Any experience with radiant heat?

[StoneHeartFarm]

Patrickg

Another option would be to build an outdoor wood burner and pump the heat in through conventional heat ducts. Of course, it eliminates the in slab heating, but you don't have the heat lag and can burn waste wood and paper scrap for part of the heat which helps keep the ol homestead cleaned up. So far, I've only seen these units heating residences, not garages or barns, but I don't see any reason why it wouldn't work. The one I helped build is currently suppplying a 1.5 story, earth contact, 3 bedroom home. Sole heat source and seems to be doing well. Construction is simple, but labor intensive.

SHF

 

[cowboydoc]

Patrick,
If I get my house sold and build over at the other place I was going to go with geothermal. Tell me more about what you think is the best way to go about that please.

Thanks,

 

[utahmule]

cowboydoc,

I'm a Civil Engineer and have done a couple of Geothermal installations, so if I can help I'd be glad to do so. FYI, Geothermal is like any other heat source in that you can use it for radiant, forced air or any number of other delivery systems. Hope this helps.

Eric

 

[cowboydoc]

Eric,
I would love to know anything you can tell me about what the best way to do this would be. I've been told that heating and cooling are $50 a month. True? Also I know there are a number of ways to install them as well. What do you feel is the best way? I'm not limited by my options at the new place. Thanks alot.

 

[patrickg]

SHF, He isn't in Rome but he could still do what the Romans did or at least a modern adaptation. Put some hollow clay pipe in the floor or place a series of blocks side by each such that you can see daylight all the way through. Make the whole sub floor out of them. Pour a couple three or four inches of concrete on top to bond everything together and provide a good smooth floor. Lets say the blocks are laying long ways N-S so the chanels run E-W. At the east and west ends you make a manifold to connect all the passages together. Now you pass the combustion products through the floor, heating it. Combustion chamber needs to be low and you need a stack on the output end to help produce "draw". If the combustion chamber is well thought out you should be able to burn shredded junk mail. Not enough junk mail? Well, it sure is easy to fix that. Put in a row of mailboxes (15-20 should be enough) tilted up at a 30 degree angle with a chute out the back like an enclosed laundry chute, all feeding into a collection box. Get addresses for all of them xxx-1, xxx-2, etc. Subscribe to all the junk mail. Get a heavy duty paper shredder to process the mail. Likely it could be automated. An auger feed based on the pellet stove could be thermostatically controlled for convenience. I don't think construction costs would be a big deal and it should reduce the heating bill a lot. This could go off grid with P-V to operate the auger and thermostat should you want more energy independence.

Oh yeah, use a catalytic afterburner to help ensure complete combustion and not put a bunch of gunk in the blocks. This is an adaptation of Roman style central apartment heat (from the time of the Ceasars) and a modern passive solar home design (several of which were built, instrumented, and worked quite well). The passive solar design uses a rectangular shape with lotsa glass on the south side. Sun heating the slab floor starts convection currents up out of the manifold nearest the sun with cool air falling down on the north side manifold. The air moves through the chanels in the floor and comes out at the south side again. In operation there is only a small temp diff from the north to the south side of the floor. A small fan can assist, especially at night when the delta T is reduced as the floor temp north to south equalizes. Properly insulated (double 2x4 stud walls with 8inches of f/g batts, cheap as a 2x6 wall but more efficient) there is little or no additional heat required unless there are long periods of heavy overcast.

Something in favor of hydronics is that as long as you can run the pump (a litle electricity, easily supplied by PV system) and have one or more heat sources (scrap wood burner with heat recovery, junk mail burner, pellet stove, gas boiler, solar water heater, whatever) you can heat the floor. The system doesn't care how it is heated, just that it is heated.

Patrick

 

[StoneHeartFarm]

Patrickg

Actually, we didn't think of that /w3tcompact/icons/crazy.gif when I helped my buddy build his. I dont see why it wouldn't work. Am I right in assuming the firebox should be a little lower than the floor? Just to help the draw.

SHF

 

[patrickg]

SHF said: Am I right in assuming the firebox should be a little lower than the floor?
Just to help the draw.

That is what I meant when I said,

"Combustion chamber needs to be low and you need a stack on the output end to help produce "draw"."

But as usual I didn't make it real clear. Once the whole system is drawing it isn't as important but like a syphon which it approximates, you have to get it started. A small blower to force a draft would be real helpful till the system got hot. I'd consider a multi-speed or better a variable speed blower and use it as required, probably pretty fast getting the system up and then throtle back.

Patrick

 

[patrickg]

Richard, Like the civil engineer guy said, Gex is just another way to get heat, how you deliver it is a whole different story. I am becoming an IAQ (Indoor Air Quality) concerned person. I am trying to design an essentially duct free or as duct free system as is practical and still meet my air change, filtration, dehumidification, cooling, and heating requirements. That gives me multiple reasons to favor in-floor hydronic heat. No ducts (breeding grounds for stuff I don't want to breathe) plus ducts are drafty, noisy, scatter dust, and have no aesthetic appeal. Going bare foot is more funner when the floor is warm in the winter.

Some folks put radiant heat part way up the walls but should stay below the "picture hanging zone" to avoid nailing into a tube. Worst location is the ceiling as was used in some electrically heated homes.

Best way to "GO GEOTHERMAL" varies. as does the answer to what is the best tool. If you have or will build a pond near the structure then a coil of PEX in the bottom of the pond can be real good. If you have an artesian well or plenty of cheap water you could go "open loop" and put well water through the heat exchanger then discharge the water, hopefully into a pond or series of ponds, irrigation system, or whatever (just wasting it bothers me). If you have the real estate and trenching isn't too hard, a long deep trench to bury PEX can be a good thing. Limited real estate? Drill a well just for placing heat exchanger loops of tubing. That just about exhausts the "standard" methods of installing the ground loop. Get out a sharp pencil (or spreadsheet software) and work out the highest SEER setup that will pay for itself over time in energy savings. Electricity is not likely to get cheaper over the installed life of your HVAC system.

The radiant part is prety cut and dried too. There are published design guidelines for in slab radiant, under wood floors, etc. An earth sheltered home builder's home/office that I toured last week was heated with in-slab hydronics
A N D he had regular carpet pads and carpeting. If you insulate under the floor a lot better than the pad and carpet insulate A N D you can supply the needed BTU's at the required elevated temp then it still works fine. Man's claim was that he too loved to go barefoot in the house in winter and the warm carpet felt delicious.

I like radiant heat because there are no ducts (good news) but the bad news is that there are no ducts...available for cooling and dehumidification in summer. Don't figure on radiant cooling unless you have to run a HUMIDIFIER in the summer because it gets too dry. Cooling a slab sufficiently to lower the radiant temperature as required for in-house comfort will put floor and any coverings below the dew point in temperature and will have condensation forming. Wet slab or floor coverings is a bad thing and will grow stuff you don't want.

Consider fan coil units charged with chilled water from the geothermal heatpump. I suggest variable speed blowers on these so that when you need dehumidification more that max cooling you can slow the air handlers down to increase dehumidification while reducing total BTU's removed. Also check into installing heat pipes with the fan coils as an adjunct to dehumidification. Do net search on "heat pipe". Your looking for some outfit in Florida with an oriental gentleman as the principal. They have practical applications of the technology. Really boosts dehumidification and has no moving parts to wear out and consumes no electricity directly. I just checked your bio. Midwest mean high humidity so you should be interested in heat pipe dehumidification applications.

That's about it without writing a book. I am up way past my bedtime so I might not be functioning at peak efficiency, just typing what comes to mind.

Patrick (An honors graduate of the Christopher Columbus School of Touch Typing where you learn to look for, discover, and land on the keys...one at time!

 

[StoneHeartFarm]

Patrickg

You're hit on probably the most important feature of radiant heat. Flexibility. The radiant tubes/radiators are merely the conductors and not the source of the heat. This is where the flexibilty comes in. The heat SOURCE can be virtually anything capable of providing enough hot water. (Some sources, such has electric water heaters may not do a great job or last a long time). It can be geothermal, a water heater, a gas or oil fired boiler, a wood or pellet fired boiler, solar, etc. This readily allows for a multi-fuel system. Adequate insulation and multi-fuel systems could be an important selling point at some time in the future.

SHF

 

[patrickg]

SHF, Yet another trait we share, "preachin' to the choir".

After the design considerations for hydronic heat, there is still the cooling, dehumidification, ventilation/air changes, filtration dimension to the problem. Usually little or none of the equipment involved in the hydronic heat distribution is useful in the above air handling involved tasks as the air handler requirement is not a part of the equation with hydronics. That is why I am considering chilled water distribution to zone controlled fan coil units for cooling.
I have contacted a manufacturer of baseboard heating fan coil units designed to mount in the kickspace under cabinets and heat with circulated hot water. For a small one-time engineering charge for CAD documentation and extra cost of brazing in some condensate drain fittings and extra powder coat for water resistance (condensate) they will build units for me in low volume (onesies twosies or so where or so could be as many as 10 or more) This will allow me to use the same pumps and some of the same plumbing for cooling as for heating. Still I will nead a whole house ventilation system with a balanced heat recovery system for air changes and filtration.
I expect that my dehumidification requirements will exceed my cooling requirements so I will need to engineer in extra dehumidification so I don't waste a lot of expensive KWH chilling the house while trying to dehumidify. The house ends up cooler (at great expense) than you need just trying to dehumidify sufficiently. At RH levels at or below 50%, lots of little creatures don't reproduce very well if at all and many die in a fairly short time. Even if they live for a week or two (without reproducing) they will be history before long. Moderately low RH (40-50%), besides promoting better health, feels comfortably cool whilethe air temp is several degrees warmer than wold be required with higher RH levels.
Since most practical dehumidification mechanisations have been compressor/refrigerant systems there is often not that great a savings over just runing the AC. Well, there are now much more efficient mechanical dehumidifiers and a clever no-extra-electricity method. I am attracted to the no-extra-electricity method. This employs a special heat exchanger, actually two finned heat exchanger assemblies connected by heat pipes. "Brief" digression follows.

Tech note: Heat pipes are typically thin walled copper tubes lined inside with a material having good capilary action, wetted with a liquid solution, often proprietary, that vaporizes well at the operating temperature to be employed. I think ammonia in water was used at one time. This device "pipes" heat from one end to the other of the tube quite efficiently, much much more efficiently and quickly that just a copper tube or a copper rod. In brief,it functions thus: As heat energy is adsorbed at one end, the liquid in the inner lining at that end is vaporized. Molecules of vapor propogate toward the otherend, taking the absorbed heat of vaporization with them, at just under the speed of sound, around 700 mph. As these molecules arrive at the other end and contact its cool environment, they condense back to liquid giving up their heat of vaporization (heating that end of the tube). the liquid is transported back towards the original end where it started out by capilary action as that end is drier (liguid is being evaporated there, drying it) and away from the condensing end that is gaining liquid and its capilary material is being saturated as liquid condenses.
This action repeats continuously as long as heat is added to the one end and removed from the other. There isn't anything to wear out (molecules usually don't wear out due to repetitive evaporation and condensation or rain would have worn out all the water a long time ago.)
OK, an interesting parlor trick or AMAZING science fact but how does it dehumidify with no additional expenditure of electricity? 1. Bend the heat pipes into a U shape. 2. Put fins on both ends to increase surface area in contact with air. 3. put an air conditioner's evaporator (the finned coil that gets cold) in the middle of the U.
Air flows past the first side of the U into contact with the evaporator and is chilled (this is what air conditioners do). This cold air continues past the second side of the U. When this chilled air cools the second side of the U that initiates condensation of the material inside the heat pipe. The warmer air coming into the system past the first side of the U gives up heat to the vaporizing material inside the tube. This pre-chills the air coming into the evaporator which chills that air again (making for an accumulated delta T greater than if the heat pipe wasn't employed). The doubly chilled air sheds much of its water since dehumidification is a function of the delta T, bigger temp drop is more water condensed out. As the doubly chilled air passes over the second side of the U it is warmed up to about what it would have been if only the standard air conditioning was used, i.e. no heat pipes. There is no net gain or loss of heat energy but temporarily at the right moment the moist incoming air is chilled much lower than it would have been without the heat pipes, thus effecting greater dehumidification than with just the standard air conditioning approach.
As no additional electrical energy is used (ok there is a tiny bit more aerodynamic drag blowing air through the extra fins) yoiu get a bunch better dehumidification and the only cost is a one-time purchase of equipment that doesn't have conventional moving parts and doesn't wear out.
If you are really into the physics of this you know that I glossed over the topic of latent heat. Except for the heat generated by running the refer unit and the circulating fan there is no heat created or destroyed, no magic, just clever thermodynamic manipulation to derive a benefit. If you consider the total heat energy of the incoming air stream and account for the heat in the condensate being thrown away (or used to top off the pool since it is distilled water) and the SEER of the refer etc it all balances out. I think there is a great future for applications of heat pipes. I first saw them demonstrated at the Long Beach Convention Center in about 1972 at an electronic engineering conference/exposition. This technology was used in the F-111 swing wing fighter bomber to get heat out of internal electronic packages. There are small heat pipe systems currently being sold as coolers for high speed Pentium processors.

Patrick (Again, if you joined the Tractorbynet forum as no-credit or pass-fail, this is not on the quiz.)

P.S. If there are any serious/practical cooling and dehumidification schemes/suggestions that are compatible with hydronic heating equipment, please put me out of my misery and give me a clue.