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Home , Blower door, Stack effect

VAPOR INTRUSION: HOW A BUILDING WORKS AND BREATHS 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 . . 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.

2 Goals for Today

1. Understand how buildings are working 2. What may 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 air movement.

3 At what pressures do our buildings function?

. tests and Corp of Engineers testing 75 Pascals. . Ductwork and ventilation system 1”-2” water column (249-498 pascals)

4 What are the pressure equivalents?

. 1 atmosphere . 2.96077 e-5 atmosphere . 14.69 psi . .000435 psi . 2116 psf . .06 psf . 406.79 inches of water column . .012 inches of water column

. 101,325 Pa . 3 Pa . 29.99 “ Hg. Barometric pressure

5 What happens in a building

. . . Mechanical ventilation . Static Pressure . Natural Wind pressure . Adjacent spaces . Fresh air intakes (leakage and powered) . Recent building control innovations . Buoyancy

6 Building Ventilation Design

. 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 . Energy issues have changed that. . Office commercial 6-10 cfm/person

. For tight houses .5-.41 ACH Westminster Palace venting . For loose insulated homes 1.1-1.47 ACH

7 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 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

8 Convection

. Warm air rises, cold air falls

9 10 Stack Effect

. 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 on the 52nd floor . Moves from higher to lower negative pressure.

11 Mechanical ventilation

. Air moves by the difference in pressure . forced “push” or “pull” . Plenum spaces versus full ducting . Think about the Metrodome. Air pressure is only about 0.04-.4 psi (275-2757 Pa) . Air balancing is a vital requirement. . The in and the out need to be about equal-balanced system . Try blowing or sucking air out of a pop bottle

12 Static pressure differential

. Pressure in ducts is typically measured in inches of water column . Different zones require different pressure

13 Natural wind pressure

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

14 Building Air Leakage Case Study

Buildings: . Two – 3 story barracks buildings . Steel frame construction . Composite concrete decks . Metal studs/exterior sheathing /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 Ft Leonard Wood Barracks Building . Pressure boundary: total area of floor slab, Air Leakage Testing exterior walls & roof . Allowable CFM: 25% of pressure boundary area . Passing grade: 0.25cfm/sq ft @75 Pa (0.3 inches

H2O)

15 Building Air Leakage Building Air Leakage

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

16 Building Air Leakage

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

17 Adjacent spaces

. 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”)

18 Fresh air intake

. 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

19 Building Control system innovations

. LEED monitoring . Low level conditioning . Occupied versus unoccupied modes . CO2 Sensors . Mixed return air or air exchange systems and heat wheels . Breathable Buildings

20 Buoyancy

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

21 Vapor prevention

. 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

Benzene H + C

22 23 Slab on grade and foundations

. 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

24 EPA moisture control

25 PNC Breathable Building in Pittsburgh. Worlds Greenest Building

. Incorporates Convection, stack effect, and natural conditions

. This allows the building to operate with no mechanical system 45% of the time.

https://youtu.be/z8ScZsOBB7k

26 Underground garages

. Make up air and exhaust

27 Radon and passive systems

28 What can get in the way?

. 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)

29 Conclusions

. There are many effects taking place on 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 vapor mitigation system needs to be designed 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.

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