Humidity, Water Damage in Collingswood NJ, Condensation, Mold, and Indoor Air Quality, in Collingswood NJ,

Humidity, Water Damage in Collingswood NJ, Condensation, Mold, and Indoor Air Quality, in Collingswood NJ,

Moisture rides on air currents, and warm air carries more moisture than cool air

To control air flows, make sure the air barrier is continuous

An air barrier helps control airflow both through and within the building enclosure. By controlling airflow, you also control moisture.

If moist indoor air contacts a cold surface — for example,
exterior sheathing in cold weather — condensation can result. An air
barrier prevents those cold surfaces from being connected with humid
indoor air.

Air has a maximum storage capacity for water vapor which depends on temperature. Warm air can store lots of moisture, while cold air can store very little.

As the temperature falls from 90°F down to 20°F, the amount of
moisture that can be stored in the air changes by a factor of ten.

Leaky homes didn’t have condensation problems

Older buildings rarely had condensation problems in cold weather
because they were so well ventilated — meaning leaky. The relative
humidity in an old home would rarely rise above 25%. As we have built
tighter houses (and in some cases failed to provide mechanical ventilation), the indoor relative humidity has gone up.

In a heated, tight, unventilated house, the amount of moisture in the
air and the amount of condensation that can occur are dramatically
different than in an old leaky house. Condensation can occur wherever
water vapor can find a cold spot — on roof or wall sheathing, on the inside faces of the windows, and inside the walls.

Let's say it’s 40°F outside and the outdoor relative humidity is 50%.
If you allow that outdoor air to enter a building and heat it up to
70°F, the amount of moisture in the air stays exactly the same, but the
“tank” gets bigger because the storage capacity of the air increases
with the temperature. As a result, the relative humidity initially
drops. Then, as moisture is added to the air, the relative humidity
rises, and the absolute moisture content rises as well. How do you add
moisture to the air? You breathe, sweat, boil water for spaghetti, take
hot showers, grow houseplants — and all of those activities generate
moisture.

When does indoor humidity become a problem?

Let’s say that air leaks out of a house through holes in the
enclosure. As it reaches surfaces colder than 52°F or 53°F, the air will
cool. Once it reaches its full capacity to store moisture, condensation
occurs.

If the temperature of the outdoor air is around 30°F, the indoor air
will drop all of the moisture that it gained on the way out, dumping it
on the cold sheathing surface. That’s a typical example of the air
leakage condensation cycle. Since condensation in walls can
cause puddles — and in extreme cases, rot the framing — condensation is
something you want to avoid. Installing an air barrier is one way to
help prevent condensation.

Air conditioning can also create condensing surfaces

The same phenomenon can happen in reverse in the summertime. Let’s
say the outdoor air is 85°F and the relative humidity is 75%. When
outdoor air leaking inward contacts a surface below about 76°F, the
moisture in the air will condense. So if you have an exhaust fan in your
home, the air leaking in may cause condensation on the air-conditioned
surfaces — for example, on the back side of vinyl wallpaper.

If moist air leaks into a house through gaps in the wall or roof, you
can have problems. But in a tight house with a good air barrier and a
supply-only ventilation system, most of the air that’s drawn inside is
drawn in through the air conditioner, so the first cold surfaces it sees
are the cooling coils.

If you have air leaks in your building envelope, you usually can’t
see the condensation —Unless you have an Infrared Camera with a Visual
Inspection. However, condensation is sometimes visible in the attic; all
you have to do is look for frost or dampness forming on the underside
of the OSB or plywood roof sheathing.

Jon Barrett

Marketing and Sales Support

SERVPRO of Cherry Hill/Haddonfield

Phone: (856) 662-2772

Email: JBarrett@SP9157.com

Websites:

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