We request the USGBC confirm our understanding that the 90.1-1999 ECBM and LEED modeling protocol allows us to receive credit for EAc1 energy cost savings for desuperheaters recovering heat from water source heat pump compressors, and using this heat to preheat service water heating, and that this can be done without an Exceptional Calculation, with the supporting discussion below. We understand that the heat recovery method would qualify as site-recovered energy as discussed under section 11.2.3 and its Exception, and is not included in the design energy cost, and the equivalent usage is met in the budget model by the backup energy source, which is electricity. Therefore, the measure is eligible for savings credit and to be modeled differently in the design model from the budget model. The desuperheaters and their heat recovery to service water heating can be readily modeled within eQuest and its computational engine, DOE-2.2, and therefore do not become an exceptional calculation for that reason. Therefore, the measure appears eligible for savings credit, and does not seem to require an exceptional calculation. Is this approach considered acceptable?
The applicant is requesting clarification regarding whether desuperheaters must be modeled using the exceptional calculation methodology when the energy software program used for EAc1 compliance is capable of modeling heat recovery. The exceptional calculation methodology is only required when one of the following conditions are met: 1. The simulation program being used for the LEED EAc1 calculations cannot adequately model a design material or device 2. Input parameters that ASHRAE 90.1 requires to be modeled identically in the budget and proposed case must be modified to show the impact of the efficiency measure (e.g. schedule changes must be used to demonstrate improved efficiency, such as for demand control ventilation). 3. Previous LEED CIRs have mandated the use of the exceptional calculation methodology (e.g. - eQUEST is capable of modeling demand controlled ventilation, but since eQUEST accomplishes this by internally editing schedule values, the exceptional calculation methodology is still required for LEED v2.1 projects). In the case of desuperheaters, ASHRAE 90.1-1999 specifically requires condenser heat recovery to preheat service hot water under certain conditions (Section 6.3.6.2). Since heat recovery is prescriptively required under certain conditions, and since the software is capable of modeling desuperheaters without the use of supplemental spreadsheet calculations, the measure may be modeled without using the exceptional calculation method. The applicant should be sure to include all input assumptions regarding the desuperheaters in the input comparison table, and should provide sufficient information to confirm that condenser heat recovery does not have to be modeled in the budget case under the requirements of section 6.3.6.2. Applicable Internationally.