Went searching for information for proper install info and ran across this forum - seems to be a lot of good info here and I'm hoping I can get some direction on the best way to finish off my install.

I've been in the process of building a barn / garage over the last 4 years. I've pretty much done everything myself and I've reached the point where I'd like to get the heat working out there - so I'm trying to gather information so I can plan out how to finish this thing.

Here's the install so far - as best as I can describe it.

The barn has a poured concrete floor: 6-8" thick.  Under the floor is 2" of the Owens-Corning pink foam. I used the high PSI load version of the foam to make sure the floor is supported properly.  There's an asphalt base vapor barrier on top of the foam - and the slab is laced with rebar.  I've divided the PEX runs for the radiant heating in the floor into 3 separate runs (3 zones?) - and the PEX was zip-tied to the rebar before the concrete was poured.  I positioned the PEX so that it was approx 2-3" below the surface of the concrete when the pour was brought up to level.  I watched the concrete guys when they did the pour and they were pretty good about not driving any of the PEX down, so I believe it's all positioned optimally within the slab.

I used Wirsbo 5/8" with a metallic oxygen barrier - don't remember the exact line but I could dig it out if needed.  I followed the manufacturer's directions and kept all three of these PEX runs well within the maximum length that was recommended.

Along with the 3 runs in the floor - I ran PEX over to locations where there will be two rooms.  One a bathroom - another an office.  My intention was to use wall-mount radiant panels in these rooms - and potentially control them independently from the floor slab.

After evaluating a number of options on what to use to supply heated water to this system - I decided to use the existing (or a new if needed) - boiler that is located in the house.  So to tie the house and barn together I ran ThermoPex ( http://www.thermopex.com/?src=googletp&gclid=CK3R_-ji_LsCFUjNOgodaUQAWw ) from the barn to the house.  This run is approximately 100 ft end to end - and it's buried about 3-4ft down.  I used the 1" ThermoPex for this run. 

I felt that running tying the house and barn together gave me the following advantages:  I can use the existing boiler , I only need one boiler to supply both structures,  I didn't have to run a gas line out to the barn (likely would have much more expensive than the ThermoPex run) , and it gave me the option of piping heated water back to the house from the barn if I install a wood or pellet boiler or put solar hot water panels on the barn.


So my question is basically this:  How do I best finish this install and tie this all together and get it working?

The barn will have three "zones" (PEX runs in the floor).  Two of these are in the front part of the barn which is 2 garage bays. Normally these would have cars parked in them and this area doesn't need to be kept all that warm - I'm thinking that 40 degrees during the cold weather could be fine.  The rear part of the barn will be my work area - that I would like to be somewhere in the 50-70 degree range for working in.    There will also be three rooms in the barn - each of which I'd potentially like the do temp control on separately.  Bathroom (probably like to keep warm almost all the time) , Office (on it's own thermostat that I can turn up and heat up the room quickly), and an upstairs room that could be storage, shop, or even living space. I'd like to also have this on it's own thermostat.

Can I or should I control the front two radiant loops and the rear radiant loop in the floor separately?  I know there will be some heat loss from one part of the slab to the other (obviously) - if I try to keep them at two different temps - but is this bad practice or something that will just not work in reality.

I understand that a radiant slab is very slow to react to requests for change in temp.  So I'm thinking that I may need supplemental heating say in the back part - and I'd keep the slab at say 50 degrees - and use something like a Modine hot-water heater - or maybe some radiant wall mount panels for when I wanted to bring the temp up faster.

What is the best way to tie this into my existing boiler?  A friend passed on some info on the Taco RMB-1 unit - and it looks like a possible solution for getting this working. But what I'm looking for is more information so I can get a better idea about how to design / put this system together.

Thanks in advance.

One would need much more info to sort out whether the existing boiler will be adequate to supply the barn and if the hydronic fluid supply/return temp drop between the house/barn will be adequate for what you are trying to accomplish. What is the area of each zone, number of circuits in each zone, circuit spacing, and circuit lengths? What is the calculated or measured heat loss for each zone area (with the downward floor heat loss broken out seperately) at your design outdoor temp and desired indoor temps for each zone?

You also may want to take a look at this to gain a better understanding of what is involved in properly designing a HR system:

Borst Hydronic Radiant Floor Heating Design Software

I'm not so much worried about whether or not the boiler will supply enough to heat both structures (although I believe that it will) - but more with what the "correct" way is to physically hook up the system and have it function properly. I see the boiler sizing as a separate issue from the details of building the system out. I'll need to gather some of the information you're asking about because I don't recall it off the top of my head.

While the boiler adequacy issue certainly has to be determined, it can be addressed either way and is not a show stopper…you can always install a larger boiler.

The bigger design question and possible show stopper is whether your 1” times 100’ of PEX can provide adequate heat to the barn. The initial circuits/zones in the barn may get adequate heat, but will the hydronic temp drop that occurs as the hydronic fluid progresses through all the remaining circuits/zones provide adequate heat to these remaining circuits/zones? To answer this question, you really need to run the numbers. If I had to speculate, I would say not very likely.