Dear Jim: The sun bakes us through a large window. We also have a fireplace for heating in that room. Would installing a rolling shutter save energy and improve comfort? I am also concerned about security and storms. – Mike W.
Dear Mike: During summer, a south-facing window can let in up to 1,400 BTU per square foot of glass area per day. For a large window, this can make your air conditioner run much longer and use substantially more electricity. During winter, a significant amount of heat is lost outdoors through the large window, especially on cold nights.
Your house sounds similar to mine. About one year ago, I installed a rolling shutter outside an 11-foot-wide by 7-foot-high window. My family room has an efficient, heat-circulating wood-burning fireplace. It was noticeably warmer in my family room this winter because the rolling shutter reduced heat loss through the glass.
During winter, I keep the shutter closed because it more than doubles the insulation value of the double-pane, low-e window. During summer, I keep it either fully or partially closed depending upon how sunny it is. During spring and fall, I keep it fully open except when there is a severe storm forecast.
Rolling shutters operate similarly to an old roll-top desk with slats. A housing, which holds the slats when the shutter is open, is mounted above the window. The ends of the horizontal slats slide in a vertical track mounted on each side of the window opening. For my seven-foot-high window, the size of the housing box is only seven inches square so it fits under the soffit.
When ordering a rolling shutter, you must first select the type of slats. The three basic types are PVC, foam-filled aluminum and extruded aluminum.
For most residential shutters, lightweight PVC and foam-filled aluminum are adequate. They are strong enough to protect the window glass and provide good insulation, yet they are easy to open and close.
Most PVC and foam-filled slats have slots for light punched in the flanges between the slats. In the fully closed position, the slots are blocked.
As you start to open the shutter, the slats separate exposing the lighting slots, even though the shutter bottom edge is still down against the sill.
For a large window like mine, extruded aluminum slats are used to span the width. Since much of the energy savings is from blocking the sun (summer) and the dead air space insulation (winter), the heavier uninsulated extruded slats are only slightly less efficient than the others.
There are also several operator options for opening and closing the shutter. For large windows with heavier extruded slats, an electric motor drive is needed.