This paper describes the design of a simple guarded hot-plate apparatus for the measurement of heat transfer across transparent insulation. The apparatus is used to measure the heat transfer coefficient across a transparent corrugated (zigzag) sheet and honeycomb transparent insulation. The sheet and honeycomb are made from cellulose acetate film, which has high absorptance for long-wave thermal radiation and high transmittance for short-wave solar radiation. The corrugated sheet performs well, however, honeycomb transparent insulation of the same height and material appears to be superior due to greater thermal radiation blockage and better solar transmission characteristics. A numerical model for a honeycomb is developed which shows good agreement with the experimentally measured results. (C) 2003 Elsevier Ltd. All rights reserved.