Skylights are a brilliant way of providing your home with a large amount of ventilation and natural daylight, but are they energy efficient?

When it comes to making your home sustainable, natural available resources such as the sun and wind should be utilized to their maximum, which is where skylights and roof windows can help. Ensuring these products are as energy efficient as possible can save energy; reduce heating, cooling, and lighting costs; and improve the comfort of your home.

As stated by The U.S. Department of Energy, “daylighting such as the use of roof windows or skylights is one building strategy that can save money for homeowners and businesses. Highly efficient, strategically placed windows maximize the use of natural daylight in a building, lowering the need for artificial lighting without causing heating or cooling problems.”

To ensure your skylight or roof window is as energy efficient as it can be, there are a number of points to consider.

Glass Selection

Selecting the right type of glass is essential when thinking about your skylight or roof window’s energy efficiency. If you choose the wrong type of glass issues can occur, for example, selecting glass with a high solar heat gain may keep you warm in the winter, but could trap in heat during the summer months. Thinking about where your skylight or roof window will be placed on your home will help prevent this problem and will increase your home’s energy efficiency.

If you’re looking for an energy efficient product you will also need to make sure it has a low U factor. The U factor is how skylight performance is measured in terms of transmitting non-solar heat energy, with a lower U factor meaning the skylight or roof window is more energy efficient.

Energy efficient skylights should be double-pane, and you might want to consider coatings on the window to limit heat gain, but remember that heat gain can be energy-saving during the winter. Adding ventilation capabilities to your skylight can improve indoor air quality and reduce the possibility of mould. Ventilating skylights are energy efficient in kitchens and bathrooms, with some skylights, such as Glazing Vision’s Vision Vent, Sliding Over Fixed, and Sliding Over Roof skylights, have built-in sensors that close when they detect rain or moisture on the outside.

The most energy efficient type of glass for double and triple glazing is low emissivity (low-E) glass. Low-E glass has a microscopically thin coating of metal oxide on one of the internal glass surfaces which reflects heat back into the home but still lets in the light from outside, and when combined with argon gas in the cavity and warm edge spacer bars, the glass is even more energy efficient. Our team of experts will be able to help you select the perfect glass for your skylight or roof window.

Solar Heat Gain Coefficient (SHGC)

You will also need to look at the solar heat gain coefficient (SHGC) which is the fraction of solar radiation admitted through a window, door, or skylight, either transmitted directly and/or absorbed, and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits and the greater its shading ability. A skylight or roof window with a high SHGC rating is more effective at collecting solar heat during the winter. A skylight or roof window with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun, and will also have a lower light transmission. Your home’s climate, orientation, and external shading will determine the optimal SHGC for a particular skylight or roof window.


Once you’ve chosen skylights that are energy efficient, it’s important to install them correctly to capitalize on their benefits. The best way to do this is to work with professional installers. Choosing the right installer will ensure they are air-tight, water-tight, and working seamlessly.

The way your product is installed will affect the energy efficiency of your home. Installing a skylight or roof window involves careful planning and sealing to create a moisture barrier to make the skylight as effective as possible. After locating the ideal location for your new skylight or roof window, the installer will create and frame the opening. If the ceiling is not sloped with the roof, they can install a light shaft that will pass through an attic space to the roof. Then, they will place an underlayment which goes beneath the shingles to make sure water moves away from the product properly.

Depending on the skylight type and brand, the installer will place about three phases of flashing, one around the bottom, step flashing around the sides, and solid flashing over the top, attached to the skylight to create a water-tight seal. Different types of skylights will have different mounts and are suitable for various types of roofs. Your skylight supplier, such as Glazing Vision, will be able to help determine which type is right for your home.

Flat skylights should be between 5% – 25% of the size of the floor area of the room they’re located in, depending on the number and size of windows. This way they will maximize light transmittance without creating an overwhelming glare.


Due to the location of skylights, such products can result in unwanted additional heat in summer and loss of heat from the inside of the home in the winter. To make skylights more energy efficient, manufacturers such as Glazing Vision use various glazing technologies including heat-absorbing tints, and insulated glazing such as low-e coatings or translucent insulation material between several glazing layers.

In warm climates, skylights should be placed on north-facing roof slopes, while in cold climates, south-facing slopes will capture the most possible sunlight. In areas that experience both warm and cold temperatures, consider locating skylights on east-facing slopes. Here, the morning sun will provide some heat and the skylight will be shaded from the most intense afternoon rays. Putting a skylight under the shade of deciduous trees will also help limit summer heat gain.

Your skylight should be tilted to the angle of your latitude plus ten degrees. This enables the skylight to capture the most sunlight and heat in the cooler months and deflect the high summer sun.

If you are considering a skylight and want it to be energy efficient, speak to one of our Technical Specification Managers at Glazing Vision Inc, we are happy to help!

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