Besides aluminium heat exchangers the Dutch company Holmak now produces also air-to-air heat exchangers made of high-quality PET material. The PET plastic plates have a long operating life and high standards of hygiene as well. The heat exchangers TST 15, 25 and 35 reach thermal efficiencies up to 95 % at lowest pressure drops. This allows the classification of a heat recovery ventilation unit in energy category A+ regarding the European norm EN 13141 (2015) which is valid from 2016 and specifies the test requirements for home ventilation systems. The so-called “eco-label” means classifications concerning the energy efficiency ranging from top marks like A+ to minimum values such as G.  
Holmak produces plastic heat exchangers with lengths from 200 to 700 mm in Staphorst, the Netherlands. The plastic plate heat exchangers from Holmak are based on the counterflow principle. When separate supply and return air flows pass each other in opposite directions (counterflow principle), the air in one channel can heat up or cool down the air in the other channel by means of thin plastic plates.

Image 1: Plastic heat exchangers TST 15, 25 and 35 from Holmak