Patent Application
20180252421
The present invention relates to Heating, Ventilation and Air Conditioning (HVAC) technologies. In particular, the present invention relates to a method of reducing the phenomenon known as the ‘stack effect’ in a house with or without a combustion appliance.
Often, a wood stove or the like having a chimney stack is installed in a dwelling as an auxiliary source of heat. A common frustration with such devices is that the fuel does not always burn to complete combustion. As a result of the stack effect, the house may experience air being drawn out by outside wind forces causing the flames in the wood stove to not burn the fuel to complete combustion. Accordingly, this impedes air flow into the wood stove, and subsequently, impacts the efficiency of combustion of the fuel.
Stack effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers, resulting from air buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the “chimney effect”, and it helps drive natural ventilation and infiltration.
Since buildings are not totally sealed (at the very minimum, there is always a ground level entrance), the stack effect will cause air infiltration. During the heating season, the warmer indoor air rises up through the building and escapes at the top either through open windows, ventilation openings, or unintentional holes in ceilings, like ceiling fans and recessed lights. The rising warm air reduces the pressure in the base of the building, drawing cold air in through either open doors, windows, or other openings and leakage. During the cooling season, the stack effect is reversed, but is typically weaker due to lower temperature differences.
Generally, a house is heated in cold climates by way of a furnace, a wood burning stove, or the like, in which a combustible product, such as, for example, natural gas, oil or wood/coal is combusted in a combustion chamber and the heat produced is moved throughout the house in a number of different ways. The combustion byproducts escape from the combustion chamber and outside of the home by way of an exhaust pipe connected to a flue or a chimney or the like.
The tendency of the warmer house air to rise results in air pressure differences at various levels in the house. The stack effect in a house can make a considerable difference in the venting and performance of combustion appliances, such as a furnace or water heater.
Prior art methods and devices have been developed to address this issue.
U.S. Pat. No. 4,633,768, issued Jan. 6, 1987 (Benson) discloses a device that comprises a supplemental ventilation apparatus. In one of the embodiments, the invention discloses the ventilation system for a gas burner furnace comprising the conventional central flue for combustion gases release and an inlet air tube which introduces outside air into the furnace.
Canadian Patent No. 1,175,721, issued Oct. 10, 1984 (Newell) discloses a method for increasing the efficiency of a heating system that comprises a furnace, an exhaust pipe to remove the combustion gases extending from the combustion chamber of the furnace to the exterior of the building and an auxiliary duct intersecting the exhaust pipe to permit air to flow from the interior of the building to the exhaust pipe. The flow through the auxiliary duct is controlled in part by a damper and additionally, shut-off valves.
U.S. Pat. No. 4,920,866, issued May 1, 1990 (Hoban) discloses an improved combustion arrangement meant to prevent the back draft in a flue due to the negative pressure in the house. The invention deals with the back draft by adding an additional duct connected to the flue through a nozzle arranged to inject air into the flue in forward direction. Before being injected into the flue, the air is heated and then forced into the flue by a fan.
Canadian Patent No. 681,043, issued Feb. 25, 1964 (Field) discloses a furnace system utilizing separate flue pipes for introducing combustion air and exhausting smoke at the exterior of a building. Field also discloses a cap structure for used at the exterior ends of the flue pipes.
U.S. Pat. No. 4,262,608, issued Apr. 21, 1981 (Jackson) discloses an assembly of powered exhaust flue and preheated combustion air supply for use in association with a heating furnace so that the flue gases are exhausted to the outside while a balanced combustion air supply is pulled inside. The exhaust pipe is concentrically positioned within the outside air intake pipe. Both the exhaust and the air intake pipes are controlled by dampers. The flow of exhaust gases and fresh intake air is controlled by means of fans installed inside the two pipes.
Canadian Patent Application No. 2,708,756, published Jun. 30, 2010 (Melanson) discloses a method for equalizing air pressures within a house, the method comprising the steps of affixing an auxiliary air supply means to an existing exhaust stack of an existing combustion device located in an area with an air pressure that is lower than an atmospheric air pressure and supplying the auxiliary air supply means with air via an aperture located in an area with an air pressure that is equal or higher than the atmospheric air pressure.
The present invention provides a method of reducing the effects of the stack effect in a house with or without a combustion appliance. The present invention also provides kit to perform the method.
As an aspect of the present invention, there is provided a method for reducing the effects of the stack effect in a house without a combustion appliance, the house having an attic space and a lower portion, the method comprising the steps of: creating a substantially air tight space in the lower portion of the house by sealing at least one of cracks, leaks and openings in the lower portion of house; improving airflow in the attic space of the house by at least one of installing soffits around the roof line, increasing a total number of soffits, and cleaning/clearing debris blocking airflow through pre-existing soffits; and creating at least one airflow path, direct or indirect, from the lower portion of the house to the attic space.
As another aspect of the present invention, there is provided a method for reducing the effects of the stack effect in a house with a combustion appliance, the house having an attic space, a lower portion, and a chimney stack, the method comprising the steps of: creating a substantially air tight space in the lower portion of the house by sealing at least one of cracks, leaks and openings in the lower portion of house; improving airflow in the attic space of the house by at least one of installing soffits around the roof line, increasing a total number of soffits, and cleaning/clearing debris blocking airflow through pre-existing soffits; creating at least one airflow path, direct or indirect, from the lower portion of the house to the attic space; and creating a combustion airflow path between the chimney stack and the attic space.
Embodiments of the present invention will be further described, by way of example, with reference to the accompanying drawings, in which:
A better understanding of the present invention and its objects and advantages will become apparent to those skilled in this art from the following detailed description, wherein there is described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated for carrying out the invention.
An aspect of the present invention is purposed to reduce or possibly eliminate the phenomenon known as the stack effect, and approach equalizing air pressure in a house or building with or without a combustion appliance.
An optional first step according to an embodiment of the invention is to attempt to make the interior of the lower portion (12) of the building an air tight space. For example, this would include sealing all cracks, leaks and/or openings (15) in the lower portion of house (12), for example, cracks in the foundation in and around the basement, floor joists, doors, windows, etc. Additionally, for further sealing of cracks and leaks and/or openings (15), weather stripping, caulking, foam insulation or the like may be applied.
According to another embodiment, a further step in the method of the present invention is to improve airflow in the attic space (11) of the house. Airflow may be improved by installing soffits (16) around the roof line, increasing the total number of soffits (16), and/or cleaning/clearing debris that may be blocking airflow through pre-existing soffits (16). Additionally, airflow may be further improved by installing at least one roof vent (17) or replacing an existing roof vent (17) with a larger roof vent. Alternatively or in conjunction with roof vents (17), airflow may be improved by installing one or more stack vents (18) in the roof. The one or more stack vents should be fitted with a rain cap (19). Preferably, the one or more vent stacks (18) are six inches in diameter and four feet long. The number of soffits (16), roof vents (17) and/or stack vents (18) that need to be installed is dependent upon a number of factors, such as the size of the attic space (11), and can be determined when the air pressure of the attic space (11) is approaching equivalency with the external pressure.
The result of carrying out the previous steps somewhat normalizes air pressure in the attic space (11) with the external air pressure, which may typically provide a negative pressure zone in the attic space (11).
According to an embodiment, an additional step in the method of the present invention is to create at least one airflow path (20), direct or indirect, from the lower portion of the house (12) to the attic space (11). The airflow path (20) may be a hole, a vent stack, a vent or the like, that enables the air of the attic space (11) to communicate with the lower portion of the house (12). If the lower portion of the house (12) comprises multiple floors, then it is contemplated that at least one airflow path (20) could be installed between floors. The number of required airflow paths (20) will vary, and is dependent upon, inter alfa, the square footage of the building. Location of the at least one airflow path (20) within the building can be strategically selected in order to maximize efficiency of pressure equalization.
When pressure differences exist between the attic space (11) and the lower portion of the house (12), the airflow path (20) allows for an exchange of air that serves to equalize the pressures. Ultimately, the air pressure inside the house (10) will approach or equal the air pressure outside the house (10), thereby minimizing or eliminating the stack effect in a house (10) that does not have a combustion appliance installed.
According to a further embodiment, an additional step of the method includes creating a combustion airflow path (21) between the chimney stack (14) and the attic space (11). The combustion airflow path (21) may be a hole in the chimney stack (14) at a point located in the attic space (11), installing a “T” junction in the chimney stack (14) in the attic space (11), or some other method known to one skilled in the art, which allows the attic space (11) to communicate with the chimney stack (14).
Introducing the combustion airflow path (21) reduces and/or eliminates the stack effect in the house (10), and in particular, within the combustion appliance, thereby contributing to increased combustion of fuel within the combustion appliance.
A kit is also provided for performing the method as described herein. The kit may broadly comprise adequate soffits, vents, roof vents, rain caps, and/or ducts. At least some relevant construction materials as would be understood by one of skill in the art, such as tools, fasteners (nails, screws etc.), may also be included in the kit.
Another embodiment of the present invention will now be described.
Similarly, a water heater tank (2) has a cold water inlet (8), a hot water outlet (9), a gas supply line (5), an exhaust stack (6), and a secondary air flow (7). The gas supply line (5) provides fuel for the water heater tank (2), the fuel combusts and heats the water in the water tank (3), the heated water is then available to be used throughout the house. Combustion by products escapes via the exhaust stack (6).
Now referring to
The method according to the present invention provides for an auxiliary air supply located inside the house and/or outside the house to reduce the effects of the air pressure variation, i.e. the stack effect, and prevent back drafting. The method broadly comprises the steps of 1) affixing an auxiliary air supply means (24) to an existing exhaust stack (6) of an existing combustion device located in an area of lower relative air pressure (below the neutral pressure plane), 2) supplying the auxiliary air supply means with air from an aperture (25) located in an area of higher relative air pressure (above the neutral pressure plane). Since air located in a higher relative air pressure area will flow freely to an area of lower relative air pressure this will create an escape for the air in the higher relative air pressure are and balance the two different air pressures.
The method according to the present invention may further comprise the step of controlling the air flow through the auxiliary air supply by way of a damping means. This ensures that to the air can only flow out of the house in one direction and not into the house.
An embodiment of the present invention was installed and tested in a house. Two 6″ aluminum round ducts were connected to the exhaust pipes of a furnace and a water heater tank and sealed with aluminum duct tape, the two aluminum round ducts are connected together with a 6″ aluminum T round duct, the duct was then ran through the house to the uppers levels of the house and into the attic. In general, the attic of a house is vented to the outside and thus will have the same air pressure. The duct was held in place in the ceiling with a duct thimble. Temperature tests were conducted at various spots on the duct. The outside air temperature was at −15° C. At a point 18″ below the ceiling the temperature was measured to be −12° C. and at the point where the auxiliary air supply is affixed to the exhaust pipe the temperature was measure to be −0.2° C. This means that the cold air flowing down the auxiliary air supply is warmed up approximately 15° C. before it reached the connection point. This shows that air is indeed being drawn down into the lower air pressure areas and is equalizing the air pressure in the house as a result of the fresh air originating from the attic.
A kit is also provided for performing the method as described herein. The kit may broadly comprise adequate duct to reach from an existing exhaust stack to a desired area of higher air pressure, duct tape for sealing the duct, duct insulation, flexible duct, a duct thimble, a vent or a directional vent, and a damper.
Optionally the air that is flowing from the area of higher relative air pressure to the area of lower relative air pressure may be outputted into the area of lower relative air pressure. Optionally the air that is flowing from the area of higher relative air pressure to the area of lower relative air pressure may be vented outside the house via the exhaust stack (6), the chimney stack (14) or outside the house directly.
