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Optimizing Building Energy Performance
How Doorways Contribute to Increased Energy Efficiency

While the negative environmental implications of gas guzzling cars are well known, inefficient buildings are also a sustainability drag: studies show buildings consume roughly 40% of global energy use. As a critical component of any building’s envelope, doors and hardware can improve overall facility energy efficiency by reducing thermal and air leakage as well as reducing the impact of electronic access control (EAC) systems.

The building energy use statistic noted above comes from a report—Energy Efficiency in Buildings – A Global Economic Perspective—by the World Business Council for Sustainable Development which also finds that heating and cooling needs account for more than one-third of building energy use. This one area of energy consumption can be lowered by equipping buildings with frames, doors, hardware and specialized doorways that form an effective thermal barrier.

Thermal Break Frames
The most basic measure for improving energy efficiency entails the use of thermal break door frames. These specially designed frames are built to thwart metal’s natural heat transfer capabilities. Thermal break frames feature strategically placed barriers that prevent heat/cold transfer. A thermal break in the frame, filled with closed-cell polyethylene foam lowers its overall U-factor (or U-value).

U-factor is the measure of heat transmission from one side of an opening to the other. The lower the U-factor, the more effective the material is at preventing heat transmission.

Metal door frames with a thermal break made of insulated material help prevent heat transmission. In cold weather, thermal break frames reduce heat loss and prevent condensation or frost from forming on the frame’s interior portion. The barrier provides a positive thermal break within the frame profile, delivering maximum protection against cold penetration.

Insulated Doors
Insulated doors can also be used to improve building envelope thermal performance. Used on exterior openings in conjunction with thermal break frames and high-quality weatherstripping, these doors help minimize energy loss. The insulating properties of a door are usually expressed as the R-factor.

R-factor is the measure of a material’s ability to resist heat flow. The greater the resistance—or R-factor—the more effective are a material’s insulating properties. Simply stated, the R-factor is the inverse of U-factor. The following equation can be used to convert R-value to U-value: U = 1/(R1 + R2 + R3…).

A door with a high R-factor improves thermal performance making it ideal for use in the building envelope. The doors are constructed from sheet steel in 20- (standard duty), 18-, 16-, and 14-guage (extra heavy duty) thicknesses. The doors can also be reinforced with steel stiffeners for added strength. The core or interior space of the door can be filled with a variety of material including paper honeycomb, polystyrene or polyurethane. The thermal properties of a honeycomb core are poor and should not be seriously considered for envelope use. Cores made from polyurethane or polystyrene perform the best in thermal resistance testing as it creates a solid barrier within the door.

Insulated doors can also be used on interior opening applications that require a temperature controlled room, such as a computer server room.

KERF Frames
Application of weatherstripping can be simplified with Kerf frames. These specially designed frames feature a grove that is constructed along the section of the frame that comes in contact with the edge of the door. The grove serves as a convenient channel to install weatherstripping without the use of additional fasteners.

Sustainable Access Control
Careful selection of access control hardware can reduce power consumption and infrastructure needs. One of the greatest efficiencies can be found with the use of IP-based access control solutions, which reuse existing WiFi or Power over Ethernet (PoE) equipment. This reduces or eliminates the need for security infrastructure, lessening both power requirements and materials used.

Integrated PoE locks combine all access control functionality (credential reader, controller, lock) into the hardware and use existing network cabling for both power and data. The most efficient PoE devices feature the lowest power consumption with a maximum of 7 watts per lock — 50% less than typical PoE installations.

WiFi access control solutions leverage current 802.11b/g WiFi infrastructure, and offer the same reduction of components as PoE, and optimize power consumption for long battery life.

Yet another great option for energy savings is exit devices with electric latch retraction (ELR). Driven by motor instead of solenoid, electricity savings per activation can easily exceed 50% over other methods of electric latch retraction.

The Big Picture
Reducing building energy consumption is an enormous challenge that will require closer attention to details. Although they are relatively small in the scope of an entire structure, doors, frames and hardware do play a role in improving building energy efficiency. Each opening component must be carefully chosen to ensure maximum energy savings are being achieved.

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