Air Sealing


Inadequately sealed building envelopes can lead to air leakage occurs or the movement of unconditioned air into and out of conditioned spaces. This process, known as air leakage, decreases the comfort of a building by using natural airflow and allowing moisture, drafts, and undesired noise to enter. It applies to any holes, cracks, or gaps in the building envelope. It is important to control air movement in buildings because research indicates that air leakage can cause huge energy losses, accounting for up to a third of a home’s energy use. Air leakage may also reduce indoor air quality by permitting dust and airborne pollutants to infiltrate the building.

Air Leakage

air leakage home

Air leakage is the outdoor air that enters and indoor air that leaves home through cracks and openings. Don’t let air leakage provide your house with natural ventilation. On cold or windy days, too much fresh air may enter a house. But on non-windy or cold days, too little air may enter a house. Indoor air may become stagnant and polluted. Air leakage also can cause moisture problems which cause occupant discomfort and poor indoor air quality. Cracks and openings are sealed to reduce drafts and keep cold air spots improving comfort.

The best way is to control leakage home air sealing and provide controlled air leaking and ventilation where needed. Before air sealing, you shall:

Locate air leaks Check out air sealing your home needs for ventilation to keep indoor air quality. You can install air-sealing materials and techniques, like caulk and weatherstripping. If you have a larger home remodel and some construction is involved, consider some of the new home construction air sealing techniques and have a home energy assessment done to find all the air leak and the opportunities to save energy and money in your home.


Can You Air Seal Your Home Without Adding Insulation?

Yes, you can air seal your home without adding insulation outside air well, but they are usually done together—and for good reason.

The Importance of Air Sealing
Air sealing your home is an essential process for enhancing your home’s energy efficiency. It involves identifying and sealing gaps, cracks, and openings that allow air to leak in and out of your home. This process can significantly reduce your energy bills, improve indoor air quality, and make your home more comfortable by eliminating drafts.

The Role of Insulation
Insulation, on the other hand, acts as a barrier to heat flow and is crucial for maintaining a consistent temperature within your home in cold climate. Proper insulation ensures that your heating and cooling systems do not have to work as hard to keep warm air within your home at a comfortable temperature, which further reduces energy consumption and costs.

Why Air Sealing and Insulation Work Best Together
While air sealing can provide immediate benefits, combining it with proper insulation maximizes your home’s energy efficiency. Here’s why:

  1. Temperature Regulation: Even if you have sealed all the air leaks in your home, without adequate insulation, your home will still be vulnerable to temperature fluctuations. In the summer, your home could become stuffy, and in the winter, it could remain cold despite your heating efforts. This is because insulation is responsible for reducing heat transfer, keeping your home warm in the winter and cool in the summer.
  2. Energy Efficiency: Air sealing without insulation might stop drafts, but it won’t address heat loss or gain through the walls, roof, and floors. Proper insulation works in tandem with air sealing to create a more comprehensive energy efficiency strategy.
  3. Comfort and Health: Air sealing can improve indoor air quality by reducing the infiltration of pollutants, allergens, and moisture. However, insulation also plays a role in preventing condensation, which can lead to mold growth and other health hazards. Together, they ensure a healthier living environment.
  4. Cost-Effectiveness: While air sealing alone can reduce energy bills, the combination of air sealing and insulation offers the best return on investment. The initial cost of adding insulation pays off through lower energy bills and increased comfort over time.

Considerations for Effective Air Sealing and Insulation

  1. Assess Current Insulation: Before starting the air sealing process, it’s crucial to evaluate the current state of your insulation. Old or deteriorated insulation should be removed and replaced to ensure maximum effectiveness.
  2. Identify Key Areas: Focus on areas prone to air leaks, such as attics, basements, around windows and doors, and where utilities enter your home. Addressing these areas can significantly improve overall efficiency.
  3. Professional Help: For the best results, consider hiring a professional energy auditor or weatherization expert. They can perform a blower door test to pinpoint air leaks and recommend the most effective insulation and air sealing solutions for your home.
  4. Quality Materials: Use high-quality caulks, weatherstripping, and insulation materials. Low-expansion spray foam is excellent for sealing small gaps, while foam boards or batts are ideal for larger spaces.

Tips for Sealing Air Leaks

To enhance your home’s ventilation system energy efficiency, cooling costs and reduce air leaks, follow these steps:

  1. Hire a Professional: Engage an energy assessor or a weatherization expert to test your home for air tightness.
  2. Seal Doors and Windows: Use caulk and weatherstripping to seal any air leaks around doors and windows.
  3. Seal Penetrations: Apply caulk and seal air leaks where plumbing, ducting, or electrical wiring penetrates through walls, floors, ceilings, and soffits.
  4. Install Foam Gaskets: Place foam gaskets behind outlet and switch plates on walls to reduce air leaks.
  5. Inspect Insulation: Check for dirty spots on insulation, which indicate air leaks and mold. Seal these leaks with low-expansion spray foam and install house flashing if needed.
  6. Check for Dirty Spots: Look for dirty areas on ceiling paint and carpet, which may indicate air leaks at interior wall/ceiling joints and wall/floor joists. Seal these with caulk.
  7. Upgrade Windows: Replace single-pane windows with double-pane, low-emissivity (low-E) windows for better insulation.
  8. Use Foam Sealant: Apply foam sealant on larger gaps around windows, baseboards, and other areas where air may escape.
  9. Ensure Dryer Vent Efficiency: Check your dryer vent to ensure it is not blocked, which saves energy and prevents potential fires.
  10. Replace Door Seals: Install new, pliable sealing gaskets on exterior door bottoms and thresholds.
  11. Manage Fireplace Flue: Keep the fireplace flue damper tightly closed when not in use to prevent air loss.
  12. Seal Around Chimneys and Vents: Use fire-resistant materials like sheet metal, sheetrock, and furnace cement caulk to seal air leaks around fireplace chimneys, furnaces, and gas-fired water heater vents.
  13. Chimney Flue Maintenance: Over time, heating and cooling can warp or break metal flues, leading to air loss. Consider using an inflatable chimney balloon to seal the flue when not in use. These balloons are durable, reusable, and deflate automatically if exposed to heat. Alternatively, create a reusable flue plug by filling a plastic trash bag with fiberglass batt scraps and jamming it into the flue. Attach a durable cord with a tag that hangs into the fireplace as a reminder and for easy removal.
  14. Consider Fireplace Upgrades: To save money and improve efficiency, replace traditional fireplaces with EPA-certified inserts installed by a certified professional.


air sealing

A building envelope constructed with proper air sealing can provide many benefits, including:

  • Increased comfort: A tighter building envelope reduces the amount of unconditioned air, drafts, noise, and moisture that enter your home. Proper air sealing will also minimize temperature differences between rooms. As a result, tight envelopes can maintain a more consistent level of comfort throughout a house.
  • Improved indoor air quality: A tighter building envelope reduces the infiltration of outdoor air pollutants, allergens, dust and radon as well as moisture infiltration from outdoor air in humid climates. Properly sealing the building envelope will also eliminate paths for pests to enter.
  • Lower utility bills: Air leakage accounts for 25% to 40% of the energy used for heating and cooling, hampering the performance of other building systems, including HVAC, fenestration, and insulation. All building systems must perform well together to optimize the energy efficiency of a home.
  • Fewer condensation problems: In hot, humid climates, moisture can enter into wall cavities through exterior cracks, resulting in mold and mildew problems that can lead to costly damage to framing and insulation. In cold climates, gaps in the interior walls allow moisture from warm indoor air to enter wall cavities and attics, which can condense on cold surfaces and lead to similar damage. Proper air sealing can significantly reduce the incidence of these problems.


Building code officials must be aware of the requirements covered in the energy code and ensure that:

  • Correct insulation is used to prevent air leakage around the building envelope
  • They are aware of the Thermal Bypass Checklist (if applicable)
  • There is caulking around all windows, skylights and doors
  • They check all bypasses into unconditioned spaces, such as attic hatches, stairwells, recessed lighting fixtures, and around bathtub enclosures, all of which are notorious for air leakage

Typical Problems

Standard issues/concerns that arise include:

  • Contractor/sub-contractor closing off an area yet to be checked
  • Not sealing where different building features meet


Requirements covered in Section 402.4 are mandatory for all climate zones.

Code History

The 2009 IECC code improved requirements for air leakage control by mandating compliance with either a visual inspection option or a testing option. The 2006 IECC made some minor improvements over the 2003 version, such as clarifying the rather ambiguous language regarding which areas required sealing and adding provisions for recessed lighting and sealed dampers for ventilation equipment (bath and kitchen fans, primarily).

Residential Policy Options

Taken from proposals for the 2012 IECC:

  • Exterior thermal envelope insulation for framed walls shall be installed in substantial contact and continuous alignment with building envelope air barrier. Breaks or joints in the air barrier shall be filled or sealed. Air permeable insulation shall not be used as a sealing material. Air permeable insulation shall be inside of an air barrier.