Masonry Magazine March 1963 Page. 5
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Since water-retardant vermiculite masonry fill insulation is installed by the masonry contractor as the wall goes up, it offers an additional profit opportunity, another few cents per square foot of wall in clear profit. It is impossible for the vermiculite manufacturer to follow every job, but the masonry contractor is on the job when the need for insulation is immediately evident.
In promoting masonry wall insulation, the masonry contractor should be exceedingly careful in the type of insulation used. Such materials should meet the requirements of the Structural Clay Products Research Foundation. Some materials now offered for sale have not been tested by SCPRF and are not recommended. Untested materials may contribute to leaky walls and efflorescence. In promoting insulated masonry walls, economics is one of the strongest arguments. Reduced initial and operating costs are always important considerations to owners. Manufacturers and manufacturer's associations have recently prepared economic analyses of particular building elements which architects and engineers will find useful. As an example of this, the Ultimate Cost of Building Walls, published by the Structural Clay Products Institute, has found acceptance by the design professions. The Re Company has recently undertaken a study of the economics of thermal insulation for building enclosures. This report, MF-46, is available on request. It was prepared to be of particular assistance to the smaller architectural offices which, for most of their work, cannot afford to make intricate economic analyses.
Most architects know that annual costs for heating and air conditioning are reduced in proportion to a reduction in U value for building enclosures. Many, however, are unaware of the magnitude of the dollar savings which can accrue. It was the purpose of our report to provide a simple method of determining rapidly the annual fuel costs attributable to heat transfer through building walls and roofs. Heating and air conditioning costs are included for masonry walls.
A thermal economic coefficient has been computed for the United States. The product of this coefficient and the U value of the wall provides the annual thermal cost per square foot of surface area. The U value, or coefficient of heat transmission, depends on the type of wall and materials used. U values for many masonry walls are given in Table I. For building walls in common use in the United States, the range in annual fuel cost is about 60 per cent, from about 2/10 of a cent to 12c per sq. ft. per year. Even in the same climate, the spread is often more than 300 per cent.
An architect would be embarrassed at such a divergence in contract bids on the initial cost of his buildings. Yet such differences in operating costs are often ignored. For many owners, the operating costs are just as great as the initial cost in terms of capital outlay. For example, the Department of Defense and the New York State school system spend as much each year to maintain buildings as they do to build new ones.
The U value of uninsulated masonry walls is in the .25 range. The addition of insulation would reduce this up to 60 per cent. The economic effect of this reduction is to save up to 4c per sq. ft. of wall area per year, providing an annual return on the insulation investment of up to 40 per cent per year with an annual return of 25 per cent being more usual.
The derivation of the thermal economic coefficient is based on equations presented in the Guide and Transactions of the American Society of Heating. Refrigeration, and Air Conditioning Engineers. The study is meant to be applicable to smaller projects, and the assumptions made for the variables involved in the coefficient are predicted on that basis. We therefore used fuel consumption levels based on a gas-fired, fan-driven, warm air system. Most other systems would tend to increase annual operating costs. Fuel costs were estimated at 10c per therm (Continued on Page 18).
Table No. I
U VALUES*
COEFFICIENTS OF
HEAT TRANSMISSION (*)
SOLID BRICK AND BLOCK WALLS
Interior Wythe | Exterior Wythe | Uninsulated | Insulated
---|---|---|---
4 Face Brick | 4 Common Brick | .34 | .23
Concrete Black | (Lightweight) | .21 | .15
Concrete Block | (Lightweight) | .25 | .36
Concrete Block | (Sand & Gravel) | .43 | .31
CONCRETE BLOCK WALLS
Wall Thickness (Inches) | Type of Block | Uninsulated | Insulated | Furring and Plaster()
---|---|---|---|---
| | | Block Only | Furring Only | 1 Furring Space | 2 Furring Space | Plaster | Uninsulated | Insulated | Insulated
| Lightweight | .40 | .24 | .18 | .15 | .21 | .17 | .13 | .11
| Lightweight | .29 | .36 | .23 | .14 | .13 | .12
| Sand and Gravel | .30 | .15 | .12 | .05 | .27 | .30 | .22 | .37
(1) All masonry dimensions are nominal except as noted.
(0) % in gypsum lath and 16 in, of vermiculite gypsum plaster.
CAVITY WALLS
4 Exterior Wythe | Actual Cavity Dimensionin | Uninsulated | Insulated
---|---|---|---
4 Concrete Black | 296 | .34 | .13
4 Concrete Block | 416 | .34 | .13
Clay Tile | 216 | .08 | .08
4 Concrete Block | 416 | .13 | .12
(Lightweight) | 26 | .24 | .21
Concrete Block | 456 | .21 | .20
(Lightweight) | | .27 | .27
Concrete Block | | .25 | .25
(Lightweight) | | .13 | .08
4 Face Brick | | .27 | .27
4 Common Brick | | .24 | .12
Face | | .12 | .12
Common | | .25 | .25
Brick | | .23 | .11
Concrete | | .23 | .20
Block (cy | | .20 | .12
Cavity Insulated | 12 | .07
Block & Cavity Insulated | 10 | .00
Uninsulated | 22 | .22
Cavity Insulated | 21 | .21
Block & Cavity Insulated | 18 | .11
Uninsulated | NA | NA
Insulated | NA | NA
Aggregate same as interior wythe.
(1) NA: Not applicable.
• U values are expressed in Btu persoft-deg F