Windows, Glass, Doors and Hardware

Home | Fire Safety | Skyscrapers

Home Emergencies | Glossary


Windows are generally classified by their type of operation. There are fixed (do not open), double-hung (slide up and down), horizontal sliding (well named), casement (side hinged, like a door), and projecting (swing out or in, on horizontal pivots at top or bottom). See (ill. 39).

Windows are composed of the frame, which connects to the building wall, and the sash, which is the operable or movable portion.

The other major variables in the windows are the materials the frames and sash are made of, their sizes, and kind of glass they can hold.

Selection as to type of operation is mostly a matter of deciding how much of the window you wish to have open to outside ventilation, and how much ability you want to change the direction of the incoming air. For example, the double-hung and the horizontal sliding windows can open a maximum of 50% of the overall window size (usually somewhat less), but each affords no ability to control the direction of any incoming air. On the other hand, casement and projected windows can open almost 100% and do provide some amount of control on air movement patterns. This is because, like a damper or control vane, they angle the air in varying degrees, depending on the position of the sash.

Selection of the materials of which the frame and sash are made is dependant on several factors. Metal windows are normally made of steel, which must be protected from rust; or, of aluminum which is lightweight, however less rigid, but don't rust nor require painting to survive. Aluminum windows are available with various factory finishes and coatings which do enhance their appearance as well as eliminate grey oxidation, or discoloring, which eventually takes place with plain unprotected aluminum. The advantages of metal windows are the crisp, thin frame profiles which can be a design or visual asset, and their resistance to rot and decay compared to a window made of wood. They may also be slightly cheaper than wood windows, but this can vary with locale.

Wood windows, and windows of wood encased in a plastic jacket are available for residential construction. These have assets and liabilities which are directly contrary to those of metals; however, they are usually somewhat more costly and are always more bulky in lines and appearance. If of un-protected, or plastic-encased wood, they require more care and maintenance, such as painting.

(CAUTION) In very cold or very hot climates, metal windows have a very common defect, which is their ability to easily conduct heat. In those climates, the frame and sash parts transmit heat readily to either the outside or inside, thus contributing to the mechanical equipment load of the building. Also, depending on the level of humidity in the air on the warm side of the window, moisture condensation can easily occur with its annoying and damaging effects. Metal windows are made which have special split construction to break up the conduction path thru the metal and thus minimize these problems, but they are usually precluded from residential construction due to their higher cost.

Another cost factor, although admittedly not a major one, in the selection of windows can be whether or not special hardware is required to make the window function. For example, almost no special hardware is required for a horizontal sliding aluminum window, as opposed to special offset hinges, geared operator, and latch locks which are all necessary for casement type windows. In some respects, however, the old adage you get what you pay for applies.



Beyond the concerns for cost, type of operation, condensation / conduction effects of the frame and sash, and the appearance, the most important window decisions to be made are the quantity of glass to be installed, and its thermal, or insulating qualities. The insulation quality of clear sheet glass is directly affected by the number of parallel sheets, or panes, of glass that are used. Quite simply, the more sheets with thin air space separations between each, the better the insulation value. it's very difficult to envision a location or a situation wherein the installation of at least double-pane glass would not be beneficial, whether in the form of manufactured sealed insulating glass (Thermopane, Twindow, etc.,), or simply by the use of removable storm windows commonly found in the East and Mid-West. The reason for this recommendation is based on the fact that a single pane of glass in a vertical position has a heat transmission (U) value of 1.13, which is extremely high. Remember from the discussion on INSULATION, the lower the ‘U’ value, the better. Two parallel panes of glass reduce the ‘U’ value to approx. 0.55, while three parallel panes reduce it still further to approx. 0.36. (Remember, there must be a slight air space between each pane; the actual values of ‘U’ vary slightly dependent on the thickness of the air space between each pane). Now, compare these ‘U’ values to that of 0.08 for the solid sidewall construction having a Resistance ‘R’=12 required in the most liberal Zone of the country; and , you will readily conclude that no matter what is installed for window glass, it will result in much less insulating value than any other portions of the building.

Glasses other than clear are available which can limit the amount of heat passing thru due to direct solar exposure. These include reflective-coated and color-tinted, available in single sheet glass as well as sealed insulating glass. Although more expensive, these specialty glasses should be considered for large areas of direct solar-exposed glass in the warmer southern and southwestern locations where solar heat gain is a major factor in the cooling/air conditioning load of a building. The measure of effectiveness against the passage of heat thru special glasses is the shading coefficient. For example, the coefficient for clear untreated glass is approx. 0.95, whereas reflective coated glass can be as low as 0.23.

A supplemental benefit gained by installing multi-pane windows lies in the fact they normally will not form moisture condensation on inner or outer faces during extremes of temperature and humidity.

The discussion above on the relatively poor insulating quality of glass, underscores the need to be concerned with the quantity of glass to be installed. The greater the quantity of glass area compared to the remaining area of insulated solid wall, the poorer the overall heat loss/heat gain characteristics of the building. You must therefore, carefully balance and decide on the optimum amount and type of glass area which can be allowed and afforded, vs. the need to conserve energy, preserve interior comfort and achieve lower costs of heating and cooling.


The final point of concern regarding windows is the need for a good fit of the window parts, plus the need for weather-stripping. Other than heat loss or gain thru the glass areas of windows or doors—and even more significant than conduction of heat thru metal frames—is the resistance of the window to infiltration of air thru loose fitting parts. Substantial amounts of air can be lost or gained thru poorly fitted windows, a factor which is taken into account in the selection of heating and air conditioning equipment capacity. All windows which have moving sash should have at least single, and preferable double layers of weather-stripping. This is merely flexible gasket-type material which, like the rubber seal material around the door and windows of automobiles, maintains positive contact to moving parts and minimizes leaks of air and water. Ask your builder to show you the extent of these features on the windows being proposed in your building.

The major weakness points in today’s construction as far as heat loss or gain are concerned, are the windows and doors. This is directly attributable to the quantity of glass, the number of panes of glass, and the quality of fit of the moving parts.


Doors are classified by their suitability for exterior or interior use, by their details of construction, and by their method of operation, i.e., swing-hinged, sliding, pocket, etc.


Only certain doors are suitable for use in exterior walls of a building, where they will be exposed to the weather. Exterior doors must be assembled with water-resistant glue, or the door will gradually come apart as moisture penetrates and dissolves glue in the joints. Exterior doors can be used for interior Purposes, but not the other way around.

PANEL doors are those which have exposed solid side, top, bottom and intermediate rails (usually of wood), which are the main structural parts of the door. The spaces between the horizontal rails and vertical stiles may be plywood, solid wood, glass, plastic or grilles or louvers for ventilation purposes. Panel doors are generally more decorative in appearance because of the shapes and moulding effects used. Good quality Douglas Fir or other appearance grade wood is usually used in their construction, which allows for natural or stained finishing as well as paint finishes. See (ill. 40).

FLUSH doors have flat faces, usually both sides of the door, which may be plywood, hardboard, or metal. Flush doors are either solid core or hollow core. Solid core doors have an interior construction of solid wood pieces glued together, or the core may be of solid particle board or a fire-resistant mineral material. The top, bottom and edges are usually continuous pieces of solid wood. See (ill. 40). Flush exterior doors are usually solid core, as are other special purpose doors in commercial and institutional buildings, because of their increased durability and strength. Flush doors may have various hardwood veneer facings, suitable for natural or stained finishes, or be of less exotic, less costly materials more suitable for painting.

Hollow core doors differ from solid core in that the inner core of the door consists of an open grid or lattice work of crossed wood slats with considerable void spaces between them. These doors are much lighter in weight and are more generally made for interior use only. See (ill. 40).

BATTEN doors consist of solid wood boards fastened together side-by-side, with another layer of wood members, called ledgers, attached straight across or angled across the faces of the first board layer. See (ill. 40).



Doors are made in thickness of 1 1/8 inches, 1% inches, 1 3/8 inches and 1 3/4 inches (rare). Exterior doors should be not less than 1¾ inches thick, because of their larger overall sizes, and to accommodate the heavier-duty hardware required. 1 3/8 inch thick interior doors are common, and should be the minimum thickness for hinged doors up to 2ft-8inches wide; over 2ft.- 8 inches, doors should be 1¾ inches thick. 1 1/8 inch doors can be used for narrower doors and less critical applications such as bi fold closet doors. Stock door heights are 6ft-8inch, and 7ft-0 inch. 6ft-8 inch is suitable and most usually used for interior doors. Stock widths vary in 2 inch increments from about 1ft-6 inch up thru 3ft-0 inch. Door widths should vary depending on the location and purpose of the door. At least one 3ft-0 inch wide exterior door should be provided in every house to allow adequate in-and-out movement of furniture and equipment. Two such doors are better, at obvious major entry/exit locations (front and rear, front and side, etc.).

(CAUTION) Occasionally, interior doors are undersized in width, making it difficult to move furniture and belongings in and out of spaces. If there are doubts about the adequacy of a particular door size, increase to the next standard width, rather than accept the constraints of the smaller opening. The increment of cost is very minimal. Also, if there are handicapped or disabled persons in the household, certain minimum door openings will be required to accommodate their needs, such as 32 inches clear (minimum) for wheelchair access, etc. Any door less than 32 inches will present difficulties in furniture movement thru it.


HORIZONTAL SLIDING doors suspended by metal or nylon rollers from overhead metal tracks are often used for interior closets and storage spaces. By-passing sliders (ill. 41) can provide from 1/3 to 1/2 of the total opening as actual access opening; whereas, if all doors stack behind each other, 2/3 of the opening can be accessible.

POCKET doors are horizontal sliders which slide into a pocket created within the adjacent partition, and thereby are completely hidden and out of the way when open. See (ill. 42). A pocket door can be very useful in a location where closure of the door is only infrequently required; whereas, if hinged, the door when standing open would be an inconvenience or an obstruction. Pocket doors are not recommended for high-traffic locations where the door must be frequently opened and closed, because their operation is time consuming and clumsy.

SLIDING EXTERIOR doors (commonly called patio or Arcadia [which is actually a trade name] doors) are simply a form of by passing horizontal slider which are specially constructed and weatherstripped for exterior wall usage. Here again, quality of construction, good fit of parts, lots of weatherstripping, and use of multi-pane insulating glass are important. They are available in wood, steel, and aluminum.


ill. 42: POCKET DOOR

SWINGING HINGED doors are the most common operation found. These doors pivot on hinges mounted to the frame, close against stops along all sides of the frame, and are held closed by a latch or lock mechanism.

ROLL-UP doors consist of many small interlocking sections, usually steel or aluminum, which open by rising upward while coiling around a drum assembly at the head—or top—of the door opening. These are rarely used in residential construction.

SECTIONAL OVERHEAD doors are often used for large garage doors. They consist of horizontal sections full width of the opening but short in individual height, made of wood or metal, flush or paneled, connected together by hinges. The sections are guided by ball bearing rollers in side metal tracks and counterbalanced by various kinds of spring mechanisms, so that they rise up and lay overhead, above and out of the way of the door opening.

The DOOR FRAME is the surrounding unit to which the door is hung and against which it closes. The frame is a finished member which also serves to cap the rough wall opening. Frames are made of wood or metal. Wood interior frames are a minimum of 3/4 inches thick, if the stop or piece to which the door closes against is nailed onto the frame. Exterior wood frames should be thicker (a mm. before milling of 11/4 inches), with the strip being an integral and notched-out part of the frame rather than nailed on the surface, See (ill. 43). This is for reasons of security.


All hinged doors should have a minimum of three (3) butt hinges, in order to resist warpage, sag and poor fit. Butt means that the hinge is mortised, or housed, into the edge of the door, rather than fastened to its surface. Batten doors, however, usually require surfaced mounted hinges.

(CAUTION) If for some reason an exterior hinged door must swing out, with the hinges therefore exposed to the outside, the pin of the hinge which holds the two hinge parts together, and about which they pivot, should be a special self-locking pin so that the door can't be removed from its hinges when closed.

LATCH sets provide a knob or lever grip to operate the door, and a mechanism to hold doors in the closed position via a latch which engages the frame. A LOCK SET is similar to a latch set, but provides the ability to lock and unlock the door with a key. Locksets should have multi-tumbler cylinder keying, not be the old fashioned bit key, both for proper security and for compatibility with today’s technology. Latch and lock sets are either mortised—or housed into—the stile edge of a door, or are of the tubular bored-in type, which is mounted into a hole bored thru the faces of the door. The tubular type are much more common today and much less costly to install. See (ill. 44).

There are many other items of hardware which may be useful and proper depending on the location, need, etc. These include door closers, dead locks, dead bolts, kick plates, etc. They are considered beyond the scope and purpose of this book. Consult Your Builder or hardware Supplier.



There is a wide variety of finishes and designs available for hardware.

(CAUTION) More importantly, there is a wide range of quality in the mechanisms and make-up of hardware. Generally, it's good practice and value to spend a few extra dollars to buy better quality hardware, because its durability, improved security and trouble-free use will prove worthwhile in the long run.

Prev: Exterior Walls
Next: The Roof Structure

top of page    Home