Whole House Fan With Latent Heat Recovery
ME 481 Multi-College Program
Modeling
Economic Analysis
Fluid Dynamics:
• Computational Fluid Dynamics (CFD) in Fluent
• Models examined flow patterns in attic for a variety
. of conditions
• Used to validate the need for ducting on fan
• Energy equation used to predict temperature layers
and fan run time in addition to heat transfer analysis
Project Sponsor
Academic Advisors
Bob LaZebnik
Airmaster Fan Company
Dr. Brian S. Thompson
David Regan
Michael F. Lobbestael
Engineering
Marketing / Advertising
Andrew Gillett
Chad Kleinow
Andrew Kruk
Kevin McKay
Chrystal Kozsey
Melissa Poirier
Alyse Solomon
Special Thanks to:
Heat Transfer Analysis:
Model predictions based on Florida Temperature Study
Based on:
68oF thermostat setting
Above 75oF in attic
Below 64oF ambient air
Attic/Ambient Air Temperature Distinction
110
Degrees (oF)
80
Average
Ambient Temp
(°F)
Operation Time
Points
52
57.8
1 hours
53
58.9
2 hours
54
60.0
3 hours
55
61.1
4 hours
56
62.2
4 hours
57
63.3
2 hours
58
64.5
3 hours
59
65.6
1 hours
60
66.7
1 hours
Operating Range
60
$9.71 per year
Natural Gas
$9.71
$2.04
$4.82
2
3
4
5
6
7
8
9
10 11 12
13 14 15
16 17 18 19
20 21 22
$6 - $9
Attic Temperature for 80°F Day
Average Ambient Air Temperature = 55°F
Attic Temperature for 55°F Day
Completed an energy balance to
check temperature predictions
with new temperature study data
qsolar
qo (reflected)
qreflected 
Shingle
Temp (K)
Specification
Average
310.25
Measured
Temp (K)
310.97
Error
2.41%
(Ts  T )
1
1
(

)
ho A hr A
qo + qin = qsolar
Roof Plywood
(T  T )
qin  s a
Rthermalcircuit
House Information
Size = 1700 sq. feet
Dark Shingle Roof
Location = Cocoa, Florida
1.
Opto22 G4OAC5 Solid State Relays
(SSR)
2. Opto22 120D10 SSR(High Speed)
3. DS1620 Digital Thermometers
Ducting
• 20” Plastic duct added to fan
• Decreases chance of debris pickup
• Increases fan access to warm air layer at top of attic
1.63
4.82
Years
$7.87
4.
5.
6.
BS2 Basic Stamp Microcontroller
ULN2803A Line Driver
AO Smith 1/3hp Motor
1
2
Capabilities:
Attic temperature distribution from
Florida study
0.84
9.3
Years
Components:
1
Metal strip
for strength
Payback
Period
Control System
2” x 6” Roof Joist
qin
Profitability
Index
-$7.20
Rising Energy
Prices
Model is valid!
Ducting before and after metal strip was added
Net Present
Value
Finance Parameters
Asphalt Shingles
Hour
Average Ambient Air Temperature = 80°F
Location
Arizona
New York
$4 - $6
Current Energy
Prices
23 24
LPG
$18.49
$4.01
$9.18
$2 - $ 4

qsolar  qnetsolar
 arearoof
1
• Supplement current HVAC System
• Solid State Controls
• Regulate operation of fan based on seasonal setting and
. temperature data
• Minimal input from user after initial setup
• System should be cost effective and provide energy savings to
. customer
$10.53 - $0.82
Map Key
70
40
• Design and develop a control system that will enable a whole house
. fan to recover heat from a hot attic and return it to living space
• Predict attic temperatures and determine fan operating conditions
• Estimate a yearly cost savings associated with recovered heat
• Develop market and advertising strategies for product release
15,000 kJ / day
$ Annual Cost
Savings
Annual Cost
Savings by State
Average
Attic
Temperatu
re
90
50
Problem Statement
90 days
Furnace cost for
energy – motor
electricity cost
Comparison of velocity vectors and temperature for fans with and without ducting
100
• Reduce energy usage within the home by recovering heat from attic
. and using it to supplement the house heating system
Energy pulled into
house per sunny
day
Maximum
Minimum
Average
Dr. Gregory Wierzba - ECE Brian Wright - ECE
Dr. Neil T. Wright - ME
Todd Burghgraef – DornerWorks
Purpose
Number of sunny
days within
temperature range
Summer Mode
• Evaluates actual room temperature and
. desired temperature set by user
• If the room is too hot, the fan turns on high
. speed exhaust
• If the room is too cool, fan does nothing
3
5
4
Winter Mode
• Evaluates actual room temperature and
. desired temperature set by user and
. compares them to the attic temperature
• Attic must be more than 5 degrees hotter
. than the desired room temperature
• Room temperature must be less than desired
. temperature