As we begin to blog on Thursdays as well, we continue our consumer guide to replacing windows and doors by covering some of the basic window and door terms that you should know about as you shop. Additionally, you can check out some of our other windows terminology here in case it does not get mentioned here.
Door and Window Types
Though doors clearly are functional and open, windows have the option of being operable or fixed, or a window that opens or doesn't open respectively (Fig. 4). Windows that are fixed are more energy efficiently simply by their characteristics of being airtight. Additionally they offer the most safety and security since they cannot be left unlocked or opened by any other means besides breaking, so if you have the choice, install or keep as many fixed windows as codes allow (floors with bedrooms need at least one operable window for emergencies).
Though fixed clearly only has one form, operable units have many: awning, casement, hopper, horizontal slider, vertical slider (single- or double-hung) and turn-and-tilt (Fig. 5). They may also go by other names, but each is clearly distinguishable by just looking.
Operable windows can be sealed (when closed, not to make them inoperable) in two ways: with a compression seal or a sliding seal. Compression seals generally make a window more airtight, so when possible choose that type of window (Fig. 6). Be sure to confirm that the gasket is a compression, neoprene rubber type.
Despite all doors being operable, they are actually less complicated than windows. Doors can be one of four things: solid, slid with an insulated core, solid with window(s), or solid with an insulated core and window(s). For patio doors, there is the normal slider, French doors, and the bi-folding types. Hinged French doors, with a solid center post to close again, and folding doors, with a compression-fit like an aircraft door, are more energy efficient (Fig. 7). More importantly is the material used. Solid wood, for example, is not as good as metal-clad, insulated core doors (depending on style and insulation material) (Fig. 8). Additionally, doors also have a frame, sill, optional glazing and rough frame opening in a wall as windows do (Fig. 9). Some doors can come factory installed in the frame and sill system like windows.
Glazing - Energy Efficiency
Glazing refers to the transparent (or translucent) material in a window or door. For windows, we often refer to them as single-, double- or triple-glazed. A window can be divided into multiple sashes which may move or can be fixed. A double-hung window, for example, usually has two movable sashes while a single-hung window may usually has only one (Fig. 10).Each sash may be divided into two or more lights (panes of glass) which are held in place by mullions and muntins (Fig. 10). The glazing types (single-, double- or triple-glazed) refers to that number of lights: single-glaze is one pane, double-glazed is two panes, and triple-glazed is three panes (Fig. 11).
Most windows in America are double-glazed for efficiency, but to determine how many glazings a window has, hold a light next to the light and count the reflections (Fig. 12). Double glaze windows, for example, will have two main reflections, indicating the number of glazings
Most window manufacturers offer many types of glazing which affect the insulations value and the likelihood of condensation. They also sometimes use transparent plastic films to increase energy efficiency, and can be referred to as glazings as well.
There are other ways to create energy efficient windows besides increasing from a double-glazed window to a triple-glazed; a variety of coatings on the surface, such as plastic films or inert gases between glazings, can increase the insulation value of a double-glazed window beyond a standard triple-glazed window. Such coatings are often used with gas fill (which we will discuss in more detail in a future blog). Most windows have incorporated sealed, insulated glazing (IG) units, meaning two or more glazing layers are sealed around the outside edge to prevent air or moisture from entering in, which helps eliminate dirt and condensation. If condensation is found between the glazing, its because moist air was leaked in through a faulty seal, and this can only be remedied by replacing the IG unit.
Spacers, Frames and Sashes
Conventional double-glazed windows have spacers, a strip of material found where glass meets frame, to maintain uniform separation between the panes of glass (Fig. 13). Traditionally made of hollow aluminum, spacers contain a drying agent or desiccant made to absorb initial moisture present at the time of manufacture in the space between the glazings. Metal spacers easily conduct energy and are significantly increase heat loss and poor window performance, therefore the best spacers are made from non-metallic materials. There are also hybrid spacers that are made with metal and non-metallic materials, and significantly do not conduct heat nearly as much.
The frame of a window holds the sash, and the glazed unit fits into the sash, thus creating a window. Considering the frame and sash may make up as much as one third of the total window area, both can be major sources of heat loss due to conduction through the material. Heat loss can also occur from air leakage due to increased expansion and contraction or warpage of a window's frame and sashes over time. Highly conductive materials used to create the frame and sash need thermal breaks incorporated in order to reduce heat loss. A large amount of heat loss via sash and frame usually results in condensation formation and frost on interior window surfaces.
Frames and sashes come in a variety of materials: aluminum, fiberglass (or fibreglass), vinyl, wood, and combinations of these materials (composite). Each has its benefits and drawbacks in terms of insulation value, strength, durability, cost, aesthetics, and maintenance requirements, but good quality windows can be made using any of these materials. The best way to consider energy performance is to use the Energy Rating (ER), which takes into account the thermal performance of the frame, sash, and glass. For more information, click here. We will also delve into this more in a later post (and we have plenty of other blog posts related to this topic).
There are many things that contribute a window's energy performance as well as many different types of windows and doors. For our next post, we will further discuss the different types of materials available as well as make a checklist of considerations you should have when purchasing replacement windows. Additionally, you can call one of our sales representatives at 888-367-0256 or click the button below to contact Brennan Windows by submitting a form. Stay tuned on Saturday for our next installment in this window and door consumer guide!