Duct Sealant

Technical Resources Bulletin
March 27, 2009 TRB #4-09
To: SMACNA Members
From: Technical Resources Department
Subject: HVAC Duct Sealant Usage Requirements on USGBC LEED® Projects
The purpose of this bulletin is to clarify the use of duct sealant for United States Green Building Council (USGBC) LEED® projects and describe the current sealant usage requirements and typical issues associated with those requirements.
When addressing duct sealant, LEED® references South Coast Air Quality Management District (SCAQMD) Rule 1168. HVAC duct sealer is not specifically addressed or categorized in Rule 1168, and that has led to some confusion.
SMACNA contacted SCAQMD to determine which category under Rule 1168 covers HVAC duct sealant. SCAQMD stated that they consider HVAC duct sealant to be an “Architectural” sealant, which limits the VOCs to 250 g/l, and not part of the “Other” category which allows a VOC limit of 420 g/l. Sealants compliant with the 250 g/l VOC restriction tend to be water-based. Use of these sealants pose a significant performance issue for contractors when temperatures go below 40°F (5°C), particularly in new construction when ductwork is installed in unenclosed buildings. These sealants cannot be applied at temperatures at or below 40°F (5°C) nor can they be exposed to temperatures below 40°F (5°C) until the product fully cures, typically 24-48 hours. The sealants that can be applied at temperatures below 40°F (5°C) are solvent-based and typically have VOC levels around 300 g/l. This makes them unacceptable per LEED® requirements since LEED® classifies them as an “Architectural” sealant with VOC limits of 250 g/l. Therein lies the problem for contractors: use a LEED®-compliant sealant and have the sealant fail or use a sealant that works, but will not meet LEED® requirements.

To make SMACMA’s bulletin official, USGBC addressed duct sealants in LI#5241 (http://www.usgbc.org/leed-interpretations?keys=5241): “Project teams may classify duct sealants under ‘Other’, as listed in the SCAQMD VOC Limits table.”