Mold and moisture inside the wall cavities of homes, hotels, office
complexes, and a host of other buildings is causing millions, if not billions,
of dollars’ worth in property damages. In addition, this mold and moisture can
and will cause a wide variety of health problems for homeowners, tenants,
travelers, and the like.
Much attention has been given in recent months to problems surrounding buildings
clad in Exterior Insulation Finishing Systems (EIFS, or synthetic stucco). In
fact, a class-action lawsuit has been filed claiming that not only is EIFS a
faulty building product, but that improper installation techniques allow excess
moisture to penetrate the exterior finish and enter the wall cavity. This
moisture not only degrades the structure, but it allows mold to gain a foothold
inside the cavity. As a result, the EIFS industry is being forced to provide
free moisture inspections on virtually any synthetic stucco building. If excess
moisture is found, the stucco is replaced at no charge to the owner.
Doc
Air, LLC postulates that while moisture problems can indeed be the
result of improper construction practices in some cases, EIFS structures
generally develop moisture problems not because synthetic stucco is a bad
product; rather, the problems develop because the EIFS is an excellent product.
To explain, we must look at the home or building as a whole, considering
building dynamics and HVAC systems.
Buildings have been constructed increasingly tighter in order to save on energy
costs. As a result, these homes, hotels, and offices introduce less and less
outside air. In many cases, the outside air allowance valves or dampers are
bolted shut. When this phenomenon is combined with the practice of pulling air
out of the buildings (often through ventilation exhaust fans), a pronounced area
of negative air pressure with respect to the outside develops. This negative
pressure is exacerbated by normal (insignificant outside air intake) HVAC
operation and the “chimney effect.” The chimney effect refers to the natural
tendency of warm air to rise (as in a chimney or stack). Often, warmer air
constantly rises through a building, eventually escaping through an attic or
roof vent. To balance this flow, air must be drawn in from another source.
Since the volume of air entering a building must equal the volume leaving,
air is continuously being sucked in wherever possible. This would include
“sealed” penetrations in the exterior walls, window frames, door frames, and
gaps in the floor between the living space and the crawl space. If a wall is
watertight, it doesn’t necessarily mean that the wall is airtight. As this
uncontrolled outside air is brought into the wall cavity, it brings with it
significant amounts of moisture (especially on humid summer days). The excellent
insulating properties of EIFS maintain the temperature inside the wall cavity
very close to room temperature, which is often at or below the dew point for the
moisture-laden outside air. The moisture condenses, and the water becomes
trapped in the wall cavity. Over time, enough moisture will accumulate to allow
mold growth, degrade building materials, or both.
This negative pressure relationship is not unique to EIFS buildings, but this
group has received by far the most attention. Homes clad in brick, vinyl siding,
or other types of exterior finishes are also very susceptible to this ongoing
problem. All it takes is negative pressure inside the living space to begin
pulling air from outside.
The concept of negative air pressure is neither complicated nor is it foreign to
most indoor air quality (IAQ) professionals. However, the vast majority of these
people have not realized the significance of this information. Negative air
pressure is often treated as a minor player or small problem; rather, it is
often the primary cause for mold and moisture inside wall cavities.
The Solution: Proof Positive™
Doc Air, LLC has developed a procedure whereby we can quantify
the amount of air entering and leaving a particular structure due to pressure
imbalance. Using blower door technology, we are able to effectively analyze and
measure pressure differentials within the building. Once quantified, the
problems can be solved with the following steps:
Locate all major building leaks and repair using expanding foam,
weatherstripping, or silicone caulk.
Identify and repair any leaks or damage in HVAC ductwork.
Insert a small outside air allowance valve or ventilation system near
the HVAC mixing box, placing the home under positive air pressure.
Seal masonry-block basement walls to prevent air and moisture incursions.
Monitor the home over time.
Installing a valve or ventilation system for outdoor air allowance
allows for positive pressure inside the home by reducing the amount of
air intake through the return air vents. The HVAC unit will continue to
supply a constant amount of conditioned air to the interior of the
building. Since the supply air being discharged within the building is
now greater than the amount of return air being taken away, positive
pressure results.
Placing a building under positive pressure means that where outside air
was once entering through the myriad cracks and holes in the building
skin, now conditioned air is leaving. Outside moisture no longer enters
the wall cavity. Energy losses would be minor for air allowance valves
and non-existent for certain types of ventilation systems.
Positive building pressure is also a solution for radon problems. As
radon gas leaves the soil underneath a building, it often gets sucked
inside the structure due to negative building pressure. Positive
pressure ensures that any radon gas under the building will be unable to
migrate into the breathing environment.
Summary
A host of structural and indoor air quality problems can be directly related
to negative building pressure. With the Doc Air, LLC Proof Positive™ system,
negative pressure is eliminated. In so doing, moisture and mold in wall cavities
disappear, radon gas is unable to enter buildings, and millions of dollars in
repair work can be saved.
The
Problem
Doc
Air, LLC postulates that while moisture problems can indeed be the
result of improper construction practices in some cases, EIFS structures
generally develop moisture problems not because synthetic stucco is a bad
product; rather, the problems develop because the EIFS is an excellent product.
To explain, we must look at the home or building as a whole, considering
building dynamics and HVAC systems.