Water, Water Everywhere . . .
- By Amy Milshtein
- July 1st, 2007
A thin skin, your building’s envelope, separates outside from in. This barrier between your students and the outside world keeps out cold, heat, rain, and wind. Build the envelope too loosely, and those elements find their way in. Construct it too tightly, and mold may become a dreaded reality. How are today’s school planners treading this tightrope, and what new green innovations are on the horizon?
Case Studies: Ohio and Denver
The state of Ohio, which is in the middle of a $5-billion project to rebuild or renovate all of their 3,000 school buildings, created the 2,400-pageOhio School Design Manual to address all aspects of school design.Everything is in here from whether you should renovate or build new to how to choose furniture, reports Franklin Brown, planning director Ohio School Facilities Commission.
Brown admits that since there is little agreement among people on which solution is the best solution to building design, this document sets a standard and controls the architecture. Envelope design is quite specific. The wall must be 14 in. thick, says Brown. Once above grade, those 14 in. translates into four in. of brick veneer, two in. of air space fitted with rigid board insulation, and then eight in. of concrete. That exterior sits nicely on the 14-in. concrete block footing.
The two inches of air space proves most important for keeping water from migrating in. So important, in fact, that some people want to increase wall size to 16 in., adding the extra two in. to the air space. Sometimes the mason can drip motor into that space giving water a bridge to travel on, explains Brown. The extra two in. would compensate for human error.
Even with that extra air space, a vapor retarder still needs to be installed between the concrete and the insulation. Once called a vapor barrier the word retarder is used to acknowledge that water still makes it in. The retarder has to be on the warm side of the insulation, reminds Brown.
Weep holes let water out of the building. Old strategies like putting hemp in the mortar of every other brick course have been replaced with high tech tubing. These square-celled tubes let water out but don’t allow bugs in. I’ve seen lots of buildings constructed in the 1960s that had no weep holes at all, says Brown. That’s a bad idea. In fact a lot of the buildings built in the ‘60s and ‘70s seem to be self destructing.
Trena Deane, interim executive director and Kenneth Montoya, foreman, protective coatings department, at the Denver (CO) School System know a thing or two about buildings and water. We manage 150 buildings, and many of them are under a historic mandate, reports Deane. That means lots of old brick and mortar. Moisture moves into those walls pretty easily.
Compounding the problems in these historic buildings are the old-fashioned plaster walls on the interior. In fact, Deane and Montoya estimate that 50 percent of their structures have plaster somewhere in them. Plaster really holds onto that moisture, tells Montoya. Then the mold takes over.
To prevent seepage as best they can, the Denver school district employs six painters to spray water-based waterproofing agents on the masonry exterior. The agents soak in and protect fairly well, but Montoya speaks to the constant battle between shrinking public school budgets, which doesn’t allow us to spray all the square footage we would like to. We also have a graffiti problem and the chemical that removes the graffiti removes the waterproofing agent as well.
When there has been a breach, wet plaster must be addressed. We cut a hole in the plaster and set up a fan to dry it. That takes quite a while, because the plaster holds water so efficiently, reports Montoya. After the plaster dries, a hazardous waste specialist tests for mold. Once the space gets an all clear the wall is treated with specialized anti-bacterial paint. Then comes the hard part... replastering. Working with plaster is a dying art, Montoya laments. I keep trying to encourage the younger guys to take it up.
Top It Off
The roof remains one of the most obvious places to repel water. Large leaks, the kind that require a pan to catch the drips, are rare. It’s the slow leaks, the ones that are not immediately noticeable that present a problem, says Jim Sheltmire, senior manager, Soprema, Inc. These allow water to seep in, letting mold and mildew grow and damaging the structure.
Roof maintenance hasn’t changed much over the years. Annual inspection is a must, insists Sheltmire. If you suspect students or other unwanted guests are walking on your roof, you should schedule twice-yearly inspections. Things to look for include: obvious membrane tears, vegetation growth, and plugged drains.
What has changed, however, is everyone’s environmental awareness including roof manufacturers. Traditional roofing is a fairly invasive procedure — from the kind of products that are used, to the VOCs those products put out, to where those products ultimately end up, says Sheltmire. Today we are responding to architects’, roofers’ and building owners’ desires to be greener.
One way Sheltmire and his company have responded is with a magnesium oxide slurry or MOS. This bonding agent contains no solvents, occurs naturally in nature so it is biodegradable, and is odorless and not toxic. Many K-12 schools want LEED certification or at least some of the LEED principals integrated into their schools, says Sheltmire. MOS is an environmentally conscious, inexpensive option. It’s cheap chic.
When people think of green roofs they often think of vegetated roofs. These planted roofs have been around in Europe for a long time and are just catching on in the US. They retain heat in the winter, keep cool in the summer, release oxygen into the air and slow water flow into storm drains. A new mixed planting matrix means the roof can be lighter and installed on metal structures. Yet vegetated roofs remain in their infancy here. I don’t see us moving to a vegetated roof any time soon, says Brown. A white roof sure but not a planted one.
Case Closed Cell
One new technology that Brown and his Ohio School Facilities Commission are looking into is closed-cell insulation for their cold-line pipes and ductwork. Closed-cell materials fight mold and mildew on cold-line pipes by not allowing moisture to wick through. Since there is no food source, mold can’t grow. It also remains more efficient — every one percent moisture gain in insulating material translates into a 7.5 percent loss in thermal efficiency.
Closed-cell insulation also proves valuable inside ducts. It’s a smooth surface with a skin so dust is inhibited from collecting. What does accumulate can be easily removed, says Mike Resetar, technical manager North America Insulation Products, Armacell LLC.
Closed-cell technology also has the advantage of being fiber free. While this is not a big selling point for Brown, I know people are afraid of fibers, but we are more attracted to the materials’ cleanability, it was a huge asset in the renovation of Cumberland Valley High School in Mechanicsburg, PA. The school district just endured a decade of asbestos cleanup. We’ve spent upwards of $2M in asbestos removal, says Lee Brandt, a construction rep for Cumberland Valley School District. So despite conflicting reports on fibers in the airstream, this school district wanted to go entirely fiber free.
This decision, however, comes at a price. It’s definitely more costly, says Resetar, about 1.5 times more expensive than traditional fiberglass.