Energy

Written by R. Kirk Johnson, AIA, LEED AP

The third edition public draft of the long awaited Standard 189.1P Standard for the Design of High-Performance Green Buildings except low-rise residential buildings was released in May with a plan to finalize and publish the standard incorporating applicable public comments by January 2010.  The standard, upon completion, is a joint partnership between the U.S. Green Building Council (USGBC), the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), and the Illuminating Engineering Society of North America (IESNA).  The standard is designed to significantly move forward sustainable concepts and construction by providing a code-enforceable standard for green buildings that may be adopted by jurisdictions, agencies, clients, rating systems, and regulatory entities.  It is designed to set the minimum requirements for high performance buildings.

 

According to the proposed standard, a high performance green building is defined as “a building designed, constructed, and capable of being operated in a manner which increases environmental performance and economic value over time, seeks to establish an indoor environment that supports the health of occupants, and enhances satisfaction and productivity of workers through integration of environmentally-preferable building materials, and water-efficient and energy-efficient systems.”  The new high performance standard is built around sustainable concepts found in the USGBC LEED Rating Systems and designed to work in conjunction with existing published ASHRAE/IESNA standards such as Standard 90.1-2007, and additional ASHRAE standards such as 62.1-2007 and 55-2004.  Although the ASHRAE standards address energy, ventilation, and humidity requirements in buildings, Standard 189 addresses a broader perspective that encompasses many areas such as site sustainability, water use efficiency, energy efficiency, indoor environmental quality, and building impact upon atmosphere, materials, and resources.  Additionally, the standard delineates building construction and operation protocols.  In essence, the standard is a code enforceable evolutionary confluence of the LEED NC Rating System, LEED CI, LEED EB Rating System, and ASHRAE 90.1, 62.1, and 55.1 regulations.  As a result of these measures, the proposed high performance standard may be used as a roadmap for options for increasing building and site efficiencies.

ORGANIZATION

A quick glance at the beginning of the Public Draft states that the standard is designed for high-performance buildings and is written in code enforceable normative language.  It is therefore developed as a building regulation code rather than a supplementary sustainable rating system.  This distinction is important primarily due to the fact that the document can be adopted as a building code independently of other sustainable criteria.

Each chapter contains five key components such as general requirements, compliance paths, mandatory provisions, prescriptive options, and performance options.  The standard, upon adoption will be revised at three year intervals and updated via addenda to the standard similar to the present protocol with other ASHRAE standards.

PURPOSE AND SCOPE

According to the authors of the proposed high performance regulation, the standard is designed to provide “minimum requirements for the siting, design, construction, and plan for operation of high performance green buildings.”  The operative words are “high performance”.  This distinction is important as it differentiates the standard from normative construction codes.  However, the standard may also be used as a basis for future rating system drafts or as a foundation for other model codes.  In the proposed Standard 189P standard, particular attention is given to two overriding concepts.

• Balance environmental responsibility, resource efficiency, occupant comfort and well being, and community sensitivity.
• Support the goal of development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

ENERGY OPTIMIZATION

Although many elements are covered in the standard, this brief article concentrates upon specific energy improvements that are listed in the Standard 189 Public Draft Three dated May 2009.  In general, the standard works in concert with the published ASHRAE 90.1-2007, 62.1-2007, and 55-2004 standards as a preliminary prerequisite for compliance to these regulations.  However, Standard 189P goes beyond these requirements by superseding the regulations in a large majority of instances.  The regulations that vary in the standard from the ASHRAE 90.1-2007 version are specifically listed in the narrative.  The items that are the same as ASHRAE 90.1 are not specifically listed as they are required as a overall compliance prerequisite.

At the end of the day, the standard from an energy perspective is designed to increase the overall energy performance savings up to 25% higher than those required in ASHRAE 90.1-2007.  This in turn is designed to compliment an overall energy reduction goal of 30% above ASHRAE 90.1-2004.  As a point of reference, the ASHRAE 90.1-2010 version share similar energy reduction goals.  Both of these are foundational to the overarching energy and carbon reduction goals contained in the 2030 challenge adopted by many Mayors across the country.

The scope of energy efficiency measures included in the Standard 189P Public Draft covers specific requirements for energy efficiency for buildings, appliances, on-site renewable energy systems, and energy measurement.  In order to comply with the standard, basic mandatory requirements must be met along with either a prescriptive or performance option.

MANDATORY REQUIREMENTS
Three mandatory provisions included in the proposed standard are required as energy compliance prerequisites to the system.  Mandatory provisions are required for the following.

• AHSRAE/IESNA Standard 90.1-2007 compliance (sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4).
• On-site renewable Energy Systems incorporation.  Provisions must be made for future or present installations of on-site renewable energy systems with a minimum rating of 13 BTU/SF multiplied by the total square footage of roof area.
• Energy Consumption Measurement + Management of both system typologies and sub-system categories are required.  System typologies include items such as electric service, on-site renewable power, gas and district services, geothermal energy, and renewable thermal energy.

Examples of sub-system categories include HVAC systems, people moving systems, lighting loads, process loads, and plug loads.  The energy consumption data must automatically communicate hourly and daily to the data acquisition system.  It must also be storable and retrievable with the ability to publish energy consumption reports of various capacities.

PRESCRIPTIVE OPTION REQUIREMENTS
As mentioned previously, the proposed Standard 189 requires adherence to either prescriptive criteria measures or to an overall performance guided measurement.  Section 7.4 of the standard lists the requirements for the additive prescriptive compliance option.  All measures in this section supersede the requirements contained in the ASHRAE 90.1-2007 standard.  Satisfactorily meeting the thresholds contained in the prescriptive option method meets the energy compliance of the standard as well as meeting the overall approximate 25% energy reduction goal of the standard.  The prescriptive option requires adherence to the following general categories.

• On-Site Renewable Energy Systems
• Building Envelope
• HVAC
• Service Water Heating
• Power
• Lighting
• Equipment

Some of the specific requirements contained in Section 7.4 of the regulation are discussed below.

ON-SITE RENEWABLE ENERGY SYSTEMS

Under the standard, building projects are required to provide on-site renewable energy systems providing an annual energy production equivalent of 4.0 KBtu/SF of conditioned space.  Exceptions are provided for providing both exterior renewable flat plat collectors and with the purchase of renewable electricity products into the building project.

BUILDING ENVELOPE

The building envelope requirements in Standard 189 are more stringent than ASHRAE 90.1-2007.  Some primary areas that are addressed are roof insulation (R-25 ci minimum), vertical fenestration area (40% maximum fenestration to gross wall area requirement), permanent projections (vertical fenestration required to have a minimum permanent project factor of 0.50), vertical fenestration SHGC (0.25 maximum for all elevations), vestibules, fenestration orientation (maximum solar orientation angle is provided by mathematical calculations), and a continuous air barrier requirement.

HVAC

Minimum equipment efficiencies are required for equipment compliance to either an Energy Policy Act baseline, Energy Star, or to higher adjusted requirements than ASHRAE 90.1-2007.  Demand control ventilation is required for highly densified occupant areas.  Ducts and plenums shall be sealed by more stringent requirements.  Economizers are required for more buildings along with higher performance criteria.  Additional zone controls, fan system power limits, additional system controls, and exhaust air energy recovery requirements are provided.  Additional service water heating requirements are listed.

Perhaps three of the most performance optimization HVAC system measures included in the standard is in the form of peak load reduction, lighting power density adjustments, and occupancy sensor requirements.  Under the provisions, buildings shall reduce peak load building demand through the use of demand limiting or load shifting automatic systems.  Lighting power densities are required to reduce by a minimum of 10% over ASHRAE 90.1-2007 standards.  Occupancy sensors are required in many more spaces than previous regulations.  Automatic controls for lighting in daylight zones around the perimeter fenestration areas are required under the proposed regulation.  Automatic controls for outdoor lighting are also required.  Another measure is the requirement for Energy Star equipment compliance for a large majority of the project.

PERFORMANCE OPTION REQUIREMENTS
In lieu of using the optional prescriptive measures described previously, the proposed Standard 189 allows the compliance to a performative standard.  This is similar to the previous Appendix G, Performance Model Analysis found under ASHRAE 90.1-2007.  The methodology is simpler in this case and is also the same as required for LEED certification submittals for Energy and Atmosphere credit 1 (EA c1).  As a result, the majority of LEED Certified projects will probably use this option.  Under the Performance Option of the Standard, the following additive three basic criteria must be met.

• Annual Energy Cost Compliance
• Carbon Dioxide Equivalent Compliance
• Load Factor/Peak Demand Compliance