Roof Windows / August 2, 2018 / Odo Vaillancour
A skylight is like a window which has been placed in your roof. It has a frame specially designed to withstand rain and prevent leakage from rain and snow. To maximize a skylights use of natural light to illuminate a room or its passive solar heating potential you will want to take into consideration how a skylight is positioned. Facing north your skylight will provide fairly constant illumination but will not provide a lot of heat. Facing east it will provide the maximum amount of light and solar heat gain in the morning. Facing west your skylight provides afternoon sunlight as well as heat gain. A skylight facing south provides the greatest potential for winter passive solar heat gain than any other location but will often allow unwanted heat gain in the summer.
The air near the ceiling is automatically cooled when fresh air flows in from outside. These roof skylights are so designed that they open and close a little to let in the fresh air. The glass tilts at about 45 degrees. There is a small handle to manually open the venting roof skylight. You crank the handle slightly to open or close or adjust the angle and position of the glass. The venting roof skylights are located in the ceiling of the house and are hard to reach so there is an extension to the handle. Otherwise every time you want to open or shut the venting roof skylight you will need a ladder or a high stool. Nowadays electronically operated venting skylights are also becoming very popular.
For example the optimum slope for a south-facing skylight in Columbus Ohio at 40º North latitude is 45º to 55º. Every skylight has a "shaft" which governs how much light is admitted into the room below. If all four sides are flared then the light is spread over a wide area. If your skylight has a shaft with perpendicular sides the light is focused straight below. If your skylights shaft is flared on only one or two sides then the light is sprayed in the flared direction. Ventilation If you wish you can have a skylight which also provides ventilation as well as light to your room. This allows you to release the hot air which collects at your ceiling.