Air sealing is one of the most cost-effective ways to improve your home’s energy efficiency and comfort. By sealing cracks and gaps that allow conditioned air to escape and outdoor air to leak in, you can reduce energy costs while creating a healthier indoor environment. This article will explore what air sealing entails, where common air leaks originate, benefits you can expect after sealing, and tips for prioritizing and completing an effective air sealing project.

What Does Air Sealing Mean?

Air sealing refers to the process of locating and blocking gaps and penetrations in the building envelope that allow air flow between unconditioned spaces, like attics or crawlspaces, and heated/cooled living spaces. Weather-stripping around doors and windows also falls under air sealing. Materials like caulk, spray foam, weather stripping, and other sealants are used to plug these holes to prevent air leakage. Air sealing differs from insulation in that insulation slows heat flow through building materials, while air sealing stops airflow altogether. An effective whole-house weatherization plan includes both insulation improvements and comprehensive air sealing.

Where Does Air Leakage Occur?

Air leaks can occur almost anywhere air can move between two spaces in a structure. Some of the most common sources of air leakage into homes include:

• Penetrations – Electrical/plumbing openings, cable outlets, light fixtures
• Attic/ceiling – Dropped ceiling seams, recessed lighting
• Walls – Electrical boxes, window frames, exterior cracks
• Foundation – Sill plates, rim joists, utility openings
• Doors/windows – Gaps around frames, thresholds, unfinished trims
• Ducts – Gaps in installation, unsealed returns/supplies
• Fireplace – Chimney breaches, gaps around hearth
• Fans/vents – Bath fan housings, dryer vents

Sealing these common pathways for air infiltration should be the first priority for effective air sealing projects.

Benefits of Air Sealing

Taking steps to seal air leaks provides a number of important benefits:

Energy Savings

Preventing conditioned air from escaping and outdoor air from entering means your HVAC system doesn’t have to work as hard to maintain desired indoor temperatures. Reduced air leakage can lead to 20-30% lower heating and cooling costs.

Improved Comfort
Minimizing drafts makes for an overall more comfortable living space year round. Stopping air leakage moderates indoor temperatures throughout the house.

Better Indoor Air

Quality Sealing the building envelope means less outdoor allergens and pollution find their way indoors. Keeping attic air out of living spaces also prevents insulation fibers and other particles from migrating into the home.

Moisture Control

Unwanted air movement can transport moisture into building cavities, which can lead to condensation, mold growth, and structural damage over time. Controlling air leakage mitigates this moisture movement.

Added Durability Improved air tightness places less stress on the mechanical systems. This extends the service life of furnaces, heat pumps, air conditioners and other HVAC components.

Where to Begin with Air Sealing

While a comprehensive approach to finding and sealing all possible air leaks will provide maximum benefit, starting with the easiest and most impactful steps is best for DIY projects. Some good places to start include:

• Seal attic air leaks – Heat naturally rises into the attic, making it crucial to install proper weather stripping between ceilings and attic hatches/doors. Inspect for gaps around penetrations like light fixtures, pipes, wires and address with spray foam or caulk.
• Weather strip exterior doors – A good rule of thumb is, if you can see daylight around an exterior door or feel airflow, it likely needs new weather stripping installed around the frame. Make sure to include the threshold at the bottom of the door.
• Seal window air leaks – Replace old window putty and seals around window panes. Ensure window sashes close tightly and use spray foam insulation around frames. Install or replace weather stripping valves/sweeps at window bases.

Conclusion

Effectively sealing the many air leaks in your home may seem like an overwhelming task. But methodically addressing the major problem areas first, then moving to smaller leaks throughout the building over time, can lead to substantial energy savings. Just sealing obvious air leaks around attics, doors and windows to start with can improve the comfort of your living spaces for years to come.