Radiant under floor heat and hardwood floors

TRBenj

Ive spent the last few weeks searching the forums and it has been a huge help!  I do have a question pertaining to my specific application though- thanks in advance for any and all guidance!



We are currently planning to install a heating system on the main floor (24x40) of our cottage.  In the past few years we have put quite a bit of money into winterizing and modernizing it- new foundation (full walkout basement), insulation, etc.  The intent is to make this a comfortable year round home... thus the heat.  We are currently planning to go with under floor radiant using 3/8" hePEX and Joist Trak aluminum panels below the 3/4" subfloor.



My concern is that next year's project involves tearing down a wall and putting down new flooring... and our strong preference is hardwood.  The one flooring installer I spoke to indicated that traditional nailed down hardwood flooring was not an option over under-floor radiant heat due to the potential of puncturing the lines.  He suggested a floating engineered or pre-finished floor instead.



I was curious if the information Ive been given is correct, or if perhaps I have other options?  I can still build up the joist cavities from underneath with an additional layer of ply if need be- though Im not sure what effect that would have on the performance of the heating system (thicker floor = less efficient?).  If this would allow me to be safe from nails protruding into the tubing that might be an option though.  Or can I simply have the flooring installer use shorter nails?



Obviously we will need to do our homework when selecting the flooring material and other specifics when the time comes... just trying to keep my options open for the flooring rather than limit myself with the methods used to install the heat.



Thanks in advance!

Big Ed_4

Hard Wood Floors

Floating the floor and using the pre grooved sub floor is a nice option or you could first nail down the floor and then cut the perturbing nails (which sucks if your the one)...



What to keep in mind with radiant wood floors is maintaing a constant temperature .. A system with an outdoor reset and floor sensor is recommended .... The other recommendation is maintaining proper humidity in the home... You don't want the wood to dry out ...



Too much change in temperature and lack of moisture tatters the looks of a nice wood floor ...



Other radiant options are a radiant ceiling or walls .. Radiant is heat x mass ... The more mass the better the comfort ...

meplumber

85 deg F is the max contact temp for the floor.

This is especially important with hardwood.



I do a lot of radiant.  I have architects that refuse to put hardwood over it and one that will do it only over quicktrak (grooved plywood on top of the subfloor with 5/16" tubing).



On all hardwood applications, I put a strap on aquastat on the supply pipe as a limit stop that will shut off the circ in the event that the outdoor reset mixing valve allows the water temp to get too high.



My design water temp for joist trak is usually in the neighborhood of 140 deg's up here in Maine (-10 design temp).  If you are going to do harwood, then consult an experienced radiant pro to help with design.  It could save you the hassle of damaged flooring.



Just a note.  Teragren (sp?) makes several lines of flooring that I have seen used over radiant in some houses with very picky clientele.



Good Luck.

haventseenenough

radiant under floor heat and hardwood floors

have u thought about increasing tubing spacing, more tubing and using glue down flooring. that will keep a better target temp and eliminate nail holes in tubing

icesailor

Radiant Hardwood Floors:

From someone who wears many hats, all the suggestions here are on. I have only one thing to add.

Engineered floors look very nice when first installed. They only have a very thin veneer of wood on the top. If the finish gets worn in high traffic areas, it will look poorly and need to be refinished. Which means being sanded which you can not do. If it were my house, I would use the solid wood floors like Oak or Maple. Strip flooring should be laid perpendicular to the joists to strengthen the floor. 3/4" oak strip flooring will take an incredible amount of "bounce" out of a floor. Your floor installer should know that. He also should know that the most important nails in the flooring are the ones in the joists. Where there are no pipes. The pipes are between the joists. He also should know that it is very common to glue the flooring to the sub floor with PL200 or some type of floor adhesive.  But he should know this. You can nail on the joists and not between and the adhesive will hold the floor in place. "Liquid Nails"? And o matter what they say, they $&*^. The only advantage is that they can put on three coats in a day. All the high end floor finishers I see use alkyd bases finishes.



I go in a lot of houses in a year. I have never seen a 5 year old engineered floor that I would want my name on as the installer or the one who recommended it.

JMO,

Mark Eatherton

If hardwood floors are limited to 85 degrees F surface temperatures...

Then is should be against code to put them into an area with south facing windows, because I have seen unheated hardwood floor surface temperatures of 140 degrees F in the sun....



With that said, and this has been misinterpreted so many times by so many different agencies, it is not even funny any more. The maximum recommended floor surface temperature of 85 degrees, regardless of finish materials, is based on human physiology, not mechanical limitations. If your feet are in contact with a surface that is hotter than your skin temperature (85 degrees F), you WILL break out in a sweat, because your body is trying to cool down your core temperatures and keep you from overheating.



The key to placing hardwood floors over ANY radiant surface is to make certain that the wood is cured to the local back ground moisture (relative humidity) prior to being placed, and to also make certain that the subfloor (if using concrete or gypcrete) is as dry as it can be, and no possibility of it transferring moisture up through the floor (vapor barrier under cement).



I have done sleepers over gyp, and plywood over concrete, and I have found that THE best system available is WarmBoard hands down. Lowest operating fluid temperatures, with highest average surface temperatures for a given fluid temperature.



People shy away from this product due to cost, but they are focusing on the per square foot cost for the emitter, and not paying attention to all the other components necessary to apply other alternatives. Bottom line, the net installed cost of WarmBoard is NOT that much more expensive than the cementitious alternatives, and it is THE most efficient means of radiant heat transfer, and delivers excellent human comfort.



And for the record, I do not work for WarmBoard. I am just a firm believer and applicator of their product.



ME

Eric_32

In my opinion:

In my opinion, the best way to install radiant with hardwood floors is with the above subfloor method using a product like Viega's Climate panel or any other company's similar product, this way the tubing is visible while the flooring contractor is nailing. It will increase the finish floor height however. Sould heat up faster being above the  subfloor as well.



We had a customer that installed a floating floor themselves over this type of radiant system and had nothing but problems with it. It came with a skinny layer of foam on the underside of their new floor which totally blocked out the heat. Definately do research on it before it is installed.



I've made my own panels using regular 1/2" plywood and aluminum flashing under it, with the 5/16" tubing between, and jigsaw out the 180° returns at the ends of the runs. You use pieces of 1/2" plywood as a spacer between the plywood strips as it is screwed down then remove the spacers and you have the correct space for the 5/16" tubing.



Works perfect and much cheaper, if you are doing the work yourself, the labor is definately more than a pre-made panel system. You can create what ever spacing you wish this way,

TRBenj

I appreciate the responses

I appreciate everyone's input, but Im afraid I might have been unclear in my original post.

 

The heat is going in NOW.  The existing 3/4" subfloor and linoleum flooring are staying for the time being.  We will be replacing the floors at a later date (next year?).



I believe this eliminates the Warmboard and "above subfloor" options.  This is why we are going with the below floor staple up and extruded panels.  We also wont have the luxury of putting the floor down first, and trimming the nails.



We are only putting heat on the first floor for now.  The basement is open and we have full access to the joist cavities.



We would strongly prefer to go with a true nailed down hardwood floor when the time comes, as opposed to a floating prefinished or engineered floor... Im just not sure if this is possible.



My real question is:  Is there anything I can do before or during the installation of the below-floor heating that would make installing true hardwood floors in the future possible or easier?  Without compromising the heating system's effectiveness, obviously.



Something like putting an additional layer of plywood up in the joist cavities to essentially "thicken" the subfloor (for nail protection when installing hardwood) comes to mind.  Im just not sure if this would be recommended or not.



Thanks again!

tim smith

RE: hardwoods, plywood etc

If your heat loss is not too bad, another layer of 1/2" plywood won't be a deal killer. Just need to run load and see what temp requirements are needed.Our floor guys deal with nail down hardwoods all the time. They just need to know how thick floor underlayment is so as not to use too long of edge nails or top nails. I would just find a flooring guy to spec what is the min underlayment he needs to get good fastening.