radiant floor heat

[patcooper]

I'm going to be tiling my dining room and kitchen and I'm considering putting radiant floor heat under it.
1) are there any special considerations when doing this?
2) does the entire area need to be done or just the traffic area's?
3) recommendations on quality brands to use

[CWC]

Assuming you mean electric radiant and not hydronic radiant...

1) Depends on exactly what you're doing. What type/size of tile? Any floor height restrictions? What's your subfloor construction? How much square footage are we talking?

2) You certainly don't NEED to do the entire area, but keep in mind that the heat will only be in the exact areas you have the wires/mats. It's not going to spread over your whole floor. I would strongly suggest you do the entire floor.

3) You mean besides www.suntouch.com?
Nuheat
Flextherm
Warmup
Nexans
There are one hundred and one companies doing this now, and most are pretty much the same, quite honestly. I would say just make sure you get one that has a dual-conductor wire, and compare the warranties and materials used.

[patcooper]

I'll be using 13" tiles. Sub-floor will be plywood with either hardi-backer or ditra. Probably hardi-backer. The walk area in the kitchen is only about 6 x 8. An island seperates it from the dining area. The dining area is app. 12 x 12. Our dining table sits in the middle of the floor, so there's really only about a 3' path going around the table.

[CWC]

If you use use Ditra, the radiant would go underneath that. Other than that, the radiant always goes in the thinset or SLC layer under the tile, above all other subfloor materials.
Make sure your floor is sturdy enough to support the tiles you're using...I'm not a tile guy so I don't want to be giving you any numbers, but there's that handy Deflecto tool here to use!
If you're thinking of not putting any heat under your table, just remember this: if you ever move that table, you're going to have a cold square where it was.
Electric radiant heat would never go under cabinets or any other built-ins...because there's no air flow under them there is no where for the heat to go.
If you go over 150sq/ft of heated area, you'll more than likely need to use a 240v system, so keep that in mind when you consider the electrical needs.