Geothermal home construction

A method for constructing structures to minimize the amount of fuel necessary to heat the structure during winter months as disclosed. The structure of this invention maximizes the heat obtainable from the earth at depths substantially below the frostline by providing a basement having a relatively thin floor of conducting or noninsulating material and walls with a maximum of reasonable insulation both in the basement level and in the living-level first floor of the structure. Grids are provided adjacent walls and below windows and doors at the first floor level whereby cold air within the house will drop to the basement. The external walls are of standard construction with maximum insulation to protect against heat loss from within the structure. The basement floor adjacent the walls may be insulated if desired. The structure consists of one or more floors over an excavated basement, the basement being at a depth sufficiently below the frostline so that the temperature of the earth or the geothermal heat will be relatively constant. In addition the walls are preferably insulated and the ceiling over the first floor contains insulation also.

For thousands of years, since prehistoric times, man took refuge in caves 
to utilize the geothermal heat of the earth. At a sufficient depth, the 
interior temperature of the cave would remain at approximately 50.degree. 
F. even during bitter cold winter weather. 
In contrast, the average home today which has a full basement has a floor 
sufficiently below the ground level to be maintained at about 50.degree. 
F. However, because of a lack of insulation, as will be subsequently 
explained, the ambient temperature within an unfinished basement may be 
substantially below the floor temperature. 
The instant invention is directed to maximizing the warming effect of 
geothermal heat within a living structure whereby a base ambient 
temperature may be maintained within the structure at or near the 
temperature of the basement floor even though the exterior temperature may 
be as low as 20.degree. below zero. The geothermal heat of the earth is 
then utilized as a heat sink because it has been established that the 
temperature at a substantial depth of, for example, seven feet, will vary 
from a median temperature of only about .+-.5 to 10 degrees from the 
hottest day of the year to the coldest. Furthermore, even this variation 
lags the change in surface temperature by at least about a month. 
Therefore, although the coldest surface temperature may be realized in the 
latter part of January, the coldest temperature at a depth of 7-10 feet 
may not be realized until as late as April, when the surface has already 
begun to experience the spring thaw and warming. 
Whereas other sources of energy such as solar heaters, and windmill or wind 
chargers for storage batteries provide energy without cost, these means 
require large capital investments and are subject to atmospheric changes. 
Solar heaters, obviously, will not function on a cloudy day, and wind 
chargers or windmills cannot provide power in the absence of wind. In 
contrast, geothermal heat is a constant that requires no machinery to 
utilize. In addition, geothermal heat is most efficient when the home is 
subjected to the lowest exterior temperatures, at night. When no outside 
doors are opened, heat loss from within the structure is at a minimum. 
Therefore, the efficiency is maximized during the periods of lowest 
temperature. The solar heated home, in contrast, must rely at night, on an 
energy storage means for heat during normally the coldest part of a 
twenty-four hour day. Wind powered homes smiliarly require storage means 
because the wind normally diminishes at night. 
This invention comprehends the use of a supplemental heating source then 
and maximum use of geothermal heat to minimize dependence on the 
supplemental heating system. The size of a supplemental heating system 
will depend on the amount of insulation in the home and the outside 
temperatures to be contended with. It has been discovered that by 
providing maximum reasonable insulation on walls and ceilings, together 
with minimum insulation on the basement floor and grids to allow 
circulation of cold air downwardly from the living area to the basement 
floor will maximize utilization of geothermal heat. In other words, the 
atmosphere within the basement is placed in a heat exchange relationship 
with the earth beneath the basement floor covering and the structure 
itself is fully insulated to minimize heat loss therefrom. 
Conventional uninsulated basement walls coupled with the normal loose 
fitting windows therein present a major source of heat loss in homes. A 
basement 30 feet by 30 feet and 71/2 feet deep will present an uninsulated 
wall surface equal to the floor area. Therefore in conventional homes heat 
exchange through the basement floor is more than offset by heat exchange 
through the walls which are exposed to much lower external temperatures. 
In addition, this invention includes the recovery of heat from hot water 
used within the structure before it is disposed of, and in addition, 
supplementing the heat transfer capability of the basement area by 
utilizing a circulating system for municipal water which also enters the 
structure at a temperature at or near the basement floor temperature of 
about 50.degree. F. 
Therefore, this invention relates to a method for constructing a heat 
efficient structure whereby only a minimum of fuel is necessary during 
winter months in order to maintain the interior living area of the 
structure at a temperature of about 68.degree. F. The invention comprises 
the development of heat transfer between the interior of the structure and 
the earth at depth sufficiently below the frostline to provide a heat sink 
in a temperature range of about 50.degree. F. It is well known that at a 
depth of five or more feet, the temperature of the earth is a relative 
constant, 50.degree.-55.degree. F. or 60.degree. F. summer and winter. 
Accordingly, caves, fruit cellars and the like are usable during winter 
months without danger of freezing. 
It has been discovered, however, that a conventional basement may be 
adapted to utilize geothermal heat, and thereby decrease the amount of 
supplemental heat necessary from costly energy sources such as natural 
gas, electricity, or fuel oil. It has been discovered that an ordinary 
depth basement may be maintained at a temperature of about 50.degree. F. 
whereby convection currents from the living area over the basement may be 
established so that the supplemental heat required will only be that 
necessary to raise the temperature of the first floor living area from 
50.degree. to 68.degree. F. during winter months when the outside 
temperature may be as low as -20.degree. F. 
In order to establish said convection currents it is necessary to fully 
insulate the walls of the basement and first floor of the structure and 
the ceiling over the first floor living area. It is then necessary to 
provide a basement floor only thinly covered with, for example, concrete 
so that heat transfer will be effective thereacross. If desired, the floor 
may even be bare earth. Also, the basement floor should not have 
insulating materials such as rugs or tiles thereon because such materials 
would obviously inhibit heat transfer. 
In order to facilitate the convection currents between the living area on 
the first floor and the basement, a plurality of grids are provided in the 
first floor separating the basement and the living area. The grids are 
preferably disposed beneath sources of cold air such as windows and 
exterior doors so that the air entering the structure immediately 
circulates to the basement where it is warmed to the ambient 50.degree. F. 
temperature of the floor. Supplemental heat is then provided preferably by 
hot air registers or baseboard electric heaters disposed in the first 
floor living area. If desired, heat sinks may be utilized to recapture 
some heat from hot water used within the structure. For example, hot water 
utilized in showers or in the kitchen may be circulated to a reservoir in 
the basement where it is retained while heat is transferred therefrom to 
the ambient atmosphere. When the reservoir cools to, for example 
50.degree. F. water therein may be discarded through conventional source 
systems. This invention then contemplates retention of water from 
dishwashers, showers, and sinks in a retention reservoir situated in the 
basement. The reservoir will function automatically to dump cool water 
from the bottom thereof as hot water enters the top. 
The external walls of the structure may be of conventional construction. 
However, it is preferred that the basement walls be constructed of 
light-weight concrete blocks without windows. In view of the heavy heat 
loss associated with concrete walls above the surface line of the earth, 
and also in connection with basement windows, this invention contemplates 
a basement structure, as noted above, of light-weight concrete blocks, and 
an absence of windows or window wells in the basement. Of course, wood 
ducts, well insulated, may be used for ventilation. The upper story or 
first floor of the house may be constructed from conventional building 
materials, either wood or brick, or both, with preferably insulated 
windowglass on the windows. Furring strips could be placed horizontally 
rather than vertically to help minimize the downward circulation of air 
through the walls. The conventional walls of the structure of this 
invention then support maximum reasonable insulation materials such as 
fiberglass or the like which may be disposed between conventional vertical 
supports (studs). Wallboard or the like then completes the interior 
surface of the walls. The ceiling preferably is of conventional 
construction but with maximum reasonable insulation therein to thereby 
insulate fully the interior of the structure except for the basement floor 
which allows heat transfer between the interior and the earth therebelow. 
While the basement floor may be excavated to any depth desired, a constant 
temperature is normally found below about 5 feet and therefore the usual 
71/2 foot standard depth basement will be adequate. 
In order to direct cold outside air to the basement floor, entry areas or 
vestibules are provided at external doors to the structure of this 
invention. A grid is located in the floor of the vestibule so that when 
the external door is opened, cold air entering the structure will drop to 
the basement. In addition, a vertical chute is provided to direct the cold 
air against the basement floor whereupon it becomes heated and circulates 
upwardly. 
It it is desired to utilize picture windows in for example a living room, 
preferably on the south wall of the structure, grids are provided in the 
floor immediately adjacent the window, and a metal sheet provided to 
direct air from the lower portion of said picture window downwardly 
through the grid. Preferably, the metal sheet is painted black on the side 
facing the window to absorb heat in the winter. This type of metallic 
shield extend from about the middle of the window down to the floor. 
Accordingly, it is an object of this invention to provide a method of 
constructing a home wherein a savings of theoretically up to 78% in both 
heat capacity and operation may be secured. 
It is another object to supplement the interior heating requirements by 
facilitating heat transfer in a home between the interior living space and 
the earth below the basement floor. 
It is another object to provide a living structure having a basement with 
all walls and ceiling fully insulated whereby convection currents are 
established between the living area and the basement to effect heat 
transfer between said area and the earth beneath the basement. 
It is another object to provide a structure having a full basement, 
insulated walls, and an insulated ceiling with grids in the floors whereby 
the living area air on the first floor is in communication with the 
basement air so that convection currents are established therebetween to 
maximize utilization of the capacity to transfer heat from the earth 
beneath the basement floor to the interior of the structure. 
It is still a further object to provide an insulated structure having a 
noninsulated basement floor and grids in the floor separating the first 
floor and the basement which grids are situated below windows, external 
doors, and the like so that cold air entering the structure drops to the 
basement floor for heat transfer across the basement floor with the earth 
disposed therebelow.

With attention to FIG. 1, the structure of this invention 10 comprises a 
basement area 12 and a first floor living area 14. The walls of the 
basement area are formed of preferably, conventional light-weight concrete 
blocks 16 with concrete footings 18. The basement area 12 is preferably 
excavated to about 7 feet below the surface 20. Earth at this level has 
been found to be maintained at a temperature of about 50.degree. F. 
without regard for the temperature at surface 20. In other words, the 
temperature at level 22 will be about 50.degree. F. regardless of the 
temperature at level 20. 
For example, depending upon the locality, the frostline or the depth at 
which moisture in the ground freezes will vary from two or more feet due 
to the insulating characteristics of earth. At a level substantially below 
the frostline, such as 6-8 feet, the temperature of the earth will remain 
essentially constant during summer and winter. This invention is directed 
to a method for constructing a structure whereby the constant temperature 
of the earth may be utilized as a heat sink for maintaining a basement 
temperature of 50.degree. F. which is then supplemented with auxiliary 
heat on the first floor level. 
In view of the fact that it is an essential feature of this invention that 
heat transfer from the surface 22 to the air in the basement area 12 
should be facilitated, the basement floor may consist of only a thin 
layer, for example concrete 24. In the alternative, the basement floor may 
consist of packed clay, bare earth, or any other relatively noninsulating 
material. However, it is essential to this invention that the basement 
floor be unobstructed by rugs, tile or other floor converings which would 
serve as insulators. Furthermore, storage boxes should be placed on tables 
or shelves and any basement partitions should have openings near the floor 
so that the entire floor of the basement can be placed in a 
heat-conducting relationship with the ambient atmosphere. 
The living area 14 is separated from the basement area 12 by a conventional 
floor 26 constructed in the normal manner with transverse beams (not 
shown). The floor construction shown at 26 is intended to be conventional 
in design with the exception of grids 28 and 28' disposed at preselected 
areas. Grids 28 and 28' then allow communication between the living area 
14 and the basement area 12 whereby convection currents may be established 
circulating cold air from area 14 downwardly into area 12 for heat 
exchange with surface 24. For example, grid 28 may be a vestibule or entry 
grid disposed adjacent the front door (not shown). Grid 28' would be 
disposed adjacent the back door (not shown) so that cold air entering 
would circulate to the basement 12 to be warmed. Cold air grids 28 also 
may be located beneath windows or other cold air areas. 
The exterior walls 30 of the above ground portion of structure 10 are of 
conventional construction of brick or wood, for example. The walls, 
however, have maximum insulation which may be, for example, from four to 
six inches. Preferably, horizontal furring strips 32 extend along the 
walls 30 and the concrete blocks or bricks 16. These furring strips then 
support insulation 34 extending vertically from footings 18 to the upper 
portion of living area 14. This insulation is of conventional design. 
As would be obvious to those skilled in the art, conventional vertical 
studs (not shown) may be used to support insulation 34, and wallboard or 
the like may be laid over the interior surface to complete construction of 
the walls. The living area 14 also has insulation 36 extending between 
walls 30 so that the living area 14 is sealed by insulation. Windows in 
the living area would be provided, but are not shown herein. Windows 
should be of conventional design with either double or triple pane glass. 
Similarly, grids (not shown) are disposed below these sources of cold air 
also. 
Accordingly, the structure 10 is essentially thoroughly insulated on all 
sides and in the ceiling thereof so that heat exchange with the structure 
is by convection currents between the living area 14 and the basement 
floor 24 and through the basement floor to the earth at 22. Any interior 
living space (not shown) wherein windows could be opened, such as bedrooms 
during the night, should also be insulated with weatherstripping provided 
at the doors thereof, and walls should have the same insulation as 
exterior walls. In such instance, the grids 28 disposed within such a room 
would obviously be closed before windows were opened. 
It is contemplated that the structure 10 would be served by an auxiliary 
heating source (not shown) which conventionally could be hot air, 
baseboard electric heaters, or the like disposed along the floor 26 and 
within living area 14. Of course, hot water or hot air furnaces could be 
disposed in the basement and radiators or ducts provided on the first 
floor. In view of the fact that without auxiliary heating, the interior of 
the structure would be maintained at or near the temperature of the 
basement floor 24, the heat necessary to maintain the living area at a 
confortable temperature during the winter months should be that equal to 
producing an increase in temperature from 50.degree. F. to 68.degree. F. 
While it is contemplated that rugs or the like would be disposed on floor 
26, it is not contemplated that the basement floor 24 would be covered 
with any insulating material. In fact, if desired, the basement floor may 
be insulated itself from side walls and footings 18 by, for example, a 
wooden border piece 36. See FIG. 3. Insulating pieces 36, however, are 
optional and could be used to minimize heat transfer by contact with the 
footings 18. 
With reference to FIG. 2, in order to make maximum utilization of the heat 
energy generated within the structure 10, this invention also contemplates 
a heat recovery system for retaining heated water in the basement area 12. 
When hot water from a hot water heater, (not shown) is utilized for 
example in a shower, laundry, or dishwasher, schematically shown at 40, 
the waste water normally would be at a temperature of 100.degree. to 
170.degree. F., far higher than the basement ambient temperature in area 
12. Accordingly, water from a hot water appliance could be routed by a 
conduit 42 to a heat trap 44. The hot water would be retained in the heat 
trap 44 until water at a higher temperature entered the trap. The cooler 
water would then be forced out of trap 44. The hot water within the trap 
would warm the air in the basement and would increase the basement 
temperature somewhat at the level of the heat trap. In view of the fact 
that the average four-person family uses 120 gallons of hot water a day, 
it is contemplated that a substantial amount of heat may be retained 
within the structure by holding the used hot water in heat trap 44. 
As an additional embodiment, a second heat trap 46 could be provided for 
use as follows. If waste water is collected in heat trap 44 until it is 
partially cooled, it may be transferred to a second heat trap 46 by hotter 
water from applicance 40. When the water in heat trap 46 had reached 
ambient temperature, it would no longer need to be retained. However, to 
warm the basement air, it is important that the heat trap tanks be located 
so that they generally are in colder air than their own temperature. When 
the temperature of the water within the tank reaches ambient atmospheric 
temperature, it could be expelled through a conventional sewer drain 48. 
In the alternative, as will be obvious to those skilled in the art, a 
single heat trap (not shown) could be utilized which would dump partially 
cooled water retained therein into drain 48 whenever appliances 40 
expelled hotter water thereinto. 
Heat traps 44 and 46 are of conventional design and are merely storage 
tanks intended to be utilized to warm the ambient air within basement area 
12. They are located away from cold air grids so that the heat therein may 
rise into the living area through, for example a centrally located grid 
53. 
With reference to FIG. 3, it should be recognized that municipal water in a 
water line 50 utilized within the structure 10 enters the structure at a 
temperature of about 50.degree. F. Accordingly, the water line 50 could 
extend along the basement floor 24 through a finned heat exchanger 52 
before entering the living area through line 54 for use in kitchens and 
bathrooms. The heat exchanger 52 would then supplement the geothermal heat 
exchange between ambient air in the basement 12 and the basement floor 24. 
With reference to FIG. 4, a preferred embodiment of the structure of this 
invention 10 also uses vestibules 70 and 70' as follows: in view of the 
fact that external doors (not shown) to the structure will admit cold air 
to the structure 10, a preferred embodiment encloses the doorway opening 
and an entrance portion of the living area 14 in a vestibule 70 or 70'. 
The floor portion of the vestibule 70 or 70' comprises a grid 72 or 72'. 
When the door (not shown) has opened, cold air will immediately flow 
downwardly through the grid 70 or 70' to the basement floor 24. 
To facilitate circulation toward the floor 24, a chute 74 or 74' extends 
downwardly into the basement area 12 substantially therethrough to the 
floor 24. Cold air then passing through grid 72 or 72' is directed by 
chute 74 or 74' to the floor 24. At floor 24, the cold air then is warmed 
by contact therewith for circulation upwardly through the structure 10. 
In summer, if a window is left open in an exterior door, and an exhaust fan 
is located in living area, fresh air will be pulled automatically into 
vestibule, then down grids to basement floor, to be cooled approximately 
to 50.degree., thus providing automatic partial air conditioning. 
With reference to FIG. 5, the structure 10 of this invention will include 
windows. A preferred window treatment as shown in FIG. 5, comprises a 
conventionally mounted preferably thermal-pane or insulated-pane 76 
mounted on wall 30 in the conventional fashion. A metal shield 78 is 
provided substantially covering the lower portion of picture window 76. A 
grid 80 in floor 26 is located between shield 78 and outer wall 30. 
Accordingly, interior air cooled by contact with pane 76 will circulate 
downwardly between shield 78 and pane 76, and through grid 80 to the 
basement area 12. The portion of shield 78 facing window 76 preferably is 
painted black or coated with black material whereby it will be warmed by 
the sun during the daytime. At night, conventional metal venetian blinds 
or shutters (not shown) may be utilized to cover balance of window 76 and 
thereby minimize radiant heat loss from within structure 10. 
In summary, then, the instant invention comprises a method for constructing 
structures which have a fully excavated basement. The structure of this 
invention comprehends an insulated interior design with an uninsulated 
basement floor and grids located in close proximity to cold air sources 
and mounted in the earth level floor. The living area above the basement 
then is in communication with the basement through grids whereby 
convection currents circulate cold air from above the floor into the 
basement for heat exchange with the basement for a period. In this way, 
the interior of the structure may be maintained at the approximate 
50.degree. F. temperature of the basement floor. Therefore, only a low 
capacity auxiliary heating element in the living area will be necessary to 
raise the temperature to a comfortable level therein. 
In contrast to conventional structures, the basement walls are fully 
insulated so the geothermal heat of the basement floor is conserved. 
This invention also includes as alternate embodiments to supplement heat 
exchange in the basement, one or more water retention heat exchangers or 
traps whereby waste hot water will be retained in the basement area until 
it reaches ambient temperature. Furthermore, the heat capacity of the 
basement floor may be increased by utilizing municipal water in, for 
example, finned heat exchangers disposed along the floor. The temperature 
of municipal water is at or near that of the basement floor and therefore 
heat exchangers of this type would add to the geothermal heat capacity of 
the basement floor. 
The invention may be embodied in other specific forms without departing 
from the spirit or essential characteristics thereof. The present 
embodiments are therefore to be considered in all respects as illustrative 
and not restrictive, the scope of the invention being indicated by the 
appended claims rather than by the foregoing description, and all changes 
which come within the meaning and range of equivalency of the claims are 
therefore intended to be embraded herein.