6 great tips for specifying and installing windows and doors
When it comes to controlling moisture and increasing energy efficiency in buildings, windows and doors are among the most vital components in commercial and institutional construction. Improper or insufficient design details and shoddy installation practices can lead to air infiltration, moisture intrusion, and poor overall system performance.
To promote consistent, high-quality installations of windows and doors, the American Architectural Manufacturers Association (AAMA) has issued a 317-page installation manual geared toward the commercial building market. The publication, AAMA Standard Practice for the Installation of Windows and Doors in Commercial Buildings, addresses the installation of window systems and exterior glass doors—including hinged and sliding-glass doors—for both new construction and replacement projects.
The manual offers hundreds upon hundreds of how-to tips, lessons learned, and advice on designing, specifying, and installing window and door systems. We've highlighted six of the best tips below; see the box for more boo-boo's to avoid.
1. Install only those products designed to meet the performance levels expected on the job.Comparing the water performance capabilities of the products intended for the job with the project specifications can greatly reduce the potential for water damage due to improper product selection. Use products only on projects that have performance requirements less than, or at most equal to, the rated performance of the product.
“Where products are subjected to increased risks of wind-driven rain events, they will typically be expected to have achieved a higher design pressure (DP) rating and water penetration resistance test,” says Ken Brenden, AAMA's technical standards manager. “All products have limitations when it comes to their performance ratings. Placing a product with a relatively low DP and water resistance rating in a structure located in an extreme weather environment will certainly lead to problems.”
2. Make sure to rebalance HVAC systems when installing energy-efficient windows and doors in existing buildings. When new energy-efficient windows and doors are installed in existing buildings, the HVAC system should be rebalanced to accommodate the reduced levels of air infiltration through the windows and doors.
If you don't rebalance, negative pressures can be created within the building because the HVAC unit is still trying to draw make-up air from the existing spaces, yet there is less volume allowed from around the windows and doors. When the allowable air infiltration is reduced in volume, a higher pressure (negative) is created within the structure. That make-up air must come from someplace else, typically from other small holes or cracks in the building envelope. This can lead to whistling and howling noises and water infiltration in places that had never occurred in the building before, says Brenden.
3. When installing exterior glass doors in multifamily dwelling units, consider these building code pointers and cautions:
Doors must have a minimum clearance width of 32 inches (measured from the face of the door to the stop of the door while open 90 degrees) for wheelchair access.
Exterior door thresholds and sliding door tracks typically should not exceed ½ to ¾ inch in height. Thresholds and changes in level at these locations are to be beveled with a slope no greater than 1:2.
Minimum clearance width for an accessible route inside the unit is 36 inches.
If a balcony or patio has doorways leading into two or more separate rooms, all doors must be wheelchair accessible.
Note: Always consult with the local building code official to determine the applicable code requirements.
4. Keep windows flush with the face in surface barrier applications. In surface-barrier wall systems that don't include a water-resistive barrier behind the exterior skin, such as poured concrete walls or CMU without wall cavities, do not allow the windows to extend beyond the exterior face of the building or beyond the exterior water barrier.
“It's imperative that sealant continuity be achieved between the drainage plane of the window/door and the adjacent construction,” says Brenden. “This crucial area forms the primary defense against air and moisture intrusion.”
5. Never take action inconsistent with the manufacturer's installation instructions without consulting all appropriate parties. The manufacturer is most familiar with how the product should be installed to function properly and meet the terms of the warranty.
“Installation is not a one-size-fits-all solution,” says Brenden. Each product has unique design characteristics, including method of fabrication and assembly, hardware, sash operation, and recommended maintenance. These factors often dictate how the manufacturer requires its product to be installed to meet its performance requirements.
6. Know when safety glazing is required. According to IBC 2003, safety glass is required in any operable window or fixed panel adjacent to a door where:
The nearest exposed edge of the glazing is within a 24-inch arc of either vertical edge of the door in a closed position; and
The bottom of the exposed edge of the glazing is less then 60 inches above the walking surface.
Exception: Safety glass is not required when there is an intervening wall or other permanent barrier between the door and the glazing. In addition, it's not required for glazing in walls that are perpendicular to the plan of the wall the door is in.
When designing rooms that include operable windows or individual fixed panels not adjacent to doors, safety glass is required where:
The exposed area of an individual pane is greater than nine sf;
The exposed bottom edge if the glazing is less than 18 inches above the floor;
The exposed top edge of the glazing is greater than 36 inches above the floor; and
One or more walking surface(s) is within 36 inches horizontally of the plane of glass.
Exception: Safety glass is not required when a protective bar 1½ inches or more in height and capable of withstanding a horizontal load of 50 lb. per linear foot without contacting the glass is installed on the accessible sides of the glazing 34-38 inches above the floor. In addition, it's not required in the outboard lite in an insulating glass unit or multiple glazing where the bottom exposed edge of the glass is 25 inches or more above any grade, roof, walking surface, or other horizontal or sloped surface adjacent to the glass door.
AAMA Standard Practice for the Installation of Windows and Doors in Commercial Buildings (317 pages) is available to members for $50; $100 for non-members. Order at: www.aamanet.org.