Heat-pump heating unit

A building-interior heating system comprising a heat pump connected to heat the interior of a building and having a heat pump fluid for the transfer of heat and a static heat exchanger traversed by said fluid, said heat exchanger comprising a multiplicity of geometrically similar, planar, vertically spaced, horizontal heat exchange elements traversed by said fluid, means for connecting said elements together in a parallelopipedal stack with vertical sides at all of which gaps between the vertically spaced elements open freely onto wind-blown air, and means for mounting said stack externally of said building for uniform through-flow of wind-blown air from any compass direction freely through said sides of said stack wherein said elements are plates being free at said sides and secured in said stack by traction bolts and spacers, said heat exchanger being devoid of any air propelling fan means and relying entirely upon wind-blown air.