If you are on the fence about adding skylights to your home this post will help!
There are some major disadvantages to skylights especially here in Arizona where cooling bills can rival your mortgage. These disadvantages will stem from having more light enter your home; which raises the temperature of your home, and makes it more expensive to cool your home.
Disadvantages of Skylights
According to Energy Vanguard U-Factor, Solar Heat Gain Coefficient (SHGC) and R-values should be used to calculate energy efficiency. In short, this would mean that since a skylight would be less insulated than a typical roof or wall plus the added sunlight exposure makes the room much hotter. A U-factor is a calculation to determine how much heat loss occurs meaning a window with a lower U-Factor translates to a better-insulated window. R- Values would be used to calculate insulation for other areas of your home or office, so a higher R-Value would mean a great amount of insulation.
For a more up to date information International Energy Conservation Code (IECC) click here.
Since your glass skylight does not conduct in the same way as a wall or ceiling made from wood or concrete during the winter months cold temperatures will seep in easier. Dwell recommends using a skylight that has insulation as well as being “thermally broken” meaning all hardware inside the skylight is not connected to hardware touching the outside of the skylight. Another option to reduce heat loss would be to apply a film to the skylight to reduce solar radiation. Solar tubes on the other hand do not contribute to heat loss.
Heating cost or cooling cost increase
SFGate appropriately called skylights “year-round energy losers”, because a well-insulated skylight will lose more heat during cold months like December. While in warm months like June, a room with a skylight will have a higher temperature because of the increase in sunlight and SHCG. Solar Heat-Gain Coefficient or SHGC is a measure of how much direct sunlight translated into solar heat is gained and trapped by a window frame or the window itself; which raises the temperature.
Since skylights can be large in size than a window the can let in more sunlight from outside causing fading to materials like wood or fabric. Another factor to consider is that an improperly installed skylight could leak causing water damage to the items inside your home as well as possible mold and water stains. When an accident like this does occur it is best to speak with your insurance agent to make sure that your policy will cover damages from improperly installed skylights.
Limits on usable space
When skylights are installed on residential or commercial buildings they limit the amount of roof that can be used for equipment like air conditioners, or back up generators. For a residential building, this may not be as big of the issue since the equipment could be installed on the ground level, or on a section of roof that does not have a skylight. The situation for a commercial roof, in a densely populated area, is not the same since there are often multiple tenants working out of one building, making rooftop real estate even more of a factor, and could lead to an increase in accidents by roof crews working on or near skylights.