"Earth" Temperature Just Below Frost Line

Does "geothermal" have to mean pipes and pumps installed below frost line, and full of fluid?

No, to me Geothermal means (in its simplest sense) 'useful temperature difference, the larger the better'.

You cannot accomplish much work when the temperature difference is small regardless of the reference temperature. A few degrees isn't much of a difference when comparing frozen ground to cold air.

Hi, thanks for your post, this differential temp that exists every day, no matter where you are or what time of year it is, interests me. Couldn't the foot print of a home utilize this much better ? I mean, if some more money was put into the foundation plan at the start of construction, a solar footprint could be created, which would keep the house warmer in the winter, and cooler in the summer, because of this direct contact with & IN the earth, and NOT having any moving parts. The backup heating and cooling would be left for the owners and contractors to accomplish. 56 f is warm and cool at the same time, and wants to stay that way, am I right? So if you built a home more connected to the planet, and use in floor heating/cooling, (56 f), would not it save quite a bit of money and be more user friendly. It wouldn't take much to take the house from 56 f, to 68 f. and not much to take it from 88 f, back to 56 f. If you can see storms coming and reset your thermostats accordingly you can use allot less energy. Can you see my point? TY

Ground Ssource Heating

For some useful information see link - www.coresource.co.uk

This is more aimed at vertical bore ground loops but given building constraints these might well prove the more applicable in most home builds in the nect few decades.

GSHP is a very efficient form of heating and cooling that's been used across certain areas of Europe for the last 50 years and is growing in popularity in North America too.

"geothermal" heating and cooling on paper is very efficient, but when you see how much digging and drilling and piping has to be done, then pumps and "fluids" installed and tested, it gets very expensive, and has to forever after be serviced by a professional, which adds another aspect to be considered. I believe that an inexpensive and user friendly "solar/geo foundation" can accomplish passive heating and cooling for the home that sits on it. With no moving parts to speak of, this kind of "foundation" protects the home from radical temperature changes during the hottest and coldest parts of the year. I don't see this kind of thinking in the building trades, and most peoples budgets will not allow for "geothermal" systems.

Couldn't the ground work for the foundation of a "solar home" include enough undisturbed ground, washed gravels, water proofing and good drainage, insulated properly and massive. That would create a dry "heat sink" (which could be considered a "thermal battery"), and the house above this would absorb this energy forever after. If you were to use the sun and water, an "in-floor radiant" heating system can be built into the foundation and radiant floors. This way the home Always would absorb this wonderful energy free of charge, and the "back-up heating and cooling sys." would fill in the gaps. This idea of having what I call a "solar foundation" To set the home on, is a big advantage, because , not only being a great utility space, it is already functioning and can add solar fluids to the floors. (around where I live in S.W. co. thats 300 days or so of very low utilities)

Heats usually flows from the warm media to the colder one. Since the ground temperature tends to stay around 16C, your house has to be warmer than that to have free cooling but it has to be colder than 16C to have free heating. Not very comfortable.

Also, as soon as you have a heat drain or source to the ground, its temperature will vary in the same direction. The thermal mass is huge but the conduction resistance is relatively high.

Sure.

There are "actively passive" solar homes in which the "basement" is a large pile of rocks, insulated from the ground around. Heat from simple air-based solar collectors is piped through this mass, warming it. In practice, all this warm rock can keep the house warm for several to many days of gray weather.

Some very simple passive solar houses have a monolith inside that is heated by the sun through appropriately placed and large windows. (These windows are insulated at night with blanket curtains, pumped in styrofoam beads, etc, etc.)

Thank you for your post, you are the first one to say that with some attention to the solar aspects of the site and foundation in the site, that quite a bit of energy can be saved. and is not that's what it's all about. The owner now has control of his utilities instead of the other way around. I know that the 32 to 56 degree earth temp influences the warm house by wicking it out, but a good plan can minimize that. ( lots of washed gravel and no clay is a must for backfill) and the warm friendly floors above the "crawl space" will radiate downward a bit and keep it in a comfort zone. Moving warm dry air through the mass of the "under house" works well too. although it's not done much. It does cost a bit more to "solaria and landscape" the site, but i think it would pay for itself in a short time. another thing is to dehumidify the crawl space by taking The air out, instead of cross ventilating, and bringing outside air in.

Architecture can and does heat and cool a structure with a minimum of moving parts (if any) all we have to do is learn more about it. (and sacrifice ) Living in S.W. co., and visiting the dwellings here has convinced me. They are thousands of years old, but retain their original function. Solar orientation and knowledge of the skies passed down with no written language. Their "foundations" were their schools. (meeting places)

" in practice, all this warm rock can/will keep the house warm for several to many days of grey weather".

That is what I call a " solar foundation". It not only holds up the house and keeps it dry, but it absorbs energy from the sun and distributes it. Full basements are not needed, but, well built, bigger crawl spaces, with good access, will add passive energy, and good storage space to any home. It is the amount of dry mass that counts, because it takes so long to heat it up. and thus exactly the same amount of time to cool off, and stays stable at 55 degrees. (no moving parts). If you a massive trumb wall within the foundation even more energy can be used by the house during all those grey days. (that's where the true savings is)

Most homes are built with foundations that only "hold up" the house.

A good "solar foundation" costs a little more, but gives the owner the ability to have more options during construction.

That is what I call a " solar foundation".
We may be talking about somewhat different things. In the concept I have in mind, the idea is not to keep the rock at 55 degrees but to keep it at 100 degrees or so -- a temperature higher than the desired inside air temperature of the living space. The rock must be well-insulated from the earth around it, so that the earth does not rob the rock of its heat.
I was referring to the sort of rock system discussed here: http://www.ces.purdue.edu/extmedia/ae/ae-89.html

This concept is used in home building, notably by ground-coupled heat pumps. (A term I prefer to "geothermal" because "geothermal" also refers to geyser or hot spring activity.)

Depending on location and how deep, ground temperature is around 56°F. By itself, this is not warm enough to heat buildings in the winter, and is just barely cool enough to cool buildings in the summer; hence "boosting" via the heat pump.

When used as a heat source/sink, the ground temperature changes, which must be addressed in system designs. There is some useful averaging over summer/winter.

"Does "geothermal" have to mean pipes and pumps installed below frost line, and full of fluid? (which is pretty expensive)"

To answer your question, yes, Geothermal involves a loop installed below grade and pumps to circulate the transfer medium. Yes, Geothermal is rather expensive.

Here are some useful links: http://minnesotageothermalheatpumpassociation.com/geothermal/earth-loop-options/

http://www.popularmechanics.com/science/energy/hydropower-geothermal/4331401

You can also do a Google search of "Home Geothermal System" for additional information.

The community where I live is heated and cooled by "heat pumps" in contact with water circulated from under ground. The temperatures of the subsoils here are in the 50 to 60 degrees F range so they can work both ways.

It is not expensive.

Another method is Berm or Earth Houses...

http://en.wikipedia.org/wiki/Earth_sheltering

We hope for another place

Well, in a very real sense we DO! When we bring in water lines and send out sewer lines, they are sent out below the frost line from a basement. So any home in North America is already partially underground, and is utilizing the earth heat to keep the pipes from freezing.

You "could" earth shelter your house just fine...have it fully underground for instance. However, such a home would be very uncomfortable unless conditions were exactly exactly right....the temperature a few meters down is not a comfortable temperature to keep your home environment at.

You would have to dig it deeper, install studs, and insulate just as you have to do above ground. And the earth will always be there, sucking heat from your living space...creating spots in the lower corners for mold to grow in, and generally making it difficult to both build and maintain and depending on a sump pump to never ever fail.

Other problems include, but are not limited to Radon infiltration, pests, zoning difficulties, bedrock outcrops, and a near impossibility to get a mortgage.

As I said, we do it (sort of) now with basements up here in Ottawa. There are a LOT of problems involved with making a basement liveable. It can be done...but it is expensive. So expensive that a large number of people have gone to the trouble to find out ways to do it cheaper. Mike Oehler is one of those people...he is my hero. However, as anybody who has ever watched Mike Holmes redo a basement, the problems of doing a good job abound, and generally speaking, building underground is not a good way to build a cheap house.

There have been some threads on CR4 that address these problems. You should search them out. Lots of good discussions from people like Chris and Capt. Moosie, and others.

(Damn...did it again! Replied to anonomous! What has come over me? Must be the egg nog.)

This principal has long been used in "earth berm" and "underground" homes, some of which are supplemented by heat pumps, burning stuff, etc.

In an earth-bermed home, the foundation should be insulated on the outside, so the concrete can act as a thermal mass, (rather than conducting heat into the ground in winter) and to reduce condensation in the summer.

An earth bermed home with passive solar (sun heating massive concrete etc located in the house) can be kept warm without any additional heating source, if it is located not too far north of the Mason-Dixon line.

Yes geothermal has come to mean pumps, etc. I don't like the term, which conjures up images of hot springs, etc.

couldn't an "earth-bermed" foundation and crawl space be built with a small well insulated "home", and solarium, above it? Wouldn't it have the same advantages as a fully, "earth-bermed" home, and store energy in the mass. It seems to me that most foundations for homes these days do not take advantage of the physics, (good sunshine for many, many days on average) and add no usable space to the home. The foundation of a home, I feel, is potential energy, which is over looked by builders & owners. (allot of homes are built over unusable crawls, and use forced air heating) You buy the whole footprint of the home, why not utilize it from the floor of the crawl space on up, and have really good access to it?. (instead of a very small "hole" in a closet floor). I think that "radiant heating" can really save energy.

The trouble with most passive heat storage methods such as tunnels filled with rocks and such is not so much the activities of the living as the stench of the dead.

Trombe walls work better for heat regulation than any earthern berms. And they are easy to build. They work brilliantly.

The reason why you have "unusable crawls" is because it is less expensive to build that way. A LOT less expensive. So if you are a young family man going to purchase a new home, are you going to get the fifty thousand dollar town home with the crawl space, or are you going to go for the two hundred thousand dollar mansion. You can buy a lot of insulation for the cost of digging a full foundation.

I suddenly realized how negative my posts sounded....I guess it helps to take a week off and re-read them. I don't think things are that bad, actually.

I DO believe that the way houses are being built here in North America is a disgrace....the lifespan of a house (according to my appraiser) is only forty years. That is to say, when you buy a house for, say, four hundred thousand dollars, it depreciates in real value by ten grand a year. During that time, you will need to replace much of the house....asphalt shingles, water softeners, plumbing fixtures, chimney brickwork, furnace...all will need replacement about halfway through its alotted time span. The "real" value I am referring to of course is not the "market" value. As so many people have found out in the last few years, market value can be volatile. It is market value which is usually higher, and is where the builder's profit lies.

Houses are often built with no regard to sun light direction, in fact most planning commissions demand that the ridge line of the house follow the line of the road in front, regardless of the direction of the sun. Other factors which should be addressed would include trees and trellis vines which shed their leaves in winter, and shade the house in summer, and attic summer ventilation systems. Earth sheltering does not provide the R value that a handspan of insulation will provide.

The R 2000 house developed by the University of Winnipeg, and referred to by every shyster salesman who is trying to sell a house nowadays does not use earth sheltering, or trombe walls...yet it uses a tiny fraction of the energy a "conventional" house uses.

Since all this work has been done for you, I suggest you research the methods we have already developed. Hamilton's Eco house, for instance.

The fact that most homes are built without first using the "solar" aspects of the site, IS disgraceful, and is a slap in the face of the whole idea of passive/active solar building. I know that subdivisions are not going to allow you to put your ridge line where you want it, but I guess it's the nature of the beast. The south side of the house can still gain some solar if built right.

"earth sheltered" homes are not what I was talking about in a post. There are good ways to use radiant heating over a dry, well insulated and ventilated, usable crawl space. (maybe a split level design). These types of foundations become a heat sink for the home, and save energy.

A well built foundation and house can be "adjusted" for too hot or too cold conditions, (by the way it's engineered), but most of the time the comfort zone is tolerable. Remember, the earth temperature is around 55 degrees, winter and summer.

Radiant aspects of a house, and it's foundation, can, and should be used, in building.

Earth sheltering does not provide the R value that a handspan of insulation will provide.

Nor is it intended to so so. The idea of earth sheltering is to provide an outside temperature of 55 degrees, so that for a given insulation, there is a much lower temperature differential in both summer and winter. Earth-bermed homes must be insulated from the ground.

Underground housing or earth berming to use earth as a thermal mass (as mentioned in the wikipedia article) is maybe a little misleading: the earth around your home is not a good place to store energy. You can try to warm up the earth around your home, but you have to pump a lot of energy into the earth to do so, and the earth is a poor insulator so that energy ends up being lost. (You are doing no better than you would living in a conventional basement.)

If you don't want the feel of living in a cave, then earth berming is really only to have a moderate temperature around the home, to reduce delta T. Then, with the home insulated on the outside of the underground walls, the walls are quite easy to keep at 70 or so. It they are not insulated on the outside, then they are damp in the summer and cold in the winter. (Even at 70, they are likely to be damp in the summer, so dehumidification is required.)

Some of you may be interested in this

http://www4.rgu.ac.uk/sss/research/page.cfm?pge=32982

Totally passive heating - no earth storage just massive insulation, mechanical heat recovery and ventilation.

Good answer.

What gets lost in the discussion is "degree days", foliage and ventilation. Its putting the electrical outlets in plastic bags, sealing the sill, doubling windows, and forming thermal breaks. These "little things" are, as you say, all important. Its not a great revolution, but thousands of little incrimental things which add up. There are two great inventions which can make the revolution happen. One is icf blocks. The other is the IR camera. You can lie to your friends, and I can lie to MY friends, but you CAN'T lie to the IR camera.

9 per cent? Sounds about right. For the same money, a housing developer will lose one house in twenty by building to R2000 standards....thats more than his profit. So the money dictates what is built and sold. The builder will never live in that house, and will never pay a single heating bill, so what does he care? With people being mobile, and often not living in a house for more than ten years, their attitude is "well, I can buy a lot of heating oil if I buy that cheaper non-R2000 house. I fear it will take a revolution in building codes...something which I don't think will happen as long as the developers drink and play at the same golf clubs as city councillors. What it needs is the ground swell of home owner voters to create the change which we would LIKE now, and will NEED as soon as the oil runs out.

That is why I think topics like this one are vitally important.

Does the R2000 system of building change any if a greenhouse/solarium is used on the south aspect of the house? How would solar thermal collectors, storage, and "in-floor radiant heating, add or subtract from the R2000 system? Also, can a "slab on grade" work,? if built properly within this R2000 system, or do crawl spaces work better?

You can download a pdf file of the R2000 specifications here. The information about crawl spaces is in appendix A2, page 2 of this link. Essentially, the problem with crawl spaces is the radon....the house is so sealed up that radon and other gasses (say, from decomosing soil matter like Hydrogen Sulphide, or glues or carpets, or others) which normally occur in very small doses can add up, and can result in health hazards. So a positive pressure needs to be applied to keep these dangers down in the soil where they belong. When you consider that most homes have a negative pressure from ventilation fans and even air exfiltration up into the attic, you can see that it may prove to be a problem to keep a positive pressure.

Green houses are very cool things. I would love to have one in MY house, and R2000 standards be damned. I don't think you can get a green house to meet R2000 standards...you just can't get all that glass to have sufficient insulation. If part of a house does not meet the standard, the whole house does not meet the standard. But hey, lots of houses around here are marketed as "almost R2000 standard", so why worry about it? A solarium will not give you enough energy during the day to compensate for the heat loss at night. UNLESS you do something out of the ordinary. Roll quilts over the glass for instance. Install styrofoam shutters which close off at night. Thats what I would do. But then, its not "passive" any more is it? But...an investment in a couple of quilts from the thrift store could really make that trombe wall earn its keep! The real problem at this point would be to decide if the investment in layers of environmentally expensive triple glazing is worth blocking the view with a big ugly rammed earth wall. Me...I would rather keep the view, and have a bunch of really heavy, possibly concrete based furniture for the sun to shine on during the day. Or bathtub sized planters.....whatever is heavy and will soak up heat. But thats your call...and the answers to this question is what makes your house truly YOURS.

Just as a mild experiment, try to place some nice heavy stuff (a layer of brick for instance) in the sun in your present living room. See if they absorb enough energy to keep you warm at night. Then try it without. See if it is better or worse. Nothing answers questions as good as experimental results.

Hi, well I guess the idea of using the "whole/hole" building site as a passive "battery", IS out of the ordinary. The battery includes all the washed gravels, and drainage, the footers (below frost line), the Well insulated and waterproof stem walls, a good crawl space with 1.5 inch "in-floor heated floor above TGI joists, a green house/trombe wall, with a 500 gallon solar tank, flat plate thermal collectors (optional but cool), A small pool/hot tub, wood fired heat exchanger, the trombe wall.

The trick is to get this system in place and "working" (and paid for) as soon as possible. If your contractor can get the septic sys., all underground piping in, top soil piled up and mulched (for later) , all washed rock backfills and drains in, foundations in, 1.5" radiant "slab" floor in, the green house complete and ready, garrage and drive way in (optional but cool), then you'll be ready to build your home (any style will work ysing this system, but R2000 standards are best). At this point you could relax a bit because as far as "heating/cooling" and mechanical is concerned, you're 75% done. ( and the jobsite is good and dry and secure for the next phase of contractioning. The Mass tries to stay the same temperature all year no mater what the air temp. so the more you invest now in well engineered foundations and "site construction", you already have a great place to hunker down during the construction of the "structure". My idea for the excess heat in the summer is to put this heat to use hot tub/pool or any where excess heat can be storred so not to over heat the home.

This system is all one piece so it does work well and is very user friendly. The more massive it is in the ground (and dry) the better, gravels and insulation are cheep. It does become a "grow hole" (as in greenhouse) and WILL lower utility bills dramaticaly.

It would be ashame to put an R2000 home on a bad "site", or any home for that matter. Site contracting could be the same system over and over again and leave the eye candy to the "general contractor".

Who in Canada has never wondered if there was a way to use that heat beating down on the roof in the summer to keep the place warmer in the winter. Therefore, I really DO like your attitute and approach. My comments are not meant to disparage your efforts in this direction an any way....to supplement them, based on my experiences as a contractor over a 15 year period. (I quit when I realized that "green" was honoured in the words but not in the deeds...and I was spending all my time in court trying to get paid...but thats a whole 'nother topic!)

I am not really as familiar with "heat pump" technology as I should be, but I think the exchange units will warm the water in the ground as they cool your space in the summer, and then release that heat in the winter. (well, thats what the literature says anyway!) But that assumes a fairly static body of water being drawn up to the units. And it is dependent upon increasingly expensive electricity. I prefer the outside wood burning heat exchange systems, but again, this may be site specific.

If I could keep my place at 55 degrees (a number which has been bandied around this thread...I think it is much lower in Ottawa and higher in West Texas) all year around, I might be able to convince my wife and her friends to never take their sweaters off. Ever. Good luck with that. Her term for that (I just asked her) is "uncomfortably cold". No doubt any Japanese citizen reading this right now is chuckling at how wimpy we are!

If I decided to increase the heat from 55 to a more comfortable 65 or even 70, then every degree above 55 will simply be sucked down into the trombe walls. This could be the reason why adobe construction is not as popular in Canada as it is in, say New Mexico or West Texas.

But wait. There's more. You don't get the heat going into your "thermal battery" unless there is a temperature differential. This means you still have to endure some fairly extreme temperature fluctuations, all to keep the trombe wall working. (or basement filled with gravel, or whatever.) To MY eye, this is too much like the tail wagging the dog, but YMMD. Keep in mind, we already HAVE a huge trombe wall system in most houses...that would be the layers of drywall on the walls of all the rooms. Do you think that by doubling it all up, you would achieve much in the way of summer-winter reduced delta T? I don't either. But I have noticed that whenever I would finally get a house drywalled, the temperature fluctuations through the work day become greatly attenuated. So thermal mass does work. One of my previous links noted that thermal mass works, but only to a point. Water seems to work better. Tanks of water instead of big earthern walls. But....they have their problems too. My friend (in Aliston Ontario, just north of Toronto) had the idea of keeping the big water tank for his green house plants IN the greenhouse....all that extra thermal mass would help right? Well, no, it didn't really...he took the heater out to use on another greenhouse, and within a couple of days, all that water froze. Experimental results...use them for what they are worth.

Personally, I think if you just increase the insulation by a few more inches of styrofoam, double up the windows to make them four pane instead of two pane, install a good venmar heat exchanger system to keep the mold spores and radon under control, and heavily insulate that heat sucking basement wall, you will nearly have achieved your goal of a house which can be heated with a candle. Then the question of creating a solar heated "battery" really should not even come up.

It would be better if floors had a good mass (with in-floor heating ), then they would only heat what was touching the mass. Convective heating "moves" and is wasted to a certain extent because as it moves it cools. In a good radiant heat system, you don't see or feel the heat, but the house tends to stay in a moderate comfort zone full time with out the high utility bills. If it is 70 degrees on this kind of floor, then it is only 72 degrees above your head. Do you really care what the temperature is above? In a convective system, if it is 70 degrees on the floor, then it can be 80 degrees above. (wasted energy and higher utility bills in my mind). Good t-stats, set and left alone, do the job quite well, and the in-floor tubes don't care where the hot water comes from. wood boiler, solar, gas boiler/water heater, geothermal heat pump, combination of all four, makes no difference, because the piping for the system is the same. The difference about warm friendly floors is that you can not get instant gratification from them (oh well just wait a bit).

If you use solar collectors, angle them more toward the winter sun to capture the most energy you can. Also if you have a hot tub that's where you put any extra heat in summer. I have found that outside wood boilers are expensive and the smoke stays low and stinky all the time.(and the piping from the boiler to the house is a pain) A good wood boiler system has a concrete chimney out the ridge of the house.

This kind of "mass" heating /cooling system costs a bit more to install, but saves so much energy in the long run.

In floor heating tubes are not what is normally thought of when you say "radiant" heating...radiant heating is used here in Canada in hockey arenas and warehouses and workshops. It is normally hot pipes high up in the rafters with reflectors that direct the IR down towards the people. It is really useful in rooms which need to be ventilated a lot, like machine shops and such because radiant heating does not heat the air...only the things in the room. You will find systems like this in train stations, bus stops, and welding shops which are open to the air. You can flush all the air out of the room, like, when you open the hangar doors to let the airplane out, and it takes only a few minutes to warm back up again because in actuality, air does not have much mass, and all in all, is not really that great a way to carry energy.

The "in floor" systems you are referring to are stunningly good systems. Although technically they are "radiant" in that they utilize the Stefan-Boltzmann constant, they warm things as much or more by convection than by radiation. But that is just me being pedantic. There is no doubt that a warm floor is better than a cool floor. No mold spores in the carpets....fewer dust mites and no fire or ignition hazards or slippery wet floors. And there is a perception of coziness which is all out of proportion to the energy use. Although I have been around when the crews installed these systems, I personally have not installed one. Looking forward to it. I think you are right on in your choice of heating system. It is very versatile.

And I agree...most commercial wood fired hydronic systems do not have high enough chimneys...for that reason they are regulated pretty much out of existance here in Ottawa. And if you use part of your own house to support a higher chimney (at least 12 inches above the ridge line I believe) then you don't get a break on your insurance...they increase your rates quite a bit for using a wood heater that is attached to your house. Oh well. It may be worth it. A business owner of my aquaintance uses a hydronic heater to heat his stone cutting and dressing shop...he uses old automobile radiators high up in unused corners and commercial barn fans to blow warm air down onto the work stations. The process of cutting and polishing stone uses a lot of water flooded sandpaper. This splashes a lot, so the workers get drenched pretty quickly. You want warm air moving down into the room, and the job still gets done even in the dead of winter. He goes through a lot of scrappy wood which is not really good for anything else.

Personally I used inside wood heat for years in this house until the wife complained it out of existance. The natural gas replacement is not nearly as nice, but there is a lot less dust.

As a long time user of hot tubs, I can state that they are only comfortable within a very narrow range of temperature. But you can insulate them really well, and some people (like art metal workers such as myself) don't consider them to be a luxury. I don't think you could use them for passive heat storage AND still use them for their intended purpose.

I don't have much experience with passive heating of hot water....aside from helping a friend install black pipes on the roof to help heat his pool. The great SCA Pennsic war has 10 thousand people suddenly arrive at their campground for one month in August. They do simulated fighting in real armour, therefore, they sweat a LOT, and they need a LOT of showers. This IS August in Pennsylvania! The owners of the camp site heat the hot water in great big plastic bags up on the hill. Although Pensic showers are famously cold, they are not as cold as they might be otherwise. I don't hang with those guys any more, but when I did, I appreciated the efforts they made to get 10 thousand sweaty college age kids less smelly. This was passive heating at its finest! I have always wanted to do a follow up to see how that system has held up over the years, and if there was a good R.O.I.

My analogy about "radiant heating" using hot water is like a rock in the desert. During the day the mass of the rock absorbs energy from the sun. when the sun goes down, then the energy comes back out at about the same rate. The bigger the rock, the more energy it can absorb and the longer it will give back. What I call a "radiant" floor has the same characteristics in that it absorbs then gives back. When mass radiates, it does so in all directions, unlike a convective system which hot air rises. A warm friendly floor with insulation below will radiate the things above it but not be convective. There are a few ways to add energy to the floors your choice, and when the floors get to the right temperature, they are pretty easy to maintain that temp. (but in a power failure your floors will still radiate for a long time) You really don't see or feel the heat, but it works very passively. Too cool a floor, or too hot a floor can be hard on your body. Putting heat in the upper spaces of any room is a waste of energy, and costs to install and maintain are high. Why use energy to make heat or radiation go downward, when it naturally wants to rise.

During the hot summer (S.W. Colorado), the energy from the sun can go to keeping my hot tub 24/7 , it's very cool at night here at 72,000 ft. so the floors can stay at a comfortable temperature. The domestic hot water also comes from a very cheep source and we have never run out. (once in a great while we have to use Nat gas to heat water). note: you can use a 50 gallon Nat/LP water heater to heat the floors of an 800 sq foot house. (much less in an R2000) which is a much simpler and user friendly system. Just let the t-stat run the pumps, and let the aqua-stat adjust the flame (no control boards allowed).

I know what your situation is up your way, but these floor systems work well.

Reading all these "things to be avoided" to improve heat retention are the things that I need in my parts to stay cool.

My house is 100% masonary and the ground floor is in direct contact with the ground.

I have huge windows and doors that are open all day.

I don't use aircon. I use fans. I enjoy a 28-30C environment even when it is 40 outside This time of year it drops down below 25 at night. Lovely.

I could never stand it!

Because the first sentence describes a "ground source heat pump", which requires an intervening fluid used as a refrigerant.

The term <...geothermal...> generally relates to pumping cool liquid to great depths and bringing to the surface heat that is normally retained at that depth in the form of hot fluid.