With the recent “Heat Dome” weather behind us, let’s take a look at an abnormal occurrence that can happen to doors when there is an extreme difference in temperature on either side of the door.
Thermal bow is a short-lived phenomenon that sometimes occurs on exterior doors. Any type of insulated door that is exposed to direct rays of the sun can experience this effect, which is characterized by a swelling of the door core that causes the door to bow toward the sun. This occurs when the inside-outside temperature is very different. The door usually goes back to normal after the sun sets for the day.
Symptoms of thermal bow include difficulties in latching or unlatching hardware, and issues with a very tight door clearance at the top or bottom of the door. Some doors are more likely than others to experience this effect, since it depends on the door color, door construction, length of sun exposure, and extremity of the temperature differences. Both steel and FRP (Fiberglass Reinforced Plastic) doors are susceptible.
To minimize the annoying effects of thermal bow, paint exterior doors a light color, or arrange for shade (such as a tree or an awning) to protect the door from direct sunlight. Another option (for some climates) is to choose door cores that are honeycomb or steel-stiffened, in lieu of insulated cores, since these tend to be less vulnerable to thermal bow.
Finally, while thermal bow is typically seen when the outside temperatures are very hot, it can also happen under extremely cold conditions, too.
Confused over any of this door-related terminology? Make sure you bookmark or download our handy Door, Frame, and Hardware Glossary. LaForce customers also receive great service and technical advice from our knowledgeable installation team, so make sure you utilize this resource!