I dont know why you would need glycol if you keep the water circulating even if it is going through a water heater set at a low temp. Going through a water heater ia a good soultion if you only need to take off the chill and to help out with the load on the main system. I think you might be suprised how well it heats provided you are insulated well,
Glenn

Glenn
Life is not about being dealt a great hand but how Great you play the one you were dealt!