The Case for Energy
Recovery in addressing
Commercial Building
Indoor Air Quality
Fundamentals
Common Misconceptions
Performance Certification
Applications
Learning Objectives
Improve and broaden dialog concerning the role and
importance of Energy Recovery Ventilation
Define Energy Recovery Ventilation
Review fundamental terms involved in description and
operation of Energy Recovery Ventilation
Review the fundamentals to apply effective and reliable
Energy Recovery Ventilation
Compare and Contrast common Energy Recovery
Ventilation Media
Applications
Why Energy Recovery?
Address issues related to Indoor Air Quality
Improve heath and productivity of occupants
Elevated CO2 levels
Moisture control
Off gassing of Volatile Organic Chemicals
Comply with energy codes
Save energy / reduce energy consumption
Building Functionality and Economics
Reduce HVAC system costs
Indoor Air Quality Basis of Discussion
Rate of ventilation air required, most often by
mechanically induced (forced) outside
(ventilation) air
ASHRAE 62.1 for CII Buildings
ASHRAE 62.2 for low-rise residential buildings
LEED Increases ventilation rates over ASHRAE
standard
What is “Ventilation Air”? The Air used to provide acceptable indoor air quality per
prescribed ventilation rates outlined in ASHRAE Standard 62
HOURS
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
M 1 2 3 4 5 6 7 8 9 10 11 N 1 2 3 4 5 6 7 8 9 10 11 M
PP
M C
O2
(T
HO
US
AN
DS
)
OSHA
800 PPM
CO2 LIMIT
ASHRAE-1000
PPM CO2 LIMIT
PRESCHOOL FACILITY- CO2 levels obseved
Before Ventilation Strategy
OUTDOOR
300-400 PPM CO2
Why Ventilate?
HOURS
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
M 1 2 3 4 5 6 7 8 9 10 11 N 1 2 3 4 5 6 7 8 9 10 11 M
PP
M C
O2
(T
HO
US
AN
DS
)
PRESCHOOL FACILITY- After ERV Installation
OSHA
800 PPM
CO2 LIMIT
ASHRAE-1000
PPM CO2 LIMIT
TIME
CLOCK
TURNED
OFF - ERV
TIME
CLOCK
TURNED
OFF - ERV
Why Ventilate?
OUTDOOR
300-400 PPM CO2
Fundamental Terms Differences in performance and cost is significant
ERV aka:
Energy Recovery
Ventilator
Heat Exchanger
Sensible and Latent
Recovery
Energy Wheel
Static Plate Core
Enthalpy
Enthalpic Plate
HRV aka:
Heat Recovery Ventilator
Sensible Recovery
Heat Exchanger
Energy Recovery Ventilation
Opportunities Every commercial
building needs
ventilation
Cost Benefits
Downsize HVAC equipment
Reduced ductwork
complication
Favorable payback
Quantifiable energy savings
Rebates (where applicable)
Performance Benefits
Decouple ventilation from space
conditioning
Demand control ventilation
Humidity control
Capture exhaust energy
Fundamentals of Energy
Recovery Ventilation
Summer: Pre-cooling /drying of hot & humid
incoming air
Winter: Pre-heating/humidifying of cold & dry
incoming air
Transfers upwards of 55 - 75% of the energy in
the exhaust air stream to fresh air stream
Wheels or Plates are most common
Elements of Properly
Applied ERV
Performance
Media independently certified - AHRI
Ratio between highest energy recovered
vs. lowest device operation energy
consumed in the recovery process • (vs. cost / footprint)
Recovery Efficiency Ratio (Guideline V)
Elements of Properly
Applied ERV Value
Easy to drop into HVAC systems
Minimal complexity
Minimal maintenance
Minimal commissioning effort
Elements of Properly
Applied ERV
Reliability
• Performance and operation is consistent
and reliable as HVAC equipment
applied on project
• Confident in downsizing the HVAC
equipment
One-Year Example of Adding
a Commercial 1850 cfm ERV
3.8 tons cooling equipment downsize
(Conventional AC system avoided installed cost
$5,700)
Annual energy savings $2,387.98
Annual demand savings $276.07
Total energy savings $2,664.05
Simple payback: 0.5 years
Software selection tools
General ERV Selection
ERV Selection – Core/Wheel CFM Per air stream (leaving EA/ entering OA)
Static Pressure Drop
Summer/winter weather data (ASHRAE standard)
Electrical voltage, phase and horsepower required to operate
ERV
ERV Selection – Wheel Specific Purge air - Project schedules will show an imbalance of up to
50% between EA/OA
• Common for Wheel ERV to clean media surface
Cross leakage/contamination consideration
Condensate/defrost strategy consideration
Common Energy Recovery
Media / Packages
Core material: Aluminum or Plastic
Core material: Hydroscopic Resin
20-30% total effectiveness
Sensible only recovery
HRV: Heat Recovery Ventilator
Sensible and Latent recovery
ERV: Enthalpy Core
60-65% total effectiveness
ERV: Enthalpy Wheel
70-80% total effectiveness
Sensible and Latent recovery
Wheel material: • Aluminum
• Synthetic Fiber
• Polymer
Manufacturers: Fantech, Lifebreath, Venmar
Manufacturers: Greenheck, SEMCO
Manufacturer: RenewAire, S&P, Mitsubishi
HRV: Sensible Core
Numerous Media Manufacturers
Packaged HRV Equipment
Common Transfer material
Aluminum
Polypropylene
Performance
The return and supply airstreams pass
within air passages perpendicular to
each though the plate material
Liquid water is a common byproduct
Critical Media Components
End pans and frame
Defrost
Drain pan
Associated plumbing
ERV: Enthalpy Wheel
Transfer Performance Media rotates between the
airstreams transferring the energy
from exhaust airstream to the
supply airstream
Critical Media
Components Cassette
Bearings
Wheel Segments
Wheel Drive Belt & tensioner
Pulley
Wheel Motor
Frost control
ERV: Enthalpy Wheel
Packaged Options
300 to 20,000 cfm Indoor and Rooftop
Stand Alone Energy
Recovery Ventilator
Energy Recovery
w/Heating
Energy Recovery
w/Heating and Cooling
Energy Recovery
w/Evaporative Cooling
Dedicated Outdoor Air
Systems
ERV: Enthalpy Core
Transfer Performance
Air passages perpendicular to
each airstream though the plate
material
Sensible via conduction
Latent via diffusion
Straight Air Passages
Laminar Flow
Typical Velocity
250 - 500 ft./ min.
Static pressure loss
0.6 – 1.2 inch
ERV: Enthalpy Core
Packaged Options 70 to Unlimited cfm Indoor and Rooftop
Stand Alone Energy
Recovery
Dedicated Outdoor Air
Systems
Energy Recovery
Bypass
Tight Humidity Control
Performance
AHRI Certification
UL 1812 flammability rated
Design and Construction
Symmetrical/well
proportioned
Fully adhered construction
Unobstructed airflow
Similar transfer materials
Critical Media Components
End pans and frame
Attributes of a Superior
Enthalpy Core
Addressing Common
Misconceptions
Media performance, correct equipment sizing and
application, warranty and maintenance influence actual
performance
Static plate core:
Is made of a high engineered polypropylene
Core will not burn
Core will transfer sensible and latent energy
Energy Star does not have a U.S. standard for HRV and
ERV
AHRI-1060 certified versus performance in accordance with
AHRI -1060 standards or some other standard
ERV Design Ideas: Downsize Heating and Cooling Equipment
Retrofit: Preconditioning OA with ERV can allow
conventional Heating and Cooling systems to
remain unchanged
Increases in outdoor air load w/o increasing
the size of the equipment
ERV Design Ideas: Downsize Heating and Cooling Equipment
New: Preconditioning OA with ERV allows for
downsized HVAC equipment • New ERV technology is more reliable making downsizing
more viable
• Oversized H&C equipment is expensive and inefficient
• Increase H&C system efficiency
• Reduce H&C equipment cost
• Payback on ERV cost <5 yrs
• Annual energy savings
ERV Design Ideas: Peak Load Reduction
Oversized AC is inefficient, ineffective and
expensive
Can lead to short cycling
ERV can be a strategy to manage peak
load
Largest contributor to peak load is ventilation
Tie ERV in to BMS or apply zone
approach
ERV Design Ideas: Recirculation of Toilet Exhaust
ASHRAE Standard 62.1-2010, Section 5.16.3.2.5 Class 2 air shall not be transferred in to Class 1 spaces
Exception – When using an energy recovery device, recirculation
from leakage (EATR), carryover or transfer (Purge air) from the
exhaust side of the energy recovery device is permitted
• Not to exceed 10%
Another Option: An AHRI 1060 rated static plate core with no recirculation through
the core for defrost
• 0% EATR
• 0% purge air
ERV Design Ideas: Must Use Ventilation Wheel to Control Humidity
City 75°F WB 73°F WB 70°F WB
Detroit 10 75 238
New York 29 78 495
Washington DC 170 328 735
Columbus 0 149 475
Pittsburgh 0 52 235
Columbus 0 149 475
Boston 11 61 201
When outdoor air conditions are dryer than 70wb, RenewAire total effectiveness is
comparable to most Wheels
At most locations around the US there are very few ventilation hours where the wet
bulb temperature exceeds 70 degrees
National Weather Service 40-year weather data bin hours / 8760 hours p/yr / ASHRAE Design Test
Conditions 95/78
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
0 20 40 60 80 100 120 140 160 180
Wheel
Heat Pipe
Plate
RenewAire
ARI-1060 Winter Sensible
Unit Number
Eff
ec
tive
ne
ss
Median
ARI-1060 Summer Total
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 20 40 60 80 100 120 140 160 180
RenewAire 78 WBWheelHeat PipePlateRenewAire 75 WBRenewAire 73 WBRenewAire 70 WB
Unit Number
Eff
ec
tive
ne
ss
Median
ERV Design Ideas: Zoning ERV
Supports space sensitive, architectural and
historically sensitive building requirements Mechanical room not required
Smaller equipment and smaller duct diameter
• Duct space only required above ceiling
Eliminate large rooftop footprint
Source point controls are low cost and simple Operation is based on ASHRAE ventilation rates
Simple, lower cost, less complex maintenance Maintenance affects the zone, not entire building
ERV Design Ideas: Replace non process exhaust fans with ERV
CFM/watt consumed per airstream (OA/EA) Energy Star standard for bathroom and utility room fans is 2.8 watt
p/cfm (EA only)
ERV cfm/watt can be competitive depending on the manufacturer
Compare and contrast Fan exhausting 100% of heating and cooling
ERV recapturing up to 75% of heating and cooling
ERV Advantages
Payback of ERV: <5 yrs
Advantages of ERV remain for 10+ years
IAQ advantages
ERV Design Ideas: Simple ERV CO2 control with RTU Economizer
Separate static-plate ERV from RTU
RTU economizer runs standard based on
enthalpy control
ERV runs based on CO2 control from the
space
Simple, self-correcting system control!
ERV Design Ideas: Simple ERV CO2 control with RTU Economizer
Economizer conditions: 55F DB OA, cooling mode
RTU opens economizer panel for free cooling
CO2 levels drop quickly in the space
ERV turns off
ERV Design Ideas: Using ERV with a VRF system
VRF fan coil units have strict EAT ranges
Bringing in too much untreated outside air may cause the mixed
EAT to be outside the acceptable range
Using a zoned or central ERV can bring EAT to an acceptable
temperature without needing a full DOAS system!
Typical Heating EAT Range
59°F DB 81°F DB
Typical Cooling EAT Range
59°F WB 75°F WB
ERV Design Ideas: Using ERV with a VRF system
OA 300CFM 5F DB
RA 706 CFM 70F DB
Mixed Air 1006 CFM
50.8F DB
Without ERV: Unacceptable EAT
Typical Heating EAT Range
59°F DB 81°F DB
With ERV: Acceptable EAT
OA 300CFM 51.2F DB
RA 706 CFM 70F DB
Mixed Air 1006 CFM
64.4F DB
AHRI 1060-2005 Exchange Media Certification
Pressure drop in e.g. @ 100% cfm
Effectiveness @ 100 & 75% rated cfm
for heating and cooling conditions
Sensible
Latent
Total
Exhaust Air Transfer Ratio, Outdoor Air
Correction Factor, and Purge Angle or
Setting (if applicable) at 0.00 in H2O
[0.0 Pa] and two or more pressure
differentials
Tested at Balanced Airflow
Performance at “Standard
Conditions”
Winter -
OA= 35°Fdb, 33°Fwb
RA=70°Fdb, 58°Fwb
Summer -
OA= 95°Fdb, 78°Fwb
RA= 75°Fdb, 63°Fwb
Required by ASHRAE 90.1 Addendum E. and where rebates are available to be
submitted with application
comparison of energy-recovery technologies
Typical Performance
airside pressure drop (per side), in. H2O
0.2 0.8 1.2 0.6 0.4 1.0
coil loop
HRV plate heat exchanger
heat pipe
HRV wheel
ERV wheel
ERV Enthalpy Plate Exchanger
comparison of energy-recovery technologies
Typical Performance
effectiveness, %
30 60 80 50 40 70
coil loop
HRV plate heat exchanger
heat pipe
HRV wheel
ERV wheel
sensible
sensible
sensible
sensible
sensible latent
sensible latent
ERV Enthalpy Plate Exchanger
comparison of energy-recovery technologies
Typical Performance
Outdoor Air Correction Factor
100 160 140 120 180
Heat Pipe
HRV Sensible Plate Exchanger
ERV Wheel
ERV Enthalpy Plate Exchanger
110 130 150 170 190
comparison of energy-recovery technologies
Typical Performance
Exhaust Air Transfer Ratio
0 6 4 2 8
Heat Pipe
HRV Sensible Plate Exchanger
ERV Wheel
ERV Enthalpy Plate Exchanger
1 3 5 7 9
Comparison of energy-recovery technologies
Typical Frosting Conditions
outdoor temperatures at which frosting typically occurs, °F
-50°F 10°F 50°F -10°F -30°F 30°F
coil loop
HRV plate heat exchanger
heat pipe
HRV wheel
ERV wheel
557 hrs
(1788 hrs) 12 hrs
(79 hrs)
7 hrs
(25 hrs)
Chicago, IL 6 AM – 6 PM, weekdays
(all hours, all days)
ERV core
Exchange Media
Flammability Rating
All components pass UL-723 test for burning characteristics of
building materials
Less than 25/50 flame spread/smoke developed rating
The basic standard:
UL 1812 “Ducted Heat Recovery Ventilators.”
National Fire Protection Association (NFPA) 90A and 90B
90A: Standard for air conditioning and ventilating systems
90B: Standard for warm air heating and air conditioning systems
ERV Maintenance
Comparison
Wheel Routine Inspection / Replacement
Components Wheel cassette
Drive belt
Belt motor
Air seals
Defrost
Cleaning Procedure Short soak
Overnight soak
Media Remove and Reinstallation Segments
Entire wheel
Replace Filters
Core
Routine Inspection Core face
Filters
Cleaning Procedure Vacuum core face of any accumulated
particulate
Media Removal and
Reinstallation Not required
Replace filters
ERV Media Warranty
Comparison
Enthalpy Wheel:
Five year warranty
against manufactures
defects and
workmanship * Source: Airexchange
Enthalpy Core
Ten year performance
warranty against
performance
degradation * Source: RenewAire
ERV Application Examples And Common Attributes
Non process exhaust
AHRI 1060 Certified Media Recovery effectiveness
0% Cross Contamination
Zero Purge Air
No active defrost deployed
10-year performance warranty
Zone or Central ERV Approach
Zone Ventilation
Codify all Building Exhaust Points into a Ventilation
List
• Satisfy the intake air of “Suitable Exhausts” with ERV
• Satisfy the Replacement of Non-Recoverable Exhausts with
Makeup Air Equipment
• Satisfy any Remaining Balance of intake air with Fans,
Makeup Air Equipment or the equivalent
Central Ventilation
Feed building ventilation in to one centralized system
Distribute out to individual VAV boxes or fan coils
Zone Energy Recovery
1 indoor
Horizontal ERV
Two restroom
exhaust points
Exchanging
450 CFM fresh
air into building
Roof Top Connect in to Air
Handling Unit 14 rooftop ERVs
Exchanging 21,000 CFM
fresh air into building
Manifold Stack -(3)- CA4X Units
Packaged Air
Conditioning Unit
Fresh Air Blower
Service Area
Exhaust Air Blower
ERV Media Installed in Air Handling System
ERV
Cabinets
ERV Media Integrated
in to HVAC System
1 indoor ERV cabinet
Integrated in to HVAC
system
Exchanging 3,000 CFM
fresh air into building
ERV Core Custom Application:
Hospital Installation 4 indoor ERV cabinets
Integrated in to custom
enclosure and third party
fans and blowers
Exchanging 8,000 CFM
fresh air into building
Discussion Resources Other Sources ahridirectory.org
ashrae.org/
epa.gov/
hvi.org/ ul.com/global usgbc.org/ energystar.gov/ nfpa.org/index.asp
renewaire.com ERV Calc –
• Define ventilation needs • Equipment sizing • Develop project schedule • Payback analysis • ASHRAE Weather data • RenewAire ERV Product
data – Submittals – Guide specs – Drawings (Revit, PDF, 3D,
DWG)
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