Building Enclosure defects can be expensive to correct, difficult to diagnose and can leave your facility vulnerable to issues such as indoor air quality problems. C.L.I. has worked on many area buildings that are suffering from such problems. In many of these cases, in addition to problems in design and construction, building owners are also faced with expensive mold remediation projects, damaged structural components and litigation.

C.L.I. Group, LLC is a member of the Building Enclosure Technology and Environment Council (BETEC)

 

Has Your Building Experienced...

- Excerpt from the 2005 National Institute of Standards and Technology (NIST) report, Investigation of  the Impact of   Commercial Building Envelope Airtightness on HVAC Energy Use.

According to the National Institute of Standards and Technology (NIST) report, Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use, the inclusion of an air barrier system in four sampled types and sizes of building reduced air leakage by up to 83 percent. This represents a large reduction in current and future energy consumption and operating costs: potential gas savings of greater than 40 percent, and electrical savings of greater than 25 percent.

Below are photos from a recent project performed for a large church. When the C.L.I. Group became involved, all parties were under the assumption that the doors and windows were leaking, which caused wet carpets near exterior walls, mold and odors. Our diagnosis, after investigating was much different. The masonry exterior walls of the church were built with an inadequate drainage plane and flashing. The ductwork was in a drop ceiling and was excessively leaky, thereby de-pressurizing the conditioned spaces. The difference in vapor pressures from exterior to interior, the hygroscopic capacity of the exterior brick, solar radiation and poor drainage plane added to the negative room pressures WRT outdoor led to significant amounts of moisture and condensation forming in the wall cavities. The steel stud framing also acted as a thermal bridge which made the problem even worse in the winter. The result was deteriorated framing, water damaged drywall and sheathing, mold and other issues. This problem was allowed to manifest itself over months due to numerous misdiagnosis of the problems.
 

 Recent Wall Cavity Investigations Involving Large Commercial Buildings (Church & Area Hospital)

The case above is one of several we have recently been involved which have similar problems. In most cases, the building owners had already spent thousands of dollars trying to correct the problems with little success. Such problems can only be diagnosed and corrected using an "holistic" approach to the problems. Our team of professionals includes building science professionals, professional engineers, indoor air quality professionals and air and balancing experts that can evaluate the building in it's entirety. It is important to understand when trying to address such problems with one specialty contractor, that in such cases, changes to one system of the building will affect other systems of the building. Those not understanding this holistic approach to buildings can have good intentions, but can actually make the problem worse.

By measuring the performance of the building and it's systems. Our team understands these important interactions and also has the ability to verify the results. This building enclosure was modeled before opening to evaluate problem (condensation) potentials. See sample condensation analysis model.

Air Leakage and Energy Costs

There is little attention paid to air leakage through the building enclosure when commissioning is performed on a building. The commissioning process has typically dealt with the performance of the HVAC system and Lighting. What has been missed is the fact that even a commissioned HVAC system can be inefficient due to factors that are not evaluated. The major oversight in the commissioning process has been air leakage through the building enclosure. This is typically accounted for in design by making assumptions about the amount of air leakage and then sizing systems based on those assumptions. This results in poorly performing buildings with over-sized or under-sized systems (generally over-sized). NIST performed a study on the impact of air leakage below is a link to a summary of their findings.

The results of this study estimated that infiltration is responsible for about 15% of the total heating energy and 4% of the total cooling energy for U.S. office buildings. Results also indicated that potential energy savings on the order of 26% for heating load and 15% for cooling load could be realized by tightening building envelopes by 25% to 50%. The study also revealed the difference in the contribution of infiltration to the heating and cooling load depending on whether the building was pressurized or depressurized with respect to the outdoors.

The study shows the importance of understanding not only air leakage through the building envelope, but also shows how pressures within the building can affect the air movement. These costly and important issues have gained importance in recent years due to increasing energy costs for building owners.

Envelope Assessments

For any of the following types of building envelope assessments, we begin by gathering as much information as possible from the owner. Items which may be helpful in our assessments include: as-built drawings, specifications, shop drawings, maintenance schedules & records, documentation from previous maintenance and repairs, etc.

Types of Assessment:

Understanding Enclosure Loading

In order to successfully design, build and maintain a building enclosure, one must first understand the conditions which will affect the enclosure, both from interior and exterior loadings. The inter-relationship of the loadings which will affect the building must be understood from the onset if a building is to perform as intended. Understanding issues such as temperature, pressure and humidity during the design and construction phases would help to reduce the number of problems being experienced in buildings. Most of the loadings which a building enclosure experience are dynamic and the designer should understand the dynamics which will affect building enclosure performance by modeling as many of these conditions as possible during the design phase.

We have modeled some of those issues for the Cleveland area in the charts above. The inter-relationships between these dynamic building enclosure loadings is what fuels many problems in buildings. By understanding the dynamics of these parameters, designers could accommodate many of these inter-relationships which would aid in lessening some of the most common shortcomings in the building enclosure.

Failures Which Could Have Been Avoided

Poor attention to detail led to the catastrophic failure you see below. Careful attention to detail is required on thin stone veneer, much the same as barrier type stucco installations. The ability of stone to hold larger amounts of moisture against the exterior sheathing makes this even more critical in such installations. It is important to remember that water will get in. Once it does get in, where is it going? Not answering that question in advance could be a costly mistake. 

Commissioning The Building Envelope for Moisture Management

Moisture control problems account for up to 80 percent of all associated premature wear expenditures made on built facilities. Although proper commissioning procedures have been noted to reduce the potential for approximately 70 percent of these claims, no standards exist for the control of moisture migration in building commissioning guidelines. The development of commissioning guidelines for the control of moisture migration involves quantifying, with a risk management approach, the performance thresholds that distinguish acceptable from unacceptable design. These criteria should define allowable threshold values regarding mold growth, corrosion, loss of structural strength, and indoor air quality. This report includes an introduction and brief history of building commissioning and the code regulations intended to address moisture in buildings, a description of the commissioning process as related to the building envelope in humidified buildings, and discussions of building humidification and the criteria and guidelines for commissioning humidified buildings. The guidelines explain the role of a building envelope commissioning agent, from early in the design phase, through construction, to assuring proper operation after occupancy. This process includes the use of performance modeling techniques to predict the envelope performance prior to completion. Establishing guidelines for the commissioning of humidification is an important step toward anticipating and preventing the conditions that may lead to moisture problems and related health effects and maintenance expenditures.

Commissioning for Humidified Buildings, Brian M. Deal, William Rose, and Scott E. Riley, USACERL Technical Report 99/03 November 1998

Thermal Bridging

Thermal Bridge - a heat-conductive element in a building assembly that extends from the warm to
the cold side and provides less heat-flow resistance than the adjacent construction.

Thermal bridging is related to many comfort complaint, moisture issues, mold, structural degradation and other issues in buildings. However, it is often overlooked in the design phase. Thermal bridging is also the culprit in many comfort complaints and other issues in buildings and is often overlooked. This can end up costing owners thousands of dollars for unsuccessful repairs. This issue is again related to "holistic" building evaluations when problems arise. The knee-jerk reaction to the majority of comfort complaints is to call the HVAC contractor and blame them for poor thermal comfort. The owner, in turn makes these service calls annually and may even replace systems in an attempt to correct the problem. The results of these service calls and system replacements will likely be unsatisfactory. The issues relating to thermal bridging would have been best addressed in the pre-design phase of the building. However, these issues can be diagnosed and corrected in existing buildings if a qualified building science company is brought on board to evaluate the building and problems from an un-biased, holistic approach.

The wall components and overall thermal performance should be evaluated in the design phase as part of commissioning the building envelope. Below is a thermal analysis from an exterior wall which was framed with 2.6" steel studs and was experiencing thermal bridge, condensation and comfort problems. ASHRAE 90.1 includes de-rating factors for insulation R-values when fiberglass batts are installed in steel stud walls. The R-19 insulation actually performs as R 8.6.

The loss of R-value in such wall construction is what led to the "continuous insulation" (c.i.) requirement in the standards. This increases the resistance to heat loss by breaking the thermal bridges. SOMETIMES!! There are other factors which must be considered. The continuous insulation will only work to stop thermal bridging if other factors are also functioning as intended. These other factors include having a good air barrier to prevent unconditioned air from coming into contact with steel framing and paying attention to wall/foundation junction.

Waterproofing Principles

Principle One: The 90%/1% Principle - As much as 90% of all water intrusion problems occur within 1% of the total building or structure exterior surface area.

Principle Two: The 99% Principle - Approximately 99% of waterproofing leaks are attributable to causes other than material or system failures.

So what does cause the numerous failures we see? Human installation errors, poor attention to details, improper system choice for the application, inadequate surface preparation, poorly trained workers, poor terminations, material incompatibilities to name a few. The two principles mentioned above come from the Construction Waterproofing Handbook by Michael T. Kubal (McGraw-Hill, 2000). It has been our experience that his principles are very accurate. The waterproofing handbook goes into great detail concerning the building envelope and how systems must function as a whole. This advice should be carried through to an understanding that not only the building envelope, but the entire building should function as a whole. A failure in one component can and does affect other components in the building. The principles mentioned here could likely be transferred to just about every component in any building. The majority of failures appear to be in areas other than materials and/or system failures.

Our experience has led us to believe that it is this lack of understanding that a building is "holistic" and must be constructed, operated and maintained using an "holistic approach". To that end, we have developed investigative procedures that evaluate the roles of different integrated components in the overall performance of the buildings we evaluate.

When evaluating water and/or moisture issues in a building, an understanding of waterproofing systems and membranes is essential. Most buildings will have several types of systems in place dependent on the particular application (e.g. below grade, above grade, horizontal and vertical applications, plaza deck, green roof systems, roofs, etc.) These systems, although each performs it's own function must also perform "holistically" in order to maintain the envelope of the building. It is with this and the 90%/1% Principle above that failures must be considered. Surprisingly, in many cases moisture issues are related to other failures in the building and not waterproofing membranes. Poor attention to flashing, building pressures, thermal bridging, air leakage in the envelope and other issues may be at the root of the problem. As an example, a poorly installed air handler and/or duct system can act to depressurize interstitial spaces and actually suck moisture into these hidden spaces. These problems often go unnoticed until a significant amount of damage has occurred. With such problems, building owners turn to roof contractors, waterproofing contractors, etc. to find and fix the problem. Many thousands of dollars later the problem is not only still present, it has worsened as the result of more time lapsing. This goes back to C.L.I. Group's reasoning on independent third-party evaluation. We can look at the problem from all angles because we have no particular interest.