Our intention is to design, construct, and commission this building with an emphasis on its superior building envelope, including a tight seal at all building elements to minimize infiltration. Aggressive measures to limit infiltration of air through the building envelope have a significant impact on building performance. We propose to demonstrate the effect of a sealed building envelope by modeling a reduction in the infiltration rate between the proposed building and the budget building in the energy cost budget calculations. For the budget building, we propose the standard established in ASHRAE Fundamentals 2001, Chapter 26. ASHRAE sets the average building infiltration at .30 cfm/ft2 based on a pressure difference of 1.6 lbf/sf. The design case we will use is from the specification for our exterior wall system; this specification permits air leakage of not more than .06 cfm/sf of wall area when tested according to ASTM E 283 at a static air pressure difference of 6.24 lbf/sf. The envelope will be tested in the field with blower door tests to verify infiltration rates. We believe that reducing infiltration is consistent with the goals of the LEED program and promotes the benefits of careful building practices. As such, we request that infiltration rate be permitted as a variable in the energy cost budget calculation for optimizing energy efficiency.
This CIR seeks to use reduced infiltration rates from a superior building envelope as a variable in the energy cost budget calculation for optimizing energy efficiency. It proposes to use an ASHRAE estimate of average building infiltration from the 2001 ASHRAE Fundamentals handbook as a baseline and to demonstrate actual infiltration from a blower door test. The ASHRAE modeling protocol does not allow the infiltration rate to be changed between the budget and the design case. One of the reasons for this is that there is no current basis of comparison. The ASHRAE average infiltration rate cited is based on one study from 1976, which is most likely not representative of current envelope design. Note that window and door components are specifically addressed in Section 5.2.3.2 of ASHRAE 90.1. It is also unclear what specific sealing strategies are to be used that would go beyond good construction practice. An energy efficiency measure should not be based on simply doing well what is already required. The CIR ruling of 3/11/2003 provides some guidelines on how a case might be made for advanced air sealing. The methodology proposed for this project does not address all the issues raised in that ruling and would be insufficient to grant an exception to the modeling protocol. Applicable internationally.