Developing a proof-of-concept non-scalable active vacuum insulated building envelope prototype

Abstract

Heating and cooling buildings consumes around 17% of global energy demand. Improved thermal insulation can reduce much of this consumption with positive implications for energy security and economic opportunity. For over 25 years vacuum insulation panels (VIPs) have been considered a highly promising thermal insulation solution for building envelopes. VIPs can potentially provide an order of magnitude greater insulative performance than common insulation materials with the same thickness. However, the adoption of VIPs in buildings is hindered by many factors: their relatively high costs, installation challenges due to fragility, inalterability, and limited dimensions; limited service life in comparison to buildings due to loss of vacuum over time; susceptibility to thermal bridging along their edges; and other issues. An innovative concept in vacuum insulation technology, active vacuum insulation, is being developed to address many of these challenges. Incorporating a connection to a vacuum pump enables use of cheaper materials and equipment for on-site assembly and evacuation of customizable, large (for example, a whole wall) active vacuum insulation panels (active-VIPs). Vacuum can be extended indefinitely through occasional reactivation of the vacuum pump. For the project described in this thesis, a proof-of-concept active vacuum insulated building envelope prototype was developed. Large active-VIPs were produced and integrated with a vacuum assembly that created, monitored, and maintained internal vacuum. Over a one month trial period an average pressure of about 68 mTorr was maintained and the average R-value per inch of the active-VIPs was around 50 hr∙ft2∙°F∕Btu∕in. This was achieved using a minimal amount of electrical energy for the vacuum pump, representing less than 5% of the thermal energy saved thanks to the vacuum pump. These results indicate that active vacuum insulation is a worthwhile innovation for continued investment in research and development.