The Washington State Department of Commerce has released, "Evergreen Sustainable Development Standard Version 3.0." Below are notes as related to residential airtightness testing:


Section 5.11: Airchange on rehab gets 3 pts for 7 ACH and 7 pts for 5 ACH.  This could be difficult in some types of houses. Key step, is to find all the attic leaks around plumbing stack vents and chimneys that can be sealed off with foamboard, foam and sheet metal for chimneys. Then wiring penetrations and pot lights that must all be replaced with sealed LED units to save on leakage and  power. This work is most easily done by removing the insulation which will allow the tops of all wals to be sealed between the 2x4 and sheetrock.  All open joist ends must be blocked and sealed. Then look at joist spaces in the basement that should all be foamed. DOE has a Bypass Guide that shows you where to look and what to do.


Section 5.12: Duct leakage set to 0.1 CFM50/sq ft = 6.4 CFM25/100 sq ft where IECC 2009 is 12 and 2015 is 4. So about half way. Gets 10 pts for rehab. Should be easily attainable by sealing all the boots to the sheetrock, the collars and connectors and the cabinet. Then look for duct leaks using a pressure pan which should then show them up quickly. Or, 50% reduction in outdoor leakage which means it must be done before and after requiring a blower door and duct tester.


Measure pressure drop across the blower to ensure it’s in its performance range; usually under 0.5 inches and if too high the ducts need to be increased or unit downsized which is often the best approach. Ducts between floors where they’re using joist spaces as plenum can only be sealed well using AeroSeal which is expensive but effective.