Radiant questions

First, I want to thank anyone that is reading this and responding to this. I have been getting as much information as possible about radiant heat for a while now and finally came across this website. There is so much good information here. I have some questions, like all of us new to radiant systems potential owners have. I have tried to organize them by category and list.

Second, I will be doing all the installation myself on my new construction. There is no way I could ever afford to have someone do the radiant heating so this is my only option to get radiant heating in my house. I have a budget of around 10k for radiant heating.

What company’s are there to choose for the DIY person? Radiantec, Radiantcompany? Are there others for the DIY that are good? I am leaning towards Raniantcompany so far.

Background information- I have about 1700sq ft on the main floor (3 zones) and 950 sq feet on the second floor (one zone) that I will cover with the sand, concrete or slightly possible gypcrete. I have about 1200 sq feet in the basement (2 zones) living space and 400 in the garage/workshop (1 zone) in which I will put the PEX in the slab over foam insulation. I will have 7 zones total. Everything will be covered with wood flooring or tile except in the garage. This will be a very well insulated log home with passive solar also taken into consideration. I am building in Fredericksburg VA where it can get to about 10F degrees on cold winter nights.

7/8 vs ½ pex tubing. As far as I can see it would be better to do the ½ tubing. The heat given off by the tubing is about the same and it seems to work better with ½ from what I have read. I did read that you can space 7/8 farther apart than the ½” so it will save you money that way. Now, if the heating output is about the same what should the spacing be on the ½” assuming I am building a log home with good insulation. I am wondering, 8”, 10”, 12”. I would assume that if 7/8 tubing can use 16” centers and work ok that if I use the ½ pex which has about the same output then I can use 12” and be fine. Am I crazy thinking this. Is having more 2x4’s on the floor for the sleeper system going to affect the system and the way it heats? Also, should I use the O2 barrier PEX or not if I plan on using a closed system? The O2 barrier should add about $500-750 to the cost.

I downloaded and read the radiant floor company manual and like what I see so far. I see that they recommend a sleeper type of floor systems for above subfloors, which makes sense to me. I will be building on 16” center for my floor so it can take the weight if needed for concrete. With the sleeper system, do I just use 2x4’s or if using ½” PEX tubing should I use like a 1”x4” (maybe just cut down all the 2x4”s)? In the areas that need tile I could adjust the height of the 2x4’s to match the flooring overall to make it more seemless. I would assume this is a common practice, but is that true?

Sand versus concrete? I do not think I can afford the gypcrete option due to cost. As of now I plan to use the sleeper boards method. In the Radiant flooring manual is says I can use sand and/or then cover it with plywood in areas that need tile or I can use sand mixed with Portland cement with a mixture of 4 sand to 1 cement in the tile areas. Which method would be better? Can I use just sand and have it work well? Or should I use the Portland cement/sand combo more? I wonder the overall cost of such a mixture if I wanted to due the entire house this way? If I have the sleepers on 10” or 12” centers I would think that strength is not an issue, more of transferring the heat.

How much should gypcrete cost for about 2200-2400sq feet if I can afford this considering there is a big advantage?

Closed vs open. I was going to go with the open system until I read the site here and now will go with the closed system and a heat exchanger. Thank you all for the information. Is there a specific heat exchanger that works best? The heat exchanger seems to cost about $500. As far as I can tell this is the only added cost to the closed system or do I have to add other pumps, valves, switches, expansion tanks, etc? Is this correct? Should I also just go for the largest heat exchanger I can get? I assume this is just like a car radiator so I would think the larger the better and faster transfer of heat?

Does each zone need its own pump or can there be one larger pump with multiple switches? Most of what I see is multiple pumps.

I plan to use liquid propane and a boiler. What size boiler do I really need? What boilers brands are good and affordable? What is a dual input/output boiler? As far as I can see water goes in cold and comes out hot. Is a dual one that has the basic heat exchanger built into the unit? Is this worth the extra cost? Is it much more efficient?

When I do the radiant heating myself I will still need AC in the summer. In VA it gets hot and humid. Is there a smaller more specific type of HVAC system I should be looking for that is more for AC and maybe some slight heat if needed? What about the UNICO system? I have also been told in my basement I could really mainly use a dehumidifier to keep it cool, is this correct?

How do I know what pump to use? High, low or medium. My mechanical room will be in the basement.

Thank you so much for helping me figure all of this out.
Troy

Troy,
I admire your tenacity. You ask alot of very good questions. But no where did you mention a "heatloss calculation" of your proposed dwelling. This first step will unlock the answer to many of your other questions. Examples tube spacing, and size of the heat source needed.

I know you said you are building a well insulated log home. Is this a half log configuration? Full log homes can be leaky, and careful considerations need be taken on a heatloss calc.

You have done considerable research and have acclimated yourself with the components of radiant system,and some design aspects. Concentrate on a good heatloss calculation for right now,and the other answers will come from that.

Look under find a RPA member and see if someone close to you can assist you with a heatloss,and system design. It will be money well spent on your first step. Aspecially with a log type dwelling. Certain inputs need be interpulated in the calcs by someone who has had experience with log homes.

After a good design recommendation has been made it will take all the guess work out of component selections for you.
Gordy

Gordon,
Thanks for the reply. Some log homes are leaky and not as good. I believe I am building one that is very good and the windows will be good also. I am trying to control cost so a heat loss calculation may cost a bit much. I would also think that from the company I pick to go with they could do a heat loss calculation to figure out what configuration I would need.
Troy

[QUOTE]Originally posted by Troymx576:


What company’s are there to choose for the DIY person? Radiantec, Radiantcompany? Are there others for the DIY that are good? I am leaning towards Raniantcompany so far.

If you're careful and you've done your research, you can get a good system out of some of those companies. Don't let them talk you out of the things you know you want though, like 1/2" tubing or a heat exchanger. Of course, none of the companies you mentioned do rigorous heat load calculations; you should treat them like supply houses rather than design companies, and do your heat load figuring and system planning another way, IMO. Heat loads are critical if you want to be sure you're doing the right thing.


7/8 vs 1⁄2 pex tubing. As far as I can see it would be better to do the 1⁄2 tubing. The heat given off by the tubing is about the same and it seems to work better with 1⁄2 from what I have read. I did read that you can space 7/8 farther apart than the 1⁄2” so it will save you money that way. Now, if the heating output is about the same what should the spacing be on the 1⁄2” assuming I am building a log home with good insulation. I am wondering, 8”, 10”, 12”. I would assume that if 7/8 tubing can use 16” centers and work ok that if I use the 1⁄2 pex which has about the same output then I can use 12” and be fine. Am I crazy thinking this. Is having more 2x4’s on the floor for the sleeper system going to affect the system and the way it heats? Also, should I use the O2 barrier PEX or not if I plan on using a closed system? The O2 barrier should add about $500-750 to the cost.

You can use an O2 barrier or all non-ferrous components. Between the two, the O2 barrier is probably easiest and will make future maintenance simpler and cheaper. Bronze pumps are expensive! You do not want to install pipe at 16" o.c.. 12" o.c. is a max, 8 or 9" oc under tile or other low-R coverings. Anything wider and you will notice heat striping under certain circumstances at least. If you want to forgo sleepers, use a floating floor.

I downloaded and read the radiant floor company manual and like what I see so far. I see that they recommend a sleeper type of floor systems for above subfloors, which makes sense to me. I will be building on 16” center for my floor so it can take the weight if needed for concrete. With the sleeper system, do I just use 2x4’s or if using 1⁄2” PEX tubing should I use like a 1”x4” (maybe just cut down all the 2x4”s)? In the areas that need tile I could adjust the height of the 2x4’s to match the flooring overall to make it more seemless. I would assume this is a common practice, but is that true?

Gypcrete must be 1.5" thick, so your sleepers need to bridge that height.

Sand versus concrete? I do not think I can afford the gypcrete option due to cost. As of now I plan to use the sleeper boards method. In the Radiant flooring manual is says I can use sand and/or then cover it with plywood in areas that need tile or I can use sand mixed with Portland cement with a mixture of 4 sand to 1 cement in the tile areas. Which method would be better? Can I use just sand and have it work well? Or should I use the Portland cement/sand combo more? I wonder the overall cost of such a mixture if I wanted to due the entire house this way? If I have the sleepers on 10” or 12” centers I would think that strength is not an issue, more of transferring the heat.

Sand is crap, it has highly unpredictable performance and lesser transfer than concrete/gypcrete. Don't do it.

How much should gypcrete cost for about 2200-2400sq feet if I can afford this considering there is a big advantage?

Not sure, but if it's too high, you could consider an over-the-floor dry system (like a sandwich method install).

Closed vs open. I was going to go with the open system until I read the site here and now will go with the closed system and a heat exchanger. Thank you all for the information. Is there a specific heat exchanger that works best? The heat exchanger seems to cost about $500. As far as I can tell this is the only added cost to the closed system or do I have to add other pumps, valves, switches, expansion tanks, etc? Is this correct? Should I also just go for the largest heat exchanger I can get? I assume this is just like a car radiator so I would think the larger the better and faster transfer of heat?

You will want standard closed system components; fill valve, expansion tank, backflow preventer. Larger heat exchangers are good, but no need to jack up the HE cost if you don't need it. For a system this size, you might want to consider moving up to a condensing boiler like a Munchkin, which gives you a closed system without the HE plus great efficiency for your low temp system (I expect it to be low temp at least!). You will have a decent sized heat load, so higher efficiency looks better and better!

Does each zone need its own pump or can there be one larger pump with multiple switches? Most of what I see is multiple pumps.

We zone by pump, but it's a matter of preference. The cost differential is, in our experience, small between the two methods.

I plan to use liquid propane and a boiler. What size boiler do I really need? What boilers brands are good and affordable? What is a dual input/output boiler? As far as I can see water goes in cold and comes out hot. Is a dual one that has the basic heat exchanger built into the unit? Is this worth the extra cost? Is it much more efficient?

We think it's better to have DHW in a seperate storage tank, for a lot of reasons.. sorry, no time right now [b]



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Northeast Radiant Technology, LLC
-=RFH Design, Supply and Consultation=-
RPA certified Radiant Designer
http://www.NRTradiant.com
rob@NRTradiant.com

quote:

Originally posted by plumbob:
Troy - please have a heat loss done. It is for your benefit. Would you use a fiat to pull a backhoe or a truck, and on the other hand a semi and a flatbed trailer would be overkill to deliver just a residential washing machine. Look on the RPA website and see if someone in your area can give you a hand. Ihave helped homeowners in the past where I live and am doing two projects at the present time. Heatloss is critical. Good luck.

[This message has been edited by plumbob (edited 03-01-2005).]

I can't agree more with the other replys. Get an accurate heatloss calc. first. You wouldn't build a house without a set of plans would you?

You would think that if you were purchasing a system from someone, they would do a heat load.

Unfortunately, you'd be thinking wrong. Lots of places don't, and rule of thumb you into a system that you may or may not need, that may or may not work, that may or may not intelligently "control your costs" without sacrificing what will really do you some good.

Insist on seeing a room by room heat load calculation from anyone who claims to be "designing" any kind of radiant system for you. Insist!

------------------
Northeast Radiant Technology, LLC
-=RFH Design, Supply and Consultation=-
RPA certified Radiant Designer
http://www.NRTradiant.com
rob@NRTradiant.com

How much is a typical heat loss calculation? Where and who can I get this done by? I assume this will tell me how much heat I need to put into the house to keep it warm. What would this do? Would this just tell me how far to space the piping? Where to put the piping? How strong of a boiler to use?

I was thinking about using the Munchkin heater. It seems a little more money but if it is more efficient and comes with the dual system so I do not have to have a heat exchanger then the extra cost is well worth it. Would this be the Muhchkin 199?

As far as the flooring. After reading what I have I plan on using 1/2 pipe on 12" or 10" spacing. I would use the slepper 2x4 system. I plan to use basically all hardwood flooring throughout the house so the 12" or 10" spacing should help with this.

Now, I will put concrete or gypsum (if I can afford it) in there. I was thinking about using the 4 parts sand to 1 part portland sand. I could mix this myself and I would think this would work well, I can install it myself and might be the best and least expensive option for myself. Is this realistic to buy the concrete bags, sand and mix it up myself and pour it in? I know it will take some labor.

BTW-The logs are 6" wide soft wood, pine.

Thanks again for the help.

Troy, take a deep breath and slow down before you make a mistake you can't undo.

You've learned a lot and that's good. But you now need to put all your ducks in a row.

Every professional who has responded has told you that you need a heat loss calculation done. The reason is that's what drives everything else. You can't choose a tubing size or layout until you know how many btu's each room will need. You can't choose a boiler or other heat source until you know the total btu load. You can't properly evaluate the different methods (warmboard, extruded plates or homemade concrete) until you know - not guess - KNOW how much heat you're going to need.

Think of it like the footings for your foundation. If your footings are too small, eventually you get settling, cracking and falling down issues. If your footings are too large, you've poured money into the ground for nothing.

Check out some of the professionals that have replied to you and get a firm footing under your radiant project.

Just another homeowner

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Josie

[This message has been edited by Josie (edited 03-02-2005).]

I'll reiterate that sand is a mistake as well. You're rolling dice if you go that route.

------------------
Northeast Radiant Technology, LLC
-=RFH Design, Supply and Consultation=-
RPA certified Radiant Designer
http://www.NRTradiant.com
rob@NRTradiant.com

One word of caution is it is typical thinking by Munchkin suppliers/installers that a heat loss calc is not important because the boiler will modulate to whatever the load is. There is a little truth to that on a baseboard/radiator system with no outdoor reset. Radiant systems, however, are much different. The boiler may modulate to the load, but without a HL calc you aren't going to know where to set the reset curve, what temps are required in which zones, or how much pipe is required. A generic calc program isn't going to tell you all those things, but a radiant heat loss program will. Sometimes certain zones can't be heated without supplimental.

Anyway enough about that. I see you are planning on nailing hardwood flooring down to pine nailers. Check with the flooring guys and see how often they nail the floor down. If you space those nailers too far you won't have much nail surface (and in pine at that). Something to think about.

If I understand correcltyl now. A heat loss calc will tell me what the BTU requirement is for each room, what pipe size I should use, how many coils I will need per room and what temperature I should use for the boiler. This will all add up to a boiler size in BTU's that I will need. Is this all correct? So who to contact about doing this? How much should that cost?

Something to also consider is that this HAS to be a DIY project for me because I can not afford to have a professional do it. I just can not afford 25-30k to do this. I consider this a luxery item in my home as a HVAC would do the job also, just not as well.

Thank you,
Troy

Not exactly. If it's done with a radiant heat loss program, it will tell them all that info. If it's done on a program such as Slant/Fin's baseboard program, then it's just a heat loss calc.

You can use a standard heat loss calc to determine the rest provided you have charts and such to tell you the rest.

I was in your exact same shoes about 4months ago. I learned my leasons the hard way. and would be more than willing to share my mistakes and my knowledge. I would not recomend Radiantec. I myself built my entire house, only subbing out the rough-in plumbing, insulation, and sheet rock. I know a little about construction. If I had to do it over I would spent a few extra $ to work with someone who has done a few systems. The money you spend for knowledge will you say you $ and your sytem will work well. I would estimate it cost me about $2,000 in mistakes.

Troy, I think your budget may not be enough, even you doing it. Be prepared to spend more. there is not point nickel and diming your heating system.

As far as who can calc this for you. Use the find a contract search either here and or @ heatinghelp.com and hire a radiant profsional or engineer to do it.

You should be able to do the radiant system for less than 10k with carefull planing. ac would be additional. Let me know if I can help...Eric

I am trying to keep it within my budget. If I can not I will simply not do this at all. This is a luxury item for my house build and something I really want to do, but the rest of the house is important also. I will still have to have a full AC system in the house, and this can add to the heating need of radiant if needed, so I really do not need the radiant system. I just hope it can work out within budget to make it affordable. I know it can be the best system. It is sad that the best system is so expensive to have for a common person who is not rich.

I called a local place that would do the gypsum if I wanted to go that route and that would cost me $6200. I can not afford that at all. I think the only real way to do it is the sandwich dry method as of now and we will have to see the final cost of that. I consider my labor free

Thanks for all the help.
Troy

Troy,

You can run the numbers but I believe Theo G is right. You will be over your budget dollars when you throw in the AC and duct work.Even with sweat equity it will be tight,hate to see you skimp to get what you want.

What you can do is plan for the future, when some dollars come your way. Lay your tube in garage and basement per specs. See if your budget dollars will allow for the tubing and material to do your sleeper systems on main floor and upstairs,maybe consider some ceiling radiant where applicable.

Go with your F/A system for now,and in the future when dollars come your way to lash up the boiler, and near boiler piping to tie it all together. The F/A furnace can then be a backup.

I know it sounds a little weird,and I would not suggest this...... But it sounds like you really want the radiant. You want the AC anyway. Once the house is done its hard to impossible to go back and lay the tubing.

The boiler and controls will add considerable dollars to the cost of the radiant system, and you should really have a professional at the very least commission your boiler if not do the controls and near boiler piping also, I don't know your ability,and if not done properly can have adverse/dangerous results.

Others may disagree with my suggestion or may have a different approach. Just helping you reach your goal.

If you are very carefull you could do this as a staple up and normal forced air w no bells and whistles, for example I have installed with out zone valves and controller with valve bodies used as balancing valves. there are lots of ways to economize but a lot of them will prove very expensive. At least install tube and insulation in basement, garage, and 2nd floor. I find it funny that people compare a full featured radiant system to a single or 2 zone system FA that doesnt heat garage and does a very poor job of heating basement. I've had more people tell me that radiant heat is one of the last things they would give up..Eric