This paper reports the experimental and theoretical evaluation of various heat exchange phenomena that occur in a vacuum insulation panel (VIP). Fumed silica and a range of IR-opacifiers were mixed in different proportions to identify the best composition that yields minimum thermal conductivity value at ambient and evacuated conditions. Three variants of carbon black (CB) and one each of silicon carbide (SiC) and titania (TiO2) were employed as opacifiers. Of all tested, CB was found to be the best opacifier based on the detailed experimental FTIR investigations performed whereby specific extinction was measured for each composition. To demonstrate the performance of the optimised samples of core materials developed four VIPs were manufactured which achieved a significantly low overall VIP thermal conductivity of <4 mW m(-1) K-1 (R-value >36.03 ft(2) degrees F h/BTU in.) measured using guarded hot plate apparatus. With these thermal conductivity values the samples perform much better than most state of the art commercially offered VIPs. (C) 2015 Elsevier B.V. All rights reserved.