Walls, Ceilings and Learning Environments
- By Michael Fickes
- July 1st, 2010
What do walls and ceilings have to do with creating a good learning environment in K-12 schools? Aren’t these building systems simply supposed to look pleasant?
As it turns out, they contribute quite a bit to a school’s learning environment. First, walls and ceilings hide the inside of the exterior wall and any problems developing with the building envelope. Two examples: Leaks in the roof or exterior wall and waterproofing materials installed to protect against leaks can lead to water damage, rust, erosion and mold. Second, insulation failure can cause temperatures to rise too high or fall too low, making the environment uncomfortable for learning and expensive for a school district heat and air condition.
Then there are the ceiling materials like acoustical tiles that control the transmission of noise with rough surfaces that diffuse sound waves and help prevent sounds from one room infiltrating into neighboring rooms. Insulation also plays a role in acoustical control by diffusing sounds coming through the exterior from, say, the traffic noise on the roads that run past the school.
Water: Keep Out
First things first: “Water is, by far, the biggest enemy of a school building,” says Dennis Hacker, AIA, LEED AP, a specification writer in the Dublin offices of Salina, Ohio-based Fanning Howey Associates, Inc. “It can come in through the roof and ceiling, the exterior and interior walls, the basement walls and the floor. When it does, it causes mold, rust and other kinds of damage.”
Today’s top-of-mind water problem is mold, continues Hacker. Mold lives and grows in the same temperatures as people. There is nothing you can do about mold from the point of view of temperature. It is also difficult to eliminate the organic materials, such as paper and wood that feed mold.
The only effective way to stop mold is to eliminate water from leaks, condensation in areas behind the walls and above the ceilings and in air with too much humidity — as a rule, mold begins to grow within 72 hours when humidity persists at 65 percent or higher.
Waterproofing or damp proofing below ground and above ground is the second line of defense against encroaching water and moisture — after the exterior walls and roof. “You should waterproof any building feature that goes below grade,” Hacker says. “Such features include orchestra pits, a sunken reading area in the library and the basement.”
Groundwater creates hydrostatic pressure that spreads water out. Underground building systems close to the water table need to be waterproofed. “The unusual thing about waterproofing below ground walls is that, unlike the roof, you have to get it right the first time,” Hacker observes. “You can always patch the roof. But it will be very expensive to repair the waterproofing behind a basement wall.”
In other words, waterproofing materials must be durable and zero-maintenance.
Waterproofing materials come in the form of self-adhering sheets and sprays. The sheets can bridge over cracks, notes Hacker. They resist chemical intrusion and even have self-healing properties. Self-adhering sheets do not adhere well to rough surfaces. Sprays do.
“The important thing is to look at the track record of the waterproofing product you choose,” Hacker says. “Whatever you do, don’t choose a new material. Choose proven materials.
“You also want to make sure that waterproofing materials and their installation form complete systems that the installer will warrant.”
If there is no water pressure in the ground surrounding the structure, the goal becomes damp proofing. Damp proof membranes (DPMs), thick polyethylene sheets, lie under floor slabs and connect to damp-proof courses (DPCs) that protect walls from moisture. Structures with cavities between exterior and interior walls typically use a DPC on the inside of the exterior wall and the exterior of the interior wall.
Water in the air is another factor, says Michael E. Stobak, a vice president with the Barton Malow Company in Southfield, Mich., a construction management firm with many K-12 school projects to its credit. “Usually, temperatures differ substantially between the inside and outside of a building, and that leads to condensation,” he says. “This is where condensation occurs.”
So it makes sense to consider interior materials that can resist the ill effects of water and help to prevent mold formation.
Ceiling tile manufacturers have added new lines to help deal with moisture, too. “We are addressing moisture problems with cellular PVC ceiling panels,” says Rob Larson, director of operations with Acoustic Ceiling Products of Appleton, Wis.
The term cellular refers to the panel design. Instead of solid and rigid, the panels are made with cells or spaces inside. Larson says it is a manufacturing method that uses less material but yields a stronger product.
To the point of interior environmental quality, the PVC materials won’t absorb water and so will resist mold and mildew formation.
Do PVC ceiling tiles sacrifice the noise diffusion properties of conventional ceiling tile? “To some extent, yes,” says Hacker. “But manufacturers also design and make these products in various textures that help with acoustics. We’re learning to use other materials — wall hangings and soft furnishings to help control noise.
The PVC ceiling panels help prevent moisture damage, and their smoother, less acoustical surfaces promote environmental quality in other ways. Hacker points to the emphasis on natural daylighting in schools today and offers that architects are using the smoother plastic mold and moisture resistant ceiling tiles to help enhance the benefits of natural light by reflecting it into areas that it might not reach on its own.
Finally, Hacker points out that buildings particularly susceptible to moisture and mold problems might benefit from applications of anti-microbial agents on the materials used to construct the walls and ceilings.
Not Too Hot, Not Too Cold
Insulation behind the walls and above the ceiling helps to maintain temperatures at comfortable levels, despite the thinner walls made possible by modern steel construction.
“Architects used to rely on the mass of stone walls to insulate against heat and cold,” Hacker says. “With the advent of steel, they could design slender walls. That drove down building costs, but now we need insulation.”
R-values measure how well materials resist heat transmission — how long does it take for the heat on two sides of a barrier to equalize, continues Hacker, who recommends selecting materials with the highest affordable R-value appropriate to the application.
For instance, blanket (or fiberglass) insulation can fill space between studs in a wall and also provide acoustical benefits by diffusing outdoor sounds — like traffic noise from a highway. On the other hand, the blanket insulation doesn’t cover the metal studs that can transmit cold. “Insulating is always a matter of calculating the trade-offs,” Hacker says.
Masonry walls require different insulation because they typically offer no cavities for insulating blankets. Extruded polystyrene board may work better for these walls. “We’re increasingly using polyurethane spray foam,” adds Hacker. “You can spray it anywhere and make it thick. Its benefits include working as a vapor retardant. Then again, it is a foam, and its fire properties may make it inappropriate for schools.”
Walls, ceilings, waterproofing and insulating materials play important roles in supporting the quality of a school building’s indoor environmental quality. Walls, ceilings and insulation help to maintain comfortable temperatures for lower utility costs than heating and air-conditioning systems can provide on their own.
Waterproofing and damp proofing materials above the ceiling and behind the walls can prevent moisture from doing its worst to degrade materials and produce mold.
Over time, ceiling panels have evolved away from conventional acoustical tile materials to help combat mold and distribute natural light, leaving the acoustical work of diffusing noise for other materials to handle.
All told, these new materials and techniques contribute as much to the learning environment of K-12 schools as the components of building envelopes.