Abstract: This invention relates to a novel counter flow tube-manifold heat exchanger which can be installed in a wood or concrete floor and used to heat the floor and the earth space associated with the floor. A heat exchanger for conveying a heat containing fluid material in counter flow pattern comprising a hollow conduit comprised of three hollow elongated resillient fluid conducting tubes which are disposed parallel to and are joined to one another; and a first hollow elongated manifold with ports therein; and a second hollow elongated manifold, with ports therein adapted for connection with the ends of the tubes, the first ends of two of the three tubes being connected to the ports of the first manifold and the opposite ends of the same two tubes being connected to ports of the second manifolds, and the first end of the third tube adjacent the first ends of the two tubes being connected to a port of the second manifold, while the opposite end of the third tube is connected to a port of the first manifold.