US2324971A

US2324971A - Wall

Info

Publication number: US2324971A
Application number: US317167A
Authority: US
Inventors: Hobart F Woodward
Original assignee: Minnesota and Ontario Paper Co
Current assignee: Minnesota and Ontario Paper Co
Priority date: 1940-02-03
Filing date: 1940-02-03
Publication date: 1943-07-20
Anticipated expiration: 1960-07-20

Description

H. F. WOODWARD July 20,I 1943.

WALL

Filed Feb. 5, 1940 ZJMM www1/Mm, H s, ma. 3. f J L WW y Y, mfg wm @www w w V MMV? Z y J f e f Y A p M, wm @www of.

INVENTOR ATTORNEY Patented July 20, 1943 WALL Hobart F. Woodward, Minneapolis, Minn., assignor, by mesne assignments, to Minnesota and Ontario Paper Company, a corporation of Minnesota Application February 3, 1940, Serial No. 317,167

2 Claims.

This invention relates to walls which are located where there is a temperature differential between opposite sides thereof and in which wall insulation is provided forretarding the transmission of heat through the Walls. The invention has special reference to winter insulation of buildings wherein a warm, more or less humid atmosphere normally exists on one side and where a freezing temperature may occur on the cold side.

It has been found in climates experiencing freezing weather that vapor in heated houses migrates into the walls and as it acquires a lower temperature from the outside, the vapor may condense depositing water. Theoretically condensation of vapor occurs at the dew point, and in the event the temperature is freezing, ice may form in the walls. At warmer temperatures the accumulated ice will melt. This usually results in injury and decay to wood frames and other structural parts and such injury may be'observed after a number of years of this action. Siding and sheathing in particular deteriorate, and such action appears to be hastened by conventional structures, which retard the passage of vapor and tend to prevent evaporation of water which accumulates. It has been found by experience that themigration of vaporl into a normalwall under many conditions is,

far too rapid to wall. y

There has. been much speculation about the theory relating to the migration of vapor through materials, and the application of the theory to building construction. The direction of vapor travel is Adetermined by the moisture equilibrium conditions for the two sides of the material and not the absolute vapor pressure difference. vIt may be said that in most practical cases where the vapor pressures are different on the two sides of a building wall, a vapor pressure gradient will be established through the wall, and the vapor will travel in the direction of vapor pressure drop. n

It is an object and purpose of vapor barriers to provide means which will either bar the migration of vapor into walls or so retard the migration of vapor that condensation Within the walls will not occur.

It is an object of this invention to provide a wall construction in which the warm side is of such construction as will prevent or retard to prevent condensationwithin the a great extent, the migration of vapor into the Q into the wall from the warm side will escape from the wall before condensation occurs.

Other objects of the invention are the independent or combined provisions of a heat insulated walland heat insulating material in which the cold side of the Wallis substantially not less than eight times more vapor-pervious than the warm side of the wall. f

Otherandl additional objects and advantages of the invention Will appear from the following explanation of the invention made in connection with the accompanying drawing in which:

Figure 1 is a diagrammatic representation of a wall of the open stud space type.

Figure 2 is a diagrammatic representation of a wall of the insulated stud space type.

Figure 3 is a diagrammatic representation of a wall of the so-called dry wall type.

Figure 4 is a sectional view of a wall of the type shown in Figure 1.

Figures 5, 6, and 7 are views of ber board having vapor barriers on one face thereof.

For successful construction attention must be given, to vapor barriers. In cold 'climates it is especially important to provide a vapor barrier to prevent or retard vapor from the interior of the house migrating through the inner wall panel and condensingtwithin the stud space. Vapor barriers should beappliedlon the Warm` side of` the wall (the inner panel,` In. a-construction where plaster is to be used the vapor barrier generally should be applied on the rear face of the plaster base. In a construction employing so-called dry wall the vapor ybarrier may be on either face of the inner panel, preferably on the room .side of the inner panel.

Referring to Figures 1, 2,.3and 4, it is assumed that suchwalls are employed in a house wherein the room or inside temperature is about '70 F.,

anda relative humidity of about 40%, and the outsidertemperature is about F. The inside yair will contain about 3.86Igrains per cubic foot of water asvapor. As air cools its capacity for holding moisture decreases. For example, at 15 F. one cubic footr of air can hold only about .218,grain. As the air from the warm room migrates into the wall and cools there may be condensation and a deposition of water.

In Figures 1, 2 and 3 the numeral Il] represents plaster and II represents a' plaster receiving base. The plaster receiving base may be and preferably is fiber board although plaster board and similar material can be employed. Associated Withthe plaster base is vapor barrier I2. Various forms of vapor barriers may be used so long as they retard the passage of vapor to about .5 gram or less per square foot in 24 hours when the interior temperature is about 70 F. at 40% humidity and the outdoor temperature is about 15 F. below.

Numeral I 3 represents a sheathing of such composition and formation that vapor will migrate therethrough at a rate of at least 8 times faster than through the vapor barrier. A sheathing that will permit vapor to pass at least grains per square'footin 24 hours under conditions above indicated will give a successful wall construction.

A sheathing that willproduce these results is a vegetable ilber board having a density of from about 16 to 25 pounds per cubic foot. Generally the sheathing should be about 25/az" in thick-` ness, but generally it may be said that sheathing should have a thickness of about 75" to' 1*/2".

In Figure 2,the stud spaces I5' are in part at least filled with insulating material I6. It is preferred that a dead air space be provided in the stud space, this dead air space preferably is adjacent to the sheathing.

Il.' a plaster receiving base is employed it is desirable to lock the joints between adjacent sheet or board forming vthe plaster base. The locking of such joint may be accomplished In various ways, but such an arrangement as disclosed in Figure 2 gives excellent results. The edges of the boards forming the plaster base are provided with an interlocking or over-lapping construction and secured to one of the abutting boards is lock I8 which extends across the joint and contacts the surface of the adjacent board.

In Figure 3 the warm side or inner panel is to be used without the addition of plaster. The vapor barrier may be used on either face but preferably on the room face side.

Heretofore, in many constructions the sheathing was seal coated or Va coated building paper was employed between the sheathing and the iinishing material. Such a construction prevents or tends to prevent the passage of vapor and moisure from the stud spaces. If it is desired to employ a paper between the sheathing and the finishing material. it should vbe-of a porous construction such as does not act as a vapor barrier. Coated paper should not be used as it retards the escape of vapor and moisture from the stud space.

The best and desirable result is obtained by employing a fiber insulating inner panel With a vapor barrier associated therewith and an outer insulating sheathing which permits vapor to pass therethrough at a relatively fast rate. Many modifications may be used which' give satisfactory results. For example, the inner panel may be plaster board having associated therewith a vapor barrier.

A vapor barrier may be provided with many materials and the following are the most economical to use and the most economical to apply.

A fiber board Il is coated with an asphalt or other bituminous compound by spreading over one surface melted asphalt. If only one coat of asphalt is used care must be used to see that there are substantially no air or pin holes therein. Generally, one coat of asphalt as heretofore ap- D plied does not prevent vapor passage. If only asphalt is to be used as a vapor barrier, to insure a safe vapor barrier at least two coats of asphalt should be employed.

In Figure l is disclosed a very successful vapor barrier which consists of a coating of asphalt I2 and a sheet of kraft paper 2|. To produce this kind of vapor barrier the base material II, such as for example fiber board, is coated with hot asphalt and when the asphalt becomes tacky the kraft sheet is applied and then the composite body passed through a hot calendering process. The calenderlng insures that substantially all of the small holes in the asphalt will be closed.

In Figure 5 is 'disclosed another form of vapor barrier that is highly eicient. The base material such as fiber board is coated with asphalt or other bituminous compound and -metallie granules are preferably applied while the compound is in a soft state. The Whole is then preferably rolled to evenly imbed the granules in the surface of the body layer. It has been found that the substance commercially known as bronzing powder may be used and the material preferably used is aluminum bronze powder which imparts a silver-like appearance. The grade of aluminum powder known as ne is well adapted for the purpose, although coarser grades may be used, and as little as 3 pounds of it is sufficient to coat one surface of athousand square feet, although a greater quantity is preferred.

In Figure 4 the plaster base I I is coated with plaster I9 or other interior nishing material. Associated with the plaster base I I is vapor barrier I2. Breathing sheathing I3 forms a part oi the coldside of the wall and secured thereto is finishing material 20.

What I claim is:

1. A wall construction comprising inner ber board panels having an `asphalt coating and a sheet of paper over the coating on one face of each panel, said coated panels having a vapor porosity of about 0.004 to 0.5 gram per square foot in 24 hours when indoor temperature is about F. at 40% humidity and the outdoor temperature is about -15 F., studding supporting the panels, liber board sheathing of about 16 to 25 pounds density per cubic foot and a vapor porosity of about at least 5 grams per square foot in 24 hours under conditions indicated, and siding material secured over said sheathing.

2. A wall construction comprising an inner fiber board panel having an asphalt coating and a sheet of paper over the coating on one face of each panel, means for locking the joint between adjacent panels, said coated panels having a vapor porosi-ty of about 0.004 to 0.5 gram per square in 24 hours when indoor temperature is about 70 F. at 40% humidity and the outdoor temperature is about 15 F., studding supporting the panels, liber board sheathing of about 16 to 25 pounds density per cubic foot and a vapor porosity of about at least 5 grams per square foot in 24 hours undertconditions indicated, and siding material secured over said sheathing HOBART F. WOODWARD.