Tips of the Trade

Tips of the Trade: Selecting Exterior Glass Doors

Glass entrance systems provide both a functional and aesthetic element for non-residential applications. These systems are required to provide durability, design integrity, thermal performance, security and safety. When specifying an exterior commercial glass entrance, several factors must be considered.

First, what are the functional and performance requirements of the application? Entrance door options will be largely dictated by accessibility (Americans with Disabilities Act), egress (accounting for volume and type of traffic), energy efficiency, and regional building code requirements.

Meanwhile, external and internal air forces created by wind, HVAC pressures, and seasonal change, which can cause the door to expand or contract, must also factor into the equation. Location-specific weather conditions, such as hurricane-prone coastal regions or severe winter climates, will require additional considerations in terms of weatherization, thermal performance and impact resistance.

Secondly, what is the architect’s design intent? Entrances play a large role in a building front’s overall aesthetic, thus it is important to select a door that complements the project’s design and aligns with the architect’s vision. Once form and function have been addressed, cost and lead time remain key influencers in product selection. Schedules and budgets have a tendency to trump aesthetics, thus door manufacturers are tasked with providing entrance solutions that eliminate the need to compromise design intent in the interest of budget or lead time.

This article looks at the range of glass door options on the market, with important details and specification considerations for each.

Frameless All-Glass Entrances

All-glass entrances are one of the most elegant of the main entry doors. Typically frameless with only top and bottom rails or patch fittings, these doors create a big statement. All-glass systems are also designed to provide clean, uninterrupted lines, and come in many configurations and finishes to complement virtually any surrounding surface.

It is important to note that all-glass doors have height, width, and weight limitations. Additionally, there are recommended minimum thicknesses of fully tempered glass that are determined by the door height. Depending on the door and opening size, the incorporation of a transom and/or stabilizer fins may be required.

In the interest of public safety, glaziers should always abide by the Glass Association of North America’s and the International Building Code’s recommendations and limits for heavy glass doors and entrances.

While all-glass doors are very effective in creating a beautiful, modern look, not to mention enhancing natural light, their application as exterior doors is somewhat limited, as they don’t seal well against water and air infiltration.

Aluminum Framed Storefront Doors

Aluminum framed storefront doors remain the most specified entrance in retail and commercial applications. They serve as a cost-effective entrance solution and are quite versatile. These doors are available in many styles and colors, thermally broken for improved thermal performance, and with many hardware and glazing options.

Aluminum framed systems address one of the biggest difficulties with glass—the weight. The reinforced metal corners can transfer the glass weight load to the hinge side of the door thus keeping the doors from sagging. In addition to accommodating added weight, full-framed doors are also better suited for the daily wear-and-tear of high traffic conditions as opposed to all-glass systems.

These performance features, coupled with the attractive price points and LEED-friendly qualities of recycled aluminum extrusions, make for an entrance that is both practical and economical.

Balanced Doors

Balanced doors are ideally suited for commercial projects with high traffic, or monumental entrances requiring oversized, heavy doors (up to 700 pounds). Not only do they require less operating space than conventionally hinged doors, they also qualify as a “barrier-free door,” meeting ADA requirements without power operators.

When balanced doors open, approximately two-thirds of the door swings outward while one-third swings inward, which helps avoid swinging over property lines and also allows wind or stack pressure to assist rather than hinder the operation of the door. Air pressure balances itself out around the rolling pivot, so less force is needed to operate the door.

This door design neutralizes two naturally occurring pressures— atmospheric (wind) and interior stack pressure—allowing effortless opening and positive closing.

Automatic Doors

An automatic entrance door eliminates the aggravation and struggle associated with opening a heavy, manual door, and demonstrates to those entering the establishment that the building owner cares about their convenience. Automatic doors allow businesses to welcome everyone entering, regardless of their physical capabilities (ADA compliance), with an accommodating, open door. Additionally, these doors have a controlled opening and closing, which is beneficial in applications with high wind or stack pressures.

There are three basic types of automatic doors: swinging, sliding and folding.

Automatic swinging doors have a variety of configurations, including a single door that swings in or out and is left-handed or right-handed, and a pair of doors that simultaneously swing in the same direction. The door operator can be concealed or surface-mounted. Swinging door options include: center pivoted, offset hung, balanced or hinged. Automatic swinging doors also feature sensors or control mats and safety signage.

Automatic sliding doors have flat panels that slide horizontally and linearly, with a variety of configurations. They share many of the same features and options as swinging automatic doors, including sensors or control mats and safety signage.

Automatic folding doors are comprised of two or more separate panels; one panel swings and the other panel slides in a guide. Automatic folding doors may include a single folding door that folds in or out and is left-handed or right-handed; or a pair of doors simultaneously folding in or out, either left-handed or right-handed.

Revolving Doors

A revolving door typically consists of three or four doors that hang on a central shaft and rotate around a vertical axis within a cylindrical enclosure. Revolving doors are energy efficient as they prevent drafts, via acting as an airlock and thus preventing increases in the heating or cooling required for the building.

At the same time, revolving doors allow large numbers of people to pass in and out. The wings of revolving doors usually incorporate glass to allow people to see and anticipate each other while passing through the door. Manual revolving doors rotate with push bars, causing all wings to rotate.

A speed control (governor) is implemented to prevent people from spinning the doors too fast. Similarly, automatic revolving doors have safety sensors built into their mechanisms to ensure people will not be run over by the wings.

This type of entrance can also be used as security measures to restrict entry to a single person at a time if the spacing between the doors is small enough and can also be designed for one-way traffic.

It should be noted that, per ICC, all revolving doors require a side-hinged swinging door in the same wall within 10 feet to comply with applicable egress codes and requirements.