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Radiant planning

MPG Member Posts: 5
Thanks for all the great discussions here, I've learned a lot.

Long story short - we're renovating and considering radiant but are also hoping to use 5" wide 3/4 hardwood (white oak). It would be installed in about 1200 sq ft with R25 walls, double pane low-e windows and simple floor plan. We will also be install a new high-efficiency boiler and are hoping for as low water temperatures as possible.

Thoughts on installing 5"-wide hardwood over Warmboard-R? Are we asking for trouble and need to consider something else for the flooring? Anything else other than Warmboard-R that you would consider better for 5"-wide hardwood?

We have spoken to a heating company that has worked with our family before. They usually use Uponor products for radiant but are willing to use something else.

Thanks in advance


  • hot_rod
    hot_rod Member Posts: 16,312
    the wider the board, the more shrinkage possible T&G helps hide some. engineered or laminated flooring is much more stable. Acclimate the wood before installing, control humidity also
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Brewbeer
    Brewbeer Member Posts: 616
    What is the calculated supply temp for the coldest day of the year?
    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
  • Gordy
    Gordy Member Posts: 9,514
    Shrinkage is more from humidity levels. If you can control your humidity 5” wide is fine. So long as it is properly acclimated as mentioned.

    Personally I like the 5” wide wood flooring. 3” all though less shrinkage is to much like a gym floor...
    Rich_49john p_2
  • MPG
    MPG Member Posts: 5
    Thanks for the comments and helping figure out what makes sense vs being too risky.

    We will definitely plan to acclimate hardwood for a couple weeks if that's the route we go. I have read in other discussions here the importance of acclimating hardwood with radiant, so it's good to hear that repeated.

    Unfortunately, I don't have specifics on supply temps at this stage.

    I think we should be in good shape relative to humidity. The house is new to us but everything has been very dry with no evidence of moisture anywhere (basement, wall cavities, etc).

    Any more thoughts on if Warmboard (though expensive) is preferable/less-risky than other options?

    Thanks again
  • nibs
    nibs Member Posts: 470
    Wood will move up to 1/8th inch per foot across the grain as it dries / moisturizes, it will also cup if one side is drier than the other, and the only thing that might stop it is fully sealing the wood both sides. if it can float to allow expansion/contraction it will help.
  • Gordy
    Gordy Member Posts: 9,514
    Other option is sunboard. https://www.sunboardpanel.com/
  • Gordy
    Gordy Member Posts: 9,514
    I wouldn’t get to hung up on how much the wood moves if properly acclimated. How it’s sawn has a lot to do with it also. Quarter sawn, or plain. That’s the character of solid wood.

    If you want perfect all the time do engineered, or god for bid laminate.....

    The great thing about solid wood is the ability to refinish more times than engineered. So think about wear, and tear. Pets?
  • MPG
    MPG Member Posts: 5
    We've looked at a variety of flooring and really prefer some of the 5" width hardwoods, so I think we would consider radiant wall panels (e.g., Pensotti, buderus, etc) before going with engineered/laminate. We've also considered quarter sawn products but the price of quarter sawn 5" rivals Warmboard, which lead me to ask for opinions here.

    I've looked into Sunboard as well, but haven't gotten a clear answer on their opinion of 5" wide 3/4 hardwood. I know a few people here speak very positively of the silver and graphite Sunboard. Warmboard (I think) is the only product that specifically states they have no concerns until width gets to 5.5 inches).

    It's may sounding like even with Warmboard-R that 5"-wide hardwood is somewhat risky, though, honestly, we're not looking for it to be perfect. We just don't want problematic.

    Thanks again for all the help.
  • hot_rod
    hot_rod Member Posts: 16,312
    I have had customers put 10” wide flooring over radiant. The understood the movement potential. It was a farm style decor and fit their expectations.

    The load of the room will dictate how warm the floor will need to run. Limit the SWT, use ODR, humidify and dehumidify as needed, tight tube spacing and complete aluminum panels. The Roth Panel allies 6” spacing is aluminum and foam. It give the floor a softer feel compared to wood underlay and a bit more R
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MPG
    MPG Member Posts: 5
    Thanks Hot Rod. I had looked at Roth a bit when thinking about potential radiant in the basement. I hadn't given it as much thought for the main floor but I think I see how 6" could be helpful.

    I think we should be able to get good heating loads calculated on everything shortly. We've been waiting on plans of everything being drafted for some of the potential renovations. I have used a few online tools and think we should be in the area of 20 BTU/sq ft. after insulation/glazing upgrades but will need to verify this.
  • Gordy
    Gordy Member Posts: 9,514
    The wood floor manufactorers are always cya of their product line, which leads radiant panel manufactorers to cya their product line.

    Wood floors can be subjected to much warmer than the 82* surface temps the wood floor manufactorers say do not exceed with out a radiant panel underneath. Say a southern oriented room with many windows the floor temp can get much warmer.

    All the rhetoric comes from poorly designed radiant systems with poorly controlled, and runaway floor surface temps. Which do create issues.
  • Zman
    Zman Member Posts: 7,330
    It sounds like it is time to run your heat loss and figure out design temps. From the sounds of your insulation details, I would be surprised if your temps will be high enough to be a concern with 5" oak.
    If you go with panel radiators, Pensotti, buderus, dianorm etc are all the same product. IMO, they are ugly and restrict furniture layout.

    Check out the Runtal radiators for a nicer look https://runtalnorthamerica.com/residential_radiators/wallpanel-vlx-radiators.html
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • kenjohnson
    kenjohnson Member Posts: 74
    Just went through this process myself. With the wall constructions and windows you describe, I would expect your heat loss to be low, so you should be able to use pretty low water temperatures.

    Oak does expand a bit more than other woods - having put in a hardwood floor once, I can tell you that the longer you can acclimate the wood the better. 3-4 weeks stacked in a way that allows air circulation around all of the wood is a good way to make sure that the wood is really acclimated. Most installers won't do this since they don't want to wait, but if you can wait, take the extra time and stack it right for good air movement.
  • MPG
    MPG Member Posts: 5
    Thanks Ken. We're trying to find a good person to the Manual J and met about trying to finalize some of the renovations that need engineering. Hopefully we'll be able to get some answers soon.

    Sooner we can get the Manual J, the sooner we can make a decision and start the clock on acclimating wood.
  • RetrosPex
    RetrosPex Member Posts: 56
    Radiant planning: Gordy's comments are right on the money...there really isn't any issue with the width of the wood itself, it is more related to the overall humidity control in the house. Of course, that depends a lot on where you live, and if you actively control the humidity in your home. Here in the Midwest, you will see wood floors shrink during the winter, and then expand again in Spring. Hotrod's comments are also accurate, if you want the least shrinkage, go with engineered wood.

    Personally, I'm a fan of traditional 3/4 inch hardwoods. You mentioned, white oak....one of my favorites. I put in quarter sawn white oak in a very large dining room 20 years ago, and it still looks perfect. I use only those clinching nails that are straight on one side, and toothed on the opposite side.

    I have a good friend who owns a couple of sawmills, and runs his own flooring. They do wide flooring all the time, and don't have problems with it. Ranging from 3"-8". They have done some beautiful floors mixing both narrow and wider in the same floor. We just did 1400 sf of walnut flooring in a house I'm selling, and it is gorgeous.

    My opinion is that Warmboard is a great product, and putting a 5" white oak floor over-top would be awesome.

  • Rich_49
    Rich_49 Member Posts: 2,692
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • TAG
    TAG Member Posts: 620
    I have retro fitted radiant under quite a few existing typical 3/4 red oak floors and have done the same with a wider cherry/maple/ white oak strip flooring using plates w/o any issues. The Cherry was 4"and 6" wide. I have also done new Warmboard subfloor product and covered with a variety of 3/4 wood flooring -- typical oak strip and wider white oak 4" /8" mix.

    As stated above -- it's all about heat load. 25 years ago people started to retrofit radiant in older poorly insulated buildings w/ 150 degree water. High moisture content flooring on installation day made it worse. Typical strip oak flooring will often gap out in some places w/o any help from radiant in the winter.

    My new project I'm retrofitting under existing wide 6" beech in a large loft area w/ plates. The rest of the house will be very wide reclaimed QS white oak. It's going to be a mix from 6" to 14" wide ... I recently went to a project installed last year using Warmboard that used new QS white oak with some boards as wide as 12" with no issues. It seems glue is recommended in strategic spots on the very wide boards. In my case I'm doing a 1870 stone building so perfection is not desired ... that's why I'm using reclaimed oak. But, I don't want cupping or any wide gaps -- so placing a nice line of glue in the middle of the widest boards may be in order. I ordered a mix of 8" to 12" with some 6" for fitment where needed .... the 14" wide board is for drama in a couple rooms where it will be fitting for a building so old.