Ventilation Systems and Methods

Abstract

This application describes methods and systems for ventilating a building. A method for ventilating a building includes drawing in air, using a central fan, for heating or cooling at least a portion of the building and exhausting air from the building using at least one exhaust fan. The exhaust fan can be automatically operated during time periods when the central fan is not switched on. The method further includes automatically opening a damper, during at least a portion of the time periods, such that fresh air enters the building through the damper

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 61/470,801, filed on Apr. 1, 2011, the entire content of which is incorporated herein by reference.

BACKGROUND

New energy efficient homes are being constructed almost air tight. So tight they now need mechanical ventilation added to bring in just enough fresh air to keep the occupants healthy.

ASHRAE (American Society of Heating and Refrigeration and Air-conditioning Engineers) provides a formula for the amount of ventilation: 7.5 cfm (N+1)+(A×0.01) where N=number of bedrooms, A=square footage of the home. So for example a 4 bedroom, 2,000 sq ft home would require: 7.5×5+(2,000×0.01)=57.5 CFM continuously of fresh air. The homes are measured for air leakage that can be subtracted from the calculated requirement. For this example assume we measured 27.5 CFM of leakage. That leaves 30 CFM we need to bring in continuously to meet the ventilation standards. Coming standards are going to penalize builders for over ventilating so the more precise the method of control the better.

An inexpensive and effective method to bring in fresh air is to use the central fan and existing duct work from the heating and air-conditioning system to bleed in an amount of fresh air from an outside known source and distribute it throughout the home using a controller such as the AirCycler™ available from Lipidex Corporation of Marshfield, Mass. Techniques for accomplishing this are described in U.S. Pat. Nos. 5,547,017 & 5,881,806 & 6,431,268, which are incorporated herein by reference.

With this known system you could bring in 90 cfm ⅓ of the time to meet the 30 cfm continuous ventilation requirement. The AirCycler™ control monitors the thermostat and if it hasn't run ⅓ of the time from heating or cooling, it will bring on the central fan to bring in the remaining requirement of fresh air.

One issue with using the central fan to provide needed ventilation is that a central fan will typically draw a lot of power (e.g. 400 W) to move a relatively small amount of air. By contrast, a typical bathroom exhaust fan only uses 30 W.

U.S. Pat. No. 7,798,418, which is incorporated herein by reference, discloses three alternative methods for ventilating a space having a central fan (for heating/cooling) and a bathroom exhaust fan.

Method 1:

the exhaust fan comes on whenever the central fan comes on. This provides “balanced” ventilation. The central fan is used to bring air into the building, and a bathroom exhaust ventilation fan is used to exhaust the same volume of air out of the building.

Some jurisdictions require “balanced” ventilation. They are concerned with where the fresh air comes from when you exhaust stale air. In hot humid climates you don't want to depressurize a building because that could pull outside moisture into the walls.

In other jurisdictions, the balanced approach is not required, and ventilation may be achieved by either only supplying fresh air (which will force out stale air by leakage out of the building), or by only exhausting stale air (which will be replaced by leakage into the building).

Method 2:

the exhaust fan is turned on whenever the Central fan is off. The idea is you make up the required ventilation you're not getting when the central fan is off by turning on the ventilation fan. With this technique, you do not have to run the large expensive central fan for ventilation, only heating and cooling. However this method could cause over-ventilation as a result of excess exhaust fan run time.

Method 3

the exhaust fan runs independently. A controller determines how many minutes per hour to run the exhaust fan and it monitors fan run time when a person is in the bathroom manually operating the fan, including the “delay” time that the fan runs to continue after the person leaves, then subtracting that from the required time and making up the difference.

One potential problem with home ventilation systems is the possibility that unhealthy air may be drawn into the building. For example, when an exhaust fan is operating, air may leak into the building from the garage, and such air may include volatile organic hydrocarbons (VOCs), which are known to be carcinogenic.

Another potential problem with home ventilation systems is over ventilation, whereby more fresh air than is desired or needed is brought into the building.

SUMMARY

In one aspect, the application describes a method for ventilating a building. The method includes drawing in air, using a central fan, for heating or cooling at least a portion of the building and exhausting air from the building using at least one exhaust fan. The exhaust fan can be automatically operated during time periods when the central fan is not switched on. The method further includes automatically opening a damper, during at least a portion of the time periods, such that fresh air enters the building through the damper.

In another aspect, the application describes a controller for controlling the ventilation of a building. In the building there are a central fan configured to draw in air for heating or cooling at least a portion of the building, at least one exhaust fan adapted to exhaust air from the building, and a damper that, when opened, permits fresh air to enter the building. The controller includes control logic adapted to generate signals to automatically operate the exhaust fan to exhaust air from the building during time periods when the central fan is not switched on and to open the damper during at least a portion of the time periods, such that fresh air enters the building through the damper.

In another aspect, the application describes a method for ventilating a building. The method includes drawing in air, using a central fan, for heating or cooling at least a portion of the building. The central fan is automatically switched on during periods when a heating or cooling system is supplying hot or cold air to the building. The method also includes expelling air from the building using at least one exhaust fan such that the total amount of ventilation of the building resulting from the operation of the central fan and the exhaust fan is controlled to approximate a predetermined amount. The exhaust fan is configured to be operated during periods in which the central fan is not operational.

In another aspect, the application describes a controller for controlling the ventilation of a building having a central fan for distributing air in a heating or cooling system and at least one exhaust fan. The controller includes a control logic adapted to generate signals to operate the at least one exhaust fan during periods when the central fan is not operational, so that the total amount of ventilation of the building resulting from the operation of the central fan and the exhaust fan is controlled to approximate a predetermined amount.

Implementations can include one or more of the following.

Control signals can be received from the controller at the central fan, the at least one exhaust fan and the damper and these can be operated in accordance with the control signals. The central fan can be switched on in accordance with one of the control signals when a heating or cooling system is operating to heat or cool a portion of the building. The exhaust fan can be switched on in accordance with one of the control signals responsive to a manual input. The exhaust fan can be switched off after a predetermined time period. The damper can be automatically opened during a time period when the central fan is switched on. The exhaust fan can be a bathroom exhaust fan. The exhaust fan can be a kitchen exhaust fan.

The controller can be further adapted to generate signals to switch on the central fan in accordance with an operation of a heating or cooling system. The controller can be adapted to generate signals to switch on the exhaust fan responsive to a manual input. The controller can be adapted to generate signals to switch off the exhaust fan after a pre-determined time period. The controller can be adapted to generate signals to open the damper during a time period when the central fan is switched on.

The at least one exhaust fan can be configured to be operated for a first time period responsive to a manual input and automatically for a second additional time period on determining that the exhaust fan is to be operated for the second additional time period to achieve the approximate predetermined amount of ventilation. Automatically operating the exhaust fan can include operating the exhaust fan during periods when the central fan is not switched on. A damper can be automatically opened to permit the inflow of fresh air into the building during the first time period or the second additional time period.

The exhaust fan can be part of a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV). The controller can be further adapted to automatically open a damper during at least a portion of time periods when the exhaust fan is switched on, such that fresh air enters the building through the damper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a ventilation system.

FIG. 2 is a flowchart of an example process for operating a ventilation system.

FIG. 3 is a flowchart of an example process for operating a ventilation system.

FIG. 4 is a block diagram of a computing system.

DETAILED DESCRIPTION

The present application describes methods and systems for ventilating a building. Referring to FIG. 1, a ventilation system 100 of a building includes a main or central fan 105 that is used for heating and/or cooling at least a portion of the building in connection with a heating or air conditioning system, at least one exhaust fan 110 (such as a bathroom or kitchen exhaust fan), and a damper 115 in communication with the central fan, for example through a controller 120. The central fan 105 can be disposed within the building or in a unit external to the building. Fresh air is drawn in by the central fan 105 and circulated in the building via one or more fresh air ducts 106. In some implementations, air from within the building can be expelled or exhausted from the building through one or more exhaust ducts 108. The controller 120 is usually disposed inside the building, for example on a wall. The controller 120 may include an electronic controller such as a microcontroller, microprocessor or a digital signal processor (DSP). In some implementations, the exhaust fan 110 is switched on during time periods when the central fan 105 is not operating, in order to exhaust stale air from the building. In some implementations, during at least a portion of those time periods, the damper 115 is automatically opened, so that fresh air enters the building through the damper, rather than other, potentially less desirable, routes (e.g. via a leakage from the garage). Even though the example of FIG. 1 illustrates that the damper 115 is disposed in an intake duct 113 connected to the central fan 105, the damper 115 can also be disposed elsewhere in the building. For example, the damper can be disposed on an external wall of the building or in another duct or pipe that facilitates a flow of fresh air. The controller 120 can be configured to send control signals to one or more of the central fan 105, the exhaust fan 110, and the damper 115 to facilitate the automatic operations (e.g. switching on or off). For example, the exhaust fan 110 may be automatically operated by the controller for certain time periods in addition to periods when the exhaust fan 110 is manually operated, for example, using a switch 113. In another example, the controller 120 may send one or more control signals to operate the central fan 105 when the heating or cooling system is operating. The controller 120 may also operate the exhaust fan 110 when a person is using the bathroom (e.g., based on determining if the bathroom light is turned on), and potentially for a period afterwards. The controller 120 may further operate the exhaust fan 110 to perform any additional ventilation needed to achieve a desired amount of ventilation in the building over a predetermined time period (e.g. an hour, a day, or during normal work hours). In some implementations, the exhaust fan may be part of an energy recovery ventilator or a heat recovery ventilator.

The controller 120 can also be configured to send control signals to the damper 115 to automatically open or close the damper 115. In some implementations, the controller 120 can be configured to open the damper 115 during periods when the central fan 105 is operating. In some implementations, the controller 120 can also be configured to open the damper 115 during periods when the exhaust fan 110 is operating.

In some implementations, a user of the ventilation system 100 may enter the desired continuous ventilation requirement, for example 30 CFM, into the controller 120. The controller 120 may also be provided with a measured exhaust fan ventilation flow rate and the central fan supply flow rate in CFM. The controller 120 may then monitor the central fan 105, tracking the amount of fresh air supplied to the home as a result of heating and/or cooling operations. The controller 120 may also track the amount of fresh air supplied as a result of manual operation of the exhaust fan 110 (e.g., when a user is using the bathroom). If the desired amount of ventilation in a given time period (e.g., one hour) was not reached from heating and cooling and the manual exhaust fan operation, the controller 120 may calculate, based on for example, the provided flow rates for the central and exhaust fans, an amount of additional ventilation still required to be made up by the exhaust fan 110. The controller 120 then operates the exhaust fan 110 for an additional period of time to achieve the additional amount of ventilation.

In one example, the central fan 105 brings in or circulates 120 CFM of fresh air and the bathroom ventilation fan 110 exhausts or expels 90 CFM of air. If the desired ventilation rate is 30 CFM, the controller 120 may calculate the additional ventilation needed as follows. In this example, the hourly requirements are 30 CFM×60 Minutes/hr=1,800 Cubic Feet/hr. If the central fan runs for 10 minutes in a given hour, 120 CFM×10 Min=1,200 CF of fresh air is brought in therefore leaving an additional 600 CF to bring in. In this example, 600 CF/90 CFM=6.7 minutes of additional ventilation operation of the exhaust fan 110 is needed either at the end of the hour or within the hour to meet the 1,800 CF/hr requirement.

During long heating and cooling runs, the controller 120 may close the damper 115 to restrict the amount of fresh air to a predetermined amount, thus preventing over ventilation. In some implementations, during periods of little or no heating or cooling, the controller 120 provides the required ventilation by operating the exhaust fan 110, while also opening the motorized damper 115 in the fresh air duct to the air handler to provide pressure relief.

In a case where the central fan 105 comes on at the end of the hour (or another predetermined period) while the exhaust fan 110 is running, the controller 120 may track the additional flow and subtract the additional amount from the following hour or period, thus preventing over-ventilation. In another example, if the ventilation fan is operated for an excess amount of time (e.g., because of a long occupancy of the bathroom), the resulting excess ventilation amount may be subtracted from the desired ventilation in a following time period.

FIG. 2 is a flowchart 200 of an example process for operating a ventilation system. In some implementations, the process represented by the flowchart 200 can be implemented in the ventilation system 100 described with reference to FIG. 1. Operations of the process can include circulating air, using a central fan, for heating or cooling at least a portion of a building (202). Operations of the process also include exhausting air from the building using at least one exhaust fan that is automatically operated during time periods when the central fan is not switched on (204). The automatic operation of the exhaust fan(s) with respect to the central fan can be controlled by a controller such as the controller 120 described with reference to FIG. 1. Operations of the process further include automatically opening a damper during at least a portion of the time periods (206). The damper is opened such that fresh air enters the building through the damper.

FIG. 3 is a flowchart 300 of an example process for operating a ventilation system. In some implementations, the process represented by the flowchart 300 can be implemented in the ventilation system 100 described with reference to FIG. 1. Operations of the process include drawing in air, using a central fan, for heating or cooling at least a portion of a building (302). The central fan can be switched on during periods when a heating or cooling system is supplying hot or cold air to the building. Operations of the process also include expelling air from the building using at least one exhaust fan such that a predetermined amount of ventilation is achieved (304).

FIG. 4 is a schematic diagram of a computer system 400 that can be used to implement the controller described in association with any of the computer-implemented methods described herein, according to one embodiment. The system 400 includes a processor 410, a memory 420, a storage device 430, and an input/output device 440. Each of the components 410, 420, 430, and 440 are interconnected using a system bus 450. The processor 410 is capable of processing instructions for execution within the system 400. In one embodiment, the processor 410 is a single-threaded processor.

In another embodiment, the processor 410 is a multi-threaded processor. The processor 410 is capable of processing instructions stored in the memory 420 or on the storage device 430 to display graphical information for a user interface on the input/output device 440. In some implementations, the processor 410 can be substantially similar to the controller 125 described above with reference to FIG. 10.

The memory 420 stores information within the system 400. In some embodiments, the memory 420 is a computer-readable storage medium. The memory 420 can include volatile memory and/or non-volatile memory.

The storage device 430 is capable of providing mass storage for the system 400. In general, the storage device 430 can include any non-transitory tangible media configured to store computer readable instructions. In one embodiment, the storage device 430 is a computer-readable medium. In various different embodiments, the storage device 430 may be a floppy disk device, a hard disk device, an optical disk device, or a tape device.

The input/output device 440 provides input/output operations for the system 400. In some embodiments, the input/output device 440 includes a keyboard and/or pointing device. In some embodiments, the input/output device 440 includes a display unit for displaying graphical user interfaces.

The features described in this application can be implemented in digital electronic circuitry, or in computer hardware, firmware, or in combinations of them. The features can be implemented in a computer program product tangibly embodied in an information carrier, e.g., in a machine-readable storage device, for execution by a programmable processor; and features can be performed by a programmable processor executing a program of instructions to perform functions of the described embodiments by operating on input data and generating output. The described features can be implemented in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program includes a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

Generally, a computer will also include, or be operatively coupled to communicate with, one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. Alternatively, the computer can have no keyboard, mouse, or monitor attached and can be controlled remotely by another computer.

The features can be implemented in a computer system that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination of them. The components of the system can be connected by any form or medium of digital data communication such as a communication network. Examples of communication networks include, e.g., a LAN, a WAN, and the computers and networks forming the Internet.

The computer system can include clients and servers. A client and server are generally remote from each other and typically interact through a network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

The processor 410 carries out instructions related to a computer program. The processor 410 can include hardware such as logic gates, adders, multipliers and counters. The processor 410 can further include a separate arithmetic logic unit (ALU) that performs arithmetic and logical operations.

Other embodiments not explicitly described herein are also within the spirit of the invention and the scope of the claims. It will be understood by those skilled in the art that various changes in form and details may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the claims. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described specifically herein.

Claims

1. A method for ventilating a building, the method comprising:

drawing in air, using a central fan, for heating or cooling at least a portion of the building;

exhausting air from the building using at least one exhaust fan, wherein the exhaust fan is automatically operated during time periods when the central fan is not switched on; and

during at least a portion of the time periods, automatically opening a damper, such that fresh air enters the building through the damper.

2. The method of claim 1, further comprising:

receiving control signals from a controller at the central fan, the at least one exhaust fan and the damper; and

operating the central fan, the at least one exhaust fan, and the damper in accordance with the control signals.

3. The method of claim 2, further comprising switching on the central fan in accordance with one of the control signals when a heating or cooling system is operating to heat or cool the portion of the building.

4. The method of claim 2, further comprising switching on the exhaust fan in accordance with one of the control signals responsive to a manual input.

5. The method of claim 4, further comprising switching off the exhaust fan after a predetermined time period.

6. The method of claim 1, further comprising automatically opening the damper during a time period when the central fan is switched on.

7. The method of claim 1, wherein the exhaust fan is a bathroom exhaust fan.

8. The method of claim 1, wherein the exhaust fan is a kitchen exhaust fan.

9. A controller for controlling the ventilation of a building in which there is a central fan configured to draw in air for heating or cooling at least a portion of the building, at least one exhaust fan adapted to exhaust air from the building, and a damper that, when opened, permits fresh air to enter the building, the controller comprising:

a control logic adapted to generate signals to automatically operate the exhaust fan to exhaust air from the building during time periods when the central fan is not switched on and to open the damper during at least a portion of the time periods, such that fresh air enters the building through the damper.

10. The controller of claim 9, wherein the controller is further adapted to generate signals to switch on the central fan in accordance with an operation of a heating or cooling system.

11. The controller of claim 9, wherein the controller is adapted to generate signals to switch on the exhaust fan responsive to a manual input.

12. The controller of claim 11, wherein the controller is adapted to generate signals to switch off the exhaust fan after a pre-determined time period.

13. The controller of claim 9, wherein the controller is adapted to generate signals to open the damper during a time period when the central fan is switched on.

14. The controller of claim 9, wherein the exhaust fan is a bathroom exhaust fan.

15. The controller of claim 9, wherein the exhaust fan is a kitchen exhaust fan.

16. A method for ventilating a building, the method comprising:

drawing in air, using a central fan, for heating or cooling at least a portion of the building, wherein the central fan is automatically switched on during periods when a heating or cooling system is supplying hot or cold air to the building; and

expelling air from the building using at least one exhaust fan, wherein the exhaust fan is configured to be operated during periods in which the central fan is not operational, such that the total amount of ventilation of the building resulting from the operation of the central fan and the exhaust fan is controlled to approximate a predetermined amount.

17. The method of claim 16, wherein the at least one exhaust fan is configured to be operated for a first time period responsive to a manual input and automatically for a second additional time period on determining that the exhaust fan is to be operated for the second additional time period to achieve the approximate predetermined amount of ventilation.

18. The method of claim 17, wherein automatically operating the exhaust fan comprises operating the exhaust fan during periods when the central fan is not switched on.

19. The method of claim 17, further comprising automatically opening a damper that permits the inflow of fresh air into the building during the first time period or the second additional time period.

20. The method of claim 16, wherein the exhaust fan is part of a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV).

21. A controller for controlling the ventilation of a building having a central fan for distributing air in

a heating or cooling system and at least one exhaust fan, the controller comprising:

a control logic adapted to generate signals to operate the at least one exhaust fan during periods when the central fan is not operational, so that the total amount of ventilation of the building resulting from the operation of the central fan and the exhaust fan is controlled to approximate a predetermined amount.

22. The controller of claim 21, wherein the controller is further adapted to automatically open a damper during at least a portion of time periods when the exhaust fan is switched on, such that fresh air enters the building through the damper.