Draft Proposal CB-5 

This concept has been developed by the DOE Building Energy Codes Program (BECP) as a possible code

change proposal to the Commercial provisions of the 2012 International Energy Conservation Code

(IECC).   Interested parties are asked to submit any and all comments on DOE's initial concepts and draft

code change proposals. For instructions on submitting comments, visit:

www.energycodes.gov/development/commercial/codes/iecc/concepts/

Fenestration Product Rating (CB-5) 

Objective:  Remove default values for fenestration thermal properties (U‐value, SHGC, and VT) resulting

in a requirement that all fenestration have those properties determined by an accredited independent

laboratory and labeled and certified by the manufacturer.

Suggested Code Change Proposal

Revise Section C303.1.3 as follows and delete Tables C303.1.3(1), C303.1.3(2), and C303.1.3(3):

C303.1.3 Fenestration Product Rating. U-factors of fenestration products (windows, doors and 

skylights) shall be determined in accordance with NFRC 100 by an accredited, independent laboratory, 

and labeled and certified by the manufacturer. Products lacking such a labeled U-factor shall be assigned 

a default U-factor from Table C303.1.3(1) or C303.1.3(2). The solar heat gain coefficient (SHGC) and 

visible transmittance (VT) of glazed fenestration products (windows, glazed doors and skylights) shall be 

determined in accordance with NFRC 200 by an accredited, independent laboratory, and labeled and 

certified by the manufacturer. Products lacking such a labeled SHGC or VT shall be assigned a default 

SHGC or VT from Table C303.1.3(3). 

Reason:  The lack of labels and other marks to verify the thermal properties of installed fenestration in

the field is causing considerable confusion and adversely impacting the confidence level and cost

associated with compliance verification (enforcement).  The code now requires a determination of

thermal properties in accordance with specific National Fenestration Rating Council (NFRC) standards

and the labeling and certification of fenestration product properties to those standards as with a

number of other products, components, and equipment covered by the ICC codes.  Allowing default

values for unlabeled fenestration products means some products not so tested can be evaluated at plan

review using default values, but those products and likely others will be found in the field as unlabeled.  

Is an unlabeled product encountered in the field really unlabeled or was the label simply torn off?  This

is causing confusion in the field, not only from building to building but within specific buildings where

some fenestration was intended to be assessed using the default values and other fenestration the

NFRC determined values.  Beyond this problem of “unlabeled and labeled but missing labels” is

verification of the correct default based products in the field.  How does one readily determine if a metal

door is insulated or not?  How can you easily determine by sight the existence of a thermal break on

windows?   
The NFRC standards have been in existence for some time, a majority of products have their thermal

properties determined in accordance with those standards, and it seems reasonable to expect all

fenestration products to be labeled with their actual thermal properties to facilitate verification of code

compliance in the field.  If a fenestration product is not labeled in the field, then it is clear the label is

missing and values can be determined from the manufacturers listing as opposed to raising the question

if the fenestration is “unlabeled or labeled but missing labels.”  Default values served a purpose at one

time but they are no longer needed and, as noted, are creating challenges for compliance verification in

the field.

Cost Impact:   There is a modest cost impact associated with this proposed change.