ON OCT. 1, CALIFORNIA'S
Title 24, Part 6 of the 2005 Building Energy Efficiency Standard for Residential and Nonresidential Building, will become effective. The code will influence the way buildings are designed and constructed throughout the state. The new legislation is designed to serve four primary functions:
1. To respond to California's energy crisis, reduce energy bills, increase energy delivery system reliability and contribute to an improved economic condition for the state
2. To respond to the AB 970 (Statutes of 2000) urgency legislation to adopt and implement updated and cost-effective building energy-efficiency standards
3. To respond to the SB 5X (Statutes of 2001) urgency legislation to adopt energy-efficiency building standards for outdoor lighting
4. To emphasize energy-efficiency measures that save energy at peak periods and seasons, improve the quality of installation of energy efficiency measures, incorporate recent publicly funded building-science research and collaborate with California utilities to incorporate results of appropriate market incentives programs for specific technologies
The energy code is estimated to be about 20 percent more stringent than ASHRAE 1999/2001. But the California Energy Commission believes the directives are essential to achieve state-mandated goals. These goals include decreasing energy consumption, lessening peak loads, reducing global warming, moderating the heat-island effect and cutting down on fossil-fuel usage.
Although Title 24 only applies to those in California, it exemplifies the importance of staying abreast of energy-code changes in the states in which your firm works. It is important to know what the energy code requires and if the state energy commission is making modifications to it. If modifications are imminent, find out how you can get involved in the process. California is a good case history. Your state may be planning energy-code changes, as well.
THE GREEN BUILDING MOVEMENT
Since the construction of the Crystal Palace in London in 1851, designers have looked for ways to moderate temperatures within buildings. The Crystal Palace symbolized the latest technological achievements of its time. The building was designed in 10 days, could house 13,000 exhibits and hosted 6.2 million people. The designers used innovative passive systems to moderate the building temperature. The glass roof was equipped with water-cooled, retractable roof awnings. The building included operable roof and wall louvers and ventilators. An underground cooling chamber moved cool air into the building. Passive systems such as these were the only options until the 20th century, when heating and cooling systems were invented and refined. These systems provided the ability to heat and cool high-rise buildings, which led to the massive building structures we take for granted today.
"In the 1970s, we witnessed the creation of the first Earth Day, the 1972 oil embargo and the establishment of the Department of Energy," states Charles Praeger, the Metal Building Manufacturers Association (MBMA's) assistant general manager. "Since then, have been solid efforts underway to increase the efficiency with which buildings and their sites use energy, water and materials. This requires reducing building impacts on human health and the environment through better siting, design, construction, operation, maintenance and material removal. In essence, it addresses the complete building life cycle."
These objectives have caused many states, such as California, to embrace green-building concepts and sustainable design practices and work toward more-efficient energy standards. Energy-efficient metal building systems can help states achieve their energy goals.
A vast majority of metal building roofs, for low-slope, nonresidential construction, have utilized through-fastener roof systems with a bare Galvalume-coated steel surface. Under the new code, it will be more difficult to use these systems on conditioned buildings.
KNOW THE ENERGY CODE
One of most important components in designing an energy-efficient structure is the building envelope, which consists primarily of walls, roofing and windows/skylights. "The envelope significantly impacts total heating and cooling loads," Praeger says. "Investment in cool roofs, insulation or energy-efficient windows can result in smaller HVAC systems and reduced lighting requirements, which can offset the cost of a more energy-efficient envelope."
The new California Energy Code requires that the building must meet an energy budget established for it based on the 16 California Climate Zones and using approved software programs for nonresidential buildings. The code applies to all new buildings, as well as reroofs and building additions, except for institutional buildings, such as hospitals and jails. The code is all inclusive.
There are three methods to comply with the code. These methods are common to energy codes and standards and accommodate as many building alternatives as possible.
The Prescriptive Method also is referred to as the Envelope Component Approach. It offers the easiest way to comply but is relatively inflexible and includes specified requirements based on climate zones. The Prescriptive Method categorically states what envelope components must be used on a building to comply. This includes roofing, walls, floors, windows, skylights, etc., for low-slope, conditioned spaces. It represents the straightforward "no-trade-off" requirements that form the baseline for the other methods for code compliance. It encompasses new buildings and additions and reroofing projects.
An essential new requirement under the Prescriptive Method is that all conditioned buildings must have a cool roof. Roof insulation criterion also is specified by the code when employing the Prescriptive Method. The maximum U-value for roof systems in Climate Zones 1 through 5 and 10 through 16 is 0.051, using a standing-seam metal roof with thermal blocks and double-layer insulation. A U-value of 0.076 is required for Climate Zones 6 through 9, which include the southern coastal region.
Envelope Trade-Off Method-143(b)
The Envelope Trade-Off Method offers greater flexibility. With this approach, the thermal performance of one envelope component can fail to meet prescriptive requirements, as long as other components perform better than required. For example, if a roof system does not meet the prescriptive cool-roof requirements, overall compliance may be achieved by using more insulation in the walls and/or roof, installing more energy-efficient windows, or adding window shades or overhangs. When employing this method, the proof of compliance is more involved, requiring clear documentation of overall heat loss and gain.
Although Title 24 only applies to those in California, it exemplifies the importance of staying abreast of energy-code changes in the states in which your firm works.
"A vast majority of metal building roofs, for low-slope, nonresidential construction, have utilized through-fastener roof systems with a bare Galvalume-coated steel surface," Praeger notes. "Under the new code, it will be more difficult to use these systems on conditioned buildings."
To ensure compliance, it is essential to perform a trade-off analysis. (MBMA developed an Overall Envelope Approach spreadsheet to do this. Visit www.mbma.com for more information.)
Whole Building Methodology-141
The Energy Cost Budget, or Whole Building Methodology, is the most rational yet the most complex alternative. In addition to allowing envelope trade-offs, it permits design substitutions if they can be proven to reduce annual energy consumption. These design trade-offs involve the building envelope, HVAC systems, flooring, lighting, and water and heating systems.
Because many metal building systems contractors provide complete design-build construction services for single-source building projects, the Whole Building Methodology may represent the best option. "However, because of the complexity of developing the analysis for this methodology, it is wise to bring an energy consultant onto the design team," Praeger adds. The California Association of Building Energy Consultants is a good resource and provides certification programs for energy consultants, as well as educational programs.
COOL ROOF MANDATES
The Title 24 legislation requires cool roofs for all low-slope buildings that are conditioned spaces. Unconditioned spaces are defined as requiring less than 5 btu/hr/sf cooling and less than 10 btu/hr/sf heating.
The Prescriptive Method requires a cool roof with a total solar reflectance of 0.70 or greater and an emittance of 0.75. However, other cool roofs with lower reflectance and emittance and non-cool roofs, such as bare Galvalume, can be credited through the Envelope Trade-Off Method or Whole Building performance method.
For any cool roof, the material must be rated and labeled per Section 10-113 of the code. The code specifies the requirements of the rating program and identifies the Cool Roof Rating Council (CRRC, www.coolroofs.org) as the sole supervisory entity for providing the rating system.
CRRC mandates deal with reflectivity, emissivity, slope specifications, and initial and aged performance. The industry's paint and coating suppliers are working through the Cool metal Roofing Coalition with CRRC to get families of colors approved rather than individual colors. Paint manufacturers will become "Licensed Other Manufacturers." Metal building manufacturers also are working with CRRC to become "Licensed Sellers" so the roofing products used on buildings are rated and labeled.
THE DAYLIGHT FACTOR
Skylighting for the 2005 Building Energy Efficiency Standard has two primary requirements. Consideration must be given to the minimum daylighting provisions and also to their impact on a building's energy consumption.
When designing for skylights, an analysis should be performed to determine how skylights would affect conditioned and unconditioned spaces. Other considerations are building size and height, ceiling height, roof slope, lighting power density and visible light transmittance (tint). Exemptions to the code exist for buildings in Climate Zones 1 and 16 and facilities with specialized uses, such as refrigerated buildings, theaters and museums.
The Building Estimating Daylighting Guide, developed by MBMA, enables users to explore options for skylighting and light-transmitting roof panels that meet the daylighting provisions of the code. The guide helps construction or specifying professionals to develop an estimate of the square footage of skylighting or light transmitting roof panels required to meet the daylighting provisions in the 2005 Building Energy Efficiency Standard. This number then can be inputted into the Title 24 Envelope Approach spreadsheet to perform the energy analysis on the building envelope.
METAL AND COMPETING ROOF SYSTEMS
Understanding the Title 24 energy code means learning how metal roofing compares to other roofing products, such as thermoset membranes, modified-bitumen membranes, tile and shingle roofs, and spray-on coatings. Cool metal roofing is highly reflective and durable, as well as available with high emissivity. It is recycled and recyclable, has a low life-cycle cost and is aesthetically pleasing. Reflective pigments also reflect more infrared light, which allows design teams to use darker colors.
Research conducted by Oak Ridge National Laboratory, Oak Ridge, Tenn., under the auspices of the Cool Metal Roofing Coalition, showed that "prepainted metal roofing retained 95 percent of its initial solar reflectance over a three-year period." The fence-post exposure studies showed that polyvinylidene fluoride (PVDF) base paint metals maintain their resistance to soiling for at least 30 years.
"The new California mandates are complex yet can be managed through knowledge and a willingness to adapt to change," Praeger says. "Complexities can be best understood by studying the code and working with your metal building supplier and industry authorities to fully comprehend its implications in the design and building processes."
For further details, contact MBMA at (216) 241-7333 or visit www.mbma.com. Or contact the California Energy Commission at (916) 654-4287 or visit www.energy.ca.gov.
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