Optimizing Building Energy Performance
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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
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 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 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…).
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.
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
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
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.