Just think about all that wonderful outdoor air creating an airstream moving from the bottom of your house up to the attic.
Doesn't all that air movement seem like a good idea, bringing fresh air into your home?
During the winter, it's not. Honestly, you don't want that kind of air movement in your home any time of year. It leads to high energy bills because you can't regulate the temperature of your home and an uncomfortable home to boot, not to mention all of the allergens and outside pollutants it will bring in.
This kind of air movement from the bottom of your home that travels to the top is called a stack effect. Warm air leaks out near the top of your home, causing outside air to leak into the lowest part of your home, according to My Home Science.
Since 2002, RetroFoam of Michigan has been working with homeowners to create the air seal they need to keep that outside air from making its way inside.
In our continued efforts to educate homeowners, let's look at how the stack effect happens and what you can do to fix it.
The stack effect definition is essentially air movement that can negatively impact your home's monthly energy bills and comfort level.
The air comes in through your crawl space or basement, moves up through your floors and walls, and finally makes its way to your attic and out. This is cold air in the winter and hot air in the summer that puts extra strain on your AC unit and furnace.
Another thing to consider is that the air coming in increases the air pressure inside your home. That air pressure is looking for any way to escape, and it's taking your conditioned air out with it.
The problem with the stack effect is the taller your house is, the more of an issue you will have.
As that air pressure builds up, the faster the air moves before it hits your attic insulation. Your traditional insulation, like blown-in fiberglass and cellulose, will get pushed to either side of the attic.
If you don't have any attic insulation, you are losing much more air.
With inadequate or no insulation in your attic, you likely already had air seeping in through cracks and crevices and moisture. Now you have air coming in from different directions just from the roof and even more air from inside the house.
You have a ton of air movement in the attic, which will increase moisture problems leading to mold and mildew growth, as well as damage any insulation you have up there. The only insulation that won't get damaged in this scenario is one that is fixed into place and creates an air seal, like spray foam.
The simplest way to fix the stack effect is by creating an air seal.
You will want to stop that air from ever finding its way into your home.
From your foundation, where the air comes in, all the way to the top, where it goes out through the roof. You want your entire living space to have an air seal around it, which can be created with foam insulation. That is what we like to call the building envelope.
You have to remember that if you decide to just air seal your walls, that will increase the stack effect. When creating an air seal in this instance, the best fix is to air seal the entire home.
If you have a crawl space that is air sealed, you don't get that air coming in from the bottom, which is the most significant source when it comes to the stack effect. When you air seal your exterior walls, they are also sealed around the windows and outlets, stopping the air from getting inside. Finally, if you block the air from getting into and leaking from your attic, you seal your home's envelope.
This air seal will make your home more comfortable and energy efficient, which means lower monthly energy bills.
You now understand the stack effect and how it impacts your home's comfort and energy efficiency.
Did you know other factors related to your home's insulation could make it less comfortable while costing you money? Check out our 18 Signs and Symptoms checklist to see if it's time for an insulation upgrade.
What is a Building Envelope? (Definition/Importance)
What is Air Sealing a Home? (Definition/Importance/Methods)
R-Value vs. Air Seal: What is More Important When Buying New Insulation?