The building enclosure is an assembly of materials and layers that acts as an environmental separator between the indoor and outdoor. It controls heat flow, airflow, water vapor flow, rain penetration, groundwater ingress, the transfer of light and solar radiation, noise and vibrations, contaminants, environmental hazards, odors, critters, and fire. A successfully designed and constructed building enclosure provides strength and rigidity, and must be durable. After energy conservation, long-term in-service performance of a Building Enclosure is arguably the next most important determinant of a building’s sustainability. Although energy conservation is adequately addressed within green building rating systems, attention to the Building Enclosure has been lacking.
LEED AND THE BUILDING ENCLOSURE
It seems obvious, then that the building enclosure should be prominently featured in green building rating systems. Inexplicably, this is not the case with the LEED rating system. In an earlier Straight Green article “Green Building Rating Systems and Building Durability” I wrote about the flawed approach currently employed in LEED to address building durability. The LEED “durability” credits (available only in LEED Canada and LEED for Homes rating systems) are written in a way that every building can get the available points by simply stating that the building’s systems were evaluated, and a glut of forms filled out with completely inconsequential information. As flawed as they are, they are the only credits within LEED that address the importance of the Building Enclosure.
GREEN GLOBES AND THE BUILDING ENCLOSURE
The current draft version of Green Globes Proposed American National Standard 01-2008P also addresses building durability by making five points available to teams that attempt to describe measures employed to describe and predict the building’s service life. In crafting this to be a “building service life” issue rather than a “building durability” credit, the rating system hopes to avoid the legal issues surrounding certification of a building’s durability.
Dig a little deeper into the current draft of Green Globes and you will find much more about the Building Enclosure, starting with a unique, forward-thinking feature called “Project Management for Green Design and Delivery Coordination.” This is the first of seven “areas of assessment” within the rating system that requires teams to establish the environmental goals of a building before design activities are begun. Points under this assessment area are given for establishing green performance goals for several building elements, including the Building Envelope. Another point is available for ensuring that, “The building envelope was weather-tight and permitted to dry before installation of interior walls, wood floors or ceilings or HVAC systems.”
The GDDC area of assessment also includes available points for developing a Whole Building Commissioning strategy with specific emphasis on the Building Envelope. It is this portion of Green Globes that introduces Guideline 0-2005, The Commissioning Process, from the American Society of Heating, Refrigerating and Air-Conditioning Engineers. This document describes how to verify that a facility and its systems meet the owner’s project requirements. It is the foundation for a series of National Institute for Building Sciences commissioning guidelines that deal with specific disciplines, including the building enclosure. Five points are awarded if “The Building envelope (roofing assemblies, waterproofing assemblies, fenestrations and doors and cladding/skin) was commissioned in the pre-design, design and construction phase in accordance with ASHRAE/NIBS Guideline 0-05: Article 5, 6 and 7.”
Establishing performance goals and commissioning requirements in the pre-design phase is perhaps the best insurance that a building will be designed with the highest possible degree of sustainability. I have worked on many projects in which sustainability was considered late in the design process, often as an afterthought, with less-than-optimal results. It’s nice to finally have a rating system that provides incentive and rewards teams for early consideration, planning, and adoption of green building strategies.
In the Green Globes Resources and Materials assessment area, 42 points are available under Section 10.7 Building Envelope. This part of Resources and Materials addresses the following components of the building enclosure:
• Roofing Membrane Assemblies and Systems
• Roof and Wall Openings
• Foundation Systems
• Below Grade Walls
• Slabs and Above Grade Horizontal Assemblies
• Exterior Wall Cladding Systems
• Rainscreen Wall Cladding
• Continuous Air Barriers
• Vapor Retarders
CONSTRUCTION AND INDUSTRY CHECKLISTS
Green Globe rating system requirements for building enclosure components include verification that they were designed and installed in accordance with manufacturer’s instructions, field inspection during installation, and field testing. The rating system relies on construction checklists found in NIBS document Guideline 3-06 Exterior Enclosure Technical Requirements for the Commissioning Process for several building enclosure assemblies.
An example of the type of items contained the checklists is provided below, for waterproofing assemblies, from Annex M.1 Construction & Industry Checklist M.1-1 for Waterproofing:
Verify subcontractor is authorized by manufacturer to apply product.
Verify that acceptable weather conditions are present for application (above 40 deg F, not damp or foggy, depending on material used).
Verify surfaces are primed, if required.
Verify that subcontractor has properly disposed of excess materials in compliance with EPA and OSHA requirements.
Ensure pipes, ducts, conduits, and other items penetrating membrane are watertight.
Verify proper coverage and quantities of materials such as mil thickness.
THE BUILDING ENCLOSURE AND TESTING REQUIREMENTS
Points are available in Green Globes for some building enclosure assemblies that have been field and/or laboratory tested for minimum performance levels. Rainscreen Wall Cladding assemblies can earn a project two points if tested in accordance with AAMA 508-07 for both pressure-equalized and non-pressure equalized systems (at the time of this writing, AAMA is currently in the process of developing a companion standard to AAMA 508 establishing minimum performance criteria for non-pressure equalized “open joint” cladding systems).
Roof and wall openings (skylights and windows) can earn up to five points if “selected and configured to meet performance requirements of established Design Pressure, in accordance with AAMA/WDMA/CSA 101/I.S.2/A440-05.” In addition to being laboratory tested, these assemblies are also required to be field tested in accordance with ASTM E1105 - Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls.
AIR BARRIER ASSEMBLIES AND VAPOR RETARDERS
In addition to addressing bulk water intrusion issues, Green Globes has points available for meeting minimum performance requirements for air barriers and vapor retarders.
Six points are available for design and construction of a building employing a continuous air barrier assembly. Teams are required to demonstrate that materials and assemblies were designed and installed in accordance with ASTM E2178 - Test Method for Air Permeance of Building Materials and ASTM E2357 - Test Method for Determining Air Leakage of Air Barrier Assemblies, respectively.
Another six points are available if teams can demonstrate that the building:
Was designed and constructed with a Class I or II vapor retarder on the interior side of framed walls in Climate Zones 5, 6, 7, 8 and Marine 4 in accordance with the International Energy Conservation Code 2007 Supplement, and that:
Crawl spaces are adequately insulated and equipped with a continuous vapor retarder.
Green Globes is extremely comprehensive. There is little that the rating system does not address. Of the 1,000 total available points, more than 50 are assigned specifically to the Building Enclosure. Unlike LEED, Green Globes does not penalize buildings for points that are not applicable. For example, points available for existing building under LEED remain in the denominator under LEED, but are removed from the calculation in Green Globes if the project is for new construction. Under LEED, the number of available points in the denominator never changes, and points that cannot contribute toward achievement of a rating count against the building. In Green Globes, all points that do not apply are removed from the denominator. The final level of certification is based only on the points applicable to the project. A building using the Green Globes system may end up with only 700 points in the denominator, which makes the 50 points available for the Building Enclosure worth that much more, as a percentage of the total.
It is encouraging that the building enclosure is being comprehensively addressed in a green building rating system. The prominence of specific inclusion of building enclosure elements in Green Globes underlines the importance of the building enclosure in determining a building’s overall measure of sustainability. Compliance with the building enclosure requirements in the newest proposed version of Green Globes will certainly result in buildings that are more energy efficient, and more durable than those that do not. According to the Green Building Initiative’s Web site, the Green Globes technical committee will complete a final round of changes to be reviewed again by the public in the spring. The committee expects to finish their work on this version of the standard in mid-2009. Go to www.thegbi.org for more information on Green Globes and how you can contribute to its improvement by providing comments. W&C