Paper Poised to Fill New Gaps as Insulation: Mirrorpanel May Mitigate Foam Flaws

Buildings account for 40% of energy usage in the United States. In a world that stresses increased levels of responsible energy use, ensuring that new and existing construction is as efficient as possible will be vital to meeting our nation’s sustainability goals. Wood has long been the material of choice for framing, walls, and floors, but designers often fall back on conventional foam insulation to keep the heat in and the elements out. New research however, published in Forest Products Journal, introduces an insulation system that may help give forest products the green light to fill in new gaps.

A cutaway of a Mirrorpanel revealing its layered construction.

The article, co-written by FPL Supervisory Materials Research Engineer Samuel Zelinka, and FPL Research Physical Scientist Samuel Glass, proposes a new type of insulation called Mirrorpanel. Mirrorpanel takes advantage of the low thermal conductivity of still air, and is made of closely spaced layers of coated paper in a wood or fiberboard frame. It has been fabricated and tested at the laboratory, wall, and building scale and was found to perform as well as its foam counterpart — so well that it would even meet the stringent 2012 International Energy Conservation Code (IECC) for continuous insulation.

Adding to Mirrorpanel’s appeal is its comparatively small environmental footprint. Conventional foam insulation is made using fossil fuels, and can have up to 24 times the environmental impact of natural insulation materials like cellulose or cork. A paper-based insulation like Mirrorpanel would mitigate this energy usage, and could even be made from recycled materials or low-value woody biomass clogging our nation’s forests and increasing fire danger.

The test house constructed using Mirrorpanels.

Paper-based insulation is not a new development in the forest products industry. FPL’s own Research Demonstration House, constructed in 2001, is insulated with a blown-in cellulose product made of recycled newspapers. It is the layered construction, IECC compliance and thermal efficiency, and scalability of the panels which puts Mirrorpanel ahead of the pack.

Although Mirrorpanel has been tested in house-sized structures, researchers caution that further development is needed for it to become a viable insulation system. More testing needs to be done, especially in regards to its moisture-storage characteristics, and economic feasibility. With the rise of environmentally friendly commercial construction, Mirrorpanel should also be tested at even larger scales to ensure it meets the requirements of large energy-efficient commercial buildings.

It may not be ready for prime time yet, but ideas like Mirrorpanel represent a step in the right direction for insulation systems, and embody what research at FPL is all about — the latest scientific research, promoting the health and sustainability of our nation’s most valuable resources, for the betterment of the American people.

For more information, please see Thermal Insulation System Made of Wood and Paper for Use in Residential Construction

Weathering Walls : FPL Helps Buildings and Builders Breathe Easy

At the core of combating the cold in residential structures is effective insulation — but keeping warmer at home is not as simple as plastering as much polystyrene as possible to your walls and floors. Using more plastic insulation on exterior walls is a surefire way to increase the thermal efficiency of a building, but before you remodel, consider that you may be trapping more than just heat inside of your house.

Popular types of extruded and expanded polystyrene insulation have a much lower permeability than typical wooden building materials such as plywood and oriented strandboard. Because of this, exterior walls may become moisture traps, allowing moisture to enter, but not evaporate. This low-drying potential may lead to the mold growth, and in some cases, decay of walls made with these wood structural panels (WSPs). Unfortunately, little data exists on the real-world performance of these wall combinations, but researchers at the Forest Products Laboratory (FPL) are out to change this.


Wood structural panels (WSPs) are mainstays in residential and commercial construction.


FPL, in cooperation with APA – The Engineered Wood Association and Washington State University, has been studying the hydrothermal performances of walls constructed with WSPs since 2014. Performance testing in the Pacific Northwest was completed last last year, but data for cold climate zones, like FPL’s hometown of Madison, Wisconsin, is still being collected.

Researchers have constructed a “test hut” in Madison using wall assemblies with exterior continuous polystyrene insulation installed over WSPs. In this hut, they will investigate the potential for moisture accumulation and the drying capability of the walls during the colder months of the year.


The interior of the Chamber for Analytic Research on Wall Assemblies exposed to Simulated Weather (CARWASh) at FPL.


But FPL researchers don’t have to wait for the leaves to fall for the testing to begin. Using the on-site weathering chamber, the CARWASh, researchers will be able to run tests on individual wall sections in a computer-controlled and monitored environment. A total of 16 wall assemblies, each 4 feet wide and 7 feet tall, will be tested. Various combinations of water-resistive barriers, and exterior insulation will be used in the test walls, and the CARWASh will provide realistic weather perimeters and controlled water injections to simulate rain intrusion.

The test hut hygrothermal monitoring and CARWASh studies will be completed by July 2016, and the final report will be prepared by September.

With this data, WSP manufacturers will finally know how their products preform when the temperature goes down and the humidity goes up, and whether or not the permeability of the wood balances the impermeability of the insulation. Furthermore, as contractors make improvements to existing structures, and engineers design new buildings to comply with increasingly demanding energy-efficiency codes, they will have peace of mind thanks to FPL research — and breathe a little easier, knowing that their buildings will do the same.

For more information, see this Research in Progress report.

Insulation Guide Hopes to Comfort Engineers and Occupants Alike

If you haven’t been on a construction site lately, the word “insulation” will bring to mind one thing: long rolls of paper-backed pink fiberglass. This decades-old mainstay of residential construction is used in over 90% of homes in the United States, but it is not the only, nor the most efficient, type of insulation.

As the demand for high-efficiency building materials increases, engineers and contractors are looking for new ways of keeping the occupants of tomorrow’s buildings comfortable, and the existing buildings of today compliant with increasingly demanding codes.

One possible solution? High-efficiency foam insulation and wood structural panels. The problem in implementing these new technologies? The unknown.

A computer illustration of a 2x6 wall framing package.

A computer illustration of a 2×6 wall framing package.

Changes in building codes mean that existing buildings looking to improve their R-Value (a measure of an insulation’s efficiency) are left with two options: increase the cavity insulation, or add exterior insulation. Despite its ease of use and high performance, only 10% of homes use exterior rigid foam and insulated wood structural panels. Implementation of these new materials are limited by a lack of specific performance details and concerns over long-term moisture performance and hazard resistance.

The Forest Products Laboratory (FPL) hopes to answer some of these questions, and help bring high R-Value exterior foam and insulated wood structural panels into the mainstream. In cooperation with the Department of Energy’s Building America program and Home Innovation Research Labs, FPL researchers are working to assemble a Builder’s Guide to support a wider adoption of energy-efficient wall systems in residential construction.

The first edition will focus on two primary wall systems: 2×6 walls with optimized framing and 2×4 walls with exterior foam insulation. These two wall systems represent the best of adaptable, mainstream, energy-efficient options that use standard materials and require a minimal learning curve.

The guide, geared toward industry professionals, should be available in early 2016, and will contain advice for builders that can be readily implemented in the field using available methods and materials. The publication will cover everything from minimum code requirements and best practices, to 3-D graphics showing various construction options.

With this new guide, builders and engineers will have peace of mind about the performance of these new technologies and be armed with the knowledge to make informed decisions about these new insulation systems. Together, they will keep us all warmer in the winter, cooler in the summer, and reduce our energy requirements for the decades ahead.

For more information, please see the FPL Research in Progress publication Builder’s Guide to Energy-Efficient and Durable Wood-Frame Walls.