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Indoor Air Quality

Indoor Air Quality

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Indoor Air Quality

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  2. Learning Objectives Indoor air quality • By attending this session, participants will be able to: • Recognize about the factors affecting IAQ. • Describe the role moisture plays in IAQ. • Discuss moisture movement. • Formulate pollutant remediation techniques. • Examine the impact of occupant behavior on IAQ. • Describe the evolution of ventilation standards. • Describe the requirements of ASHRAE 62.2 2010.

  3. IAQ and Moisture Indoor air quality • Moisture and Mold • Stored Toxic Materials • Carbon Monoxide (CO) • Radon • Sewer Gas • Other Photo courtesy of The PA WTC

  4. Occupant Driven IAQ Sources Indoor air quality • Common household pollution sources • Pet dander • Volatile Organic Compounds (VOC’s) • Improperly stored solvent, paints, cleaners • General unhygienic conditions • Rodent or Insect Infestations • Making things worse • Tight house with a lack of ventilation • Uninformed occupants Photo courtesy of The US Department of Energy

  5. Sources of Water Vapor Indoor air quality Related to the building Related to occupant behavior

  6. Moisture Movement Indoor air quality Air flow Air molecules are blocked. Both water vapor and air molecules pass through. Water vapor molecules are passed. Diffusion Through Surface Convection Through Holes

  7. Permeance of Building Materials Indoor air quality Permeance of Building Materials Material placed on the warm side of a building surface to retard diffusion of water vapor is called a vapor barrier. Material intended to retard convection is called an air barrier. Material which accomplishes both is termed an air/vapor barrier. A material qualifies as a vapor barrier if its permeance is 1.0 perm or less.

  8. IAQ and Relative Humidity Indoor air quality Relative Humidity and Indoor Air Quality Relationships Decrease in bar width indicates decrease in effect

  9. What Determines IAQ? Indoor air quality Photos courtesy of The US Department of Energy

  10. Client Interview Indoor air quality Use the interview process to learn more about how the client uses their home as it relates to health and safety: • How many people live in the home? • Are there cold rooms? Hot rooms? • Do they use the fireplace or unvented space heaters? • Does anyone in the home have asthma or other illnesses? • Are headaches a chronic problem in the heating season? • Do they use their kitchen and bathroom exhaust fans? • Do they dry clothes or wood in the house? • Are there any unpleasant odors or burning sensations?

  11. Client Education Indoor air quality • Properly size central AC units. • Talk people out of using unvented heaters. • Don’t overcool the house in summer. • Don’t hang wet clothes in the house. • Don’t dry wood indoors. • Use kitchen and bath exhaust fans. • Enhance room circulation with fans to avoid cold spots.

  12. What WAP Can and Cannot Do Indoor air quality • Testing and abatement is not an allowable expense. (WPN 11-6 H&S Guidance) • Mold clean-up is not an allowable expense • Correcting moisture problems that may cause mold is allowable • Controlling surface temperatures with good insulation and air sealing practices • Venting dryers • Installing mechanical ventilation • Fixing minor drainage issues

  13. Pollutant Action Tree Indoor air quality • Source • Eliminate • Encapsulate • Dilute • Driving Force • Eliminate • Weaken • Path • Eliminate • Block Photo courtesy of The US Department of Energy

  14. Outside Air and IAQ Indoor air quality How much outside air do we need for good IAQ? How do we get it? WIND DIRECTION Exhaust Fan Wind Buoyancy Stack effect - warm air rising Mechanical Fans

  15. How has natural ventilation been calculated? Indoor air quality N-factor variables: • Geographic location • Building height • Building exposure • The n-factor for the house illustrated at right would be different if it was one story taller, or less shielded. The map shown below is the LBL Climate Zone Map used to determine the geographic variable.

  16. Why Isn’t the MVG Our Best Tool? Indoor air quality • A single-point blower door test will see these holes as identical! Photos courtesy of The US Department of Energy • The missing flue plug creates a stable-sized round hole with little air flow drag. • The matched board ceiling above has many feet of linear cracks that expand and contract depending on relative humidity (RH).

  17. Random Size & Distribution? Indoor air quality Neutral pressure plane

  18. AnImportant Corollary! Indoor air quality Based on single-story 1,500ft2house Chart courtesy of Paul Francisco

  19. ASHRAE 62.2-2010 What is the DOE Requirement Now? Indoor air quality A Wisconsin pilot study conducted in 2004 found that 78% of weatherized units required additional mechanical ventilation under 62.2, up from 47% using the previous ASHRAE standard, 62.1989. Average installed cost, including controls: $525 (2004-2005 prices).

  20. ASHRAE 62.2-2010 Indoor air quality Photos courtesy of The US Department of Energy

  21. ASHRAE 62.2-2010 Table Indoor air quality Table 4.1a: Minimum Ventilation Air Requirements, CFM, New Buildings1 45 1 ASHRAE 62.2-2010, p 4

  22. ASHRAE 62.2-2010 Formula Indoor air quality New or Existing Buildings2: • Assumes two occupants in master bedroom and one each in the other bedrooms. Over this density, increase ventilation by 7.5 cfm/person. • Whole building, intermittently operating ventilation may be used under some conditions for compliance. • Ventilation air must come directly from the outdoors. • Credit is allowed for envelope air leakage in some cases, based on ASHRAE 62.2 and 136. CFMfan= 0.01Afloor + 7.5(Numberbedroom+ 1) + (alternative compliance supplement) - (Infiltration credit) A = conditioned floor area; “the part of the building that is capable of being thermally conditioned for the comfort of occupants.” (ASHRAE 62.2, p.3) 2 Slide content from ASHRAE 62.2-2010

  23. Beyond Fan CFM Requirements Indoor air quality ASHRAE 62.2 2010 includes: • Spot ventilation requirements as mentioned. • Attached garages must be adequately sealed from living space to prevent migration of contaminants. • Clothes dryers must be vented to exterior. • All duct joints outside conditioned space must be sealed. • Sone rating requirements must be met. • Branch duct systems must have backdraft dampers. • Whole-home fan flow must be verified. • Continuous vs. intermittent fan specifications. Photo courtesy of The US Department of Energy

  24. Summary Indoor air quality • IAQ depends on the pollutant source strength and the air change rate. Elimination at the source is preferable to confinement, which is preferable to dilution. • Many pollutants are present in the average home: The air change rate is a function of inside to outside pressure difference, hole size, and hole location. • A higher air change rate equals better IAQ, and usually higher space conditioning costs. • ASHRAE 62.2 2010 guidelines are a required standard for new and existing buildings. • Occupant behavior can have a major impact on IAQ.