New Construction Wall Details Install Instructions - 2
ACTUAL R-VALUES
Designed for optimal performance, this system uses the space required for the full specified insulation
thickness, isolates the conductive steel purlins/girts, and seals the insulation from interior air and moisture infiltration.
Insulative thermal breaks are used to minimize conduction. Every system is designed to perform at the specified Rvalue.
The user is responsible for providing suitable structure. Flexible insulation is considered within specifications with +/- 10% of thickness.
In-place insulation values are obtained by installing insulation in an actual structure, determining the average thickness
and multiplying by the tested R-value per inch. The conductive losses through purlins and girts are negligible
when thermally broken and isolated from interior air by the liner fabric.
The calculations of ASHRAE accurately predict insulation values of this method. Insulation R-values
and thicknesses shown are for 0.6 lb./ft. density fiberglass. High density yields higher R-values with less overall thickness.
ACTUAL R-VALUES OF OUTDATED INSULATION METHODS
Outdated insulation methods are often represented as the pre-installed R-values when they actually perform at far
less. This table reveals the truth about the traditional over the purlin/girt method.
Based on Formula: U=.012 + [0.255 / (.31Rf +t) ] (1-N / L) + (.198 + .065n) / L
Variables:
Rf = The sum of inside and outside air films R-value of .78 used for all calculations.
t = Pre-installed insulation thickness = see below.
N = Number of purlins or girts in the L dimension = ( L/spacing) +2.
L = Dimension of the building section in linear feet = 100 foot width used.
n = Fastener population per linear foot of purlin = one per linear foot used.
U = Heat loss in BTU per square foot- hour- degree Fahrenheit.
Notes: In-place insulation values shown above are for white vinyl laminated installed in traditional over-the-purlin method based on published Formula. The Formula has been verified to be accurate in a study conducted by the BROOKHAVEN NATIONAL LABORATORY for the DEPARTMENT of ENERGY and claims accuracy within 3%. In-place insulation values actually contained in a new building must be disclosed at the point of sale for the customer’s information and energy code compliance. Representation of insulation values greater than those indicated may be misrepresentation and in most states constitutes fraud.
Formula was derived from test data of non-reinforced vinyl faced insulation. Reinforced facings commonly in use are more resilient and are generally installed more tightly, resulting in greater compression of the insulation and less actual insulation performance than the above formula would indicate. Actual independent tests of the effects of reinforced facings on actual performance have not been made available to the general public. No valid representation of the in-place insulation performance with the reinforced facings can be made.
TIMA was an abbreviation for the Thermal Insulation Manufacturers Association, 1420 King St.# 410, Alexandria, VA.22314, (703) 684-0474. The formula for determining in-place R-value was published in the July issue of the Metal Construction News, in the letter to the editor. (Since this analysis was published, has changed it’s name to North American Insulation Manufacturers Association, or .)
The Brookhaven National Laboratory, Upton, Long Island, NY 11973, issued a final report of the study entitled: Metal Building Study: Performance of Materials and Field Validation dated December 1987 by W. Loss. The study was supported by the United States Department of Energy. BNL 52134
