Seal Tight, Ventilate Right (Part 1)
What if I told you could save 5-20% of your heating and cooling bills, improve your indoor air quality, comfort, moisture control, durability, and value of your home all by preforming one single upgrade for less than $800? You probably wouldn’t believe me, but such a single upgrade does exist. It’s call “air infiltration reduction”, or in layman’s terms, “air sealing”. I have probably done over 150 energy evaluations in the midtown area and I can’t think of a single house where air sealing was not recommended. During the period most midtown homes were built, air sealing simply wasn’t even on the radar.
The air leakiness of a house can be quantified by a door blower test, where a calibrated fan is installed into an exterior doorway and the house is depressurized. For new homes (per code), the air leakiness should be less than 7 ACH (air exchanges per hour). This means that if the house was depressurized for an hour, all the air in the house would be exchanged with new, outdoor air seven times. From my experience, most midtown homes have a range between 6-15 ACH with some in the 20s.
For midtown homes, most air leaks occur in the basement, attic, wall penetrations (pipes, electrical outlets, etc.), and around window and door frames. In the basement, the rim joists is usually the largest source of air leakage. In the attic, air leakage comes from the attic hatch itself, recessed lights, vents, soffits, and top plates on exterior walls. A more detailed list is available on our website, www.transductiontechnologies.com.
There is nothing complicated about air sealing. Most home owners themselves can perform this task without hiring a contractor. However, from my experience, qualified contractors do a far superior job than homeowners. Find a contractor who has been trained and certified by the Building Performance Institute (BPI, www.bpi.org), Air Barrier Association of America (www.airbarrier.org), or Dept. of Energy Weatherization Assistance Program (WAP) certification.
Before you grab your caulk gun, there are some things you should consider. Your house is a system and every component in it works together. Sealing air leaks can improve the home’s energy efficiency and living quality. However, tightening the home can cause pressure imbalances, which can lead to a high negative pressure in the basement. This can set up the conditions for backdrafting of fireplaces, furnaces, or hot water heaters. After air sealing, I strongly recommend a second door blower test be performed to ensure these conditions will not occur.
Can a house be too tight? The physical structure itself cannot be too tight. The old paradigm “a house needs to breathe” is not true. However, people living inside the house do need to breathe, and so do these combustion appliances! Even though you want your house as tight as possible, you want adequate ventilation to provide acceptable indoor air quality to the residence. How much air ventilation is enough? Well, that’s the topic of the next column. Seal tight, and ventilate right!
The air leakiness of a house can be quantified by a door blower test, where a calibrated fan is installed into an exterior doorway and the house is depressurized. For new homes (per code), the air leakiness should be less than 7 ACH (air exchanges per hour). This means that if the house was depressurized for an hour, all the air in the house would be exchanged with new, outdoor air seven times. From my experience, most midtown homes have a range between 6-15 ACH with some in the 20s.
For midtown homes, most air leaks occur in the basement, attic, wall penetrations (pipes, electrical outlets, etc.), and around window and door frames. In the basement, the rim joists is usually the largest source of air leakage. In the attic, air leakage comes from the attic hatch itself, recessed lights, vents, soffits, and top plates on exterior walls. A more detailed list is available on our website, www.transductiontechnologies.com.
There is nothing complicated about air sealing. Most home owners themselves can perform this task without hiring a contractor. However, from my experience, qualified contractors do a far superior job than homeowners. Find a contractor who has been trained and certified by the Building Performance Institute (BPI, www.bpi.org), Air Barrier Association of America (www.airbarrier.org), or Dept. of Energy Weatherization Assistance Program (WAP) certification.
Before you grab your caulk gun, there are some things you should consider. Your house is a system and every component in it works together. Sealing air leaks can improve the home’s energy efficiency and living quality. However, tightening the home can cause pressure imbalances, which can lead to a high negative pressure in the basement. This can set up the conditions for backdrafting of fireplaces, furnaces, or hot water heaters. After air sealing, I strongly recommend a second door blower test be performed to ensure these conditions will not occur.
Can a house be too tight? The physical structure itself cannot be too tight. The old paradigm “a house needs to breathe” is not true. However, people living inside the house do need to breathe, and so do these combustion appliances! Even though you want your house as tight as possible, you want adequate ventilation to provide acceptable indoor air quality to the residence. How much air ventilation is enough? Well, that’s the topic of the next column. Seal tight, and ventilate right!