What is thermal bow?

Thermal Bow is a temporary condition which occurs in metal doors mainly due to the temperature differential from one side of the door to the other. This may occur in exterior doors when direct sun rays strike the door surface. When air conditioning creates a large temperature differential, the core may swell, causing the door to bow toward the sunlight. As a result, the lock can bind in the strike and fail to latch properly. Adjustments to the strike, latch or weatherstripping in the field are a temporary and inadequate solution. This condition, and the degree of bowing, depends on the door color, construction, length of exposure, temperature, etc. Thermal Bow can occur in reverse under extremely cold conditions.

Typical symptoms are:

• Door will bow towards the sun or exterior of the building
• Hardware latching and unlatching difficulties
• Door clearances may very tight at the top and bottom of the door

Ways to alleviate condition:

• Painting the surface of door a lighter color finish
• Select the door with a core construction of door which is less susceptible to thermal bow 
• Honeycomb and steel-stiffened doors are the least susceptible
• Install or use of an awning to block sunlight exposure on the door surface

If this is a chronic situation which occurs at all times of the day and night, it is most common cause is improper frame installation.