Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.0

Inquiry

2. Optimize Energy Performance -- Credit EA1 - Credit Interpretation Request - Air leakage reduction Windows: ASHRAE 90.1 does not allow credit for air leakage reduction. However, it does indicate that windows are allowed to have 1 cfm per square foot air leakage (at 0.30" water.) The windows we are using in this project are very high performance, with significantly lower air leakage rates. The manufacturer has supplied test results indicating the tested air leakage rate. Further, we are using a blower door and infra-red camera simultaneously to locate and seal any air leaks in the window system that result from installation. We propose to take credit for this air leakage reduction, with the following methodology: The tested air leakage rate at 0.30" can be established for the windows as installed, based on manufacturer\'s data, and for the base case windows based on ASHRAE 90.1. Both these values will be extrapolated to expected winter heating season air leakage rate, using the LBL correlation for blower door test data. We have run two blower door tests, and will use the most recent (during which most of the air leakage has been taken care of) test data to establish the relationship between the air leakage rate at 0.30" static pressure (75 Pa) and the average heating season air leakage rate, which is calculated at the building pressure established by the LBL correlation, which is based, in part, on the exposure of the building to wind. In this case exposure is significant, as the building is on the shore of Lake Champlain, fully exposed on the west side of the building to windows ranging from south to west to north. We then propose to run the base case building, in the energy modeling, using TRACE, with the air leakage rate for the windows established in the above manner. The building as built would be modeled with zero air leakage rate. Preliminary estimates indicate that the difference in overall extrapolate natural air leakage rates in 0.04 air changes per hour, at typical heating season winter conditions. Blower door guided air leakage reduction: A significant effort at air sealing is part of the energy saving strategy for this building. With the location noted above, air leakage reduction is particularly important. Two blower door tests with simultaneous infrared scanning, have been completed. The first identified a number of areas that were not complete as designed. Most of these were completed by the time of the second test, and a number of areas were identified during the second test that, in my opinion, would not have subsequently been air sealed had this procedure not been in place. A list of further items was developed from this second air leakage test, and this list has been circulated by the GC to responsible parties, who will sign off when they have completed the items. When those items are complete, a third, and hopefully final, blower test will be conducted. We propose to take credit in our energy calculations for the air leakage reduction between the second and third blower door tests, using the LBL correlation to extrapolate to typical heating and cooling season air leakage rates, as described in number 2 above. The extrapolated seasonal air leakage rate reduction would be applied to the base case building. For example, if the extrapolated air leakage reduction were 0.1 heating season air changes per hour from blower door test #2 to test #3, we would assign 0.1 ACH to the base case building and zero air leakage to the building as built. We feel that this third round of testing and air leakage reduction is well beyond typical attention paid to air leakage, that air leakage control is particularly important in this very cold (7700 degree-day) climate and at this exposed site, and that we have demonstrated a method using accepted principals to quantify the savings. Blower door test results and LBL correlation spreadsheets for each test would be provided as part of the submission. We would also submit the list of items to be air sealed as part of the final air leakage reduction package. Windows and air leakage reduction together: We propose to add the two air leakage reductions - from window improvements and blower-door-guided air leakage reduction. For example, if the blower-door-guided heating season air leakage rate reduction were 0.1 ACH and the window air leakage reduction were 0.04 ACH, the base case building would be modeled at 0.14 ACH and the building as built at 0.0 ACH.)