Two-zone hydronic radiant heat question

Rick_88

When I built our house, I took the time to run pex tubing in my basement and under the ceramic tile of both my master bath and kitchen (both on ground level). I effectively used a "warmboard" style of installation of the pex above the basement for discussion purposes. I have big plans to integrate tankless and solar hot water heating later on, but for now I want to build the system with what I have right now, and that is a propane-fired 80-gallon hot water heater made by State . The home is currently heated with a heat-pump/electric back up heat/forced air. It would be nice to add warm floors as a comfort-only improvement (not really trying to heat the whole house with hydronic. I stepped into the hydronic world when I realized my basement was too large for those electric heat mats. I prepared a picture of my diagram for you to look at and attached it to this post.

Looking for lessons learned, what brands of components are considered ones you trust?

Last question, concerning tempering/mixing valves. Just before hot water from the heat exchanger hits the floor(s) return cooled water should get mixed in. But another convention is to to not use tempering valves in radiant floors but just spin the water through the floor and add hot water slowly to gently raise the temp of the floor until the thermostat is satisfied. If I intend to use a heat exchanger for both the basement slab AND the kitchen floor (kitchen needs to be warmer than basement I am told),
then how would I be able to ADD heat to both zones at different amounts if I am NOT using some type of mixing valve???