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Ventilation in Multi-Family Buildings - Summer Camp 2015

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Corridor pressurization based ventilation systems are often ineffective and inefficient. Find out why in this presentation given at the Nineteenth Annual Westford Symposium on Building Science (Summer Camp).

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Ventilation in Multi-Family Buildings - Summer Camp 2015

  1. 1. 1 of 56 Ventilation in Multi-Family Buildings 19TH ANNUAL WESTFORD SYMPOSIUM ON BUILDING SCIENCE (SUMMER CAMP) LORNE RICKETTS, MASC BUILDING SCIENCE ENGINEER, RDH BUILDING ENGINEERING LTD.
  2. 2. 2 of 56 Intro I’m Not Going to Talk About This
  3. 3. 3 of 56 Intro I’m Not Going to Talk About This Either
  4. 4. 4 of 56 Intro Airflow in Multi-Family Buildings as a System
  5. 5. 5 of 56 Outline  A (little) Bit of Science  Some Engineering  Corridor Pressurization Case Study › What it Is › Measuring It › Finding Out Why › What it Means  A Bit of Context
  6. 6. 6 of 56 A (little) Bit of Science
  7. 7. 7 of 56 A Bit of Science – Driving Forces 3 Driving Forces create pressure differences that drive airflow: Stack Effect, Wind, and Mechanical Ventilation
  8. 8. 8 of 56 Stack effect caused by the density difference between inside air and outside air due to temperature difference A Bit of Science – Stack Effect
  9. 9. 9 of 56 Wind creates pressures on the surface of a building and tends to drive airflow from windward to leeward A Bit of Science – Wind
  10. 10. 10 of 56 A Bit of Science – Driving Forces
  11. 11. 11 of 56 A Bit of Science - Airtightness Resistance to airflow provided by airtightness of building elements such as walls, windows, doors, etc.
  12. 12. 12 of 56 A Bit of Science  Buildings are complicated with many zones separated by many pressure boundaries  Convenient to develop a model to help understand the complex relationships
  13. 13. 13 of 56 Interstitial Spaces A Bit of Science  Many connected interior spaces…
  14. 14. 14 of 56 A Bit of Science  It’s complicated…
  15. 15. 15 of 56 Corridor Pressurization Ventilation Systems  A Case Study
  16. 16. 16 of 56 Background  Most apartments/condos (multi-family buildings) are ventilated using pressurized corridor systems  Decades of anecdotal evidence indicates that this system likely does not work very well  Still most common system  Particularly relevant now, as newer more airtight buildings have less tolerance for poorly performing ventilation systems  Less infiltration and exfiltration to supplement ventilation
  17. 17. 17 of 56  Design Intent  Provide ventilation air to all zones  Control flow of air contaminates between zones  How  Provides air to corridors directly via a vertical shaft which pressurizes the corridor  Corridor pressurization forces air into suites via intentional gaps under the entrance doors Pressurized Corridor Ventilation System Background
  18. 18. 18 of 56 Background Case Study Building  13-story multi-family building in Vancouver, Canada with 37 residential suites  Constructed 1986  Enclosure renewal 2012  Below grade parking garage located under the building  Ventilated using pressurized corridor ventilation system by a single make-up air unit Overall, is typical of high-rise multi-family buildings
  19. 19. 19 of 56 Measured Ventilation Rates Perfluorocarbon (PFT) Testing Two component system:  PFT Sources (7 distinct types)  Capillary absorption tube samplers (CATS)  Sources release distinct PFT tracer gasses in different zones and use CATS to sample the concentrations Sources CATS
  20. 20. 20 of 56 Measured Ventilation Rates  Order of magnitude variation in the ventilation rates  Significantly higher rates for upper suites than lower suites  Most suites under-ventilated or over-ventilated 10 28 11 25 48 70 58 154 193 121 0 20 40 60 80 100 120 140 160 180 200 220 Suite 202 Suite 301 Suite 302 Suite 303 Suite 402 Suite 1003 Suite 1101 Suite 1102 Suite 1103 Suite 1203 Airflow[cfm] Total Airflow Into Suites from All Sources Lower Suites Upper Suites ASHRAE 62.1-2010 ≈ 85 cfm per suite Waste of Energy Indoor Air Quality Issues
  21. 21. 21 of 56 PMCP Released in MAU Measured Ventilation Rates
  22. 22. 22 of 56 Measured CO₂ Concentrations  Carbon dioxide concentrations were monitored as an indicator of indoor air quality (IAQ)  Significantly higher concentrations in the lower suites Floor 02 Suites Floor 04 Suites Floor 11 Suites Floor 03 Suites Floor 10 Suites Floor 12 Suites Make-up Air Unit
  23. 23. 23 of 56 Measured CO2 Concentrations (Fisk et al, 2013)
  24. 24. 24 of 56 Infiltration from Parking Garage PDCB Released in Parking Garage
  25. 25. 25 of 56  Summary:  Over ventilation and under ventilation of most suites  Higher ventilation rates in upper suites than lower suites  Better indoor air quality in upper suites than lower suites Why is this happening? Measured Ventilation Rates
  26. 26. 26 of 56 Cause of Ventilation Rates - MAU Maybe the MAU isn’t working correctly?  Powered flow hood used to measure intake flow rate  MAU airflow approximately the same as design flow rate (3,300 cfm)
  27. 27. 27 of 56 0 2 4 6 8 10 12 14 0 50 100 150 200 250 300 350 FloorNumber Flow Rate [cfm] MAU Supply to Corridors Pre-Retrofit (70°F) Post-Retrofit (43°F) Post-Retrofit (61°F) Pre-Retrofit (70°F) Total = 1257 cfm Post-Retrofit (43°F) Total = 1184 cfm Post-Retrofit (61°F) Total = 1229 cfm Fire Damper noted to be closed on Floors 4, 8, & 12. Cause of Ventilation Rates – Duct Leakage Maybe the ventilation air isn’t reaching the corridors?  Only 40% of intake flow reaches the corridors directly
  28. 28. 28 of 56 Cause of Ventilation Rates – Corridor Leakage Maybe the air isn’t reaching the suites from the corridors?  Airtightness tested corridors and found significant flow paths other than to the suites through the suite entrance doors.
  29. 29. 29 of 56 Cause of Ventilation Rates – Corridor Leakage Maybe the air isn’t reaching the suites from the corridors?  Airtightness tested corridors and found significant flow paths other than to the suites through the suite entrance doors. 335 cfm, 10% 945 cfm, 29% 1,297 cfm, 41% 627 cfm, 20%
  30. 30. 30 of 56  Theoretically, only 8% of intended ventilation actually goes where it is supposed to! Waste of ventilation air, and the energy needed to move and condition it. Cause of Ventilation Rates – Leakage  If only 40% of the flow rate reaches the corridors And, only 20% of that air reaches the suites… Leakage of air along ventilation flow path is a major issue. 𝟒𝟎% × 𝟐𝟎% = 𝟖%
  31. 31. 31 of 56 Cause of Ventilation Rates – Pressure Differences Maybe pressure differences are an important factor?  Pressure differences were monitored with a focus on an upper floor and a lower floor (Floors 11 & 3)  Assessed relationship of stack effect and wind to ventilation system performance
  32. 32. 32 of 56 Cause of Ventilation Rates – Pressure Differences  Mechanical ventilation system creates pressure of 5 to 10 Pa -20 -15 -10 -5 0 5 10 15 20 Feb 8 6:00 Feb 8 8:00 Feb 8 10:00 Feb 8 12:00 Feb 8 14:00 Feb 8 16:00 Feb 8 18:00 PressureDifference[Pa] Average Corridor to Suite Pressure by Floor when MAU Off Floor 02 Floor 03 Floor 04 Floor 10 Floor 11 Floor 12 Measurement with MAU Off Measurement with MAU Recently Turned On Corridor-to-SuitePressureDifference[Pa] ≈10 Pa ≈5 Pa Corridor-to-Suite Pressure Difference
  33. 33. 33 of 56 Cause of Ventilation Rates – Pressure Differences  Pressures created by stack effect found to be of similar magnitude (10 to 15 Pa) as mechanical pressures -5 0 5 10 15 20 25 -10 -5 0 5 10 15 20 ExteriorTemperature[°C] Corridor-to-SuitePressureDifference[Pa] Average Suite to Corridor Pressures by Floor and Exterior Temperature - 24 Hour Moving Average Floor 02 Floor 03 Floor 04 Floor 10 Floor 11 Floor 12 Exterior Temperature [°C] -5 0 5 10 15 20 25 -10 -5 0 5 10 15 20 ExteriorTemperature[°C] Corridor-to-SuitePressureDifference[Pa] Average Suite to Corridor Pressures by Floor and Exterior Temperature - 24 Hour Moving Average Floor 02 Floor 03 Floor 04 Floor 10 Floor 11 Floor 12 Exterior Temperature [°C] -5 0 5 10 15 20 25 -10 -5 0 5 10 15 20 ExteriorTemperature[°C] Corridor-to-SuitePressureDifference[Pa] Average Suite to Corridor Pressures by Floor and Exterior Temperature - 24 Hour Moving Average Floor 02 Floor 03 Floor 04 Floor 10 Floor 11 Floor 12 Exterior Temperature [°C] Corridor-to-Suite Pressure Difference 10 – 15 Pa 23 32 41 50 59 68 77 ExteriorTemperature[°F]
  34. 34. 34 of 56 Cause of Ventilation Rates – Pressure Differences  Stack effect pressures found to distribute 69% at corridor-to-suite boundary and only 9% at exterior enclosure  Stack effect pressure acts primarily in the same location as mechanical pressures intended to provide ventilation and control contaminate flow
  35. 35. 35 of 56 Cause of Ventilation Rates – Enclosure Retrofit Before Maybe the enclosure retrofit negatively impacted the ventilation system performance? After
  36. 36. 36 of 56 Enclosure Retrofit - After Installed More Insulative Windows R-1.8 upgrade to R-5 Added Insulation to Exterior Walls R-4 upgraded to R-16 Improved Air-Sealing Reduced air leakage by 53% 63% Space Heat Savings Improvements:  Quieter  More comfortable  Reduced electricity and gas consumption
  37. 37. 37 of 56 Cause of Ventilation Rates – Enclosure Retrofit  Overall measured average enclosure airtightness improvement of approximately 53% 215 cfm, 16% 204 cfm, 15% 209 cfm, 15% 58 cfm, 4% 318 cfm, 24% 354 cfm, 26% Suites Above and Below Corridor Suite Entrance Door Suites to Left and Right Exterior Enclosure - Post-Retrofit Exterior Enclosure Airtightness Improvement Airflow Rates at 75 Pa
  38. 38. 38 of 56 Cause of Ventilation Rates – Enclosure Retrofit Average Operable Window
  39. 39. 39 of 56 Extension of Study Findings  Vancouver is a relatively moderate climate  Should consider other climates  Case study building is 13 stories  Should consider different building heights
  40. 40. 40 of 56 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 40 m Tall Building in Miami15 Story Tall Building in Miami 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 40 m Tall Building in Vancouver15 Story Tall Building in Vancouver 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 40 m Tall Building in New York15 Story Tall Building in New York15 Story Tall Building in Toronto 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 40 m Tall Building in Toronto 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 40 m Tall Building in Fairbanks15 Story Tall Building in Fairbanks Extension of Study Findings Wind Stack Effect Mechanical (10 Pa)  Climate
  41. 41. 41 of 56  Building Height Extension of Study Findings Wind Stack Effect Mechanical (10 Pa) 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 10 Story Building in New York10 Story Tall Building in New York 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 20 Story Building in New York20 Story Tall Building in New York 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 30 Story Building in New York30 Story Tall Building in New York 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 40 Story Building in New York40 Story Tall Building in New York 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec PercentageofDrivingForcePressure Daily Average Distribution of Pressure Difference due to Driving Forces for a 50 Story Building in New York50 Story Tall Building in New York
  42. 42. 42 of 56 0% 10% 20% 30% 40% 50% 60% 70% Stack Effect Wind Mechanical (10 Pa) PercentageofDrivingForcePressure Average Proportions of Driving Force Pressure Differences - New York 10 Storys 20 Storys 30 Storys 40 Storys 50 Storys Building Height Extension of Study Findings  Stack effect is more significant in taller buildings  Proportion of wind pressures remains relatively the same  Relative magnitude of mechanical pressures decreases as height increases
  43. 43. 43 of 56 0% 10% 20% 30% 40% 50% 60% 70% Stack Effect Wind Mechanical (10 Pa) PercentageofDrivingForcePressure Average Proportions of Driving Force Pressure Differences - 15 Story Building Miami Houston Los Angeles New York Vancouver Toronto Calgary Fairbanks Extension of Study Findings  Stack effect more significant in cold climates  Wind highly variable, but typically more significant in warm climates
  44. 44. 44 of 56 Comparison of Driving Forces  Since all of the pressure differences created by the driving forces (stack effect, wind, & mechanical systems) are of similar magnitude, it is possible that any one could dominate  This is exaggerated for buildings located in more extreme climates than Vancouver Ventilation system can not practically overwhelm nature.
  45. 45. 45 of 56 What it Means  Corridor pressurization does not provide intended ventilation rates to a large number of suites  Some significantly over ventilated while others significantly under ventilated  Significant leakage along the ventilation air flow path from the duct and the corridor (wasted ventilation)  Uncontrolled airflow wastes energy and provides poor ventilation  Stack effect and wind pressures are often similar or greater than mechanically-induced pressures  Ventilation system can not practically overwhelm nature
  46. 46. 46 of 56 What it Means  Ventilation air should be directly supplied to suites to limit the potential of loss along the flow path and of the system being overwhelmed by stack effect and wind  The exterior enclosure should be airtight, and suites and vertical shafts should be compartmentalized (airtight) to limit the impact of wind and stack effect on ventilation
  47. 47. 47 of 56 A Bit of Context
  48. 48. 48 of 56 A Bit of Context - Efficiency How can we talk about equipment efficiency when system efficiency is 8%?
  49. 49. 49 of 56 A Bit of Context – Current Codes/Standards  International Mechanical Code 2012  601.2 Air movement in egress elements. Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.  Something similar in code since at least 1996 Code Adopted http://www.iccsafe.org/about-icc/overview/international-code-adoptions/
  50. 50. 50 of 56 A Bit of Context – Current Codes/Standards  CaGBC LEED Credit EQp1 Interpretation (#1126)  Supply of ventilation air from corridor is unlikely to meet the referenced ASHRAE 62.1 requirements for distribution  Likely to conflict with ETS and fire separation
  51. 51. 51 of 56 A Bit of Context – How much air? How do we set a ventilation rate if we don’t know what we are going to get? ? ? ?? ? ?
  52. 52. 52 of 56 A Bit of Context - Are All Systems Equal?  BSC Standard 01 takes a first crack at adjusting ventilation rate based on system effectiveness System Type Distributed Not Distributed Balanced or Mixed 0.75 1.0 Not Balance or Mixed 1.0 1.25
  53. 53. 53 of 56 One more thing…
  54. 54. 54 of 56 Current Situation…
  55. 55. 55 of 56 The Plan i
  56. 56. 56 of 56  rdh.com Questions? LORNE RICKETTS MASC, EIT LRICKETTS@RDH.COM

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