The largest source of heat loss/gain from doors is not from conduction based on what the doors are made of, but from infiltration based on how well the door fits and how often the doors are open.
People door entrances should be equipped with a double ‘air lock’ entry. To be effective, the distance between the sets of doors must be far enough that both doors are not easily opened at the same time – except in times of high traffic.
Heating the space between the doors in an ‘air lock’ entry can add comfort, but doesn’t save energy.
Practices and Measures
- Maintain all door seals, including weatherstripping and boots
- If doors must remain open and it is not otherwise possible to restrict air infiltration, such as with the use of boots (photo above) then install air curtains or door heaters above the door. Air curtains may use heated air or simply blow a high pressure stream of existing room air across the door opening to reduce infiltration and exfiltration
- Replace doors that do not seal due to damage; it is difficult to repair doors that have been severely damaged
- Replace overhead doors that are open and closed often with high-speed doors
- Consider fabric high-speed doors that seal much better against air leaks
Roll-up doors typically offer a faster response time for open/close cycle and if high quality, may form a better seal.
The above overhead door has been replaced with a heavy vinyl roll-up door. It seals very tightly on all sides, has quick leases should it be run into, and operates much faster than a metal roll-up door. The existing metal door was moved to the outside for closing during security times or when the rapid open and closing door is not being used.
Inside shipping docks offer an alternative to outside docks. Trucks can be pulled inside and loaded/unloaded with the doors closed.
Door heaters/air curtains are installed directly above roll-up doors, and at an angle for Over Head doors.
(Illustration from Armstrong International Catalog)
The principal of air curtains is to create a barrier that other air does not easily cross.
(Illustration from PoweredAire)
There are many types of door heaters and air curtains that use all types of fuel, electricity or are unheated.
(Photo from PoweredAire)
Note: There are many manufacturers and web sites on these products; the web site below has been selected because it includes educational information about how the products work and are to be installed, and a wide variety of product for different applications.
935 Campus Drive
Mundelein, IL 60060
Web site www.dynacodoor.us
Powered Aire, Inc.
109 Mortensen Rd.
Greenville, PA 16125
Web site www.poweredaire.com
Source: Text Bob Fegan 1/2009; pictures Bob Fegan; other pictures and illustration source identified above; revised 3/2008;