Hidden Costs of Building Green
Donald E. Smith, CCS
November 2009An interesting question came across my desk the other day that caused a bit of a quandary, and with all of the emphasis on green building and LEED® certification, I am sure some of you will also find yourself scratching your head as to what to do. The question had to do with storing drywall on site. So what is the big deal?
Here’s the situation. The building is closed in and the HVAC system is up and running. The general contractor asked the drywall contractor to cover the drywall stored on site with plastic. This is a big job. There is approximately 1,775,000 square feet of drywall in three buildings with a total square footage of 639,000 square feet. The drywall contractor, an AWCI member, is on site hanging board. So why worry about protecting the board?
This project is going for LEED certification. In the LEED-NC Version 2.2 Reference Guide there is a requirement for a Construction IAQ Management Plan, and its "during construction” component is worth a credit of 1 point. The following is from the reference guide:
"Intent. Reduce indoor air quality problems resulting from the construction/renovation process in order to help sustain the comfort and well-being of construction workers and building occupants.
"Requirements. Develop and implement an Indoor Air quality Management Plan for the construction and pre-occupancy phases of the building as follows:
"During construction meet or exceed the recommended control Measures of the Sheet Metal and Air Conditioning Contractors national Association (SMACNA) IAQ guidelines for Occupied Building under Construction 1995, chapter.
"Protect stored on-site or installed absorptive materials from moisture damage.
"If permanently installed air handlers are used during construction, filtration media with a Minimum Efficiency.”
So now we understand why the protection requirement exists. The problem here is that the general contractor used the page from the Reference Guide as his IAQ Management Plan. He did not develop a specific plan in his own words. The instructions to the drywall contractor were to cover the stacks of drywall with plastic sheeting. Not a problem, right? Let’s take a look at what the Gypsum Association has to say about storage of gypsum board on a job site. The following is a direct quote from GA-801-07:
"Exposure of gypsum panel products to rain and other high moisture levels may result in water stains, discoloration, mold, paper delamination, and sag. This sensitivity of most gypsum panel products to adverse moisture conditions requires that gypsum panel products NOT be stored outdoors without complete protection from the weather.
"The plastic covering provided for product protection during shipment on rail flatcars or flatbed trucks is not suitable for storage of the gypsum panels and shall be removed upon arrival at the destination prior to warehouse storage. Failure to remove this plastic covering can result in damage to the gypsum panels due to moisture, condensation, wet product, and/or mold.
"The Gypsum Association does not recommend outside storage of gypsum panel products.”
Needless to say, the reason for removing the plastic cover used for shipping drywall is that moisture will form on the underside of the plastic, which is also the side on the drywall, and cause damage to the drywall. So to comply with the LEED requirement, just how do we protect the drywall? It is apparent that the general contractor did not investigate the type of covering required, nor did he specify the correct material. The information in the LEED Reference Guide is not of much help either when it comes to selecting the correct type of covering to protect the drywall. Since the building is closed in and the HVAC system is operational, the likelihood of the drywall being damaged by high humidity is nil. However, there is the possibility of water being spilled on the gypsum board by other trades.
The solution I offered after consulting with some sources in the gypsum industry was to use a water-resistive barrier like Tyvek. This material has some water resistance and it is also breathable, thereby eliminating condensation on the side next to the gypsum board. The protective material should not come in contact with the gypsum board, use gypsum rippers or touch the floor. I believe this would comply with the LEED requirements for protection of the gypsum board.
But the big rub for the project in question is the additional cost involved in providing protection for three building totaling 639,000 square feet. That amounts to a lot of stacks of drywall waiting to be hung and needing protection. Also, the size of the pieces of protective covering needs to be adjusted at the end of each day depending on the amount of drywall used in any given location. This could translate to one person per building uncovering the stacks of drywall prior to work commencing and then returning at the end of the day after work has ended. Just another hidden cost in the pursuit of building green.
Donald E. Smith, CCS, is AWCI’s director of technical services. Send your questions to firstname.lastname@example.org or call him directly at (703) 538.1611.