Patent Application
20200109870
The invention relates to an article and method for ventilating contaminants from a building.
Ventilation systems can be used to reduce humidity, toxins, radioactive gases, pollutants, allergens and other unwanted chemicals (collectively “contaminants”) from buildings. Such systems can produce either a positive or negative pressure gradient between the building and the exterior that forces contaminants from the building and replaces the contaminants with fresh air.
More generally, ventilation systems have included exhaust systems, supply systems, balanced systems, and energy recovery systems. These systems can include one or more fans, vents, or ducts. They typically operate continuously; however, they can be triggered by an event such as a timer or high humidity level.
An exhaust system includes an exhaust fan that draws air from the building. Outside air can infiltrate through cracks, windows, etc. to replace the exhausted air. A downside of exhaust systems is the incoming outside air can draw in contaminants, such as toxins, allergens, and humidity, and outside air may exhibit temperatures that are excessively hot or cold, or humidity which is excessively moist or dry. Any of these states may be detrimental to the structure or the health of the inhabitants thereof. Humidity can even condense inside the walls of the building thereby promoting mold and mildew growth.
Supply systems produce a positive pressure inside the building that forces out interior air. Outside air is drawn into the building though a duct, and replaces the interior air forced from the building. Unlike exhaust systems, supply systems permit the incoming air to be filtered, thereby reducing particulate contaminants. Supply systems do not typically remove gaseous contaminants or particulates too small for the filter. Because supply systems also do not remove moisture or adjust the temperature of the incoming air, they are limited to drier and warmer climates.
A balanced system can contain a plurality of fans that move air into and out of a building. A first fan draws a volume of outside air into the building through a first vent so the incoming outside air can be filtered. A second fan exhausts a similar volume of interior air from the building through a second vent. The need for a plurality of fans and vents makes a balanced system costlier than either an exhaust or supply system. Like exhaust and supply systems, however, balanced systems cannot remove gaseous contaminants, small particulates, and do not affect humidity or temperature of the incoming or exhausted air.
Energy recovery systems permit exchange of both air and heat. Like a balanced system, an energy recovery system includes a plurality of fans and vents for transferring air between a building and the outside. Energy recovery systems also include a heat exchanger that transfers heat between the incoming and outgoing air, thereby reducing heating and cooling costs. The transfer of heat can also stabilize humidity levels in the building as warmer air absorbs moisture from cooler air. Of course, an energy recovery system is typically more expensive to purchase and install than other types of systems. Further, energy recovery systems do not eliminate gaseous contaminants or small particulates.
The energy efficiency of modern buildings restricts air infiltration. Humidity trapped in the building can cause mold, mildew, and decay. A solution in the prior art includes an exhaust fan triggered by a humidity sensor, whereby humid air in a crawl space is replaced by outside air. This solution fails when the outside air is more humid than the air within the crawl space. This can produce a runaway state, that is, a feedback loop that causes the exhaust fan to run continuously as the humidity within the crawl space increases. The ventilation system can reduce the effectiveness of heating systems and other energy conservation measures, such as insulation and double pane windows, because the ventilation system can draw in large amounts of cold air.
A need exists for a ventilation system that operates as needed to remove contaminates from a building without drawing in even more contaminates or reducing the effectiveness of heating and cooling systems. Current ventilation systems can result in more contaminates and cold, humid air being drawn into a building. A ventilation system should be able to monitor both interior and exterior air quality and then move air either into or out of a building as needed to reduce interior contaminants.
The invention describes a building ventilation system comprising at least one fan, at least one duct or vent, at least one sensor, and at least one controller. The fan can be reversible and can be of any appropriate size, voltage, and air flow. In embodiments, a plurality of fans can be used, including for example at least one intake fan for intake air and at least one exhaust fan for exhaust air. Ducts and vents can comprise, for example, metal or plastic pipes with or without check valves. The ventilation system can optionally include shutters to close the ducts or vents, thereby restricting airflow. In embodiments, the fan can be integrated into a duct or vent.
The sensor can detect contaminants including, but not limited to, humidity, radon, temperature, allergens, and pollutants such as carbon dioxide, carbon monoxide, or hydrocarbons. Optionally, the ventilation system includes redundant sensors to ensure reliable operation in case of failure of the primary sensor. The sensor provides sensor inputs to the controller. Sensor inputs can include interior sensor inputs and exterior sensor inputs. In embodiments, the ventilation system includes a plurality of sensors, including an interior sensor and an exterior sensor. Generally, an interior sensor provides sensor input from the side of the fan opposite the air flow, that is, the interior air input, and the exterior sensor provides sensor input from the incoming side of the air flow, that is, the exterior air input.
The controller comprises circuitry capable of receiving the sensor inputs and operating the fan when the inputs exceed a differential. Conveniently, the controller is a programmable microprocessor and can include various peripherals, memory, communications media, a logging device, and combinations thereof. The controller can trigger the fan and direct airflow into or out of the building. The ventilation system can be used for an entire building but also in specific applications including, but not limited to, attics, crawlspaces, and garages.
In an embodiment, the ventilation system can be used in building having raised floors and crawl spaces. For example, raised floors mitigate the heaving and shrinking of bentonite clays on which many buildings are constructed. Heaving and shrinkage can damage concrete slabs, load bearing beams, walls, etc. The raised floor increases costs and produces an enclosed volume that can accelerate decay of construction materials, growth of fungus and mildew, and accumulation of radioactive radon gas.
In embodiments, the interior sensor samples interior air within the building and the exterior sensor samples exterior air outside of the building. Preferably, the sensors are placed at sample locations of interest. For example, the interior sensor can be placed in a crawl space or attic where air quality might be problematic. The sensors send inputs descriptive of the interior and exterior air to the controller. The controller receives the inputs and, based on the inputs, and algorithm setpoints, determines whether air exchange is necessary. The controller may turn the fan on, change the speed of the fan, or even reverse the direction of airflow. Unlike prior art, the controller would not trigger airflow based solely on an interior sensor, thereby reducing the risk of a feedback event that would cause the fan to run continuously and impair energy efficiency of the building. In alternative embodiments, the controller can assist in heating or cooling the building by moving air to take advantage of thermal gradients between interior and exterior air. For example, an attic heated during the day can be actively cooled by drawing in cool night air, or merely ventilated during extreme heat.
In an alternative embodiment, a sensor of the ventilation system can detect a pollutant, such as for example, carbon monoxide. This could be used, for example, in homes and especially garages. If the sensor input exceeds a safe level, the controller could direct the fan to exhaust interior air, thereby reducing the level of pollutant. In embodiments, the controller could also trigger an alarm to warn residents of excessive levels of pollutant. The alarm could be audible, visual, and even electronic such as sending a text or email message to a designated person, or monitoring service.
In embodiments, a plurality of sensors integrates with the primary airflow of the fan. For example, humidity, temperature and carbon monoxide sensors can be in close proximity on or near the fan, thereby reducing the mass of wires. The controller can receive inputs from the various sensors and based on its programming operate the fan as needed.
The fan can be either AC or DC; however, DC operation reduces wear parts, can operate with low power switched transistors, are reversible, throttleable, and can provide tachometer feedback to the controller. Further, DC operation can reduce noise and vibration by controlling the RPM of the fan blades. The controller can be programmed to adjust fan speed for reduced noise and vibration. Alternatively, an accelerometer sensor near the fan can provide input to the controller, which can adjust fan speed automatically.
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The controller can comprise a programmable microprocessor that would allow updates to its internal software. The controller can be connected wirelessly, for example, Wi-Fi or Bluetooth, so that data can be downloaded and uploaded. Users may interact with the controller using an app or website address. Advantageously, software that operates the controller can be improved using uploaded date and the improved software can be downloaded into existing ventilation systems.
The controller can also be programmed to improve power characteristics of the fan. Such characteristic can include, for example, current, voltage, or their product. One or more audio, vibration, or accelerometer sensor inputs may be employed to acquire the acoustic signature of the fan operating at an improved power setting.
Typically, the acoustic signature of the fan at its quietest or lowest vibration coincides with the preferred power setting, that is, the preferred RPM setting for the fan. The quietest setting can be the power setting having the lowest decibel reading. Preferably, the controller is biased in favor of quieter operation at the expense of a higher power setting.
In prior art, a single humidity sensor could cause even moister exterior air to be drawn into the building in a positive feedback loop. A first example of the present ventilation system includes a controller, a fan, an interior humidity sensor, and an exterior humidity sensor. The controller is programmed to operate the fan only when (a) the interior of the building exceeds a preset humidity and (b) the exterior humidity is lower than the interior by a preset differential. This avoids running the fan when air exchange will produce no benefit and also reduces energy loss.
A ventilation system comprises a fan, a switch, a reversible fan, an interior humidity sensor, an interior temperature sensor, an exterior humidity sensor, and an exterior temperature sensor. See
What is believed to be the best mode of the invention has been described above. However, it will be apparent to those skilled in the art that numerous variations of the type described could be made to the present invention without departing from the spirit of the invention. The scope of the present invention is defined by the broad general meaning of the terms in which the claims are expressed.
This application claims priority to U.S. provisional application 62/742,564 filed 8 Oct. 2018.
| Number | Date | Country | |
|---|---|---|---|
| 62742564 | Oct 2018 | US |
