High R Value Exterior Doors
Some of the features that help therma tru doors earn their energy star qualified ratings include.
High r value exterior doors. Rails and stiles these are the horizontal and vertical parts that brace a wood door. This is a huge difference and essentially comes down to astm c518 being a theoretical maximum based on a steady state thermal test of only a portion of the door panel. When determining how much insulation you need don t guesstimate calculate. A 2 1 4 inch solid core wooden door for example has an r value of 3 70.
R values climb as thickness of the material increases. The r values of most steel and fiberglass clad entry doors range from r 5 to r 6 excluding a window. In new homes especially in cold climates in very energy efficient buildings look for the best performance doors possible. Rustica s french style sliding barn doors entry doors and rustica s replacement windows have the most efficient r value on the market listed at 3 94 for interior doors and replacement windows and 5 31 for a 2 1 4 exterior door.
R value measures how well certain building insulation materials can resist heat. An insulated steel or fiberglass will have an r value that is twice as good generally r 5 to r 6 but in some cases as high as r 7. Therma tru fiberglass doors have a solid polyurethane foam core which is among the most energy efficient door materials available today. Based on astm c518 calculation method the door has an r value of up to 11 but using astm c1363 tested operable the same door only have an r value of up to 3 5.
The r value of a 1 3 4 inch wood door is 3 03. Glass inserts also cut the door s insulating value though double or triple panel glass reduces that effect. A polyurethane foam core. Look for a door with a good insulation value say a u value of at least 0 2 that is r 5 metric.
European manufacturers of passivhaus certified doors advertise r values as high as r 11. Know exactly how much you need with our project calculators. Most therma tru decorative as well as privacy and textured glass is triple pane for reduced heat flow.