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Humidity is important to our home
and health and it
is important to maintain the proper humidity levels in our homes and
workplaces for our health. What is humidity? Humidity is simply little
water droplets in the air. Cold air is nearly saturated with these
little water droplets because the properties of cold air allow the air
to hold more water droplets or humidity. As air is heated it expands
and holds less humidity. When you heat the air in your home using a
furnace, boiler, or heat pump this air expands and becomes drier. It is
air with less humidity relatively speaking before it was heated and
compared to the outside air. Air that is 30° F with 80% humidity
will
only be 15% humidity at 75° F. That is a big difference in humidity
levels in the home after the air is heated. Granted, you are not
heating air from 30° F to 75° F with your furnace. Depending on
the set
up of your thermostat and heating system you are most likely heating
air that is 68° F to around 70° F to 75° F depending on the
thermostat
setting. The point is unless you have a source providing humidity to
the airstream you are simply reheating dry air from inside the
structure. There will be minimal infiltration humidity but the
infiltration humidity will never be enough to bring the humidity levels
up to healthy levels inside the structure for the inhabitants, plants,
and furniture.
The Study of Psycrometrics
Yes, that is psycrometrics
and it has nothing to do with psychology. It is the study of air and
its properties. It is used in HVAC by HVAC technicians and HVAC
engineers to determine the properties of air. The HVAC industry uses
Psychrometric Charts to plot the properties of air. Using the
Psychrometric Chart a technician or engineer can determine the relative
humidity, enthalpy value, dry-bulb temperature, wet-bulb temperature,
dew point and vapor pressure if they have a few of the listed values.
With this data engineers and technicians can solve problems or assign
values and set points. For example, an economizer system that is
controlled by the building automation system can be controlled by an
enthalpy value. This value associated with an "And
Gate"
will only allow the economizer to open under certain conditions that
will allow the mechanical cooling systems to shut down and take in free
cooling from outside the structure. The temperature, humidity, and all
the properties of the air will be optimum for free cooling using the
economizer. By knowing the properties of air one can set up HVAC
systems to work better and one can also use the data provided by
knowing the properties of air to troubleshoot problems with HVAC and
building systems.
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Indoor Air Quality and Proper Levels of Humidity
It is important to maintain proper levels of
humidity in the home for many reasons. Comfort is one factor, indoor
air
quality is another factor, and saving energy is another factor. All
three are related in one way or another but each are separate factors.
If you reside in the northern climate regions where the average
temperatures are less than 20° F you want the indoor humidity to be
relative to outside air humidity. Temperatures about 20° F the
recommended relative humidity inside the home or business is 35% to
45%. The construction of the home or business will also determine the
amount of humidity. If you have proper vapor barriers and good tight
windows and doors you need a good mechanical ventilation system.
Humidity levels can rise above 60% causing excessive moisture inside
the structure which will lead to mold, mildew, and possible water
damage. Make sure you have a good mechanical
ventilation system
inside your structure to avoid moisture issues. Bathroom ventilation
fans, hood fans over stoves, and other type of exhaust fans inside the
structure pull out excessive moisture when cooking or showering. If you
have this problem it most likely shows up in the form of mold growth
inside closets, kitchens, bathrooms, and ceilings. Additionally, if you
have excessive moisture problems your windows will frequently fog or
have a lot of moisture on the windows.
During the humid, languid days of summer, an
air conditioner
can make your house feel less like a steam bath and help prevent the
unpleasant, musty smell that's a sign of a damp home. But during cooler
weather or in your basement or crawl space, a dehumidifier is the best
way to reduce humidity levels. (For more information on keeping
moisture out of your home, read Keep moisture out from our report and
review of dehumidifiers.)
Dehumidifiers
do more than just enhance your comfort. By keeping humidity at the
proper level, these machines will prevent a host of problems. Left
unchecked, a household relative humidity above 50 percent can breed
mildew, dust mites, and mold that exacerbate allergies and asthma.
Mildew and mold can thrive on and discolor cloth or natural-wood
furniture and grow on clothes, books, and other items stored in your
basement or elsewhere. An increasingly common household problem in this
country, mold can also cause drywall and wood to rot, resulting in tens
of thousands of dollars in structural damage.
While preventing mold requires also properly sealing and ventilating
your home, a dehumidifier can reduce potential for its growth.
High
humidity could especially be a problem in new homes. "New construction
is even more vulnerable to mold because homes today are made mostly of
paper-faced wallboard instead of wood and plaster, which are more
mold-resistant," says Lew Harriman, a humidity consultant and member of
the American Society of Heating, Refrigerating and Air-Conditioning
Engineers.
Using
a dehumidifier in a cool, damp basement or crawl space is ideal for
treating humidity-related problems. The dehumidifier uses a fan to pull
room air over two sets of refrigerant-filled coils, one cool and the
other warm, wringing out moisture along the way. The water that
condenses out of the air typically drips into a bucket inside the
dehumidifier. Most units can be connected to an external drain,
eliminating the need to empty the bucket.
Low Humidity Levels
Low humidity levels cause problems also. Static
electricity, dry skin,
dry sinuses, and other health problems including increased flu illness
can occur. Additionally, low humidity levels cause problems with wood
inside the home. To test for low humidity levels in the home make a
glass of ice water and set it somewhere away from the kitchen or
bathroom. If after five minutes water droplets do not form on the
outside of the glass then you have a problem with low humidity levels
in your house and you need to get a humidifier. If your structure is
suffering from low humidity levels you will also feel cooler resulting
in a desire to turn the thermostat up. Therefore adding a humidifier
to the HVAC system will cause you to turn the thermostat down. The
proper levels of humidity in your home can increase comfort, save you
money on your utility bills, and make you healthier.
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