We all need the natural light, the views and the ventilation that windows and skylights provide. Skylights can transform dark rooms into well-lit spaces... But that may come at a high price.
People often love skylights, but building energy experts detest them. And with a good reason: skylights can be a cause of huge problems.
A skylight is a weak link in the home's envelope, subject to extreme temperatures and pressures, something that should not be overlooked. Be aware to it if, you are planning to buy a skylight.
Modern skylights properly selected, installed and sized can prevent or minimize many of the problems that once plagued traditional skylights; but we should not overlook their potential for causing problems.
Skylights are not just a cause of water leakage problems.
They can also be responsible for...
1) excess daylight, glare and UV (ultra-violet radiation) damage;
2) energy loss;
4) roof ventilation problems;
5) ice dams.
Excess daylight, Glare and Furniture and floor Fading
Be especially careful with skylights in the sunny side of the house, or even in the East and West. A skylight can admit over three times as much light as a window of the same size.
Overheating and energy loss Problems
Water leaks, glare and UV damages are often seen as the main threats posed by skylights. But their thermal impact can be even more relevant. Overheating and heat loss can cost thousands of dollars over the years.
Even the best type of glazing, will not prevent significant heat loss and gains.
The problem is common to windows, but much more acute. Heat will escape out of the house, or enter into it at a faster rate.
To minimize this type of problems…
- choose a solar tube (tubular skylight), if you aren't interested in views and ventilation;
- consider a polycarbonate (plastic) aerogel insulated skylight;
- do not oversize your skylight;
- pay attention to the positioning of the skylight;
- choose a proper type of glazing, and consider skylight covers to reduce unwanted heat gain and loss.
Water leakage and condensation problems
Modern improvements in the skylight technology have eliminated some of the leakage problems once associated with skylights. But rainwater and snow runoff and extreme temperatures, year after year, can be a cause of damage.Poor quality skylights are highly prone to leakage and may need replacement after some few years.
The quality of the installation and the flashing of the skylight are critical to avoid water leakage problems and to ensure a longer lifespan.
Even the best skylight, improperly installed, will soon become prone to leakage or condensation problems.
Skylight leaks caused by Debris, Snow, Leaves, Damaged cladding and Flashing
Seemingly unimportant factors such as accumulation of debris, snow or leaves on top of the roofs can ultimately cause skylight leaks. They can block the normal draining of water and increase pressure around the skylight.
So, in existing skylights, make sure that the fasteners are secure and the flashing doesn't show signs of excessive wear, or that there isn't scratches on the cladding finish. Damaged cladding and flashing should be replaced to avoid further damages.
Skylights and Water condensation Problems
Many skylights have condensation channels, and small weep holes around the perimeter of their glass panes. The channels catch the condensation in the inside of the skylight, and the small weep holes in the perimeter allow the water to escape; but if this mechanism is defective or the weep holes clogged, water will overflow into the living area. Leaks on the lower end of the skylight can be due to this mechanism.
Obviously, skylights with low quality glass, or with a poor design, can also raise leakage problems; and that can only be solved by replacing them with energy-efficient units.
Condensation on the inside of the skylight panes or on the inside of its frames and sashes can be a natural phenomenon. It occurs on all cold surfaces.The ventilation of the room, or the use of exhausting systems, can solve some of these problems.
Be aware, anyway. Vapor condensation on the glazing surfaces surfaces of the skylight or around it, may go deeper. Many homes have excessive moisture, caused by baths, laundry, cooking and other internal sources of moist air, or by attic or basement leaks, bringing outside moist air into the house and ultimately to the skylight.
Skylight Wear problems
Many skylights use gaskets and deck seals, or adhesive underlayment and engineered flashing; others come with rubber gaskets, and vinyl flanges; and others rely mostly on mastic, cement or other sealants.
And some of these traditional sealants – namely mastic and similar sealants - may fail with time, causing water leaks.
Re-flashing or re-sealing can solve some water leak problems.
Poor Installation and condensation problems
Modern skylights from top manufacturers rarely fail in their first years of operation. But a poor installation can precipitate the problem.
Be special cautious with the skylight flashing and the water-sealing system, but pay also attention to low levels of insulation and sealing on the underside of the skylight.
The installer should use enough roofing felt and insulation in the area between the frame of the skylight and the rough opening. Otherwise, moist air will escape from the room and enter into contact with the underside of the flashing or cladding, causing water condensation that will will drip back into the living space below.
Problems with Skylights installed in bathrooms
How to get natural light into our bathrooms? A common solution is to install a skylight in the bathroom, but it can be a huge mistake.
Do not forget that bathrooms are a high-humidity room, and lots of condensation plus cracks are responsible for huge moisture problems.
Skylights can interfere with roof ventilation and contribute to ice dams
Skylights can also cause problems on the roof ventilation systems, particularly when they disrupt the air flowing from the soffit to the roof peak…
In the winter, in cold and snowy areas, skylights can also be a cause of ice dams: heat loss through the skylight to the roofing, and the consequent roof warming and snow melting, can ultimately be a cause of ice dams. Many of the worst ice dams are associated to skylights.