Double glazing timber sashes and casements in Wellington
Double glazing wooden windows can mean new glass in the sashes you have now, or new timber sashes made to fit the old frames. Before you pick one, find out whether Wellington City's District Plan lists the house as a heritage building or places it in a heritage area or Character Precinct, since each has rules of its own. Still deciding whether the frames are worth keeping? Weigh up the choices in double glazed windows for older Wellington homes.
Ask for a quote
Glass into the old sashes, or new sashes made to fit
In Lower Kelburn, one of the Character Precincts, Wellington City Council's design guidance describes houses mostly built between 1920 and 1930, with wooden casements or sashes and, often, bay windows. There are two ways to double glaze windows like those without losing the timber or the frames.
Option one
New glass in the sashes you have now
The single glazing in each sash is swapped for double glazed units. Under NZS 4223.3:2016, a low pane close to the floor may need to be safety glass when it's replaced.
Option two
New timber sashes made for the old frames
The frames stay, and new sashes are made to hold double glazed units. Ask about this route if a sash has rot or old repairs. Where heritage or precinct rules apply, check with the council before any are made.
A draughty sash needs seals as well as glass, so check they're itemised on the quote. For an aluminium insert in the timber surround, read up on retrofitting Wellington windows with double glazing.
One Wellington glazing firm's published list (February 2026, incl GST) prices new glass in timber frames at $800–1,200 per glass unit, and a new timber sash made for the existing frame at $850–1,250 per glass unit. The same firm says counterweighted sashes and kept leadlights cost more. They aren't the only things that can add to a double glazing price in Wellington.
Low-E, leadlight and obscure glass under the clear-glass rule
Two heritage rules in Wellington City's District Plan are written for double glazing, HH-R5 for a listed heritage building and HH-R18 for a building in a heritage area. Both describe a clear single-glazed pane swapped for a clear double or triple glazed pane in the existing frame.
The plan doesn't say what clear means.
The insert-window guide from WGANZ, the Window & Glass Association NZ, lists clear and low-E units separately, and most retrofit units are low-E.
As the rules are written, the old pane and the new one both have to be clear, so leadlight, coloured and obscure glass fall outside them. Don't count on either rule covering a low-E unit. Ask the council's resource consents team before anything is ordered.
Have the glass named in writing on the quote, so the council can see exactly what's going in.
Ask for a quoteWhich heritage or precinct rule applies to your house
Wellington City's District Plan lists heritage buildings individually. It also has 43 heritage areas, and classes the buildings in them as contributing or non-heritage. The areas that take in housing include Aro Valley Cottages, Tarikaka Street Settlement, Armour Avenue, Doctors' Common, Elizabeth Street, Moir Street, Porritt Avenue, Ascot Street and Truby King (Manchester and Duncan Terraces).
On a listed heritage building, a controlled consent has to be granted and isn't notified, but the council can set conditions on design, appearance and heritage fabric.
Building consent and resource consent
Window work on a one- or two-storey house rarely needs a building consent. Whether it needs resource consent depends on the District Plan. If your home is a listed heritage building, or in a heritage area or one of Wellington City's Character Precincts (Thorndon, Mt Victoria, Mt Cook, Aro Valley, The Terrace, Lower Kelburn, Newtown or Berhampore), check the District Plan before you change windows. Swapping clear single glazing for clear double glazing in the existing frames has its own simpler rule for heritage buildings and heritage areas. The plan doesn't define clear glass, and most retrofit units are low-E, so a low-E unit isn't confirmed to qualify. Changing the frames themselves is treated as an alteration. Wellington City Council's resource consents team can confirm what applies to your address.
Listed heritage building (Wellington City)
Rules
HH-R5, HH-R7
Clear double glazing in the existing frames
Controlled (resource consent is needed, and it must be granted)
New frames or other alterations
Restricted discretionary
Contributing building in a heritage area
Rules
HH-R18, HH-R19
Clear double glazing in the existing frames
Controlled (resource consent is needed, and it must be granted)
New frames or other alterations
Restricted discretionary
Non-heritage building in a heritage area
Rules
HH-R18
Clear double glazing in the existing frames
Permitted
New frames or other alterations
Check the District Plan
House in a Character Precinct
Rules
MRZ-PREC01-R5
Clear double glazing in the existing frames
Unresolved. The rule has no glazing carve-out
New frames or other alterations
Restricted discretionary
Porirua scheduled heritage item
Rules
HH-R1, HH-R10
Clear double glazing in the existing frames
Ask the council. There's no glazing-specific rule, and it isn't confirmed whether HH-R10 covers new glass
New frames or other alterations
Ask the council. Heritage alterations are restricted discretionary under HH-R10, but it isn't confirmed that new frames count
Kāpiti Coast scheduled historic building
Rules
HH-R2, HH-R6
Clear double glazing in the existing frames
Ask the council. There's no glazing-specific rule, and it isn't confirmed whether HH-R6 covers new glass
New frames or other alterations
Restricted discretionary (HH-R6)
Hutt City, Upper Hutt, Wairarapa
Rules
Not stated
Clear double glazing in the existing frames
Ask the council
New frames or other alterations
Ask the council
Elsewhere in Wellington City
Rules
None of these
Clear double glazing in the existing frames
Check the District Plan. No heritage or precinct rule applies
New frames or other alterations
Check the District Plan. No heritage or precinct rule applies
Only clear glass is named in HH-R5 and HH-R18. With no definition of clear glass in the plan, and most retrofit units being low-E, a low-E or tinted unit isn't confirmed to qualify. Check with Wellington City Council. Building consent is another matter, and Schedule 1 usually exempts window work on a one- or two-storey house.
Rule IDs as at September 2026.
Mention the house's heritage status in your enquiry, and we'll pass it on with your details.
Ask for a quoteChanging windows in a Character Precinct
Wellington City's eight Character Precincts manage pre-1930 buildings, and none of their rules mentions double glazing or window replacement.
Maintenance and repair, meaning making good decayed or damaged fabric with like materials of similar design and appearance, is permitted (MRZ-PREC01-R1). An alteration needs resource consent as a restricted discretionary activity (MRZ-PREC01-R5), and so does demolishing a pre-1930 building or part of one (MRZ-PREC01-R4). In a precinct, demolition includes removing features from a primary elevation, which covers bay windows and window-to-wall ratios.
Swapping to frames in another material, or ones that open a different way, is an alteration. On a pre-1930 street-facing elevation, the swap could count as part demolition too. Whether new glass in the existing frames needs consent is unresolved. It isn't clearly maintenance and repair, no rule deals with it, and we haven't found a council statement or decision saying it's free of consent.
Inside a precinct, talk to the council about consent first, whether you're keeping the frames or replacing windows in a Wellington house.
Built before 1930
82%
4,507 of 5,492 properties in the old District Plan's six pre-1930 character areas
From a 2019 review for Wellington City Council. It isn't a count for the whole city.
Heritage consent fees can be refunded
Wellington City Council can refund resource consent fees when a consent was needed under its heritage rules and the work protects heritage values. A private owner can get back up to $2,500 per consent, or $3,000 with an eligible pre-application meeting.
The money comes from a $50,000 pool each year. It pays back fees, not the cost of the windows, and the council's refund page doesn't mention Character Precincts.
Refund limits as at September 2026.
You can have the windows priced while you check the consent rules.
Ask for a quoteTimber sash and heritage consent questions
Can old wooden windows be double glazed?
They can. Double glazed units go into the old sashes, or new timber sashes are made to fit the frames. An aluminium insert in the timber surround is another way of retrofitting double glazing.
Does double glazing timber windows cost more than aluminium?
Per glass unit, it does on a Wellington glazing firm's February 2026 list. New glass in timber frames is $800–1,200 per glass unit there, against $550–850 per glass unit in aluminium, incl GST.
Are double glazed sash windows worth it?
They can be, if keeping heat in is the aim. With standard double glazing, MBIE's H1/AS1 table rates a timber window at R0.41, and WGANZ puts single-glazed timber at roughly R0.19. Weigh that against a quote for your own sashes.
Does changing windows in Thorndon or Mt Victoria need resource consent?
It can. Both have a Character Precinct, and inside one, new frames in another material or opening style need resource consent, while new glass in the old frames is unresolved. Listed heritage buildings and heritage areas have separate rules.
What do heritage windows cost?
On a Wellington glazing firm's February 2026 list, a new timber sash made for the existing frame is $850–1,250 per glass unit, incl GST. If the work needs resource consent, the council's fees come on top of the double glazing price.
Ask for a price on keeping your timber windows
If the frames are staying, with the old sashes or new ones, choose "New glass" on the form. We'll pass your details on so a local installer can measure up and quote.