To understand how USG Sheetrock® Brand EcoSmart gypsum wallboard (GWB) has a better environmental footprint than many alternative wall coverings, it helps to know how it is made.
The key is two different gypsum crystals
The mineral gypsum comes in two different crystal forms: Calcium sulfate dihydrate (CaSO4 2H2O) is how the molecule is found in nature. Calcium sulfate hemihydrate (2 CaSo4 H2O) is created through a process of grinding and heating the calcium sulfate dihydrate molecules.
The first step in making GWB is to mine the gypsum dihydrate or collect it as flue-gas desulphurization from a coal-fired power plants. Step two is making the hemihydrate by grinding it and driving off water by heating it. The gypsum wallboard industry calls this material “stucco.” It’s a very fine powder, a lot like wheat flour in consistency.
If you take that incredibly fine powdered gypsum, mix in some key and proprietary additives, you can turn it into a slurry by rehydrating it with water. Adding water will move the crystal structure back to the dihydrate form, but in the process manufactures can form the recrystallizing dihydrate between two runs of paper to make gypsum wallboard (see the manufacturing diagram below).
In standard GWB manufacturing, about four times more water than required for recrystallization is added and a lot of energy is used to drive off that excess water. USG EcoSmart board uses special additives to reduce water use in the manufacturing process. The result is:
- GWB made using 25% less water
- 20% less CO2 emissions (reduced drying energy with less water in the board)
- 20% lighter board
- 20% less fuel consumption during transportation of the finished board
Why not make all board this way?
I asked USG this question and not surprisingly, the one downside to EcoSmart is cost. A USG representative told me that for ½-inch sheets of EcoSmart available at a big box store, there is a 10% to 15% premium. The EcoSmart premium is about half that for the 5/8-inch Type X EcoSmart board used throughout the commercial building industry.
The result is that ½-inch EcoSmart board has a pretty limited market share while the 5/8-inch Type X EcoSmart board is about 35% of USG’s Type X total sales. Clearly, the significantly better eco-footprint of EcoSmart GWB and its lighter weight labor savings is more important in the commercial building industry than the residential construction side.
And rumor has it that some Home Depot customers were even less tolerant of the EcoSmart premium because they thought that the “Eco” stood for economical not ecological.
EcoSmart board has solid “eco-cred”
BuildingGreen recently reviewed EcoSmart panels and stated this:
“Compared to standard drywall, EcoSmart has a better environmental profile, equal or better performance in most applications, and is cost competitive. It also has the following certifications and transparency documentation:
- Greenguard Gold certified for emissions
- Declare Red List Free
- LEED v4 compliant Type III EPD
- 1 Health Product Declaration
EcoSmart GWB also meets Architecture 2030 for products based on carbon emissions from manufacturing, according to USG.
Impact of less-dense board on acoustics and fire-resistance
It’s mass that largely deadens sound transfer in GWB and it’s the water in the dihydrate gypsum crystal that contributes quite a bit to GWB fire resistance (it takes a lot of energy to drive off the water in the gypsum crystal).
So, if EcoSmart board is 20% lighter or less dense, doesn’t that decrease acoustical and fire performance? I spoke with more than one technical representative at USG about these properties and was told that was “…the really challenging part of the EcoSmart formulation, but also the proprietary part. We have the test results to prove that EcoSmart board maintains acoustical and fire-resistance properties compared to standard GWB but we can’t give you the secret.”
Some industry perspective
I talked with Steve Rapoport, Territory Manager for Kamco Supply Corp in Williston, VT. They sell an awful lot of USG EcoSmart board. Steve was more than happy to connect me with some of his customers, drywall contractors using USG EcoSmart board. I caught up with Travis Dashnow of Hardrock Drywall of South Burlington.
“The only Type X board we use is USG EcoSmart,” Travis told me, “It’s the weight and quality of the board for us. We look for innovation in our work and EcoSmart’s reduced weight is a big deal.”
When I asked Dashnow about the price premium, he said, “More than happy to pay a bit more for this board—about 7% for us—and lift 20% less weight over the course of the day.” Dashnow went on to say that since USG Ecosmart can be used in place of the even heavier Type C ceiling board, it’s even easier for his company to stick solely with EcoSmart board.
I asked Travis if he ever sees EcoSmart board specified by architects because of its certifications or environmental performance. “We are starting to see this a bit in our work,” se replied, “but since we only use EcoSmart, it’s fine with us for architects to spec it.”
-Peter Yost is GBA’s technical director. He is also the founder of a consulting company in Brattleboro, Vermont, called Building-Wright. He routinely consults on the design and construction of both new homes and retrofit projects. He has been building, researching, teaching, writing, and consulting on high-performance homes for more than twenty years, and he’s been recognized as NAHB Educator of the Year. Do you have a building science puzzle? Contact Pete here.