Double Pane Resealing

True IGU seal failure shows up as moisture trapped between the two panes — you can't wipe it off from inside or outside. The fog appears in cold weather first (when the interior pane is coldest and the trapped humidity condenses), often clears in warm dry weather, and progressively gets worse over years. Eventually you see permanent mineral deposits or even visible silica desiccant residue from the spacer. That's a hard diagnosis — it's an IGU replacement.

Condensation on the interior surface of the glass (where you can wipe it off) is a different problem. That's high indoor humidity, low interior surface temperature, or both. The fix is dehumidification, better window treatments, or in extreme cases upgrading to a warmer IGU spec — not replacing the existing IGU. We talk customers through this distinction on the phone before scheduling a visit, because we don't want to charge for a measurement on a problem that's not ours to fix.

Condensation between a storm window and a primary window is a third scenario. Common on older NJ housing in Princeton, Madison, and Cape May with original wood sashes and exterior storm panels. The fix there is improving the primary window's seal so warm interior air stops migrating into the storm cavity — not replacing the storm or the primary glass.

Frame leaks that show up as water on the sill rather than fog between the panes are another category entirely. That's perimeter sealant failure, flashing failure, or in newer windows a defective weep system. We diagnose those separately and fix the frame and flashing rather than touching the glass.

Reseal makes sense when: the sash frame is sound (no rot, no warp, no separated joints), the glazing system is field-serviceable (most vinyl, aluminum, and clad-wood windows are; some older fixed-glass windows aren't), the hardware still works on operable units, and the energy performance of a new IGU is acceptable. For a 15-year-old Pella casement in good shape with one foggy IGU, reseal is a no-brainer — saves the customer 50-70% over full replacement.

Full replacement makes sense when: the sash is rotted (common on wood sash 30+ years old), the seal failure pattern indicates frame movement (multiple IGUs failing at the same corner suggest a structural problem), the hardware is failed and parts are no longer available, the existing window's U-factor and SHGC are so far below current code that the energy savings of a new full unit justify the cost, or the homeowner is doing a whole-house aesthetic update.

Honest assessment matters here. We've talked customers out of full replacement when the existing windows had another 15-20 years of service life left and a reseal was the smart move. We've also told customers that resealing a 1985 wood window with rotted muntins is throwing money at a problem — full replacement was the only honest answer.

Standard rectangular IGUs up to 48" x 60" with dual-pane Low-E argon make-up: 7-10 business days from our manufacturer partners (Cardinal IG, PPG, Vitro). These are the bread and butter and the price is consistent.

Custom shapes (arched tops, half-rounds, octagons), oversized IGUs (over 60" x 80"), and triple-pane assemblies: 14-21 business days. The shape templates have to be made and verified, and triple-pane spacer fabrication takes longer.

Specialty IGUs — Starphire low-iron, laminated interlayers for noise or security, custom internal grilles to match historic patterns, dichroic or decorative glass: 21-30 business days minimum, sometimes 6-8 weeks for true custom decorative work.

Emergency situations get prioritized. A retail tenant with a fogged storefront IGU we can sometimes turn around in 3-5 days through expedited fabrication with a 25-30% surcharge. We're upfront about the cost — most customers wait the standard lead time once they hear the difference.

Step one is removing the failed IGU. On vinyl windows that usually means removing the interior glazing bead (snap-in vinyl strip or stop), supporting the IGU as it releases, and lifting it out. On aluminum windows the exterior gaskets pull out and the IGU rolls out the front. On wood windows with putty glazing it's chisel work — we use a glazing tool to score the putty and lift the glass with vacuum cups.

Step two is cleaning the glazing pocket. The old butyl glazing tape or sealant has to come out completely so the new IGU seats properly. We use a plastic scraper (not metal — metal scores the frame and creates a leak path) and acetone or naphtha to remove residue.

Step three is setting blocks. Per IGMA TM-3000, setting blocks go at the quarter points of the sill (not the corners) at 90 durometer EPDM. This is non-negotiable — a glazier who sets the IGU directly on the frame is creating a future failure point.

Step four is glazing. New butyl glazing tape on both sides, snap the bead back in, tool any exposed sealant smooth. On wood sashes we use linseed-oil putty for the exterior face if the original was putty-glazed — modern silicone reads as wrong on a historic window.

Step five is the warranty paperwork. We label the IGU with installation date in a corner, hand over the manufacturer's 20-year warranty card, and document the install with photos. Future failures (rare but possible) are traceable to our install and the manufacturer's batch.