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Doc Air's Proof Positive™
Click here for a brief overview of Proof Positive™
 The Problem
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.
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