Lanterna Rally
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Roof Temperatures in Simulated Attics
Author: Jerrold E. Winandy
Publisher:
Published: 1995
Total Pages:
ISBN-13:
DOWNLOAD EBOOK →The degradation of wood treated with fire retardant (FR) chemicals in roof systems is a problem of major national significance. Understanding of this phenomenon is limited by lack of information on how the performance of FR-treated wood in the laboratory correlates to that of FR-treated wood in the field. In this study, five outdoor field exposure chambers were constructed near Madison, Wisconsin, in the summer of 1991. These structures were intended to simulate the gbsatticsgcs of multifamily structures for which model building codes sometimes allow the use of FR-treated roof sheathing. Interior attic air, exterior air, inner and outer sheathing, and internal rafter temperatures of black- and white-shingled chambers were monitored. Temperatures were measured using thermocouples and recorded over a 3-year period from October 1991 through September 1994 using a datalogger/multiplexer device. Overall, the plywood sheathing in black-shingled roof systems tended to be 10ÃF to 15ÃF (5ÃC to 8ÃC) warmer during the midafternoon of a sunny day than the plywood in comparable white-shingled roof systems. The maximum sheathing temperatures recorded were 168ÃF (76ÃC) for blackshingled roofs and 147ÃF (64ÃC) for white-shingled roofs. The results suggest that roof-sheathing plywood and rooftruss lumber temperatures, which are the primary factors that influence thermal degrade of FR-treated materials, are primarily controlled by solar gain rather than attic ventilation or attic insulation. These results are tempered by the fact that the effect of moisture content was not evaluated nor was moisture controlled by attic ventilation.
Roof Temperature Histories in Matched Attics in Mississippi and Wisconsin
Author: Jerrold E. Winandy
Publisher:
Published: 2000
Total Pages: 28
ISBN-13:
DOWNLOAD EBOOK →To address the problem of defining actual field temperatures of various wood components in wood-framed roof systems, roof temperatures were monitored in test structures situated in the northern and southern United States (Madison, Wisconsin, and Starkville, Mississippi, respectively). The field exposure structures were intended to simulate the attics of multifamily wood-framed structures for which Model Building Codes sometimes allow the use of fire-retardant-treated roof sheathing. The structures were instrumented to monitor interior attic air, exterior air, inner and outer plywood roof sheathing, and internal rafter temperatures in dry whiteshingled structures and both dry and heavily humidified black-shingled structures. Temperatures were recorded from January 1992 through December 1999 in Wisconsin and from January 1996 through December 1999 in Mississippi. The Mississippi exposure generally induced 5ÃC to 10ÃC higher temperatures than did the Madison exposure, though the difference in annual maximum gbs1-h averagegcs temperature of both exposures was usually no more than 3ÃC to 4ÃC. Overall, black-shingled roof systems tended to be 5ÃC to 10ÃC warmer during the midafternoon of a sunny day than were comparable white-shingled roof systems. Few differences in plywood roof sheathing temperatures were noted between dry and heavily humidified structures. Attic airspace and rafter temperatures were generally 5ÃC to 10ÃC cooler in humidified attics than in dry attics. The major difference in the temperature of wood components in the Wisconsin and Mississippi structures occurred during the winter, when temperatures were as much as 20ÃC lower in Wisconsin.
FPL Roof Temperature and Moisture Model
Author: Anton TenWolde
Publisher:
Published: 1997
Total Pages: 48
ISBN-13:
DOWNLOAD EBOOK →This paper describes a mathematical model developed by the Forest Products Laboratory to predict attic temperatures, relative humidities, and roof sheathing moisture content. Comparison of data from model simulation and measured data provided limited validation of the model and led to the following conclusions: (1) the model can provide reasonably accurate estimates for temperatures of roof sheathing and attic air, although heat storage effects often cause delay of 1 to 2 h in attic air temperatures; (2) the model can accurately predict the frequency of occurrence of high roof sheathing temperatures (> 120ÃF (49ÃC)) during summer, but accuracy is highly dependent on solar absorptance and emissivity values of the roof shingles; (3) the model consistently overpredicts the extent of night-time cooling from sky radiation losses, leading to predicted temperatures that are too low; (4) treatment of the effect of snow cover is too simplistic, but no better alternatives are apparent for simulating this very complex behavior; (5) the model apparently can predict average moisture conditions in the sheathing with reasonable accuracy, generally within 1% moisture content, when moisture content is not excessively high or low; and (6) hourly moisture behavior is not represented as well as is daily or seasonal behavior, especially for north-facing sheathing. The model would benefit from verification with data that include measured emissivity and solar absorptance of the shingles, addition of thermal mass in attic and roof, better algorithms to calculate direct and diffuse solar radiation, and verification for roof with east--west orientation.
Research Paper FPL-RP
Two-year Wisconsin Thermal Loads for Roof Assemblies and Wood, Wood-plastic Composite, and Fiberglass Shingles
FPL Roof Temperature and Moisture Model
Research Note FPL.
Predictor Sort Sampling, Tight T's, and the Analysis of Covariance
Author: S. P. Verrill
Publisher:
Published: 1996
Total Pages: 420
ISBN-13:
DOWNLOAD EBOOK →In recent years wood strength researchers have begun to replace experimental unit allocation via random sampling with allocation via sorts based on nondestructive measurements of strength predictors such as modulus of elasticity and specific gravity. Although this procedure has the potential of greatly increasing experimental sensitivity, as currently implemented it can easily reduce sensitivity. In this paper we discuss the problem and we present solutions. Given the existence of nondestructive measurements of strength predictors, our methods can be used to reduce sample sizes. We have written a public domain computer program that implements the methods.
Efficient Utilization of Red Maple Lumber in Glued-laminated Timber Beams
Author: John J. Janowiak
Publisher:
Published: 1995
Total Pages: 394
ISBN-13:
DOWNLOAD EBOOK →The feasibility of utilizing cant-sawn hardwood lumber, which would not usually be desired for furniture manufacture, was studied for the manufacture of structural glued-laminated (glulam) timber. Two red maple beam combinations were evaluated: (1) a glulam combination designed with E-rated lumber in 25 percent of the outer laminations (top and bottom) and No. 3 grade lumber in 50 percent of the center laminations and (2) a wide-width glulam combination with laminations made from nominal 2- by 4- and 2- by 6-in. No. 2 grade lumber laid edge-to-edge having staggered end joints (termed 2 by 4/2 by 6 glulam combination). Test results of 42 red maple glulam beams showed that it was feasible to develop structural glulam timber from cant-sawn lumber. The glulam combinations made from E-rated lumber exceeded the target design bending stress of 2,400 lb/in2 and met the target modulus of elasticity (MOE) of 1.8 Ã 106 lb/in2. In addition, the 2 by 4/2 by 6 glulam combination exceeded published design stresses for vertically laminated bending strength, MOE in both the horizontally and vertically laminated orientations, and horizontal shear stress in the vertically laminated orientation. Based on the results of the 2 by 4/2 by 6 glulam combination, it was determined that edge gluing the laminations to form wide-width lumber is not required to achieve targeted strength and stiffness levels. Data analysis showed that ASTM D3737 procedures developed for softwood species accurately predict beam stiffness and provide conservative bending and horizontal shear strength estimates for red maple glulam beams. Also, it was shown that results from ASTM D143 shear-block tests could be used to accurately predict horizontal shear strength of 2 by 4 and 2 by 6 red maple glulam beams.
