How much does it cost to seal air leaks in a house?

Air sealing is the reduction of unintentional leaking of air in and out of a house through cracks and openings, so that the house is more energy efficient, durable, comfortable, and has a healthier indoor environment. Air leakage is sometimes also called air infiltration and is measured in terms of air changes per hour (ACH) or cubic feet per minute (CFM). For example, if your home has an ACH of 0.5, it means that half the air in your house is getting changed every hour.

Air sealing can help you lower your utility bills. According to the ENERGY STAR program, most people could reduce their heating and cooling costs by 20 percent by fixing air leaks. Many old homes have holes in the “building envelope” or the exterior walls, roof, and foundation. These openings may range from large, conspicuous holes to tiny, almost invisible cracks. Even small cracks can have a big impact. For example, an eighth-inch-wide, 6-foot-long crack between a door and a door jamb can be considered equivalent to a 9-square-inch opening. In winter, these leaks let the heated indoor air escape and cold air enter the house. In summer, cool air leaks out and hot air moves in. Air leaks can also cause moisture to seep into the walls and ceiling, causing structural damage to the house as well as affecting the health of the occupants.

The average air sealing project in the U.S., which covers air sealing the doors and windows of a two-story, 2,500 sq.ft. home will cost around $350 -$600.

Air leakage

Before air sealing your home, it is important to understand how air leakage occurs and how it can impact you. Infiltration is mainly caused by wind, stack effect, and mechanical equipment in the home.

Wind causes infiltration on one side of the building and exfiltration on the other side by creating a positive pressure on the windward face and a negative pressure on the leeward face, pulling air out of the building. Wind effect depends on the surrounding terrain and vegetation.

The warm air always goes up because it is less dense than cold air. So during winter, warm, indoor air leaks from upper levels of the building through cracks and other holes in the exterior walls and roof, reducing pressure at the base of the building. This forces cold, outdoor air to move in through windows, doors, and other openings. This is called stack effect. This phenomenon is reversed in summer but is not very significant because the temperature and pressure difference in summer are not as great as in winter.

Mechanical equipment such as fans, blowers ¹, and dryers cause the movement of air within a building and through enclosures, causing pressure differences. If more air is exhausted from a building than is supplied, it creates a negative pressure indoors, causing unintentional air flow into the building.

Pros and cons of air sealing

Air sealing your home has many advantages, including lowered energy consumption, lowered utility bills, and increased comfort.  

Air sealing promotes better health by reducing the chances of mold and mildew growth. Reduction in the movement of moisture inside a home will also make the home more durable. In addition, air sealing is one of the most affordable home improvement projects and gives good returns on investment. Air sealing projects may also be eligible for incentives such as tax credits and rebates as part of energy saving initiatives.

The only disadvantage of air sealing is that indoor contaminants will have no way to escape outside, especially during winter when all the doors and windows are kept closed. This will affect indoor air quality and could aggravate symptoms of flu and other illnesses.

Air leak detection

While some sources of air leakage in a home are obvious, for example, space under the entry door, there may be other less obvious gaps that have to be sealed to make your home energy efficient. A blower ¹ door test is a good method to detect air leaks. A blower door is a powerful fan that attaches and seals to a door, usually, the main door, to blow air in or out and accordingly pressurize or depressurize the home. The pressure difference between inside and outside will force air through any cracks in the building envelope. The flow rate at the specified test pressure is a measure of the leakiness of the envelope. This test can be performed by a wide range of professionals - builders, contractors, or tradesmen. However, the person should be knowledgeable and should know how to operate the equipment. Infrared imaging equipment can also be used to determine where heat is escaping and cold air is entering a building.

A basic building pressurization test can also help detect air leaks. On a cold, windy day, turn off all combustion appliances in the home and shut all windows, exit doors, and chimney flues ². Switch on all exhaust fans that blow air out such as clothes dryers, exhaust fans in the bathrooms, kitchen stove vents, and so on. Light an incense stick and take it near common air leak trouble spots. If the smoke wavers, it indicates a draft.

Energy audit

An energy audit can help you understand how much energy your home uses, where you are losing energy, and what changes you can make to make your home more energy-efficient and comfortable. The average energy audit for a one-story, 1,200 sq.ft. home costs about $150. Most energy audit packages will include a blower door test to check for air leaks and measure the tightness of a home, infrared imaging to detect loss of heat from the home, a room-by-room visual inspection of windows, doors, and appliances, and utility bill analysis.

Air sealing trouble spots

Below are some key air sealing trouble spots that can have a significant impact on your home’s tightness and energy efficiency.

• Ceiling fixtures, especially recessed lights ³
• Whole-house fan
• Air ducts
• Switches
• Air vents
• Fireplace wall
• Garage/living space wall
• Windows
• Doors
• Chimney shaft/flue
• Attic air sealing
• Attic access
• Rim joists, sill ⁴ plate, foundation, floor
• Exterior wall penetrations
• Between flooring and baseboards

Air sealing methods

Air sealing can be done using a wide range of materials and techniques. Some methods are more appropriate for specific parts of the building than others. For example, caulking ⁵ is best suited to fix air leaks in areas that do not move such as gaps around plumbing fixtures.

Labor

Air sealing can be done by a certified home improvement contractor or an air sealing contractor, who are specialized contractors who seal air leaks in homes. Your local Home Energy Rater may employ air sealing contractors or will be able to guide you to a trusted professional. Before hiring, make sure to ask whether they will measure the air leakage in your home using a blower door test before and after sealing. You should also find out if they will test the safety of combustion appliances after sealing to determine if the combustion gases are being properly vented. Before starting, you should have a certified energy rater come conduct an energy audit in your home. Many contractors employ performance-based pricing methods, where they estimate a price for a target infiltration rate. Hourly rates are usually between $50 and $200. Others may give you a quote based on the work needed, hours required, total square foot area, and cost of materials.

Air sealing vs insulating

Air sealing prevents air leakage into and out of your home by sealing all gaps, cracks, and seams. Insulation in a home offers resistance against heat flow. Both air sealing and insulation play an important role in determining how comfortable and durable your home will be. Other benefits of a well-insulated and tight home include lowered utility costs, reduced energy consumption, reduced noise from outside, lesser chances of dust and insects entering your home, improved humidity control, and lowered probability for ice dams on the roof during winter. Always remember that air sealing should be done before insulation. If you add insulation without air sealing, air will leak through the insulation.

An expert can help you determine whether you need more insulation or air sealing depending on the results of your energy audit. For example, if you have drafty rooms, it may be because of poor air sealing in your attic or the walls. If you experience uneven temperatures between rooms, you may benefit more from adding insulation and air sealing.

Air sealing and ventilation

Air sealing can make a home tight to the point that indoor contaminants such as formaldehyde, radon ⁷, and volatile organic compounds (VOCs) are trapped inside the home. This makes proper ventilation very important in an energy efficient home. Ventilation can also control moisture, which causes mold growth and structural damage.

Air sealing and moisture control

Air naturally moves from high pressure to low-pressure areas, taking the easiest path before it, which may be holes or cracks in the building. These air currents may also transfer moisture. With air movement accounting for around 98% of water vapor movement in building cavities, air sealing is very important for moisture control.

Enhancement and improvement costs

Attic insulation

The attic offers significant scope for reducing energy consumption in your home. A properly insulated attic will help you maintain the desired temperature in your home and avoid hot or cold ceilings, drafty rooms, and ice dams during winter. On an average, an attic insulation project for a two-story, 2,500 sq.ft. home will cost between $1,700 and $2,000.

Home insulation

On an average, the cost of insulating a two-story home of roughly 2,500 sq.ft. area is around $2,500. This will include the cost of insulating the attic, insulating the walls, and having an energy audit done.

Sealing ductwork

HVAC systems and ductwork should be tightly sealed to maximize energy efficiency. In a tight system, less energy will be utilized to circulate conditioned air. Leaks, holes, and poor connections in the duct system account for around 20% of air conditioning costs. Ductwork is usually sealed with aluminum duct tape, ductwork mastic, and ductwork insulation. On an average, ductwork sealing costs around $275 per project.

Additional considerations and costs

• If you are planning a DIY home air sealing project, start by testing your home for air tightness. If you find windows and doors with air leaks, apply caulk ⁵ and weatherstripping. Air leaks around plumbing, ducting, or electrical wiring through walls and ceilings can be sealed with caulk. If you find leaks in your insulation, seal them with spray foam. You can also install house flashing ⁸ if required. End drafts from outlets and switch plates by installing foam gaskets ⁹ behind them. Make sure the flue ² damper is tightly closed when you are not using the fireplace. Install pliable sealing gaskets on door bottoms and thresholds.
• Many utility companies and government agencies offer incentives and rebates for sealing air leaks in your existing home. To qualify, you will mostly have to hire a qualified contractor who is certified to conduct an air leakage test. DIY air sealing projects are usually not eligible for such incentives. Other conditions may include adherence to ENERGY STAR guidelines and achieving specified minimums.
• Air sealing projects can be done in tandem with other energy-saving home improvement measures. They are also frequently combined with home insulation.
• Older buildings built prior to the adoption of the 2012 International Energy Code may have air leaks.
• Air leakage may be responsible for up to 20% of home heating costs. In cases of new construction, every worker should pay attention to air sealing. In the ideal situation, gaskets should be placed under the bottom plates when the walls are built and all penetrations through the building envelope should be sealed for air leaks as work progresses. If air sealing was not a priority from the beginning and the contractor decides to take it up later (after framing but before insulation), it can make their work easy or very difficult, depending on the type of construction and the quality of work.

Remodeling Terms Cheat Sheet

¹ Blowers: An accessory that makes a fireplace more efficient by circulating the warm air in the fireplace to other areas of the home

² Flues: A duct or pipe through which exhaust gases from a fireplace, stove or boiler are released to the outdoors

⁵ Caulking: A chemical sealant used to fill in and seal gaps where two materials join, for example, the tub and tile, to create a watertight and airtight seal. The term "caulking" is also used to refer to the process of applying this type of sealant

⁶ Metal flashing: A thin sheet of metal used around the edges and junctions of the roofing material,such as around a chimney or vent, to prevent water from entering the structure through those joints

⁸ Flashing: Pieces of sheet metal used on roofs to cover joints, such as where the roof meets the wall, or around a chimney or skylight, to protect them and prevent water leaking through

¹⁰ Soffits: Construction material, typically composed of vinyl or aluminum, used to enclose the underside of eaves and ceilings