About PaneWise

What you will find here

• What double glazing, retrofit and secondary glazing cost in 2026, per m² and for a whole house: see retrofit cost and replacement cost.
• What each option saves in your city’s climate, and how long it takes to pay back: use the calculator or read is it worth it?
• When you need a building consent (usually not, for a house of up to two storeys) and what the Building Code’s H1 rules mean for windows.

What we do

Double glazing is sold on comfort and on savings. The comfort is real; the savings depend on your city, your windows and how you heat. We built a model that works this out from public data, so that you can see the numbers before a salesperson does.

Independence

We do not sell windows, glass or finance, and we take no referral fees or commissions. No glazier has paid to be mentioned. Prices are mid-points of published ranges, not quotes from a partner.

Corrections

If you find a number that looks wrong, or a rule that has changed, tell us and we will check it against the source and correct the page. Every page shows the date it was last checked.

See methodology and data for how the numbers are made.