For cool roofs the combined effect of the three parameters that define heat gain and loss from a roof, namely solar albedo α, thermal emittance E, and sub-roof R-value must be considered. An accurate contribution of night sky cooling, and hence humidity and total down-welling atmospheric radiation is needed. A systematic analysis of the contribution of a roof to average cooling load per day and to peak load reductions is presented for a temperate climate zone over six cooling months using an hour-by-hour analysis. Eighteen 3-parameter sets (α, E, R) demonstrate the overriding importance of a high α, while sensitivity to R-value and E drops away as albedo rises. Up-front cost per unit reductions in peak demand or average energy use per day always rises strongly as R rises unless albedo is low. A moderate R~ 1.63 is superior to high R unless a roof is dark, or winter heating demand is high. We indicate briefly why the roof is typically not at present a dominant influence on average winter heating needs in most temperate zones, enhancing the benefits of cool roofs.

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The shape memory (SM) capabilities of nanocomposites based on two photocurable acrylated/methacrylated resins, doped with carbon nanotubes (CNTs), and manufactured by digital light processing 3D printing were investigated. The mechanical properties and glass transition temperature (T g ) can be tailored in a broad range by varying the weight ratio of the two resins (T g ranging from 15 to 190 °C; Young's modulus from 1.5 to 2500 MPa). Shape fixity (S F ) and recovery (S R ) ratios are strongly influenced by the temperature being significantly higher at temperatures close to the T g . The results confirm that the S F strongly depends on the stiffness of chain segments between cross-linking points, whereas the S R mainly depends on the cross-link density of the network. CNT addition barely affects the S F and S R in the conventional oven, whereas the recovery speed using IR heating is significantly increased for the doped nanocomposites due to their higher IR absorbance.

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