Privacy glass and daylight: planning obscure double glazing

The trade-off between privacy and light

Every privacy decision on a window gives something up. Clear glass gives light and view but no privacy. Obscure glass scatters light and reduces detail, with the amount of daylight and obscuring depending on the product. It also reduces your outward view. An opaque covering can provide privacy when correctly fitted and closed, while sheer fabrics and edge gaps can still reveal the room. Closing an opaque covering also reduces daylight. The goal is to find the right mix for each opening rather than applying one answer to the whole house.

When you replace windows with double glazing, privacy is a good thing to rethink, because you are choosing the glass for each opening anyway. A bathroom window that has always had a frosted film could have obscure glass made into the sealed unit instead. A bedroom that faces the street might need obscuring only on its lower half. A living room window that looks at a neighbour's new second storey might need a different answer from the one that suited it ten years ago.

This guide is about working out what each opening needs. The broader question of which glass make-up suits your climate and orientation is covered in the energy efficient glass page. Privacy glass can usually be combined with those choices, although it changes some of the performance values, which we return to below.

Why privacy is different by day and by night

How well someone can see through a window depends mostly on which side is brighter. During the day, outside is usually much brighter than inside. A person on the street sees a lot of reflected sky on your glass and not much of the room behind it. You, standing inside, look out easily. At night the situation reverses. With lights on inside and darkness outside, the room is lit up behind clear glass, and anyone outside can see in.

This is why so called one way glass is misleading in a house. Reflective and heavily tinted glass exaggerate the daytime effect, making it harder to see in on a bright day. They do nothing useful after dark, and they reduce the daylight reaching the room at all hours. If someone offers you a glass that guarantees privacy while keeping a clear view out, ask how it performs at night with the lights on.

For night privacy, test the proposed glass with indoor lights on and someone at the distances they will normally stand from the window. Obscuring products vary in how much detail and silhouette remains visible. An appropriately fitted opaque covering may still be needed. Many people settle on clear glass plus a covering in living areas, and obscure glass in bathrooms, ensuites and toilets where a covering is inconvenient or gets damp.

Privacy options inside a double glazed unit

In a sealed unit, one of the two panes can be an obscuring glass, with the other pane chosen for its own job, such as a coated pane for thermal performance. The common types are:

• Patterned or textured glass. Rolled with a surface pattern that scatters light and blurs shapes. Patterns range from light textures that still show outlines to heavier ones that hide almost everything.
• Acid etched or sandblasted finishes. A smooth, even frosted look. The level of obscuring depends on the product.
• Translucent laminated glass. Two panes bonded with a translucent interlayer. It gives an even frosted appearance and brings the properties of laminated glass, which the Australian Government's Your Home glazing guide describes as holding shards in place if it breaks.
• Toned and reflective glass. These change how much light and solar heat pass through and reduce daytime visibility, but they do not provide night privacy.

Two practical questions apply to all of them. First, which face of the unit does the pattern, etch or interlayer sit on? A textured face on the outside of the unit collects dust differently from a smooth one, and a textured face inside the room can hold grease and fingerprints. Second, how does the obscuring glass affect the rest of the specification? Ask the supplier to confirm the glass make-up in writing, pane by pane.

Films applied after installation are sometimes suggested as a cheaper route. On sealed units, check with the window supplier first. Some films change how the glass absorbs heat, and some manufacturers restrict their use or exclude it from the unit warranty.

Map the sightlines before choosing a glass

The most useful privacy work happens outside the house, not in a showroom. Check viewpoints from your own property and public areas, such as the footpath or driveway. Estimate views from neighbouring decks or upper windows without entering their property; obtain permission for any closer check. From each point, look back at the window and note what you can see of the room.

Then do it again after dark with the lights on in the room. You may find a window you worried about is only exposed at night, which a blind solves, while another one you never thought about gives a clear line of sight from a neighbour's kitchen into your bathroom.

Note the height at which the view is a problem. From the street, a bedroom window is often exposed at standing height but not above head height. A bathroom window may need obscuring across its full height if a neighbour's upper floor looks down on it. Knowing the height lets you ask for obscuring only where it is needed, keeping clear glass above for sky and light.

Remember that an open window has no privacy glass at all. If a bathroom window must be open for ventilation while the room is in use, consider which part of the window opens. An awning high in the frame, above an obscure fixed pane, may preserve more privacy while opening, but check the actual sightline from higher neighbouring windows too. The opening styles guide covers these combinations.

How much light you keep

Obscure glass does not have to make a room dark. Most obscuring glass still passes a large share of visible light but scatters it, so the room is lit evenly rather than by a direct beam. Some people find the scattered light more pleasant in bathrooms because it removes glare and harsh shadows.

The measure to ask about is visible transmittance. The Window Energy Rating Scheme describes it as the amount of visible light transmitted, expressed as a number between 0 and 1, where higher numbers mean more light. Whole-window ratings include the effect of the frame, so a window with a wide frame and small glass area lets in less light than the glass figure alone suggests. Our guide to window energy ratings explains how to read these figures.

Toned and reflective glass are different. They cut visible light as well as solar heat, and Your Home notes that if visible light transmittance is too low a room can become dark enough that you switch lights on more. Use them where solar heat is the actual problem, not as a privacy fix.

Partial obscuring is a good compromise in many rooms. A clear upper section brings in sky light and a sense of openness, while an obscure lower section blocks the view in. Ask the supplier whether the frame system allows a transom or a divided sash for this.

How to judge a sample properly

Obscure glass looks different in a showroom than in your house. Showroom samples are often small, lit from above and viewed at arm's length. In your window the glass is larger, lit from behind by the sky, and viewed from across the room and from outside.

Ask the supplier to demonstrate a safely supported sample at the opening or provide a suitable sample for ground-level viewing. Avoid handling large loose panes, climbing or balancing a sample against glass. Look at it in the morning and late afternoon, when the light changes. Check what a person standing close behind the glass looks like from outside, because obscuring that hides a room at a distance can still show a clear outline of someone right against it.

If a physical sample is not available, ask the supplier for the product name so you can look up its description, and ask whether a similar glass is installed somewhere you can view. A photo on a screen is a poor guide to how much a pattern hides.

Bathrooms, toilets, front doors and sidelights

Bathrooms and toilets are where obscure glass is most often chosen, because blinds in wet areas get damp, stained and mouldy. The same moisture affects the glass. A heavily textured surface on the room side can hold soap film and water marks, and it takes more effort to clean than a smooth surface. If you are choosing between patterns, ask which face of the unit the texture sits on, and consider a smooth faced obscure option near a shower or bath.

Ventilation matters too. An obscure fixed window keeps the room private but does nothing for steam. Plan for an opening section, or rely on an exhaust fan, and think about what can be seen through that opening when it is open.

Front doors and the narrow sidelights beside them are another common privacy point. People like to see who is at the door without the visitor seeing into the hallway. A lightly obscure or textured glass in a sidelight lets you see a shape and movement while blurring detail. Safety glass is commonly required in and around doors, so ask the supplier which obscure products are available in a suitable safety glass for that location.

Laundries, garages and home offices facing a neighbour are good candidates for partial obscuring rather than full. In these rooms, keeping clear glass above eye height often makes a noticeable difference to how bright and open the room feels.

Hypothetical example: three rooms, three answers

In a single storey house facing a busy footpath, the main bedroom window is exposed at standing height from the street, and a neighbour's new second storey overlooks the ensuite from the side.

The bedroom keeps clear double glazing, because a blockout blind is used every night anyway and the owners want the morning light and view of the garden. For the ensuite, the supplier demonstrates a safely supported translucent sample with the planned lighting, including night-time backlighting and a person near the glass. The owners consider a small upper awning, but only select that arrangement after its open position has been checked against the higher neighbouring sightline. They retain an opaque covering if the selected product leaves a visible silhouette. The front living room gets an obscure lower section to head height with a clear transom above, which keeps the room private from the footpath during the day while still showing the sky.