Skylights: Should You Cut a Hole in Your Roof to Add One?

Skylights can do wonders for a room. With our typical Seattle gloom, the natural light they provide does more than brighten a room. It can brighten our moods. The right skylight can add height to a room. At the very least, make the room feel larger. From the outside, skylights can be a welcome architectural element adding to your homes curb appeal. 

If you are considering adding one, you need to consider the negatives as well.

Energy inefficiency 

Though skylights provide light and a bit of heat during the day, minimizing the need to use more electricity, the heat loose from them will far exceed any gains in the winter.

In warmer months, the sun beating down on them will add a considerable amount of heat. Without air conditioning, your home will be warmer. With it, the cost to cool it will increase. 

Any addition of a skylight means removing a section of insulation. We’re in Zone 4 for building insulation requirements, meaning an insulating R-value for ceilings should be between R38 and R60. The most efficient skylights come in at around an R-value of 9.8 (as of this publication). 

With the most efficient skylight, roof placement plays an important part of the efficiency equation.

The slope or tilt of the skylight affects solar heat gain. As a general rule of thumb to optimize solar heat gain in winter and minimize solar heat gain in the summer, you want to achieve a slope equal to your geographical latitude plus 5 to 15 degrees. – Energy.gov

We are at a latitude of 47 degrees. The roof slope where the skylight is to be installed should be between 52 and 62 degrees.

Water intrusion

There’s a hole in my roof! Regardless of the type of skylight being installed, there will be a hole cut in your roof. Unless done professionally (and sometimes even when done professionally), leaks are a persistent risk. The skylight itself could leak or the seal between it and the roof can fail. Regular inspections and maintenance are extremely important – more than usual – when skylights are installed. The best recommendation to limit the risk of leaks is a curbed skylight. 

Moisture concerns don’t end with leaks. Condensation is a serious potential problem. Condensation forms when warm air meets cool surfaces. The greater the surface area of the skylights in a roof, the increased potential for condensation. A secondary concern then becomes the increased heat loss through the skylights in winter. This can lead to ice dam formations. 

This needs to be addressed by re-evaluating your current levels of insulation and ventilation. As the skylights themselves are still going to be allowing heat to escape, it may be necessary to address how to insulate them in colder months. 

For all the aesthetic and psychological benefits from adding skylights, they do come with some real headaches. Without question, if you will be installing them, hire a professional. Skylights are not a smart DIY project.

But what if you already have them installed?

Maintenance is vital. They should be visually inspected each year, ideally twice, inside and out. Sometimes the first sign of a problem will show inside. In wooded areas, the high side of the skylight will collect leaf and tree litter. This can lead to water pooling and an area potentially attractive to small critters. We have seen cases where seeds have started to germinate in the debris packed against a skylight. A tree growing on your roof is not a good thing!

Repair – As soon as there is a sign they are leaking, repairs need to be made. If the first signs were inside, the leak has likely been a problem for some time. Waiting is not an option.

Roof replacement – If your roof will need to be replaced, depending on the type of skylight already installed, the recommendation is to replace the skylights. This especially true of deck mounted ones. While they can be reinstalled, they are more likely to leak as the removal process can bend the flanges and frames leaving them more prone to leaks later. 

Older skylights will generally be less energy efficient than new ones, making roof replacement the best time to upgrade.

In many cases, roofing companies will require they be replaced or ask for a signature waiving them of responsibility if they leak. 

Roof repairs – Any repairs done in the vicinity of a skylight need to be done with added care. Make sure you are using a reputable, professional company. Improper repairs, especially above the skylights (chimneys, vents, valleys) can lead to water collecting at the skylight. Sadly, we have seen workers sitting on skylight frames while on breaks and leaning on them.

In light of everything…..

Before getting skylights installed, consider the risks. Are the benefits worth it? Look at non traditional options like tube light, which will reduce some benefits and still add light while reducing the risks.

If you already have skylights installed, get with us to create a regular roof inspection and maintenance schedule.