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    The Pitfalls of Skylight Condensation:
    How to Avoid it

    arrow Back to blog 27th May 2019

    The internet is awash with complaints and negative reviews from owners of skylights – not acquired from Sunsquare – regarding the levels of skylight condensation formed on the glass surface, creating excess moisture that exists and festers within living and working environments.

    The internet is awash with complaints and negative reviews from owners of skylights – not acquired from Sunsquare – regarding the levels of skylight condensation formed on the glass surface, creating excess moisture that exists and festers within living and working environments.


    The problem is that condensation on skylights doesn’t just exist on the glass surface. In some cases, warm, moist air can escape from living or working spaces below and reach a roof’s cladding or flashing. You’ll then see condensation from skylight dripping downwards back into rooms below from between the frame and the opening of your rooflight, creating the unwanted illusion of a roof leak. This is also known as cold bridging.

    What causes skylight condensation?

    Skylight condensation occurs most frequently when warm, moist air rises to the ceiling and comes into contact with the colder glass surface that’s influenced by outside temperatures and weather conditions. There is also a danger that skylight condensation can form on more than just the glass pane.

    The root cause of skylight condensation is the conversion of vapour into liquid. When pockets of air become saturated with moisture, it is released in the form of water droplets. The condensation is easily identifiable by the mist-like conditions that form and cloud the interior glass pane of any low-value, poorly manufactured rooflight.

    We contribute more water vapour or humidity into our internal atmosphere by doing the simplest things; all of which can accrue on roof windows and skylights as condensation, including:

    • Cleaning
    • Showering (the main culprit for bathroom skylight condensation)
    • Cooking
    • Everyday breathing
    • Human perspiration

    Signs of skylight condensation to look out for

    There are several tell-tale signs of condensation within homes and workplaces that may be caused by defective rooflights:

    • Peeling or bubbling wall paint
    • Skylight condensation mould or mildew on walls, window seals and baseboards
    • Worsening wall and attic insulation
    • Deteriorating floor tiles and furniture
    • Structural integrity of wood between outside walls is beginning to rot

    How come skylight condensation occurs primarily in the winter months?

    Skylight condensation problems are most prevalent in the colder, winter months due to the greater extremes in temperature between the internal pane of a skylight and an external pane of a skylight.


    Warm air is heavier than cold air because it carries more moisture. During the winter months, homes and workplaces have central heating systems to maintain warm, comfortable temperatures. However, when this warm, moist air rises and contacts a cool surface, such as a skylight glass pane, the moisture immediately forms condensation on the cooler surface.


    When the outside temperatures are somewhat milder and the temperature difference between outside and inside a property is that much smaller, condensation is much less likely to occur.


    Extremes in temperature between internal and external panes of Sunsquare skylights is not an issue. As each rooflight is thermally broken, they help properties stay warmer, more energy efficient and, crucially in terms of skylight condensation, drier too. Thermal breaks prevent heat generated internally from transferring to external panes via direct transfer through the skylight’s framework. This allows the inner pane of a rooflight to stay as warm as possible, with minimal influence from the external pane that’s exposed to winter’s worst.

    How to prevent skylight dripping condensation

    Here are some simple steps you can take to better ventilate your home and reduce the possibility of condensation from skylight dripping down onto walls, floors and furniture:

    • Use internal exhaust fans more frequently to expel hot, moist air outside.
    • Ensure tumble dryers and gas appliances adequately vent moist, warm air outside.
    • Keep window blinds and shades open to encourage warm air to circulate around your windows.
    • Open your windows in living or working areas daily for improved air circulation. Sunsquare’s Aero Electricrange of skylights can offer simultaneous natural light, ventilation and roof access at the touch of a button for homes and workplaces, minimising skylight condensation risk in the process.
    • Keep loft vents open, allowing hot air to rise and release it outside rather than settle onto rooflight panes.

    How to fix skylight condensation

    Already suffering from the effects of skylight condensation? Follow these six simple skylight condensation solutions to bring an end to damp, musty interiors caused by your rooflight:

    • Ensure your skylight is fitted and fully insulated for your property, preventing small gaps forming in the outer panels of your rooflight.
    • Cover any cracks or holes in skylight joints or corners with silicone caulk.
    • Gain access to your skylight’s roof flashing.
    • Remove all dirt, moisture, leaves and any other debris that has settled around the flashing, unwittingly creating a dam for condensation and water to seep indoors.
    • Ensure your skylight’s weather stripping is in good condition – replace it if necessary.
    • Redo steps three to five annually as part of preventative skylight condensation maintenance – sooner if you live in a rural or heavily wooded area.

    How Sunsquare’s products defy skylight condensation problems

    Sunsquare’s skylights are not only BSI Kitemarked for weather tightness and wind loading, they are Kitemarked for air permeability too.


    Every skylight that we design, manufacture and install for our clients is thermally broken using multiple polyamide insulating sectors. No comparable flat roof skylight available on the market is capable of keeping the interior glass pane warmer and drier, with no chance of skylight condensation between glass panes. Our optional upstands are regularly purchased by clients to ensure that every Sunsquare skylight fits and fits well into the roof membrane.


    A Sunsquare upstand makes the skylight installation process quick and painless, but it is also designed to offer supreme energy performance and 0% condensation risk. Each upstand is built from a unique sandwich panel using highly sophisticated insulating foam and is tested to handle the most demanding weather scenarios.


    At Sunsquare, we’ve been innovating the UK skylight industry since 2004. Our bespoke, pioneering designs not only provide stunning architectural statements, they break the mould for safety standards too.


    For homeowners and businesses seeking a rooflight that offers abundant natural light without the risk of your inner glass becoming all too easily influenced by external temperatures, let us advise you on the best possible skylight solution for your project. Our senior sales team offers friendly and experienced guidance to make your rooflight aspirations a stunning reality.

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    Call us on +44 (0)1284 723377

    Email sales@sunsquare.co.uk

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