How to Install Radiant Heat Transfer Plates

       Radiant heat transfer plates can be installed above the floor or beneath the floor in-between the joist gaps.  Many people, like myself, want to install radiant heat to an existing home where floors are already finished.  Installing radiant heat transfer plates and radiant tubing from beneath the floor is one of the most common retrofit installations of radiant floor heating.  Joist gaps usually carry a lot of dead (unutilized) space.  This space can now be used to run radiant tubing, heat transfer plates, thermostat wires, and provide placement for manifolds.  Some people have had radiant tubing previously installed within the joist gaps, but found that the temperature supplied by tubing alone was insufficient and would like to increase the efficiency of their system by adding heat transfer plates. Installing heat transfer plates is possibly the easiest part of the entire radiant heating system, and the most cost beneficial as well.
 

     Before pulling tubing, the subfloor needs to be inspected and all exposed screws and nails must be clipped or removed.

     Once tubing has been feed between each joist in a loop, there will be two lengths of tubing running in parallel.  The first heat transfer plate is snapped onto the tubing.  Typical joist spacing is 16 inches on-center, with an actual gap of 14.5 inches.

     Other consideration for the allowed placement are tubing size and the bend diameter that the tubing manufacture allows.  You don’t want to void your tubing warranty or kink a tube by bending it too tightly at the end of the gap.  For instance, 1/2” PEX tubing is typically not allowed to be bent tighter than a 10 inch diameter.  Therefore, 4 inch wide plates would be spaced 10 inches apart inside the joist gap.  Other types of radiant heat tubing such as PEX-AL-PEX allow a much tighter bend diameter and can usually allow spacing at an even 8” within the gap and across the floor (a big benefit to providing uniform spread heating).  However you plan your spacing, it helps to create a spacer block from wood to use during the installation.

     Plates are stapled up to the subfloor in progression, using 18 gauge (or thicker) staples or with pan head metal screws.  The staple leg length or screw length should not be longer than the thickness of the subfloor. For instance, use ¾ inch staple leg or slightly shorter for a ¾ inch thick subfloor.  Staple along the flat part of the plate at least every 12 inches, and on both sides of the plate.  A one inch gap should be placed between plates along the tubing to allow for the aluminum metal to expand with heat.    

To keep heat directed toward the floor above and not lost to the level below, the gap needs to be properly insulated.  Radiant heat is mostly achieved through conductive heat, but some convective heating can also occur when a 2” or larger gap is provided between insulation and subfloor.  For instance, a 12” high joist gap could have an R-30 fiberglass batt installed that is 10” high when expanded.  Other people have successfully used cut rigid foam sheets with a foil face to reflect the heat back towards the subfloor.

Feel free to comment for any questions you may have.  I am happy to help!

Which Radiant Heat Transfer Plate is Right for me?

    There are a lot of variables to consider when trying to decide which radiant heat transfer plates to use for your project.  One of the main things to keep in mind prior to starting is what products are currently on the market.  For example, depending on which tube size you were hoping to use, a transfer plate may or may not be available to compliment your installation.  Here I have compiled a list of plate sizes that are widely available for ½” PEX tubing and the pros and cons of each plate.

4’ length by 4” width omega shape

                                         

Pros:  Omega shape maximizes thermal diffusion as there is less space between the tube and the plate.  The omega shape also allows for easier installation as the plate “snaps” into place with the tube, when compared to “u” shaped plates.  Longer plates also reduce gaps between each plate, as there is less space for heat to escape when compared to shorter length plates.

Cons:  Longer plates may be more difficult to install than shorter plates. 

Link to best priced plates of this size:  http://www.ebay.com/itm/200-4ft-Aluminum-Omega-Radiant-Floor-Heat-Transfer-Plates-for-1-2-Barrier-PEX-/251821090171?hash=item3aa1b4e57b:g:4P4AAOSwBLlU~Hs4

2’ length by 4” width omega shape

Pros:  Omega shape is ideal for all installations in that, as mentioned above, they maximize the amount of heat produced and are easier to install as the tube stays in place while you work.  The main benefit of shorter lengths is ease of installation.  Overall, it is a lot easier to lift and keep a 2’ plate in place over a 4’ plate.

Cons:  While the length allows you install the plates easier, it is not ideal as far as reducing thermal gaps in your project. 

Link to best priced plates of this size:  http://www.ebay.com/itm/100-2ft-Aluminum-Omega-Radiant-Floor-Heat-Transfer-Plates-for-1-2-Barrier-PEX-/261759499894?hash=item3cf214fe76:g:PRgAAOSwPhdU-0dh

2’ length by 4” width “U” shape

Pros:  U shaped plates do tend to be cheaper in price

Cons:  Though you’ll save a buck or two U shaped plates are not ideal for projects.  Your tube will not easily stay in place as you’re installing, which could prove frustrating.  Also, the tube may sit further away from the aluminum.  This will cause thermal gaps and the money that you may have saved by going the cheaper route will be lost when the bill comes.

Link to best priced plates in this size:  http://www.ebay.com/itm/100-2ft-Aluminum-Radiant-Floor-Heat-Transfer-Plates-for-1-2-Barrier-PEX-/262545243343?hash=item3d20ea7ccf:g:SZ8AAOSwENxXlpoR

4’ length by 5” width omega/U shape

Pros:  Benefits from 4-foot length and omega shape as mentioned above. 

Cons:  Some people may think that paying more for a 5” wide plate over a 4” wide plate is beneficial as you can cover more ground with the plate.  What some fail to realize, however, is that most of the heat is dispersed where the tube meets the aluminum plate.  Paying more for a wider plate does not really make much sense as the aluminum only aids in heat being dispersed throughout a certain radius.  In other words, this is where you can save the money on your project. 

4’ length by 12” width omega shaped plates

Pros:  You will definitely cover more ground with these plates.  Each plate has two omega shaped channels that snap into the tubes.  Along with the length and omega shaped benefits, you’ll have your project done in less time. 

Cons:  These plates due tend to run a bit higher in price.  Also, the size of the product probably makes installation a bit harder.

Link to best priced plates in this size:  http://www.ebay.com/itm/50-4ft-Aluminum-Double-Omega-Radiant-Floor-Heat-Transfer-Plates-for-1-2-PEX-/262465741234?hash=item3d1c2d61b2:g:4wgAAOSwo0JWJnRe

Why Use Radiant Heat Transfer Plates in your Installation?

    Radiant heating systems typically use pipes or tubes to distribute heated fluids throughout the house.  Heat stored within the fluid escapes to warm its surroundings, hence the name ‘radiant heat’.  The efficiency of the radiant heat system depends on this final transfer of heat to the desired location.  Tubing alone is not efficient at transferring the heat between two surfaces because of its cylindrical geometry.  Only the tangent (tip) of the tubing is able to touch a flat surrounding surface such as a subfloor or drywall.  Additionally, tubing installed horizontally will sag between clips where it will not touch another surface at all.  This system would otherwise rely on surrounding air to transfer the heat from tubing to subfloor by convective heating, which is significantly less effective than direct contact.  This is why radiant heat transfer plates are essential to a radiant floor heating system.  What if your system only had tubes installed with clips originally? The good news is you can retroactively add the plates over tubing to optimize the system with little cost.  Radiant heat transfer plates and tubing can be installed above subflooring in a track style ‘sandwich’ installation or used below the subfloor.  If no floor access is available or loosing headspace is not ideal, radiant heat can be installed in walls or within ceilings too.   

    Radiant heat transfer plates are made with heat conductive materials and are shaped with a central groove to hold the tube.  The best plates I have used are ones that fully surround the tube in an ‘omega’ shaped design.  They snap into place over tubing making it really easy for installation.  This design also has the most surface contact with tubing, compared to ‘C’ or ‘V’ groove shaped ones, and helps transfer the heat to surrounding surface faster.  Some believe, in theory, that a thicker plate material will transfer heat faster.  This is false assumption, as the purpose of the plate is not to store heat, but to simply provide the conductive surface to transfer heat between tube and floor.  Actual performance shows that there is negligible benefit to using a thicker plate material but it will otherwise end up adding significant cost.   This is why it is instead better to focus on using the conductivity of the plate material. Copper is a better conductor than aluminum, but the cost of copper is so much more than aluminum that it is usually cost prohibitive for any build.  Therefore, aluminum offers the best value by performance.  Even within aluminum, there are tempered alloys that are more conductive than other alloys.  I tend to only use the tempered aluminum heat transfer plates to ensure I am getting the best conductivity for the price.  Here is link to the plates I have used with great performance:  

http://www.uspolystock.com/polystock/www/index.php

There are more items than are displayed on the website.  I’d call if looking for a different size or item.