A polished concrete floor figures prominently among the many “green” building features of a new addition to Da Vinci Arts Middle School in Portland, Ore., which could be one of the first—if not the first—school buildings in the U.S. to earn LEED Platinum certification from the U.S. Green Building Council (USGBC).
The Portland Public Schools district is seeking the LEED Platinum certification for a new, separate music-program building totaling 1,490 square feet: the Evans-Harvard High Performance Classroom. The building—winner of the Green Investment Fund grant from the city of Portland—houses the music classroom and practice space for the school’s band and music program.
A key sustainable-design element in the project was the passive heating and cooling system designed by SRG Partnership of Portland, said Project Architect Timothy Grinstead. The passive heating/cooling system significantly reduces the use of an HVAC unit.
Also contributing to reduced energy demand is the polished-concrete floor, produced using the FGS/PermaShine Polished Concrete Floor System from L&M Chemicals Inc. Such flooring is reported to absorb heat from the sun shining through skylights on cold days. During summer nights the skylights can be opened to allow cool air to lower the temperature of the exposed concrete slab and walls inside.
The PermaShine process involves the “dry” mechanical-grinding installation method, which can be used on new concrete floors or for concrete-surface restoration. The system starts with a dry diamond-grinding process, followed by collection of dust with a high-performance vacuum system.
After grinding, the floor is chemically hardened, or densified, with an odorless, non-toxic proprietary solution that chemically reacts with the calcium hydroxide and calcium carbonate in the concrete to form strong, durable calcium silicate hydrate (CSH), a crystalline formation that provides the concrete its strength and wear resistance. The densified concrete surface can be colored with dyes or stains, and is polished using finer-grit diamonds.
Concrete densifiers offered by L&M and other companies are typically based on sodium, potassium, and lithium silicates, magnesium fluorosilicates, or other proprietary silicate/siliconates.
Maintenance of the floor over its lifetime is described as relatively simple, and involves the use of a rapid-setting polyurea joint material and a concrete conditioner. The polyurea joint material prevents deterioration of unfilled joint edges, providing a clean and safe joint edge. The conditioner, used for routine maintenance, combines a degreaser, cleaning agent, and chemical hardening agent that reinforces the densified floor.
Jenci Bergen of Specialty Coatings in Portland, an installer certified by L&M Construction Chemicals, installed the exposed-aggregate floor system in the project.
In addition to energy conservation, the polished-concrete floor system can contribute to LEED credits for sourcing of regionally produced materials due to local production of cement used in concrete.
Polished concrete gets high marks as a green- and sustainable-building technology from the GreenSpec Directory, published by BuildingGreen.com, an influential, independent publishing company that researches and reports on green design and building methods and materials.
In an article published in the company’s Environmental Building News in 2006, BuildingGreen.com Executive Director Alex Wilson gave the polished-concrete method sustainability points for durability, UV resistance, ease of maintenance, and the concrete floor’s “structure as finish” condition, with no overlay, topping, or additional floor required. This gives the process the benefits of economics and reduced raw-materials consumption and waste disposal. Indoor air quality is marginally affected, if at all, by the zero- or low-VOC materials involved in the process.
Also contributing to the new school building’s LEED credits is the use of zero-VOC and very low-VOC paints and coatings. The products used include The Sherwin-Williams Company’s zero-VOC Harmony® water-borne acrylic paint, in primer, eggshell, and semigloss grades; the Pro Industrial Pro-Cryl® rust-inhibitive Universal Primer, with VOC content of 100 grams per liter; and Pro Industrial zero-VOC water-borne acrylic topcoat.
Indoor air quality credits under the LEED rating system require VOC content of 50 g/L for interior flat paint and coatings and 150 g/L for interior nonflat paints and coatings.
A sustainable-design showpiece
The DaVinci school building is billed as a sustainable-design prototype for the Portland Public Schools district, and the project team incorporated several other passive architectural design strategies. Extensive daylighting reduces energy used for lighting, increased insulation conserves more energy, and a photovoltaic array generates electric power.
Daylight enters the classroom through a large, central skylight, and is reflected onto the sloped ceilings and distributed evenly across the room.
Heating and cooling are provided by a highly efficient heat-recovery ventilator, and the building is “super insulated” and sealed against air leaks to reduce heat loss in colder weather and heat gain in the summer. The building-envelope system includes a vapor-permeable liquid-applied air barrier, Air Bloc 33, supplied by Henry Company. The material is a one-component elastomeric membrane that is reported to provide a UV-resistant, air and rain barrier. VOC content is low, at a maximum of 100 grams per liter.
(A PAINTSQUARE EXTRA from jacjournal.com, the Internet home of the Journal of Architectural Coatings).