How To Seal Attic Air Leaks

By Robert Robillard on Energy Saving

Air Leaks Rob Heat-Retaining Efficiency

Adding insulation in your attic can drastically help reduce your heating and cooling bills each month.

Lack of attic insulation and air leaks are usually the biggest offender for heat loss in a home.

This article will teach your how to seal attic air leaks and save money on your energy bills.

Sealing Air Leaks:  Start in the Attic:

The attic is a perfect place for hot and cold air to leak in and out.  With no air leaks and proper insulation, your attic can provide you with an energy efficient home.

A client of mine recently had an energy audit to their 20 year old home. This was done by the Concord Municipal Lightinsulating and attic Plant.

One of the suggestions was to add at 10″ of R-30 insulation in the attic.  The survey specified that the savings was $ 106.42 for 32.75 gallons of number 2 heating fuel with an estimated 7.52 year payback.

Tax Benefit

Our lesson in how to seal attic air leaks is a further benefit to the homeowner because it is eligible for a tax credit for installing the insulation.

Homeowners are eligible for a tax credit of 10% of cost up to $500 or a specific amount from $50–$300 for qualified energy efficiency improvements made to their homes.

Air Leak Sealing

I suggested that the client also let me check for and seal any air leaks. See post on air leaks Adding attic insulation and air leak sealing was our plan of action.

Sealing Attic Air Leaks:

We spent the first hour peeling back the existing insulation and looking for wire penetrations, plumbing vent pipes, electrical light boxes and recessed lights.

We used cans of triple expanding foam to seal all of these leaks.

Examples of air leaks:

  • Wire penetrations
  • Pipe penetrations
  • Openings at partition walls
  • Sofit openings
  • Openings around chimneys
  • At and around recessed lights and fans

Recessed Lights:

There were two recessed lights that were not insulated and IC rated.

For fire safety reasons, insulation needs to be kept back from these fixtures making them a poor choice in attics.

To remedy this issue we built insulated boxes to cover these lights but far enough away to avoid a fire safety issue


Recessed Light Insulation Box:

We dealt with these two lights by building a box around and on top of them with 1″ thick, R-6.5, foil rigid insulation board.

We then insulated up to and also over the light boxes to ensure we achieved a better R value.

Sofit Ventilation

We added additional “Proper Vent” baffles to  extend up and past the new insulation we added to the attic.

Adding Insulation

To achieve a better R value we added 10-inches or un-faced 24″ wide fiberglass insulation perpendicular to the existing 8″ insulation in this attic.

Batten Down The Hatches

Attic hatches are a MAJOR source of air leaks and heat loss.

We installed 1″ foil board to the attic hatch door and weather stripped the opening seams.

Prior to leaving the attic we overlapped the hatch with fiberglass insulation. [see bottom photo]

Learning how to seal attic air leaks is a straightforward and simple process and one that will pay dividends in the heating and  cooling bills.

Ice Dam Reduction

Sealing air leaks in conjunction with  adding insulation in your attic can drastically help reduce your chances of developing ice dams.

A Comprehensive Approach

Learning how to seal attic air leaks is a comprehensive approach.  You need to look at how the home is constructed and sometimes even remove insulation bay by bay to track down leak locations.

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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