Alternative Methods for Preheating Outdoor Ventilation Air

In the pursuit of energy efficiency one has developed a complex technology of earth-air heat exchangers (EAHX). In this process, one discovered some drawbacks such as possible entry of radon gas or high humidity in the shoulder seasons. Elsewhere, we highlighted that when the outdoor temperature changes frequently, one needs using two different air intake sources with an automatic selection of the one more appropriate for the actual weather conditions. In winter, the EAHX may be used continually but in the other seasons, the selection should be performed by a steering/ control system. In this paper examined two nearly identical EAHX systems placed in the soil next to the building or under the basement slab. While there is an advantage in the under house placement, yet the advent of integrated system design permits replacing the EAHX by different heat exchangers located in the mechanical room (as it was done in a case study in NY) or in the exterior wall. In the latter case we propose an alternative system that permits using different ventilation patterns in summer and winter.