Abstract: There is provided a heat recovery ventilation unit comprising a first air flow path and a second air flow path and a heat exchanger in which the first air flow path is in heat exchange contact with the second air flow path; the unit further comprising an air flow path selector in the first air flow path which is arranged to select between the first air flow path and a third air flow path which bypasses the heat exchanger; wherein the air flow path selector is located between an inlet filter of the first air flow path and the heat exchanger. Providing the bypass selector between the filter and the heat exchanger, air is always filtered, even in the bypass mode, thus reducing particulate matter drawn into the building during bypass operation.

Abstract: There is provided a gas heat recovery unit comprising: two gas flow paths in heat exchange contact; a condensate drainage path for each of said two gas flow paths for draining condensate from the respective gas flow path, said two condensate drainage paths being fluidly connected to a common drainage outlet of the heat recovery unit; and each of said two condensate drainage paths comprising a valve which allows passage of liquid but not gas from the respective gas flow path towards the common drainage outlet. Providing a common drainage outlet simplifies installation and minimises the possibility of incorrect installation. It also permits switching the airflows within the unit without requiring any corresponding alteration to the drainage system.