Hi, we are having issues passing our blower door tests and have been presented with the alternative compliance path below, does anyone have experience with this approach?

Tracer gas testing will be performed using an infrared spectrophotometer. Originally approved in LEED NC v 2.1 and 2.2 as an optional compliance path for Environmental Tobacco Smoke Control, the method utilizes a portable spectrophotometer capable of quantifying a variety of gases in the part per billion range. Nitrous oxide was selected as the tracer gas since traditional studies using sulfur hexafluoride have been deemed a potent greenhouse gas contributor. The analyzer is capable of detecting nitrous oxide levels down to an estimated 60 parts per billion (ppb). While nitrous oxide is an anesthetic gas, dosing levels may be set well below occupational exposure standards (25,000 ppb recommended 8 hr exposure limit). A dosing target of 10,000 ppb will be achieved through constant gas injection to steady state conditions (varying <8%). To achieve the desired differential between the dosing range and leak detection requirement of <1%, the leak criteria for surrounding spaces will be at <100 ppb, well within the detection range of the instrument.

The tracer gas testing will follow dosing criteria as described in Section 9 of ASTM E741 (“Constant injection test method”) and ASHRAE Standard 129, Section 6.4 describing a “Test of infiltration and air exchange with adjoining spaces,” but instead of monitoring decay rates of the tracer gas to calculate air exchange or age-of-air, the proposed tracer gas testing procedures measure the presence of tracer gas in adjacent units as a marker for infiltration.  Furthermore, the proposed methodology is aligned with the CEN Standard EN 1779, Section 2 outlining the “Knowledge required for selecting a testing method”, as well as the considerations listed for detectability, applicability and appropriate techniques in Sections 3 and 4 of the Standard. 

In order to confirm that unit configuration does not affect the pressure relationships and construction practices are consistent throughout the project site, residential units will be grouped together based on similar layouts (eg. bedrooms and square footage).  Testing/dosing will occur in 1 in 7 similar units in each group, resulting in 22 groups and a total of 34 testing/dosing locations in the complex.  The residential units will be tested with all the doors and windows closed, and the HVAC systems under normal operating conditions. The tracer gas will be released at breathing height in a centrally located area within the dosing unit. Following steady state conditions in the dosing unit, leak tests will be completed on all adjoining residential units (above, below and to each side, where applicable) for a minimum of 5 minutes using a second spectrophotometer to establish if leak criteria is confirmed.  Readings will be taken at 30-second intervals in each sensing location (adjoining unit) over the 5 minute period. Throughout the testing, steady state conditions in the dosing unit will be confirmed using the spectrophotometer.

The proposed infrared spectrophotometer can be calibrated to monitor tracer concentrations in the part per billion range (a fraction of the dosing concentration) in adjacent rooms to monitor for unwanted infiltration to adjacent spaces.  

Passing criteria is based on the modeling of negligible exchange of air between the dosing unit and adjacent testing units, which is defined as <1% of the dosing gas under the specific environmental conditions of the test.  This method will result in measurements that properly reflect the sufficient sealing of the walls, floors and ceilings of the residential units, thus mitigating the transfer of ETS between units.  The proposed tracer gas testing methodology meets the intent of the LEED prerequisite and provides robust quantitative data. 

A report will be provided documenting the groupings, locations, test methodology, results, and conclusions.  The results will consist of the dosing unit concentration, test unit concentration, % leakage, and whether or not the requirement has been met.