Glass composite sheathing board

An insulating board is provided in which the capacity to absorb the moisture exemplified by wood fiber based board, cellulose fiber based board and perlite based board is coupled with the high permeability of fiberglass insulation to provide a board having a balance between the capacity to hold moisture and sufficient permeance to allow the board to give up the moisture as the board is passed through a cycle of absorption and desorption, whether it be on a daily or seasonable cycle.

FIELD OF THE INVENTION 
This invention relates to an improved insulating sheathing board primarily 
directed to residential home construction and more particularly to a 
sheathing board with improved insulating and breathability properties. 
BACKGROUND OF THE INVENTION 
As a result of steadily rising energy costs construction practices in 
residential housing have changed considerably inasmuch as residential 
dwellings are now more heavily insulated and usually contain high "R" 
value sheathing. As is well known in the industry, the "R" value of a 
material is a term used in connection with the performance of insulation 
and is determined by dividing the thickness of insulation by its thermal 
conductivity. The application of high "R" value sheathing which usually 
has low permeance has caused concern as a result of the changing moisture 
patterns that may occur in the wall. Excessive moisture in wall cavities 
can produce detrimental/destructive effects. The moisture may decrease the 
effectiveness of the cavity insulation and if a wall cavity remains wet 
for extended periods may result in the decaying and rotting of wood 
components of the wall. Under winter conditions condensation tends to 
accumulate on the insulation/sheathing or siding. The outdoor temperature 
and indoor humidity are the critical values. Indoor moisture moves toward 
the drier outdoors and will condense if the sheathing or siding are below 
the dew point temperature. This condensation may result in the buckling or 
warping of the siding or the blistering or peeling of the paint on the 
siding. Walls having higher "R" values have colder outside surfaces with 
greater condensation potential. The lower perm values of these walls also 
results in less moisture movement and consequently less opportunity for 
moisture to disipate through vapor diffusion. 
Where the source of moisture is external, rain water or surface 
condensation (dew) penetrates the siding under the influence of the wind 
and capillary action which can pull surface water on the siding exterior 
up between the horizontal laps of the siding. The moisture can then 
migrate from between the laps of the siding and the siding/building paper 
interface both towards the exterior (into the wood siding towards the 
paint/finish siding interface) when a sheathing of relatively low 
permeability is used and towards the interior (into the sheathing 
material) when a sheathing of relatively high permeability is used. 
Absorption of water into sheathing material of wood fiber based board, 
cellulose fiber based board and perlite based board not only lowers the 
"R" value but causes dimensional instability in the board as well. 
Dimensional instability in the board in turn causes the sheathing to warp, 
buckle and pull away from the nails holding it in place and in many 
instances may result in the total failure of the product. 
Condensation occurs typically at a marked change of permeance such as at 
the interface of two different materials where these materials are below 
the dew point temperature. It is not significant that the two materials 
may be both highly permeable to water vapor, only that they are each of 
differing permeability. An example of this is when a spun bound olefin 
film covers fiber glass insulation on the cold side of a wall. The film is 
"permeable" however the fiber glass insulation is more permeable and 
condensation occurs at the film/insulation interface. How much moisture 
accumulates is dependent on the potential for evaporation at that 
interface. Consequently, at cold temperatures considerable moisture may 
collect with resulting damage to components of the wall if the moisture is 
allowed to remain there for extended periods of time. A difficulty with 
sheathing such as asphalt coated wood fiber based board, cellulose fiber 
based board, and asphalt coated perlite board, is their relatively low 
permeance. While these materials have a relatively large capacitance to 
accumulate moisture their relatively low permeability prevents them from 
giving up the moisture as the wall passes through its climatic cycle 
whether it be daily or seasonal and as a result the wall never has the 
opportunity to completely dry. 
Thus, there has existed a definite need for an insulating board which in 
addition to having sufficient capacity to accumulate moisture has 
sufficiently high permeance to permit the moisture to escape the board 
under proper conditions. 
It is an object of this invention to provide a new and improved insulation 
board that will meet these needs of capacitance and high permeance and yet 
provide improved R values. 
It is another object of this invention to provide an insulating board 
having greater dimensional stability than comparable insulating boards. 
Still another object of the present invention is to provide an insulating 
board having superior flame and smoke life safety characteristics. 
Yet another object of the present invention is to provide an insulating 
board that possesses lower thermal conductivity (or higher "R"/inch) than 
previously attainable in insulation boards of comparable density. 
Additional objects and advantages of the invention will be set forth in 
part in the description, or may be evident by the practice of the 
invention. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is a composite material insulating board in which the 
capacity to absorb the moisture exemplified by wood fiber based board, 
cellulose fiber based board and perlite based board is coupled with the 
high permeability of fiberglass insulation to provide a board having a 
balance between the capacity to hold moisture and sufficient permeance to 
allow the board to give up the moisture as the board is passed through a 
cycle of absorption and desorption, whether it be on a daily or seasonable 
cycle. 
The board which has a nominal density of 10-35 pounds per cubic foot (pcf.) 
is produced from a homogeneous slurry of 0-40 percent by weight of 
perlite; 25-50 percent cellulose fiber; 5-60 percent glass fiber; 1-10 
percent binder (starch or phenolic resin) and 1-8 percent asphalt. With 
the Fourdrinier process, the product is made by mixing a homogeneous 
aqueous slurry of pourable consistency containing about 2-5 percent by 
weight solids of the constituents noted above, forming the slurry into a 
mat on the foraminous surface of the continuously moving open mesh chain 
of a Fourdrinier machine, dewatering the same and then drying the mat into 
a board form.

DETAILED DESCRIPTION OF THE INVENTION 
As noted above, insulating board in accordance with the present invention 
has not only the capacity to absorb moisture as exemplified by wood fiber 
based board, cellulose fiber based board and perlite based board but the 
high permeability of fiberglass insulation contained therein provides the 
board with the ability to give up moisture as the board is passed through 
a cycle of absorption and desorption, whether it be on a daily or 
seasonable cycle. 
The balance between the capacity to hold moisture and the ability to give 
up moisture can be varied by increasing and/or decreasing the amount of 
fiberglass and the permeance of the board relative to the amount of wood 
fiber or cellulose and the moisture capacitance of the board within the 
percentage limitations set forth. 
A glass composite board made in accordance with the present invention is 
produced by a wet slurry process and preferably the Fourdrinier process, 
the same process employed to produce perlite based sheathing board with 
glass fiber added as a partial or full replacement for the expanded 
perlite. The board is made from a homogeneous mixture containing the 
ingredients listed in Table I at the indicated rate percentage levels, 
based upon the total weight of the mixture. 
TABLE I 
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By Weight % 
Example Example 
Example 
Ingredient General 1 2 3 
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Perlite 0-40% 15% -- -- 
Cellulose 25-50% 47% 47% 29% 
Glass Fiber 
5-60% 25% 42% 60% 
Binder (Starch or 
1-10% 8% 8% 8% 
Phenolic Resin 
Asphalt 1-8% Asphalt Asphalt 
Asphalt 
Emulsion Emulsion 
Emulsion 
3% 3% 3% 
Asphalt 
Hot Melt 
2% 
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The cellulose fiber in the product is customarily provided by using either 
wood pulp or recycled newsprint fiber and the glass fiber utilized can 
either be newly produced glass fiber or preferably recycled or scrap fiber 
which may usually be obtained at a savings since such fiber would 
ordinarily be destined for a landfill. 
All of the constituents of the board with the exception of the glass fiber 
are mixed into a homogeneous aqueous slurry of pourable consistency, the 
glass fiber is added through a hydrapulper and a stock storage tank with 
agitating action. For example, the glass fiber may be added to a whirlpool 
or vortex of the fiber stock which feeds into the head box containing the 
conventional agitator and feeder. The slurry is formed into a mat on the 
continuously moving foraminous surface of the Fourdrinier, the mat is 
dewatered, and then the mat is dried into a board form. The aqueous slurry 
forming the mat has a solid consistency of about 2-8% by weight and 
preferably 3 1/2% by weight. 
Increasing the glass fiber in the formulation provides a board having 
increased permeance. 
The partial or full replacement of glass fiber for expanded perlite results 
in insulating board with improved thermal properties and equivalent 
flexural strength when compared to perlite based sheathing board. 
In Table II below are typical properties for samples produced in which 
there is no glass fiber and those produced in accordance with the 
compositions Examples 1, 2 and 3 of Table I. 
TABLE II 
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K BTUs Flex 
Btu in/hr Strength 
ft.sup.2 .degree.F. 
R/inch psi 
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Perlite Based Board 
0.4 2.5 205-210 
Example 1 0.328 3.05 210-210 
Example 2 0.305 3.28 205-210 
Example 3 0.290 3.45 205-210 
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As noted by the data above, the addition of glass the composition board not 
only improves the thermal performance of the insulating board as compared 
to the perlite based board, but also improves its "R" value while having 
minimal effect on the flexural strength of the board. The fiber glass in 
the formulation of the insulating board also greatly improves the 
dimensional stability of the board. Test data has shown that the use of 
25% glass fiber in the formulation (Example 1) improves the dimensional 
stability of the board over perlite based board not having fiber glass 
contained therein by 54%. Utilization of 42% glass fiber in the 
formulation (Example 2) increases the dimensional stability of the board 
produced over perlite based board having no glass fiber by 70%, and in the 
case of the formulation containing 60% glass fiber (Example 3) there is an 
85% improvement of dimensional stability over perlite based board not 
containing glass fiber. 
The glass composite board of the present invention, also compares very 
favorably to other sheathing materials as indicated in Table III below. 
TABLE III 
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K 
BTUs in/hr 
ft.sup.2 .degree.F. 
R/Inch 
______________________________________ 
Composite Board Example 2 
0.305 
Perlite Based Board 0.40 
Wood Fiber Based Board 
0.40 
Cellulose Fiber Based Board 
0.55 
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In addition to the other favorable properties of glass composite board, the 
Table IV shows a comparison of flame spread/smoke development life safety 
of the formulations of Examples 1, 2 and 3 for the standard asphalt coated 
wood fiber based board. 
TABLE IV 
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Flame Smoke 
______________________________________ 
Asphalt Coated Wood 
140 300 
Fiber Based Board 
Example 1 45 10 
Example 2 42 7 
Example 3 25 5 
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Listed in Table V are the Perm values of the formulations of Examples 1, 2 
and 3 and asphalt coated perlite based board with fiber based board and 
cellulose based board with a facer. Any material with a Perm value of less 
than 5 is normally classified as being impermeable. The term "perm" is a 
unit of measure in the industry in connection with the permeability of a 
material, denoting its ability to transmit water vapor. A perm is 
equivalent to the transmission of 1 grain of water vapor per hour per 
square foot of the material in question, and is measured in accordance 
with known standard procedures, set forth, for example, in ASTM E 96 WVT. 
TABLE V 
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PERM 
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Example 1 36 
Example 2 42 
Example 3 67 
Asphalt Coated Perlite 
0.05 
Based Board 
Wood Fiber Based &lt;5 
Board 
Cellulose Fiber Based 
&gt;5 
Board with Facer 
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In Table VI below there is illustrated the moisture storage capacitance of 
Examples 1, 2 and 3 formulations. 
TABLE VI 
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Moisture Storage Capacitance where relative humidity is 
______________________________________ 
100% 
Examples 1 and 2 
1.55 lbs. water vapor per cu. ft. 
Example 3 .825 lbs. water vapor per cu. ft. 
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While in the illustrations above the use of the glass composite board is 
directed to use as sheathing, obviously this board in view of its inherent 
properties can be used for various other purposes.