Retrofit IGUs into existing timber frames.

Good candidates for IGU drop-in retrofit.

• Timber sash window or french door, pre-1995 build
• Original timber frame is structurally sound (minor paint and seal issues are repairable while sash is out)
• Rebate depth allows a 20mm IGU (vast majority of pre-1990s timber frames do)
• Heritage Overlay property where full window replacement triggers planning permit issues
• Owner wants to preserve period character (Old Berwick weatherboards, Cranbourne 90s timber-frame, federation cottages)

When full replacement is the better call.

• Original frame is mill-finish aluminium — thermal-bridge problem means retrofit isn't worth it. Full thermally-broken aluminium replacement is the right answer.
• Major rot in the sill, bottom rail or stiles — not repairable in place.
• You want a different opening style (changing awning to sliding, casement to fixed, etc.)
• You want to widen the opening (no longer a retrofit — lintel rework required).

Our retrofit process.

1. Site measure (free): 60-min visit. Each sash measured 3 times. Rebate depth checked. Frame condition assessed sash-by-sash — the honest restore-or-replace call is made openly with you, on the day.
2. Manufacture: 20mm argon-filled IGUs assembled to your exact opening sizes by AGGA-affiliated Melbourne manufacturer. 6–10 weeks. Glazing beads cut from matching timber profile.
3. Install day: Sash by sash — remove, machine the new bead rebate if needed, drop IGU in, set on neoprene setting blocks, install new bead with concealed pinning, re-hang. 1–1.5 days for a typical 15-window house. House stays sealed against weather throughout.
4. Finish: Repair any minor sash issues while it's out — touch-up paint, replace failed putty, lube hardware. Air-seal the perimeter caulking with quality silicone (most original perimeter caulk has long since failed).
5. VEU lodgement: Photographs of removed single glass and installed IGU rating sticker submitted via Accredited Provider. Rebate netted off the invoice. WERS ratings and 10-year cavity warranty issued.

What it costs.

Standard IGU drop-in retrofit (per window, argon clear Low-E, including minor sash refurbishment): $600–$1,000/window.

Compared to full thermally-broken aluminium replacement at $1,200–$1,800/window, the saving is $400–$700/window — about $7K–$12K saving on a typical 15-window full-house retrofit. You give up some thermal performance (timber-rebate retrofit U ~2.0–2.2 vs full TB-alu replacement at U ~1.7–1.9), but for heritage and period properties it's the clearly right answer.