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Need to re-do the radiant heat in new-to-me house.

Short story: Log home with baseboard hot water in the basement and radiant floor heat on 1st floor(and two baseboard radiators in the great room along with the radiant floor).

All of the bedrooms are on one side of the house on a single hallway. The only heat in this area is radiant floor under plywood/carpet. I went through an entire tank of heating oil in less than a month before I realized that the thermostat was never being satisfied because the just place a few random loops of pex in the joist spaces and thought that would do it. So in 4 rooms and a hallway, there are 5 warm spots. Thats it. I'm going to install all new pex, properly, in the joist spaces in the summer.

This is a closed system with a separate electric water heater for domestic. The heating water is supplied by an oil boiler. I have no confidence in the previous homeowner's abilities as everything that was DIY was done wrong and has had to be redone by me.

My question is: what would be the suggested temperature for the boiler? It is currently sending out 185F. The visible pex tubing is a orange/red/brown color rather than the red it obviously was when it was new. Kind of looks to me to be discolored due to overheating.



  • Jamie Hall
    Jamie Hall Member Posts: 23,297
    Have you calculated the actual heat loss on a room by room basis? That's the place to start with any heating system -- but particularly with radiant.

    That will tell you two things: can you, in fact, heat the rooms with radiant, and how the radiant needs to be designed.

    I rather expect that you will need to redo the whole radiant system. While they aren't all that hard to do, they are sufficiently sensitive to design that there is something to be said for having professional help, at least for the design stages.

    I might point out that carpet makes pretty good insulation -- radiant floors under carpet are not really that good an idea. Under isolated throw rugs, no problem.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gordy
    Gordy Member Posts: 9,546
    Of this is a full log home infiltration is enemy number 1.

    As been said you need to do an accurate heatloss with particular detail to infiltration, even suggest a blower door test.

    A proper radiant design could do it need to know the loads first.

    Existing system sounds like it had baseboard originally, and radiant was added, and run at the same water temp as baseboard. Over the top radiant methods require lower water temps than under floor.