A protective enclosure for equipment located outside, such as, for example pipeline and wellhead valves, includes a plurality of modular panels that are releasably connectable to form the enclosure into a configuration necessary to enclose and protect the equipment from the weather. The modular panels are metal structural panels having a rigid foam core to provide a desired level of insulation rating to the enclosure. In embodiments, the modular panels are configured to be assembled into one or more of a roof assembly, a gable assembly, and one or more sidewall assemblies. Assembly securing members attach the various modular panels together in a manner so as to prevent separation in a plurality of directions.