Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.0

Inquiry

We are submitting the following appeal to the USGBC Project Manager\'\'s Ruling of a CIR in the Energy and Atmosphere category, Credit EA-1. The Credit Interpretation Request was submitted on 7/17/2002 for the Valley View School District 365U. The issue raised was whether exceptions are allowed in the ASHRAE 90.1 Energy Cost Budget (ECB) methodology to allow for comparisons of different HVAC system types - specifically when a higher performing system has been selected over a less efficient system that would typically be used for a particular building type. The Project Manager\'\'s Ruling states that the answer is no, although one exception is allowed for equipment with less than 150 tons of cooling capacity. While we are not appealing the specific scenario of this CIR (i.e., whether packaged rooftop units can be compared to water-cooled chillers for a school) we are appealing the broader reasoning that allows only one exception to the ASHRAE ECB methodology. As the Project Manager\'s ruling states, the LEED program allows the following exception to the ASHRAE ECB methodology: air-cooled chillers can be used in the baseline for water cooled chiller designs if chiller capacity is less than 150 tons. This exception clearly rewards projects for choosing a more efficient system type, as opposed to more efficient equipment within the same system type. The LEED 2.0 Reference Guide notes that this exception "encourages the switch to more efficient water based cooling over air cooling in smaller equipment sizes." We applaud this reasoning, as it supports the overall LEED program goals of transforming market practices and encouraging investment in high-performance buildings. However, we feel the logic of the one exception should be extended to recognize other similar situations where different HVAC system types are involved. For our building type (a high-rise residential building), it is by far the norm to use through-the-wall direct expansion (DX) air conditioning units as the means of cooling individual apartments (the individual units are normally 1 ton or less in capacity, with one or more units installed per apartment, depending on size). In our project, a deliberate decision was made to use a much more expensive central cooling system, using gas-fired double-effect absorption chillers (one 420 ton unit and one 380 ton unit) with cooling towers. From an ASHRAE 90.1 ECB standpoint, we are required to compare the double-effect absorption chillers to an equivalent system, which is, in fact, double-effect absorption chillers. This gives the project practically no savings for the chillers, as all double-effect absorption chillers operate within the same efficiency range. With the current ruling in place, we therefore have the following paradoxical situation: if a multi-family residence has a typical through-the-wall DX system, but specifies more efficient units, LEED acknowledges the energy savings. However, if the multi-family residence has an absorption chiller plant, which is more energy efficient than any through-the-wall DX system, LEED acknowledges no energy savings for the plant. This situation contravenes the USGBC\'s mission and, we submit, is a very high price to pay for the sake of consistency. Because of this situation, we are making the case that, for high-rise multi-family residential buildings, the basis of comparison for HVAC should be the predominant standard of through-the-wall DX units. A ruling by the USGBC in favor of this request will support efforts to transform the market for multi-family residences away from inefficient, air-cooled DX systems. In addition to increased energy-efficiency in cooling the building, such a move will have the following additional benefits: