Ventilation – Having both inlet and outlet airways – Natural ventilation including air passage through rooftop
Reexamination Certificate
2000-05-04
2002-12-10
Joyce, Harold (Department: 3749)
Ventilation
Having both inlet and outlet airways
Natural ventilation including air passage through rooftop
C052S198000, C052S199000, C454S339000, C454S366000, C454S367000
Reexamination Certificate
active
06491579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to roof vents, and more specifically to passive attic vents for use with tile roofs.
2. Description of the Prior Art
Energy efficiency is a serious consideration in building design and construction. Many building codes require builders to minimize energy requirements to maintain comfortable living spaces. One of the most common energy losses in a home is due to heat transfer through the attic. In warm climates, heat builds up in the attic from solar energy incident on the roof or from heat transfer up from the living space. If the attic is allowed to become too hot, the installed insulation becomes ineffective and the attic heat is transferred to the living space below. In colder climates, moisture builds up in the attic, robbing the insulation of much of its R value. Consequently valuable heat in the living space is conducted out through the attic.
Early efforts at minimizing energy losses through the attic focused on the insulation between the living space and the attic and ignored the effects of the heat and/or moisture build-up. As insulation improved a point was reached where more insulation was not necessarily better or possible due to space limitations. Gable vents and dormer type passive ventilation systems have been incorporated to ventilate the attic. These ventilation devices conduct excess heat and or moisture out or the attic thus maintaining the efficiency of the installed insulation. However, both gable and dormer ventilation systems are clearly visible and often require extensive architectural manipulation to minimize their esthetic effect on the structure.
In geographical areas that are typically warm and dry such as the American Southwest, many homes have low pitch, hip roofs which have no gables, and dormers may have a significantly effect the aesthetics of a design if improperly located or too numerous. Therefore, these systems have proven to be inadequate. In colder and or wetter climates such as the Eastern United States, snow buildup, or driven snow or rain counteract the conventional passive ventilation devices and usually block the vents and or reintroduce more moisture than was originally present thus minimizing the benefit of the vents.
Passive attic vents which attempted to camouflage their appearance have been marketed in recent years. These camouflaged vents are generally a closed device made for direct conduction of air from the attic or waste vents and are often made of plastic or other material amenable to mold manufacturing. The direct conduction or one-piece construction may limit air flow and may provide a direct path for moisture such as driven rain or snow into the attic thus minimizing the benefit of the vent. To improve the conventional ventilation technology it is necessary to understand clay or concrete roof construction.
A roof is designed to shed rain and snow and shield the living space from sun. A roof is composed of structural elements to support its weight and form a slope to assist in shedding rain and snow.
The first structural element is the roof rafter
8
or truss which creates the basic slope of the roof as shown in
FIGS. 7 and 8
. Secured on top of the rafters or trusses, such as rafter
8
, is a layer of wood
6
, such as planks, plywood or oriented strand board (OSB). Nailing plywood
6
to the roof rafters forms a sloped diaphragm or structural layer D.
Structural layer D forms a very strong structural element and is likely to leak only along the seams between sheets of plywood
6
if left as the complete roof. However, wood requires frequent attention and treatment to retain its weather resistance, and thus is not a good long term roof material.
Plywood
6
is usually covered with lapped layers of roofing felt
4
or paper or other suitable material which is treated with tar and or other chemicals to render it water resistant. The lapped layers of felt
4
may become sealed together by the heat on the roof and form a true water proof membrane or layer and could be used for a roof topping. However conventional roof felt or paper such as felt
4
is fairly fragile and susceptible to damage from sun or wind. If left unshielded in the sun it would dry and crack in a short time and thus is inadequate as a lone weatherproofing material.
By covering felt
4
with a layer of material resistant to sun and other weather effects, felt
4
may be protected from direct solar radiation and may produce a weather-tight roof. Layer
2
may be composed of asphalt shingles, wood shingles, clay tiles, concrete tiles, metal tiles or similar conventional materials. In this example, layer
2
is composed of interleaved clay tiles such as cap tiles
2
C and pan tiles
2
P. Battens, such as batten B, may be used as securing sites for metal, clay or concrete tile roofs.
Layer
2
sheds the majority of rain and snow and is generally impervious to long term weather effects. Layer
2
does have many small openings and spaces between the tiles or other elements, thus felt
4
remains as the waterproof layer and sheds any water or snow which passes through layer
2
.
Referring now to
FIG. 8
, conventional camouflaged vents, such as vent
7
, provide a direct and closed conduction path P for attic air or waste vent air. In a passive ventilation system, the volume of air conducted via path P is limited by the cross sections at opening O and inlet I and the temperature differential between the air AI in the attic and air AO outside the attic. To permit adequate attic ventilation, many conventional vents, such as vent
7
, will be needed. Due to the directness of path P, wind driven rain or snow may be blown into opening O and travel directly into the underlying attic space bypassing tile layer
2
and water proof felt layer
4
.
Due to the complex shapes required, conventional camouflaged vents, such as vent
7
are often fabricated from moldable materials such as plastics. Plastic permits a vent to survive moisture yet may not be as durable as conventional roofing materials due to the effects of solar radiation and/or airborne chemicals.
What is needed is a new roof system incorporating an improved passive ventilation system that can be simply manufactured from highly durable material and will not affect the appearance of a building design if used in adequate numbers to properly ventilate the attic and or rafter spaces, and is useable on many roof configurations and with many types of conventional roofing materials.
SUMMARY OF THE INVENTION
The present invention provides a new roofing system that incorporates an open attic or rafter space ventilation technique. The new roofing system includes solid conventional roofing materials such as clay or concrete tiles combined with two or more primary vents conducting air through the structural layer and the water resistant membrane.
Thus, in a first aspect, the present invention provides a ventilated roof comprising a roof structural layer through which air is to be ventilated; a primary vent disposed in the structural layer to provide an air flow passage therethrough having a first venting performance; a plurality of tiles mounted on the structural layer to form a tile layer thereover and arranged to provide air flow passages between adjacent tiles having a combined second venting performance; and a secondary vent disposed in the tile layer to form an outer roofing layer therewith and having an air passage therethrough with a third venting performance smaller than the first venting performance, the outer roofing layer being in air flow communication with the primary vent to provide a venting air flow passage for venting said air.
In another aspect, the present invention provides a method for ventilating a roof comprising the steps of providing a roof structural layer through which air is to be ventilated; selecting a primary vent having a first venting performance; mounting the primary vent in the structural layer to provide an air flow passage therethrough; selecting a plurality of tiles; arranging the tiles on the structural la
Joyce Harold
Knobbe Martens Olson & Bear LLP
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