Performance is crucial for insulation. “Superinsulation” and continuous insulation (abbreviated “ci”) across the entire envelope are critical elements of highly sustainable and net-zero projects, says Perkins+Will’s Cillian Collins. Green roofs, living walls, and some rainscreen enclosures offer a variety of insulating and environmental qualities.
Mineral wool, which is highly fire resistant, can also be effective, says SmithGroupJJR’s Andrew Dunlap. Wiss, Janney, Elstner’s Fiona Aldous mentions phase-change materials, super-thick insulation, and high-performance insulating blankets with R-values exceeding nine per inch of thickness.
The latest trend, says Aldous, is to ensure that the exterior wall assembly complies with continuous insulation requirements (where required) and NFPA 285, the IBC-mandated testing of combustible envelope material assemblies, including foam plastic insulation and certain water-resistive barriers.
Aldous says that even the best-designed envelopes can be undermined by thermal bridging in areas where insulation is deficient. She recommends the following:
• Determine how much insulation is needed, and how to install it properly.
• Evaluate the insulation’s permeability and the risk of creating an unintended vapor barrier.
• Locate the insulation correctly within the wall assembly.
• Use insulation to manage vapor movement or air leakage (or both).
• Minimize thermal bridges.
• Meet continuous insulation (ci) requirements.
• Comply with NFPA 285.
The choice of the correct insulation should be more than a rush to the highest available R-value. The products selected must contribute to a system that controls the flow of air, heat, vapor, and water. Older buildings’ envelopes, which may be leakier and less insulated, at least have a good potential for drying; the tighter, high-R-value envelopes in favor today allow very little thermal flow. So if there is bulk water intrusion or vapor/air leakage, moisture can remain in the envelope long enough to lead to mold, corrosion, and dry rot.
There are many options for envelope insulation. Fiberglass, rock wool, and slag wool have been used for decades, but now there’s rigid board, cellulose, and foam insulation, as well as cotton, wool, and hemp.
Hemp insulation (which was just recently allowed in the U.S.) comes from a renewable resource and is biodegradable and breathable, according to building enclosure experts. Hemp has good sound absorption, resists mold and bugs, and is stiffer than many other fiber insulations, so it doesn’t slump after it’s installed.
Slumping and movement following installation can be a problem, so passive designers have been looking to building materials that have insulation built into the material’s structure, such as structural insulated panels (SIPs), insulating concrete forms (ICFs), and insulated metal panels (IMPs). Polystyrene or polyurethane foams are major components of these prefabricated systems.
Another option: vacuum-insulated panels filled with aerogels. These so-called “VIPs” are panels with fumed silica or fibrous layers with nanopores. Some enclosure experts say they can enhance design flexibility, as they are thinner than some other insulations.
According to the USDOE Oak Ridge National Laboratory, open-cell aerogels are 90% or more air by volume and offer “unique physical properties, including the highest thermal resistivity, the highest specific surface area, the lowest density, the lowest refractive index, and the lowest dielectric constant of all solid materials.”
The dominant specs for insulation are plastics, some of which contain recycled content. Plastic foam board and spray-applied materials perform well as envelope insulation, both above and below grade.
Related Stories
| Nov 4, 2013
New DOE code changes require improved energy efficiency in commercial construction
Outsulation by Dryvit incorporates continuous insulation and a seamless air/water-resistive barrier, which meets new code requirements
| Oct 15, 2013
Sustainable design trends in windows, doors and door hardware [AIA course]
Architects and fenestration experts are looking for windows and doors for their projects that emphasize speed to the project site, a fair price, resilient and sustainable performance, and no callbacks.
| Oct 7, 2013
Nation's first glass curtain wall exterior restored in San Francisco
The Hallidie Building's glass-and-steel skin is generally recognized as the forerunner of today’s curtain wall facilities.
| Oct 7, 2013
10 award-winning metal building projects
The FDNY Fireboat Firehouse in New York and the Cirrus Logic Building in Austin, Texas, are among nine projects named winners of the 2013 Chairman’s Award by the Metal Construction Association for outstanding design and construction.
| Oct 4, 2013
Sydney to get world's tallest 'living' façade
The One Central Park Tower development consists of two, 380-foot-tall towers covered in a series of living walls and vertical gardens that will extend the full height of the buildings.
| Sep 24, 2013
8 grand green roofs (and walls)
A dramatic interior green wall at Drexel University and a massive, 4.4-acre vegetated roof at the Kauffman Performing Arts Center in Kansas City are among the projects honored in the 2013 Green Roof and Wall Awards of Excellence.
Sponsored | | Sep 23, 2013
Nichiha USA panels provide cost savings for community project
When tasked with the design and development of a newly constructed Gateway Rehabilitation Center, architects at Rothschild Doyno Collaborative first designed the new center to include metal panels. When the numbers came back, they were challenged with finding a product that would help cut costs and keep them within the construction budget. Nichiha’s fiber cement panels come in a half or less of the metal panel cost.
| Sep 20, 2013
Perimeter roof edge: The first line of defense in a wind event [AIA course]
Aside from the roof membrane itself, the perimeter roof edge is the most critical component of the roofing system. As such, it warrants more scrutiny when designing a roof system.
| Sep 15, 2013
How to build a rainscreen using fiber cement panels - AIA/CEU course
This course will review the cause and effects of moisture intrusion and explain how fiber cement panels can be used as a rain screen to reduce moisture build-up, rotting interior walls, and mold growth.
| Sep 13, 2013
Video: Arup offers tour of world's first algae-powered building
Dubbed BIQ house, the building features a bright green façade consisting of hollow glass panels filled with algae and water.