Well, you are not alone. According to WebMD, 30% of adults and 40% of children suffer from allergies. Americans spend 16 billion dollars a year on allergy related healthcare. It may be even worse for those of us living in Lexington; our city has been ranked by Forbes magazine as the worst city in America for seasonal allergies. Considering the average American spends 90% of their time indoors, and indoor air can be 2-5 times as dirty as outdoor air, the air quality in your home can be a major contributing factor to your allergy issues. In this article, we will first discuss why our air is so bad, and then we will go over the steps we can take to improve it so our families can breathe easy in our homes.
So how does the air in our homes get so bad? If you have known me for longer than 5 minutes, you’ve probably heard me say that a house does not need to breathe. This is one of the worst misconceptions in residential construction, and causes many problems in our homes. When a house “breathes,” it pulls air in from uncontrolled locations like your attic, or even worse, your crawlspace. This process is called uncontrolled ventilation, or infiltration for short. Air leaks into the house typically at ground level, and then makes its way out at the top of the house through the attic, as seen in this graphic.
When this air leaks in, it brings with it dust, dirt, pollen, and humidity in the summer, dry air in the winter, and even Radon gas. Then when the air leaks out, it leaves all of these bad things behind. When your house breathes, it is acting like a filter for that outside air.
So the first step in improving indoor air quality is to tighten up our homes. The tighter the home, the easier it is to control the air quality. Period! When building a new home, it has never been easier to build air-tight construction. With products like spray foam insulation, double pane windows, and exterior house wrap, you can achieve a really tight house with minimal increased cost. This will benefit not just your air quality, but also your comfort and energy bills. Tighter homes are better all the way around.
Existing homes are a little more involved in making them tight. Through years of experience, we know the areas to focus on for the greatest impact are your crawlspace or basement, and your attic. If you live in a house with a crawlspace, more than 25% of the air in your home came in through that crawlspace, bringing with it all sorts of unhealthy pollutants before it traveled through the home and exited through your attic. So the crawlspace is a good place to start.
First we have to consider what are we sealing in the home as we tighten it up. A crawlspace, for example, is a very dirty place, often containing mold, rodents (some dead some alive!), construction debris, old insulation, dead hvac and plumbing, and even Radon gas. When we seal a crawlspace properly, this process is called “crawlspace encapsulation”. The first step in any encapsulation is cleaning the crawlspace as best we can, removing all the old insulation and construction debris, and treating any microbial growth that may be mold. We then install a heavy gauge plastic sheeting sealed to the walls of the crawl to prevent moisture, odors, or even Radon gas from leaking out of the ground into the crawl. We then use closed cell spray foam insulation on all the foundation walls up into the rafters to seal off the home’s rim joist. All foundation vents and other penetrations are also sealed to make the crawlspace as tight as possible. At this point, the crawlspace is as easy to control as a basement. We often add a dehumidifier to keep moisture in the air in control. Here’s a picture of what it should look like after crawlspace encapsulation.
Unfinished basements or unfinished areas in basements are the next best places to insulate and air seal. The rim joist is where the wooden frame of the house meets the concrete foundation. Wood against concrete is never very airtight, and can account for more than 10% of your home’s air leakage. All you have to do is look at the black streaks in the pink fiberglass to see where the air is coming in. This is a good example of why we don’t use fiberglass to insulate in these areas because the air just passes right through it. The best fix here is spray foam insulation because it not only insulates, but air seals as well. During installation, the foam expands to fill in all the gaps and cracks. This not only stops air leakage, but also keeps out insects and other unwanted pests.
Once we have the lower half of the house sealed up, then we move on to the attic. I’m often asked why we skip the walls and windows. With existing homes, it’s usually not very feasible to add insulation to the walls unless the home is going through an extensive remodel. Windows are another misconception in home improvement. As long as your windows are functional and relatively tight, there is little value in replacing them. In fact, one study showed that replacement windows will never return their cost investment in their lifetime. It’s usually the last place you should spend your money.
Now back to the attic! Ventilated attics really do cause a lot of problems in our homes. Energy efficiency, drafts, and indoor air quality are all negatively impacted by ventilated attics. In the summer, a central Kentucky attic can reach temperatures of over 140 degrees. This immense heat rises out of your roof vents– or even worse– the dreaded attic fan. As the hot air vents out of the roof, it has to replace the air in the attic; in most cases it pulls air from the house. Now not only is it pulling out the conditioned air that your air-conditioner has worked hard to deliver, but even worse it puts the basement or crawlspace on a negative pressure, effectively acting like a vacuum pulling in air from all the dirty places we talked about above. I once saw an attic fan pull so much air from a house it was literally sucking Radon gas out of the ground!
So how do we fix a ventilated attic? Just like the crawlspace, the process is called “attic encapsulation”. Attic encapsulation is accomplished by insulating the roof deck (the top of the attic) with open cell expanding spray foam. All roof and gable vents are sealed and insulated. Typically, 5.5 +/- inches is recommended for our area to give the encapsulation the air sealing and insulation desired. Because we are bringing the attic into the home’s conditioned space, just like in the crawlspace, we want to clean the attic of all the old insulation and construction debris. You would be shocked at how much nastiness comes out of an attic when we vacuum out the old insulation. If your home’s heating and cooling are in the attic, this process will not only help with air quality, but it will also save dramatically on heating and cooling bills, paying for itself in just a few short years.
So now that we have tightened the home as much as is practical, what’s the next step in improving indoor air quality?
Capture and kill!
It’s a phrase we use in heating and cooling to describe our best practices in controlling air quality with HVAC equipment. Capture means having a really good air filter on your system. Throw away the old 1 inch thick filter and invest in a media filter cabinet that’s at least 4 inches thick. 1 inch filters are to protect the equipment, not your air. 4 inch pleated filters perform much better and will not harm your system’s fan like a 1 inch filter can.
Kill! We want to kill anything organic in the air stream of your HVAC system. Mold and mildew are found inside most HVAC systems we inspect. That’s why we recommend ultraviolet lights inside the ducts nearest your systems AC coil. UV light will kill most of the bad stuff and prevent anything new from coming back. UV also kills dust mites, breaks down VOCs, and weakens viruses. UV in your HVAC is the single best thing you can add to your home to improve your air quality.
If you want to get really serious about your home’s indoor air quality, then this will give you a clear path to get there. Tighten, control, capture and kill. In my next blog, I will talk about the role of the actual heating and cooling equipment, and how controlling the humidity in your home can also impact your home’s air quality.