Windows and Doors in ICC 700-2008

Industry products can help builders and remodelers score points under newly-published National Green Building Standard
April 20, 2009
Resource | Codes & Standards

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The National Green Building Standard, a document developed by the International Code Council and the National Association of Home Builders, is said to be the first green building rating system to be approved by ANSI. Completed last year, it is now available for purchase through BuilderBooks.com.

The ICC 700-2008 document is designed to define green practices that can be incorporated into residential development and construction on a national scale and how home owners can operate and maintain their green homes. It follows up on NAHB's earlier National Green Building Guidelines, covered last year in Window & Door, and as highlighted below, contains very similar requirements and recommendations related to fenestration.

“The significance of this standard cannot be overstated,” says Eric Borsting, a California builder and chairman of the NAHB green building subcommittee. “This document–and the voluntary project certification program administered by the NAHB Research Center–will more readily enable green home building, remodeling and development all over the country.”

Practices outlined in the National Green Building Standard can be integrated into new single- and multi-family homes, home remodeling and additions, hotels and motels, and the site upon which the green homes are located. The green practices covered in the standard include lot design, preparation and development; resource, energy and water efficiency; indoor environmental quality; and operation, maintenance and building owner education.

The four threshold levels, Bronze, Silver, Gold, and Emerald, provide builders with a means to achieve basic, entry-level green building, or, on the other end of the spectrum, achieve the highest level of sustainable green building that incorporates energy savings of 60 percent or higher.

The new NAHB/ICC standard requires builders to include sustainable features in seven categories, including energy, water and resource efficiency, lot and site development, indoor environmental quality and homeowner education. Table 303 from the standard shows how the point system works in the existing guidelines, but a new higher emerald level will be added to the bronze, silver and gold certification levels when the new standard is issued.
Threshold Point Ratings for Green Buildings
 
Level of Certification
Category
Bronze
Silver
Gold
Emerald
Lot Design, Preparation & Development
39
66
93
119
Resource Efficiency
45
79
113
146
Energy Efficiency
30
60
100
120
Water Efficiency
14
36
41
60
Indoor Environmental Quality
36
65
100
140
Operation, Maintenance & Homeowner Education
8
10
11
12
Additonal Points From Any Section
50
100
100
100
Table 303 from National Green Building Standard.  In addition to the threshold points in each category, the standard includes numerous mandatory provisions that also must be met.  The standard also sets forth provisions requiring homes of more than 4,000 square feet to earn more points.
  
ENERGY PERFORMANCE REQUIREMENTS
The most specific requirements for window and door products appear in the section covering energy efficiency. The standard features two compliance paths to achieve its energy efficiency goals—one performance-based and one prescriptive. The same energy performance requirements for fenestration products are mandatory for both approaches, however. 
 
Section 701.4.4 says that windows, exterior doors, skylights, and tubular daylighting devices must have NFRC-certified U-factors and SHGCs in accordance with Energy Star or equivalent. There is an exception for decorative fenestration elements up to 15 square feet or 10 per of the total glazing area, whichever is less.

 

The prescriptive path outlined in the standard also includes two sets of “enhanced fenestration specifications” that can earn builders additional points. Tables 703.3.1(a) and (b) detail these options: 
 
Enhanced Fenestration Specifications
 
Windows & Exterior Doors
Skylights & TDDs
 
Climate Zones
U-factor
SHGC
U-factor
SHGC
 
1 and 2
0.45
0.3
0.55
0.35
 
3
0.35
0.3
0.55
0.4
 
4 to 8
0.3
Any
0.6
Any
 

Table 703.31(a).  8 points available in Zones 1-3, 5 points in Zones 4-5 and
6 points available in Zones 6-8.

Enhanced Fenestration Specifications
 
Windows & Exterior Doors
Skylights & TDDs
 
    Climate Zones
U-factor
SHGC
U-factor
SHGC
 
1 and 2
0.45
0.25
0.50
0.35
 
3
0.35
0.25
0.50
0.35
 
4 to 8
0.25
Any
0.50
Any
 
Table 703.31(b).  10 points available in Zones 1-3, 10 points in Zones 4-5 and
12 points available in Zones 6-8.

Under the performance-based approach, builders are also more likely to use higher performing windows and doors, as they can earn additional points by exceeding the requirements of the International Energy Conservation Code. 

SOLAR DESIGN
The Energy Efficiency section of the new standard lists several other additional practices which builders can use to score additional points, including the use of “sun-tempered design” is worth five points. Section 704.3.1.1 lays out a number of requirements covering building orientation, sizing of glazing, and design of overhangs. Examples of these provisions include "the long side (or one side if of equal length) of the building must face within 20º of true south" and "vertical glazing area is between 5 and 7 percent of gross conditioned floor area on the south face."
 
In addition to designing a home to benefit from solar heat, the standard awards points for “passive cooling design features (Section 704.3.1.3).  Up to four points can be earned by taking three or more  of six steps, including exterior shading on east and west windows through the use of moveable awnings or louvers, covered porches, vine-covered trellises or attached or detached structures, such as sheds or garages.  Other strategies include overhangs designed to provide shading on south-facing glazing and placement of windows and/or venting skylights to facilitate cross ventilation.
 
Other strategies to optimize a home’s use of the sun to reduce energy demand are rewarded as well.  Automated solar protection that provides shading for windows earns one point (704.3.1.2).  Two points are awarded for the use of tubular daylighting devices or low-E insulating glass skylights in rooms without windows (704.2.4).
 
RECYCLED/RENEWABLE CONTENT
Within the Resource Efficiency section of the new document (604.1), one point is awarded if two “minor components” feature 25 to 50 percent recycled content, two points for two minor components with 50 to 75 percent recycled content and three points when recycled content is greater than 75 percent in two minor components.  For “major components,” the potential points for recycled content double. The draft standard does not say whether windows or doors would be classified as major or minor components of a building, however.
 
The standard also awards builders points for the use of building materials “derived from renewable renewable resources.” Up to eight points can be earned for using “biobased” products, including certified solid wood, engineered wood, bamboo, straw, and other natural fibers.  The points awarded are determined by the percentage of the projected building material cost (606.1).
 
Using windows and/or doors made of certified wood or wood-based products can also help builders score points under ICC 700.  It awards three points for using a minimum of two certified wood or wood-based products in minor elements of a home, "such as trim, cabinetry or millwork."  NAHB recognizes a number of wood certification programs, including the Forest Stewardship Council, including the Sustainable Forestry Initiative, the American Tree Farm System and the Canadian Standards Association’s Sustainable Forest Management System Standards (606.2).
 
EXTRA CREDIT
Windows and doors can earn points in at least two other ways under the the NAHB/ICC standard.  Section 601.7 awards points for using building materials or assemblies that do not require site applied finishes.  In this section, it specifically cites “window, skylight, and door assemblies not requiring paint or stain on exterior and/or interior surfaces.”
 
Section 609.1 awards three points "per product/system comparison" for the selection of environmentally preferable products or assemblies based on a life cycle assessment assessment tool compliant with ISO 14044 or other recocognized standards.  Section 610.1 awards points for purchases from product manufacturer with operations and business practices that incorporate environmental management system concepts. The standard says the production facility should be ISO 14001 certified or equivalent and offers one point for every 1 percent of the estimated total materials cost coming from such production facilities, with a maximum of 10 points possible.
 
CONSTRUCTION PRACTICES
In its energy efficiency section, ICC 700 specifically requires that “caulking, gasketing, adhesive flashing tape, foam sealant, or weatherstripping is installed forming a complete air barrier” around windows and doors (Section 701.4.3.3).
.
The standard also awards practices that provide “enhanced durability and reduced maintenance.” In section 602.1, it awards three points for an exterior door assembly, including sidelites, that is covered and protected from the effects of precipitation and solar radiation. This can be done through the use of a porch roof or awning, extending the roof overhang or recessing the exterior door.  Additional covered door assemblies can earn an additional point.
 
The same durability section of the document (602.12) also awards six points when a builder shows flashing details in a home’s plans and flashing is installed around exterior fenestrations, skylights and doors and other applicable areas, such as roof valleys and various intersections.  To earn these points, a drip cap must also be provided above windows and doors that are not covered by a roof overhang or protected some other way.
  
More Information
NAHB offers more information on the standard and certification of green homes at a dedicated NAHB Green Web site.  It includes an online scoring tool for homes and a variety of information, as well as sections targeted at homeowners, verifiers, policy makers and others.