In-Floor Radiant Hot Water Heat

[Dusty Rhodes]

Seems like it would be an inefficient system to me. Why heat the water from a "boiler" designed to heat water to high temperatures, then add cold water to cool it to 120 degrees so it could go through the floor to give up whatever heat 120 degrees could muster, then send that even colder water back to a "boiler" to reheat it well past 120 degrees and start the process all over again. My simple mind says you are wasting wood. What am I missing here? I am having trouble figuring the logic of it all.

 

[Mac88]

May have to bring a trailer of that hedge with ya. Help make friends with the neighbors.

Hmmm...about 4800 lbs/cord...4 cords would put me right at gross weight...that's about $500 worth of diesel...maybe we'll stick a few splits in the trunk the next time we're up that way, just so you can "test the waters" so to speak. :msp_biggrin:

 

[Mac88]

Seems like it would be an inefficient system to me. Why heat the water from a "boiler" designed to heat water to high temperatures, then add cold water to cool it to 120 degrees so it could go through the floor to give up whatever heat 120 degrees could muster, then send that even colder water back to a "boiler" to reheat it well past 120 degrees and start the process all over again. My simple mind says you are wasting wood. What am I missing here? I am having trouble figuring the logic of it all.

That's why the question was presented. There's a broad range of knowledge on this site. I'm sure there are several folks here that have done it already.

 

[kevinlar]

I read a lot about Warmboard. plywood that is laminated with aluminium and foam. It's a little pricey but would do the job.

 

[Mac88]

I read a lot about Warmboard. plywood that is laminated with aluminium and foam. It's a little pricey but would do the job.

I'll look into that. Thanks.

 

[JHctRednek]

Seems like it would be an inefficient system to me. Why heat the water from a "boiler" designed to heat water to high temperatures, then add cold water to cool it to 120 degrees so it could go through the floor to give up whatever heat 120 degrees could muster, then send that even colder water back to a "boiler" to reheat it well past 120 degrees and start the process all over again. My simple mind says you are wasting wood. What am I missing here? I am having trouble figuring the logic of it all.

If the return water is the "cold water", your not adding cold water to your boiler water but adding hot water to your zone water to keep the water in the zone at 120 degrees so that the mass of the floor can reach temp. The great benifit is that once the mass of the floor reaches temp it will hold that temp for a very long time and all that you have to do is maintain it. In a normal baseboard system you are transfering the heat in the radiator to the air by convection across the fins of the baseboard radiator.

Think about how long a rock you put next to the fire when camping holds heat, vs how fast the tap in your sink is back to room temp after you run hot water through it, its kinda the same idea.

Hope that makes sense

 

[Dusty Rhodes]

Should just keep my nose out of it. Do not really understand how the system works. On the surface it seemed inefficient to me. I have a friend who added onto his house. He already had an OWB and heated the old part of the home with baseboard hot water. When he added on he installed radiant heat in the floor of the new addition and added a mixing valve to cool the return water down to 120 before it went into the pex in the floors. I do not know all the details of what his setup was exactly but he has had a royal pain trying to get the system to work properly and was going through more wood than he expected. Guess because he is trying to mix two types of systems. I apologize, especially to Mac. Without further hoopla, I'll get my ignorant arse out of here. Good luck Mac with finding the right system for your place in Maine. Lived their for 14 years and really enjoyed almost everything about that State. Depending on where you settle, be prepared for some frigid weather. As you know, the closer to the coast, the more your temperature will be moderated by the ocean in the winter. The further west and north you go, the colder it will be. Where I lived we averaged 168 inches of snow per winter and it could get bitter cold with ambient temps reaching -30. But then again, I was about as far north as you could get and still be called an American.

 

[woodman6666]

Mac88 looks like im a little late to the party. Anyway here is what I have learned after building quite a few large boilers and installing heated floors in several of our buildings. First and foremost, most plumbers and hvac guys wont be much help especially if you want to keep things simple. If I were you I would lay a foil back material on existing concrete then half inch pex (just the cheap stuff from menards but you will have to buy or borrow the pex crimp ring tool) keep all loops the same length run them anywhere from 12-18 inches apart run your hot supply straight to outside walls then lose it back to the return header. Now put an adjustable aquastat on your boiler and set it at 130-140 or so this will be enough to give you hot enough water at your water heater and also plenty hot for your floor now either put a zone valve that is operated by a thermostat or a pump that will turn on and off with a thermostat I prefer to pump constantly and just send it to the floor when thermostat is calling then when satisfied just send back to the boiler. Doing it this way you will not need a mixing valve (which I hate with a passion) they are nothing but trouble and you dont need them. There will be all kinds of people that will tell you that you need one or this that and the other thing will happen. but I can say with experience that they are more trouble than they are worth. this is the simplest way to do what you are asking about. Feel free to pm me if you want to. Good luck

 

[Mac88]

Without further hoopla, I'll get my ignorant arse out of here. Good luck Mac with finding the right system for your place in Maine. Lived their for 14 years and really enjoyed almost everything about that State. Depending on where you settle, be prepared for some frigid weather. As you know, the closer to the coast, the more your temperature will be moderated by the ocean in the winter. The further west and north you go, the colder it will be. Where I lived we averaged 168 inches of snow per winter and it could get bitter cold with ambient temps reaching -30. But then again, I was about as far north as you could get and still be called an American.

Not necessary, Dusty. I appreciate your take on it. I've always believed that one can never have too much information. I figure the more opinions I get the better off I'll be. It might not work out as planned and I'll have to come up with some other idea.

The Mrs folks live up near Rockland. Relatively mild as compared to the "far north". I lived in far upstate NY for several years, 30 miles from Canada. Believe it or not, it does get down to -40 from time to time.

Mac88 looks like im a little late to the party. Anyway here is what I have learned after building quite a few large boilers and installing heated floors in several of our buildings. First and foremost, most plumbers and hvac guys wont be much help especially if you want to keep things simple. If I were you I would lay a foil back material on existing concrete then half inch pex (just the cheap stuff from menards but you will have to buy or borrow the pex crimp ring tool) keep all loops the same length run them anywhere from 12-18 inches apart run your hot supply straight to outside walls then lose it back to the return header. Now put an adjustable aquastat on your boiler and set it at 130-140 or so this will be enough to give you hot enough water at your water heater and also plenty hot for your floor now either put a zone valve that is operated by a thermostat or a pump that will turn on and off with a thermostat I prefer to pump constantly and just send it to the floor when thermostat is calling then when satisfied just send back to the boiler. Doing it this way you will not need a mixing valve (which I hate with a passion) they are nothing but trouble and you dont need them. There will be all kinds of people that will tell you that you need one or this that and the other thing will happen. but I can say with experience that they are more trouble than they are worth. this is the simplest way to do what you are asking about. Feel free to pm me if you want to. Good luck

Interesting concept. Right now it's an "on paper" work in progress. The layout would ultimately depend on the building we end up with. I did some research on mixing valves and have a lot better idea of how they work in radiant systems. I'm thinking LP for hot water during the warm season, but that could be tied into the boiler during winter. We would have LP anyway, for the cook stove. Thanks Woodman for your input.

 

[Dusty Rhodes]

Your a gracious man Mr. Mac. Good luck with you move and planning of an install. For me, planning things out is half the fun. The Rockland Area is beautify, heck the whole state qualifies for that statement. I am afraid you will come up dry though on burning your beloved hedge. Sugar maple was my staple wood in Maine and I used and appreciated beech and Yellow birch as well. You may be far enough south in the state to score some oak but do not know for sure. It certainly was not growing in the Caribou area were I lived. if you could come up with a design for a potato furnace you'd be all set for Maine

 

[Mac88]

Thanks Dusty. Taxes are too high for my blood along the coast. Even the lobstermen are suffering. Yea, we're gonna miss our hedge, but oak is pretty close btu-wise. Seems to be a lot of pines the further north one goes. There's some other stuff up there that I'm not familiar with. But I'm of the mindset that, if it makes an ash, it's firewood. We didn't make it to Caribou, but, on our next trip, we'll probably run all the way up to the Ft. Kent area for a look around. Funny you mentioned potatoes. We almost bought a 50 lb. bag, but there was no room in the car for them. Potato stove. Now there's an idea worth pondering. :msp_smile:

 

[Marc]

Not necessary, Dusty. I appreciate your take on it. I've always believed that one can never have too much information. I figure the more opinions I get the better off I'll be. It might not work out as planned and I'll have to come up with some other idea.

The Mrs folks live up near Rockland. Relatively mild as compared to the "far north". I lived in far upstate NY for several years, 30 miles from Canada. Believe it or not, it does get down to -40 from time to time.



Interesting concept. Right now it's an "on paper" work in progress. The layout would ultimately depend on the building we end up with. I did some research on mixing valves and have a lot better idea of how they work in radiant systems. I'm thinking LP for hot water during the warm season, but that could be tied into the boiler during winter. We would have LP anyway, for the cook stove. Thanks Woodman for your input.

Although I don't share Woodman's distaste for mixing valves, particularly ones from reputable companies, it is good to get a range of possible solutions. I heard you mention you might be moving to Maine (ayuh) and there is a guy on the ********** forums named Brian who owns a small engineering outfit in NH that designs residential heating systems, specializing in IWB applications. I think he normally hangs out in the Boiler Room subforum, and usually volunteers advice there. He might be a good one to ask advice from.

 

[woodman6666]

As far as mixing valves go if you dont set your boiler higher than you need your water in your floor why run them? Anyway Mac one more thing if you end up going over existing floor you may want to look at Farmtek they probably have a product that would work well.

 

[Mac88]

As far as mixing valves go if you dont set your boiler higher than you need your water in your floor why run them? Anyway Mac one more thing if you end up going over existing floor you may want to look at Farmtek they probably have a product that would work well.

I'm not sure how I would run a wood fired boiler to maintain a water temperature in the 80-90 degree range.

 

[Guswhit]

Just jumping in again to give some scenario's I have first hand experiance in. The 2 I have acutally been in after they were finished(1 house and 1 farm shop), were done by 2 differant contractors, but they both have the circulating water temperature in the concrete floors set at 104 degrees. They run their outdoor CB OWB's at 175-185 range. The thermostats are wall mounted and as they call for heat it actuates mixing valves to allow for higher temperature water from the boilers to get to the floor loops. They are very very nice systems! I especially like the shop, as I get to work in it sometimes! Laying on the warm floor is just unbelievable to work on in the winter!

 

[Mac88]

Thanks Guswhit. More food for thought. It's been a good long time since I messed with hot water heat. I've got a lot of catching up to do.