ebuild Guide to Patio Door Specifications

Patio doors provide convenient access with significant advantages over standard entry doors: patio doors are fully glazed to expand the view while flooding interior spaces with natural light. While old-style patio doors were notorious for heat loss, leakage, and poor security, modern doors offer significant improvements. Frames and glazing are more energy-efficient, many products incorporate multi-point locking mechanisms for better security, and sophisticated flashing packages prevent leakage. The two basic types of patio doors, sliding and hinged, offer distinct feature sets.

Sliding patiodoors (sometimes called gliding doors or bypass doors) are best for maximizing views and admitting daylight. They consist of two or more individual panels, at least one of which is able to slide back and forth on hidden rollers. Sliding panels can be combined with fixed panels to create dramatically broad expanses of glazing. Panels slide parallel to the wall so they don't interfere with furniture placement or walking areas outdoors or indoors, a particular advantage if they lead to a small patio or deck.

Hinged patio doors operate in much the same fashion as standard entry doors, but they are fully glazed and often hang in pairs. In one configuration, the doors are center hung (hinged on either side of a central mullion) and open much as butterfly wings. French doors on the other hand are hinged at the side jambs so that the door panels meet when closed. The latching mechanism is contained in an astragal mounted to one of the doors. When French doors open, the entire area between the hinges is clear.

Choosing a patio door often comes down to a matter of aesthetics versus energy-efficiency. A swinging door can be weather-stripped more effectively than a sliding door, but individual panels are narrower and more visually obstructive. A sliding door is more space efficient and lends itself to larger openings, but the large expanse of glass is problematic in regard to heat loss and solar heat gain.

Key Specifications

Dimensions--Manufacturers use various conventions to identify the size of patio doors. In some cases, nominal dimensions (or call-out dimensions) correspond to the overall dimensions of the rough opening that the door fits into, rounded to the nearest whole inch. However, one manufacturer uses the term callout to refer to internal reference numbers that don't correspond to an actual dimension. So in general, it's safer to consider nominal and callout dimensions more as product identifiers than as actual dimensions.

Color/Finish--In the case of clad doors, this attribute applies to the exterior surfaces of the door and its frame. In the case of aluminum, vinyl and fiberglass doors, it applies to exterior as well as interior surfaces. In the case of unclad wood doors it relates to whether the door is unfinished, primed, or pre-finished.

Unit Format (Sliding doors)--Sliding doors can include various combinations of sliding and fixed panels but essentially there are two types of sliding patio doors: bi-parting and bypass doors. Bypass door represent the majority of sliding patio doors where one panel is operable and the adjacent panel is fixed. Bi-parting doors consist of two operable panels that slide open in opposite directions to create one vast opening.

Unit Format (Swing doors)--This refers to how the door is hinged, whether it is hung separately or combined with another door, and whether it is a fixed or operable door.

Number of Door Panels--This refers to the number of fixed and moveable panels, whether hinged or sliding. Fixed door panels should not be confused with sidelites which are smaller in width than the actual door panels.

Door Swing--Hinged doors can be mounted to swing into the house or to the outside; the choice involves various tradeoffs. Outswinging doors don't interfere with furniture placement in a room but they might prove awkward or even unsafe if they swing onto a small deck. Outswinging doors are more prone to deterioration caused by weather exposure, but tend to be more energy-efficient than in-swinging doors because wind pushes them against the weatherstripping rather than away from it.

Top profile--Most doors have a square-off top. Arched-top or radius doors offer a dramatic appearance but are more expensive. Also, doors with a non-square top may be more costly to install because of special requirements for wall framing, jambs, and interior trim.

Additional Considerations

Patio doors configurations can feature various combinations of fixed, hinged, and sliding panels. Consequently, builders have to be very careful when ordering these products. One method of describing the combinations of sliding panels is to describe door operation with X and O designations, with X representing the operable panel and O signifying the fixed panel. For example, a door operation described as OXO would feature two fixed panels flanking a sliding panel; OXXO would feature two sliding panels and two fixed panels (sometimes called a bi-parting door). Some manufacturers refer to the fixed portion of a sliding door as a sidelight or an inactive panel, while the sliding portion is sometimes called a vent panel or active panel.

Nominal or callout dimensions, as noted above, offer a way to identify products but don't always provide the actual door dimensions a builder or designer typically needs for installation, particularly when it comes to remodeling projects. Always look for rough opening dimensions to determine the actual size of the opening a framed door will fit into. Another important number is the unit dimension (sometimes called frame dimension or outside frame-to-frame dimension). This typically refers to the actual size of the framed door, measured to the outermost surfaces of the jamb, excluding applied trim or casing. If a patio door includes a transom, the unit height of the door is measured to the top of the transom frame. In some cases, manufacturers will also provide a panel dimension for a patio door, which typically refers to the actual size of an individual door or door panel. When making detailed solar gain and heat loss calculations, however, you may find it more helpful to use an unobstructed glass dimension, which refers to the amount of glass that's actually visible in a panel. Unfortunately, you won't find all of these dimensions on a typical product sizing sheet.

Materials:

The two main elements of a patio door are the frame and the glazing, and depending on where in the country the door will be used, either one of these may be the deciding factor. Metal-frame doors are typically less expensive and less energy-efficient than fiberglass or wood doors, but they offer the advantage of a less obtrusive frame. The chief disadvantage to a wood frame is the amount of maintenance it requires. Clad products attempt to offer the best of both worlds, and have the energy-efficiency of a wood frame with the low-maintenance of vinyl or aluminum cladding. In the case of clad wood patio doors, manufacturers offer a choice of wood for the interior surfaces of the frame, typically a veneer. Choose wood such as pine if the interior surface will be painted. Other woods, such as Mahogany, alder, Douglas fir, and maple are more appropriate for stained or clear finishes.

The glazing of a patio door has a considerable impact on its energy efficiency as well as its cost. Patio doors, particularly sliding models, offer broad expanses of glazing to capture views and admit daylight, but that same expanse is a prime source of heat gain in the summer and heat loss in the winter. Manufacturers offer a number of glazing options to reduce heat loss and heat gain, but it's important to balance the cost of upgraded glazing against the expected energy savings. This often depends on the location and exposure of the patio door.

Glazing options include:

• Double- and triple-glazing, air fill.
• Double-and triple-glazing, gas-filled. Argon and krypton are colorless, non-toxic gasses that provide better insulation than air.
• Tinted glass. Tinting reduces sun glare.
• Low-e glass. An invisible coating on the inner surface of glass that improves the thermal performance by reducing solar heat gain and thermal heat loss. Three variations are available:
• High solar gain: best for areas with cool summers and very cold winters.
• Moderate solar gain: best for areas with moderately hot summers and cold winters.
• Low solar gain: best for areas with very hot summers and either cold or mild winters. This type of low-e coating does the most to reduce sun fading of indoor surfaces.
• Impact-resistant glass. Increases safety and security.

The energy performance of glazing in a patio door can be described in several ways. Manufacturers provide either the glazing U-Factor (preferable) or its R-value. The U-Factor is a measure of non-solar heat flow through glazing; the lower the number, the more energy-efficient the glazing. On the other hand, R-Value describes a material's ability to block heat flow; the higher the number, the better an insulator it is. The Solar Heat Gain Coefficient (SHGC) is a figure that describes how effectively the glazing blocks heat-gain caused by sunlight. The smaller the number, the more effective a material is.

* Figures are based on a range of products available in 2006

Additional Information

American Architectural Manufacturers Association www.aamanet.org

American Institute of Architects (AIA)
www.aia.org

American National Standards Institute (ANSI)
www.ansi.org

American Society of Civil Engineers (ASCE)
www.asce.org

Associated Builders & Contractors (ABC)
www.abc.org

Associated General Contractors of America
www.agc.org

Association of Window & Door Installers (AWDI)
www.awdi.com

ASTM International
www.astm.org

Blue Book of Building & Construction
www.thebluebook.com

Builders Hardware Manufacturers Association
www.buildershardware.com

Building Codes Assistance Project (BCAP)
www.bcap-energy.org

Building Officials and Code Administrators (BOCA)
www.bocai.org

Building Trades Directory
www.buildingtradesdir.com

Construction Specifications Institute (CSI)
www.csinet.org

Door and Access Systems Manufacturers Association
www.dasma.com

Door and Hardware Institute
www.dhi.org

Efficient Windows Collaborative
www.efficientwindows.com

ENERGY STAR
www.energystar.gov

Glass Association of North America
www.glasswebsite.com

Glazing Industry Code Committee
www.glazingcodes.org

Insulating Glass Certification Council (IGCC)
www.igcc.org

Insulating Glass Manufacturer's Association
www.igma.com

International Conference of Building Officials (ICBO)
www.icbo.org

International Window Film Association
www.iwfa.com

National Association of the Remodeling Industry
www.remodeltoday.com

National Fenestration Rating Council
www.nfrc.org

National Fire Protection Association (NFPA)
www.nfpa.org

National Glass Association
www.glass.org

National Institute of Building Sciences
www.nibs.org

Northeast Window & Door Association
www.nwda.net

Occupational Safety and Health Administration (OSHA)
www.osha.gov

Protective Glazing Council
www.protectiveglazing.org

Safety Glazing Certification Council (SGCC)
www.igcc.org

Screen Manufacturers Association
www.smacentral.org

Steel Door Institute
www.steeldoor.org

Steel Window Institute
www.steelwindows.com

U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy
www.eere.energy.gov

Window & Door Magazine
www.windowanddoor.net

Window & Door Manufacturers Association
www.wdma.com