Our presentation will strengthen your knowledge on building sciences with a focus on ventilation systems, design and operation that impacts the environmental vapor potential in a building.   Topics include: -Understanding how building air movement works -What can effect the movement of vapor through a building  -How air moves through a building  -Considerations when designing ventilation and vapor mitigation systems -Different forces that affect air movement Please, contact Steve Flaten at Slfaten@braunintertec.com for more information or questions.

1. VAPOR INTRUSION:
HOW A BUILDING WORKS AND BREATHS

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The “Breathing Building”
 The top five floors of this seven-story
structure are covered in 734 gold, copper and
bronze-colored steel plates that can be raised
or lowered via 82 computerized motors.
 The plates function as a second skin for the
building, increasing its ability to permit
natural ventilation and lowering energy
consumption by cutting down on the use of
air conditioning.
 The plates are peppered with micro-holes to
allow visibility from within. Geox occupies the
ground and first two floors, while the
remaining four floors house non-retail
tenants.

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1. Understand how buildings are working
2. What can effect movement of vapor through a building
3. Understand how subtle the air movement can be
through a building
4. What are the different forces that affect the air
movement.
Goals for Today

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 Blower door tests and COE testing 75 Pa.
 Ductwork and ventilation system 1”-2” water column
At what pressures do our buildings
function?

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 1 atmosphere
 14.69 psi
 2116 psf
 406.79 inches of water
column
 101325 Pa
 2.96077 e-5 atmosphere
 .000435 psi
 .06 psf
 .012 inches of water
column
 3 Pa
What are the pressure equivalents?

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 Convection
 Stack Effect
 Mechanical ventilation
 Static Pressure
 Natural Wind pressure
 Adjacent spaces
 Fresh air intakes (leakage and powered)
 Recent building control innovations
 Buoyancy
What happens in a building

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 Building codes require:
 Living areas - 0.35 air changes /hr or > 15
cfm/person
 Garages-100 cfm/car
 Enclosed parking .05 cfm/sf AND capable of
1.5 cfm/sf
 Commercial Buildings – 4-10 air changes /hr
 ASHRAE-ventilation design is anticipated
to be thru infiltration. Energy issues have
changed that.
 For tight houses .5-.41 ACH
 For loose insulated homes 1.1-1.47 ACH
What do we do for Ventilation?
Westminster Palace venting

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Building Occupancy
Differs with how the building is used:
 Health care
 Higher air volumes
 Required to be full ducted return
 Office space
 Could be return plenum ceiling
 Apartments and hotels
 Usually parking below and furnace inside
 Does not have make up air system except in corridor
 Make up air is via opening a window
 Often referred to as Magic Pak or Ptac

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 Warm air rises, cold air falls
Convection

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 Areas like stairwells, atriums
and elevator shafts show
the volume of air that is
moving vertically through
the building.
 E.g. IDS Building, 52nd floor.
Difficult to open the door to
the mechanical room on the
52nd floor
Stack Effect

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 Air moves by the difference in
pressure
 Fan forced “push” or “pull
 Plenum spaces versus full ducting
 Think about the Metrodome. Air
pressure is only about 0.04-.4 psi
 Air balancing is a vital requirement.
 The in and the out need to be about
equal
 Try blowing or sucking air out of a
pop bottle
Mechanical ventilation

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 Air in ducts is measured in inches of water
column
 Different zones require
Static pressure differential

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 Wind air pressure can be in the 20#+ psf (.13 psi)
Natural wind pressure

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Building Air Leakage Case Study
Buildings:
 Two – 3 story barracks buildings
 Steel frame construction
 Composite concrete decks
 Metal studs/exterior sheathing air barrier/rigid
insulation/brick
 PTO roof membrane over rigid Insulation
Test Requirements:
 USACE Protocol for TESTING Air Leakage
in Occupied Buildings
 ASTM E779 – Standard Test Method for
Measuring Air Leakage Rate by Fan Pressurization
 Pressure boundary: total area of floor slab,
exterior walls & roof
 Allowable CFM: 25% of pressure boundary area
 Passing grade: 0.25cfm/sq ft @75 Pa (0.3 inches
H2O)
Ft Leonard Wood Barracks Building
Air Leakage Testing

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Air Pressure inside a building on a calm day
Depressurization Test Cycle -75Pa to -25Pa with Bias pressure readings pre & post test
Building Air Leakage
Building Air Leakage

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Air pressure inside the same building on a windy day
Depressurization Test Cycle -75Pa to -25Pa with Bias pressure readings pre & post test
Building Air Leakage

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 Balancing Issues
 Air transfer in Roof Deck flutes between building
tenants
 Air transfer at material joints
 Air barrier installation (not “weather barrier” or
“vapor retarder”)
Adjacent spaces

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 Normal fan powered units pass a 6-10% fresh air or # cfm per
occupant.
 Fin tube radiation has no fresh air unless a separate system is
provided.
 PTAC and Magic Pak units have a small amount of fresh air, but
unit must be running and balanced with the exhaust fan
 Pressurization
 Supply air-air loss=>return air + fresh air. Normally building is slightly
positive in pressure.
 Apartments and condos
 Corridor has make up air, but stopped from getting to the units due
to fire gasketing
 Opening locations
Fresh air intake

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 LEED monitoring
 Low level conditioning
 Occupied versus unoccupied modes
 CO2 Sensors
 Mixed return air or air exchange systems and
heat wheels
 Breathable Buildings
Building Control system innovations

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 Warm air makes a difference
 Chemicals also make a difference.
Buoyancy

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 Consider particle/molecular size- “Coffee Filter”
 Water proofing versus vapor retarding
 Think of Gore-Tex
 Vapor passes through
 Water beads up
 Issue is really molecule size
 Water liquid 90 molecules in size
 Water vapor 2 molecules in size
 If vapor is larger than water it will not go through normally
Vapor prevention

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 Negative pressure zone under floor
 Membrane selection and sealing
 Materials
 Concrete block is porous and will allow air/smoke/vapor
through it
 Concrete block can also transport air vertically and up into the
second floor
 Vapor retarder-
 Quality material, not lumber yard poly
 Virgin polyethylene. Stego, Raven etc.
 Exterior wall waterproofing
Slab on grade and foundations

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EPA moisture control

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PNC Breathable Building in Pittsburgh.
Worlds Greenest Building
https://youtu.be/z8ScZsOBB7k
 Incorporates Convection, stack
effect, and natural conditions
 This allows the building to
operate with no mechanical
system 45% of the time.

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 Make up air and exhaust
Underground garages

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Radon and passive systems

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 There are many effects taking place in the building and they
vary by season.
 Not all buildings are the same. The ventilation systems,
design and operation all impact the vapor potential.
 Nature affects the way buildings operate.
 The mitigation system needs to work with the mechanical
system, if possible.
 The engineer needs to deal with all of these different issues
in the design of the building and systems.
 Remember there is a potential for the buildings to operate
outside of the norm. Mainly due to human interference.
Conclusions

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 Weather
 Other building systems or openings for fresh air
 Insulation systems that want to add a porous material to the
perimeter of the building.
 Making a connection between all the membranes through
structure.
 Future occupants
 Trying to save on the costs of energy, modifying the building by
disabling or shutting off systems.
 Tenant changes (pizza ovens; high volume exhaust etc)
What can get in the way?

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