Inadequate insulation is one of the largest causes of wasted energy, quickly allowing comfortable heating or cooling to disperse air outside.
That’s why researchers at the U.S. Dept. of Energy (DOE)’s Oak Ridge National Laboratory (ORNL) are collaborating with industry to develop a high-performance material that nearly doubles the performance of traditional insulators without a high cost premium.
“Buildings are responsible for 40% or more of the energy consumption in the U.S.,” says Kaushik Biswas of ORNL’s Building Envelopes Group. “There’s a huge opportunity to save energy.”
More specifically, about 6% of the entire U.S. energy consumption, which includes the building, industrial and transportation sectors, can be attributed to the energy used by heating and cooling equipment in compensating for heat transfer through opaque sections of building roofs and walls, Biswas says.
In residential and commercial buildings, roofs and walls are buffered with insulation to prevent heating and cooling losses. But the lower the insulation performance, the more heat is lost during winter or gained during summer and the more often a heating or air-conditioning unit will have to start up.
“Insulation is important because you want to reduce heat transfer between indoors and outdoors,” Biswas says, adding, “You want your AC or heating unit running as little as possible to keep your home cool during summer and warm during winter.”
Commercial buildings commonly use polyisocyanurate, or polyiso, foam boards, while many residential structures are insulated with spray foam. Compared with the product ORNL is developing with partners NanoPore and Firestone Building Products, these materials have low “R-values”—the measure of heat transfer through an insulation material.
The material being developed by ORNL and its partners is a composite polyiso foam board containing “modified atmosphere insulation,” or “MAI,” cores. While polyiso and spray foam hover around an R-value of 6 per inch, the goal for MAI-polyiso composites is 12.
“With what we are targeting, you can get a similar R-value in half the thickness,” Biswas said, adding, “What we want to do is get a new insulation product that’s cost effective and achieves R-12 per inch.”
To reach the increased R-value, MAI technology borrows from the design of vacuum insulation panels (VIPs), which display some of the highest R-values but are expensive to produce because of steps in the current manufacturing process. To make MAIs more viable, NanoPore changed how they’re made and knocked off about half the cost.
MAI panels are made of a porous core measured in terms of molecules that is evacuated and sealed within multiple barrier layers. The nanoporous structure and vacuum within the MAI cores help to reduce two out of the three modes of heat transfer in insulation materials: solid conduction and gas/vapor conduction. The third mode of heat transfer, radiation, can be reduced by adding opacifiers to the core, which can potentially further increase the R-value.
Truly separating MAIs from VIPs, however, is the manufacturing process. Almost 75% of the cost for VIPs is bundled up in the processing and overhead stages. But MAI manufacturing cuts out around half the price by reducing the processing steps and eliminating the need for much of the specialized equipment used in making VIPs.
Unlike VIPs, the vacuum in MAI panels is produced by filling the porous core with a condensable vapor, which then condenses to liquid that occupies a fraction of its original volume, leaving the remaining space a vacuum. Further, the MAI sealing process is comparable to that used in sealing potato chip bags.
“NanoPore fundamentally changed the manufacturing process for MAIs,” Biswas said.
While NanoPore has a grip on constructing MAIs and ORNL on testing the product, Firestone Building Products is developing a composite that uses polyiso foam to encapsulate the MAI cores. An added advantage of the new composite is that it allows MAIs to be integrated into buildings without any special installation considerations. For instance, the new MAI-polyiso composite will be a drop-in replacement for existing polyiso boards.
Additionally, following preliminary research, Biswas said the ORNL team and industry partners are confident that an R-value of 12 per inch is reasonable and can be reached. And with its high R-value and cheaper cost than VIPs, MAI’s are shaping up to be a promising alternative to current insulators.
“Development of next generation insulation materials achieving R-10 to 12 per inch can lead to substantial energy savings in the buildings sector,” Biswas said. “Modified atmosphere insulation is a lower cost alternative to vacuum insulation panels and is a good candidate for next-generation insulation materials.”
Source: Oak Ridge National Laboratory