Hey guys I have 1250sq ft driveway in long island, doing snow melt there, I put aluminum bubble first then metal mesh, i Did 3/4 pex 350-400 feet max, spaced 11-12 inches, do you guys think that will be enough or i should put another loop in between, some sites saying its good some saying 8 inches i dont know anymore, please help...

First, let's start with appropriate insulation; say 2" of XPS. Bubble wrap is not insulation by any accepted standard.

Snow/Ice melting systems rarely lend themselves to DIY and more rarely to DIY design.

First the proper load information, application referencing the Class of system desired, heat source, fuel and controls.

Once I have this information and plug it into a dedicated software package, then model the half-dozen viable patterns and tube spacing options to get the most efficient design possible.

http://www.greenbuildingadvisor.com/blogs/dept/musings/stay-away-foil-faced-bubble-wrap

Well thanks for replay, I am doing this project by my self to save money, got lot of opinions and I value your that's why I am here, I will get this foam boards but I cant go with 2 inches that would only leave me with 2 inch of concrete since I still want to install pavers on top of that...help if you cant, looking to get some pointers to do this outside part right,

Their is no reason to install concrete under pavers. If you have a 2" thick paver the PEX can go in the sand below. You can also rethink insulation depending on the operation.

As I said, it is not easy.

Yes, a SIM system for a paver covered surface is a very complicated affair to get right. The problematic issue is that you can’t allow any water to accumulate under the pavers because subsequent freezing can cause heaving.

In areas with low permeability soil, the base layer below the EPS insulation should be at least 6” of crushed stone. Drainage piping that removes accumulated water to a nonfreezing disposal point may be necessary. EPS is impermeable to water, so it needs to be drilled with 1” diameter holes spaced 12” apart so it will drain. 60 PSI EPS is recommended if there will be vehicular traffic.

The EPS is covered with water permeable filter fabric and then a 2” layer of sand is placed. Welded wire fabric (WWF) is placed on top of the first 2” layer of sand and the PEX is then tied to the WWF and pressure tested. Finally, another 2” layer of sand is placed before placing the pavers. 121 Btu/h/sf is recommended for a Class 1 SIM in NYC, which is the highest in the country (e.g., Minneapolis-St. Paul, MN is only 95 Btu/h/sf).

All of this information and more can be found in John Siegenthaler’s “Modern Hydronic Heating”. This can certainly be accomplished as a DIY project, but it must be done right or it will likely be very short-lived...and pavers are not cheap. Perhaps you should consider concrete colored/stamped in cobble stone. ButterField Color's Dublin Cobble Stone stamp is my personal favorite.

The hazards grow if you get second-hand information from someone whom has likely never seen a SIM system in operation, let alone designed one; book or no.

We make a 1.8" panel that could be used as your insulation. Check it out at creatherm.com for an estimate. It helps do your layout as the panel is insulation and holds/protects the tubing also.