Raleigh Housing Authority Duct Sealing Evaluation

In multifamily and attached buildings, manual duct sealing methods are often impractical or very costly and disruptive because of the difficulty in accessing leakage sites. In this project, two retrofit duct sealing techniques manually applied sealants and injecting a spray sealant (Aeroseal) in combination with some manual sealing were implemented in several low-rise multi-unit buildings in North Carolina. An analysis of the cost and performance of the two methods is presented. Each method was used in 20 housing units: approximately half of each group of units are single story and the remainder are two story. Results show that duct leakage to the outside was reduced by an average of 59% through the use of manual methods, and by 90% in the units where a combination of injected spray sealant and manual sealing was used. Some of this difference is likely due to the fact that injected spray sealing reached portions of the duct system that were inaccessible to manual methods. It was found that 73% of the leakage reduction in homes that were treated with injected spray sealant was attributable to the manual sealing done at boots, returns, and the air handler.

The cost of manually applying sealant ranged from $275 to $511 per unit and for the Aeroseal treated ducts the cost was $700 per unit. Utility bills were collected and compared for 1 year before and after the retrofits for each unit. Energy savings based on utility bills were within 25%-50% of those predicted by the models for most unit types. Utility bill analysis shows 14% and 16% energy savings using the Aeroseal and hand sealing procedures, respectively, in heating season whereas in cooling season, energy savings using Aeroseal and hand sealing were both 16%. Average simple payback based on utility bills was 2.2 years for manual units and 4.7 years for the Aeroseal units. Only 18 of 40 units had usable utility bills.

Berkshire Village Court - House Count - 4: Single Story, Hand sealed ducts; Single Story, Aeroseal Ducting; 2-Story, Hand Sealed ducts; 2-Story, Aeroseal ducts
Terrace Park Court - House Count - 2: Single Story, Hand sealed ducts; Double Story, Hand sealed ducting
Winter Park Court - House Count - 2: Single Story, Hand sealed ducts, Aeroseal sealed ducting; Double Story, Aeroseal ducting