By Greg Stopher, Stopher Construction | In the past I’ve discussed the importance of air sealing. In this case I’m going to discuss a specific example of air sealing your home. A properly air sealed home will get you the most bang for your buck when it comes to an energy rating audit reward. I’ll get to the specific area for an example of air sealing later in the article but first let us refresh our memory on the definition and benefits of air sealing.
Our homes have an enormous amount of heated air in them. This is air that we have spent our hard earned dollars to heat. Let us say our home is 1200 square feet and we have 8 foot ceilings. That amounts to about 9600 cubic feet of heated air. The goal with air sealing is to try to keep that heated air inside our home and keep the cold air outside. The air we lose through cracks and gaps out of our homes means the replacement air coming in through the gaps and cracks needs to be heated. Air will naturally go from cold to warm or the difference between warm air and cold air creates a pressure differential.
The effects of our ventilation systems in our homes also create pressures differentials. We turn on our bathroom fan to exhaust moisture laden air from a shower, which is necessary for our health and that of our home, now we are pumping about 80 cubic feet of air out of our homes that gets replaced from air coming through the gaps and cracks that needs to be heated. Say we leave the fan on for an hour. We created a pressure differential since we pumped out 4800 cubic feet of air out of the 9600 cubic feet of air in our home, half the air in our home was replaced and heated over the last hour. Dryers and range top exhaust have the same effect or more sometimes. This ventilation is absolutely necessary. Don’t get me wrong, always run the ventilation to get rid of this moisture laden air. This is why Heat Recovery Ventilation (HRV) systems works so well in this climate because it is a balance system meaning we exhaust the same amount of air we bring in and transfer the heat to that air. HRVs are expensive but definitely worth the investment, but only if the home is sealed tight so we can control all the air. HRVs mean nothing if your losing cubic feet of air to neverland. So having a tight air barrier, most commonly called a vapor barrier, is very important in controlling the air in our homes. Your home probably has a vapor barrier in place but small gaps and cracks can add up to having a window or door open all year round. Areas where these gaps and cracks are often found include around windows, doors, light switch boxes, phone jacks, outlet boxes, lighting fixture boxes, plumbing pipes, and electrical wires.
Now let me show you a specific example of air leakage and how one gap adds up to a lot of airflow and other dangers.
The Example
We bought our home in June and my wife decided it was time to update the 70’s light fixtures. She has been ordering a couple of new ones every couple of months. Every time I replaced a fixture I would seal the box the wires were in, you know the usually round box that holds the wires. This sealing is part of the air sealing process to eliminate that lost air. I will seal around the wire coming into the box and I would seal around the box with caulking or foil tape depending on the size of the opening. I replaced the fixture in the dining room and thought it would be nice to replace the switch to the light with a dimmer style switch. I pulled the plate cover off and pulled the old switch off and proceeded to seal the electrical box. The box is on a common wall between the garage and dining room with a door directly to its right. Our garage is somewhat heated since we have a hydronic baseboard to keep our mechanicals and washer and dryer from freezing.
While replacing the switch with a dimmer switch I sealed the box but I felt a cold draft on my hand. Where was this coming from? I had just sealed the electrical box. I moved my hand about four inches to the right and could feel cool air pouring into the dining room from behind the trim around the door leading to the garage. I pulled the trim from around the door on the garage side, like you would do if you were air sealing around exterior doors or windows. I found an average of a ⅝ inch gap between the door jamb and the framing. Some places around the door the gap was 3/4 of an inch. I calculated that that gap equates to a hole in the wall between the garage and the home, to about 121 sq inches or close to the equivalent of having a 2 foot wide window open about 5 inches. There is a lot of air that can pass through a hole that size, especially if there is a pressure differential between the garage and the house. Our garage is insulated well but is always 10 or 20 degrees cooler. Now we have our pressure differential with the different temperatures between house and garage. Another way we could get a pressure difference between the garage and house is that the dryer is out in the garage. Now the dryer pulls a lot of air and exhausts it to the outside (or at least it should or I have other problems). The garage is not that tight so its probably not pulling a lot of air from the house, it is probably getting its air from around the garage door or somewhere easy. Now say the dryer is off in the garage and I turn on the ventilation fans in my home, my daughter is in the shower and I’m cooking. Well, I’m probably not cooking but the range top vent is moving air in the kitchen 10 feet from the garage door and the bathroom vent is moving air, now I have a pressure difference between the house and the garage, especially when you add the temperature difference between the house and the garage. Cold air is definitely moving from the garage to the house, I couldn’t measure the amount of air without some cool gadgets, but I could certainly feel it on my hand next the door trim.
The Scary Part
So I have cool air coming into my house through a gap around the door in my dining room that leads to the garage. Do you want the hear the really scary thing about this type of air leakage? Okay, I’ll tell you anyway. I don’t park a car in the garage, but if I did, the carbon monoxide from the exhaust would be coming directly into my house. Even if you drive the car in, shut it off, then close the garage door, studies have shown a huge spike in carbon monoxide levels in the home. A little bit of carbon monoxide won’t kill you but the long term effects of exposure to low levels of carbon monoxide aren’t good for you. I don’t store any hazardous materials in the garage but I sometime have a gas can or some oil in the garage for a few days.
The other scary monster in the garage is the boiler, a carbon monoxide producing, fuel fired, combustion chamber that heats water to heat my home. What if that fuel fired combustion chamber backdrafts a little bit of exhaust into the garage. Well the exhaust ends up in my house. About a month back we ran out of fuel and I knew right away when the boiler didn’t fire up but there was a strong smell of diesel in the house. Not good.
Back to the Example
So with the trim off the garage side of the door, I used a spray foam to seal the gap and then I re-installed the trim. I just sealed a 121 sq inch hole between my garage and house with very little time and effort and we all feel a little healthier already.
Small gaps and cracks really can add up throughout a home. The example above is just on a single door and it resulted in almost a square foot opening to the outside. When you add up an entire house full of windows, doors, outlet boxes, electrical switch boxes, and other areas it could easily add up to having one window open, possibly two windows open, or a door or two. Thats a lot of heat loss or cold air infiltration in the cold winter months. Like my Dad would always say when I left the door open, “Close the door! Were you born in a barn?”
Greg Stopher has over 16 years of experience in the construction field and earned a degree in Construction Technologies from the University of Alaska – Southeast. His company, Stopher Construction, LLC, is a general contracting company specializing in remodeling, custom finishes, additions and new home construction projects. He can be reached at 907-321-2350.
