Originally posted Tuesday, 30 October 2012
Written by Fiona Aldous
The primary function of a building’s “skin” is to provide shelter and to protect the inhabitants from the threats of the exterior environment by providing a comfortable, conditioned (as needed), secure, and aesthetically pleasing interior space. The skin of a building can also provide a statement on the type of facility, organization, and values of the inhabitants or culture. For example, an art gallery skin may appear to be a work of art itself, while a courthouse skin may reflect the dignity and order of its society. Beyond iconic buildings, the skins of the bulk of institutional, commercial, and office buildings reflect the basic needs of their inhabitants, while striving to fulfill rapidly changing needs and remain cost effective and energy efficient—all in an economic and continuously changing, theoretically “new-is-better” built environment. Overall, the building’s enclosure can significantly impact the success of a facility, and it is a critical factor in “saving your skin” for any Owner.
Building Enclosure Failures, Energy Usage and Cost
Because water leakage, air leakage, thermal discomfort, and microbial contamination are fairly common occurrences, the building enclosure is often subjected to intense scrutiny by inhabitants. Something as seemingly innocuous as noise can even become an issue. This was recently demonstrated in a New Orleans high-rise following Hurricane Katrina, when wind whistling through gaps between the glass and curtainwall frame generated numerous tenant complaints. Resolution of this problem not only calmed landlord/ tenant relationships, but not surprisingly, it also significantly reduced energy usage!
The building enclosure and the heating, cooling, and air-conditioning systems are interdependent. The internal air pressures, air temperature, and humidity play a significant role in the performance of the enclosure. The building enclosure’s layers to control heat, air, and moisture/vapor must be:
• Properly designed and constructed
• Appropriate to the climate of the site
• Coordinated with the mechanical system
• In accordance with the principles of building science
• Hopefully supported by good design
In short, the building designers must consider environmental siting, building shape and configuration, incorporation of sun shading, natural lighting, window-to-wall ratio, and appropriate insulation—to name just a few factors that influence the durability, maintenance, cost, and success of the skin!
Today, it is well documented that existing buildings constitute one of the greatest users of energy. Whether a re-clad, re-roof, or comprehensive retro-fit of the facility is appropriate, building enclosure retro-commissioning can assist in achieving the desired performance and results through the independently performed application of the process. Any building enclosure retro-commissioning project should begin with:
• An initial understanding of the Owner’s concerns and objectives, combined with an evaluation of the current performance of the enclosure of the facility
• A review of energy use and analysis of potential cost savings
• An analysis of the relationship between HVAC and the enclosure
We recently teamed with a prominent architectural firm to assist a hospital in following up on complaints that the aging façade was leaking and thermally inefficient, leading to condensation in some areas. First, we conducted studies of the façade and implemented a program to address uncontrolled water infiltration. Then, during design development, we focused on methods to systematically install a new primary interior control layer that would suffice as the exterior layer of the façade, as the current outer “skin” was removed and upgraded to meet the demands of the facility.
Smaller retro-commissioning activities, more commonly referred to as forensic investigations, may not require such extensive commissioning activities, but similarly serve to repair known deficiencies and mitigate risk related to the performance of the building enclosure.
Owners who have experienced forensic investigations on the enclosure of existing buildings know very well the unfortunate necessity of such interventions. Such owners are often the greatest proponents of building enclosure commissioning for new projects. Often there are tales related to years of litigation; numerous visits by consultants and experts, each independently assessing the problem(s); and a final resolution and repairs. All the while, the problem persists, resulting in disruption to operations, closure of spaces, and potential impact to the actual function of the space. In an extreme case, a recent forensic investigation of water leakage at the roof-to-wall interface closed a one-year-old building that contained a laboratory. This had a negative impact on years’ worth of research, as results were no longer verifiable or repeatable. Costs associated with that loss were unquantifiable.
Building Enclosure Commissioning (BECx)
Building Enclosure Commissioning (BECx) is a quality-oriented process to enhance the delivery of a new building or the retro-fit of an existing building in accordance with the Owner’s Project Requirements (OPR). The process includes tasks to achieve, verify, and document that the enclosure design and construction meets the expectations of the Owner and the performance criteria identified in the Construction Documents (CDs). The BECx process is comprised of numerous tasks and is performed during the standard phases of a project: Pre-Design, Design, Construction, and Occupancy. The primary tasks include:
• Establishing a well-defined OPR and BECx Plan
• Verifying that the details and specifications meet the OPR through careful design reviews of the CDs performed by a party knowledgeable in the detailing, performance, and construction practices/installation of building enclosures
• Developing a building enclosure specification for inclusion in Division 1 of the Project Manual, inclusive of projectspecific field testing
• Reviewing construction phase submittals and developing project-specific checklists
• Laboratory or field mock-up of building enclosure and testing to validate performance
• Periodic or ”milestone” observing, documenting and reporting of work during construction for compliance with CDs • Testing of assemblies throughout construction to validate performance
• Report for the building enclosure “close-out”
• Facility personnel training related to building enclosure operation and maintenance
Total Building Commissioning and the Enclosure
The term BECx arose following the National Institute for Building Science’s (NIBS) concept of Total Building Commissioning. Each system to be commissioned should follow the process established by ASHRAE Guideline 0: The Commissioning Process. The building enclosure is a critical component of the building as a total system. The challenges in achieving a successful building enclosure have become more broadly appreciated, in part due to the knowledge shared through the development of regional Building Enclosure Councils across North America and the demands related to design complexity, sustainability, and energy consumption. This building enclosure challenge was originally met six years ago with the original publication of the ASHRAE / NIBS Guideline 3 – 2006, and currently, with the updated version of NIBS Guideline 3 (2012) Building Enclosure Commissioning Process . The greater interest and understanding of the impact of the building enclosure has also sponsored the development of an ASTM document on the practice of BECx, following the successful implementation of the process across the country, adoption of NIBS Guideline 3 BECx by the USGBC’s Leadership in Energy and Environmental Design (LEED) 2009 NC program, and many government and state agencies, and institutions.
However, confusion and miscommunication amongst many Owners and MEP Cx Authorities sometimes still surrounds the concept and implementation of BECx. Projects pursuing LEED certification can achieve one “design innovation” point or one “enhanced commissioning” point for undertaking BECx. However, the majority of these organizations provide no basic outline of the services that define or clarify the scope of BECx, and written requests are often required by the Architect to clarify the requirements. However, it is anticipated that with the adoption of LEED NC 2012, greater clarification will be provided.
BECx is also pursued under numerous project delivery methods, including Design-Build. This method requires the Owner maintain a keen focus on his best interests throughout the project. Ideally, under all project delivery methods and especially significant for Owners operating under the requirements of public funding, it is important the Owner retain independent and objective commissioning, similar to materials testing, in which the Owner controls the process. To benefit from “commissioning,” BECx should be initiated in the pre-design and design “verification” phases, and it should continue through the construction “validation” phases and into the occupancy of the facility. Without this comprehensive process, the concept will likely fall far short of its planned potential.
Enclosure performance issues should be detected and/or prevented early on in the project rather than be identified mid-way through construction by a performance test. The greatest misconception of BECx is that the BECx process for the enclosure is like the HVAC Cx process and can involve just a few performance tests following completion of construction of the enclosure, or worse still, is solely a whole building enclosure air pressure test or thermographic scan accomplished at the very end of building delivery.
NIBS and ASHRAE characterize total building commissioning as an Owner-driven and collaborative process. As a component of this process, the Building Enclosure Commissioning Authority (BECxA) is best contracted directly by the Owner or as a sub-consultant to the overall Commissioning Authority (CxA). The BECx process does not infringe upon the contracted obligations of the design and/or construction entities. The Owner should take an active role in determining the direction of the Cx team. Three key steps to a successful BECx project include:
1. Pursue a commissioning “process” that allows for flexibility and adaption to suit the specifics of the project, in combination with an experienced BECxA. Develop a project specific commissioning plan that can meet the defined budget, while not compromising the quality objectives of the Owner. Find the best BECxA for your project through a qualifications based search, not a costcentered search.
2. Maintain focus on the Owner’s occupancy requirements, not only on achieving performance intent during the design and construction phases. The BECxA will perform specialized building enclosure design reviews to enhance the quality of the building enclosure during construction and to achieve a long-term durable and sustainable skin.
3. Develop a BECx specification section tailored specifically to the project that provides guidance to all the parties throughout the construction process. Effective communication starts with a clear outline of roles and responsibilities. The BECx specification section is the path to success during the construction phase.
Don’t Expect What You Don’t Inspect
The success of the building enclosure ultimately rests with the design and construction team. Some Owners may rightfully argue that the BECx process outlined above should inherently be a part of the professional services provided by the design and construction team, and that you should not pay for something twice. Those who receive what they expect are indeed fortunate. Those who nod in agreement with the notion outlined above regarding inspections realize that a quality oriented BECx process on behalf of the Owner constitutes good practice, and on occasion it may well serve to “save your skin.”
Fiona Aldous is an Associate Principal with Wiss, Janney, Elstner Associates, located in their Dallas, Texas, office. Early in her career, Fiona taught architecture and design-build at the university level, and she gained further experience while working for a national contractor in design-build and building enclosure projects as a field engineer and superintendent. As a member of ASHRAE, she actively serves of technical committees encompassing Building Materials and Building Envelope Performance and Building Commissioning. As a member of Building Enclosure Technology and Environment Council (BETEC), she serves as the National Co-Chair for the Building Enclosure Council and has written and made numerous presentations on various aspects of the building enclosure. Fiona can be reached at firstname.lastname@example.org