What is Air Sealing a Home? (And Why It’s So Effective)

Even if you don’t know what exactly air sealing a home is, you have definitely experienced if a home is not air sealed. 

Do you have a drafty or uncomfortable house? Or maybe your electric bills just seem higher than they should be. Or maybe the different floors of your home have a significant temperature difference?

Homes that are not air sealed might be all of the above, and cause other issues to boot.

Air sealing a home is often overlooked by homeowners, but it can be one of the most effective ways to reduce energy bills. In this blog post, we’ll cover all you need to know about air sealing a home and why it’s so important.

What is Air Sealing a Home? 

In basic terms, air sealing a home is minimizing the opportunity for unwanted airflow within the house by identifying leakage points. This increases the energy efficiency of the home and creates a more comfortable environment to live in.

It can be located anywhere from the basement to the attic in a home and everywhere in between. Some of these points are pretty simple such as windows and doors, outlets, or baseboards where others can be hard to identify like ducts, recessed lighting, drop ceilings, attic access, fireplace walls, or garage walls. 

Air Leakage Indicators

There are a few key indicators of air leakage. The biggest one is having a significant temperature change between floors of your home. In a home, or any structure, hot air rises. A well-sealed home holds the heat into its structure, keeping the temperature consistent. 

A picture of an eave inside a master bedroom, showing a break in the drywall. This indicates lots of air leakage into the attic, which is poor for air sealing and energy efficiency for a home.
During our renovation project, we discovered a huge gap in the drywall in the master bedroom eave near the top of the ceiling. HVAC systems have a hard time keeping up if this much air is leaking into your conditioned space.

A home with air leakage will allow the air to flow through the house, creating a disparity in the temperature on different floors. This is called the stack effect, as Energy Smart Ohio describes well in more detail. A good rule of thumb is that the different floors of your home should be within three degrees of each other. If it is more than that, then there is a good possibility of air leakage. 

Another indicator of air leakage is having a draft in your home. Sometimes people think a draft is a good thing, that it keeps the air moving and fresh air filtering through the home; however, this is a misconception. A breeze through the house means there are inefficiencies and gaps in the building envelope.

Why is Air Leakage Bad? 

Air leakage causes a lot of inefficiencies in a house. Having a draft or stack effect can cause high electric bills as the air conditioner or heater must work overtime to adjust for the temperature swings.

A home is designed to work a specific way and has air filtration and air movement systems in place. When air leakage occurs, it puts added stress on those systems and makes it nearly impossible for them to work correctly. 

This results in high electric bills or even simply an uncomfortable home. Having a big temperature difference between floors of a home can be tough to manage. Sometimes the source is obvious. Perhaps a leaky window, door, or electrical outlets could be the culprit, but it can sometimes be harder to identify. 

How Do I Test for Air Leakage? 

There are a couple of options that vary in their effectiveness. Two of them can be done as a homeowner, but are not as accurate as a professional blower door test.

Visual Inspection  

A visual inspection is a great place to start to determine if air leakage may be an issue in your home. Checking around the seals of windows, doors and any appliances or pipes coming into the home will give a good indication of major air leakage points. If there are visible holes or gaps in the seal or no seal, then air leakage occurs. 

It is also essential to check outlets, wall or window-mounted air conditioners, baseboards, attic hatches, and other visible areas where air could be leaking. 

It can be harder to determine if something like or ducts is causing the air leakage. In this case, doing a building pressurization test is the next step. 

Building Pressurization Test

This is the next step in determining air leakage. In order to conduct a building pressurization test, it is ideal to choose a cooler, windy day. Then, turn off all appliances, including anything gas-burning such as a furnace. Also, turn off water heaters, exhaust fans, clothes dryers, vents, or anything else that could move air around the home. 

Then, light a candle or incense stick and walk around your house holding it close to potential leakage points, similar to what is listed above. If at any point the airflow is strong enough to make the light flicker quickly or even go out, it is an air leakage point. 

Blower Door Test

The blower door test for air leakage is fairly simple but does need to be done by a professional. This test will quantify how much air is leaking from the home and identify where the leakage is occurring. 

A picture of a black dial hooked up to a blower door test that we have mounted to our front door. The picture shows a red cover with a fan attached to it in the doorway. This is the tool you use before air sealing a home.
This blower door test hooks up to your main door opening, so that you can test the leakage in your home.

The test utilizes a blower that is temporarily installed on a door. This sucks the air out of the house at a constant rate. Doing this forces air through any leakage points, which a professional identifies during the test. 

If you’d like to learn more about blow door test benefits, check out our writeup here.

Some Simple DIY Tips for Air Sealing Your Home

Air sealing can range from simple fixes that you as a homeowner can complete to more complex tasks that would require a professional.

Some of the simple fixes include caulking around windows and doors, installing foam gaskets behind outlets, and ensuring vents are sealed or caulked. In instances where the air leakage is severe, or there are bigger gaps, a foam sealant may be necessary instead of caulk. The good news is that all these products are at your local hardware stores like Home Depot or Lowes.

For more extensive tasks such as exterior wall sealing, insulation work, attic work, or work with the ducts, it can be more effective and efficient to hire a professional. Handy individuals could potentially handle all fixes themselves; however, hiring a professional could save money on materials, equipment, and time. 

A picture of an electrical outlet with the cover plate off. It shows a foam insulation gasket cover installed on the back of the plate to help with air sealing the home for energy efficiency.
Buying some inexpensive outlet cover foam sealers to go behind your electrical outlet plates can really help stop air movement through your home.

Energy.gov also has a really great post on some additional trouble spots to check for home air sealing here.

Can a Home Be Too Tight?  

One thing to be careful of is sealing the home too much. There does still need to be some airflow through the house. Air sealing every hole in the home, including covering vents, can be dangerous. Luckily, it is pretty tough for older homes to over-seal a home even if you try to, rarely happens. 

If your home is sealed too tight, then installing a vent fan is a possibility. Additionally, suppose the house is simply designed to be too tight. In that case, mechanical ventilation may be necessary, which forces air through the home at an appropriate rate and exchanges the inside air with fresh outside air. 

How Much Does it Cost to Air-Seal a Home? 

As with many things, the cost can vary widely based on the extent of air-sealing needed and where in the home it needs to be completed. For example, air sealing on the first floor might be more easily accomplished than attic work. Additionally, installing insulation or fixing ducts is more extensive than caulking windows, doors, and vents. 

That being said, there is a good amount of cost data available. According to FIXR, The average cost to air seal a two-story, 2,500 square foot home ranges from $350 to $600. This includes materials and labor. 

Summary

Air sealing a home is essential for home efficiency and cost savings. It can also significantly increase the comfort level within the home as temperatures on different floors are more stable.

Identifying air leakage is the key to air sealing a home. Once the points are identified, air sealing can be conducted to eliminate the air leakage points. 

The air sealing process can be done by the homeowner themselves or a professional and widely depends on the severity of the air leakage. And luckily, a lot of it can be as simple as caulking small holes near windows and doors to needing work done in the ducts, utilities, or attic. 

Think of a boat with a lot of holes in the hull. The water is slowly leaking in, and you keep bailing out the water to stay afloat. This is how our systems in the house (like HVAC) are working overtime in our homes. You cannot control the air inside to keep the interior at a constant temperature if it keeps leaking out through all the holes.

And this is why air sealing and leakage testing is one of the cheapest and most effective things anyone can do at the beginning of their energy-efficient journey.

Erin Shine

Erin Shine

Founder | Attainable Home

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