In the first part of our series covering the new air barrier requirements for the 2020 VT CBES, we looked at the general requirements set forth, and the general paths to achieving whole-building air barrier compliance. Part 2 of this series took a deeper dive into the blower door pathway for compliance. What about this other pathway that avoids the blower door test, and instead requires commissioning? What does it entail and is it a simpler path to compliance? Part 3 of this series explores this in detail.
Does this compliance path require commissioning of just the air barrier or the entire building envelope?
A valid question because, to be honest, the code is a little misleading on this. This compliance path puts on a front that indicates commissioning of just a continuous air barrier (C402.4.1.2), but this path really encompasses all of the building envelope as it ties a much more elaborate full envelope commissioning checklist to the air barrier commissioning piece (C402.4.1.2.1).
What commissioning is required specifically for air barrier?
The code indicates that all that is needed for continuous air barrier commissioning (C402.4.1.2) is a final commissioning report, delivered to the building owner, that includes an inspection checklist and field inspection reports that outline the ‘what’ and ‘how’, respectively, of continuous air barrier installation. However, it isn’t clear if the checklist referenced here is the same checklist shown under C402.4.1.2 for full envelope, or if a separate checklist is intended. Knowing the potential for complexity in air barrier continuity, I imagine the intent is for a dedicated checklist. The code, however, doesn’t appear to define minimum checklist requirements beyond those which are spelled out under item 2 of C402.4.1.2 – proper material storage and handling, use of approved materials, and proper material/surface preparation, and continuity at envelope penetrations. Frankly, most of these should be contractor obligations regardless of air barrier compliance, so they don’t offer a lot of value to the checklist (not to mention most are big asks for anyone other than the GC/CM to monitor daily). A truly comprehensive air barrier checklist should focus on defining each significant air barrier system and transition details, the interfacing air barrier materials at said transition, and the quality of workmanship acceptable for that detail to be deemed continuous.
What does the full envelope commissioning checklist ask for then?
Compared to the dedicated requirements for air barrier commissioning, it asks for a lot, and since it is tied to the air barrier commissioning pathway, there isn’t any way around it. The commissioning process outlined in this checklist (C402.4.1.2.1) employs plan reviews, submittal reviews, site inspections, reports, etcetera, and not just for the air barrier, but it appears to be for all facets of the envelope. Think air, thermal, moisture, and vapor barriers. The list is relatively extensive and the types of items found within vary from structural installation compliance, to general envelope review, to code compliance verification. Some items contain a level of specificity that brings into question the extent to which certain services should go. For example, drawing and submittal reviews are required, but appear to only be necessary for exterior glazed window fenestration. This requirement isn’t seen under any of the other envelope systems/assemblies listed in the checklist. Another example – there is a requirement to meet OPR, BOD, and Cx specification requirements, but apparently only for “moisture envelopes”. Taken literally, this would mean the bulk water barrier. Why not also the thermal, air, and vapor barriers? We haven’t yet seen clarification for these kinds of items. One tip we can offer, which took us a while to pick up on is that where checklist items seem generally vague such as, “check ‘blank’ for requirements/compliance”, it is generally referring to checking compliance with, or requirements of, the code itself.
Who can provide commissioning?
The code states an “approved agency” shall commission the continuous air barrier (C402.1.2), which we now know “continuous air barrier” really means the building envelope. We reached out to the state for clarification on this and our understanding is that this is to mean an individual/group, or group of individuals, that is registered, licensed, or experienced to practice their design profession. It was written intentionally vague to not exclude individuals/groups, such as commissioning firms, that are experienced, but may not necessarily carry a design license/registration. The intent seems to indicate that someone, or some individuals, from the design team should carry the torch on the commissioning effort, whether it is the architect, engineer, or a 3rd party agency, or a combination.
When choosing who plays that role, there is something important to keep in mind here, and that is that there are some uncommon and time-intensive asks in this compliance path that some parties may not typically carry in their standard scope and fee. For example, C402.4.1.2 suggests reporting/inspections that verify proper material handling and storage, or the checklist in C402.4.1.2.1 which asks for structural anchoring sign off on structural systems and shading devices. Depending on who the Cx Agent is, they may not be on site every day to constantly monitor material handling and storage, and as an envelope commissioning agent, may not be versed in structural requirements. The latter example is one that also does not bring much, if any, value in regards to the commissioning of the air barrier/envelope.
All Clear as Mud?
Unlike the blower door compliance path, this commissioning compliance path isn’t easy to digest. There is no test requirement, but there are a lot more moving pieces, and with that, more questions and more up for interpretation. The requirements laid out, particularly those within the C402.4.1.2.1 checklist, seem to pool together responsibilities that are really a better fit for separate parties. The structural engineer of record would be a better fit to determine compliance of the structural systems. The builder is a better fit to verify proper material storage and handling on a daily basis, and to verify that each fenestration product delivered comes labeled with a National Fenestration Rating Council (NFRC) sticker that satisfies code requirements. So on and so forth. Why not utilize a dedicated envelope professional in a cost-effective manner, using their efforts where most valuable, and utilize other team members/resources to fulfill the other pieces of this pathway? After all, this compliance path is part of the self-certification process, which is facilitated through the forms and affidavits discussed in part 1 of this series. The trick is the final report to be submitted. Someone needs to take lead of assembling this report and collecting information from each team member to fill in the blanks, likely the architect, engineer, or commissioning agent.
Where is an envelope professional most valuable?
Above I suggested using a dedicated envelope professional where cost-effective. So where can an envelope commissioning professional provide the most value in the commissioning effort? We think the following is a good starting point and checks many of the boxes in the air barrier/envelope commissioning path to compliance:
- OPR and BOD review
- DD and CD design reviews
- Commissioning kick-off meeting
- Select submittal and shop drawing reviews
- Air barrier construction checklist development
- Periodic site visitation to review building envelope progress
- 1st instance air barrier fog test visits
- Ongoing issues log maintenance
- Final commissioning report
Food for Thought
Setting the code aside for a moment, we would be remiss if we didn’t mention that there is great benefit in providing both a commissioning effort and a final blower door test for any given project. The commissioning process provides opportunity to optimize the envelope during design and construction phases. Optimized for efficiency, continuity, and durability. The blower door test alone may confirm the fruits of the team’s labor, but doesn’t necessarily mean there aren’t outstanding air barrier deficiencies hidden behind finishes that could pose durability risks. Commissioning and testing go hand-in-hand, but per the code, only one of these two compliance paths is required. That said, if achieving a quantitative target through blower door testing path leaves you feeling uncertain, but so do the ambiguities of the commissioning path, then incorporate both into your project. You will have all of your bases covered for code, and the building will be better off for it.