Sound Transmission of an Exterior Insulated Rainscreen Wall (via - - PowerPoint PPT Presentation

Sound Transmission of an Exterior Insulated Rainscreen Wall

(via Field Testing and Acoustical Modelling) Wesley Narciso

Introduction Field Testing (Intensity Probe) Acoustical Modelling (SoundFlow) Summary Results and Discussion

Outline of Presentation

Drivers of building envelope design

Heat, air, moisture, vapour . . . . . acoustics

Lack of sound transmission field data, especially for walls Consulting industry

Letters of assurance (Schedule B – Sound Control)

Especially in noisy areas (e.g. bus stops, skytrains, railways)

Introduction

Field Testing

Field Testing

Wall Schedule

Gypsum wall board (0.5”) Fibrebatt insulation (6”) PT Plywood sheathing (0.5”) Moisture/air barrier XPS (1.5”) Wood furring (0.5”) Cedar shingles (0.5”)

Field Testing

Test Procedure

Temperature and humidity Façade dimensions (all areas) Background noise Set speaker inside room Measure sound pressure in room Measure sound intensity at wall exterior (discrete locations within a grid)

Equipment

Omni-directional speaker Intensity probe (GRAS) Soundbook and Samurai software 831 sound meter (Larson Davis)

Field Testing

Field Testing

Field Testing

0.0 10.0 20.0 30.0 40.0 50.0 60.0 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

Transmission Loss (dB) Frequency (Hz)

Transmission Loss and OITC Values

Wall Window Composite Window and Wall STC Reference Curve

Field Testing

* Other OITCs and STCs are taken from the IRC/NRC Internal Report, October 2000, Bradley and Birta (similar stud size and spacings to test wall)

Comparison with Laboratory Testing (IRC/NRC Report)

Wall Type OITC STC Face-sealed, vinyl clad 25 37 Rainscreen, vinyl clad 25 37 Face-sealed, vinyl clad (exterior insulated - 1" rigid fibre) 25 37 Face-sealed, vinyl clad (exterior insulated - 1" EPS) 26 37 Facade Specimen - rainscreen, cedar clad, 1.5" XPS 26 36 Face-sealed, vinyl clad (additional GWB) 27 39 Face-sealed, EIFS clad 27 38 Face-sealed, stucco clad 29 40

SoundFlow software

Simulation software for calculating the absorption, reflection, and transmission of sound by multi-layer structures Assumptions

Properties Areas Air gaps A/V barrier

Acoustic Modelling

Acoustic Modelling

20 40 60 80 100 120 140 160 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 Transmission Loss (dB) Frequency (Hz)

Transmission Loss of Test Wall

Wood Framing Wall Cavity Window Entire Composite Facade Studs and Cavity Composite STC Reference Curve

Split Insulated Rainscreen Wall OITC STC Field Tested 26 36 Acoustically Modelled 27 31

Acoustic Modelling

5 10 15 20 25 30 35 40 45 50 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

Transmision Loss (dB) Frequency (Hz)

Transmission Loss and OITC Values

Empty Cavity More XPS Empty Cavity (but 4.5" of XPS) No XPS (just rainscreen) Test Wall

Wall Type OITC STC Empty Cavity – No XPS 20 29 Empty Cavity (4.5" XPS) 21 30 Batt in Cavity (3“ XPS) 27 31 No XPS - Just rainscreen 27 31 Test Wall 27 31

Based on Field and Laboratory Testing

Test Façade

Great wall for heat, air, moisture and vapour, but not so great on sound insulation Windows - better at most lower frequencies Wall - better at most higher frequencies

Exterior Wall Design

What’s best for traditional/current BE design is not always best for sound insulation Stucco does well for acoustics but . . . Rainscreening doesn’t help with acoustics Exterior insulation had little effect Adding GWB can be a cheap and easy way to improve sound insulation

Summary of Results and Discussion

Based on Acoustical Modelling

OITCs are possible to compare and correlate Removing batt insulation is detrimental (even if you add exterior insulation); keep some sound absorbing material in the cavity (min 50 mm); split insulation is optimal Adding/doubling exterior thermal insulation (rigid) improves very little sound insulation

Summary of Results and Discussion