Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Although no longer published in the current ASHRAE Handbook of Fundamentals (HOF), the 1997 version included a 1 page table in Chapter 25 that provided Best Estimates, Minimum Estimates, and Maximum Estimates of Eeextive Leakage Areas of over 100 different building elements. The table is described as applicable to low-rise residential, and states that ELA are are based on a pressure differential of 0.016 inches H2O and a Cd of 1.0
I recall seeing this table (or a variant of it) included in Wrightsoft software, used to fully document the determination of initial and final building level ELA. I have also seen custom spreadsheets which used this table, or a variant of it, to accomplish the same. While certainly not perfect, it is the best example I can point towards for the development of a transparent estimate of ELA, pre and post.
At the other extreme, I am aware that Canam/ZeroDraft uses a hybrid inverse/forward model (proprietary software) called ALCAP which performs monthly savings estimates of savings (peak demand and consumption) associated with descriptive infiltration improvements. Some of the algorithms used in ALCAP are described here: http://www.regie-energie.qc.ca/audiences/3671-08/MemoiresPreuves_3671-08/C-9-12_GRAME-1_Annex7_3671_14nov08.pdf
Canam/ZeroDraft has claimed that the ALCAP calculation methodology is both conservative in nature and has been validated via numerous case studies. They certainly have the experience and data to mine from many, many projects. At a first glance, it does not seem difficult to extend the basic ALCAP approach to calculate infiltration savings estimates at a daily level, based on unique daily operations. This might be useful to generate upper/lower bounding levels for savings that could be claimed.
I personally think from a practical perspective, in addition to transparency, our community needs open-source tools that can provide a layer of quality assurance on top of our savings estimates, to prevent excessive claims of savings performance which cannot be substantiated without great expense, such as infiltration reduction. Perhaps these two methods can be applied in creative ways to help us move closer towards this.
