Restoration of historic buildings is tricky business. Among other challenges, preservation concerns severely limit façade alterations.
Restoration often includes deep energy retrofits which generally increase the thermal resistance (R-value) of the envelope. For existing structures adding insulation to the exterior is generally preferred over the interior as adding insulation from the inside will reduce its floor area. But for historic structures this approach is self-defeating.
Vacuum insulation has been used widely in non-building applications like refrigerators, thermos containers, and thermal doors. Its use in building envelope insulation is fairly new and still in R&D. Vacuum Insulated Panels (VIPs) are composed of two stainless steel plates which sandwich a core of vacuum and fumed silica.
Get on your way to green.