Floor joist radiant heat system

Discussion in 'HVAC Heating & Cooling' started by Jsfalbo, Jul 13, 2014.

  1. Jsfalbo

    Jsfalbo New Member

    Messages:
    5
    Location:
    New York
    Hi, I'm new to this forum and have some questions on my radiant heat system in my ranch house with fully finished basement.

    So I have lived in this house for four years now and one of the selling points, along with the fully finished basement, was the radiant heating system. However, after the first winter in this house (upstate New York) I ended up spending nearly 4k in propane using the system. It seemed to take forever to heat the floors and when it finally did it took a lot to keep the temperature constant. I turned to a wood burning insert I installed and use space heaters in the bedrooms and basement to save money.

    Long story short, I'm tired of dealing with wood and after the electric bills went crazy this last winter I decided to do some research on the best way to revert back to my propane. In this research I have discovered that my radiant floor system seems to be installed incorrectly. After removing some drop ceiling tiles and insulation I found that the entire system is installed perpendicular through the floor joists rather that inside the floor joist wells!! Not only that but it about 3 inches below the underside of the sub floor with no heat exchange plates. So basically the inefficiency of the system is due to the tubes having to heat up all the space between the insulation and the sub floor before it even starts heating the sub floor. I don't even understand how idiotic the installers could have been to do the system this way when I was able to do three minutes of research to figure out how it is supposed to be installed and also how the heck did this system pass inspection by the town!

    Anyway, my question is how expensive could this problem be in trying to install it properly. I imagine all my drop ceilings will need to be taken down , insulation removed and pex tubes some how drained and removed leaving holes bored all through my floor joists, then reinstalled the proper way. Or is there a way I can work with how it currently is to make it more efficient? The tubes do not seems flexible enough in between the floor joists to push them up and try to get heat exchange plates onto the small portions of tubing between the joists.

    And if I have to remove my entire basement ceiling which is over 1000 square feet in six different rooms and hallway is it worth reinstalling the radiant system or having forced air ducts installed instead? Is there a better system to go with at this point and how expensive could this whole screwed up mess cost me?!

    I already spent $16k on this basement my first year in the house after it flooded and I had to take all my walls down for a company to come waterproof my whole inside and outside of the basement with a new drain system then I rebuilt the finished basement myself. I'd hate to have to do this all over again in this money pit!

    Thanks in advance for any advice that can be given!
  2. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,167
    Location:
    North Vancouver, BC
    Wow - what a gong show.

    How many zones do you have in this space?

    I would be tempted to test out two ideas.

    1). Just add the radiant fins below the pipe as is and your done.

    2). Make one zone proper as per spec and test both head to head.

    I purchased Cast Iron Column Radiators and Baseboards for my home. They work awesome. You might consider that as another approach...
  3. Jsfalbo

    Jsfalbo New Member

    Messages:
    5
    Location:
    New York
    Johnfrwhipple, thanks for the reply.

    Yeah I am beside myself with this whole mess! I have three zones. One zone covers the main living spaces, kitchen, dining room, living room, etc. Another zone covers the two kids bedrooms, hallway and main bathroom. The third zone covers the master bedroom and master bath.

    There is actually a fourth zone for the boiler that covers the basement but it is just one continuous copper pipe that runs the entire perimeter of the basement and pops out of the wall in each room with a baseboard radiator. Quite inefficient since I don't ever need my entire basement heated all at once. I wish I thought of separating the basement zones when I had the walls apart from the flood three years ago.

    When you say radiant fins do you mean the aluminum plates that are normally used to hold the tube against the underside of the subfloor? I don't think this would be possible because I tried pushing up on the tubes to get it to touch the subfloor to see if I could do this and they don't quite reach because of the stiffness and not enough slack in between each floor joist.

    I guess just installing baseboard upstairs and bypassing the radiant tubes could be another option. Doesn't look like I'm getting out of this one with low cost though!
  4. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,167
    Location:
    North Vancouver, BC
    I don't think you should push on the pipes.

    Try just adding the fins and insulation below....
  5. Jsfalbo

    Jsfalbo New Member

    Messages:
    5
    Location:
    New York
    I see what you are talking about now with the fins. I checked out Ultra-Fin and saw how they do the installation perpendicular with the use of their fins that don't actually touch the sub floor like the other heat transfer plates I've been seeing with installations. $150 for a pack of 100, I'll probably need a few packs but definitely better then pulling out the whole system and I'll only have to take down the insulation rather than the entire drop ceiling.

    Thanks for the help! Of course I would much rather the system have been installed properly and more efficiently but this gives me a bit of relief knowing I can do it this way and hopefully I will be able to use it this coming winter with more efficiency!
  6. Dana

    Dana In the trades

    Messages:
    2,841
    Location:
    01609
    Getting more effective heat transfer out of the suspended tube by adding clip-on convectors will allow the boiler to heat the floors more effectively due to the higher heat transfer rates, but it won't save any money on propane- it's not more efficient, just more effective. All the heat from that propane you burned went into the house, not anywhere else- it just didn't keep you as comfy as you liked due to the less effective heat transfer between the plumbing & floor.

    Adding the Ultra-Fin clip-on convectors may make you more comfortable, but your propane use will rise slightly, not fall. If you're spending $4000/year in propane now, you'd be spending a bit more than $4000/year after upgrading the radiant, since it's now possible to run the house at a higher temp, which increases the heat loss out of the house.

    The only way to save money on propane is to switch to a different fuel, or dramatically lower the heating load. You can get marginal efficiency boosts out of switching to a condensing propane boiler and optimizing the heating system, but after spending the $30,000 necessary to get there you'd likely still be using $3000/year instead of $4000.

    But you can get a lot more for a lot less outlay by heating one or more zones with a cold-climate ductless air-source heat pump (mini-split), delivering heat about 1/3 the cost per BTU of heating with propane. It works best in large open floor plan zones, hopefully that describes at least one of your lossier zones. It's not cheap to install, but it will pay for itself in reduced propane use in under 3 years (at recent years' electricity & propane pricing) if sized correctly. The other upside is that you get high-efficiency ultra-quiet air conditioning with those units along with the lower heating costs.

    If by "upstate" you meant Westchester county there are many options that can work for you, but in colder areas than that you'd be looking at primarily the Fujistu -xxRLS2-H series or the Mitsubishi -FHxxNA series mini-splits.

    Fixing all of the lower-hanging (and even some of the higher) fruit on the heat leakage end is worth it too, but it can be complicated to figure out which is the first-best place to start chipping away at it. If the "fully finished basement" doesn't have any insulation it could easily be 25% or more of the total heat load, but pretty expensive to retrofit since you would have extensive re-finishing to do to get there in a way that doesn't create mold hazards etc. Fixing air leaks in both the basement and at the attic floor plane is always cost effective, but if you have any atmospheric-drafted appliances (the boiler, perhaps, or a water heater) backdrafting can become an issue if you do it in the wrong order.
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