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Avoiding Building Envelope Failures
Prevention in New Construction
Many Owners who are planning new buildings are familiar with ice dams and other building envelope problems and wish to prevent these insidious cold-climate problems and the related maintenance and repair costs. Most of the problems they have experienced or heard of could have been avoided at the design stage, and all could have been diagnosed and prevented during the construction phase. It is possible to significantly reduce the likelihood of having building failures with a design review and the use of a quality assurance protocol, both of which can easily be incorporated into the design and construction phases of the project. These provisions should be seriously considered for all new construction projects for the following reasons:
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Quality assurance procedures are inexpensive and the downside of not doing them can be financially catastrophic.
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Almost all building failures, whether related to temperature or moisture issues, are also related to wasted energy. Preventive measures are paid for by the energy saved.
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Preventing building failures during the construction phase is inexpensive; fixing failures after the building is finished and occupied is very expensive (to say nothing of the disruption, cost of related maintenance, and the loss of good will).
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Most building Owners are concerned with the efficiency of the “systems” that create or use the energy in their buildings, but there is usually very little focus on the “vessel” that can either waste or conserve that energy. The two go hand in hand.
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Buildings can be built right, even if they are large commercial buildings or very complex structures. Example: the new Vermont Law School building is reported to be one of the most energy-efficient buildings in the world. The designers attribute its success to both the building envelope and its energy management systems.
A survey of new buildings similar to the one you are planning would yield a nightmarish list of projects with damage from ice dams, freeze-ups, and indoor air quality problems. New building owners usually can’t afford these problems, especially when they can be prevented. Usually these problems result from a lack of attention to detail. It is difficult to justify the expenses involved in fixing these building failures when they really are easy to avoid.
The following process focuses on eliminating typical causes of ice dam formation, freeze-ups, and general heat loss problems commonly present in new construction. It only addresses building envelope problems, but the general concepts can be applied to heating, ventilating, and other energy management systems as well.
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Complete a review of the architectural plans to identify likely problematic areas of the building configuration and details that typically lead to building envelope failures. Ideally this will be done in advance of bids so that any details that are changed are incorporated into the pricing.
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Complete a review of the architectural specifications to verify that all components of the building envelope that typically lead to building envelope failures are included and properly addressed.
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Propose minimum performance standards for inclusion into the project documents. (See Sample Specifications).
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Propose quality assurance procedures for inclusion into the project documents. (See Sample Specifications).
Following is a more detailed description of these steps.
Plan Reviews
Because a significant portion of FOAM-TECH’s work is in repairing building failures, we are in a unique position to anticipate and identify critical details that typically lead to failures. We have learned that plan reviews and performance standards are a win-win situation for everyone involved. The architect has a satisfied client, the builder can include work in his bid that will allow him to detail and quality assure the building, and the subcontractor can price his work to meet standards in an extremely competitive market. Reviewing architectural plans and details can save the costs of call-backs and disputes over the responsibility for building failures. Most building failures have similar causes that can be avoided by good detailing and performance-based specifications. Detail changes and related performance specifications are included into the review process report. These reviews are used to avoid liability and guarantee quality for the client.
Keys to Success
Having the plans reviewed is only half of the battle. Incorporating the adopted recommendations into the bid documents is crucial to their implementation. All too often, recommendations that could be low-cost or no-cost during the construction phase do not make it into the original contract documents. Attempting to address problem details late in the construction process makes the upgrades more expensive because the work is out of sequence and no funds are available in the contract amount. As a result, the upgrades aren’t done, performance is compromised, and call-backs are necessary.
Specification Reviews
Reviews of architectural specifications used for projects that have had building envelope failures generally disclose that some of the major components of the building envelope are not addressed. Typically, only the R-values of insulations and possibly a vapor retarder are specified, but air-sealing procedures, air-barrier materials, ventilation, and other vapor-control measures are left out. The inclusion and implementation of these important elements of the building envelope are left to the discretion of the general contractor and his sub-contractors. Common building practices are generally inadequate to prevent building failures at some scale in almost every structure and building performance rarely meets the potential that modern building materials could provide. This omission from the specifications of critical elements of a successful building envelope make it difficult for even the most responsible and knowledgeable contractors to include these measures in their bids because they can only afford to include what is specified due to the extremely competitive nature of the construction industry. For this reason, these critical elements are usually omitted from the construction. In addition, many special-use buildings require a knowledge of building science related to these structures. Most contractors are not aware of the specific details and methods required for difficult or severe indoor environments.
Keys to Success
Again, having good project specifications is only half of the battle. Confirming that buildings include all of the specified work assures that the Owner is receiving the intended value and performance of the design. If the contractor is held accountable for his work by regular reviews throughout the construction process, the proper installation of the materials that make the difference will be assured.
Performance Specification Reviews
Reviews of standard architectural specifications typically show that the specifications rarely include expected performance standards for the thermal envelope materials or the combined performance of component systems. Asking contractors to install building components in a manner that will achieve the desired performance is not unreasonable. In-place performance standards for other building systems (structural, duration, etc.) is routine and expected. Examples of performance specifications are readily available and well developed. Testing equipment used in the evaluation of building performance is not new and these services are also readily available. Increased use of performance standards could only serve to increase the availability and standardization of the documentation and procedures. Again, establishing performance standards is a low-cost element of the construction process and one of the few that has a short-term payback. Standardized specifications and industry familiarization with performance standards will keep up-front costs low, while dramatic savings in energy usage and all of the environmental implications provide the return on investment that any increase in design and construction costs create. Additionally, performance testing is a scientific process resulting in objective data that eliminates disputes over responsibility related to problems identified during the construction phase, reducing project delays and possible litigation.
Keys to Success
Having a good performance review process will result in an effective building envelope; however, standards must be achievable for a given building type or use. Some advance education may be required for the builder to understand how to achieve the standards without excessive costs due to a lack of an understanding of what level of effort is required to meet them. A pre-construction meeting to review the details and point out the likely areas where additional work (beyond normal construction practices) will result in successful performance testing results.
Quality Assurance Procedure Reviews
Reviews of standard architectural specifications typically show that the quality assurance sections only address the manufacture of the products to be incorporated into the thermal envelope, not their installation or the success of their in-place performance. Standardized specifications and industry familiarization with quality assurance procedures that measure performance will keep up-front costs low, while dramatic savings in energy usage and all of the environmental implications provide the return on investment that any increase in design and construction costs create. Additionally, problems not anticipated in the design or allowed by the construction process that may go undetected until the work is accepted and building failures occur will be identified before the construction process progresses to a point that it is too expensive to fine-tune the construction details. The testing process also provides a long-term benefit in that all of the parties will gain an understanding of how the building materials work together as a system and building designs and construction practices will improve throughout stages of the project and in each successive project.
Keys to Success
Verifying the performance of the thermal envelope systems through quality assurance testing will require advance planning so that the testing is incorporated into the construction sequence at the proper time(s). Waiting until the work has progressed beyond the point where low-cost touch-up of any missing or incomplete parts of the building envelope may result in expensive dismantling of finishes to access any problem areas.
Theoretical Considerations (excerpt from the Thermal VII paper)
The process outlined above requires two phases of testing and remediation work. In the first series of testing procedures (Phase I), only major conductive and air-leakage loss areas could be identified because the larger losses overwhelmed or “concealed” smaller ones. In the case of air leakage, large openings reduced the pressure differential across the barrier, and the smaller, more restricted openings had little or no flow. In conductive loss areas, large un-insulated sections of wall or roof concealed or reduced the apparent importance of relatively poor R-value areas. The initial (Phase I) testing gave an overall sense of the problem and determined that the primary causes of the ice formation were not failures in the insulation or ventilation systems in the cathedral roofs. It identified the areas requiring improvements and aided in prioritizing them. This procedure also provided a benchmark for comparative quality assurance procedures for the project.
After the Phase I improvements had been completed, the infrared and melt patterns in Phase II testing provided much more concise information about smaller, concentrated heat-loss sites. The pressure differential across the remaining small openings increased, allowing them to be easily detected. The second round of testing also gave the contractor making the improvements feedback about the initial round of work. Usually, this was done prior to closing access areas and replacing finishes. By incorporating a review step and fine-tuning into the planning, there was less pressure to address potentially low-payback repairs in the first phase, resulting in cost savings on several occasions. This also allowed everyone involved to assess the impact of the initial work, and to develop and try alternative techniques to overcome problems encountered in the first Phase. Creating a cooperative effort where everyone worked together to accomplish practical goals resulted in a much lower probability of failure. For all of these reasons, it was clearly important that at least two series of tests be performed.
