Acoustic building infiltration measurement system

Abstract

Building infiltration is a significant portion of the heating and cooling load of buildings and accounts for nearly 4% of the total energy use in the United States. Current measurement methods for locating and quantifying infiltration in commercial buildings to apply remediation are very limited. In this talk, the development of a new measurement system, the Acoustic Building Infiltration Measurement System (ABIMS) is presented. ABIMS uses Nearfield Acoustic Holography (NAH) to measure the sound field transmitted through a section of the building envelope. These data are used to locate and quantify the infiltration sites of a building envelope section. The basic theory of ABIMS operation and results from computer simulations are presented.

Full text

Better Decisions + Better Technology = Better Buildings
Building Energy Decision and Technology Research Program
BEDTR
Acoustic Building Infiltration
Measurement System (ABIMS)
Ralph T. Muehleisen and Eric Tatara, Argonne National Laboratory
Energy and Global Security Directorate
rmuehleisen@anl
Ganesh Raman and Kanthasamy Chellia, Illinois Institute of Technology
Mechanical, Materials, and Aerospace Engineering

Outline
What Is Building Infiltration and Why Should I Care?
Measuring Infiltration and The Problem with Current Systems
The ABIMS System: How Does This Work?
NAH
Next Steps / Future Work
This work was funded by Argonne National Laboratory under
Contract No. DE-AC02-06CH11357 from the U.S. Department of
Energy.
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 2

What is Building Infiltration?
Simply put, building infiltration is the uncontrolled leaking of
unconditioned air into a building from pressure differences
between the building interior and exterior
These pressure differences are
primarily caused by
Wind
Thermal Buoyancy (Stack
Effect)
Occupant Entry/Exit
HVAC pressurization
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 3
Wind Effect Stack Effect

Why Should I Care?
28%
30%
42%
Total Energy Use
Buildings
Industry
Transportation
Simply put, infiltration is
estimated to be as much as
20% of the space heating
and cooling energy used in
buildings in the US.
–That’s about 4% of all energy
use in the US!
Building pressurization (to
reduce infiltration) does not
reduce that heating or
cooling load unless heat
recovery is used on air
intakes
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 4
15%
30% 55%
Residential Energy Use
Space
Heating and
Cooling
Water Heating
All Others

Current Systems for Measuring Infiltration
Only one primary method is used for
measuring infiltration: building
pressurization testing
–Generate a known P between the interior
and exterior and measure flow rate
required to maintain it
–Usually implemented using a blower door
test
–For large buildings, extremely large fan
systems (usually gas engine powered)
inserted into large loading dock doors are
required
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 5
http://en.wikipedia.org/wiki/File:Minneapolis_Blower_Door.jpg

The Problem
The blower door method is really limited to smaller
buildings and construction must be complete. This
means:
You can’t do the test during construction which
means you can’t require the test as part of code
It is disruptive to the occupants, so companies are
very reluctant to do it as an evaluation for retrofits
It is really hard to do for large buildings
Also, the blower door method quantifies total leakage
but does not identify leak location
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 6

The Solution: The Acoustic Building Infiltration
Measurement System
7
Muehleisen:2pSA Acoustic Building Infiltration Measurement System

How Does This Work?
Speaker on interior generates multiple tones,
swept sine, or broadband random noise
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 8

How Does This Work?
Sound propagates through cracks and by
structural vibration
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 9

How Does This Work?
Propagated Sound Pressure and Velocity is
Measured at a Distance by Nearfield Acoustic
Holography (NAH)
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 10

How Does This Work?
Sound Through Cracks and Structural
Vibration Separated by Looking at Impedance
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How Does This Work?
Acoustic Transfer Impedance Converted Into
Static Flow Infiltration Estimate
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NAH for Estimating Exterior Pressure and Velocity
Investigating standard Fourier Transform, Boundary Element
Method (BEM) and Equivalent Source Model (ESM)
implementations of NAH
So far ESM with Generalized Cross Validation (GSV) method
looks to be the best for our purposes
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Static Flow Through Orifices
Static Flow (Infiltration) is well described by incompressible 1-D Navier Stokes
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 14
 

  

   

 



 
DxHxL Long Straight Crack DxHxL Very Short Crack General Crack (mixed)
2
22
1
2
pQ
DH


3
12 L
pQ
DH


2
p AQ BQ  
L

Next Steps
Develop relations between Acoustic Transfer Impedance of
crack, Zcrack, and static flow coefficients A and B
A is related to viscous losses and hence real part of acoustic
impedance. We expect that we will develop a relation of the
form
B is inversely related to area of crack. We can estimate the
area from the NAH measurements
Alternately, we can develop correlations between the
acoustic impedance Zcrack and the coefficients A and B
through CFD Analysis
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 15
 
 
0
Re crack
AZ





Future Work
Over the next year the team will
Finalize NAH algorithms
Finalize relations between acoustic impedance and
static flow (infiltration) parameters
Construct and Test ABIMS system prototype
Muehleisen:2pSA Acoustic Building Infiltration Measurement System 16

Thank you.
Questions?
17
Ralph Muehleisen
630-252-2547
RMuehleisen@anl.gov
Muehleisen:2pSA Acoustic Building Infiltration Measurement System