Heating and cooling control methods and systems

[0001] This is a continuation of Provisional Patent Application U.S. 61/139,327 filed Dec 19, 2008.

[0002] The presently claimed invention is related to the field of heating, ventilation and air conditioning (HVAC). More particularly, the presently claimed invention is related to methods and systems for controlled heating and cooling in order to reduce costs and the carbon footprint of said heating and cooling by optimizing the use of fresh air ventilation (FAV).

[0003] Heating, ventilating, and air conditioning (HVAC), sometimes referred to as climate control, involves closely regulating humidity and temperature in order to maintain a comfortable, safe and healthy environment inside a building. HVAC has been described in detail in “Simplified design of HVAC systems” (William Bobenhausen—1994—Technology & Engineering). HVAC system settings are controlled by a thermostat inside a building and typically include a controller device that adjusts the temperature settings for different times of day and different days of the week. The controller device acts as a programmable interface with users of the building. Over many years there have been many improvements in the components of HVAC systems including higher efficiency systems and improved system controllers. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) fulfills its mission of advancing HVAC and refrigeration to serve humanity and promote a sustainable world through research, standards writing, publishing and continuing education. ASHRAE have suggested standards (e.g., ASHRAE Standard 62.2) for ventilation and acceptable indoor air quality that requires fresh air to be ventilated into a house or building to at least a minimum level. To provide an informative background of information, ASHRAE Standard 62.2 and other information about HVAC provided by ASHRAE are hereby incorporated by reference.

[0004] Existing HVAC systems are shown in FIG. 1 which provides a schematic of a building that includes an HVAC system that includes heating and cooling devices, heat exchangers, fans, ductwork and dampers. Said system is controlled by a controller designed to determine switch-point on/off settings for elements of the HVAC system. The controller achieves a comfortable indoor setting by determining timing of switch points during continuous monitoring the indoor environment from one or multiple sensors that includes for example thermostats and humidistats. One significant drawback with such HVAC systems is that they do not comply with ASHRAE Standard 62.2 because they typically do not provide any outside ventilation capability.

[0005] In recent years as a result of improvements in building engineering, fresh air impact has declined as buildings have become more airtight. Fewer drafts means improved heating and cooling efficiency. Importantly it has also meant that indoor air can be stale and some would argue not so healthful. To that end improvements in HVAC have been sought that involve finding ways to sample outside air to provide ventilation. Some solutions use heat-exchangers to conserve the energy in a building. Improved HVAC systems are shown in FIG. 2 which provides a schematic of a building that includes an HVAC system similar to that shown in FIG. 1 but with the additional capability of fresh air ventilation using a selectively operable damper and fan. This type of system is present in some modern HVAC systems (e.g., Aprilaire Model 8126 Ventilation Control System, or Honeywell Fresh Air Ventilation System Power-Open Spring-Closed Damper & W8150A Control) and is also controlled by a controller. Such controllers typically prevent the system from sampling outside air when temperatures are below or above a certain limit. One significant drawback with currently available ventilation with HVAC is too little fresh air ventilation or random timing of control of fresh-air sampling that causes poor energy efficiency in the HVAC system. Some improvements, such as U.S. Pat. No. 7,044,397, are designed to improve fresh air ventilation have been made by determining a fraction of time that the fresh air intake must be open during anticipated future system calls of the HVAC system to meet a desired ventilation threshold. Another improvement such as U.S. Pat. No. 6,095,426 involves feedback and feedforward control strategies and a method of controlling such apparatus for improved performance. Whilst these improvements in ventilation capability are built into the HVAC system their control is notably not integrated with the HVAC controller.

[0006] Existing literature clearly demonstrates that using outside ventilation as part of a mixed-mode cooling system can reduce building operating costs and carbon emissions (e.g., see ASHRAE Transactions: 2006; 112: 281-3571). Typically such cooling methods are built on individual trial and error principles and do not rely on optimized mathematical algorithms that account for outside conditions and inside occupant comfort. Such buildings are often controlled by individual occupants opening windows and doors to permit outside ventilation. Whilst this approach is very effective it does not adapt quickly to outside conditions and does not function without active occupant participation and is not inherently optimized to minimize costs. There is clearly a need for a more adaptive automated approach that might be integrated with existing HVAC capability. A recent publication by Spindler and Norford (2008) describes controlling algorithms for mixed-mode cooling strategies including use of natural ventilation (Naturally ventilated and mixed-mode buildings—Part I: Thermal modeling. Building and Environment, in press (doi: 10.1016/j.buildenv.2008.05.019)). A second publication by Spindler and Norford describes ways to optimize the controlling algorithms for mixed mode cooling (Naturally ventilated and mixed-mode buildings—Part II: Optimal control. Building and Environment In Press, (doi: 10.1016/j.buildenv.2008.05.018)). Important overall conclusions from these studies are that HVAC control algorithms can be built using linear thermal modeling and can be optimized for use in buildings. What is apparent from the literature as well as in fact from a review of existing HVAC control equipment, is the surprising lack of automated integration of mixed-mode heating and cooling using a combination of ventilation and HVAC.

[0007] The presently claimed invention (referred to hereinafter as a “Smart Stat Controller” or “Smart Thermostat” or alternatively “Smart-Stat”) overcomes the random timing and inefficient use of fresh air ventilation by incorporating a novel control system. FIG. 3 provides a schematic of a building that includes an HVAC system similar to that shown in FIG. 2 but with the additional capability of incorporating the present invention. FIG. 4 provides a schematic of a typical controller, whilst FIG. 5 provides a schematic of the present invention's programmable controller or smart thermostat (Smart-Stat). FIG. 6 provides a second schematic of the present invention's programmable controller configured with an existing typical thermostatic controller. The Smart Thermostat system is designed to optimize the timing of use of fresh air based on current outside conditions in combination with data from weather forecasts. Specifically the Smart Thermostat controller controls air-flow and HVAC in buildings by using mathematical algorithms that monitors regional weather forecasts in combination with current outside air monitoring. The present invention saves energy and reduces the carbon footprint of heating and cooling by achieving optimal timing of HVAC combined with use of ambient air ventilation as an alternative to heating and cooling. In short, the Smart-Stat controller uses outside ventilation to achieve the desired result of providing a comfortable inside air temperature and quality against user-programmable set-points.

[0008] Previously described improvements in HVAC utilize counter-flow systems that radiate heat from incoming and outgoing air. In addition, some of the said improved HVAC systems include temperature sensors for the inside and outside air that are used to set dampers flow rate in order to conserve energy. Thus it can be envisioned one aspect of the concept of the present Smart-Stat invention can be seen within these improvements to HVAC. Specifically, the existing HVAC improvements include monitoring inside and outside temperatures in order to control energy flow between incoming and outgoing air. Some of these systems integrate this control with weather information but importantly, the improved indoor ventilation is only a fraction of the air flow. Furthermore, unlike the present invention, the improved HVAC systems sample outside air with the purpose of improved air quality and the outside air is heated or cooled in just the same way as indoor air, all under the control of a typical thermostatic controller. Importantly the present invention uses the existing HVAC system to circulate air and bring-in outside air to over-ride the use of heating and cooling as used in the typical thermostat controller and improved HVAC systems. Specifically in none of the HVAC improvements is there a system for using the outside air as an alternative source of heating or cooling with the specific goal of reducing costs and reducing the carbon footprint of HVAC systems.

[0009] Another existing technology that shares similarities with the present invention is the use of whole house ventilation fans or window fans to cool or warm a house using outside air. Here, the purpose is similar to that described by the present invention: namely energy saving using outside air. Sometimes called “Whole House Ventilation” or “Whole House Fans”, these systems provide a fan often mounted in the ceiling that vents air into the attic where the air is lost passively or expelled using another fan in the roof space. These systems are often controlled using a switch, activated by a user and requires that said user has opened windows within the home. Sometimes the fans are activated by the user and rely upon opened wall ventilation panels to allow balanced air flow. Sometimes the fans are activated by temperature sensors. Importantly, in none of these examples is there an attempt to integrate or automate the Whole House Ventilation with an existing HVAC nor is there any integration with the buildings HVAC Control system or control software. Thus the user has to switch them on manually and manually switch off the HVAC system. More importantly the Whole House System does not bring together a monitoring system for inside and outside conditions with time and additionally does not integrate this with weather data monitoring to predict an optimal use of outside air. Thus the present invention overcomes the limitations of the existing systems of HVAC by bringing together such data into logical algorithms that make optimal automated use of outside weather conditions. Initially we modeled the cost saving potential using spreadsheets based on actual temperature data downloaded from the Iowa State University μg Climate 2005, 2006, 2007—Iowa Environmental Mesonet. Significant annual cost savings were possible during certain months (April through October) when temperatures were not extreme.

[0010] Yet another existing technology that shares similarities with the present invention is the use of on-line weather data to monitor local weather forecasts and take proactive steps in system operation and control. Here, the purpose is similar to that described by the present invention: namely using weather forecasting information to make decisions on controlling the HVAC system. However, the present invention uses the weather information to call on outside ventilation in place of HVAC, whereas the existing technologies proactively change the HVAC settings in days preceding weather events by increasing or decreasing cooling or heating in order to place less demand on the system on the day of the weather event. Thus the present invention overcomes the limitations of the existing technological advances in systems of HVAC control by bringing together such data into logical algorithms that monitors outside weather conditions and terminates calls for HVAC, redirecting this into calls for fresh air ventilation by reacting to outside weather conditions.

[0011] Smart-Stat can be linked with home computer monitoring and control systems and computer software systems by using any kind of suitable interface. For example, industry-standard RS-232/RS-485 protocol, or X10-Control or Z-Wave control. X10 is an international and open industry standard for communication among electronic devices used for home automation, also known as domotics. X10 primarily uses power line wiring for signaling and control, where the signals involve brief radio frequency bursts representing digital information. A wireless radio based protocol transport can also be also defined. Z-Wave is a wireless communications standard designed for home automation, such as remote control applications in residential and light commercial environments.

[0012] Smart-Stat uses the National Digital Forecast Database (NDFD) Extensible Markup Language (XML) as a service, accessing local weather data from the National Weather Service's (NWS) digital forecast database. This service, which is defined in a Service Description Document, provides the ability to request NDFD data over the internet and receive the information back in an XML format. The request/response process is made possible by the NDFD XML Simple Object Access Protocol (SOAP) server. The first step to using the web service is to create a SOAP client. The client creates and sends the SOAP request to the server. The request sent by the client then invokes one of the server functions. There are currently nine functions available including: NDFDgen(), NDFDgenLatLonList(), LatLonListSubgrid(), LatLonListLine(), LatLonListZipCode(), LatLonListSquare(), CornerPoints(), NDFDgenByDay(), and NDFDgenByDayLatLonList(). Said weather data will include a time-based forecast of temperature and relative humidity as well as hours of sunshine or cloud-cover. Upon receiving said weather data, the present invention monitors local weather forecasts for the coming days ahead and integrates this information with current inside and outside temperatures. Computational algorithms based on the local forecasts and local data are then used by Smart-Stat to make logical choices that control the HVAC system and determine appropriate use of fresh air ventilation. The system is designed not to operate ventilation if the outside air is below 40° F. or above 100° F. and if the relative humidity is above 60%.

[0013] The present invention is also able to use its outside/inside/weather monitoring capability to compute models of heat-loss and heat-gain for the local building in which it is placed. Such models represent coefficients of heat loss/gain in different environmental conditions and enable more sophisticated algorithms to be computed that will improve the ability of the control system to determine optimal set-points for the HVAC system and determine optimal use of fresh air ventilation. Thus the system learns over time and adjusts set-points accordingly. Another aspect of this monitoring system is its ability to output heat-transfer information to the local user as well as local service/installation companies. Such data output would allow the local users to recognize differences between houses in terms of heat transfer, and enable a data-driven recommendation for improvements in building insulation. The outcome would be improvements in the overall energy consumption of buildings in relation to heating and cooling requirements. Such improvements would have an impact on local and regional carbon footprints regarding energy utilization.

[0014] In light of these developments in the art, a number of patent and other documents are referenced herein which relate to efforts to modify HVAC and to achieve improvements in energy efficiency. These documents are hereby incorporated by reference.

[0015] Thus, for example U.S. Pat. No. 7,044,397 describes improved fresh air ventilation by determining a fraction of time that the fresh air intake must be open during anticipated future system calls of the HVAC system to meet a desired ventilation threshold. Another improvement such as U.S. Pat. No. 6,095,426 describes feedback and feedforward control strategies and a method of controlling such apparatus for improved performance.

[0016] U.S. Pat. No. 5,746,653 describes an apparatus mounted in for example an attic that can distribute and collect air where a fan draws air from a perforated elongated tube and vents the air as needed in order to provide cooling or heating in a building.

[0017] U.S. Pat. No. 5,761,083 describes an Energy Management and Home Automation system that senses the mode of occupancy of the building. Thus control is different when occupied or unoccupied and heating and cooling based is switched appropriately.

[0018] U.S. Pat. No. 6,095,426 involves feedback and feedforward control strategies and a method of controlling such apparatus for improved performance.

[0019] U.S. Pat. Nos. 6,756,998 and 6,912,429 detects building occupancy status using motion sensor devices interfaced with the controller unit. The system even learns from data inputs and builds an occupancy pattern for each room.

[0020] U.S. Pat. No. 6,766,651 describes use of humidity control and aromas and even pesticidal, bacteriacidal, fungicidal or sporacidal agents can be introduced into the airflow to enhance HVAC.

[0021] U.S. Pat. No. 7,044,397 describes use of fresh air ventilation wherein a fraction of time is determined for fresh air intake opening during anticipated future system calls of the HVAC system to meet a desired ventilation threshold.

[0022] U.S. Pat. No. 7,343,226 describes a system and method of controlling an HVAC system that incorporates outside temperature monitoring and is linked to demand and consumption rate from the distribution network.

[0023] U.S. Pat. No. 7,434,742 describes a thermostat having a microprocessor and network interface to obtain user-specified information from a remote service provider plus a display device responsive to the microprocessor for displaying user-specified information received via the network controller from the remote service provider.

[0024] Patent WO/2007/094774 describes a method and apparatus for maintaining an acceptable level of outside air exchange rate in a structure. The natural ventilation rate is determined as a function of the outdoor air temperature, and the amount of mechanically induced ventilation that is used to supplement the natural air ventilation is controlled such that the sum of the natural occurring ventilation and the mechanically induced ventilation is maintained by a substantially constant predetermined level.

[0025] Patent WO/2007/117245 describes a controller for an HVAC & R system is provided with the Internet connection to weather forecast information in order to determine proactive steps that increase heating or decrease cooling, or alternatively decrease heating or increase cooling, prior to changes in weather beginning to occur. The patent also describes using the proactive monitoring system to control fresh air circulation rate.

[0026] HVAC engineers continue to research ways to optimize the operation of heating and cooling systems, however despite various publications, practical applications are not apparent. For example, although Zaheer-uddin and Zheng describe optimal control of HVAC (Energy Conversion and Management (2000) 41, 49-60), whilst Chen describes adaptive predictive control for heating applications (Energy and Buildings (2002) 34, 45-51) and more recently, He, Cai and Li describe use of multiple fuzzy model-based temperature predictive control systems (Information Sciences (2005) 169, 155-174) none of these publications describe practical examples of improved control systems.

[0027] As can be seen from the foregoing review of the art, there is intense interest in improving HVAC and its impact on energy utilization and carbon footprint. There exist problems in various aspects of the known technologies, from using more efficient heat exchangers to improved monitoring and the like. Accordingly, there remains a need in the art for novel methods and compositions which provide improvements in energy utilization and carbon footprint control. The present invention provides a valuable additional set of novel methods and control systems which meet these needs while placing a minimal burden on HVAC systems needing modification according to this technology.

[0028] A primary object of the present invention is to provide a user-programmable controller having mathematical algorithms that monitors and reacts to local current ambient air conditions in order to provide logical control signals that will control the use of whole house ventilation as an alternative to HVAC in a whole-building heating and cooling system for improved energy efficiency.

[0029] Another primary object of the present invention is to provide a user-programmable controller having mathematical algorithms that monitors and reacts to local weather forecasts, current ambient air conditions in order to provide logical control signals that will control the use of whole house ventilation as an alternative to HVAC in a whole-building heating and cooling system for improved energy efficiency.

[0030] Another embodiment of the present invention is to provide a user-programmable controller having mathematical algorithms that monitors and reacts to local weather forecasts, current ambient air conditions in order to provide logical control signals that will optimize the use of fresh air ventilation in combination with heating and cooling cycles in a whole-building heating and cooling system for improved energy efficiency.

[0031] And another embodiment of the present invention is to provide a user-programmable controller having mathematical algorithms that monitors and reacts to local weather forecasts and current ambient air conditions and models of building heat retention and loss in order to provide logical control signals that will optimize the use of fresh air ventilation in combination with heating and cooling cycles in a whole-building heating and cooling system for improved energy efficiency.

[0032] Yet another embodiment of the present invention is to provide a user-programmable controller having mathematical algorithms that monitors and reacts to local weather forecasts, current ambient air conditions and loss in order to provide logical control signals that will optimize the use of heating and cooling cycles in a whole-building heating and cooling system for improved energy efficiency.

[0033] And yet another embodiment of the present invention is to provide a user-programmable controller having mathematical algorithms that computes building heat-loss models in order to provide modified algorithms for an improved overall energy efficiency of a programmable HVAC system by reactive evaluation of local weather forecasts, current ambient air conditions and models of building heat retention and loss in different environmental conditions.

[0034] Yet another embodiment of the present invention is to provide an upgradeable system of optimized HVAC control based on any combination of models and algorithms based on local weather forecasts, current ambient air conditions and models of building heat retention and loss. Users can introduce optimized control initially with only heating and cooling capability, but later add fresh air ventilation capability using the same system controller.

[0035] Still further objects and advantages will become apparent to those skilled in the art from a consideration of the entire disclosure provided herein, including the accompanying drawings and appended claims. Accordingly, departures in form and detail may be made without departing from the scope and spirit of the present invention herein described in the appended claims.

[0045] The following detailed description should be read with reference to the drawings. The drawings are not to scale and depict illustrative examples and embodiments and are not intended to limit the scope of the present invention. A typical building is presented schematically in FIG. 1 and a building incorporating a ventilation system is presented schematically in FIG. 2. A building incorporating the Smart-Stat controller is presented schematically in FIG. 3. Typical controllers are presented schematically in FIG. 4, with controllers incorporating Smart-Stat presented schematically in FIG. 5 and FIG. 6.

[0046] The present invention is directed to mathematical algorithms incorporated into a controller 20 shown schematically in FIG. 5 and a method of determining control signals that are dependent on said mathematical algorithms and user programming that integrates information from multiple sensors 21, thermostats as well as weather information 22. Used in any home or building, the controller controls heating, cooling and ventilation systems in order to reduce costs and the carbon footprint of said heating and cooling by optimizing the use of fresh air ventilation. The controller works with typical HVAC systems generally in buildings and homes.

[0047] In addition to the controller and its mathematical set-point algorithms, the system requires that the house has appropriate outside ventilation capability. This requires installation of an outside vent as well as ducting, filters, dampers and suitable vent fans and additionally requires a balanced ventilation capability where the volume of air taken inside the building is balanced by a similar volume of air vented outside of the building. Typically, fans use less than 10% of the energy of a typical HVAC system calling on Heating or Cooling. Thus the present invention can in certain circumstances reduce the energy consumed to heat and cool buildings.

[0048] The Smart-Stat algorithms are programmed into the controller and enable the controller to identify user-determined set-points alongside data from one or multiple internal temperature sensors. The user-determined set-points are also linked to time of day and day of week in a manner similar to typical thermostat devices available today. In such typical thermostat devices the controller will call for cooling or heating depending on the set points and conditions determined by the sensors in the building. The present invention is capable of interrupting the call for cooling or heating depending on whether the mathematical algorithms identify suitable outside weather conditions that permit the use of outside air cooling or outside air heating. Thus the call for heating or cooling can be redirected by the present invention in order to call for ventilation instead of heating or cooling.

[0049] The Smart-Stat controller includes a digital display system and digital keypad that acts as a user-interface for immediately adjusting set-points and timing of set-points. The timing can be time of day as well as day of week. The system can also interface with a computer for more refined control setting and linking with building automation software systems. The Smart-Stat is also capable of displaying information on HVAC performance over time and specifically can display the Heat transfer coefficient (U-value) of the building comparing this with a database of similar buildings. Specifically the Smart-Stat can inform the user of the building's relatively poor, average or good performance in terms of heat transfer. This information could be used by the user to make decisions about installing additional insulation or having a more rigorous home survey of insulation or draftproofing.

[0050] Having generally described this invention, including methods of making and using the novel compositions and the best mode thereof, the following examples are provided to extend the written description and enabling disclosure. However, those skilled in the art will appreciate from this disclosure that the invention may be varied in accordance with the disclosure and guidance provided herein, without departing from the heart of the invention. Further, the specifics provided in the examples below should not be construed as limiting. Rather, for an appreciation of the scope of the invention comprehended by this disclosure, reference rather should be had to the appended claims and their equivalents.

[0051] A whole-house fan (e.g., a typical direct-drive or belt-drive and thermally-protected fan is obtained DIY suppliers) was modified to fit an insulated opening in the ceiling of a conventional insulated two-story timber-framed house. The fan is controlled manually by a hand-held switch and used in conjunction with open or closed windows. The fan is conventional, multi-speed, 3-bladed and capable of blowing air at more than 1,000 cubic feet per minute. By controlling the fan in different environmental conditions throughout the year, we determined that outside air is an effective way of cooling a house when outside temperature and humidity is suitable. The system was not very effective when windows were partially closed and almost completely ineffective when windows were completely closed.

[0052] Daily maximum and minimum temperature data as well as hourly temperature data for different cities and states were downloaded from publicly available databases (e.g., Iowa Environmental Mesonet). These data were from different years such as 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007. A computer modeling spreadsheet was devised to evaluate and compare the costs of using a conventional thermostat controller compared with the present invention. The modeling system was also evaluative, allowing different methods of control and different set-points to be evaluated. Using this system we found that energy savings of up to 25% were possible on certain times of day and on different days energy savings of an extra 15% were possible. Savings were not possible on all days of the year but in no case was the present invention less efficient when compared with our model of a conventional thermostatic controller.

[0053] We concluded that the present invention has the potential to decrease energy costs of heating and cooling over a period of time and over the years. With a saving of 10-20% in energy costs the Smart-Stat controller quickly recovers the added costs of investment. Most importantly the present invention presented essentially no risk of increasing costs over a prolonged period of use.

[0054] Thermal heat loss equations (see table below) can be calculated based on Heat Loss equations (Simplified design of HVAC systems. William Bobenhausen, 1994, Technology & Engineering) or U-factors (quantified as BTU/ft²° F.hr). Using information provided in chapter 5 we computed the U-factor for different rooms by using the published BTU/° F.hr. There was considerable variation between rooms even in the same house (ranging from 0.1 to 0.3 BTU/sq.ft.° F.hr). It is obvious that the range of variation in thermal loss values will be even greater between different houses.

[0055]

	Heat Loss
	(BTU/	Surface Area	Thermal Loss (UA)
	° F. hr)	(sq. ft)	(BTU/sq. ft. ° F. hr)
Room A (15 × 10 × 10)	46.3	150	0.309
Room B (15 × 20 × 10)	55	300	0.183
Room C (10 × 10 × 10)	9.7	100	0.097
Room D (15 × 15 × 10)	63.3	225	0.281
Room E (10 × 15 × 10)	40	150	0.267
Room F (6 × 15 × 10)	14	90	0.156
Room G (12 × 15 × 10)	23.4	180	0.130
Room H (9 × 15 × 10)	26.6	135	0.197
Total/Average	34.9	1330	0.203
Building Thermal heat loss equation: (QA = U · A · (Ti − Ta))
Q = Total hourly rate of heat loss (Btu/hr) as measured for each building.
U = Heat transfer coefficient (Btu/hr-sqft-° F.) can be determined for each building.
A = Net area for heat transfer (sq. ft) measured on the drawing/building.
Ti = Inside design temperature (° F.) preset on thermostat (eg. 68° F.).
Ta = Outside design temperature (° F.) depends on outside temperatures.

[0056] Some houses show significantly worse performance than others which can later be shown to be due to poorer insulation or older insulation materials that had settled and hence were less effective. These data reveal the value of a Smart-Stat monitoring device that quantifies heat loss in a given house relative to outside temperatures when heating has terminated. This house-specific U-factor permits then an estimate of the house-specific coefficient of heat loss and answers the question of whether a particular house is relatively better or worse than another in terms of heat loss. Such heat-loss monitoring data is not only valuable in a smart thermostat for each specific house. Thus for example the data can be used as a source of guidance for house owners and in a database by professionals leading to potentially significant energy savings by pointing to improvements in insulation for a given house.

[0057] A prototype of the Smart-Stat system is currently programmed into a PIC 18 chip from Microchip Technology Inc. One example used the PIC18F4XK20 Starter Kit. Any programmable microcontroller device from any manufacturer may be used with the envisioned software protocols claimed herein provided sufficient processing capability exists. For example, the PIC 18, PIC 24 and PIC 32 architecture microprocessor from Microchip are sufficient. The device can be programmed using the Microchip MPLAB C Compiler. The microprocessor must have a real time clock, standard on many PIC controllers. The thermostat consists of two components: the controller that mounts near the air handling equipment and the wall-mounted microprocessor-controlled display unit, allowing temperature control via several methods. Locally, simply push the buttons on the wall-mounted unit's thermostat-like user interface. Remote or automated control is via RS-232/485 remote interfaces, making adjustments from the RS-232/485 home control system. The thermostat unit controls all standard functions of gas/electric or heat-pump HVAC systems, including heating (two-stage heating on heat-pump systems), cooling and fan control. It connects to HVAC systems via standard thermostat connections, and connects to the wall-display unit via a 4-wire connection (2 power, 2 data). The controller also offers fuse-protected relay outputs to the mechanical system, responds to polling requests by sending current temperature, set-point, mode and fan status.

[0058] The programmable microprocessor contains multiple subroutines that control the fans, call for heating or cooling or ventilation and also allow the user to change set points and time variables in the microcontroller. The control interface utilizes relay devices to handle the electrical load required for HVAC control. Although these connections are essential to the functionality of the microcontroller interface with the HVAC these connections are well known in the art and need not be described in detail herein.

[0059] What is important is the fundamental concept of using ambient air as a source of heating and cooling as well as the algorithms that determine when the system calls for heating or cooling or ventilation. It is of course these algorithms programmed into the Smart-Stat microcontroller that saves on energy use and costs. The algorithms and subroutines that interface with temperature and humidity sensors and weather-data are described in the following examples.

[0060] The temperature sensor and humidity sensor subroutines required to function with the Smart-Stat programmable microprocessor allow a different choice than using energy to heat or cool. Temperatures are in degrees Fahrenheit (F).

[0061] During a HEATING CYCLE there is a cascade of logical on/off decisions determined by the Smart-Stat controller as follows (also shown in table below):

• • [0062] 1. Controller stays INACTIVE when temperature inside building is above set-point, causing controller not to call for heating. Since cooling is inactive the controller will not call for cooling.
  • [0063] 2. Controller calls for HEAT when temperature inside building is below set-point. Controller permits HEAT provided VENT not activated by outside temperature or weather data decision point.
  • [0064] 3. Controller calls for VENT when temperature outside is above temperature inside building and humidity is within set-points limits. This call for VENT over-rides the call for heating.
  • [0065] 4. Controller calls for VENT when temperature outside is forecast to be above temperature inside building within a period of time set by the user or set by the controller using its calculation of the heat-loss coefficient of the building. This call for VENT over-rides the call for heating and is also determined by the humidity set-point limits.
  • [0066] 5. Controller calls for HEAT when temperature inside building is below a minimum temperature that is considered a risk in terms of freezing water. This call for HEAT by the controller over-rides all other set-points derived from sensors or weather data and closes all dampers and vents associated with the ventilation system.

[0067]

	Set	Inside	Outside
HEATING CYCLE	Point	Sensor	Sensor	Outcome
Cold inside,	Temperature	70 F.	65 F.	75 F.	—
Warm outside	Switch On/Off.	—	On	On	Heat-Vent
Cold inside,	Temperature	70 F.	65 F.	65 F.	—
Cold outside	Switch On/Off.	—	On	Off.	Heat-HVAC
Warm inside,	Temperature	70 F.	75 F.	65 F.	—
Cold outside	Switch On/Off.	—	Off.	On	Zero
Warm inside,	Temperature	70 F.	75 F.	75 F.	—
Warm outside	Switch On/Off.	—	Off.	Off.	Zero

[0068] During a COOLING CYCLE there is a cascade of logical on/off decisions determined by the Smart-Stat controller as follows (also shown in table below):

• • [0069] 1. Controller stays INACTIVE when temperature inside building is below set-point, causing controller not to call for cooling. Since heating is inactive the controller will not call for heating.
  • [0070] 2. Controller calls for COOL when temperature inside building is above set-point. Controller permits COOL provided VENT not activated by outside temperature or weather data decision point.
  • [0071] 3. Controller calls for VENT when temperature outside is below temperature inside building and humidity is within set-points limits. This call for VENT over-rides the call for cooling.
  • [0072] 4. Controller calls for VENT when temperature outside is forecast to be below temperature inside building within a period of time set by the user or set by the controller using its calculation of the heat-gain coefficient of the building. This call for VENT over-rides the call for cooling and is also determined by the humidity set-point limits.

[0073]

	Set	Inside	Outside
COOLING CYCLE	Point	Sensor	Sensor	Outcome
Warm inside,	Temperature	80 F.	85 F.	75 F.	—
Cold outside	Switch On/Off	—	On	On	Cool-Vent
Warm inside,	Temperature	80 F.	85 F.	85 F.	—
Warm outside	Switch On/Off	—	On	Off	Cool-HVAC
Cold inside,	Temperature	80 F.	75 F.	85 F.	—
Warm outside	Switch On/Off	—	Off	On	Zero
Cold inside,	Temperature	80 F.	75 F.	75 F.	—
Cold outside	Switch On/Off	—	Off	Off	Zero

[0074] The weather-data subroutines required to function with the Smart-Stat programmable microprocessor.

[0075] The Smart-Stat system may also be configured to work with for example an RCS Model TXB16 X10 Bi-Directional HVAC Thermostat using X10 communication via power lines, or Model TR16 Communicating Thermostat using RS485 data communication via standard serial ports. However, any HVAC system can be configured to be controlled by the current invention as any simple controller system having an appropriate interface and appropriate switching system is all that is required. A stand-alone Smart-Stat controller unit can also be envisioned, similar in outside appearance to those available today from many stores. Such a stand-alone controller can be custom designed to incorporate all of the required control features and computing algorithms and be configured with WiFi capability so as to interface with home computer systems.

[0076] The Smart-Stat system uses computerized control and mathematical algorithms to interface with the Communicating Thermostat and is time-based and day-based but is also linked to Weather data and an algorithm that learns heat loss and heat gain for the building. First and primary control is taken by a freeze-protection system that activates heating if temperatures fall below a preset temperature (eg., 50° F.). This building protection setting over-rides all other settings. During times requiring heat, the system calls for heating based on temperature sensors in the house and user-set temperature settings linked to time of day and day of week. The call for heating is interruptible by the Smart-Stat based on weather information and learned information about heat loss and gain that is specific to the building. During times requiring cool, the system calls for cooling based on temperature sensors in the house and user-set temperature settings linked to time of day and day of week. The call for cooling is interruptible by the Smart-Stat based on weather information and learned information about heat loss and gain that is specific to the building. The whole system is programmable from a touchpad display as well as by being able to interface with a computer using WiFi or is hard-wired. The Smart-Stat is also capable of switching on outside air ventilation in place of cooling or heating, depending on the outside temperature and humidity sensors and weather data.