One of the most important aspects of construction implementation is the scheduling process. If done properly, it can save the owner and the general contractor a lot of time, money, and frustration. In many instances, however, this process is not monitored closely enough and can affect many aspects of the job. In large multi-million-dollar projects, the smallest mistakes in construction sequencing can be devastating to the project by causing costly delays, damages, and legal actions.
As an accredited NGBS Green Verifier, one of the biggest problems I see with scheduling for large projects is the building envelope not being waterproofed prior to the installation of interior materials. Often, different floors of a multi-story building are at different construction stages. The first floor may have drywall hung and painted and carpet and appliances installed, while the top floor isn’t even fully framed and doesn’t have windows installed. This can be a recipe for disaster. Rain water gets in through the top floors, seeps down through utility holes in the slabs, and gets behind the building wrap due to incomplete façade work. This kind of water infiltration can cause mold growth and other issues in tight buildings.
Air leakage in the building envelope is a major concern in green home construction. As a remedy, contractors use sealants and foam in all of the seams of the exterior skin. Some even use a plastic barrier on the inside as well, for a complete energy seal. This provides very low air leakage and optimizes the efficiency of the HVAC equipment. When these green practices are implemented, it is especially critical for the insulation and overall building cavity within the envelope to be completely dry prior to air sealing. When this does not occur, multi-story buildings may experience water from floors above leaking downward within the air sealed building, which can be costly to remedy.
On a large multi-story building I was inspecting recently, none of the exterior caulking was installed and the building wrap was not complete on the floors above. The contractor did not want to install the caulking until the brick façade was power washed. Then it rained … a lot. Because of the unfinished condition of the building wrap on upper floors, water was trapped within the envelope with no means of escape. The design of the exterior wall section included masonry, house wrap, fiberglass mat gypsum sheathing, metal studs, un-faced insulation, a plastic air barrier, and gypsum. The water was sealed within the heavily caulked and taped sheathing and the plastic air barrier, which, in turn, saturated the insulation. In some areas, the water filled up the cavity 6 to 12 inches off of the floor. To fix it, the contractor had to remove the plastic air barrier and all of the insulation. Then the area had to remain open for proper drying and new insulation had to be installed. That’s a lot of wasted time, materials, and money.
The construction sequencing for any building should involve the completion of the entire building envelope (weatherproofing) prior to any interior work that cannot withstand the elements. This may seem like a basic concept, but it gets overlooked in a lot of large projects due to fluctuating and often constricted timelines placed on the contractor. A lot of different variables can affect a project’s construction timeline, including issues related to funding/financing, seasonal adjustments, rental agreements, permits, or the timing of other projects.
For buildings seeking NGBS Green Certification, an NGBS Green Verifier must inspect numerous times during the multifamily building construction process to ensure each unit is inspected for all NGBS practices. Third-party inspections like these allow for potentially-damaging issues, like exposure to the elements and water damage, to be caught early and mitigated.
Home Innovation NGBS Green Verifiers can provide guidance up front to help trade contractors understand the potential issues associated with a tight building envelope and suggestions for improved construction scheduling. The moral of this tale, work with your verifier as early in the process as possible to avoid pitfalls. Third-party certifications provide quality assurance that high-performance building practices are implemented (and scheduled!) properly.
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