Summer Humidity Explained

Summer Humidity Explained

Indoor_Humidity ExplainedIn the summer your Air Conditioner is really both cooling the air and dehumidifying it… Why is my home so humid in the summer? Do I need a new air conditioner (there are tons of offers on TV and every online ad)? Will insulation and air sealing with spray foam insulation make it easier to control the humidity? Does my steam shower/ indoor pool/ indoor greenhouse impact my humidity levels in my house? (High indoor humidity during the winter will appear in the form of condensation on windows or can lights dripping from the ceiling and in the summer, you will see humidity above 60%)

Let’s start with the facts. The average humidity level in Chicago for the whole year, over time, is 70%. December is the most humid month on average with an 82% humidity level and April being the lowest average humidity with the humidity in April averaging around 50%. In each of the cases the outdoor humidity levels outside exceed the 35% to 50% preferred indoor humidity level. If your home is drafty, leaky, and poorly sealed from the outside air, you will never be able to dehumidify your home as you are simultaneously filling the house with humidity. One easy way to know is, can you smell the airborne odors from outside your home, on the inside?

What should the humidity level in my home be during the summer? The answer is 35% to 50%, with an ideal humidity being in the 40% range.

Here are the five simple steps to solving humidity issues in most homes:

First: Keep your windows and doors closed when the humidity outside is high so that you have less moisture to pull out when the AC is running.

Second: get the humidity out of the house when it is created. Please make sure the bath fans are properly vented though the roof to the outside. Please use the fans when bathing. The simple check to see if there is a “draft” to the fan is to take a single sheet of toilet paper and place it near the grill of the fan. If the fan has a “good draft” it will be sucked against the grill. If the fan does not have a good draft, it is time to replace that fan and any that are not working or any bathroom without a good working fan. It is a common problem that bath fans don’t work (or are not used) or are vented into the attic/ soffit and do not get the humidity out of your home. When inspecting homes, it is common to see this and to see that all the roof nails are rusted, as evidence of greater humidity in your attic. High humidity in your attic can be resolved by proper venting of the bathroom/ dryer vents or correcting the roof ventilation.

Third: you need to know how your AC is running? Is it ‘short cycling” where it does not run long enough to push enough humid air over the coils? If that is the case, you may have a mechanical issue or you may have a thermostat issue. Depending on your thermostat, you have many choices how to deal with this. First, if you have an old-fashioned thermostat, the only option you have is to turn the fan on full time so that the humidity in high humidity areas of your home mixes with areas of low humidity. If you have a newer thermostat, you can modify how the AC runs. Depending on which thermostat you have, you can set it to run longer (cool more) than the setting on the thermostat so that more air passes over the coils and gets pulled out of the air in your home. If you need help with this, please call us and we can set you up with one of our preferred HVAC contractors who can help you. If you “love” your HVAC person, we are happy to help educate them on the process so you can keep your HVAC person and we can get a new referral source.

If your home is drafty, leaky, and poorly sealed from the outside air, you will never be able to dehumidify your home as you are simultaneously filling the house with humidity.

Fourth: Solutions beyond the mechanical solutions involve foaming the roof deck to stop your home air from mingling with the hot humid air outside so that when you equipment is dehumidifying and cooling your home, you are not instantly replacing the dry air with the moist/ humid air. Foam insulation at the roof deck on average reduces air leakage by 40-70%. Additionally, when you put an airtight cap on your home and significantly reduce the “stack effect” you stop the thousands of small openings in the walls of your home from having a negative impact as the small holes typically require negative pressure to pull outside air in the home. When foaming the roof with Chicago Green Insulation, we access the bath fans and how they are vented and replace or fix the issues if they are found, when doing work.

Fifth: but only with extreme caution: Add roof ventilation both high and low in your attic but only up to the square inches recommended: Roofing Magazine says that the ventilation square inch formula is: “Attic square footage ÷ 2 = square inches of EXHAUST and square inches of INTAKE Net Free Area (NFA) needed. (NFA is the unobstructed area through which air can pass through a vent, usually measured in square inches”. Adding roof or gable vents without considering the path the heat and humidity will be leaving the attic often creates cross ventilation issues reducing existing success getting heat and humidity out, even with more square inches of vents. DO NOT ADD AN ATTIC FAN UNLESS IT IS YOUR ONLY OPTION! See blog on Attic Fans for more info.

Humidity is one of the most common questions we get during the summer. If you don’t know the humidity at various parts of your home, it is easy enough to purchase good quality humidity sensors from a good quality, locally owned hardware store in your neighborhood.

(If you have a “wet basement” or “wet crawl space” those are other bulk moisture issues that do contribute but are not addressed here. Give me a call and we can talk about these, including excavation of the exterior of the foundation and installing 2-3″ closed cell foam so you get a warm and dry basement for years to come!)

If you prefer, you can request your estimate online by clicking here.

We aren’t just selling you a product we are selling our expertise and years of experience in construction and design. As Tom Decker, owner of Chicago Green Insulation is fond of saying “Comfort is only a Foam Call away!”

About the Author, Tom Decker

With ten years of experience selling spray foam insulation in Chicago, Tom Decker is THE person to call and the Chicago Green Insulation is the organization to hire when you are looking for top notch quality and performance as well as someone who can deal with the needs of code officials, home owners and general contractors. Call the others in Chicago, if you are interested in the cheapest price, call Chicago Green Insulation if you are interested in using your dollars to make Chicago a better city for all of us!

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