For your ducts, you must use duct putty. This is a sticky material that seals joints once the gaps have been reinforced with sheet metal screws and fiberglass mesh tape. Aluminum foil tape (also known as “roll adhesive tape”) is easier and less dirty, but it tends to fail faster due to delamination and dirt and grease in the ducts. Despite the mess, the putty is more durable and It is preferred by most contractors.
All the ducts leaked water into the house because the putty I applied 9 months ago was very worn on the top of the ducts. Response to Sean Sean: Although you post your question on a blog about putty and adhesive tape, it seems that your question refers to another blog. Third response to Mike C Mike, Your plan to clean the ducts and then install putty and insulation for the ducts sounds good. Unfortunately, however, few building inspectors outside of California bother to enforce existing code requirements that require residential duct joints to be sealed with high-quality putty or adhesive tape.
Basically, I used duct putty to seal the boots on the attic floors and then sealed the boots on the ceiling of my living room (before putting the grills back on).
