A heating or cooling assembly includes a plurality of modules 2a, 2b of thermal storage blocks articulated together by releasable connection 6,8 so that the assembly can be manipulated by a user to adopt a desired profile. The releasable connection comprises complementary engagement profiles on adjacent modules. At least one of the modules contains a thermal store in the form of a solid, liquid or gel that has a high specific heat capacity to cool or heat a pet housing for a period of time. The thermal store may be pre-heated or pre-cooled or may comprise a phase change material that releases heat when crystallization is initiated. The assembly may be used for heating or cooling a hutch or small domesticated animal housing.
