Duct Sealing

Keep Unwanted Heat Outside by Sealing

Get an energy audit.

Before you prepare to remodel, find out how efficient your building is already working. Contact an energy efficiency auditor to test how badly the air ducts leak, and consider getting a “blower door” test to see how much air leaks in and out through cracks, outlets, windows, and doors.



What can I do about it?

Seal and insulate existing ducts.

Start by sealing duct leaks using mastic sealant or metal tape and insulating all the ducts that you can access. Also, make sure that the connections at vents and registers are well-sealed where they meet the floors, walls, and ceiling.




As part of preparing to remodel, find out how the building is already working – test the ducts to look for leakage, perhaps do a “blower door” test to see how much air leaks into (or out of) the building through cracks, electrical outlets, windows and doors. Additionally, some remedial work such as duct and “air sealing” may be warranted and cost effective.

Blower Door Test


A duct leakage test is now part of the Energy Code requirements in most improvement cases. State code requires duct leakage be no greater than 6%.

The leakage test helps ensure the work is done properly.

Funded by the Local Government Strategic Plan Strategies Program

under the auspices of the California Public Utilities Commission.

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