Part 3—Project Phases

MOISTURE MANAGEMENT ACROSS THE PROJECT PHASES

It is tempting to assume that the building enclosure will work perfectly and water won’t get where it doesn’t belong. Such a belief can lead to a lack of risk mitigation from a very likely hazard (water) throughout the useful life of the building. A more realistic mindset is—moisture intrusion cannot be completely avoided, it must be managed. Enclosures should be designed and installed not only to keep out bulk water and drain it away, but also to manage incidental water with minimal long-term impact. The key is for the enclosure design to have a greater capacity for drying than its risk of wetting.¹⁵

This moisture durability assessment looks at six primary categories for an enclosure. Roughly working across the project life-cycle, they are shown in Figure 5, starting at the bottom:

Figure 5. Moisture durability elements and assessment project life-cycle details.

There are a number of aspects to manage moisture risks in this phase that green building rating systems can address. Below is a brief summary of the elements highlighted in this assessment:

Material Selection

The material selection phase can start early in the project process. It can often carry over into a firm master specification, or even be dictated as a line-item budget before the schematic concept is complete. Improving material selection can include above-code specification requirements, such as exceeding minimums for attachments and roof edges, dedicated air barriers, and material properties like solar reflectivity. Single-sourced manufacturer systems for building enclosures don’t mean only specifying one manufacturer per product, but it does mean to consider the bids for all components within an enclosure system, like a roof, and their ability to properly integrate with adjoining systems. In a roof system, all of the components such as the membrane, cover board, insulation, air/vapor retarder, and structural deck are tested by third parties as a system, and should really be specified as a system, not separately. Coordinated manufacturer systems can be key to installed performance, such as prior system testing and single-source responsibility for future service and repair. Third-party product certifications, such as HPDs and EPDs, can be useful in the product selection process for green building ratings, but unless the product certification addresses performance in specific applications, it may not address moisture durability.

Design & Procurement

In the design and procurement phase, project teams solidify design decisions and look for unexpected building-system interactions. When it comes to designing an enclosure, the overall system performance becomes really important, such as expected resistance to anticipated extreme weather events and clarifying the expected enclosure system service life. Rather than relying on heuristics and rules of thumb for long-term moisture performance of the building enclosure, performing a moisture analysis can identify areas where “tight-coupling” of moisture mechanisms may be occurring in the building. Specifically, performing ASHRAE 160 Hygrothermal analysis early in the design process allows the outcomes to inform the project team.^4,12 Also, engaging professionals for third-party reviews with specific expertise in moisture risk mitigation is important. These can be consultant constructability reviews, manufacturer reviews for conformance with the published requirements, and contractor shop drawing reviews across the enclosure systems.

The inclusion of performance testing can lower the risks related to moisture durability. When these tests are specified with defined pass/fail criteria, the project team is able to vet out performance at the intersection of design and construction. Potential risks, including air and water leaks, are identified early and are able to be addressed before the building is occupied.

Construction Activities

In the construction phase, project teams are bringing designs to reality. During the lengthy process of construction, moisture has a direct opportunity to find its way into areas where it was never intended. To protect the building and the integrity of the enclosure, a temporary moisture protection plan is important. The plan should include measures for material storage and specifications for in-process protection while the enclosure systems, like roofs, are being applied across many weeks or months. When installing materials onsite, rather than in a controlled environment, it is important to identify that conditions are appropriate to proceed. Qualifying the site conditions can be performed by substrate acceptance testing such as adhesion tests, compatibility qualification, and fastener withdrawal resistance methods. Whether it's a system-based verification, or specific third-party auditors, like ABAA Quality Assurance Program (QAP)¹ or the IIBEC Registered Roof Observer (RRO)⁹ programs, having a third-party quality assurance program, aside from the GC’s quality control, can also contribute to managing moisture risks.

Performance Testing

When performance testing is required, it’s important that the owner’s expectations are taken into account early in the design and carried through to the trades in the field. The point of performance testing is not to make buildings “fail” after they‘re built, but to ensure the constructed building meets the initial minimum performance targets set out by the owner and design team when they started the project. A whole building airtightness test is a good example of this. It doesn’t attempt to “over-pressurize” the building, but to uniformly pressurize the enclosure to identify inconsistencies in the overall construction. Stopping these air leaks can enable the mechanical systems to perform as designed during the use-phase of the building, limiting leakage and potential occupant discomfort. Testing can also be performed on a smaller scale with field mockup and sample tests. These can be useful to establish acceptable installation and sequencing methods onsite and provide representative results, rather than the expense of comprehensive testing. Another set of moisture durability tests are integrity and moisture detection testing, such as infrared scans, electronic leak detection (ELD), or nuclear moisture surveys. These can be useful to demonstrate a moisture protection plan was successfully implemented—that there is no concealed moisture, and that systems are continuous where they are intended to manage rain, like in a roof or waterproofing system and at interfaces.

Operation & Maintenance

It’s important to begin recognizing the operational challenges early in the design phase. This could be in terms of future assessments using climate projections, such as an increase in the intensity of rainstorms, and understanding how the project can adapt for changed uses at the end of the building’s expected life, such as capturing rainwater for irrigation. After the completion of the building, and beginning the use-phase, installed systems training is important for occupants and facility managers on the expected operation of enclosure systems, such as the clearing of roof drains and the maintenance requirements associated with rooftop solar. Use-phase training can also include the hand-off of warranties and guarantees from the construction process to the building operators. This is important because it can help inform facility management of ongoing inspection schedules and long-term maintenance contracts necessary to meet the initial design expectations. Like most things, roofs and enclosure systems need to be maintained, and service contracts can be a critical part of scheduling and performing inspections to ensure that long-term guarantees aren’t voided.

Building Enclosure Commissioning

Building Enclosure Commissioning (BECx) isn’t a separate project phase like the previous elements. BECx is a holistic process that starts in pre-design and continues through to the use-phase of the completed building.⁵ Along the way, the commissioning process can manage moisture risks by identifying “system complexities” and assist a project team to take steps to manage the “tight coupling” of the enclosure and related systems. As part of the project team and across the project phases, BECx can coordinate with the Owner’s Performance Requirements (OPR) through documentation reviews, installation observations, guiding performance testing, and establishing the on-going commissioning plan for the enclosure. When incorporated into the project, BECx can be a great tool to manage moisture durability and the associated risks.