Roof Energy Efficiency Looking Up

Few single elements have as big an impact on the energy efficiency of a structure as its roof.

John Letts, the Technical Director of Insulations in the Firestone Building Products’ Technology Department, does a very good job of describing the two major families of insulation at Faculty Executive.

The story, which posted this week, says that the older insulation is mineral wool based. It can be comprised of mineral fiber, rock wool, slag wool or stone wool. Slag wool is the most common. It is spun – the story says like cotton candy – with other ingredients. Polyiso (actually, polyisocyanurate) is used in more than 70 percent of commercial roof construction. It originally was used as insulation for beer barrels.

The story compares the two: They both have outstanding fire retardant properties. Mineral wool can be 4.5 times heavier than polyiso and therefore finds more use in walls than roofs. Polyiso is the stronger of the two. There are some concerns about the safety of materials used to tie mineral wool fibers together, Letts wrote.

The desire to more creatively use daylight is increasing demand for glass roofs. The Architectural Record posted a piece sponsored by 475 High Performance Building Supply that points to potential advantages in health, happiness and productivity of people in glass-roofed structures. Very often, however, the story says that poor design ends up leading to the opposite result: Buildings are too hot in summer, too cold in winter, tend to have leaky and are liable to sun glare that is visually disruptive.

The story provides five tips for those considering glass roofs. The most important is to ensure that standards related to preventing leaks are followed and that a way to provide continuous maintenance is built in. The roofs must be designed with the comfort of the people within as the primary goal. The third suggestion is to design systems that prevent condensation. The fourth idea is to make sure that the roof fits into the overall energy balance of the building envelope. The final idea is a bit open-ended. Designers, the story says, should be open to myriad options that are available.

Research continues. Last week, the University of Colorado website posted a story on a project by researchers at the school on metamaterials – which it defines as engineered materials containing elements not found in nature – that can cool the object it is covering by reflecting solar energy. It eliminates heat that builds up within the material itself without heating what is underneath.

The story quotes one of the researchers:

“Just 10 to 20 square meters of this material on the rooftop could nicely cool down a single-family house in summer,” said Gang Tan, an associate professor in the University of Wyoming’s Department of Civil and Architectural Engineering and a co-author of the paper.

Roofs clearly are a big topic for energy manager, both as structures are designed and in their ongoing maintenance.

 

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