TABLE OF CONTENTS

1. INTRODUCTION
1.1. General
1.2. Objective and Scope
2. EXPERIMENTAL PROGRAM
2.1. Description of Test Specimens
2.2. Test Variables
2.3. Preparations for Testing
2.4. Test Procedure
3. TEST RESULTS
4. DATA ANALYSIS
5. DESIGN RECOMMENDATIONS

FIGURES
REFERENCES
APPENDIX A: TEST DATA.
APPENDIX B: MANUFACTURER'S INSTALLATION INSTRUCTIONS

1. INTRODUCTION

1.1. General

The Manufactured Home Construction and Safety Standards, 24 CFR §3280.403(e) requires certification of all primary windows to be installed in manufactured homes based on tests conducted at the design wind pressures specified in 24 CFR §3280.305(c)(1).

1.2. Objective and Scope

NTA, Inc. conducted negative wind pressure tests on the Aura Skylight Ventilator for the Aura Whole House Ventilation System with Natural Light for Active Ventilation Products, Inc. All tests were conducted at the NTA Test Laboratory located in Nappanee, Indiana. The purpose of this evaluation was to determine the allowable negative wind pressure on the Active Ventilation Products vent and to make design recommendations regarding its use. Tests were conducted on a representative sample of three ventilators. The ultimate negative wind pressure capacity for each ventilator was determined in accordance with the ultimate load test procedures set forth in 24 CFR §3280.401(b). These test results were then used to assess compliance with applicable HUD and AAMA standards.

2. EXPERIMENTAL PROGRAM

2.1. Description of Test Specimens

Each test specimen consisted of a 16-1/2 in. diameter cylindrical vent with clear polycarbonate glazing on the top and a 0.024 H-14 (half hard) aluminum, 18"x18" flange on the bottom. For installation, #8 x 3/4 in. stainless steel "pan-head" screws are fastened through the flange, inset 1-in. from the edges, and spaced at approximately 6-in. on-center (12 fasteners total).

2.2. Test Variables

The test variables in this experimental program were selected to simulate the worst anticipated field conditions. In doing so, the test results provide a reasonable lower bound strength. Test variables included the spacing and quantity of fasteners securing the skylight and the thickness of the sheathing material into which the fasteners are driven. For this investigation, #8 x 3/4-in. pan head screws, were placed approximately 6-in. on-center around the flange. This provided a total of 12 fasteners for securement. The withdrawal capacity of each screw, which is influenced by the thickness and grade of the material into which the screws are driven, was minimized by using 7/16-in. thick OSB to simulate roof sheathing. OSB of this thickness is typically the minimum thickness used as roof sheathing.

2.3. Preparations for Testing

The test setup consisted of a vacuum chamber constructed of 2 x 12 dimensional lumber and 7/16-in. OSB, as shown in Figures 1 and 2. This vacuum chamber was placed on a steel testing table that provided connections to a vacuum pump and a manometer.

Installation of the ventilator was conducted in accordance with the installation instructions supplied by the manufacturer. To install the ventilator in the vacuum chamber, a 10.5-in. diameter hole was cut in the center of the OSB top of the vacuum chamber. Next, the ventilator was centered over the hole and secured in place with twelve screws. Then, the ventilator/OSB test assembly was mounted on the 2x12 support box with the ventilator facing downward. A 6 mil polyethylene sheet, placed between the OSB and the ventilator and was used to apply the suction pressure. This plastic sheet was pleated along the inside of the ventilator to provide uniform contact with the interior surface of the vent and to allow for possible movement of the plastic during the test.

Instrumentation consisted of a water manometer and two dial indicators. The water manometer had a resolution of 0.1 inches of water for pressures between +52 inches of water. Dial displacement indicators were positioned to take deflection readings at the center of the skylight glazing and at the OSB inline with the fasteners, as shown in Figure 1. These indicators were capable of reading displacement to the nearest 0.001-in.

2.4. Test Procedure

Testing was conducted in accordance with the guidelines set forth by the Federal Manufactured Home Construction and Safety Standards, 24 CFR §3280.401(b). Accordingly, each specimen was loaded monotonically at 22.3 psf pressure increments. At each loading stage, deflection readings were taken at the glazing and at the OSB. Ten minutes were allowed to elapse between each loading stage. This procedure was repeated until a negative pressure of 111.3 psf was reached, after which the suction pressure was increased to ultimate. In accordance with 24 CFR §3280.401 (b), a total of three ventilators were tested in this manner.

3. TEST RESULTS

Ultimate negative pressures for the three tests are presented in Table 1. All three specimens behaved similarly during testing. Failure was not observed in any of the specimens up to the maximum obtainable test pressure. As a result, the maximum pressure was maintained for 10 minutes and the test was discontinued. Upon removal of the negative pressure, all specimens quickly returned to their original shape with no noticeable residual deformations or signs of distress.

4. DATA ANALYSIS

In accordance with 24 CFR §3280.401(b), the ultimate negative pressures were divided by a factor of safety of 2.5 to obtain allowable pressures, as listed in Table 1. The average allowable pressure, based on results from three tests, is presented as the allowable negative pressure for the Aura Skylight Ventilator for the Aura Whole House Ventilation System with Natural Light, as indicated in Table 2.

The test results were evaluated using the wind load criteria specified by 24 CFR §3280.305(c)(ii) and AAMA 1600-90, Section 8.3.3. The former specification, 24 CFR §3280, requires a negative design pressure of -89 psf for exterior roof coverings in Wind Zone III, which are within 3'-0" from the ridge and eave (overhang at sidewall) or sidewall if no eave is provided. The Aura Skylight Ventilator for the Aura Whole House Ventilation System with Natural Light evaluated in this experimental program has an allowable negative pressure of -90 psf, which exceeds the 24 CFR §3280 wind load criteria.

The latter specification mentioned, AAMA 1600-09, Voluntary Specification for Ventilators, provides comprehensive criteria and test procedures for evaluating and classifying ventilators. The test results contained herein address only the interior (negative) pressure test specified by AAMA 1600-09, Section 8.3.1. Pressures obtained by testing in accordance with Section 8.3.1 are used to establish an Exterior Loading Performance Class. Criteria provided by AAMA 1600-90 serves as the basis for this classification. Based on the average ultimate load, the Aura Skylight Ventilator for the Aura Whole House Ventilation System with Natural Light evaluated in this experimental program has a Negative Exterior Loading Performance Classification of 100. For this classification, a ventilator must withstand a negative test pressure of at least 150 psf. It is important to note that this performance class)fication is only for interior (negative) pressure, while the AAMA requires both exterior (positive) and interior (negative) pressure testing to establish an Exterior Loading Performance Classification. Exterior (positive) pressure testing may result in a lower classification.

5. DESIGN RECOMMENDATIONS

This test program clearly establishes that the Aura Skylight Ventilator for the Aura Whole House Ventilation System with Natural Light supplied by Active Ventilation Products, as evaluated in this test program, exceeds the strength requirements of 24 CFR §3280.403(b) when tested in accordance with the ultimate load test procedures stipulated by 24 CFR §3280.401(b). Additionally, the Aura Skylight Ventilator for the Aura Whole House Ventilation System with Natural Light, when class)fied in accordance with AAMA 1600-90, has an interior (negative) Exterior Pressure Classification of 100.

REFERENCES

Department of Housing and Urban Development (HUD). Manufactured Home Construction and Safety Standards & Interpretive Bulletins to the Standards April 1, 1995. 24 Code of Federal Regulations Part 3280. Office of Assistant Secretary for Housing, Federal Housing Commissioner, Department of Housing and Urban Development.

American Architectural Manufacturers Association (AAMA). Publication No. AAMA 1600-90: Voluntary Specification for Ventilators. Palatine: AAMA, 1990. 6 pas