Hi,

We came up with this schematic for our radiant circuits. We're DIY and our first radian project. Any glaring errors that those with more experience can see, will be really appreciated. The bar/lounge/family room are one circuit (300 ft). The BR3 and BR4 plus bath are another(300 ft). The Office/mech room is another (150 ft), and the BR5 is one (150). I think we're using 3/4" pipe.

Also, is it good idea to put wiremesh on top and bottom of pipe? Just on the bottom? Or none at all and use little clips?

Thanks!

dont waste your money and time with large diameter pipe. no reason to run larger than 1/2" here.

do not go over 12" o.c. in a residential slab.

you should really try to avoid walls more. You are exposing yourself to a lot more puncture risk.

Also I suspect you still have not done a heat loss and so you have no idea how these circuits will perform, or whether on center distances should be adjusted. concrete is forever. it would be a shame to have to run ten degrees hotter forever because you didn't compress tubing in a higher load or more resistive floor covering area to compensate. that means carpet areas especially.

hope that helps.

lifted wire mesh has a slight performance increase over tubing at the bottom of a slab, it's slight, but since mesh should be lifted anyway if you are a purist that's the way to go. Otherwise, foam stapling is a very fast install, or something like crete-heat is even faster; and cheaper than foam staples. wire mesh/ties is the cheapest, slowest, highest performing option.

btw, nice looking drawing work though. I always look at problems first, working on trying to recognize the positives too ;)

Thanks Rob. You are correct that we have not run any numbers. How do you do a heat loss analysis? Is it something that I could try or do I have to hire someone to do it?

nice picture. I assume that this is a slab on grade.
Since the tube spacing is all the same it appears that no heat load calculations were done. I recomend doing this before you go any further.
For the tubing design I recomend that you stay away from walls. Do not go under except where you need to. You also dont need tubing under your kitchen cabinets or in the closets. I would use more loops at a closer spacing. That will allow you to lower the water temperature.
Where are the expansion joints for the slabs? you have to run tubing under the joints, not through.

I always use steel in the slab. If its a 4" slab I would use 1/2" rebar 16" on center. I put wire mesh down to tie the tubing to. Then put in the rebar over the top.
1/2" tubing will be fine. I only go to the larger diameter when the runs are long.

BillN,

Yes, I'd like to run those numbers, my question now is if heat load calculations are something we can do ourselves or if we have to have someone do it for us? If I can try to run them is there a book or website that I can use to guide us?

Has anyone used the design services at pexsupply.com? Is it worth the money? I think that's where we plan on purchasing our supplies, since we're diy.

Thanks.

I found this little heat load calculation form online, http://www.h-mac.com/heat-load-calculator/heat-load-calculator.php
Can anyone that knows something about this stuff take a look and tell me if this would get me close to get started? There wasn't anyplace on there about floor covering, which I think would make a difference if it's concrete exposed or carpeted, but maybe it is good enough without that information.

Thanks.

Is the HVAC computer software a good buy for heat load calculations? Once I get my heat loads what do I do with them and how does it relate to the radiant design? Thanks.

Here's an updated design. Still no heat gain/loss calculations, but I'm working on those and we'll make changes if we need to. So, they are all 300 ft coils give or take a few feet. 1/2" pex with oxygen barrier. We decided to go 6" o.c. under carpeted areas, 8" o.c. in exposed concrete areas. We have 7 zones.
Zone 1 has two circuits. Zone 2 has 1. Zone 3 has one. Zone 4 has 2. Zone 5 has 1. Zone 6 has 1. And Zone 7 has 1, though I need to redo that one so i route more to the mechanical room and less under the stairs. Any comments will be welcomed.

The black square grid is the planned control joints. When we actually lay the pipe down, any pipe running under a joint we'll off-set to the side, but those that cross perpendicular to the joints need to be sleeved, correct? How do you sleeve the pipes that go through control joints? What do you use for sleeves.
Also, anyone uses those twisting insulation clips? We'd like to use those then lay the reinforcement mesh on top of the pipe, but we're concerned if they can be ripped off by the concrete guys walking over them as they work on the pour.

Thanks for all the help!

You really need to hire someone to do the heat load calcs, and the radiant design. You can use a program, like I did, such as HVAC Calc, which only cost about $50 for a 2 month license. However, it only gives you the overall heat loss, not as detailed as an HVAC contractor can do. My HVAC contractor nephew ran me a heat load calc that gave me a room by room analysis. Very enlightening. One of the smallest rooms had the highest heat load because of house orientation and size of windows. The program he uses, WrightSoft, costs thousands of dollars -- not something I want to buy!

So, because of the cost of the tools to do the job right your best bet is to find someone to do the heat load calculation and radiant design for you. House construction, orientation, shading, window size, location (determines min and max temps and degree days), air changes per hour, etc., are all factors that enter into the calculation. You also have to determine water temps, velocities (faster moving water doesn't cool off as much but costs more to pump), and tube spacing on a room by room basis. These factors then help decide how many zones are practical (the fewer the better), what sort of mixing valves you need, how many thermostatically operated and manually operated control valves you need, what the supply temperature from the heater should be, what type of control panel you need, and on and on.

Who knows, you may need a mix of 3/8" and 1/2" tubing spaced at 8 or 9" in the center of the room and 4 or 5" at the outer walls, or hotter water at the outer walls and cooler at the interior, or something of the sort. And then there's the differences between carpet and ceramic and stained concrete and hardwood floor covering. I'm just trying to point out there are too many variables for a novice to know and understand.

But, I do give you credit for trying!!

Boontucky-girl, get the book "Modern Hydronic Heating" by John Siegenthaler, P.E. It'll give you lots of good info, make you aware of what all is involved in doing the job right, and make your head swim, all at the same time!!!

the radiant design is complicated, sometimes iterant.  once the heat loads are calculated, the floor coverings specified,  the tube spacing and water temperature are juggled to provide heat output to the rooms to satisfy the loads. in many cases, especially in colder climates, there might be supplimental heat needed.
here is a slab RH design that I did a few years ago showing different tube spacings and floor coverings. Notice the manifold locations and balanced tube lengths.
Its painfull to see you flounder on this design as a DIY. I do this design work for a living and I would be glad to do this design for you. I have the heat load software and Autocad for the drawings. I would estimate that your design would take me just over a day. If you like, you can give me a call and we can talk about it. Check out my web site. I have lots of pictures installing RH slabs in my home.
Cheers,
Bill Nichols 908-490-1911

Professional design help is the key to DIY success. Whether the design comes from a material supplier or an independent designer like our friend Mr. Nichols a certain amount of experience is necessary for success. The important thing is to have a plan before you invest in expensive materials you will expect to last forever. This is not the place to design your system.

I wanted to thank all of you for all of the great advice. I've been contacting several professionals in and out of my area for initial quotes on design fees. It's very hard for us to fit in the budget the money that is needed to have the radiant professionally designed. But now I am convinced that not having the heat loads done is something we can't afford either, so I am at a loss as to what to do. The local installers do none of the heat load designs. All of the contractors in the area that do radiant place the tube at 12" oc, whether it's carpeted or not. If I want them to avoid where the walls are going, they will do it, but otherwise they don't bother with that. No one does loop designs, and they all go with a standard max loop length depending on the pipe size. I am very surprised to find that the so called professionals around here do none of the things that have been recommended.
I find it alarming that the systems are not being designed. All of the contractors I spoke with have 10+ years doing this and their references check out, so I'm confused as to why people around my area aren't complaining more about radiant.
So I was thinking that I would be better off having someone design and install the system for me, but the installers don't do design and the designers I can't afford.

So I went to my local library, checked out every book on radiant available and I got enough information to do something, but not really sure if I'm doing it right. I set up an excel sheet to do all of the heat load calculations for my house. I'm basing it from Sieghenthaler's book on Modern Radian Deisgn.
I downloaded a trial of HVAC Calc, but at this moment I can't pay the $50 fee for the homeowner license. I am happy to say that the two numbers that are given for free on the trial of the software are almost exactly what I can do with my little spreadsheet, so that makes me feel like I might be on the right track.

So if I could enlist some help to make sense of what I am doing, I would really appreciate it. I have the heat loads for each room, the flux for each room, I have design temperatures, water temperatures, I can calculate temperature drops for each run of pipe, and do some other things, the question is how to put it all together?

As an example: For my Bar-Lounge area I get an estimated 5884 BTU/hr for a desired temp of 72F indoors and -15F design temp for outdoors. If I were to use .5 pex pipe at 9 in o.c., according to my calculations, I would need water temperature of about 100F for exposed concrete to keep the slab at about 82F. It would take 360 feet of pipe with 100F with a flow rate of 1.5 gpm to maintain a temperature drop of about 9F to have an upward heat output from the slab that will meet the 5884 BTU/hr.
If I increased the spacing to 12 in oc, the numbers change to 101F water in the supply. But to keep at temperature drop of about 9F I would need 355 ft of pipe. The available floor area that will need tubing is 296ft^2

Does that make sense? I am following the formulas and I am starting to get a grasp as to what the numbers mean, but I really don't have any experience in this type of work, so I can't be sure that my numbers are right.


Any comments and help will be greatly appreciated.

Thanks,

Boontucky

Yea, that's typical. Around here we use xx BTU's per sqft, got that kid? And, if you have have an efficient structure, you waste $$$$. Silly. We have a free Heat Loss Calc on our website. It works, and it's accurate. It will not, however, determine your Radiant Heating design. That's for a pro(like Rob).
Enjoy!

My understanding was that heat loss is a rate of loss per hour, the BTU/ft2 is the flux, which is technically BTU/hr/ft2. But what do I know, I'm simply going of what I read. Like I said, I have no experience in this, though I do have a little bit of physics and thermodynamics and properties of materials in my undergrad study.

Anyway, my comment about installers not doing the design, I meant that they don't do them, and they don't hire anyone to to them for them. At least the contractors I called. I guess I was under the impression that not looking at the head loads in a radiant design could mean a very inefficient set up. My point is that I can lay pipe at 12" o.c. myself, and that's actually how I began, thinking that I could simply lay down the pipe and worry about hooking it up later.

I am really not asking anyone to do my design, I'm asking for help to understand if I'm on the right track to do it myself. It's taken me a lot of reading and a lot of time to get what I have done, and I know some of the experts can do all of this in a day. But I'm in the situation that at this point I simply don't have the money to hire someone to do the heat load and design the whole system. I also can't afford to install the radiant design completely, and my hope was to get far enough that I could at least bury the pipe in the concrete and maybe in a year or two add the boiler room.

We will be constructing our new house for the next five years for sure, simply because we can't afford to do the whole thing at once, and also we are doing everything except pouring the concrete for the ICF and framing the walls and roof. The rest we will do ourselves, and we still work full time jobs.
But thanks for the heat load calculator. I will certainly use it.

Boontucky.

If you ever move to maine, look me up. We'd probably have a job for you ;)

You are probably over stressing. You can avoid disaster and get a decent system by doing this: stick to a 250 max loop length, do 6" o.c. under carpet, 12" o.c. elsewhere, and isolate all major rooms on their own loops as much as humanly possible.

That leaves you in a place where you have very good flexibility to do whatever you need to do in the future. Maybe you won't utterly minimize your electrical consumption to a 50 watt resolution, or your water temperature to 5 degrees, but you will keep yourself out of trouble and know that if radiant can do the job, you are in a place where it can be done. If you want to DIY design, accept that the results won't be "perfection", and shoot for "pretty good". It's probably not worth the time you're putting in for the benefit you're likely to get.

If you want to CYA, use a manifold that can take loop actuators if you want to be able to add zoning later, and leave a wiring conduit from the manifold to your future mechanical location. Or, arrange to pressurize the pipe without a manifold or any manifolds, and delay that decision until down the road when you can figure out what zoning you want.

Hope that helps and best of luck!

Framing the walls is doable as a DIY part of the job. Particularly so is you can have someone with experience to show you how to actually put all the 2 x 4s together.

One observation (caution?) I will offer from my recent experience. How much time do you anticipate between getting the ICF walls up and getting them covered with siding? The reason I ask is the foam turns yellow and chalky in only a few weeks. I pressure washed my walls about 3 months after they were up because they had turned pure yellow! The surface was also very powdery. After pressure washing back to a nice bright white, I can see the blocks turning yellow in just a matter of days. There is also a light coating of powder on them which is interfering with the stickiness of window flashing. It wouldn't take very many washings to obliterate the block markings. So, based on my experience I would say it behooves you to get the siding on as quickly as possible after the blocks are up.

Thanks Rob, I really appreciate that response. That helps me out a lot!

Thanks for the tip Dmaceld. Yes, I think we could handle the framing if we had someone to show us and we had the time! We had started out that way, with hiring the framer just to set the trusses up, but it's getting cold too quick and we want the roof on before we get the first real snowstorm. And working three to four hours in the evening now that it gets dark so soon it would take us a loooong time to make progress (plus we have a 20 month old child so basically until he goes to bed is only one of us working!) I contacted the siding manufacturer about installing their siding on ICF, and to keep the warranty, I have to put a vapor barrier on top of the ICF, so as soon as the main floor is framed when the carpenter adds the house wrap, he'll start at the ICF and go up. So that should help somewhat. We do want the siding up before winter really sets in too.

Again, thanks for all the help!