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Home / Internal Atmospheric assessment

Internal Atmospheric assessment

National Roof can install monitoring systems that assist in understanding the internal environmental conditions that can contribute to such moisture issues as migration, infiltration and or condensation within and through the building envelope.

The importance of controlling moisture in building envelopes is summarized by a few researchers below:

“Moisture is a leading cause of building deterioration. High moisture levels can cause decay, warping, or corrosion of materials. High humidity may result in mold, mildew, or staining and paint may peel or blister as a result of too much moisture. Moisture problems have been reported in basements, crawlspaces, attics, in and on walls, ceilings, and roofs and may occur in just about any other part of the building. Although moisture problems are so pervasive and detrimental, we have only a limited understanding of the causes of and conditions leading to the various problems. To provide practical information and advance our understanding of the complex movement of moisture in buildings, measurement is required, but the lack of suitable moisture-measuring equipment has impeded progress.”

Instrumentation for Measuring Moisture in Building Envelopes
A. TenWolde G.E. Courville, Ph.D.  ASHRAE Member

“Codes in the United States today fall far short of having appropriate requirements for controlling infiltration and moisture due to condensation in the building enclosure. Codes require ventilation of cavities in climates that are hot & humid, and it becomes counterproductive to ventilate those cavities. Codes are charged with protecting the health, safety, and welfare of the public; yet in this critical area of control that can cause mold, aggravate asthma, cause deterioration by corrosion and decay, and pollution migration within the building, they fail to represent a sufficient level of understanding of the mechanisms or the solutions.”  Moisture control requirements in codes”

– by Wagdy Anis AIA

National Roof can assist building owners and managers in the understanding of “building envelope moisture transport”, identify opportunities for minimization and influence the sustainability of roof & insulation system performance.

Pressure differentials:

Excessive pressure differentials existing between external atmospheric pressure and inside environmental conditions, in either direction, can and will adversely impact roof and wall seals over time, will exploit and exacerbate air barrier and vapor barrier deficiencies, and will relentlessly work to move moisture laden air throughout the building envelope.

The driving forces for air exfiltration and infiltration through a building envelope are usually due to either:

Pressurization or de-pressurization of a building occurs by:

  • mechanical equipment
  • manufacturing process(es)
  • HVAC operation
  • Wind

“Except for structural errors, about 90% of all building construction problems are associated with water in some way” ASTM

National Roof has the ability to install pressure differential monitors that collect real time data for long periods of time, store the data digitally for wireless transmission or download for analysis and statistical interpretation, resolve the data into air exfiltration and/or infiltration quantities using scientifically generated algorithms, and make roofing recommendations that coincide with this data.

“The infiltration of humid outdoor air is a major problem for many manufacturing facilities. In particular, manufacturers that produce such items as absorbent hygiene products or humectants must control the humidification conditions in order to ensure product quality and high first-run yield. This paper describes a technique of using differential pressure analysis in order to estimate the volume of air entering such a facility through its various cracks/crevices, windows, doors, and other openings. A mathematical relationship, based upon a best-fit graphical estimation, was presented that related the pressures of the air imbalance with the rate of outdoor air infiltration. With some specific conditional modifications, this approximation could also be applied to other comparable scenarios found in the manufacturing environment.”

“An air mass imbalance can result in a pressure difference between the inside and outside of the manufacturing space. This pressure difference is readily noted when, after entering a particular space, the door slams shut immediately on manufacturing personnel. In many cases significant infiltration airflow velocity is evident in the large passageways and doorways leading into a particular manufacturing space from adjacent areas such as raw materials storage, maintenance shops, and finished goods spaces. A major issue with an imbalance air condition at many manufacturing sites during the summer months is the infiltration of outside air at unacceptable moisture content levels.  The affects of humidity on office and manufacturing personnel is widely documented in the literature 1-5.

However, research efforts or case studies targeting humidity concerns related to product performance or quality are somewhat limited. Some production items by their very nature, such as absorbent hygiene products and various humectants, must be manufactured in controlled environments free from the potential detrimental effects of high humidity conditions. Efforts have been made to cut down on the amount of outdoor air that infiltrates a building from various cracks, crevices, and other openings in buildings that house these types of operations as well as others 5-8.

Mathematical relationships can be used as a means of estimating the extent of a particular outdoor air infiltration. The literature provides several accounts of mathematically estimating specific airflow balances/imbalances and pressure differentials 7-10. The proper use of these relationships can assist in the development of an effective and efficient strategy for taking corrective action when the environmental conditions are less than optimal. The purpose of this paper is to describe a technique used to conduct a differential air pressure analysis at a facility that experienced problems with moisture control and an excessive negative pressure differential plant wide. In order to estimate the severity of the problem, differential pressure measurements were performed around the perimeter of the manufacturing space under a range of manufacturing space operational conditions. These measurements were then used to estimate the extent of outside air infiltration.”

The Application of Differential Pressure Analysis In Determining the Extent of Outdoor Air Infiltration into Buildings –

Robert Choate, Department of Mechanical Engineering, Western Kentucky University

Rod Handy, Department of Mechanical Engineering Technology, Purdue University

Kevin Schmaltz, Department of Mechanical Engineering, Western Kentucky University