Demonstration and Cost Analysis of a Building Retrofit Using High-Performance Insulation
Mr. Tapan Patel | USACE ERDC-CERL
Objectives of the Demonstration
The Department of Energy (DOE) estimates that in 2010, 15.6 quads of primary energy consumption was attributable to fenestration and opaque building envelope components of all U.S. buildings, including Department of Defense (DoD) Facilities, of which the wall-related primary energy consumption was about 21%, or 3.3 quads (USDOE 2004). For commercial facilities, primary energy consumption attributed to walls during heating cycles was 1.48 quads, or ~30% of total energy consumption due to building envelope components. Heat loss through walls during a heating cycle is a critical component of overall facility energy use and mitigation measures are important to reduce total facility energy consumption.
This project demonstrated and validated the use of modified atmosphere insulation (MAI) to reduce wall-related energy consumption in DoD facilities. MAI can significantly increase the thermal resistance of walls with only a marginal increase in wall thickness, thereby reducing wall-related energy consumption. By retrofitting walls and increasing their thermal resistance (R-value) by R10-20 (hours-feet squared-degrees Fahrenheit per British thermal unit [h-ft2-°F/Btu]), reductions of 30% or more over the baseline wall-generated space conditioning loads are possible (greater savings are achievable with buildings of older vintage or those that are poorly insulated). A combination of facility sensors and modeling activities was used to determine the effectiveness of the MAI.
The Performance Objectives (POs) that were met are:
- Reduce facility energy usage by 4.0% compared to the baseline energy usage of the building. The actual reduction was 6.43%.
- Reduce electrical demand by 2.0% compared to the baseline demand. The actual reduction was 3.5%.
- Minimize MAI panel vacuum loss to less than 5%. Only 3.3% of the MAI panels failed.
- Increase overall R-value of envelope to R-13.8/in. The R-value was increased by R-15.2/in.
- Achieve 70% coverage of wall area with MAI panels. The project achieved 76% coverage.
- Reduce energy loss through walls by 20% or more. The project achieved a 31% reduction in energy losses through walls.
- Achieve (qualitative) user satisfaction of 90% or more. The project achieved 100% user satisfaction.
The following performance objective (PO) was not met: Achieve a simple payback of 33.1 years with a Savings to Investment Ratio (SIR) of 0.62. The project demonstrated a simple payback of 198 years with an SIR of 0.13. The high simple payback and low SIR is because the facility already contained insulation. For a facility without existing insulation, the simple payback and SIR would be 28 years and 0.83, respectively. Additional cost reductions in manufacturing and installation are expected to improve these economics.
NanoPore Inc., working in conjunction with the DOE’s Building Technology Program and Oak Ridge National Laboratory (ORNL), is developing a new generation of advanced thermal insulation with the same performance as silica-based vacuum insulation panels (VIPs) but significantly reduced costs. The new insulation technology is called MAI. Vacuum insulation is the only technology that promises a step-change in performance (R40/inch [in.]) compared to conventional insulation materials that achieve up to R6-7/in. VIPs consist of an evacuated core material (usually fumed silica) with a microporous structure. The core material is encapsulated within a barrier film and sealed under vacuum. This project will specifically test the cost and performance of MAIs. Numerous studies related to VIPs in buildings can be found in the literature, but those related to actual building applications are few
(USDOE 2004; Tenpierik, Cauberg, and Thorsell 2007; Brunner and Simmler 2008; Cho, Hong, and Seo 2014). ORNL and industry partners evaluated an exterior insulation and finish system that contained VIPs (Childs et al. 2013); combined experimental testing and numerical analysis indicated that whole-wall R-values of R30 h-ft2-̊F/Btu or higher were achievable using 3-in.-thick foam-VIP composites.
This demonstration retrofitted a ~2,000 ft2 facility at Fort Drum with MAI and facility sensors including temperature, heat flux, electric, and natural gas. A similar facility was not retrofitted but was outfitted with identical sensors. By comparing the differences in measured data, and by using modeling to account for load/occupancy discrepancies across the two buildings, the energy and cost performance metrics were calculated.
Results from the demonstration show that the MAI technology can significantly reduce heat flows across the facility walls. This results in energy and electrical demand reduction. Infrared (IR) images discovered some failed panels, which were likely damaged during the retrofit process. No degradation of the panel (after installation) was observed. Although the system economics are not favorable for this demonstration, the economics are expected to significantly improve for new or minimally insulated existing buildings and with additional reduction in MAI manufacturing and installation cost.
A majority of the implementation issues were discovered during the installation process. These issues included: (1) replacing J-channels and siding around windows required additional effort, (2) modification and replacement of soffit vents was not adequately anticipated, and (3) construction glue was not needed to hold the MAI panels in place temporarily (the clearance between the foam strips and the MAI panels was small enough that the panels were held in place by friction). These findings are discussed in additional detail in the final report. Additional issues include the relatively intensive installation process. Future efforts are aimed to reduce installation time by creating large 4x8-ft integrated boards. These boards will combine MAI panels and polyisocyanurate foam in a matrix, which is expected to reduce installation time by 80%. The team also found that further careful handling is required during the installation process to reduce the damage to panels.