Proposed standard ups green ante

ASHRAE Standard 189P (Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings) has been proposed to drive green building into mainstream building practices. It is based on the USGBC LEED rating system, and is intended to become a prerequisite for LEED certification. It will apply to newcommercial buildings and major renovation projects, and will address key areas of performance, including energy efficiency, greenhouse gas emissions, sustainable site selection, water usage, materials and resources, and indoor environmental quality.

Standard 189P aims to achieve a minimum of 30% reduction in energy costs and carbon dioxide equivalents (CO2e) over ASHRAE Standard 90.1-2007. CO2e is the internationally recognized measure of greenhouse emissions and thus global warming potential.

However, there still is work to do on the standard. For example, among the mandatory provisions of 189P is a requirement for on-site renewable energy power systems (REPS) that requires all building projects to have a REPS rating of 1% or more of the service overcurrent protection device (OCPD) rating. Consequently, a building with an 800-amp OCPD (288 kW) would require a 2.9-kW REPS. This is a step in the right direction, as an on-site renewable energy system is a powerful tool for creating low- and zero-energy buildings.

There are exceptions to this requirement: 1) to include a solar water heating system on-site that provides 100% of the domestic hot water needs or has a peak capacity equivalent to 2.5% or more of the building service OCPD rating; and 2) to demonstrate compliance via the performance option (i.e., energy modeling) and provide any combination of energy cost and CO2e savings achieving a minimum of 10% total.

There are a couple of issues with these exceptions. As for exception 1, it is practically and economically impossible to design and install a solar water heating system that satisfies 100% of the domestic hot water needs. Some form of supplemental heat is needed for those inevitable consecutive cloudy days.eems incongruous, with CO2e relating directly to energy consumption, not energy cost. Energy consumption should be the basis for each.

Reducing energy cost under exception 2 is a combination of reducing energy consumption and playing the utility rate game. Reducing energy consumption begins with the siting of the building to harvest passive energy sources and focusing on reducing building envelope loads as much as practical. Typically, the greatest opportunities for energy reduction are in improvements in glazing and wall insulation. Engineers first must manage building internal gains and select efficient equipment. Then they can select on-site renewable and nonrenewable mechanical energy systems to meet the reduced energy requirement. When designing an on-site renewable energy system, look to integrate the system into the building. For example, solar panels can double as window overhangs or as the roof of covered parking structures.

ASHRAE still has some work to do in cleaning up the renewable energy requirement in 189P, but it is clearly a step in the right direction. In many areas of the country, the economics and business marketing potential for solar energy applications in buildings have never been better.

Author Information

D’Antonio is a provider of energy and environmental efficiency in buildings. He is a member of Consulting-Specifying Engineer ’s editorial advisory board and a “40 Under 40” honoree in this issue.

AT A GLANCE

Proposed Standard 189P, for the design of high-performance green buildings, underwent its second public review in spring 2008. The 189P committee is reviewing the latest round of comments. Depending on the number and extent of changes to be made, the 189P standard will either go into a third public review or be published. ASHRAE officials hope that the next action on 189P will take place at the ASHRAE Winter Meeting in January 2009.

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