Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

radiant heat in room over a crawlspace

donedeal Member Posts: 36
I recently bought a house. It has a bath/laundry room addition that is above a crawl space. This is room is significantly colder than the rest of the house. I have gas fired hydro radiant heat throughout the house including that room. That room and the basement which is partially finished (minus the crawl space ) are on their own manifold and thermostat. The basement is warm enough so I turned the return valve off on the basement and so only hot water is directed to the bathroom on the ground floor above the unheated crawl space on the other side of the basement. Is that in issue? In terms of putting too much strain on the circulator? Is that more efficient? I have noted that the circulator makes a whining high pitched noise when first turns on and then fades after a couple minutes. The pex tubes are hot on the supply and warm on the return side entering that room through the crawlspace.

Now that it's cold the boiler is constantly running to try and heat the bathroom but the temp drops throughout the night despite its best efforts. I added a space heater to help but that's even less efficient. What is the most efficient way to run this? How else can I warm it up? The insulation is installed upside down with vapor barrier facing the unheated side. I have plans to fix this but is this just a moisture issue or is it losing heat this way ?

We had an energy audit done and there was minimal draft in that room, but it does have 3 exposed walls and because it was an addition there is insulation on the fourth wall separating from main house.


  • donedeal
    donedeal Member Posts: 36
    also- i'm wondering if it's a thermostat issue? My tstat when pulled off the wall only has 2 wires going into it Red and White, which connect downstairs to a track box zone with two inputs. There is no additional wires. The other zones are on a tstats that have 3 wires. What is the 3rd wire and where does it connect to because it's not going to the track box?
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    The 3rd wire usually is "common" and is used for powered thermostats with no batteries. Older mercury thermostats were all 2-wire (basically a thermo-switch)

    2 wires is all you need, short them together (which is what the thermostat does) sends a call for heat to relay panel/aquastat.

    Besides fixing drafts (which kill heat) and insulation, the cold room... it has its own thermostat? Or is the thermostat in the basement. The basement and bath/laundry share a radiant manifold, so basically 1 zone?

    What kind of boiler? ODR? Aquastat or boiler temp settings?
  • donedeal
    donedeal Member Posts: 36
    The basement and bath share a tstat and are on their own thermostat. Previously it was not hooked up so I jumped it on the zone track box to heat whenever the main floor was heating, so both circulators turned on. Two days ago I just put in a new tstat in the bathroom to see if that would bring the temp up being on its own would call for more heat since the main was heating up faster than the bath...and now this is where I'm at. I put in the same honeywell tstat that the prior owner already has elsewhere, but just with the red and white wires and batt operated.

    That's all I did to install the t-stat, I did not mess with any settings elsewhere.

    The tstat is on the interior wall of the bathroom. I shut the valve off for the basement because it got too hot down there running constantly. Boiler is a gas fired triangle tube. I dont' know if I have outdoor reset, how could I tell? I'm a newbie. Does this have anything to do with the tstat in the bath or is it something that would be directly to the boiler already? The boiler temp settings are adequate to heat the other zones nicely. I don't know about the aquastat either....

    Am I better off just jumping the wiring back so it runs off the main floor? I'm thinking the tstat I installed I might be over my head...
  • donedeal
    donedeal Member Posts: 36
    or do I just leave it running for a few days and see if it eventually heats up?
  • Brewbeer
    Brewbeer Member Posts: 616
    edited January 2016
    I'm gonna guess that you don't have enough emitters in the addition space to meet that space's heat loss, and you need to add emitters to that space to deliver more BTUs.

    A heat loss calc on the under heated space and an estimate of heat output by the existing emitters is in order.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
  • donedeal
    donedeal Member Posts: 36
    is an emitter referring to the loops of pex tubing? as in adding additional loops? thanks for the help everyone.
  • Gordy
    Gordy Member Posts: 9,514
    The vapor barrier on the insulation should be to the unconditioned space.

    How much insulation?

    Is the insulation pushed tight to the tubing, or is there an air space?

    What type of radiant floor system do you have.
    Suspended tube.
    Staple up.
    Are heat transfer plates a part of the installation?
    What are the water temps to the loops?
    Is the crawl space vented?

    The addition with three exterior sides over an unconditional crawl space increases the heat loss considerably.

    Start with that.
    Mark EathertonRich_49Zman