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Home::Michelle Annese
The Cause and Solution to Your Condensation Problems
Author : New Jersey Home Inspector Michael Del Greco
The Cause and Solution to Your Condensation Problems
Submitted by: Michael Del Greco, President of Accurate Inspections, Inc. a New Jersey Home Inspection company. Click here for a New Jersey Home Inspector.
The Cause and Solution to Your Condensation Problems
Condensation is caused when warm, moist air moves into a cooler air space or comes in contact with a
cooler object. The warmer the air is, the more ability it has to hold water. The cooler the air is, the less
ability it has to hold water (i.e., when warm, interior air comes in contact with a cold surface, such as a
metal window frame or cold water pipe, the vapors in the air turn to liquid on the colder surface).
In an attic in the winter, moisture or ice may form on the roofing nails and the roof sheathing for the
same reason.
Mold/fungus develops in bathrooms when vapors permeate through the surface of drywall or plaster and
turn to moisture before it exits the other side of the wall material. This is due to the change in
temperature between the living space (or warm side of the wall or ceiling) and the exterior (or cold side
of the wall or ceiling).
On milder days or milder climates, it is less of a concern because the temperature differential between
the inside and outside is not far apart. The solutions are ventilation, additional insulation, or stopping the
permeation of vapors through the wall/ceiling material. In existing situations, access is typically difficult
for proper ventilation or insulation. So the simplest approach would be to paint the wall and ceiling
surfaces with a material that would significantly reduce or stop the permeability of vapors. Most
enamels or hard-finish paints will do a good job controlling or reducing the amount of vapor which may
pass through the wall/ceiling surfaces.
The best way to ventilate an attic:
The air in attics is warmer than the outside air in summer or winter. It is obvious how warm attics are
in summer, but it may not be so obvious in the winter. Assuming the outside temperature is 35 degrees,
the thermal loss from the house will raise the attic temperature 5-10 degrees, depending on insulation,
wind, etc. Based on this information, the air in the attic will always be lighter than the outside air
because it is warmer.
The best way to ventilate an attic would be with high-low ventilation because the only condition we can
be sure of is that warmer air will be lighter and has a tendency to rise.
With high-low ventilation, the warmer air rises out of the high vents, preferably ridge vents, and this air
is replaced by cooler air from low vents, typically soffit vents.
The amount of air and the speed it moves is dictated by the temperature difference between the attic
space and the exterior. This is called thermal convection. When the ventilation is correct, mother nature
will control the air changes based on the temperature differentials and mechanical help is unnecessary.
General criteria for improving attic ventilation:
1) For every 300 square feet (SF) of attic floor space, you need at least one (1) SF of clear air. If the
clear air is not distributed 50% high and 50% low, you will need additional ventilation.
2) Louvers and vents are typically only 50-60% of their total measurement in clear air. Be sure to
calculate this when you buy these appliances.
Note: If you cannot develop high-low ventilation, you will have to increase the horizontal or high
ventilation by 100% or more, or approximately two (2) SF plus for every 300 SF of attic floor space.
Without a proper vapor barrier, it may be necessary to as musch as double the above ventilation.
Information provided by Michael Del Greco, New Jersey Home Inspector Lic. GI 0121, American Society of Home Inspectors Member 102273, Pesident of Accurate Inspections, Inc. A West Paterson New Jersey Home Inspection firm.
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