In some homes, you'll encounter what appears to be a bright porthole in the ceiling. While it may look similar to a standard recessed light, it is actually capitalizing on sunlight to illuminate a room.

Solar tubes—also known as sun tunnels, tubular skylights, or sky tubes—use a simple design to bring light into the darker areas of a home. They provide a surprising amount of light, helping reduce your reliance on electric bulbs.

Though some designs have a few bends, the most efficient solar tubes lead straight down from the roof to a room. Dave Toht, writing for the National Association of Realtors' home improvement site HouseLogic, says the tube's interior is polished to reflect the light without diminishing its intensity.

On the roof, the tube is capped by an acrylic dome and flashing to prevent leaks. The California company Skylights of Los Angeles says the ceiling end of the tube includes a diffuser to help distribute the light throughout the room.

Some solar tube models offer a few extra features. Fans or vents may be incorporated if the installation is in a humid area where moisture is likely to build up on the interior of the tube. Jim Nash, writing for home improvement professional Bob Vila, says solar tubes may have dimmers to keep the light from getting too bright. It is also possible to incorporate an electric light into the tube for use at night.

Toht says a solar tube is sometimes preferable to a skylight because the cost is lower. The installation might also be simpler, and some homeowners can even do it on their own. However, Nash warns that anyone attempting to do so should be confident in their abilities. Solar tube installation involves cutting a hole in your roof, after all, and you'll also want to make sure it avoids hazards such as wiring and trusses.

Solar tubes are usually 10 to 14 inches in diameter. Skylights of Los Angeles says a 10-inch tube illuminates an area of about 160 to 180 square feet and is good for smaller areas such as hallways, closets, and bathrooms. A 14-inch tube provides approximately 260 to 280 square feet of light and is good for  larger rooms such as bedrooms and kitchens.

While solar tubes can be added to most rooms in a home, you'll want to keep them away from any television or computer screens. Toht says the light from the tube can produce an irritating glare, and you won't be able to get rid of it by simply hitting the light switch.

It is also difficult to install a solar tube in certain areas. Skylights of Los Angeles recommends that solar tubes work best when they extend no more than 20 feet from the roof. It is possible to run a tube through multiple levels of a home, but it will be more expensive and complicated. Toht says you should also try to keep the tube hidden in closets or other isolated areas if it is running through multiple levels.

Solar tubes can be installed in roofs with pitches of up to 60 degrees, but it may not be feasible to add them to steeper slopes. You'll have the longest period of interior light if you install the tube on the southwest corner of the roof.

You can consider having a solar tube installed as an individual project, or you can include it as part of a larger renovation. Mariana Pickering, writing for the home design site Houzz, says some roofers may offer to include a solar tube as part of their work.

Make sure the frame and glass in the solar tube offer good insulation and that there are no openings around the tube. Checking these qualities will ensure that you don't lose heat or cool air through the opening made to install the tube.