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.

Zones and radiant floor

I'm doing some planning and have been considering having the bedrooms and bathroom upstairs as different zones so i can keep them cooler/warmer as the user's prefer. I am still playing with heat loss and am pretty sure its going to need make up heat. So i plan on doing 2 stage with floor being the first and baseboard as the 2nd. Anyway, After some thought I'm not sure how practical the multi zones will be due to the animals in the house and having to keep the doors open to the rooms so they can roam throughout the house. Also, downstairs 2 of my rooms only about half of the room is available for floor heat due to lack of access to the floor, so it will be mainly baseboard. That is the kitchen and the dining room. I was planning on doing the kitchen, dining room and the living room all in different zones. The living room has the stairs and 2 entrances one to the kitchen one into the dining room. The dining room has 2 one into the kitchen and one into the living room. All of those have no doors.

So on that note. How well do multiple temp zones work with open doors? and is it worth doing it if the doors are more likely to be open than closed?


  • Zman
    Zman Member Posts: 7,446
    I am wondering if you are overthinking this a bit.
    Could you post your heat loss and available floor space?
    The absolute max for radiant heat is generally considered 30 btu/ft.
    The slant fin calc adds a significant safety factor.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 19,260
    Consider panel radiators also. Very easy to zone with TRVs

    I'm not a huge fan of radiant floors in bedrooms, too much furniture that limits output, (heat flux) and warm floors are best enjoyed in rooms where you spend more time like, living, dining, kitchen and bath.

    It may be possible to design the system around a single temperature with adequately sized panel rads in the bedrooms. Only an accurate load calc and design can answer the questions, however.

    I'd suggest maximum, comfortable floor output for residential systems in the mid 20's BTU/ sq ft. A carpeted bedroom with a bed, dresser, closet and possible additional furniture would be tough to get 30 BTU/ foot output, I feel.

    A dual system radiant and fin tube or panels seems like an expensive, complicated way to heat a sleeping room?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mustang_gt_350
    mustang_gt_350 Member Posts: 25
    I did forget to add. I did use the slant fin heat loss calculator. I Don't have my paper work with me but the sq footage is a little over 1300. And i believe my total BTU between both floors is around 57k. The major heat loss comes from the kitchen and the dining room with the unconditioned floor space. And The house has been foam insulated from the outside by a local hardware store (not chosen by me it was the PO) They missed most of the corners and about the top 6" or so of the wall cavity. I have been removing drywall and that for fiberglass insulation as i have been redoing the rooms, but not all have been done so far, and will not all be done by winter.

    The master bedroom is rated at a little under 3600btu's and it is 17.5x12, and that is not including the closet space, it is also hard wood floors and the bed is 16" off of the floor with nothing but open space access under it from all sides. This room I have already redone, R38 in the ceiling as opposed to the shoddy blow in ceiling job that varied from 6"-0. Along with new R19 in the walls and 5/8's drywall. I do plan on residing the house so that will add some additional value later also.

    I currently have the bathroom gutted, and part of the hallway/landing that will be redone before winter also, and so will some of the exterior walls downstairs that they "missed" completely when they did the job. I just noticed this about 2 weeks ago for some reason they skipped a 13 or so foot wall with 3 windows in it. And i just noticed it recently after living here for almost 6 years lol. Explains why the kitchen was always so cold feeling, Not to mention the wall between the living room and sunroom wasn't insulated but the sunroom was and it is not heated... once again explains why i always had a bad cold draft along the floor when it was in the single digits .

  • mustang_gt_350
    mustang_gt_350 Member Posts: 25
    edited August 2017
    On another thought and some number playing. based on your statement hot rod... I think the $ may be better spent just re insulating the other walls that are known problems and rooms, and i may be able to get away with radiant only in most of the rooms and only need make up heat in a the 2 rooms that have lost most of the floor space.

    So that money that would have been spent doing the extra controls could almost cover the cost of tearing the other rooms apart now.
  • Gordy
    Gordy Member Posts: 9,537
    You never revealed floor coverings, and type of radiant detail. Although I think you alluded to underfloor.

    I agree with @Hotrod panel rads with trvs in bedrooms is a nice quick responding option. As he said size them for the supply water temp of your radiant for a one temp system if possible.
  • mustang_gt_350
    mustang_gt_350 Member Posts: 25
    edited August 2017
    The only covering will be in the kitchen and dining room. That is planned to be some type of vinyl flooring. The rest is just the original oak tongue and groove that i am refinishing as i go. They are the only floor covering right over the joists. So they are between 3/4 and 1" but i don't remember the exact measurement. The living room currently has carpet, but it will be removed by winter to expose the floor and refinished once i get to that room next year sometime.

    I was shooting to run a single temp, thats kind of why i was thinking 2 stages with the baseboard as the 2nd stage to the floor.

    Another question.
    How far off of the floor does something have to be not to be considered a hindrance to the system? Like dressers that have a few inches over the direct on the floor types, and so on.

    Oh yeah, i was planning on thermofins on 8" centers.

  • hot_rod
    hot_rod Member Posts: 19,260
    Radiant is pretty much a line of sight. If you cannot directly see or stand on the surface, output will be limited or shut down. Base cabinets with kick space for example will not transfer many BTU into the room. Many beds have dust ruffles and that too limits any potential convection transfer from the floor below. Couches or chairs with floor length skirting would also greatly reduce output.

    I think you would really want to limit supply temperature to an old wood floor like that, so look at the actual BTU output at floor surface temperatures 82F or less. Trying to run higher temperatures to cover high load areas could stress that old wood flooring.

    82F floor surface- 70F ambient = 12X 2 = 24 BTU/sq ft. To get 30 BTU/ft you either run a cooler room, or hotter floor surface
    85F-68=17X2= 35 btu/ft

    This assumes that the entire floor surface warms to 85F, which rarely happens, you will have striping, cooler floor surface, between the loops. Radiant Engineering has realistic output graphs for the Thermofin products, try their site.

    Engineered flooring is much better for radiant, but you are dealing with what you have.

    Heat flux example- assume a room 12 x 12 (144 sq ft.) with a 3600BTU/ hr design load.

    Now deduct the area covered by furniture that reduces or eliminates that exposed radiant surface, possibly the bed, dresser, overstuffed chair, etc. Call it 36 square feet of covered floor space.

    144-36= 108 sq ft of actual radiant panel for the 3600 load
    3600 divided by 108= 33 but/sq ft required output at design condition.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mustang_gt_350
    mustang_gt_350 Member Posts: 25
    Thanks for all of the feedback HR. I'm learning a fair amount. I knew area rugs and so on could effect the output, but i didn't think about bed skirts and such really being any issues, but it does make sense as it keeps convection from really happening over that place.

    No wonder so many people have issues with their systems, I bet most are poorly designed. I only know 2 people that have it. 1 loves it but he has a brand new stick built house he built himself, and the other retrofitted a older house and i bet never calculated the heat loss becuase he said he can't really get the house warm when its in the teens.

    I need to play with the numbers and see what i can come up with. I may just bail on the radiant and just do panels, or baseboards. I will have to decide. I really like the idea of the warmer floors as i am always in shorts and no socks in my house.