGT Home Additions & ADU: The Cupertino Owner’s Guide

PGT-compatible windows and doors for home additions and ADUs in Cupertino typically run $8,000-$25,000 installed, depending on the unit count and whether the opening requires structural modification. We stock common PGT sizes for the Silicon Valley market and can usually source less common series within 48 hours. Most Cupertino homeowners discover their PGT unit is failing when a bedroom addition or garage-to-ADU conversion starts showing daylight around the frame, or when the dual-pane seal fails and the glass fogs permanently.

Call (669) 202-9618

Which PGT Models This Applies To

PGT builds two product families relevant to Cupertino additions and ADUs: the WinGuard impact-resistant line, required by code for any detached ADU in Santa Clara County’s wind-borne debris region, and the EnergyVue non-impact vinyl series, common for second-story bump-outs and master suite additions where the existing roofline shields the opening. The aluminum WinGuard frames carry a stamped series code on the interior jamb, usually WGD or WGA followed by the nominal size. EnergyVue units label the sash lock side with an EV prefix.

The critical compatibility gotcha in Cupertino’s 94014 and 95014 zones: WinGuard and EnergyVue use different frame depths, 4 1/2 inches versus 3 1/4 inches. Swapping one for the other without adjusting the rough opening throws the drywall line off and voids the factory warranty on the install. We measure the existing jamb depth before we quote, because a mismatched replacement means reframing the opening, and that changes the price by $400-$1,200 per unit. Rowan Construction Group Cupertino is an independent service provider, not affiliated with PGT. We source OEM PGT units through authorized distributors in San Jose and also install quality aftermarket equivalents from CWS and CGI when the homeowner’s priority is lead time over brand matching.

Signs Your PGT Home Additions & ADU Is Failing

• Fogging between panes that won’t wipe clean. This means the insulated glass unit’s edge seal has failed, releasing the argon fill. In Cupertino’s wide temperature swings, Monta Vista and Rancho Rinconada homes see this most often on south-facing ADU units where daily expansion cycles stress the seal.
• Difficulty latching or a sash that drifts open. The balance system, either a coil spring or block-and-tackle type depending on PGT series, has lost tension. On WinGuard casements, this often traces to corrosion in the stainless steel hinge arm from coastal moisture pushed inland by afternoon valley winds.
• Visible gaps between frame and wall, or water staining on the interior sill. The nailing fin or installation flange has separated from the structure, or the sill pan flashing was omitted or reverse-lapped during original construction. This is structural, not cosmetic; water follows the path of least resistance into the stud bay.
• Cracked or crazed impact glass with the laminate layer intact. The WinGuard interlayer is doing its job, holding shards in place, but the unit has lost its wind-pressure rating and no longer meets code for ADU occupancy. Replacement is required before final inspection.
• Excessive condensation on the interior surface in winter. This indicates the low-E coating has degraded or the warm-edge spacer has failed, dropping the interior glass temperature below the dew point. In Cupertino’s older Ranch-style additions with minimal wall insulation, this symptom often appears before the fogging between panes does.

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Replacement Cost & What’s Included

For PGT window and door replacement within a Cupertino home addition or ADU, our installed pricing breaks down as follows:

What drives the range: unit size, series (WinGuard costs 40-60% more than EnergyVue), whether the stucco or siding needs repair after removal, and whether the city requires a permit for the replacement. Cupertino requires permits for any window change that alters the opening dimension or the egress capacity; we pull those permits and schedule inspections as part of the flat written price. Under Clause 1 of the Haven Standard, that price is delivered before anyone picks up a tool. The quote includes the PGT unit or approved equivalent, installation per manufacturer spec, interior and exterior trim repair, debris haul-away, and our 365-Day Done Right Promise on the workmanship.

DIY or Call Us?

An owner can safely check the label location and frame depth with a tape measure and flashlight. What’s not safe: removing a PGT WinGuard unit solo. These frames weigh 80-140 pounds depending on size, and the temporary opening exposes the structure to weather until the replacement is secured and flashed. We’ve responded to three Cupertino calls in the past two years where a homeowner removed the old unit on Saturday morning, discovered the rough opening was out of plumb, and spent the weekend with plastic sheeting where a wall should be.

Call (669) 202-9618 and we’ll schedule a no-charge site visit. We bring the laser level, the sill pan, and the documented photo record so you see what we see before the quote is written.

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