We have generated models of complete nova energy distributions, including the effects of the nova dust shell emission and absorption. In order to account for the dust, we require optical constants throughout the UV and EUV. Draine & Lee (1984) is the only source of such data for silicates. However, their ‘astronomical silicate’ has a strong resonance in the UV which causes circumnova dust to be heated far above its sublimation temperature in our models of Nova Her 1991. We have therefore recalculated the silicate optical constants, using the Kramers-Kronig relations, including a λ−1.0 far-IR dependence and improved 9.7μm feature, and decreasing the UV and EUV efficiencies of the grains. With these new silicate constants we can reproduce the observed behaviour of the dust shell in Nova Her 1991. Since our optical constants are consistent with the behaviour of Nova Her 1991, an EUV source, they should also be appropriate for the treatment of PN.