CA1166886A

CA1166886A - Attic ventilation system

Info

Publication number: CA1166886A
Application number: CA000392110A
Authority: CA
Inventors: John R. Peirson; Deane A.L. Lynch
Original assignee: Peirson (jr) Systems Ltd
Current assignee: Peirson (jr) Systems Ltd
Priority date: 1981-12-11
Filing date: 1981-12-11
Publication date: 1984-05-08

Abstract

ABSTRACT OF THE DISCLOSURE
An attic ventilation system is provided for a building which is normally elevated above ground. The ventilation system comprises an insulated duct extending upward from building floor to building ceiling to provide air communication between the air space under the building and the building attic. Positive suction, non-powered air exhausting devices are provided on the attic roof which are adapted to exhaust air from the attic in response to wind flowing over the devices. This arrangement prevents the accumulation of snow in the attic, particularly in harsh winter environments such as the Arctic.

Description

7~8~ 6 _______________________ This invention relates to attic ventilation systems and more particularly to those which are useful in harsh winter environments, such as the Arctic.
BACKGROUND OF THE INVENTION
_____________________._____ It is common to ventilate attics in standard building construction by providing vents in the soffit area of the building. The vents permit flow of air into the attic space and out through a ventillating device in the building roof.
An example of such typical attic ventilation system is disclosed in United States patent 3,051,071. In most climates, this form of attic ventilation is quite adequate;
however, in areas of extreme cold and high winds, it has been discovered that such system presents several drawbacks. The greatest drawback is that, with higher winds, granular snow particles can be driven into the attic space through the soffit vent openings. During the colder temperatures substantial amounts of snow can be accumulated in the attic.
In the spring time with the warmer temperatures, the snow and accumulated ice is melted spoiling the insulation and, if there has been sufficient snow buildup, the ceiling of the building is weakened by the moisture and can collapse. In the event that only minimal amounts of snow have accumulated, the thawing of the snow can moisten the insulation, cause spotting of the ceiling and then render the insulation useless from an insulative value standpoint.
An approach to building construction for the Arctic is disclosed in Peirson et al, United States patent ~,19~,328.
This building construction eliminates the attic space with provisions for optimizing on the insulation and air-vapour ~ ~ 6~6 1 barrier properties of the construction. There are, however, many homes in the Arctic with attics and there remains to be a demand for one storey homes with attics, all faced with the problem of snow build up in the attic area.
The ventilation system, according to this invention, overcomes the above problems by minimizing or totally eliminating snow build up in the attic in the extreme winter climates, such as in the Arctic.
SUM_ARY OF_ THE INVENTION
Most homes built in the Arctic, where there is permafrost, have no basements so that the building floor is elevated above the ground. With such building construction where attics are provided, the ventilation system, according to this invention, ventillates the attic with air drawn from the space beneath the building and exhausted from the roof of the building. The power to exhaust air from the attic is obtained from the prevailing winds.
The ventilation system comprises an insulated duct extending upwardly from the building floor to the building ceiling to provide air communication between the air space defined beneath the building and the building attic. Each end of the duct is mounted on and sealed to the respective building floor and ceiling. Means is provided for exhausting air from the attic, the exhauster means being adapted to withdraw air from the attic in response to wind flowing over the air exhauster means. The duct and the air exhauster means provide the sole means of air communication into and out of the attic. The duct is located in the air space beneath the buildin~ floor where snow and the like from building exterior winds are prevented from entering upwardly B ~

1 into the duct to thereby avoid accumulation of snow and the like in the attic, as the air exhauster means withdrawns air from the attic. The duct is of a cross-section of sufficient area to minimize negative pressure developing in the attic for the operating range of the air exhauster means for withdrawing air from the attic.
BRIEF DESCRIPTION OF THE DRAWINGS
____________ ____________________ Preferred embodiments of the invention are shown in the drawings wherein:
Figure 1 is a perspective view of a building construction as raised above the ground and having an attic ventilation system according to this invention;
Figure 2 is a plan view of the building showing locations of the ventilation system duct and air exhauster devices for the roof;
Figure 3 is a side elevation of a building construction having the ventilation system wherein the flow of ventilating air is shown;
Figure 4 is a view of an air exhauster device; and Figure 5 is a cutaway view of a duct used in the ventilation system to provide for air communication between the air space beneath the buil~,ing and the building attic.
DETAILED DESCRIPION OF T~E PREFERRED EMBODIMENTS
___________________ ___ ______ ____ __________ An example of a building construction with attic is shown in Figure 1. The building 10 is raised above the ground with the use of structural supports 12 to define an air space generally designated 14 beneath the building floor 16. The building is of a standard rectangular design with endwalls 18 and sidewalls 20. The roof design for the building is a standard gable design having gable ends 22 and 8 ~ 6 1 sloped portions 24 and 26. Within the gable roof above the ceiling 28 is the standard attic space. It is important to ventilate the attic because moisture within the building permeates through air-vapour barriers into the attic and can condense and form frost in the attic. This can prove to be harmful, particularly to the insulation if not removed. The ventilation system, according to this invention, provides a totally sealed attic space except for a duct 30, which provides communication between the space 14 beneath the building and the attic space generally designated 32 and the exhauster devices generally designated 34 which withdraw moisture laden air from the attic 32.
Referring to Figure 2, desired locations for the duct 30 and the air exhausters in the roof are shown. The rectangular outline of the floor is shown at 36. Tha peak of the roof is shown by line 38. The floor area has been divided into thirds where, in the length dimension, each third is represented by line 40 and in the width dimension, each third is represented by line 42. The intersection of the lines divides the floor into thirds to define a central region 44 as shown in the shaded area. The duct 30 may be located anywhere in the central region 44 because such positioning ensures that any snow which may be blown underneath the building into the space 14 has been deposited about the periphery of the building away from the central area 44O Thus locating the opening of the bottom end of the duct 30 in this central area 44 ensures that snow does not block the duct.
To optimize on air circulation in the attic, the exhauster units 34 are spaced apart and located to each side 8 ~ ~

1 of the duct 30. As shown, the space be~ween the exhauster unit 34 is represented by arrow 46. The exhaust unit 34 is spaced from the end 48 of the building by a distance 50 which is equal to one half the dimension represented by line 46.
The exhaust unit 34, as located in the roof, is o~fset slightly from the peak, as represented by line 38 to ensure location of flashing and sealing engagement with the roof.
This locating of the exhaust units optimizes on the air flow, as shown in Figure 3, where air enters the attic from duct 30 and disperses in the direction of arrows 52 and 54 and swirls around in the direction of arrows 56 and 58 before being exhausted in the direction of arrows 60 and 62.
Building floor 16 may be elevated above the frozen ground 64 by approximately one to two feet as determined by the height of the structural supports 12, which is the standard construction technique in the Arctic or in other cold areas where there is permafrost in the ground 64. As the exhausters 34 withdraw air from the attic space 32, air is replenished in the attic by way of the duct 30 drawing air from the space 14, as shown by arrow 66. As previously explained, the location of the duct 30 is such that snow from driving winds does not collect around the base of the duct, because of its central location beneath the floor 16.
Further details of the air exhauster unit 34 are shown in Figure 4. The exhauster unit has a stack portion 70 which extends upwardly between the roof rafters 72. ~o mount the exhauster to the roof rafters, a roof support tnot shown) is provided and the stack 70 secured to the support. Roof flashing 74 and storm collar 76 are sealingly engaged with the stack 70 and the roofing covering sealingly engaged with 1 the flashing 74. Mounted on the top of the stack 70 is the exhauster unit 34. As can be appreciated in the northern colder climates, it is most advantageous to use an exhauster device which does not employ any moving parts, nor require a power source which consumes energy such as a motoL driven fan. The exhauster device shown has a plurality of vanes 78 which are shaped and positioned such that the prevailing wind, as represented by arrow 80, may be directed on the exhauster from any direction and still cause the unit to withdraw air from the attic in the direction of arrows 82.
Such exhauster units may be purchased from various companies, an example of which is the system sold by the G.C. Breidert ~ompany of Pacoima, California and sold under the trademark "Air-X-Hausters".
It has been determined that the air exhauster unit can withdraw approximately 200 cubic feet per minute of air from an attic with a ten mile per hour pr0vailing wind. At a fifty mile per hour prevailing wind, the exhauster unit can withdraw approximately 5~0 cubic feet per minute. To avoid the development of negative pressures within the attic, the duct 30 has sufficient cross-sectional area to keep the pressure in the attic as close to ~ero pounds per square inch gauge as possible. For a duct of approximately 6 inches by twelve inches in width and a height from floor to ceiling of approximately twelve feet, a ten mile per hour wind, developes an insignificant negative pressure in the attic of approximately .006 inches of water gauge. This negative pressure has little if any effect on heating of the building interior, or causing any air or moisture to flow through the vapour barrier into the attic. With a fifty mile an hour 1 3 6~8~

1 wind, there is a negligable change in the negative pressure to approximately .039 inches water gauge. Therefore, the cross-sectional surface area of the duct 30 is chosen to minimi~e to an insignficant value the negative pressure developed in the attic.
Turning to Figure 5, a preferred assembly Eor the duct, which feeds air to the attic from the space beneath the building, is shown. The building floor 16 comprises floor joist, not shown, into which an upper plywood decking 84 and a lower plywood deckinq 86 are nailed The duct 30 extends downwardly through the floor 16 and finishes flush with the bottom of the floor system to provide a lower open end 88.
The lower end of the duct 30 is sealed to the lower plywood decking 86 by appropriate caulking compound to provide an airtight joint and not permit outside cold air to migrate up into the building. To prevent heat loss through the 100r, insulative batts 90 are provided between the jois~s as contained between the decking 8~, 86. To support and secure the duct 30 to the floor, a flange 92 is used which ls secured to the exterior of the duct 30 and is nailed to the floor through apertures 94.
The upper end 96 of the duct 30 similarly extends through the ceiling joist 98 to which upper ceiling material 100 is secured. On top of the ceiling material 100, insulative batts 102 are provided. The upper end 96 of the duct 30 is supported and secured relative to the joist 98 by flange 102 which is nailed to the joist through apertures 104. The upper end 96 must extend slightly above the finished level of the insulation. Again, caulking compound and the like is used to seal the upper end 96 of the duct to 1 the vapour material used in insulating the ceiling of the building.
Since the duct 30 extends upwardly through the building, it is important to insulate the duct 30 to prevent heat loss from the building into the duct. Since cold air is flowing up through the duct, any moisture in the building interior air may condense on the duct if it were not insulated and cause damage to surrounding building interior.
Also insulating the duct prevents the creation of a chimney effect because the air in the duct should not be heated by the air in the building. Preferably the duct 30 ~onsists of an inner shell 106 having insulative material 108 therearound. Over top of the insulative material 108 is an outside skin 110 which may also be of metal to resist damage and provide rigidity to the duct. The duct work may be shipped in sections, such as representative four foot sections, where mating ends are provided and interconnected by a cleat portion 112 which is adapted to form an airtight connection.
It is appreciated that the ventilation system may be installed in homes as they are being constructed.
Alternately, the system can be readily placed into an existing home in the Arctic. To ensure that the duct 30 and the exhaust 3~ are the sole means of the attic communicating with the exterior, all other vents and openings to the attic are sealed in existing homes. A duct 30 is then installed centrally of the building and may extend upwardly through a closet or the like in the building. The exhausters 34 replace other types of vent units in the roof and are positioned in accordance with the format suggested in Figure ~ ~ 8~

1 2. By the use oE air~vapour barrier and the like for new home construction, the attic can be completely sealed except for the entrance of duct 30 to the attic to provide communication with the space beneath the building and the exhauster 34.
The ventilation system, according to this invention, therefore provides ventilation for the attic while avoiding accumulation of wind driven snow in the attic. The system is inexpensive, readily installed and with appropriate exhauster units does not require maintenance.
Althou~h preferred embodiments of the invention have been described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An attic ventilation system for use in areas of extremely cold climate on a building having a building floor with a cold air space thereunder, a heated building interior, a building ceiling between the attic and the building interior and a building roof above the attic, the ventilation system comprising a duct of a length to extend from the building floor through the building interior to the building ceiling to provide air communication directly from the cold air space to the attic, the duct being sealed at the building floor and the building ceiling to substantially prevent migration of the cold air to the building interior with the duct being insulated over its entire length through the building interior to essentially eliminate heat loss from the building interior into the duct to prevent both heating of the cold air in the duct and condensation on the duct, and at least one air exhaust device adapted for mounting to the building roof for exhausting air from the attic in response to wind passing over the air exhaust device, the attic being sealed other than at the duct and the air exhaust device for essentially frost free cold air only ventilation of the attic.

2. A ventilation system of claim 17 wherein said air exhaust device has stationary vanes positioned in a manner to exhaust air from a building attic in response to wind passing over said stationary vanes.

3. A building construction as claimed in Claim 1 when elevated above ground to provide the cold air space thereunder.

4. A building construction of claim 3, wherein said building is normally elevated above ground by approximately one to two feet.

5. A building construction of claim 4, wherein said duct is located centrally of said air space relative to the building floor, said building elevation substantially preventing wind blown snow reaching under said building in the area of said centrally located duct.

6. A building construction of claim 4, wherein a single duct is located centrally of the building floor surface, two of said air exhaust means being provided on said building roof and located to each side of said duct location in said building attic.

7. A building construction as claimed in Claim 6 wherein said building has a gable roof design with a roof ridge, said air exhaust means being spaced from one another by a first distance and being located toward opposite ends of said roof and spaced therefrom by a second distance equal to about one half of said first distance, offset from the roof ridge to improve air flow out of the attic.

8. A building construction of claim 1, wherein said building floor comprises a plurality of spaced-apart joists with plywood decking on the bottom and top of the joists, the lower end of said duct being sealed to the bottom plywood decking, said building ceiling including a vapour barrier to which the upper end of said duct is sealed.

9. A building construction of claim 1, wherein said air exhauster means is designed to withdraw approximately 200 cfm from said building attic at a wind speed of approximately 10 m.p.h.

10. A building construction of claim 9, wherein said duct is of sufficient cross-sectional area to develop an insignificant negative pressure build up in said building attic space of approximately .006 inches of water gauge.