Let there be (natural) light! When designing or remodeling a home, even on a small scale, lighting is usually a strong consideration. The incorporation of natural light has become a focus for environmentally conscious and thrifty homeowners alike. Whether looking to reduce consumption of electricity, or just interested in incorporating more of the Sun’s wholesome goodness into a room, two options are most readily available: skylights and solar tubes.
Skylights, simply put, are windows located on the roof of a dwelling. Skylights have been around for far longer than solar tubes, providing the consumer with more available information. This information is both positive and negative. Common positives are the overall appearance and volume of light skylights provide. Negatives include high cost of installation and unwanted heat gain.
“Skylights bring in twice as much natural light as a traditional window of the same size,” writes Eric Corey Freed, LEED AP Architect and Principal of Organic ARCHITECT, in Green Building & Remodeling for Dummies. The location on the roof allows for more direct sunlight to pass through, illuminating the room below.
Skylights can be non-operational or operational depending on preference and climate, to capture passing breezes. Unfortunately, in addition to letting in light, skylights have been largely criticized for their solar heat gain. Solar radiation is able to pass readily through the skylight, strike an interior surface, and generate heat. The same process is at work in a car left out in the summer sun.
In addition, many construction details incorporating skylights are thermal bypasses that are under-insulated causing even more heat gain from the outdoors or attic.
Skylight locations can be a bit more restrictive as well — given roofing details and the cardinal direction of skylight location. For example, Freed recommends, “To reduce the heat gain from too much sun, install skylights on the north side of the roof“. Freed goes on to describe various glass types and window styles that can be used to further reduce the thermal gain from the sun’s rays, each adding substantial cost to an already expensive window.
Enter solar tubes. Sometimes referred to as a “sun pipe”, “sun tube”, or “sun tunnel”, a solar tube uses a small dome skylight on the roof and another on the ceiling of a room. Sun tunnels are typically low cost, and easy to install. They work by allowing sunlight to enter a domed fixture on the roof, and reflect through a mirrored tube into the room below. A low profile fixture, often called a “port hole” is installed in the room below. These two fixtures, the dome and “port hole” collect sunlight while helping to block out solar heat.
Another advantage of solar tubes is size. Solatube, a leading manufacturer of sun tubes in the United States, recommends a 10 inch diameter solar tube for rooms of approximately 100 to 200 square feet. Comparable skylights can be three to five times that size.
Ultimately, as in any construction decision, the choice is left to the owner. Skylights, while more expensive, are recognized by realtors as a feature that helps sell homes and adds value. Most homebuilders, as a result, have chosen to incorporate skylights into home designs as a means of using natural light and luring prospective buyers.
The trade off, of course, is properly locating and constructing skylights to minimize heat gain. Solar tubes, while relatively new, are able to provide large quantities of natural light while taking up less space and effectively eliminating solar heat gain issues. Costing slightly less, and eligible in most areas for tax credits or utility rebate, solar tubes win the money battle.
In either case, skylights and solar tubes are a great way to incorporate natural light and reduce the consumption of electricity.
Green Building & Remodeling for Dummies by Corey Freed.
Solatube daylighting systems.