The Magic of Air Sealing a House

Air sealing a house is one of the most important home improvement measures a homeowner can take to increase energy efficiency as well as comfort around the entire home.  In fact, by air sealing your house you can legitimately add years of service to your HVAC machine (because it won't have to work as hard) and you can eliminate paying for projects that won't fix your issues unless air sealing is complete. Air sealing a house is definitely a place a Maryland homeowner should start if they are serious about having a comfortable home.

The best air leakage points to seal are at the top and bottom of your house.  Typical air leak points include light fixtures, walls/floors, ducts, fireplace openings, plumbing penetrations and light fixtures.  Basement air leakage should also be considered equally important to attic air sealing. These air leakage points are in the areas of the home where pressure is greatest causing the holes to do the most “damage”.

Positive Pressure (Exfiltration Through the Ceiling)
Pressure is the greatest at the bottom and top of a house due to the stack effect.  Much like a chimney, the upper floor of the home is where the warm air rises and if allowed, the conditioned air will escape through the holes, cracks and crevices unless they are sealed.  This is known as positive pressure.
 

             
A positive flow of warm air into the attic creates a pull of cold air at the basement.
 

Negative Pressure (Infiltration from Basement)
When the warm air is flowing into the attic uninterrupted, the basement acts like the base of the fireplace and draws fresh, cold air in from the outside.  This is known as negative pressure.
 

Air Sealing Materials
Each area of the home that has a need for air sealing might require a different technique.  Air sealing materials consist of the following:

• Caulk
• Foam
• Sheathing Tape
• Sheet Metal
• 1/2" Polyiso/XPS
• 3/4" Plywood
• 1/2" Drywall
   

Professional Assessment
Having your home evaluated by a Building Analyst (BA) is a great way to identify air leakage in your home and find the right solutions to fix the issues.  A Building Analyst is a certified professional with good overall residential building experience.  A certified BA is able to evaluate uncontrolled air leakage into and out of a home and identify heating and cooling problems that lead to high bills and uncomfortable living spaces.  A comprehensive whole-house assessment can determine the root cause of problems and make recommendations, assess ventilation, air flow and overall health and safety.