NFRC Certifies Heat Loss Ratings for Entry Doors
Entry doors will soon display the same certified energy ratings that have appeared on windows for the last couple of years. The National Fenestration Rating Council (NFRC) recently approved a rating procedure (NFRC 100 Section B) for determining the thermal performance of doors and sidelights. Morgan-Nicolai, Ceco, Stanley and Therma-Tru are some of the first manufacturers to participate.
A permanent label attached to the edge of the door slab lists the certified U-factor. A temporary label also appears in a more convenient place on the face of the door.
The certification procedure is the same for doors as for windows, although the standard sizes differ. Manufacturers may choose to test products either under the window or door procedures. NFRC allowed this flexibility for manufacturers whose product lines may cross over the definitions of windows and doors.
The energy rating is listed as a U-factor (the rate of heat loss and the inverse of R-value). Higher numbers mean more heat loss. The values presented include the door slab and frame.
Some door manufacturers sell only door slabs, while others sell only complete, prehung door systems. Some do a little of both.
A manufacturer who sells a particular door only as a prepackaged system may test and certify it as one unit. Doors sold as slabs that are prehung by another party are tested in one of two standardized frame systems. One is wood, the other is steel. The certified U-factor is listed for the appropriate frame type. If the manufacturer wants to list both, the value for the wood frame appears on the label, while the difference between the wood and steel frame values appears as an "add-on value" at the bottom of the label. The NFRC program includes labeling formats, quality control requirements and plant inspections for manufacturers. These aspects of the NFRC process are the same for windows and doors.
This article appeared in Energy Source Builder #37 February 1995