Mastic

Michelle, If the question is whether VOC's from mastics that are applied externally can make their way into the building and cause acute air quality issues for occupants, ... the answer is yes.  I say this based on my training as a Certified Indoor Environmentalsit as well as the contact that I've had with professional IAQ Remediators and the field-based stories that they've shared. However, LEED Residential doesn't have any mandates regarding exterior adhesives, and the last I knew, neither did commercial.  In New Mexico where I've been working, most of our projects have to air-seal the envelopes to 3 or 4 ACH to meet code.  That greatly reduces the potential for occupant exposure to externally applied products.  On the other hand, many of those projects are sealing the envelope to 4 ACH and then ventilating with an exhaust only system which creates a slight negative pressure situation that could pull VOC's through the envelope.   If it was my home, I'd rather focus on installing a balanced ventilation system and then choose exterior mastics based on their durability and moisture sealing performance.  Or better yet, I'd rather build earthen walls which could eliminate several IAQ and thermal comfort issues if engineered correctly. I hope this helps.