Volume 17, Number 3, September 2012
The introduction of the 2011 National Energy Code of Canada for Buildings has created an opportunity for manufacturers to come up with innovative solutions in building envelope construction. The Code aims to achieve 25% less energy use in buildings than the energy code requirements set in 1997, and provides a fresh impetus to the construction industry’s search for the next generation of energy-efficient insulating materials.
A promising type of high-performance thermal insulation currently being considered for exterior building envelope construction is the Vacuum Insulation Panel (VIP). VIPs can be 10 times more thermally efficient than conventional thermal insulation materials (see figure above).
Building envelopes in North America have a service life of 25 to 50 years or more. Thus, long-term performance is an important parameter in the selection and design of VIPs as an insulation material. At present VIPs are available from Asian, European and North American manufacturers. They come with a wide range of choices in terms of R-value per inch, size (length × width × thickness) and shape. However, there exists very little credible information about the long-term or aged thermal performance of these available VIPs.
The primary reason for VIP aging is loss of vacuum (i.e., increase of pressure). The loss of vacuum is caused by gas or vapour permeation through barrier or sealed barrier joints.
Laboratory aging of 20 VIP specimens for nearly seven years shows that the maximum recorded reduction (loss of R-Value) is about 19% and the minimum is about 10% during the period. The average is around 13% (i.e., slightly less than 2% per year).
There is no evidence of thermal performance degradation of VIPs installed in the NRC Construction Test Hut Wall (see above photos) during 18 months of field exposure. Accelerated aging tests conducted on five different VIP products (total 15 specimens) – from different manufacturers, of various sizes, and with diverse compositions – show insignificant aging (about 5%) in 4 out of 5 products and failure in 2 out of 15 specimens.
The results from laboratory aging, field aging and accelerated aging studies clearly indicate promising long-term performance prospects for most of the VIPs available in the marketplace. However, the results also highlight the need to define long-term thermal resistance values for VIPs and to develop technical criteria and quality control processes for identification of VIPs that are suitable for building envelope construction with a service life 25 to 50 years.
Researchers at NRC Construction are working with industry and global partners to address these issues to accelerate the adoption of VIPs in high-performance and Arctic building constructions.
For more information
Contact Phalguni Mukhopadhyaya at 613-993-9600 or email@example.com.