When the former rock star Bob Geldof said the world could end by 2030 due to global warming, few people took him seriously. But for green building experts, the date certainly stood out: That’s the target year set for architect Edward Mazria’s well-publicized 2030 Challenge, to “achieve a dramatic reduction in climate-change-causing greenhouse gas emissions (GHG).”
Mazria’s plan inspired many architects and contractors to change “the way buildings and developments are constructed.” Many added more insulation to help cut energy use and create a carbon-neutral, low-GHG future.
The problem, say many, is that insulation alone is not enough. In fact, R-value is just one of a number of key issues.
Here are four more key envelope design issues that help reduce GHG emissions:
1. Dewpoint location. Where water vapor condenses at a given temperature is the dew point location. Too often, it’s situated at the stud insulation in a typical exterior wall. That means the insulation can get wet, sapping R-value and increasing the energy needed to heat or cool the building.
Here’s a solution: Use an insulated wall cladding, which can move the dew point outside of the wall. The result? According to Building Science Consulting from Westford, Mass. “With all of the insulation installed to the exterior of the structure, common problems of condensation within the structure are eliminated.” Instead, condensation occurs outside the wall’s drainage plane, so any moisture just drains away.
2. Thermal shock. Another key sustainable feature is preventing thermal shock, which is triggered by extreme temperature swings. The shock is sudden expansion or contraction of wall surfaces, which damages materials and reduces overall energy efficiency.
New products can protect against thermal shock. Thermally toughened glass is one example, as are rainscreens and double façades, which protect the insulating layer from excessive thermal change. Insulated claddings absorb sudden heating or cooling, protecting wall assemblies within. EIFS systems do the same, staying flexible and expanding or contracting as needed.
3. Thermal bridging. Any time a piece of metal extends through a building wall, it’s a short cut for heat loss or gain. That means squandered energy and a bigger carbon footprint. The worst offenders are steel columns or studs that are not protected by continuous insulation, or ci.
To deal with this, more buildings employ claddings with insulation installed outbound of the structure. “Continuous insulation not only provides its own insulating value, but also helps minimize thermal bridging across the studs,” says envelope specialist Sean M. O’Brien, P.E., of Simpson, Gumpertz & Heger. Eliminating thermal bridging can boost insulation effectiveness by 30 percent or more.
4. Weight matters. Using an insulated cladding system not only adds R-value – many are also lightweight systems, meaning less structural steel is needed to support them. This saves money and tons of steel, especially when the buildings are big. Smaller steel sections mean bigger floor-to-ceiling heights and interior spaces, too. Plus it takes less fuel – and less carbon – to transport the materials.
This kind of holistic thinking – less weight equals smaller carbon footprint – is central to meeting the 2030 Challenge. As Sara Hart wrote recently in Architectural Record, “Façades are no longer mere wrappers. They are another vital system that can improve or undermine the whole-building approach.”