HVAC with no monthly bills?
This complete independence is implied by some amazing successes which have already been pioneered. Various terms have been suggested ie: Passive Annualized Heat Storage, PAHS, & Annualized Geothermal Solar, AGS. Semi-buried houses hold many advantages for this more thorough and economical "green technology". Otherwise, unburied houses must be "buried" with piles of super-insulation. Minimalist-window- super insulating has achieved green popularity. However, it still depends on some heating fuel, (though a conserving amount of fuel). To open a house up with more windows and at the same time not consume imported fuels at all, is the domain of massive-thermal-storage like PAHS or AGS. The chief obstacle is combining geology with architecture which stretches belief and skill. It is left to pioneers to explore the ramifications. The incentive is fuller green living, bringing more daylight and scenery in for health, while not promoting world havoc for energy.This model is the result of intuitive speculation, spurred by reported successes with underground houses.
The ground-breaking, well documented project: PAHS (Passive Annual Heat Storage) Project was paid for by a US Government Grant!.
Being a visual person myself and an experienced-experimental-builder, i needed to diagram how AGS might be done in a traditional, above-ground house which poses difficult challenges for self-heating-cooling. I have yet to build AGS/PAHS, but have built thermal-storage and given lengthy thought to the subject. Semi-buried houses hold natural advantages to simplify and extend "green technology". Also, cold-wet soil conditions are addressed.
Following is a schematic blog on possibility. An ordinary house might be retrofitted, by skirting a large mass of soil within building insulation.The purpose is to connect a large thermal mass to the house through the cellar. The cellar walls would doubly serve as a heat exchanger. Below, partly transparent views show ditching around the house for drainage and insulation.
In addition to insulation, some form of earth tubes or pipes are used to distribute heat. The pictures show a deep perimeter ditch (dug by a back hoe). Pictured below, 14 more shallow ditches radiate from house. The deep ditch should ensure good diversion of possible ground water, providing water-springs are not enclosed with-in the thermal mass.
Drainage pipes are first placed at the bottom of the perimeter ditch, followed by insulation along with the heat distributing, larger perimeter pipe. Then, 14 radial tubes connect to the larger perimeter distribution pipe. (Ditches and insulation are covered and yard is restored, eventually, in the process).
Additionally, 4 air-intake pipes are placed and other connections are made within the house. This model, for the moment, omits house-ventilation tubes which have been favorably reported in early PAHS work. Some arguments discourage house ventilation tubes passing through the ground, for fears of mold. Yet ground tubes might pose no greater risk of mold, than any sort of mechanized heat exchanger, which can also potentially harbor mold. House ventilation is benefited by use heat reclaimers or heat exchangers, (buried or unburied). Time may tell which type proves best. Hait's PAHS house with more than a decade of proven performance, does have out going air tubes next to incoming air tubes, as a heat exchanger.
This modeling proposes making use of normal attic heat to help drive the whole system. Next shown, is use of the attic or roof heat, for inducing a natural draft. Roof construction can allow concentrated-solar venting through a chimney. A solar attic chimney can produce draft equivalent to a small electric fan during warm days. I have 20 years experience using natural draft from my solar dome attic, (but built too early before PAHS to know about it. Needless to say, I'd love to help build a project from scratch. More on solar drafts can be seen here.)
This model would need enough draft inducement from inlet to outlet. Summer air intake will "charge" the thermal mass while stabilizing the mass to comfortable temperatures. If additional fan power is needed, a solar-electric panel could provide the power just when it is needed, (during the warmest part of the day). An insulating damper may also be needed to stop heat loss during cold periods, preferably a self acting type, (powered by a solar piston).
The thermal mass is connected to the house interior trough the cellar. It is blanketed all around except for underneath (with purple insulation). While straight pipe- paths are illustrated, in reality the pipes should be made equal in length. Additional interior pipe length is needed to accommodate the cellar contours.
Such models could ideally be analyzed with thermal software to verify what kind of configurations are effective and most expedient for particular regions. Computer thermal modeling could provide us with valuable clues and findings. Good thermal software is generally available but at high cost. I cannot afford the software costs but want to offer precision-3D-modeling to support thermal modeling. Just ask for Bo! (1-207-342-5796)
Another Example on this site: Branched U-Tube Thermal Distributor (designing an earth-tube installation for a semi-buried home.)
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See my nephew's research and discussion page on PAHS and PAHS precursors.
Joe Anderson, PE, through his Prime Design Engineering, has done some interesting thermal modeling for self heating houses. (I think Joe coined the term "self heating house"). Joe found that earth tubes can be minimal and even omitted for much of the USA. I interpret that one can almost remove floor insulation in a super insulated house to achieve self heating. However the surrounding ground would need to be well insulated. Call it self powered radiant flooring? Through some emails and perhaps unknowingly, Joe helped jog me to invent the square donut design.
Here is a Virginia man who achieves self heating without earth tubes, but does depend on an electrical heat exchanger. Avoiding the use of electricity is one area I would love to explore as detailed above on this page.
Another North Westerner who has designed and built AGS homes reports on his work, but offers few picture-diagrams on the web.
Next follows a blog about visualizing concentric thermal gradient waves.
The drawing below shows the (exaggerated) thermal gradient wave in simple-coded colors (blue=cold, green=intermediate, red=warm). A round house is surrounded by the concentric thermal wave. Air is drawn in through multiple, parallel tubes which are placed in a predominantly parallel-spiral pattern. A greater number of smaller tubes are proposed in contrast to the more popular notion of fewer-larger tubes.
Snap shots of the thermal wave show the seasonal extremes. An alternative tube layout with radiating spirals is illustrated below, intended for larger buildings, (where the building circumference becomes to great for encircling spirals).
(These second illustrated coils-above, have a potential for digging with micro- excavators, from surface, not so difficult as might be imagined. Condensation suggest a need for drainage holes in all valleys.)
Thermal modeling would help greatly in scaling the system parts for optimum performance and minimum cost. What diameter tubes would work best? (The software generally recommended is FEA, Finite Element Analyses, generally not licensed to small, pioneering efforts).A newly proposed concrete construction method for building strong buried structure, suitable for supporting massive earth loads, (for large thermal mass).
Exposed Rock Terrain
Consider ways to force heat into bed rock through small drilled holes. A hollow pavement collector, shaped to look like natural ledge can collect summer heat. A solar heated FC (ferrocement) "mulch", sloped enough for heated air to flow to top of FC area, where it can collect, for heat storage. The picture on right suggests using water heated collectors.
Another hot water,heat collector concept, click here for diagram. Here is a contrasting solution for use of water in a trickle down mode. Finally a 2009 project to employ this idea, an eyelid greenhouse.
Still the most acclaimed book on PAHS to buy: "Passive Annual Heat Storage, Improving the Design of Earth Shelters. It can be purchased here: http://www.rmrc.org/order.htm
I was happy to meet a Swedish man who offered a Swedish term "passive jordvärme". He mentioned dutch self heated housing along dikes or rivers. I'd love to see pictures if any can share them. It seems the term "self heating homes" googles some foreign language sites.
Note: These pages are placed in the public domain and are furnished "as is". The author assumes no responsibility for the use or misuse of the concepts in this series. All authorities should be satisfied first, as might be required, by relevant laws, before any building proceeds.
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