Fight Mold By Detecting And Monitoring Vulnerable Areas In Your Home

Portable humidity sensors are the most affordable first step for finding sources of mold.

Optimal Humidity And Why it Matters

There are differing opinions on optimal indoor humidity: some sources say 30-50% while newer research indicates 40-60%.

Optimal humidity control has many benefits for all aspects of your health and more.

better respiratory health due to proper humidity levels

less mold growth affects all areas of the body

bacterial and viral transmissions are suppressed

healthier skin and hair

Lower cooling costs

Fresher food

Home Humidity Tips

To measure humidity, sensors like these are cheap and easy to place around your home.

What do I do if I’m below 30% humidity?  Typically, low humidity (below 30%) occurs in winter months when we turn on indoor heat, making skin and nasal passages dry and irritated. Humidifiers help by introducing moisture into the air.  You can place a portable humidifier in the most-used room during the day, and move it into your bedroom at night for more comfortable sleeping.

It’s more common to be over 60% humidity. Sometimes it is the outside climate coming inside through air leaks, and sometimes it’s a source of water inside the home that can be corrected to bring indoor humidity down.  Here is our Indoor Moisture Inventory which will walk you through the most common ways to reduce indoor humidity.

Here Is A Helpful Indoor Moisture Inventory

Air leaks: Insulation and weatherstripping are boring but vital to avoid  moisture problems.  Air leaks cause humidity to come into your home unless you ruthlessly find the air leaks and seal them.

Windows: Seal gaps as much as possible with a vapor barrier, window sealing tape and caulk.  Find a good indoor caulk that had low VOCs. Look for “Greenguard Gold” certification, which warrants that a product “has been tested and scientifically proven to have low chemical emissions”.

Doors: Checking for drafts around front and back doors.

Other air leaks: Outlets and lightswitches on exterior walls are very likely to have air leaks.

Cookstove ventilation:  It’s so important to have a properly-sized, working vent hood for your cooktop and microwave, for several reasons.  Cooking releases a lot of moisture into the air, which increases humidity in your home.  Also, the other gasses released, such as cooking odors and VOCs from burning gas fuel, should be vented outdoors too.  When you are venting from the house, you are actually pulling conditioned air from your home and exhausting it outside, creating a negative pressure (causing unconditioned air to leak into the house).   When it’s super-humid outside, even more humidity comes in.  With new-build construction and renovation, vent hoods with fresh-air intake can be installed that pull fresh air from the outside and are drawn right back out through the exhaust, mixing the cooking gasses with the fresh air. No negative pressure inside the house and no increased air leaks around doors and windows.  If you have an existing vent, it’s usually easy to see if vapors are being pulled through the vent, or going right past it onto your cabinets and ceiling.

Dryer ventilation: Do this test: bring your humidity monitor (yes, you really need one!) into the laundry room before drying a load of laundry, note the humidity, and then note the humidity again towards the end of the cycle or immediately after drying the load.  Did it increase more than 5%?  If so, check the vent hose for excessive lint, kinks or holes in it (sometimes they become disconnected completely!)  Rising humidity in the laundry room eventually equals rising humidity in the house.  If your vent and lint screen are clean and connected, and you still have higher humidity in your laundry room, you can at least mitigate mold growth by plugging in a Mold Guard in the room to run full-time.

Bathroom ventilation: Do you have a mold problem in your bathroom?  This is an ideal place to find mold–especially in the shower or bathtub, which can stay perpetually wet depending on the humidity and ventilation.  Full bathrooms (with showers or bathtubs) need adequate ventilation.  You can use your humidity monitor again to check humidity levels before and then 30 minutes after showering and using the exhaust fan.  They should be nearly the same: if not, let’s check some common issues:

• We should use the bathroom fan way longer than most of us do: not only during bathing, but also for 20-30 minutes afterwards!  It should always be switched on if you want to mitigate mold in your home and don’t let that moist air into the rest of your house.  After bathing and drying keep the door closed, turn the fan on and open the bathroom window for 30 minutes.  The fan will have fresh air to draw in and also exhaust all the moist air.
• Sizing: the general rule is that bathroom vents should be minimum 50 cfm (cubic feet per minute), and at least 1 cfm per square foot of bathroom space.  An 8×10’ bathroom, for example, should have an 80 cfm exhaust fan.
• Where to vent:  Bathroom vents must terminate on the outside of the house.  They may pass through ceiling or attic space, but you don’t want all that moist air ending up in the attic!  Do check that each vent goes outside and is actually working (lifting the vent flap with air expelled)

Basements: If your basement is not adequately moisture-proofed from the surrounding soil, or drained, the humidity can rise into the rest of the house and cause mold issues everywhere.  It’s best to leave a humidity sensor in this space and monitor it frequently.  Above 60% definitely needs dehumidification.  This permanent system reverses the “stack effect” in your house and forces air to exhaust from your basement, which is a great way to keep the humidity down.  The built-in humidistat causes the fan to come on automatically whenever humidity goes over a certain level.  The next option is to place a dehumidifier in the space with a moveable drain (such as into a shower or laundry drain) or ask a plumber for permanent drain options.  Use a HypoAir unit like the Air Angel in the area, and a separate HEPA filter will also help to remove mold spores.  Once you smell mustiness in the air, the mold has already started, so don’t delay on this one!  Check furnishings, walls, carpets and ceilings for signs of mold or mildew and try to determine the source of the moisture, whether it’s a specific “hole in the wall” or maybe something like lack of gutters on an upper story that causes water to pour off the roof and build up behind the wall.  If your foundation has an inadequate moisture barrier, it allows water from the soil to permeate the concrete.  There are companies that specialize in moisture-proofing your foundation or crawlspace, but be sure to get several quotes to assess a reasonable cost.

Drain Vents:  Black mold under a sink stopper is not normal! Sink, shower and toilet drains must be properly vented for several reasons.  First of all, it helps the drain operate properly because the incoming water does not have to “push” the air bubble on the other side of the p-trap to drain; it simply drains by gravity and air pressure is equalized through the vent.  This venting is accomplished naturally if building codes and/or good design are followed…but sometimes older and new construction homes have neither!  The second reason that drains need proper venting, is to allow the outside vent to relieve nasty sewer gasses instead of allowing these gasses to push on the p-trap and go back into the room, causing smells and mold.  If you have sluggish drain(s) that do not resolve despite cleaning, sewer smells and/or mold buildup in the drain, find a good plumber who knows about proper venting, so that he can evaluate your home’s vents and suggest cost-effective improvements.

Miscellaneous leaks:  If you don’t have humidity sensors in each space, here is where you can do a walkabout with a single humidity sensor to find more hidden sources of moisture.  Take a reading in your main living space, then leave the sensor in each room outside of it for a few minutes, to acclimate.  Then take a reading in the outside rooms, and do closer inspections if the humidity is appreciably higher in a certain room.  Open cabinets, check under sink drains, pull back curtains, open closet doors, check walls and carpeting behind furniture…so many drains run through the walls of our homes, and are never seen or considered til they leak!   This is where your nose, and the sensor, can tell you to look until you find the source. If possible, avoid living in that space until the leak is stopped and any mold is cleaned up.  If it’s necessary to use the room, you can add a portable dehumidifier, HypoAir product like an Air Angel, and a separate HEPA filter to make the air cleaner until the mold source is eliminated.