Air Sealing: the Why and the How

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No matter how much you love the great outdoors, you don’t want the outside in your home. Whether you are building a new house or remodeling your current one, you want your home to be cozy in the winter and cool in the summer. This means you’ll need to do some air sealing to keep the outside air out–where it belongs–and the heated or cooled air inside where you can enjoy it.

Air sealing is the process of sealing holes, cracks, and openings in your home where air can flow in and out. While you don’t want a 100% airtight home (because some circulation is important for health reasons), you definitely want to block up airflow where you can. Not only does this provide you with more comfortable temperatures inside your home, but it also makes your home more energy-efficient, helping the environment and saving you money.

House Wrap

One of the most important ways to seal your home takes place during construction. When your home or addition is being built, your contractors will use house wrap before installing siding to the outside of the house. This thin membrane will act as a moisture barrier to your home, keeping wet weather from getting into your walls. It helps prevent expensive damage to your home and it protects you from health hazards associated with mold and mildew. House wrap also makes your home more energy efficient by keeping the inside air at a more consistent temperature.

While most house wrap is installed by cutting it to size and nailing and taping it to the outside of your structure, one type called Henry Blueskin VP 100 actually adheres directly to the sheathing. Click here to read more about Henry Blueskin and why we recommend it. 

Liquid Flashing

Another important tool in your air sealing toolkit is liquid flashing. When installing or replacing windows, your contractor will use flashing around the window sills to keep moisture, wind, or water from getting in between the window frame and the walls of the house. Sometimes, this flashing is a thin, flexible material that goes around the window frame. 

Liquid flashing is another great option. It’s basically a very thick fiber-reinforced caulk-like substance that can be applied to the opening where the window will go. It is then smoothed and spread with a plastic trowel. It can get into small cracks and difficult openings where it’s hard to make traditional flashing fit properly. Liquid flashing is especially great for recessed windows, which are becoming more popular and which have the potential to leak if not installed correctly.


Insulation is probably the most well-known air-sealing resource. There are many different types of insulation, and each one is best for a specific situation. All insulation is rated with what’s called an R-value. The higher the R-value, the more the material resists the flow of heat. A few of the most common types of insulation are

  • blanket (batt) insulation. This popular insulation comes in rolls or batts and is used between boards in the frame of walls, floors, and ceilings. Blanket insulation has an insulation value of R-11 to R-38. It’s inexpensive and easy to install.

  • Foam board insulation. Foam boards are relatively thin for the high R-value they give. They are often used in attic rafters although they can also be used on interior walls if board panels or other building material is installed overtop. 

  • Liquid insulation. This material can be poured under floors or injected into walls where it hardens. It’s a good option for adding insulation to existing walls without having to remove drywall, and it also works well for oddly-shaped spaces.

  • Spray foam. This common insulation can be used by homeowners to seal up small openings and holes, or by professionals to insulate large areas.

  • Loose or blown-in insulation. Often used in attics, loose insulation is often created from recycled materials and so is a good “green” option. It settles over time, which can lower its R-value.

  • Radiant barriers and reflective insulation. These types of insulation work a little differently. Rather than blocking heat, they reflect it back by means of a shiny material that covers more traditional insulation. It’s a good choice for attics in hot climates.

How to Find Common Air Leaks

When you’re looking to seal up your house, there are a few key areas to check, places where air often leaks out, raising your heating and cooling costs. It’s a good idea to pay attention to your attic specifically. Many times, air moves from your conditioned spaces to your attic through

  • the bathroom fans

  • recessed lighting

  • the attic hatch


Conversely, there are also areas where air often gets in from the outside. This can cause temperature dysregulation and introduce pollen, dust, and moisture to your home from the outside. Check the following areas for drafts:

  • electrical outlets

  • dryer vents

  • windows and doors

  • the crawl space

How to Fix Common Air Leaks

If you’ve found some areas you suspect of air leakages, you will want to apply the proper air barrier. According to, these barriers can help you save 30% of your home’s heating and cooling costs. To take a whole-home approach, consider moisture control, insulation, and ventilation. Try the following options for common problems:

  • In the attic, pay attention to areas around the chimney, soffits, and hatch. Seal with the appropriate insulation: spray foam, blown-in insulation, or caulk (especially around soffits).

  • Caulk around the trim on windows and doors, or install weather stripping (which can save as much as 20% of energy costs when properly installed!).

  • Use spray foam in areas where pipes exit the house, such as outdoor spigots. If the pipes tend to get sweaty, use caulk instead.

  • Seal areas around exhaust fans with metallic tape or spray foam.

Home Energy Audit

If you don’t know where to start or you want a comprehensive study of your home and the air leakages you have, consider a home energy audit. A home energy professional will assess your home, perform various tests, and tell you where you should focus your efforts. Click here for more information about what a home energy audit is and if you need one. 

We Can Help!

It can be confusing knowing what type of insulation or barrier you need to apply to your home and how best to do it. If you’re planning to build a home or addition or complete a renovation in DC, Maryland, or Virginia, let us help you make your home energy efficient, safe, and comfortable. Contact us today and let’s talk about your desires and plans for your home.

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