radient under carpet?

[pulse]

I am just starting to get my feet wet here with the thoughts of adding radient throughout the house. I tried a search and did not have much luck so I thought I would just ask. How does (stapel up?) work under carpet as a finished floor? I assume it would not be as good as tile or hard wood but my living room and bed room are carpet.

 

[jimbom]

My radiant is in concrete covered with sheet vinyl. Since this passes heat to the surface easily, my water temperature is quite low. If you are pushing it through layers of wood and carpet, the water temperature has to be high enough to get the surface of the carpet up to 70 - 85 °F. Since the water temperature is going to be kind of high, insulation below the tubing would likely be necessary. The exact temperature water you would need, depends on your heat load and the combined resistance to heat flow through your floor system. The radiant floor material suppliers have design guides posted on the net.

 

[afblue]

The heat output of a radiant floor is dependent of the heat loss of the structure that it is heating. But as an estimate, if you were to expect the maximum heat output from 8" spacing staple up radiant flooring (2 lines per joist bay) the maximum heat that can be expected is 30 BTU/sqft. Now to calculate the temp water required to do this: Typical R value of Capet with pad is aprox R-1.44. Using my Modern Hydronic heating manual, I calculate 174F water temp to maintain 85F floor temp at that heat output. The next thing to consider is, the conservative rule for insulation in the joist cavity is 10 times the R vaule of the floor covering. Therefore R-14+
Staple up Radiant under carpet is doable, but it has alot of factors stacking up against it that make it somewhat undesireable.

Things to compare this to using the same caculations above: hardwood 3/8" R 0.52 water temp 145 3/4 Hardwood R1.05 water temp 160F cermic tile on thinset, R0.30 water temp 137F

These #s will reduce if your heating load is less than 30BTU/sqft.
The next thing to start factoring is what heating source/design you have or plan on using. If its the use of a thermal storage system, radiant under carpet is essentially worse than baseboard because of the water temp it requires.

 

[Grover59]

I will say this, I did put staple up in my house and in my living room I have carpet and foam under that. I did two runs of half inch pex in each bay, and made diffuser plates with aluminum flashing. It works and it works very well, yes I have to run more temp in the area with carpet however it is not that bad. I do have storage and my storage works fine, if the storage goes below 140 then I may not be able to keep up with the demand when it is very cold, however it still heats the room and is comfortable heat.
You can notice the difference from my kitchen to my living room and the carpet is why, however I love the comfort of the floor heat. You must use diffuser plates and you must insulate under the pipe it makes a big difference, very big difference, my floor is very responsive for staple up.
This past winter I left the floor temps at 70 degrees, and the room temp would be around 66 to 68 degrees and comfortable, if I had a really cold day or night the room temps may go as low as 62, but we were still comfortable. When I started a fire I would let the baseboard take it up the rest of the way if we needed it. If I set the floor temp to 80 the room would go to 70 or more and feel a little stuffy, it's a different kind of heat, it is just more comfortable. My tank temp would go from 165 to 120 I just love radiant floor heat.

Steve

 

[pulse]

I have so many questions I don't even know where to start. About the only thing I know about radient heat is how good it feels. I am not however planning on relying on only it to heat the house. My thought was the radient would give me a low base heat (keep the floors at 68-70), then use the water/air forced air I already have to raise the house temp if I wanted. My thought was to run staple up everywhere I could. Possibly (radiators/panels) where I couldn't. Staple up would not work under the older part of the house where there are multiple layers of subfloor/hardwood.

For a little background, I am currently using a owb that holds 150 gallons of water. I have no problem keeping the house at 73 all winter with water temps from 135-165. My house is a mix of updated 100 year old farm house, and new construction (2008) The original house was about 1500 sq ft. The total now is 2800 sq ft living area with a full unfinished basement that maintains around 60ish. I have A LOT (30) of big (3x5) windows and the main floor ceilings are 9 feet. 2 of the bedrooms are vaulted ceilings, in other words I have a high heat load. The best I can figure is I average 35-40k btu/hr during the winter season. I have not used a heat loss calculator, but I have let the oil furnace run for a couple days back in January and watched how much fuel it used.

The other concern I have is getting enough btus/water to the house. Does it make sence to use the water/air hx as the primary then route it to a water/water hx that would service the radient system. I understand that if the primary was running there would be little left for the secondary hx but as I stated the radient would only be used to maintain temp. Anyway I am getting way to far ahead of myself.

 

[afblue]

You can certainly use the radiant for comfortable floors, then just use the force air HX for suplemental heating. If the system is desgined and insulated correctly, you will do very well using it to heat the house for 95% of the year, you just might need to have the forced air to kick on to suplement on the coldest days of the year. The numbers i supplied you with are theoretical design load #s which are esstentially coldest day of the year situations, and if you didnt have a back up heat emitted. Does your water/Air HX run on a water glycol solution straight from the OWB? Essentially you can design a radiant system with a plate heat exchanger to supply the floors. Or you could install a 3 way valve that diverts the heat to the radiant or to the Forced air Exchanger.

I would do a heat loss calculation on your house to see exactly where you are at and to see what specific parts of the house loose the most heat, if your big windows are in the new construction which can be radiant you are golden becuase thats your biggest heat loss. But quick math, for that time when you calculated your heat load to be 35-40K/hr for 2500sq ft. Thats 15 BTU/ft^2/hr so The equation is: Water temp=room temp+ (btu load per sq ft/k) in the case of staple up radiant 8" spacing, with carpet k=.29 So 68+(15/.29)= 119.7F which is totally doable.

 

[Sawyer]

The heat output of a radiant floor is dependent of the heat loss of the structure that it is heating. But as an estimate, if you were to expect the maximum heat output from 8" spacing staple up radiant flooring (2 lines per joist bay) the maximum heat that can be expected is 30 BTU/sqft. Now to calculate the temp water required to do this: Typical R value of Capet with pad is aprox R-1.44. Using my Modern Hydronic heating manual, I calculate 174F water temp to maintain 85F floor temp at that heat output. The next thing to consider is, the conservative rule for insulation in the joist cavity is 10 times the R vaule of the floor covering. Therefore R-14+
Staple up Radiant under carpet is doable, but it has alot of factors stacking up against it that make it somewhat undesirable.

Things to compare this to using the same calculations above: hardwood 3/8" R 0.52 water temp 145 3/4 Hardwood R1.05 water temp 160F ceramic tile on thinset, R0.30 water temp 137F

Are these R-values allowing for a sub floor such as 3/4" plywood/OSB or does that also raise the r-value if the tubing is in the joist space?

 

[Grover59]

This is how mine is, I have about 300 feet of radiant in the kitchen bathroom area and 300 in the living room and dining room, they are two separate zones with separate floor temp controls, one has carpet the other one does not. I also have a modine heater that I boxed in and made a forced hot air duct that blows in my hallway and pulls form my living room, this was to be temporary but it worked so well I decided to keep it. The modine is also a separate zone so it too has it's own thermostat on the wall in the hallway.
These three zones pass through a flat plate hx, and then I have a loop that comes from my tank that passes through the other side of this hx, and also passes through another hx for the domestic hot water. I use one pump for the three zones, with 3 zone valves one for each zone. I also have one pump for the loop that pulls from the tank to the hx and back again. So when any one of the three zones call for heat, two pumps will start the one pulling from the tank and the one that pumps to the three zones, however only the zone valve for the zone requesting heat will open up, unless more then one call for heat.
So as long as the floor heat left at 70 keeps the thermostat in the hallway for the modine satisfied then the modine will never come on. I also have some strange things I do with motion sensors that prohibit the modine from running if no one is in the house, helps to save on btu's.

I would not hook up your forced hot air in series with your floor heat make them separate zones.

Steve

 

[pulse]

The zones wouldn't be in a series, but the hx's would be. I thought the water would pass thru the forced air hx first which has its own centraly located thermostat. Then it would pass through a plate hx that would have probably 4 different zones all on there own thermostat. I figure I could adjust the water temp for each zone with a mixing valve to allow for lower water temps where I could get away with them. If the radient couldn't keep up the forced air would run which I already know has no trouble bringing the house to temp. Wow this is sounding complicated as I am writing it, am I making something simple overly complex?

 

[Grover59]

I see what you mean, it sounds like that would work ok, I did not use mixing valves I was going to but it just seem to add a lot more expense and plumbing so I just run what ever the temp is through the floor and I have a sensor in the floor that shuts the zone down when it comes up to temp, very simple.

Steve

 

[heaterman]

Air Force............I like the way you think. Good solid info right there.

Buying Siggy's book, Modern Hydronic Heating is probably the single best investment a person contemplating a DIY installation could possibly make.
Obviously the stuff is not rocket science because even I can understand it. It does however leave less room for error than a scorched air system and there are countless ways to screw up. Color inside the lines and a hydronic system will always be more efficient and capable of far more comfort.

 

[heaterman]

I am just starting to get my feet wet here with the thoughts of adding radient throughout the house. I tried a search and did not have much luck so I thought I would just ask. How does (stapel up?) work under carpet as a finished floor? I assume it would not be as good as tile or hard wood but my living room and bed room are carpet.

What part of our cold and wet state are you from?

afblue has good info posted in his reply.

 

[afblue]

Air Force............I like the way you think. Good solid info right there.

Buying Siggy's book, Modern Hydronic Heating is probably the single best investment a person contemplating a DIY installation could possibly make.
Obviously the stiff is not rocket science because even I can understand it. It does however leave less room for error than a scorched air system and there are countless ways to screw up. Color inside the lines and a hydronic system will always be more efficient and capable of far more comfort.

Yeah I got tired of trying to get equations off the internet, and sticking things together till it "looks right" was not what I was willing to do when I build my system so the book has been a great and interesting read. Some of it was like I was back in college studying engineering so its way overkill, but the background and theory is completely solid. So I guess what I get from it is that I will be able to build a system that is alot more efficient not just in heat distribution and sizing, but low power consumption and outdoor reset capable too.

 

[pulse]

I am just starting to get my feet wet here with the thoughts of adding radient throughout the house. I tried a search and did not have much luck so I thought I would just ask. How does (stapel up?) work under carpet as a finished floor? I assume it would not be as good as tile or hard wood but my living room and bed room are carpet.

What part of our cold and wet state are you from?

afblue has good info posted in his reply.

I am in South West lower near South Haven. You sure got the cold and wet part right, but forgot the white. We had 4 inches of snow on the ground here Monday, what a spring! The only good thing that happened this week was I got my turkey Wednesday morning.

 

[heaterman]

I am just starting to get my feet wet here with the thoughts of adding radient throughout the house. I tried a search and did not have much luck so I thought I would just ask. How does (stapel up?) work under carpet as a finished floor? I assume it would not be as good as tile or hard wood but my living room and bed room are carpet.

What part of our cold and wet state are you from?

afblue has good info posted in his reply.

I am in South West lower near South Haven. You sure got the cold and wet part right, but forgot the white. We had 4 inches of snow on the ground here Monday, what a spring! The only good thing that happened this week was I got my turkey Wednesday morning.

The snow/ice really shut the toms down up here. Not much happening except getting colder than we do opening day of rifle season every morning. Cadillac/Houghton Lake area.

 

[bigburner]

The snow/ice really shut the toms down up here. Not much happening except getting colder than we do opening day of rifle season every morning. Cadillac/Houghton Lake area.

Seams to be fewer birds here this year, most every one has gotten one. [15 to date] No book birds, but some nice ones.