I am designing my home for Western Washington state. 2400 sq. ft. 1-level, slab-on-grade, house with hydronic in-floor heat and no cooling. Heat loses in the house come out to 22000 btu/hr in the winter. I'd like to use a 3 ton geothermal water-to-water to give me room for DHW. Read about Desuperheaters, which are great for summer A/C waste heat, but are less of a great thing in the winter. It's not an expensive add on, but I was wondering if anyone has just heated a DHW preheater tank (that supplies tankless DHW heaters) off the manifold that feeds the in-floor tubes? I would still have a buffer tank between the geothermal unit and the floor manifold to limit cycling.