a2) United States Patent
`US 8,423,322 B2
`(0) Patent No.:
`Steinberget al.
`*Apr. 16, 2013
`(45) Date of Patent:
`
`US008423322B2
`
`(54)
`
`(75)
`
`SYSTEM AND METHOD FOR EVALUATING
`CHANGES IN THE EFFICIENCY OF AN
`HVAC SYSTEM
`
`Inventors: John Douglas Steinberg, Millbrae, CA
`(US); Scott Douglas Hublou, Redwood
`City, CA (US)
`
`(73)
`
`(*)
`
`Assignee:
`Notice:
`
`EcoFactor, Inc., Millbrae, CA (US)
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`This patent is subject to a terminal dis-
`claimer.
`
`(21)
`
`Appl. No.: 13/230,610
`
`(22)
`
`Filed:
`
`Sep. 12, 2011
`
`Prior Publication Data
`
`US 2012/0065935 Al
`
`Mar. 15, 2012
`
`4,341,345 A
`4,403,644 A
`4,475,685 A
`4,655,279 A
`
`7/1982 Hammeret al.
`9/1983 Hebert
`10/1984 Grimadoetal.
`4/1987 Harmon
`
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`0415747
`3/1991
`10-1994-0011902
`6/1994
`10-2000-0059532
`10/2000
`
`EP
`KR
`KR
`
`OTHER PUBLICATIONS
`
`Arens, et al., “How AmbientIntelligence Will Improve Habitability
`and Energy Efficiency in Buildings”, 2005, research paper, Centerfor
`the Built Environment, Controls and Information Technology.
`Bourhan, et al., “Cynamic model of an HVAC system for control
`analysis”, Elsevier 2004.
`Comverge SuperStat Flyer.
`Control4 Wireless Thermostat Brochure, 2006.
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`(63)
`
`(60)
`
`(51)
`
`(52)
`
`(58)
`
`(56)
`
`Related U.S. Application Data
`
`(Continued)
`
`Continuation of application No. 12/211,690, filed on
`Sep. 16, 2008, now Pat. No. 8,019, 567.
`
`Provisional application No. 60/994,011, filed on Sep.
`17, 2007.
`
`(2006.01)
`
`Int. Cl.
`GOIB 15/00
`US. Cl.
`USPC oo. 702/182; 702/176; 702/183; 702/184;
`700/276; 700/278; 236/1 C; 236/46 A; 236/46
`R; 165/236; 165/239
`Field of Classification Search.................. 702/176,
`702/182—-184; 700/276, 278; 236/1 C, 46 A,
`236/46 R; 165/236, 239
`See application file for complete search history.
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,136,732 A
`
`1/1979 Demarayetal.
`
`Primary Examiner — Sujoy Kundu
`(74) Attorney, Agent, or Firm — Knobbe, Martens, Olson &
`Bear, LLP
`
`(57)
`
`ABSTRACT
`
`The invention comprises systems and methodsfor evaluating
`changes in the operationalefficiency ofan HVAC system over
`time. The climate control system obtains temperature mea-
`surements from at least a first location conditioned by the
`climate system,andstatus of said HVAC system. One or more
`processors receives measurements of outside temperatures
`from at least one source other than said HVAC system and
`compares said temperature measurements from said first
`location with expected temperature measurements. The
`expected temperature measurementsare basedatleast in part
`upon past temperature measurements.
`
`14 Claims, 13 Drawing Sheets
`
`
`
`
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`
`
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`
`
`
`
`
`
`1060. Ee
`(oo
`
`
`IJ [patazase]
`
`
`
`
`
`
`
`
`
`UTILITY
`DEMAND REDUCTION
`SERVICE SERVERS:
`
`
`
`
`
`
`
`001
`
`GOOGLE 1027
`GOOGLE1027
`
`001
`
`

`

`US 8,423,322 B2
`
`Page 2
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`PPPPrPrrrrrrPES
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`Reference Manual,
`
`* cited by examiner
`
`002
`
`002
`
`

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`U.S. Patent
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`Apr. 16, 2013
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`US 8,423,322 B2
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`U.S. Patent
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`Apr. 16, 2013
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`US 8,423,322 B2
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`Sheet 11 of 13
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`US 8,423,322 B2
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`INPUT OUTSIDE
`CLIMATE DATA
`
`INPUT HVAC
`DUTY CYCLE DATA
`
`INPUT PRIOR INSIDE
`TEMPERATURE DATA
`
`1102
`
`1104
`
`1106
`
`
`
`INPUT
`BUILDING/USER
`PROFILE
`
`1108
`
`INPUT CURRENT
`INSIDE
`TEMPERATURE
`
`CALCULATE
`THERMAL MASS
`
`7170
`
`T1702
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`013
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`013
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`

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`INPUT OUTSIDE
`CLIMATE DATA
`
`
`
`1208
`
`1270
`
`CALCULATE
`RELATIVE
`EFFICIENCY
`
`L272
`
`CHANGED
`
`
` EFFICIENCY
`
`DOES PATTERN
`MATCH CLOGGED
`FILTER PATTERN
`
`REPORT
`CLOGGED
`FILTER
`
`
`
`DOES PATTERN
`MATCH REFRIGERANT
`
`
`DOES PATTERN
`MATCH OPEN
`WINDOW/DOOR
`?
`
`DOES
`
`PATTERN MATCH
`
`PROBLEM n
`
`PanaLty
`
`n
`
`
`
`LEAK
`
`
`
`
`
`
`
`
`YES
`REPORT OPEN
`WINDOW/DOOR
`
`
`
`
`
`L1G. 12
`
`014
`
`014
`
`

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`INPUT OUTSIDE
`CLIMATE DATA
`
`
`
`INPUT HVAC
`DUTY CYCLE DATA
`
`
`
`INPUT INSIDE
`TEMPERATURE DATA
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
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`
`
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`INPUT PROFILE DATA
`
`
`
`INPUT
`COMPARATIVE DATA
`
`CALCULATE EXPECTED
`INSIDE TEMPERATURE
`READING
`
`G12
`
`DOES INSIDE
`TEMPERATURE READING
`DIVERGE FROM
`PREDICTED VALUE
`?
`
`INPUT HISTORICAL DATA
`
`1318
`
`
`13520
`INPUT SOLAR
`PROGRESSION DATA
`
`DOES PATTERN
`CORRELATE WITH HISTORICAL
`AND SOLAR PROGRESSION
`DATA
`9?
`
`
`
`1524
`
`\NO
`
`CALCULATE EXPECTED
`DURATION OF
`DISTORTION EVENT
`
`
`
`SET TARGET TEMPERATURE BASED
`ON CALCULATED DATA FOR
`DURATION OF DISTORTION EVENT
`
`L1G. 13
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`015
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`

`US 8,423,322 B2
`
`1
`SYSTEM AND METHOD FOR EVALUATING
`CHANGES IN THE EFFICIENCY OF AN
`HVAC SYSTEM
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation of U.S. patent applica-
`tion Ser. No. 12/211,690,filed Sep. 16, 2008, entitled SYS-
`TEM AND METHOD FOR EVALUATING CHANGESIN
`
`THE EFFICIENCY OF AN HVAC SYSTEM,which claims
`priority to U.S. Provisional Application No. 60/994,011, filed
`Sep. 17, 2007, each ofwhich is hereby incorporated herein by
`reference in its entirety.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to the use of thermostatic HVAC
`
`controls that are connected to a computer network. More
`specifically, communicating thermostats are combined with a
`computer network in order to evaluate changes in the opera-
`tional efficiency of an HVAC system overtime.
`2. Background
`Climate control systems such as heating and cooling sys-
`temsfor buildings (heating, ventilation and cooling, or HVAC
`systems) have been controlled for decades by thermostats. At
`the mostbasic level, a thermostat includes a meansto allow a
`user to set a desired temperature, a means to sense actual
`temperature, and a meansto signal the heating and/or cooling
`devices to turn on oroff in order to try to change the actual
`temperature to equal the desired temperature. The most basic
`versions of thermostats use components such as a coiled
`bi-metallic spring to measure actual temperature and a mer-
`cury switch that opens or completes a circuit when the spring
`coils or uncoils with temperature changes. More recently,
`electronic digital thermostats have become prevalent. These
`thermostats use solid-state devices such as thermistors or
`thermal diodes to measure temperature, and microprocessor-
`basedcircuitry to control the switch and to store and operate
`based upon user-determined protocols for temperature vs.
`time.
`
`These programmable thermostats generally offer a very
`restrictive user interface, limited by the cost of the devices,
`the limited real estate of the small wall-mounted boxes, and
`the inability to take into account more than twovariables: the
`desired temperature set by the user, and the ambient tempera-
`ture sensed by the thermostat. Users can generally only set
`one series of commandsperday, and in order to change one
`parameter(e.g., to changethe late-night temperature) the user
`often has to cycle through several other parameters by repeat-
`edly pressing one or two buttons.
`Because the interface of programmable thermostats is so
`poor, the significant theoretical savingsthat are possible with
`them (sometimescited as 25% of heating and cooling costs)
`are rarely realized. In practice, studies have fund that more
`than 50% of users never program their thermostats at all.
`Significant percentages of the thermostats that are pro-
`grammed are programmed sub-optimally, in part because,
`once programmed, people tend to not to re-invest the time
`needed to changethe settings very often.
`A second problem with standard programmable thermo-
`stats is that they represent only a small evolutionary step
`beyondthefirst, purely mechanical thermostats. Like thefirst
`thermostats, they only have two input signals—ambient tem-
`perature and the preset desired temperature. The entire
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`advance with programmable thermostats is that they can shift
`between multiple present temperaturesat different times.
`
`SUMMARY OF THE INVENTION
`
`There are many other sources of information that could be
`used to increase comfort, decrease energy use, or both. For
`example, outside temperature and humidity strongly affect
`subjective comfort. On a 95 degree, 90 percent humidity day
`in August, when people tend to dress in lightweight clothing,
`a house cooled to 70 degrees will feel cool or even uncom-
`fortably cold. On a below-freezing day in January, when
`people tend to wear sweaters and heavier clothes, that same
`70 degree home will feel too warm. It would therefore be
`advantageousfor a thermostat system to automatically incor-
`porate information about external weather conditions when
`setting the desired temperature.
`Thermostats are used to regulate temperature for the ben-
`efit of the occupants in a given space. (Usually this means
`people, but it can of course also meancritical equipment, such
`as in a room filled with computer equipment.) In general,
`thermostats read temperature from the sensor located within
`the “four comers”ofthe thermostat. With a properly designed
`system, the thermostat may well be located such that the
`temperature read at the precise location of the thermostat
`accurately reflects the conditions where the human(orother)
`occupants tend to be. But there are many reasons and circum-
`stances in which that will not be the case. A single thermostat
`may produce accurate readings in some circumstances but not
`others; it may be located in a place far from the occupants, or
`too far from the ductwork controlled by the thermostat, etc. In
`one house, for example, the thermostat may be located in a
`spot that receives direct sunlight on hot afternoons. This could
`cause the thermostat to sense that the local ambient tempera-
`ture is extremely high, and as a result signal the A/C to run too
`long, making the rest of the home too cold, and wasting
`considerable energy. In another house, the thermostat may be
`located in a hallway without ductwork or where the nearby
`ducts have been closed. In such a scenario, the thermostat is
`likely to (correctly) report cold temperatures in the winter,
`leading the heating system to overheat the rest of the house
`and waste considerable energy.
`These problems can be reduced or eliminated through use
`of additional remote temperature sensors connected to the
`thermostat’s control circuitry. However, such systems require
`additional hardware, additional thermostat complexity, and
`skilled installation and configuration.
`It would therefore be desirable for a thermostat system
`using only a single temperature sensor to take such sub-
`optimalinstallations into accountandto correct for the erro-
`neous readings generated by such thermostats.
`Different structures will respond to changes in conditions
`such as external temperature in different ways. For example,
`houses built 50 or more years ago will generally havelittle or
`no insulation, be poorly sealed, and have simple single-glazed
`windows. Such houses will do a very poor job of retaining
`internal heat in the winter and rejecting external heat in the
`summer. In the absence of applications of thermal measures
`suchasheating and air conditioning,the inside temperaturein
`such houses will trend to track outside temperatures very
`closely. Such houses maybesaid to have low thermal mass. A
`house built in recent years, using contemporary techniques
`for energyefficiency such as high levels ofinsulation, double-
`glazed windowsandother techniques, will, in the absence of
`intervention, tend to absorb external heat and release internal
`heat very slowly. The newer house can be thought ofas having
`higher thermal mass than the older house.
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`US 8,423,322 B2
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`3
`A conventional thermostat has no mechanism by whichit
`might take the thermal mass ofthe structure into account, but
`thermal mass significantly affects many parameters relating
`to energy efficiency.
`Thecost to an electric utility to produce powervaries over
`time. Indeed,the cost ofproduction between low demand and
`peak demand periods can vary by as much as an order of
`magnitude. Traditionally, residential customers paid the same
`price regardless of time or the cost to produce. Thus consum-
`ers have hadlittle financial incentive to reduce consumption
`during periods of high demand and high production cost.
`Manyelectric utilities are now seeking to bring various forms
`of variable rates to the retail energy markets. Under such
`schemes, consumers can reduce costs by taking into account
`not just how much energy they use, but when theyuseit.
`Thus many consumers now can see real benefits from opti-
`mizing notjust the total number ofkilowatt-hoursofelectric-
`ity consumed, but also optimizing whenit is used. The opti-
`mum strategy for energy use over time will vary based upon
`many variables, one of which is the thermal mass of the
`structure being heated or cooled. In a structure with high
`thermal mass, heating and cooling can effectively be shifted
`away from high costperiods to lowercost “shoulder”periods
`with little or no effect on comfort. If, for example, a utility
`charges much higher rates on hot summer afternoons, it is
`likely that pre-cooling a high-thermal mass structure just
`before the high-cost period and then shutting down the air
`conditioning during the peak will allow the house to remain
`comfortable. But in a house with low thermal mass, the ben-
`efits of pre-cooling will quickly dissipate, and the house will
`rapidly become uncomfortable if the air conditioning is shut
`off. Thus it would be advantageousfor a temperature control
`system to take thermal mass into account whensetting desired
`temperatures.
`Manyfactors affect the efficiency of HVAC systems. Some
`maybe thoughtof as essentially fixed, such as the theoretical
`efficiency of a central air conditioner (often expressed as its
`SEERrating), the matching of a given system to the charac-
`teristics of a given home,the location and size of forced-air
`ductwork, etc. Other contributors to efficiency are more
`dynamic, such as cloggedfilters, refrigerant leaks, duct leak-
`age and “pop-offs,” and thelike.
`Mostofthese problemsare likely to manifest themselves in
`the form of higher energy bills. But the “signature” of each
`different problem can be discerned from the way in which
`each such problem affects the cycle times of a given HVAC
`system over time andrelative to weather conditions and the
`performance of other HVAC systemsin other houses. If two
`otherwise identical houses are located next door to each other
`
`and have gas furnaces, but oneis rated at 50,000 BTUsand the
`other is rated at 100,000 BTUs, the cycle times for the higher-
`capacity furnace should be shorterthan for the lower-capacity
`unit. Ifboth of those same houseshaveidentical furnaces, but
`onehas a cloggedfilter, the cycle times should be longer in the
`house with the cloggedfilter. Because cycling of the HVAC
`system is controlled by the thermostat, those differences in
`cycle time would be reflected in the data sensed by and
`control signals generated by the thermostat. It would be
`advantageous for a thermostat system to be able to use that
`information to diagnose problems and make recommenda-
`tions based uponthatdata.
`These needsaresatisfied byat least one embodimentof the
`invention that includes a system for calculating a valuefor the
`effective thermal mass of a building comprising: at least one
`HVACcontrol system that measures temperature atat least a
`first location conditioned by said HVAC system, and report-
`ing said temperature measurements as well as the status of
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`said HVAC control system; one or more processors that
`receive measurements of outside temperatures from at least
`one source other than said HVAC control systems and com-
`pare said temperature measurements from said first location
`with expected temperature measurements wherein the
`expected temperature measurementsare basedatleast in part
`upon past temperature measurements obtained by said HVAC
`control system and said outside temperature measurements;
`and one or more databasesthatstore at least said temperatures
`measuredat said first location over time; calculating one or
`morerates of change in temperatureatsaid first location; and
`relating said calculated rates of change to said outside tem-
`perature measurements.
`Another embodiment includes a system for calculating a
`value for the operational efficiency of an HVAC system com-
`prising at least one HVAC control system that measures tem-
`perature at at least a first location conditioned by said HVAC
`system, and reporting said temperature measurements as well
`as the status of said HVAC control system; one or more
`processors that receive measurements of outside tempera-
`tures from at least one source other than said HVAC control
`
`systems and compare said temperature measurements from
`said first location with expected temperature measurements
`wherein the expected temperature measurements are based at
`least in part upon past temperature measurements obtained by
`said HVAC control system and said outside temperature mea-
`surements; and one or more databasesthat store at least said
`temperatures measuredatsaid first location over time; calcu-
`lating one or morerates of change in temperatureat said first
`location for periods during which the status of the HVAC
`system is “on”; calculating one or more rates of change in
`temperature at saidfirst location for periods during which the
`status of the HVAC system is “off”; and relating said calcu-
`lated rates of change to said outside temperature measure-
`ments.
`
`A further embodiment includes a system for evaluating
`changes in the operationalefficiency ofan HVAC system over
`time comprising at least one HVAC control system that mea-
`sures temperature at at least a first location conditioned by
`said HVAC system, and reporting said temperature measure-
`ments as well as the status of said HVAC control system; one
`or more processors that recelve measurements of outside
`temperatures from at least one source other than said HVAC
`control systems and comparesaid temperature measurements
`from said first location with expected temperature measure-
`ments wherein the expected temperature measurements are
`based at least in part upon past temperature measurements
`obtained by said HVAC control system andsaid outside tem-
`perature measurements; and one or more databasesthat store
`at least said temperatures measuredat said first location over
`time.
`A further embodimentincludes a system for detecting and
`correcting for anomalous behavior in HVAC control systems
`comprising a first HVAC control system that measures tem-
`perature at at least a first location conditioned by said first
`HVACsystem, and reporting said temperature measurements
`as well as the status ofsaid first HVAC control system; at least
`a second HVACcontrol system that measures temperatureat
`at least a second location conditioned by said second HVAC
`system, and reporting said temperature measurements as well
`as the status of said second HVAC control system; one or
`more processors that recetve measurements of outside tem-
`peratures from at least one source other than said first and
`second HVACcontrol systems and compare said temperature
`measurements from said first HVAC controls system and said
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`US 8,423,322 B2
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`5
`second HVAC control system and said outside temperature
`measurements; and one or more databases that store said
`temperatures measurements.
`In at least one embodiment, the invention comprises a
`thermostat attached to an HVAC system, a local network
`connecting the thermostat to a larger network such as the
`Internet, and one or more additional thermostats attached to
`the network, and a server in bi-directional communication
`with a plurality of such thermostats. The server logs the
`ambient temperature sensed by each thermostat vs. time and
`the signals sent by the thermostats to their HVAC systems.
`The server preferably also logs outside temperature and
`humidity data for the geographic locations for the buildings
`served by the connected HVAC systems. Such informationis
`widely available from various sources that publish detailed
`weather information based on geographic areas such as by
`ZIP code. Theserver also stores other data affecting the load
`upon the system, such as specific model of HVAC system,
`occupancy, building characteristics, etc. Some of this data
`may be supplied by the individual users of the system, while
`other data may come from third-party sources such as the
`electric and other utilities who supply energyto those users.
`Combining these data sources will also allow the server to
`calculate the effective thermal mass of the structures condi-
`tioned by those thermostats. By combining data from mul-
`tiple thermostats in a given neighborhood, the system can
`correctfor flawsin the location ofa given thermostat, and can
`evaluate the efficiency of a given system, as well as assist in
`the diagnosis of problems and malfunctions in such systems.
`This and other advantages of certain embodiments of the
`invention are explained in the detailed description and claims
`that make reference to the accompanying diagramsand flow-
`charts.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows an example of an overall environment in
`which an embodimentof the invention may be used.
`FIG.2 showsa high-level illustration ofthe architecture of
`a network showing the relationship between the major ele-
`ments of one embodimentof the subject invention.
`FIG. 3 shows an embodimentof the website to be used as
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`part of the subject invention.
`FIG. 4 showsa high-level schematic ofthe thermostat used
`as part of the subject invention.
`FIG. 5 shows one embodimentof the database structure
`
`usedas part of the subject invention
`FIGS. 6a and 66 show graphical representations of inside
`and outside temperatures in two different homes, one with
`high thermal mass and one with low thermal mass.
`FIGS. 7a and 76 show graphical representations of inside
`and outside temperatures in the same homesas in FIGS. 6a
`and 65, showingthe cycling ofthe air conditioning systems in
`those houses.
`FIGS. 8a and 84 show graphical representations of inside
`and outside temperatures in the same homeasin FIGS. 6a and
`7a, showing the cycling ofthe air conditioning on two differ-
`ent days in order to demonstrate the effect of a change in
`operating efficiency on the parameters measured bythe ther-
`mostat.
`
`FIGS. 9a and 964 show the effects of employing a pre-
`cooling strategy in two different houses.
`FIGS. 10a and 106 show graphical representations of
`inside and outside temperatures in two different homes in
`order to demonstrate how the system can correct for errone-
`ous readingsin one houseby referencing readings in another.
`
`6
`FIG. 11 is a flowchart illustrating the steps involved in
`calculating the effective thermal mass of a home using the
`subject invention.
`FIG. 12 is a flowchart illustrating the steps involved in
`determining whether an HVAC system has developed a prob-
`lem that impairs efficiency using the subject invention.
`FIG. 13 is a flowchart illustrating the steps involved in
`correcting for erroneous readings in one housebyreferencing
`readings in another using the subject invention.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENT
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`FIG. 1 shows an example of an overall environment 100 in
`which an embodiment of the invention may be used. The
`environment 100 includesan interactive communication net-
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`work 102 with computers 104 connected thereto. Also con-
`nected to network 102 are one or more server computers 106,
`which store information and make the information available
`
`to computers 104. The network 102 allows communication
`between and among the computers 104 and 106.
`Presently preferred network 102 comprises a collection of
`interconnected public and/or private networksthat are linked
`to together by a set of standard protocols to form a distributed
`network. While network 102 is intended to refer to whatis
`now commonlyreferred to as the Internet, it is also intended
`to encompass variations which may be made in the future,
`including changesadditions to existing standard protocols.
`When a user of the subject invention wishes to access
`information on network 102, the buyer initiates connection
`from his computer 104. For example, the user invokes a
`browser, which executes on computer 104. The browser, in
`turn, establishes a communication link with network 102.
`Once connected to network 102, the user can direct the
`browser to access information on server 106.
`
`One popular part of the Internet is the World Wide Web.
`The World Wide Web contains a large number of computers
`104 and servers 106, which store HyperText Markup Lan-
`guage (HTML) documents capable of displaying graphical
`and textual information. HTMLis a standard coding conven-
`tion and set of codes for attaching presentation and linking
`attributes to informational content within documents.
`
`The servers 106 that provide offerings on the World Wide
`Webare typically called websites. A website is often defined
`by an Internet address that has an associated electronic page.
`Generally, an electronic page is a documentthat organizes the
`presentation of text graphical images, audio and video.
`In addition to the Internet, the network 102 can comprise a
`wide variety of interactive communication media. For
`example, network 102 can include local area networks, inter-
`active television networks, telephone networks, wireless data
`systems, two-way cable systems, andthelike.
`In one embodiment, computers 104 and servers 106 are
`conventional computers that are equipped with communica-
`tions hardware such as modem or a network interface card.
`The computers include processors such as those sold by Intel
`and AMD. Other processors may also be used, including
`general-pur