Solar Gain & Skylights

Skylights are much more than design elements. They can provide natural light, and when strategically placed, these roof-top windows can help heat and cool a building using the principles of ventilation and solar gain. As a result, skylights can assist in reducing energy costs on both lighting and climate control.

There are some important considerations to be aware of if you intend to install skylights. Placement, quality of the windows, glazing, and other variables can help homeowners maximize energy savings.

Because of the potential for future issues, it is not a good idea to choose cheaply made windows or discounted installation. Luckily, because of their energy saving potential, skylights often qualify for property assessed clean energy financing (PACE financing). PACE programs help homeowners handle the upfront costs of installing energy efficiency features such as skylights. This means that you can schedule the upgrade and installation now, and then pay for the improvement over time as a line item on your property tax bill.

Why is Investing in Good Skylights Important?

Skylights can help lower heating costs during the wintertime because of something called solar gain – an occurrence that takes place when heat from the sunlight passes inside a home. Obviously, a skylight is one of the most effective means of giving the heat-providing rays a path to the interior of the building.

In the summer, however, this benefit could become a significant disadvantage. The solar gain will work against air conditioners, fans, or other cooling appliances. If the skylight does not include features which allow it to negate the summertime solar gain, then the air conditioner in an average home could spend as much as 240 kWh (kilowatt hours) more energy than if the skylight was not installed at all.

Another drawback to consider: the loss of heat through the skylight in colder months could be greater than the heat provided by solar gain. Anyone who remembers elementary school science class knows that “hot air rises.” Since the skylight is at (or at least near) the highest point in the house, it is an ideal target for hot air trying to escape.

These drawbacks are not necessarily deal-breakers. However, they highlight the need for high-quality skylights that can capture solar gain when it is needed, keep heat inside, and block out the sun when solar gain will hurt energy consumption.

Placement Matters

When it comes to solar gain, the location and slope of the skylight are significant. The first step is to make certain that there is nothing between the sun and the skylight. Trees, a chimney, an adjacent home, or other impediments may not fully block natural light, but they could still cast a shadow that will lower the effect of solar gain.

Also, in winter, the sun is lower in the sky than it is during the summer. Homeowners can take advantage of this natural phenomena by placing skylights on a south-facing section of the roof near an overhang. The skylight will allow the winter sun to enter and provide additional heat, but the overhang will block the direct sun in the summertime so that solar gain does not work against cooling appliances.