How to Air-Seal Your Home

Air sealing your home is one of the most cost-effective ways to improve energy efficiency, comfort and indoor air quality. Properly air sealing your home can help stop drafts, moisture and pollutants from entering while reducing energy costs. This comprehensive guide will provide tips on finding and sealing air leaks throughout your home.

What is Air Sealing?

Air sealing means finding and sealing all the cracks, gaps and penetrations in your home’s envelope that allow unconditioned air to flow in and out. This envelope includes exterior walls, floors, ceilings, windows, doors and any location where there is a separation between conditioned and unconditioned space.

When warm, conditioned air escapes through leaks, it must be replaced by unconditioned outside air. This requires your HVAC system to work harder to heat or cool this replacement air. Likewise, unconditioned outside air entering through leaks must be heated or cooled. This wasted energy leads to higher utility bills.

Beyond energy loss, air leaks can cause moisture issues and allow pollutants like dust and pollen into your home. A tightly sealed home improves comfort, energy efficiency, durability and indoor air quality.

Why Air Seal Your Home?

There are several key reasons you should make air sealing a top priority:

Reduce Energy Waste

Air leaks can account for 25-40% of heating and cooling energy use. Sealing these leaks is often the most cost-effective way to improve efficiency and comfort. Proper air sealing can reduce wasted energy from leaks by up to 30%.

Improve Comfort

Drafts from air leaks make your home feel drafty and cold. Stopping these leaks helps maintain consistent temperatures and reduces humidity.

Enhance Durability

Uncontrolled air flow can transport moisture into building cavities, leading to mold, rot, pests and structural issues. Air sealing protects your biggest investment, your home.

Better Indoor Air Quality

Uncontrolled leakage allows outdoor pollutants like pollen, dust and vehicle exhaust into your home. Reducing leakage improves indoor air quality.

Added Income

For rental properties, air sealing can lead to higher occupancy rates and rental incomes. Tenants appreciate comfort and affordable energy bills.

Increase Home Value

Energy efficiency adds value to your home at time of sale. Air sealing to reduce waste is an attractive selling point.

Fight Climate Change

Sealing air leaks and reducing energy waste helps minimize your carbon footprint. Your actions reduce demand for fossil fuel power generation.

How Your Home Leaks Air

Before sealing air leaks, you need to understand the common places uncontrolled airflow occurs. Here are key areas to inspect:

Windows and Doors

This includes any penetrations like Dryer Vents, Mail Slots, Pet Doors etc. Older windows and doors often have significant gaps and leaks. Even new windows and doors may not be properly sealed during installation.

Electrical, Plumbing and Duct Penetrations

Holes made for electrical, plumbing, exhaust fans, ductwork etc. allow airflow if not properly sealed. Utilities like phone, electrical and cable also make holes that leak.

Attic Bypasses

Gaps between ceiling framing, recessed lights, bathroom fans allow attic air to enter living spaces. Kneewalls, skylights and chimneys also leak.

Basement Rim Joists

The wood framing between foundation walls and first floors leak significantly. Ducts, plumbing and wiring penetrations here are also common.

Sill Plates and Band Joists

The wood framing below exterior walls allow airflow between sill plates and band joists. Bottom plates also leak where subfloors meet exterior walls.

Crawl Spaces and Basements

Cracks and open joints between basement or crawlspace walls and floors above allow significant airflow. Dirt floors in crawlspaces are especially leaky.

Recessed Lighting and Bath Fans

Insulation clearance requirements around recessed lighting, bath fans and chimneys create airflow. Cracks or gaps in fixture housings leak too.

Fireplaces

The flues and chimneys of fireplaces create major drafts if not properly sealed. Air leaks through the hearth area as well.

Wall Penetrations

Outlets, switches, behind tubs and showers, bottom plates, drywall cracks/joints, splits in sheathing and other penetrations leak.

Unconditioned Spaces

Garages, porches, knee walls and bonus rooms over garages connect to your home’s envelope. Sealing these helps.

Anywhere pipes, wires, cables or ducts penetrate a wall, floor, ceiling or joint between building components is a potential leak source. Even small cracks and holes add up to major energy waste.

How to Find Air Leaks

Finding leakage points is crucial before sealing them. Here are tips to locate leaks:

Conduct a Visual Inspection

Walk around inside and outside your home looking for potential leakage areas. Use the checklist above to look in common problem areas. Look for gaps, cracks, holes and penetrations that connect indoor conditioned space to unconditioned spaces like attics, garages or outside. Even small gaps add up to major leakage.

Listen and Feel for Drafts

On windy days, carefully move your hand or a lit incense stick around windows, doors, electrical outlets and other areas. Locate drafts or airflow by feeling or watching the smoke drift. Listen near potential leak sites for whistling or rushing air sounds. Focus on concealed areas like chimneys, ducts, attic bypasses or basement rim joists where airflow can’t be seen.

Infrared Camera

An infrared or thermal imaging camera makes air leaks easy to find. These cameras display surface temperatures, so the cool or warm air moving through leaks is visible. Rental cameras, energy auditors and insulation contractors can all perform infrared camera leak detection. DIY models plug into your smartphone too. Infrared cameras simplify finding hidden airflow from areas like wall cavities or recessed lights.

Pressure Test

For a thorough and quantitative test, hire an energy auditor to complete a blower door test. A blower door system mounts in an exterior doorway and uses a fan to lower interior air pressure. The higher outdoor pressure flows in through unsealed cracks, openings and penetrations. The energy auditor can measure leakage rates, recommend sealing priorities and may use smoke puffers or infrared cameras to pinpoint exact leak locations.

Smart Leak Detectors

New smart home devices can now detect air leaks. The TROBO whole home air leak detection system uses advanced sensors to continuously monitor your home for leakage. It provides real-time data on leak locations and severity.

Top Air Sealing Priorities

After finding leaks, focus first on the largest and most impactful leakage areas:

Attics

Attics account for 15-25% of conditioned air loss in a typical home. Look for bypasses at eave areas, wiring, plumbing, chimneys, ducts, whole house fans, furnace flues and any ceiling penetrations. Kneewalls, skylights and recessed lighting also leak. Sealing attics usually provides the biggest return on investment.

Basements and Crawlspaces

Unsealed sill plates, rim joists, plumbing, ducts, wiring and open sump pits cause major leakage here. In crawlspaces, bare earth floors allow extensive airflow too. Sealing basement rim joists and crawlspaces are also high priority.

Windows and Doors

Check window frames, sashes and muntins along with door frames and thresholds for any gaps or cracks. Weatherstrip as needed and/or apply caulk for small gaps. Upgrade to modern energy efficient doors and windows if necessary.

Ductwork

Inspect duct boots, plenum connections and all joints for leakage. Use mastic sealant or metal foil tape to seal ductwork. Insulate any exposed ducts to prevent condensation too. Prioritize sealing ducts located in attics, garages, basements and crawlspaces.

Fireplaces

Seal any gaps around fireplace inserts and their chimneys. Make sure flue dampers close tightly when not in use. Keep glass doors or an inflatable chimney balloon in place to minimize drafts when not using the fireplace.

How to Perform Air Sealing

Once you’ve identified key leak points, here are tips on materials and methods to seal them:

Use Appropriate Materials

• Caulk – Use paintable silicone or polyurethane caulk for small gaps up to 1/4″. Apply to clean, dry areas. Consider acoustical caulk to further reduce noise transfer.
• Foam Sealant – Two-part polyurethane foam or one-part foam sealant in cans expands to fill gaps up to 3″. Foam is very effective but messy for large gaps. Use minimally expanding foam for windows and doors.
• Weatherstripping – Adhesive-backed foam or vinyl strips seal gaps around windows and doors. Choose compression seals for best results. Make sure weatherstripping fits tightly without binding the door or window when opened.
• Spray Foam – Professional spray foam insulation contractors can quickly seal large, difficult to reach areas like rim joists. Foam conforms to any shape and insulates. Different foams are available for various applications.
• Drywall – Seal larger gaps and holes with drywall patches. Use acrylic caulk at seams and penetrations. Apply mesh drywall tape embedded in joint compound for durable results.

Prep the Area

• Clean surfaces so sealants adhere properly. Remove any dust, oil or debris. Lightly sand glossy areas. Wipe down with rubbing alcohol for best adhesion.
• Wear protective eyewear, gloves, clothing and respirators when appropriate. Follow all safety precautions when working with sealants or spray foam.
• Review manufacturer instructions for proper application temperature range, drying times, expansion rates and other factors. Do not seal over damp surfaces or when freezing temperatures are expected.

Apply Caulk

• Cut nozzle at 45 degree angle to desired bead width. Hold at consistent angle as you apply.
• Seal gaps with steady pressure, no gaps or air pockets in the bead. Smooth with fingertip or caulk tool.
• Make sure caulk adheres to both sides of the crack or gap. Dig out old caulk if needed.
• Clean up excess with a damp rag immediately. Do not “overwork” the caulk bead. Allow to fully cure based on manufacturer directions before painting.

Use Expanding Foam

• Insert foam nozzle into gap, filling about 50% full to allow for expansion room. Do not spray foam outside.
• Hold can upside down to avoid any air pockets. Shake can vigorously first.
• Layer additional foam once cured if needed for deep gaps. Cut away excess foam with a serrated knife once dry.

Install Weatherstripping

• Carefully measure width to cut weatherstrip to length. Allow extra length for compression. Use mitered corners for angled runs.
• Thoroughly clean attachment surfaces. Remove old caulk and any peeling strips. Ensure surface is smooth.
• Apply steady pressure while attaching. Make sure adhesive makes full contact and weatherstrip compresses when door or window is closed without binding.
• Use thicker material for wider gaps. Look for products with finned, bulb or w-shaped strips for best sealing.

Hire a Professional

Some air sealing jobs like spray foaming rim joists, repairing extensive drywall damage or duct sealing may require hiring a qualified contractor. Ask for references and examples of previous air sealing work. Get multiple bids to compare.

Air Seal These Key Areas

Focus on these major leakage areas and techniques for sealing them:

Attics

• Seal any gaps along ceiling and wall junctions with caulk or spray foam. Pay special attention around chimneys, ducts, plumbing vents and electrical penetrations.
• Install baffles to keep insulation from blocking eave vents. Use rigid foam board to insulate and air seal attic access hatches and knee wall doors.
• Seal plumbing stack and electrical wire penetrations through the attic floor with caulk or spray foam.
• Weatherstrip and insulation attic pull-down stairs on all four sides. Make sure stair cover fits tightly against frame when closed.
• Use duct mastic or foil tape to seal all attic duct joints and connections.

Kitchens and Baths

• Seal around sinks, tubs, showers, faucets, drains, water shutoffs and electrical outlets with caulk.
• Use silicone caulk rated for bathrooms. Remove old caulk and ensure surfaces are clean and dry before applying new caulk.
• Seal gaps around exhaust fan housings. Make sure dampers close fully when fans are off.
• Apply escutcheon plates around pipes and gaps where they penetrate walls. Foam seal larger plumbing penetrations.

Basements and Crawlspaces

• Inspect sill plates, rim joists and band joists for any cracks or gaps. Seal with appropriate caulk, foam or rigid insulation. Spray foam works well for rim joists.
• Seal penetrations for ducts, electrical, plumbing, cables etc. through sill plates or foundation walls. Use caulk, foam, rigid insulation or drywall.
• Cover exposed dirt crawlspace floors with vapor barrier sheeting, overlapping seams at least 12 inches. Weigh down and seal all edges.
• Seal the crawlspace access door or hatch insulation with weatherstripping, latch and adhesive foam panels. Make sure door fits tightly when closed.

Windows and Doors

• Apply caulk around inside window and door frames where they meet drywall. Use low expansion foam for larger gaps up to 3/4 inch. Do not restrict window operation.
• Seal thresholds with caulk if gaps exist between threshold and subfloor. Shim loose thresholds before caulking.
• Check window sashes when locked for any sliding gaps at corners. Apply weatherstrip tabs if needed to compress against frames when closed.
• Install quality weatherstripping around entire door perimeter – head, jambs and threshold. Choose thicker compressible seal types like V-strip, spring bronze or dual durometer. Replace worn out weatherstripping.
• Make sure exterior window and door trim fits tightly against siding. Seal any cracks or gaps with caulk. Ensure proper flashing exists above trim.
• For doors not exposed to weather, install door sweeps at bottoms and apply adhesive foam strips or silicone gaskets around frames to seal gaps.

Electrical and HVAC

• Seal air leaks around electrical boxes and conduits where they penetrate walls with foam or caulk. Ensure insulation surrounds boxes without blocking ventilation holes.
• Apply fire-rated caulk or foam around duct boots, plenums, pipes and other penetrations into unconditioned areas like attics and garages. Seal all ductwork joints.
• Look for leaks around furnace flues, combustion air pipes, exhaust ducts and intake vents. Seal with appropriate heat and fire resistant caulk or use metal flashing.
• Caulk gaps around HVAC wall control panels or thermostats, especially where low-voltage wiring penetrates the wall.

Fireplaces

• Ensure fireplace dampers seal tightly when closed. Replace worn out rope gaskets as needed. Keep dampers closed when not using the fireplace.
• For gas fireplaces, examine vent pipes and collars for any disconnections or gaps. Apply fire-rated caulk or tape if needed.
• Install fireplace doors over the firebox opening when not in use to reduce air leakage up the chimney. Use an inflatable chimney balloon for added effectiveness when fireplace is inactive.
• Seal gaps between the fireplace facade and framing with fire-rated caulk. Cover large gaps with non-combustible materials like cement board or sheet metal.

General Holes and Penetrations

For any miscellaneous holes, gaps and penetrations:

• Use acrylic latex caulk for small cracks in drywall, baseboards or decorative trimwork. Carefully clean area first and tool caulk bead for best appearance.
• Plug larger drywall holes with drywall plugs or inserts before applying caulk or drywall compound. Use mesh tape for durability on seams between patches and existing drywall.
• For small gaps around pipes, cables, ducts etc., apply appropriately sized escutcheon plates or use foam sealant.
• Use spray foam for larger penetrations through walls, floors or ceilings. Apply carefully to avoid excessive expansion.
• Cover unused chimneys and vents with caps or covers sealed with caulk. Ensure caps do not restrict proper venting for others like furnaces or water heaters.

Tips for DIY Air Sealing Success

Here are some handy tips to ensure your DIY air sealing project goes smoothly:

• Buy a variety of sealants and materials so you have the right product for each application. Read all labels carefully first.
• Wear protective equipment like gloves, goggles, masks and coveralls appropriate for the sealants used. Work in well-ventilated areas.
• Do a complete walkthrough and make a list of all potential leakage sites before starting. This will help you estimate the time required and ensure you have all needed materials.
• Start sealing in hard to access spots like attics, basements and crawlspaces first before moving to easier living areas.
• Turn off any appliances orpilotsbefore using combustible sealants like spray foams near water heaters, furnaces or fireplaces. Check for any manufacturer restrictions.
• Follow the manufacturer’s recommended application temperature range. Avoid sealing in very hot or very cold conditions or before rain or freezing temperatures.
• Allow appropriate curing times based on the product. Do not disturb, reopen or paint over flexible sealants before they fully set.
• Make sure surfaces are clean and dry before applying any adhesives or caulks. Remove any loose materials or old caulk first.
• Get help accessing or sealing difficult areas like ducts or upper exterior walls. Use extension tools if reaching the area safely alone is uncertain.
• Hire contractors for jobs requiring extensive drywall work, spray foam insulation, major duct overhaul or anything requiring deep expertise.
• Take pictures before and after sealing for comparison. This