In floor heating vs. radiant vs. forced air in shop??

[patrick_g]

This is quite interesting info, for both shop and home.

I am assuming that there would be no cooling benefit from radiant floor design. Meaning, in the summer, run the tubes instead of through a solar collector, through a pond or underground.

I have been reading a lot lately that cooling a house is more of a concern to architects than heating (in terms of cost reduction / energy efficiency).

So, what about a more energy efficient cooling? I would think this is just as important as the radiant heat in the winter.

Dehumidification is an important facet of comfort cooling of occupied spaces.

Radiant cooling of a slab (to act as AC) will require temps near or below the dew point which will promote mold if not make puddles on the floor not unlike the outside of an ice tea glass. Carpet or rugs will get squishy wet.

There are radiant cooling approaches that work. Imagine if you will a pipe of a few inches in diameter cut lengthwise in half and mounted near the ceiling with the open (concave) side up. A smaller diameter pipe is mounted more or less concentric to the split pipe. The smaller pipe circulates chilled water (much cooler than the ground or a pond, more likely chilled by a heatpump.) The warmest most humid air in a room without a stirring fan is near the ceiling. This warm humid air is cooled in contact with the smaller pipe and water condenses out on the little pipe and drips into the larger pipe where it drains to wherever (garden, flower beds, ...) This cools the air and dehumidifies.

If you chill a large portion of the spaces envelope, say the entire ceiling, but do not approach too closely to the dew point you can seriously reduce the effective temperature of the radiant environment and people will feel more comfortable. It is most likely a small compressor unit will have to run with a high duty cycle to do some serious dehumidifying using the latter approach. There are some suppliers of capillary tubes designed to be embedded into a plaster ceiling for radiant cooling.

Cool tubes (pipes buried underground) to cool ambient air prior to being introduced into the space can be effective, especially in sufficiently northern lattitudes where deep soil temps are pretty cool. Here is south central Oklahoma our deep dirt temp is about 62.5F and works well with a geothermal heat pump but would not be optimal for cool tube use. Better to use an HRV or an ERV in these parts.

I had an idea for dehumidification coupled with AC to achieve a ductless system for a great room or similar, a wall designed as a sculpture in concert with a metal sculpture above a shallow pool. The chiller unit chills the wall and metal sculpture till they frost over in a beautiful and dramatic effect (especially with proper lighting) then a flash defrost cycle which has chunks of ice falling off the sculpture dramatically into the pool and sliding down the features of the "Cool wall.) Excess water drains from the pool. radiant temps are lowered and there is dehumidification.

Pat

 

[Redneck in training]

Dehumidification is an important facet of comfort cooling of occupied spaces.

Radiant cooling of a slab (to act as AC) will require temps near or below the dew point which will promote mold if not make puddles on the floor not unlike the outside of an ice tea glass. Carpet or rugs will get squishy wet.

There are radiant cooling approaches that work. Imagine if you will a pipe of a few inches in diameter cut lengthwise in half and mounted near the ceiling with the open (concave) side up. A smaller diameter pipe is mounted more or less concentric to the split pipe. The smaller pipe circulates chilled water (much cooler than the ground or a pond, more likely chilled by a heatpump.) The warmest most humid air in a room without a stirring fan is near the ceiling. This warm humid air is cooled in contact with the smaller pipe and water condenses out on the little pipe and drips into the larger pipe where it drains to wherever (garden, flower beds, ...) This cools the air and dehumidifies.

If you chill a large portion of the spaces envelope, say the entire ceiling, but do not approach too closely to the dew point you can seriously reduce the effective temperature of the radiant environment and people will feel more comfortable. It is most likely a small compressor unit will have to run with a high duty cycle to do some serious dehumidifying using the latter approach. There are some suppliers of capillary tubes designed to be embedded into a plaster ceiling for radiant cooling.

Cool tubes (pipes buried underground) to cool ambient air prior to being introduced into the space can be effective, especially in sufficiently northern lattitudes where deep soil temps are pretty cool. Here is south central Oklahoma our deep dirt temp is about 62.5F and works well with a geothermal heat pump but would not be optimal for cool tube use. Better to use an HRV or an ERV in these parts.

I had an idea for dehumidification coupled with AC to achieve a ductless system for a great room or similar, a wall designed as a sculpture in concert with a metal sculpture above a shallow pool. The chiller unit chills the wall and metal sculpture till they frost over in a beautiful and dramatic effect (especially with proper lighting) then a flash defrost cycle which has chunks of ice falling off the sculpture dramatically into the pool and sliding down the features of the "Cool wall.) Excess water drains from the pool. radiant temps are lowered and there is dehumidification.

Pat

I read an article several months ago about a guy who cools his house just by colder air from underground. He won a price for most energy efficient home in Iowa. It all depends on an energy flow. If the air isn't chilled to low temperature as in standard AC then you have to make it up by volume. I don't know specific of his set up. Just that it could be done. Maybe he moves so much air that there is stuff flying in wind in his house.

 

[patrick_g]

I read an article several months ago about a guy who cools his house just by colder air from underground. He won a price for most energy efficient home in Iowa. It all depends on an energy flow. If the air isn't chilled to low temperature as in standard AC then you have to make it up by volume. I don't know specific of his set up. Just that it could be done. Maybe he moves so much air that there is stuff flying in wind in his house.

You said the magic (four letter) word, I_O_W_A

Deep dirt temp is significantly lower than around here. Did you read all of my posts on this topic?

I talked about "cool tubes" and how they would work better farther north. You need to handle humidity. The cool tubes need to be able to drain condensation and you need a way to "clean and disinfect them" so they continue to provide mold spore free air. I worked out a method for that.

Pat

 

[woodlandfarms]

Thanks patrick for all the info. We knew about the buried tubes, but never considered the plaster / trough version you have mentioned.

What is a bummer to me is that we have met with a number of architects and they all seem to be behind the times in energy efficient cooling. I guess it is changing now, but with the tanking, I think we are not going to be building for a few years.

 

[Egon]

Some Folks In Coober Peddy have this earth temperature heating cooling thing figured out.

Not only that construction costs may be covered by excavating materials!

Win/win

Coober Pedy Underground Homes: "Dugouts"

There are other locations that offer similar housing ranging from areas in the Saharha, Turkey and parts of Asia to the USA. And lots more that I have never heard off.

 

[patrick_g]

There are other locations that offer similar housing ranging from areas in the Saharha, Turkey and parts of Asia to the USA. And lots more that I have never heard off.

Such as parts of china where entire cities and villages are in earth sheltered housing based on caves in some instances and, in some of the northern agricultural areas, homes built around a sunken courtyard with wings for sleeping, kitchen, etc. These are in the fields with nothing sticking above the undisturbed grade.

A problem with many architects is that they design a building and then install sufficient mechanicals to render it habitable.

I have taken some courses from the AIA (American Institute of Architects), like the AMA but for architects instead of doctors) which were taught by a consulting architect in energy efficient architecture. He is typically hired by building design architects who are concerned with energy efficiency and realize they are not trained and experienced in that niche. I still recall some 35mm slides of his neighborhood in Colorado where the snow on his roof was so very much deeper than any of his neighbors, attesting to the lack of heat loss.

Energy efficient cooling: Lots of strategies ranging from tactics from the old days to modern science. Deciduous trees on the south side of the house to shade it in summer but let the solar energy in during winter. Likewise porch overhangs. I have wide porches on three sides of my house (fourth side (east side) is attached shops and garage so no porches needed or reasonable. Lots of good insulation, tight construction (goal is to make the house so tight your ears pop when someone slams an outside door), High SEER heat pumps, zoning, whole house ventilation where humidity allows, and on and on.

There are heat pipes (very different from cool tubes) which are super efficient at moving heat from one location to another with no moving parts except molecules hermetically sealed inside the pipe. My first contact with them was their application in the F-111 swing wing fighter/bomber where they removed heat from dense internal electronics and shed it at the skin of the airframe. Nowadays small versions are used to cool Pentium processors in some computers, especially overclocked game boxes.

Consider a set of heat pipes formed such that one end of the assemblage is in a heat exchanger located upstream from an "A" coil and the other end of the pipes in another heat exchanger downstream of the "A" coil (evaporator of a compressor based Heat pump or air conditioner. The air leaving the evaporator has been cooled and so cools the heat pipes downstream of the evaporator. The heat pipe's terrific heat conductivity causes the heat at the upstream end of the pipes to be drawn to the downstream end leaving the upstream end cooled. This cooled heat exchanger then pre-chills the air stream before it goes into the evaporator where it is further chilled. Being doubly cooled the temp of the air is lowered more than just a standard evaporator will do and so more moisture is condensed out which dehumidifies much better.

There is no free lunch more or less and energy is not created nor destroyed. As the air flows past the heat pipe's downstream heat exchanger the temp is raised back up to approximately where it would have been had we not added the heat pipes. The advantage is that we temporarily reduced the air temp by a fair margin over "normal" and got better dehumidification. There are no moving parts in the heat pipes except molecules so they don't wear out. There are heat pipe assemblies available off the shelf as packaged units to install on both sides of the evaporator and there are units available packaged with the evaporator included.

Dehumidificatioin is a very important part of HVAC and many (if not most) residential installations are not properly done and are more expensive to operate than neccessary and do not do as good a job as they would if properly designed. The typical HVAC shop has no HVAC engineer, just salesmen and installers who ARE NOT qualified to design a system and frequently do not get it right. Don't take my word for it, read about it via NREL or DoE pubs.

Pat

 

[mjncad]

Some Folks In Coober Peddy have this earth temperature heating cooling thing figured out.

Not only that construction costs may be covered by excavating materials!

Win/win

Coober Pedy Underground Homes: "Dugouts"

There are other locations that offer similar housing ranging from areas in the Saharha, Turkey and parts of Asia to the USA. And lots more that I have never heard off.

But they haven't gotten rid of all the pesty flies in Coober Pedy.

 

[Egon]

But they haven't gotten rid of all the pesty flies in Coober Peddy.

Never having been fortunate enough to visit Coober Peddy I am not aware of the fly situation but having noted it's rather isolated location would think that a proper harvest of flies would be a boon to supplement the protein requirements for the local Inhabitants diet.

The typical HVAC shop has no HVAC engineer, just salesmen and installers who ARE NOT qualified to design a system and frequently do not get it right. Don't take my word for it, read about it via NREL or DoE pubs.

The handling and transfer of Heat was never one of my academic strong points. If I said ouch I new it was either hot or very cold.

 

[mjncad]

Never having been fortunate enough to visit Coober Peddy I am not aware of the fly situation but having noted it's rather isolated location would think that a proper harvest of flies would be a boon to supplement the protein requirements for the local Inhabitants diet.

I haven't been there either; but I saw the Teutels go there on an American Chopper episode and the flies were so thick they were wearing mosquito netting over their hats to keep the little buggers away from their faces.

 

[Egon]

Teutels go there on an American Chopper episode

Maybe that would explain the flies!