Where are the hidden air leaks in my home? (Air sealing)

You know your home is leaky, but where are the leaks coming from and how do you address them? So this blog is a basic overview of air sealing.  It's one of the most cost effective ways to make your home more comfortable and efficient.

Do you know what most people think that the biggest opportunities for air sealing are?  The gap below the door or the gap that they can see at the baseboard or the leaky windows that they have. That's the automatic place that people think needs to be air sealed.  Because that is what they can see.

But in reality, the most important place to air seal is, your attic.  Why you may ask? Well, for the same reasons it's important to insulate your attic.  Remember, hot air rises. In the wintertime, the heat from your home is escaping through your attic.  And in the summertime, you got all the heat radianting down from your attic and the attic can get up to 160 degrees. 

You want to create that separation between the attic space and your home.  Thus you really want to air seal is your attic floor. Now, what exactly are we air sealing?

Well, what happens is when an electrician comes in and wires up your home?  What happens is they drill all these holes in the top plates (that's the top of your walls) and often they don't air seal those holes, so you have holes between the attic and the inside of your walls. Maybe they just add up to a small kind of area, like a ping pong ball.  But then you have a plumber come in, that plumber runs some pipes. You add those holes too, and now you have something the size of a baseball.  Maybe there's a chimney and around the chimney, they didn't both air seal that area. Uh oh, so now you're looking at something the size of a volleyball.  And don't forget, you have all these canned lights installed in your home and o maybe now the gaps and cracks around all those holes and penetrations in your ceiling create something the size of a basketball.  And don't forget all your vents. Little spaces around all those spaces add up, with everything else to something the size of a hula hoop. Now, if you looked up at your ceiling and saw something the size of a hula hoop, you would definitely take action on seal that!

Now do you see?  Most people think the leakage is coming from the places they CAN see. But what's really impactful is the leakage that is coming from the areas that you CAN NOT see.  So it's these holes between the attic and the internal wall that add up quickly.

So now let's go for a thought experiment.  I want you to imagine you're cooling your home. It's hot outside, and again, that electrician comes in...and drills a hole in one of those top plates.  Insulation does not stop airflow, right?  Insulation acts as filter for air, it doesn't stop it. If you ever see insulation with dirt marks on it, you'll notice that's an area where air has been leaking through.  It's like you are wearing a sweater. Air would go right through the sweater.  Insulation works the same way. You need both the insulation and the air barrier, just like you need a wind-breaker on top of a sweater (like a snowboarding jacket or winter coat) to block that airflow from the outside.

So the electrician goes ahead and they drill those holes.  Then install an outlet and a wall. And since that air in your attic and the air in your internal wall wants to reach equilibrium (equal out), you find your internal wall space heats up.

The space starts to balance out and the internal wall cavities heat up. And that heat transfers into the framing.  And that framing radiates out into your internal space. And now it's kind of like you have your own heater in the center of your home in the middle of the summertime when you're trying to stay cool and comfortable.

What there is to do is to air seal that tiny little hole, and it now disconnects the space inside your house from your attic space. It creates a solid air barrier at the attic floor, and the air barrier will now isolate the interior home from the exterior.  You can avoid all that heat gain by air scaling.

This is an example of what a penetration before and after sealing in a top plate would look like:

He's just running wires, but air can pass right through there, even if there's insulation sitting right on the top. And here is the after: You're basically just applying a little bit of expanding foam.  You're filling up those gaps, those holes, and now you have a well sealed attic floor.  It's really in most cases the most important place to air seal.

So let's now look at a two-story home in deail.  Here is another really good example of exactly where air sealing may be benificial. Imagine you have a furnace on the first floor.   That furnace has ducting, right?  Ducts are the tubes that carry the air that you're either heating or cooling and the ducts may be running through a chase. (A chase is like an interior channel, typically behind the drywall.)  Here's an example of what that looks like: 

You have chases that carry the ducks from one floor to another, and often those chases are left open at the level of the attic floor.  So again, it's hot outside, you're trying to keep your house cool and since the insulation at the attic floor level doesn't stop airflow the heat from the attic is going to infiltrate the space and there is nothing to really slow it down.  Now those chases are filled with hot air and that that heat will just radiate into the home.  It'll create a less comfortable home. In fact, the ducting that's in the chase would not get super hot as well. 

The goal is to keep the air that is being conditioned cold, but you're losing the battle before the air even gets back into the living space.  If you whole house is hot even when you're running the air conditioning, this is probably why.

You know you're spending money on cooling, but it might not be working effectively because you don't have an effective air barrier at your attic floor. So all you do is cover those chases with a bit of drywall and foam to seal them in and next thing you know, you now have established a solid air barrier and you will have a much more comfortable and efficient home.

Here's another image of a chase:

 You can see the before and after, right? This was like a hole from above and a piece of drywall was added and air sealed around that, and then that created an effective air barrier. So air sealing is one of the most cost effective and impactful things that you can do to your home to improve home comfort.

You can see the full YouTube Video here:

And you wanna learn more about air sealing, you can download our free air sealing checklist: https://www.homeenergyacademy.com/duct-system-checklist-opt-in which will give you a step-by-step guide of what to look for to complete a high quality air sealing project!