A -- You are absolutely correct about the enhancing effect of adding a skylight to an otherwise ordinary room. I installed a large super-efficient one in my own family room. It brightened up the room so much that, for several weeks, I inadvertently walked over and tried to switch off the lights when I left the room.
Although skylights are certainly easier to install in a room with a sloped cathedral or vaulted ceiling, they are most often installed in rooms with flat ceilings with an attic above. All you have to do is build an insulated tapered lightwell between the roof and the ceiling.
From an energy-efficiency standpoint, adding a high-quality efficient skylight is almost a wash during the winter. To reduce heat losses, I mounted a magnetic clear plastic storm window under my skylight to form a dead air space, and it is barely noticeable. Installing a skylight reduces the need for electric lights and, with the proper orientation, it provides some passive solar heat gain from the sun. A true solar south (slightly different from magnetic compass south) is best. A southwestern orientation is next best. In all but the hottest climates, avoid a northern exposure. Installing a venting skylight, as you mentioned, can be a real energy saver in the summer. Since the hottest air in a room stagnates up at the ceiling, the skylight will exhaust it. This creates a natural airflow, drawing fresh cooler outdoor air in your windows.
With the new controls available, skylights are convenient to open and close. A hand-held remote control or wall-mounted control is good for skylights in a lightwell, but you will have to run electric wiring to the skylight. If you have only a standard hand-crank rod, you probably won't open it as often as you should, thereby cutting down on maximum energy savings in the summer.
If you have been to a local home center store to look for skylights, you have probably seen, at most, only 5% of the styles and designs available. There is a huge array of shapes, frame designs, flat and domed glass and plastic glazing, etc., and each type has its advantages. Many of the smaller commercial models also work well for residential use. Two major design features to consider are the frame and the glazing materials. The strongest skylights have solid frames made of wood with durable aluminum cladding on the exterior. These are also attractive with the natural wood exposed indoors.
Another strong design fuses a fiberglass frame to the clear or tinted glazing for a leak-proof unit. The glazing options are similar to new efficient window glass. Double-pane glass, with a low-emissivity coating and argon gas in the gap between the panes, is a good choice for most homes and climates. Super-efficient Heat Mirror glass is available for cold climates.
For a steeply pitched roof, as is often found in a remodeled attic, a floor-to-ceiling balcony-style skylight is ideal. It is made of two large sections. When it is opened, the lower half, which is hinged at the bottom, forms a balcony with a handrail. The upper half becomes a glass cover over your head.
Proper sizing of a skylight is also important. If the skylight is too small, it will not provide adequate natural light or ventilation. If it is too big, there will be excessive heat loss in the winter and it will look out of proportion for the room. A good rule of thumb is that the skylight area should be about 5% of the room floor area.