Energy Efficient
Outside Air
Brian Guffey
Dallas, TX
Why do we ventilate buildings?
• To dilute potentially dangerous
contaminants
• Moisture control
• Occupant comfort and health
Why do we ventilate buildings?
• To dilute potentially dangerous
contaminants:
• Formaldehyde and other chemicals
• Volatile organic compounds from workplace cleansers,
solvents, pesticides, and disinfectants
• Fumes and other chemicals from construction materials,
glues, fiberglass, paints, etc.
• Dust mites from carpets, fabrics, and foam chair
cushions
Why do we ventilate buildings?
• Moisture control:
• Prevent insufficient or excess humidity levels which can
increase growth of substances harmful to occupants
• Molds
• fungi
• bacteria
• viruses
• Prevent structural damage from insufficient or excessive
humidity
Why do we ventilate buildings?
• Occupant comfort and health
• Insufficient ventilation can cause uncomfortable
humidity levels, buildup of odors and other
contaminants
• Better comfort = fewer occupant complaints
• Better health = higher occupant productivity
• Better comfort and health = higher space value $$$
Three basic ventilation strategies
• Natural Ventilation
• Spot Ventilation
• Whole System Ventilation
Three basic ventilation strategies
• Natural Ventilation
• Uncontrolled air movement in and out of
buildings
• Either through operable windows or through the
other leak sources in every building
• Inexpensive but unpredictable and
uncontrollable
• May lead to insufficient pollutant removal
• May make buildings less comfortable and more
expensive to heat and cool.
Three basic ventilation strategies
• Spot Ventilation
• Can improve the effectiveness of natural
ventilation by removing contaminants or
moisture at its source.
• Includes the use of localized exhaust fans, such
as in kitchens and bathrooms.
• Can be used in place of or in combination with
whole system ventilation.
Three basic ventilation strategies
• Whole System Ventilation
• Typically motivated by concerns that natural ventilation
won’t provide adequate air quality with or without spot
ventilation.
• More and more common over the last 40 years because
of changing codes and construction methods.
Three basic ventilation strategies
• Whole system ventilation provides:
• Control of air movement in and out of buildings.
• Control of air quality and moisture control in buildings.
• Improved occupant comfort, health, and productivity.
How to provide whole system ventilation?
• Heat and Vent Only
• Mixed Air Packaged Equipment
• Mixed Air Central System Equipment
• Dedicated Outside Air System (DOAS)
How to provide whole system ventilation?
• Heat and Vent Only
• Generally used for industrial or storage spaces
• Typical for kitchen make-up air
• Lowest cost ventilation
• Freeze protection type heating
• No cooling or dehumidification control
How to provide whole system ventilation?
• Mixed Air Packaged Equipment
• Typical for rented commercial spaces, some
educational facilities, small and medium sized
office buildings, some campus operations
• Typically fixed ventilation percentages during
heating and cooling operation
• Decent overall space conditioning
• Lowest first cost, highest operating cost
• Can lead to problem spaces where load or load
balance exceeds unit capacity
How to provide whole system ventilation?
• Mixed Air Central System Equipment
• Similar to mixed air packaged equipment
• Typical in most central system spaces
• Uses heating and cooling capacity from central
heating and cooling equipment
• Better efficiency than packaged equipment
• Can limit energy efficiency operating strategies
of central equipment
• Can lead to excessive energy consumption due
to overcooling and excessive reheating
How to provide whole system ventilation?
• Dedicated Outside Air System (DOAS)
• A Dedicated Outdoor Air System (DOAS) is a
type of HVAC system where the ventilation air is
conditioned separately and may be delivered to
the space separately from the air conditioned to
treat the building and occupant load.
DOAS / Make Up Air Applications
• Commercial
• Institutional
• Municipal
• Industrial
• Process
• Basically any space where the entity buying the
equipment will expect to own the equipment throughout a
large portion if not all it’s service life.
Why use DOAS?
• 10% O/A: 35% of cooling load, 20% of heating load
• 30% O/A: 70% of cooling load, 45% of heating load
• Controllability
• Space temperature and humidity can be controlled separately
• Building load system can be sized and operated to meet more
consistent interior load
• Flexibility
• OAUs can be used for humidity control and freeze protection during
unoccupied operation
• Central system setpoints can be reset for energy savings without
affecting humidity control
• Cost Savings
• MAUs can be less expensive than a larger central system
• Energy recovery saves operating cost
0.4% Design conditions
MAU Cooling Design Conditions
New Orleans
Houston
Indianapolis Chicago
Il
Washington
Orlando FL
Richmond
New York
DFW
Pittsburgh
Vancouver Winnipeg Cleveland Kansas City
Return Air
San Francisco
Calgary
Palm Springs
Denver CO Phoenix
Las Vegas
Billings MT
Albuquerque
DOAS Heating and Cooling Choices
• Hot Water Heating Coil
• Chilled Water Coil
• Steam Heating Coil
• DX Cooling
• Electric Heater
• Energy Recovery
• Runaround Loop
• Heat Pipe
• Sensible or Latent Plate
• Latent Wheel
• Direct Fired Gas Heat
• In-direct Fired Gas
Heat
Energy Recovery / ERV
• Runaround Loop
• Heat Pipe
• Wrap-around Heat Pipe
• Latent Plate
• Latent or Total Energy Wheel
Glycol
Plate
Pipe
Wheel
Wraparound Heat Pipe
• Most efficient Neutral Air Cooling Supply
• 25% -35% Cooling Load Reduction – Precooling
provides reheat
Dual Heat Pipe Unit
• No Air Mixing from Exhaust
• Constant Neutral Air Unit
Heat Wheel / Heat Pipe Combination
• Maximum Energy Recovery
• 40 to 45% Cooling and Heating Load Reduction – Energy
Recovery – Constant Neutral Discharge – Minimal Heating
Required
What Can I Do Today?
• Know your system
• Know your controls
• Know how to control your system
• Clean and maintain equipment
What Can I Do Today?
• Know your system
• What heating and cooling equipment do you have?
• What is it supposed to be doing and when?
What Can I Do Today?
• Know your controls
• What is the equipment capable of?
• What is the building system capable of?
• How and how well does the building system
communicate with your equipment?
What Can I Do Today?
• Know how to control
• What is the system supposed to be doing?
• How well is it doing that?
• What flexibility does it have?
• What opportunities for savings are there?
• Who is responsible? Are they trained?
What Can I Do Today?
• Clean and maintain equipment
• Change air filters regularly
• Pressure drop or visual inspection
• Do other regular maintenance
Questions?