My system doesn't seem to be working well. It was about 8 degrees out last night and my system would only temp house to 66 degrees. I put mixing valve up to 145 supply with 130 return and my floors are temping at about 79 degrees. They feel fine but the air feels chilly. Any suggestions? Should I run an additional loop on the outside walls? I ran 7/8 pex with plates 8" apart except on the 10 ft extension. I ran continous plates, alumin shield, and then insulated. Should I raise the mix more?? I have all hardwood floors 3/4 with 3/4 tongue and groove wood subfloor. On the extension I have 3/4 plywood subfloor. All newly insulated house.

79 floor surface temp... you don't want to go much higher than that. Might be able to squeeze a couple more degrees out of the floor, but you'll be pushing the floors fairly hard. If you can add heat elsewhere, do it, your floors will thank you.

Or, perhaps you have drafts that you could seal up?

Sounds like someone borked your heat load/floor load calculations, or your construction is leakier than expected.

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Northeast Radiant Technology, LLC
-=RFH Design, Supply and Consultation=-
RPA certified Radiant Designer
http://www.NRTradiant.com
rob@NRTradiant.com