Getting up to speed with Air Sealing Details

Article 103 of the 2009 International Energy Conservation Code (IECC) requires that construction documents include air sealing details. Detailing the building envelope air barrier is a relatively recent challenge for architects, but it is a necessary task for communicating these fussy requirements to builders. The details of laps, connections, splices, and transitions of these thin membranes and tapes are especially important considering the potential downside of an unintended hole in an otherwise tight building envelope. With increased attention to energy conservation and air tightness of the building envelope, a small hole - like a pin hole in a balloon - can wreak havoc in terms of heat loss, vapor transmission, condensation, and moisture damage to construction materials that are concealed from view.

Some architects - already tuned in to our responsibility for construction drawings that show how building materials and products meet and connect with one another - have taken up this challenge by developing a sheet or sheets of details that show typical air sealing conditions that apply to their buildings. Instead of burying this information in other details where it may be hard to read due to the thinness of the air sealing materials, they have developed details specific to the air sealing materials, showing laps and transitions within the air barrier system and at transitions and terminations where the air barrier must connect with other building components like flashings, doors, and windows. Necessary details may include full-size views and exploded views to effectively show proper lapping and isometric views to effectively illustrate 3-dimensional shapes and connections. The details should be designed to effectively communicate the air sealing requirements.

Rethinking the Cost of Time

Building design and construction have been governed in modern history by our perception of time as a cost-based commodity. Both design and construction are assumed to have greater competitive value if production time is minimized. The first cost is generally lower if it takes less time to design and build a project. We can recognize an inverse relationship between first cost and long term cost when we consider building products (e.g., cheap windows vs. expensive windows), where lowest first cost may lead to higher long term costs in energy usage, maintenance, and replacement. Yet, as a profession and an industry, we have not been able or willing to recognize the long term value of time invested in design and construction, such that more available time (if well managed) results in more integrated attention to systems and details that enhance long term building performance and optimize long term operating costs. This issue is most notable in our continuing willingness to commit to abbreviated time periods for design and construction. We talk about the value of high performance buildings in terms of energy efficiency and healthful environments, yet the market continues to demand speed over performance due largely to the long established premise that "time is money" - a premise that is reinforced by the owner who wants the building quicker and by the designer and contractor who must bid low to get the job and then minimize time in order to avoid loss. When minimizing time is the highest priority, long term performance may suffer. Owners, designers, and contractors need to rethink the cost (and focus) of design and construction time as they relate to long term building performance. We have come to recognize long term risks associated with fast food; fast design and construction deserve similar consideration.

Breaking Ground with New Consultants

It can take a few projects to work out the communication kinks with a team of consultants. Consultants who have worked together and with the same team are likely to develop a good understanding of what to expect from other team members: learned and, perhaps, unwritten protocols about information exchange - what to expect and when, and what you have to request. A new consultant may bring both the promise of talent and the risk of problems related to communication. The challenge for both architects and consultants is to spend enough up-front time talking about who will do what and how and when information will be exchanged. It's better to consider your assumptions about what the other party will do and openly discuss details that may otherwise seem too mundane for review, especially if the scope of work is critical to timely project coordination and completion. While a formal consulting agreement may already be in place with an established scope of work and schedule, the details related to scope execution and coordination are not always covered in such an agreement.

Consultants bring not only different talents but also different ways of thinking, so it is best to reach an early understanding about the expectations of each party.

Interdisciplinary Coordination of Construction Documents

Gaps between design disciplines are a common cause of construction change orders. In some cases, the consulting disciplines' standard practices may generate a gap. For example, the electrical engineer may establish an electrical scope of work that "stops" 10 feet outside the building, while the site civil engineer may expect (and indicate on the site drawings) that the electrical contractor will provide power to a sewage lift station that is 15 feet outside the building. Unfortunately, it is quite possible that neither the electrical engineer nor the civil engineer will become aware of this gap in electrical service until the contractor submits an RFI.

Similar gaps can occur between plumbing and site trades, between mechanical and general building trades, between structural steel and miscellaneous metals trades, and between other trades. In most cases, proactive coordination by the project architect during the construction documents phase can help to minimize these gaps."Proactive" coordination means getting involved in finding and highlighting possible gaps and managing document revisions to eliminate the gaps by conferring with the related disciplines, considering applicable trade practices and regulations, and assigning responsibility to the most appropriate party. (It's usually not enough (and not really proactive) to simply tell the consultants to work it out between themselves.)

A Catch 22 Product Specification

Specifications occasionally include unintended contradictions, and in some instances they are related to schedule.

Not long ago, I reviewed a specification for roofing that included a requirement for a particular "ice and water shield" product and allowed no substitutions. The application requirements for the product included a minimum ambient temperature of 40 degrees F. That looked good from a quality control perspective, but the schedule for this fast-track, multi-building project in snow country required construction during the winter, when temperatures were expected to be well below 40 degrees F, and neither the schedule nor the budget allowed for temporary tenting and heating of whole buildings. As a result, in order to meet the schedule, the contractor had to apply the product under conditions that were not recommended by the manufacturer and were not in compliance with the specification.