Abstract: A prefabricated ventilating panel including heat transfer means is disclosed for supplying air to an enclosure, including a vertical core member formed of heat insulating a material, a vertical outer facing member formed of heat conductive material arranged in parallel spaced relation to said core member, means defining at least one vertical passage between said outer facing and core members, air inlet means for supplying air to the lower end of said vertical passage, and generally horizontal passage means connected at one end with the upper end of the vertical passage and extending horizontally through the core member. Consequently, air introduced via the inlet opening flows upwardly through the vertical passage in heat transfer relation with the outer facing member and through the horizontal passage means for discharge into the enclosure. Damper means are provided for alternately connecting the horizontal passage means with the vertical passage and with a by-pass air opening, respectively.