My DH and I changed our plans and decided to go with radiant heat in the main floor instead of forced air. A cement/gypsum thinslab is not an option.
We would like to go with a dry radiant over the subfloor, instead of under the floor joist. We will be doing the pipe installation ourselves, and we will try to have the radiant design part of it hired out.

What I'd like to know is how is this typically done? I know that the pipes get set in grooves in a layer of plywood, with some aluminum plates to help radiate the heat some more. My question is do you put your flooring directly on that? In the carpeted areas do you place the pad (one approved for radiant heat, i presume) right over the pipes, then carpet? In the tiled areas do you use cement board or can you apply the mortar right over the pipes in non-bathroom areas? Or do you cover the whole house with cement board over the pipes and then install carpet and tile over that?
I remember I saw I detail somewhere (that I can't find again) of using cement board instead of wood to set the pipes in.

One other detail i saw on the internet was using sleepers under hardwood flooring to set the tube in and fill the gap with sand. Does anyone actually do this? We do have some plans to use hardwood if budget allows, and this seemed like a neat idea, but not sure if it's a good idea.

Any help will be greatly appreciated. I should add that the radiant in the main floor will probably not be installed for a year or two since we're doing almost everything in the house ourselves, but right now what I need to decide is if the framer needs to double plate the bottom of the exterior walls for the main floor with 2 -2x6 or not? Or if he should use a 1x6 and a 2x6 for the bottom plate. Also, he will be putting in stairs and he needs the best number I can give him for added height to the floor so he can do the stairs right.

Thanks

Sand is a poor conductor and a poor idea.

over a basically continuous plywood infill, flooring goes right on top, though I do prefer to see something put over the assembly when you are under carpet. Using cement board as infill isn't very helpful, but some people have done it with apparently decent results in tile areas.

You really can't decide which method to use until you have a heat load for the area you want to radiate.

I made a post a few days earlier about a product we sell call RHT Floor panel system, you can see the thread on
topic radiant heat posted by Dalladoso. There are some good observations by others on a variety of aspects regarding what you are talking about. RHT floor panel system can be seen here; http://www.blueridgecompany.com/radiant/hydronic/527/rht-floor-panel-system click the link to pictures. This is one way to do what you are speaking of.
Dan