Retrofit Double Glazing in Wellington

Retrofitting suits Wellington better than almost any other New Zealand city, because so much of the housing stock is character timber that owners do not want to lose. Villas and cottages through Thorndon, Mount Victoria, Aro Valley and Newtown, and 1920s bungalows across Miramar, Kilbirnie and Island Bay, all keep their original proportions and their original glass lines this way. Cost sits at roughly half of full replacement, and the disruption is measured in days instead of weeks.

What retrofit double glazing costs in Wellington

Aluminium frames retrofit for about $550 to $850 a window. Timber frames run about $800 to $1,250, because the rebate has to be machined and the beads remade. Aluminium insert units, where a new sash goes into the existing outer frame, sit around $980 to $1,480.

A small home or apartment with 5 to 10 windows commonly lands between $6,000 and $10,000. A standard family home with 10 to 20 windows sits around $10,000 to $18,000. Larger villas and character homes climb past $19,000 once you count window sizes, timber condition and access. Doing the whole house at once always prices better per window than doing two rooms at a time.

Timber frames need checking before anything is quoted

A retrofit only works if the frame is sound and deep enough to take the unit. On timber joinery we probe the sill and the bottom rail first. Soft timber there has to be repaired or scarfed before glass goes anywhere near it, otherwise you have put a twenty five year unit into a frame with five years left.

We quote the repair and the retrofit together so there are no surprises halfway through. On a full house lot we take the sashes back to the bench, do the timber work, glaze, repaint and refit, which gives a far better finish than trying to do it all in place.

Getting the glass spec right for a Wellington house

The standard build is 4mm glass, a 12mm gap and 4mm glass. From there you choose. A Low E coating cuts heat loss substantially for a modest cost per square metre. Argon fill improves it again. Laminated glass on the outer pane cuts noise, which matters under the Wellington Airport flight path through Miramar, Strathmore and Rongotai, and on the main road frontages in Newtown and Kilbirnie.

Wind zone matters too. On an exposed hill site the unit may need thicker glass to meet the pressure, which adds weight and can change what the old sash will carry. We check that before we order instead of after.

Consent, and what the rules really say

Retrofitting glass into existing frames on an existing home is like for like work and it is exempt under Schedule 1 of the Building Act. You do not need a consent and you do not pay council fees.

That changes if you enlarge the opening, alter structure, or the work forms part of a larger consented renovation. Since the 2021 H1 energy efficiency update, consented residential work has to be double glazed anyway.

Retrofit Double Glazing at a glance

Aluminium retrofit

About $550 to $850 a window

Timber retrofit

About $800 to $1,250 a window

Aluminium insert

About $980 to $1,480 a window

Small home, 5 to 10 windows

Around $6,000 to $10,000

Family home, 10 to 20 windows

Around $10,000 to $18,000

Standard unit

4mm glass, 12mm gap, 4mm glass, Low E and argon optional

Time on site

One to three days for most homes

Consent

Exempt as like for like work under Schedule 1