No house is completely airtight and even those which appear to be tight and wellbuilt may contain innumerable openings too small for water but ample for the passage of air.
To make a house as heatproof as possible, it is necessary to stop up as many openings as you can, and to make all exposed surfaces of the house poor conductors of heat.
Storm windows help prevent heat loss in two ways. First, they seal the window, making it more nearly airtight, and secondly, the air between the regular window and the storm window will act as insulation and prevent loss of heat through conduction. How well a storm window performs this function will depend upon how tightly it fits.
If the window does not fit tightly, air will find an easy exit around it, and the air between the storm and regular window will absorb heat instead of acting as insulation.
For best results, storm windows should be hung on as many windows as possible and should be fitted with weather stripping, particularly if they are not tight. If you cannot afford to equip all the windows in the house with storm sashes, put them on the most exposed side of the house.
There are storm windows to fit nearly every kind of window, from double-hung to steel casement.
A great deal of heat will be lost through the numerous openings in the house. Windows, especially, provide openings because no window can be made tight enough to prevent all air leakage. But a great deal of this heat loss can be stopped by weather stripping, and it should be installed on every window, including those equipped with storm sashes.
Without doubt the most effective weather stripping is metal, installed in grooves cut into the window sashes and frames. The stripping is usually put on by a professional, as special tools are required to cut the grooves, and unless the job is done precisely, the weather stripping will do no good and more openings may be exposed.
There are many good brands of weather stripping that can be nailed directly to the sash or frame. Some of these are flexible, while others are in rigid strips.
One of the cheapest kinds of stripping is felt, available in a roll. Attached to the sash and frame by means of tacks or small brads, it will give fairly satisfactory service for a season or so. In time, it will shrink and have to be replaced.
A somewhat more effective stripping is made of metal, with a felt interior that protrudes far enough to form a tight seal between the sash and frame. A small cardboard gauge is sometimes provided to make the proper location for the stripping along the frame and sash before nailing it. This will insure tight stripping without causing the sash to bind and damage the stripping when the window is opened or closed.
For double-hung windows, nail the weather stripping for the upper, or outside sash to the outside of the frame. For the inside sash, nail the stripping on the inside of the stop beads. The window should be closed when the weather stripping is attached. For the upper sash, use one long, flexible piece of stripping for both sides and top.
On the lower sash, affix a piece of stripping to each side and a piece to the bottom of the sash, so that it fits snugly against the sill. Nail the last piece of stripping to the top of the lower sash to cover the crack between the upper and lower sash. Its exact location on the sash will depend on the space between the lower and upper sash when the window is closed.
When using rigid weather stripping, make sure that your measurements are correct before you cut off a piece to nail. The corners should be mitered to make a tight joint.
On steel casement windows, attach the weather stripping by means of a special clamp or with a prepared adhesive. If the adhesive is used, clean the metal, if you intend to have a strong joint, with petrol. Be sure the metal is dry.
Put weather stripping around doors as well. If the distance between the bottom of the door and the floor is too great to be covered effectively with weather stripping, fasten a strip of wood to the base of the door with wood screws. This will reduce the size of the gap so that it can be sealed with weather stripping.
There are numerous small openings around window frames and at other points on outer walls which should be filled. Use caulking compound for this work.