Underlayment for ceramic tile floor

I am planning to place 3/8 in. thick ceramic tile on my 80 sq ft kitchen floor over an electric heating element.. I would like some feedback on the proper underlayment support for this project while keeping the additional floor height to a minimum. The joists are 2x8s placed 16 in on center. Next comes sheets of 5/8 in. plywood with an additional 1/4 in. of plywood on top. The tile store recommended taking up the 1/4 in. plywood and laying down 1/2 in. cement board. Then install the Flexterm heating elements to the cement board and spread the thin set adhesive to accept the tile. Is anyone familiar with this process?
Ralph
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I use 3/8" Durock under floor tile, but don't know what issues arise from the addition of heating elements, Ralph.
dave
Ralph wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Bay Area Dave"
Dave's not here!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.