If you’re searching for signs of excess humidity in the home, first take a look out the window. One of the most visible red flags of surplus water vapor in the air is condensation forming on the inside of window panes. Other locations in the house may be equally vulnerable to damage from overly humid conditions, but few are as conspicuous as the sight of persistent fog, water droplets and runny streaks on your glass, obscuring your crystal clear view of the outdoors. It’s important to remember that, when condensation appears on a window, the problem isn’t the window itself; it’s the excess humidity in the home.
As defined by the Environmental Protection Agency, healthy indoor relative humidity levels are in the range of 30 percent to 50 percent. Persistent levels exceeding 50 percent are considered excess humidity in the home. The difficulty of maintaining optimum indoor levels are evident when you consider typical morning and afternoon outdoor humidity readings here in coastal Georgia. On an annual basis, Savannah averages a daily morning relative humidity of 87 percent and an afternoon reading of 54 percent—both levels exceeding EPA recommendations.
You and Your Windows
The potential impacts of excess humidity in the house on indoor air quality are well-documented. Toxic mold growth is triggered by chronically damp indoor conditions. Dust mites, a known allergy trigger, also proliferate when humidity exceeds 50 percent in the house. Certain chemical irritants like formaldehyde in building materials, glue and paint are more prone to vaporize into the indoor environment when relative humidity is high.
Windows are often the first place you’ll see the effects of excess humidity in the home. Why? Simply because windows are typically the coolest surfaces inside the house. Glass is a highly effective heat conductor—the reason a glass windowpane often feels cool to the touch even on a hot day—and forms a perfect ground zero for condensation. When warm, overly-moist indoor air contacts the cool glass, water vapor in the air naturally condenses to liquid and the familiar and annoying phenomenon of chronically wet windows occurs. (The same thing happens to the cool glass bathroom mirror when you take a steamy hot shower.)
Chronic window condensation is at first glance an aesthetic issue and a housekeeping challenge. Steam, spots and streaks marring sparkling glass are disconcerting. Nevertheless, keeping wet, drippy windows clean can be a losing battle as long as you have the combined effects of high indoor humidity and the laws of condensation working against you. However, in addition to the unsightly appearance of condensation, the status quo of continuous dampness is bad for the structure of the windows themselves:
- Active mold growth and mildew may appear around the perimeter of window panes. It usually manifests as a black residue that recurs despite frequent cleaning.
- Peeling paint, rotting wood and deteriorating joints develop in wooden window structures like the frame, sill and sash.
- Swelling of window components may also occur, making windows sticky and difficult to open.
Water Vapor Happens
Notwithstanding our humid coastal climate, a great deal of excess humidity in the home actually originates indoors. Moreover, in today’s homes, it stays indoors. Homes of the past were built to less stringent standards of air exchange with the outdoors. That’s another way of saying they were drafty. Today, however, energy-efficient residential construction is airtight; not much heat leaks in and not much, including water vapor, gets out. The indoor environment, therefore, becomes a zone of concentrated humidity with no exit. Sources of excess humidity in the home include:
- Bathing – A single hot shower puts a quarter-pound of moisture into household air.
- Cooking – Boiling water and frying and baking foods releases humidity. But even the gas flame that cooks food contributes, too. Water vapor is a by-product of the combustion of natural gas.
- Housekeeping – Mopping a floor adds humidity to the air.
- Laundry – Drying clothes raises indoor humidity, especially if the dryer vent isn’t fully intact and regularly maintained.
- Breathe in, breathe out – You’ve just raised the humidity level in your house. Exhaled air contains moisture. A family of four contributes several pounds of water vapor to the air every day just by the act of breathing.
- Infiltration from unconditioned zones – Since natural laws dictate that moisture flows from damp zones into dry zones, certain areas of the structure may serve as perpetual humidity reservoirs that continuously re-supply the living spaces with water vapor. Attics accumulate humidity from outdoors and from hot air rising out of the home, particularly when attic ventilation is less than optimal. The crawl space underneath the house may stay chronically damp from moisture rising out of the soil.
What Can You Do?
You can’t do much about Savannah’s naturally humid climate except talk about it. However, excess humidity in the home and the resultant signs of condensation on windows can both be reduced by taking proactive steps.
- If excess humidity in the home can’t escape the airtight confines of the house, you can help it out. Exhaust fans installed in zones where water vapor originates, kitchen and bathrooms, for example, convey moist air through dedicated ducts all the way to the exterior of the house. Most operate on a timer so the fan will continue to run for some time after it’s activated. Experts recommending running a bathroom exhaust fan for 15 minutes after showering or bathing to fully remove water vapor from the air.
- Circulation dries air and also makes the home feel cooler. Ceiling fans are great energy-efficient options to keep air in motion. Also utilize box fans to convey air into or out of enclosed rooms. Because of our high natural humidity, opening windows isn’t often a good humidity reduction strategy. But on those days when outdoor humidity dips, it’s another way to move air into and out of the home.
- Humidity infiltrating living spaces from the attic and crawl space must be stopped. The best way to do it is by inhibiting the accumulation of water vapor in these zones in the first place. Verify that attic air vents at the soffits and the roof peak are unobstructed to ensure maximum passive air circulation that keeps damp air moving out of the attic. Down in the crawl space, make sure all vents are open and consider having a vapor barrier applied to the dirt floor to prevent rising moisture from the soil pervading the space below your floor.
- Identify and seal cracks and gaps in the ceiling that allow high attic humidity to flow into the drier environment of the living spaces. Use caulking to close cracks around the long joint between walls and ceiling, as well as gaps around the perimeter of recessed ceiling lights and anywhere vent ducts or plumbing pipes pass through the ceiling. Also, weatherstrip the mating surfaces of the attic access hatch or pull-down stairs.
- Schedule annual tune-ups for your air conditioner at the outset of the cooling season. There’s a reason it’s called an air conditioner and not just an air cooler. Conditioning the air—reducing humidity by extracting water vapor at the evaporator coil—is an important function of the A/C process. Annual maintenance by a qualified HVAC professional includes cleaning the coil and verifying proper refrigerant level. Both procedures are critical to optimum humidity reduction.
- Maintain your clothes dryer, paying particular attention to the condition of the dryer vent. Check it regularly for lint accumulation that can block the flow of exhausting air and discharge water vapor into the air.
A Whole-House Approach
Talk to your HVAC contractor about mechanical options to reduce excess humidity in the home. One he may suggest is a whole-house dehumidifier. Installed directly into your heating and cooling ductwork, whole-house systems extract humidity from the air as it circulates through the ducts. Because the cumulative air content of the house moves through the ducts numerous times daily, continued humidity reduction of all the air inside the home is assured—unlike with portable dehumidifiers that treat the air in a single room only. Humidity levels inside the home can be fine-tuned with the digital humidistat that controls the whole-house dehumidifier. A whole-house unit is permanently plumbed directly into your household drain system and requires only annual maintenance by a qualified service person.
Learn more about how Byrd Heating and Air Conditioning can remedy excess humidity in the home with indoor humidity solutions, or give us a call at 912-373-8447.
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