Double hung windows suit openings where a window cannot project outward, which makes them the practical choice above kitchen benches, beside walkways and decks, and in heritage properties where the proportions matter. Their main limitation is sealing. Because the sashes slide rather than compress, they rely on brush seals and cannot be made as airtight as an awning or casement window, which affects weather resistance and noise.
What is a double hung window?
A double hung window has two sashes sitting one in front of the other in the same frame, both sliding vertically. Raising the bottom sash or lowering the top one opens the window without anything projecting into the room or out beyond the wall.
The name refers to how the sashes are hung, meaning suspended and counterbalanced, rather than to any particular material or appearance.
How it differs from a single hung window
In a single hung window only the bottom sash moves and the top sash is fixed in place. It costs less and has fewer moving parts, but it gives up the two features that make double hung useful: ventilation through the top sash alone, and the ability to tilt both sashes in for cleaning.
Where a supplier quotes a hung window without specifying, it is worth asking which it is.
How double hung windows work
Three components make the sashes move and stay where you leave them.
Balances counteract the weight of each sash. Australian aluminium windows typically use spiral balances, a spring loaded rod concealed in the jamb, or block and tackle balances, a spring and pulley arrangement. Older timber windows used cords running over pulleys to counterweights inside the frame. Without a working balance the sash simply drops.
Jamb tracks guide the sash as it travels and hold it in alignment.
Pile or brush seals sit in the tracks and along the meeting rail where the two sashes overlap, sealing against draught and rattle while still allowing the sash to slide past them.
That last point is the source of both the style’s convenience and its main limitation, and it comes up repeatedly below.
The advantages
Nothing projects
This is the reason double hung windows exist, and it is decisive in several situations. The sash travels within the frame, so nothing swings inward into the room or outward into the space beyond.
That matters beside a walkway, a deck, a balcony or a narrow side passage, where an awning window would project into the path of someone walking past. It matters above a kitchen bench, where an outward opening window needs an awkward reach across the bench to a winder. And it allows external fly screens and security screens to sit close to the glass.
Ventilation you can direct
Open both sashes and warm air leaves through the top gap while cooler air enters at the bottom. That convection effect is genuinely useful in Australian summers and is something no single opening window can replicate.
It also means you can ventilate through the top sash alone with the bottom closed. On an upper floor with children in the house, that is a meaningful safety option rather than a technicality.
Heritage appearance
Sydney has extensive heritage conservation areas where the external appearance of windows is controlled, and double hung is the traditional form across much of that housing stock. Modern aluminium versions can approximate the original proportions while delivering performance and maintenance characteristics timber cannot.
Cleaning from inside
Many double hung windows tilt in, allowing both faces of both sashes to be cleaned from within the room. In an apartment or on an upper floor that is a practical advantage over any window that must be reached from outside.
Full height screens
Because nothing projects, fly screens and security screens fit externally across the full opening. On awning windows screens must sit internally, which some people find visually intrusive.
They suit tall narrow openings
An awning window of the same area in a tall narrow opening is an awkward proportion. A double hung fits naturally.
The disadvantages
Sealing is the significant one
A double hung sash slides past its seals rather than compressing into them, so it relies on pile or brush seals in the jamb tracks. Brush seals resist air movement but never fully block it.
An awning or casement sash compresses into a gasket when it closes, forming a continuous airtight line. That difference is structural and cannot be engineered away in a sliding sash.
The consequences are draught, reduced water resistance under wind pressure, and noise. Air leakage carries sound, so a double hung window will generally measure worse acoustically than an awning window with identical glass. We explain the mechanism in our article on acoustic seals in double glazed windows.
If noise is your primary concern this matters, and the glass has to work harder to compensate. See our soundproof windows range for how acoustic performance is specified across window types.
Only half the opening ventilates
One sash always sits behind the other, so the maximum clear opening is roughly half the window area. An awning window of the same size opens far more of its area to airflow.
Moving parts wear
Balances, tracks and pile seals are all consumables. Balances lose tension, pile compresses and degrades under Australian ultraviolet, and tracks accumulate grit.
None of it is dramatic, but a double hung window needs more attention over twenty years than a fixed or awning window does.
Exterior cleaning, unless the sashes tilt
Where the sashes do not tilt in, the outside face of the upper sash is difficult to reach from inside. Worth confirming before ordering, particularly above ground level.
Weather exposure
Under driving rain with wind behind it, brush seals allow more water ingress than compression seals. Australian windows carry water penetration resistance ratings tested under AS 2047, and it is worth comparing those figures rather than assuming, particularly on exposed elevations.
Grit and salt
Sliding sashes drag their seals across whatever is in the track. Near the coast, across the eastern suburbs, Northern Beaches and Sutherland Shire, tracks accumulate salt and sand and hardware corrodes faster than on a hinged window.
How double hung compares with the alternatives
Against awning windows, double hung loses on sealing, acoustic performance, weather resistance and ventilation area. It wins on not projecting, on directional ventilation, on heritage appearance and on external screening. For a bedroom on a quiet street the difference is modest. For a room facing an arterial road the awning window is clearly better.
Against sliding windows, the comparison is closer, since both slide and both use brush seals. Sliding suits wide openings and double hung suits tall ones, and double hung offers the top and bottom ventilation option a horizontal slider cannot.
Against casement windows, casement seals best of all and offers the largest clear opening, but it needs the most swing space and is the most exposed to wind catching the open sash.
Against fixed windows, fixed glazing seals perfectly and ventilates not at all. Where a window exists for light rather than airflow, fixed is both cheaper and better performing.
How to clean a double hung window
Cleaning is one of the practical advantages of the style, provided the sashes tilt.
If your sashes tilt in, release the tilt catches on the sash, usually at the top of the bottom sash, and rotate the sash inward until it rests horizontally. Both faces are then reachable from inside the room. Repeat for the top sash. Return each sash upright until the catches click home before operating the window.
If they do not tilt, the inside faces are straightforward and the outside of the upper sash needs external access. This is worth knowing before you order, particularly above ground level.
Do not neglect the tracks. Grit in the jamb tracks causes both wear and binding, and it is the single most common reason a double hung window becomes stiff. Track cleaning, lubricant choice and seal care are covered in our guide to fixing a loose or tight double hung window sash.
Twice a year is sufficient for most homes, more often near the coast or on an unsealed road.
Where double hung windows are the right choice
Heritage properties and conservation areas, where external appearance is controlled and the traditional form is required or expected.
Above kitchen benches and behind fixed furniture, where reaching a winder across a bench is awkward.
Beside walkways, decks, balconies and narrow side passages, where a projecting sash would obstruct.
Upper floor bedrooms, where top sash ventilation with the bottom closed is genuinely useful.
Apartments, where tilt in cleaning avoids external access.
Tall narrow openings, where the proportions suit.
Where another window type is better
Rooms facing significant noise, where an awning or casement window with the same glass will measure better because it seals by compression.
Highly exposed elevations, where driving rain and wind pressure make water resistance the priority.
Where maximum ventilation area matters, since a double hung opens only about half its area.
Very wide openings, which suit sliding units or a combination of fixed and awning windows.
Safety and compliance in New South Wales
Double hung windows are among the window types most commonly caught by mandatory window safety device requirements in New South Wales strata buildings, because the sill is often low and the sash slides up to create a large clear opening.
If your property is a residential strata scheme, check whether a compliant device is required before specifying, and note that a standard cam lock does not satisfy the requirement. The thresholds, the hardware and who is responsible are set out in our article on choosing locks for double hung windows.
Specifying a double hung window well
If the style suits the opening, a few decisions determine how well it performs.
Glass does more than the frame. Since the sealing is inherently limited, the glazing carries more of the thermal and acoustic load. Double glazing and laminated glass both deliver more improvement in a double hung window than they would in a well sealed awning window.
Check the water resistance rating under AS 2047 for the specific suite rather than assuming all double hung windows perform alike. They do not.
Confirm whether the sashes tilt in if the window is above ground level.
Specify quality seals and expect to replace them. Pile is a consumable, and a double hung window with fresh seals performs close to new.
Specify compliant safety devices where the property is strata or where children have access to an upper floor window.
Choose corrosion resistant hardware near the coast, since sliding sashes and small window hardware suffer more than door hardware does.
Our double hung windows are manufactured in Villawood, tested to AS 2047, and available with double glazing, acoustic glazing and compliant safety devices.
Frequently asked questions
What is a double hung window?
A window with two sashes in the same frame, both sliding vertically. Nothing projects into the room or beyond the wall when it opens, and the two sashes can be opened together to ventilate through the top and bottom at once.
What is the difference between single hung and double hung?
In a single hung only the bottom sash moves and the top is fixed. In a double hung both operate, which allows ventilation through the top sash alone and makes tilt in cleaning of both sashes possible.
Are double hung windows good for Australian conditions?
They suit heritage properties, openings where nothing can project, and situations where directional ventilation is useful. On exposed elevations or where noise is a priority, an awning or casement window seals better and performs better.
Do double hung windows leak?
They resist water less well than compression sealed windows under wind driven rain, because sliding sashes rely on brush seals. Australian windows carry water resistance ratings tested under AS 2047, so compare the figures for the specific suite.
Are double hung windows noisy?
They generally measure worse acoustically than an awning window with the same glass, because air leakage past brush seals carries sound. Upgrading the glazing compensates to a degree.
Can double hung windows be double glazed?
Yes. Because the frame sealing is inherently limited, the glazing carries more of the performance, so double glazing often delivers a more noticeable improvement here than in a better sealed window type.
How do you clean double hung windows?
If the sashes tilt in, release the tilt catches and rotate each sash inward to reach both faces from inside the room. If they do not tilt, the outside of the upper sash needs external access. Keeping the jamb tracks clear matters as much as the glass, since grit is what makes a sash stiff.
Why do double hung windows stop staying up?
The balance has failed. Spiral balances lose tension over time and block and tackle balances can have cords break. Replacement is the fix, and it is not DIY work because balances store considerable spring energy.