Window Installation in Dunedin

The building code asks more of a window here than it does further north, and a lot of quotes still miss it. Dunedin sits in H1 climate zone 5. Zones 5 and 6 need a minimum window R value of R0.50, against R0.46 for the North Island and the top of the South. R0.50 cannot be reached with plain double glazing in a standard aluminium frame. It needs Low E glass in a thermally broken, uPVC or timber frame. That is the floor, not the upgrade.

What R0.50 actually rules out

Under the schedule method in H1, a window in zone 5 has to hit R0.50 as a whole unit, frame included. Standard aluminium with clear double glazing lands nowhere near it. Even Low E glass in a plain aluminium frame only reaches the old transitional figure of R0.37.

So on any consented residential work in Dunedin the frame has to do some of the insulating. In practice that means thermally broken aluminium, uPVC or timber, paired with Low E and usually argon. If a quote you have been given specifies plain aluminium for a consented job, it does not comply, and we will tell you that before you sign it.

The install matters more than the joinery

Almost every leaking window we get called to was installed badly rather than made badly. Water enters at the head because the flashing was cut short or a bead of sealant was run where a hook and hem was needed. Air moves through the reveal because the perimeter gap was packed with offcuts and never sealed.

We set the unit on packers, check it square and plumb both ways, fix it at proper spacings, seal the perimeter air gap and fit the head flashing with the right upstand. Then we make good the linings and take our mess with us.

Consent, and where the line sits

Replacing a window like for like in an existing home is exempt work under Schedule 1 of the Building Act. No consent, no council fees, no waiting on a processing queue. That covers most of what we do.

Consent is needed once the opening gets bigger, structure changes, or the work forms part of a larger consented job. New builds and additions are consented anyway, which is exactly when the R0.50 requirement bites.

Heritage and character joinery

Dunedin has more surviving Victorian and Edwardian housing than anywhere else in the country, and a lot of it sits in areas where the exterior look is protected or simply worth protecting. Dropping aluminium into a villa opening is usually the wrong answer even where it is allowed.

New timber joinery profiled to match, or a retrofit into the sashes that are already there, keeps the street elevation intact. We quote both and explain what each does to the thermal performance.

Window Installation at a glance

Frame options

Thermally broken aluminium, uPVC, timber, standard aluminium where exempt

Code minimum here

R0.50 for windows and doors, climate zones 5 and 6

What meets it

Low E glass in a thermally broken, uPVC or timber frame

Safety glazing

NZS 4223 for doors, wet areas and low level glass

Weathering

Head flashing with correct upstand, sealed perimeter air gap

Consent

Like for like replacement is exempt under Schedule 1

Typical timeframe

Four to five weeks from measure to install on made to order joinery