1. Implementing Demand Controlled Ventilation to Meet ASHRAE Standard 62.1 - 2010 By Klas C. Haglid, P.E., R.A., CEM 1

2. Klas C. Haglid, P.E., R.A., CEM - Bio ASHRAE Distinguished Service Award 2011 ASHRAE Handbook, HVAC Applications and Management, Chapter 37,– Author, Klas C. Haglid P.E. R.A. ASHRAE Standard 189.1, Corresponding Member GPC 32P - Sustainable, High Performance Operations & Maintenance, Voting Member, Contributing, Co-Author Technical Committee 5.5 - Air-To-Air Energy Recovery, Handbook Subcommittee Chairman, Past Chairman Technical Committee 7.6 - System Energy Utilization, Voting Member Technical Committee 7.8 - Owning and Operating Costs of Commercial Buildings, Past Chairman ASHRAE Standard 84-1991R, Voting Member Reviewed draft of ASHRAE Standard 84-1991R and provided engineering details for efficiency calculations. 2

3. Challenge Complying with ASHRAE Std. 62.1-2010 to improve IAQ while increasing energy efficiency ASHRAE Std. 90.1 can be accomplished with: – Displacement Ventilation – Demand Controlled Ventilation – Energy Recovery Ventilator – Variable Speed Drives 3

4. ASHRAE Std. 62.1-2010 Ventilation for Acceptable Indoor Air Quality – How to determine minimum prescriptive ventilation rates – How to use Demand Side Ventilation to meet ASHRAE Standard 62.1-2010 4

5. Definitions “acceptable indoor air quality: air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.” –ASHRAE Standard 62.1-2010 pg. 3 5

6. 6.1.1 Ventilation Rate Procedure The following procedure for determining the minimum prescriptive ventilation rates can be used on any zone type. 6.1.1 Takes into consideration: – Space type – Number of Occupants – Floor Area – Typical contaminant sources and source strength 6

7. Ventilation Rate Procedure - Breathing Zone Outdoor Airflow V bz = R p P z + R a A z where: A z = zone floor area P z = zone population R p = outdoor airflow rate required per person as determined from Table 6-1*. R a = outdoor airflow rate required per unit area as determined from Table 6-1*. *Table 6-1 from ASHRAE Standard 62.1-2010 7

8. Office Example V bz = (5x12) + (.06 x 1500) = 60 + 90 = 150 cfm What is the prescriptive design for outdoor air (cfm) of a 1500 square foot office with 12 occupants? Eq 6-1 : V bz = R p P z + R a A z Design inputs for office space: Pz = 12 people Az = 1,500 square feet of floor area 8

9. School Example V bz = (10 x 30) + (.12 x 1100) = 300 + 132 = 432 cfm What is the prescriptive design for outdoor air (cfm) of a 1100 square foot classroom with 30 students? Eq 6-1 : V bz = R p P z + R a A z From Table 6-1: R p = 10 cfm/person R a = 0.12 cfm/ft 2 Design inputs from school classroom project for ventilation: P z = 30 people A z = 1100 square feet 9

10. General Manufacturing Example (Excludes Heavy Industrial and processes using chemicals) V bz = (10 x 20) + (.18 x 50000) = 200 + 9,000= 9,200 cfm What is the prescriptive design for outdoor air (cfm) of a 50,000 square foot coat hanger production facility with 20 machinists? Eq 6-1 : V bz = R p P z + R a A z From Table 6-1: R p = 10 cfm/person R a = 0.18 cfm/ft 2 Production facility input data: P z = 20 people A z = 50,000 square feet of floor area Notice the Area outdoor air rate (Ra) increased for a manufacturing facility. Increase 10

11. Ventilation Rate Procedure – Zone Outdoor Airflow V oz = V bz /E z (E z ) The zone air distribution effectiveness shall be determined using ASHRAE Std. 62.1-2010, Table 6-2. (Partial Table) 11

12. Methods of Providing Outdoor Air to Zone Dilution Ventilation Displacement Ventilation 12

13. Dilution Ventilation It’s important to design ventilation system to have maximum air distribution. This will help eliminate dead space and short circuiting of air flow UV is not properly distributing air across classroom 13

14. Dilution Ventilation Typical in U.S. construction Outdoor air is brought into space and dilutes contaminant concentrations in the space. Adequate air mixing 14

15. Displacement Ventilation Diagram shows good air circulation providing fresh air on one end of room and exhaust pulling air out on the other end to maximize removing contaminant concentrations 15

16. Displacement Ventilation (DV) Uses natural convection to provide “Buoyancy- assisted forced ventilation” Effectively removes contaminants from people and objects locally ASHRAE Std. 62.1-2010 Table 6-2 recognizes DV to be 1.2 times more effective than traditional dilution ventilation Some applications measured DV to be 2 to 2.5 more effective than traditional dilution ventilation 16

17. Displacement Ventilation Using displacement ventilation and then measuring air quality of the space is an effective way to improve IAQ Often times, balancing airflow according to how effective the displacement ventilation system is can reduce required airflow by 50% – This saves energy and reduces latent loads – Can be achieved with Variable Speed Drives (VSD) 17

18. Demand Controlled Ventilation (DCV) “any means by which the breathing zone outdoor airflow (Vbz) can be varied to the occupied space or spaces based on the actual or estimated number of occupants and/or ventilation requirements of the occupied zone.” – ASHRAE Std. 62.1-2010 pg. 4 18

19. Example of DCV Methods ERV CO2 Sensor comes on over 700 ppm and turns off under 600 ppm SOA EA People Fan Relays 19 ERV- Energy Recovery Ventilator EA- Exhaust Air SOA- Supply Outside Air

20. DCV CO 2 concentrations in outdoor air generally range from 300 to 500 ppm ASHRAE std. 62.1 2007 and 2010 recognize 700 ppm of CO 2 above outdoor ambient levels or 1000 to 1200 ppm to be acceptable air quality for an indoor space. Reference page 37 of Appendix C Displacement Ventilation with CO 2 Demand Controlled Ventilation properly engineered and installed will keep CO 2 levels well below 1000 ppm DCV can reduce runtime from 168 hours per week to 30 hours per week for a classroom. That is an 82% reduction in runtime. 20

21. Summary of Ventilation Rates Determine prescriptive design ventilation rate for zone by using Ventilation Rate Procedure Determine Method of Ventilation – Dilution – Displacement – up to 2.5 times more effective Choose appropriate method to control the ventilation system and monitor the contaminants of concern – CO2 sensor – VSD – Variable Speed Drive to reduce fan speed to balance and optimize ERV efficiency 21

22. Not All ERVs Are the Same ERV Features to Compare: – Airflow Arrangement Thermal Effectiveness – Pressure Drop – Fan Efficiency – Maintenance – Sound Levels 22

23. Heat Exchanger Airflow Arrangement ASHRAE states: Counter-flow heat exchangers are theoretically capable of achieving 100% Sensible Effectiveness* Parallel Flow heat exchangers: 50% (Max) Cross-flow heat exchangers and Enthalpy Wheels: 50-75% (Max) *Note: Source: 2012 ASHRAE Handbook – HVAC Systems and Equipment, Chapter 26: Air-to-Air Energy Recovery Equipment. 23

24. Fan Affinity Laws 24

25. Example What is the percent difference in BHP required to run a ventilation system if alternative 2 has a 50% increase in static pressure from alternative 1? Altenative 1 Conditions: – CFM = 8,000 – SP = 1” in wg – BHP = 5 – RPM = 1000 25

26. Example Continued 26

27. High Efficiency Fans Typical fan efficiency can range from 5 to 10 W/cfm A high efficiency fan can be expected to be approximately 0.2 W/cfm The EER of an ERV is formulated by the BTUs recovered divided by the watts of power consumed from the fan energy BTUs Recovered Watts of Fan Power EER = 27

28. Efficiency is Essential Combining premium Efficiency fans with High efficiency ERVs and a low static pressure system can yield great energy savings Typical ERV has an EER of around 10. High efficiency ERV can be well above 120. 28

29. Maintenance Costs are Essential There’s more to a product than its initial costs and efficiency – Maintenance costs can make or break your bottom line Look for : Corrosion resistant equipment Minimal moving parts Low static pressure Use appropriate filter type for equipment 29

30. Tools to Meet ASHRAE Std. 62.1 and Improve IAQ While Increasing Energy Efficiency, ASHRAE Std. 90.1 Displacement Ventilation Demand Controlled Ventilation – CO2 controls or other contaminant monitoring sensors ERV – Counter flow heat exchanger – Low Pressure Drops – High efficiency fans Variable Speed Drives – Air balancing – Better control 30