Sheridan Elementary School Analysis of Building ...

Sheridan Elementary School

Analysis of Building Ventilation Systems Minneapolis Public Schools

COVID 19 Analysis of Building Ventilation Systems Project Number: 20-472.00 August 20, 2020

COVID 19 Analysis of Building Ventilation Systems KFI Engineers • KFI – 20-472.00 Sheridan Elementary School Copyright 2020 KFI Engineers Minneapolis Public Schools 2

Title Page

Building Information Building Owner: Minneapolis Public Schools Building Name: Sheridan Elementary School Square Footage: 148,005 sf 1201 University Avenue NE Minneapolis, MN 55413

KFI Project Manager Information

Larry Justin, P.E. Senior Project Manager KFI Engineers 670 County Road B West St. Paul, MN 55113-4527 [email protected] 651-771-0880 - Office 651-771-0878 – Fax

Site Contacts

Curtis Hartog, P.E. Executive Director Capital Planning, Construction & Maintenance Minneapolis Public Schools 1250 West Broadway Avenue Minneapolis, MN 55411 [email protected] 612-668-0284 - Office 612-806-1274 – Fax

mailto:[email protected]

mailto:[email protected]


Table of Contents

Title Page ...........................................................................................................................................2

Table of Contents ...............................................................................................................................3

Glossary of Terms and Abbreviations ..................................................................................................4

Executive Summary ............................................................................................................................6

Disclaimer ........................................................................................................................................ 10

Introduction .................................................................................................................................... 11

ASHRAE Guidance ............................................................................................................................ 12

Building Assessment/Recommendations .......................................................................................... 13

HVAC System Filtration and Ventilation .................................................................................................. 13

Intake and Exhaust Separation ................................................................................................................ 28

Building Automation System ................................................................................................................... 28

Nurse and Office Area Air Flow ............................................................................................................... 29

Potential Isolation Areas ......................................................................................................................... 30

Appendices ...................................................................................................................................... 33

Appendix A – Matrix of Existing HVAC System ........................................................................................ 34

Appendix B – Building System Maps ....................................................................................................... 41

Appendix C – Building Equipment Location Maps .................................................................................. 44

Appendix D – MERV Filter Ratings ........................................................................................................... 50

Appendix E – Unit Ventilator Report ....................................................................................................... 52


Glossary of Terms and Abbreviations

ACH Air Change per Hour

• A measure of air flow in a specified volume of space

AHU Air Handling Unit

• HVAC equipment, typically contains fans, filters, and heating and/or cooling coils

AII room Airborne Infection Isolation room

• Room with mechanical systems designed to reduce the spread of airborne

infection disease to other areas

ASHRAE American Society of Heating, Refrigerating, and Air-conditioning Engineers

• Professional organization that supports industry research and publishes design

best practice guidelines and standards

BAS Building Automation System

• Control system for building HVAC and lighting systems

CAV Constant Air Volume

• Describes the type of control of an AHU- this type of unit varies the supply air

temperature but not the volume of air flow

CFM Cubic Feet per Minute

• Measure of volumetric flow, typically used for air flow

DOAS Dedicated Outdoor Air System

• AHU that supplies 100% conditioned outdoor air (does not mix ventilation air

with recirculated room air)

ERU Energy Recovery Unit

• AHU with a heat exchanger to transfer heat between exhaust air and incoming

outdoor air

HEPA High Efficiency Particulate Air (filter)

• A type of filter that can remove at least 99.97% of particles with a size of 0.3

microns.

HVAC Heating, Ventilation, and Air-conditioning

• Term used to describe building systems and technical expertise of professionals

MERV Minimum Efficiency Reporting Value

• A filter’s ability to capture particles between 0.3 and 10 microns in size

• A higher MERV rating captures a larger percentage of small particles

• See Appendix D for MERV ratings and ratings by particle size

OA Outdoor Airflow

• Ventilation air flow

RTU Roof Top Unit

• An HVAC system located on the roof that contains all heating and cooling

equipment in one packaged unit

SF Square Feet

• Measure of area


TAB Test and Balance

• Measurement and adjustment of building HVAC equipment.

VAV Variable Air Volume

• Describes the type of control of an AHU- this type of unit varies both the supply

air temperature and the volume of air flow to a zone

• Also used to describe the piece of equipment in a zone that includes a damper to

reduce airflow (VAV box)

VRF Variable Refrigerant Flow

• A type of refrigeration system that includes an outdoor condensing unit and

indoor fan units with a cooling coil. Sometimes the indoor unit also includes a

heating coil.


Executive Summary

Minneapolis Public Schools (MPS) requested individual facility ventilation studies for all occupied elementary, middle school, and high school buildings. These studies identified improvements to the air handling units (AHUs) and ventilation in the buildings that will allow the building to meet current ASHRAE guidance to limit virus transmission in the ventilation system in the building. Adequate outdoor air flow, or ventilation, can dilute the number of viral particles in the breathing zone of a space. Effective filtration can remove particles from the air. However, viral particles are extremely small. Most filters are not rated to capture particles as small as the virus that causes COVID-19, but some can capture a large fraction of viral-sized particles. While it will not be practical to rely only on filtration, increasing filtration levels will reduce the number of viral particles in the air. This report provides the results for Sheridan Elementary School. KFI has reviewed existing HVAC plans, Test-and-Balance (TAB) reports, and the building automation system (BAS). KFI has also performed an onsite evaluation for the facility. Sheridan Elementary School has multiple air-handling units that supply different spaces. The filtration levels of each HVAC system are detailed in the Building Assessment section, and the final filter MERV levels are provided in Table 1, Table 2, and Table 3. The following is a description of these areas:

1. Classroom areas at Sheridan Elementary School are ventilated by classroom Unit Ventilators

(UVs). Each unit ventilator contains either a 1” MERV 4 or 2” pleated MERV 8 filter. There are

two (2) UVs installed in 1993, 29 UVs installed in 1996, and 15 UVs installed in 2008. It is likely

that the unit ventilators do not have the capacity to overcome an increase in filtration from

currently installed MERV 4 or MERV 8 filters to MERV 14 filtration.

2. The music, band, and dance area is served by AHU-1. It is filtered at a MERV 8 level. Based on

the information available and the age of the unit, it is likely that this unit cannot support an

increase in filtration to the MERV 14 level.

3. The cafeteria is served by AHU-2. It is filtered at a MERV 8 level. Based on the information

available and the age of the unit, it is likely that this unit cannot support an increase in filtration

to the MERV 14 level.

4. The auditorium and associated rooms are served by AHU-3, AHU-4, AHU-5, AHU-6, AHU-7, and

AHU-8. They are filtered at a MERV 8 level. Based on the information available and the age of

these units, it is likely that they cannot support an increase in filtration to the MERV 14 level.

5. The gymnasium is served by AHU-9 and AHU-10. The spaces on the east side of the gym is served

by RTU-01 (1993). The spaces on the west side of the gym is served by RTU-02 (1993). All units

are filtered at a MERV 8 level. Based on the information available and the age of these units, it is

likely that they cannot support an increase in filtration to the MERV 14 level.

6. RTU-01 and RTU-02 were installed in 2011 and serve a classroom and the sourrounding area.

These units are filtered at a MERV 8 level. Based on the information available and the age of these

units, it is likely that they cannot support an increase in filtration to the MERV 14 level.


The nurse’s office (104) could potentially be converted to an isolation room. The conversion would require a divider wall and door, sealing of the walls, and installation of a dedicated supply and exhaust in the room. A new exhaust fan and room pressure controller will need to be added to maintain the required pressure relationship. The nurse’s office may need to be relocated to a nearby office (102) if office 104 is converted to an isolation room. Through this project, a number of conditions were identified that could be corrected immediately. Table 1 summarizes these immediate corrections. Table 2 summarizes recommendations for future system updates that do not require significant capital improvements. Table 3 identifies recommended improvements that will require a capital program expenditure to complete. These improvements should be part of a larger capital effort for improvement to ventilation systems Districtwide. Table 1: Summary of Immediate Corrections

System Tag Existing

Filtration Level*

Serves Work in Progress

AHU-1 MERV8 Band/Dance

• Secure clips on filter rack to prevent

filters from blowing out

• Replace filters with like-for-like

• Change schedules to start at 3:00am

AHU-2 MERV8 Cafeteria • Replace filters with like-for-like


AHU-3 MERV8 S.E. Auditorium

• Secure clips on filter rack to prevent

filters from blowing out



AHU-4 MERV8 Aditorium Lobby • Replace filters with like-for-like


AHU-5 MERV8 Actors Theater and Work

Room



AHU-6 MERV8 N.E. Auditorium • Replace filters with like-for-like


AHU-7 MERV8 S.W. Auditorium • Replace filters with like-for-like


AHU-8 MERV8 N.W. Auditorium • Replace filters with like-for-like


AHU-9 MERV8 East Gym • Replace filters with like-for-like


AHU-10 MERV8 West Gym • Replace filters with like-for-like



System Tag Existing

Filtration Level*

Serves Work in Progress

RTU-01 (1993)

MERV8 Offices on East side of

Gym



RTU-02 (1993)

MERV8 Offices on West side of

Gym



RTU-01 (2011)

MERV8 Room 119 and associated

rooms



RTU-02 (2011)


rooms



UVs (1993, 1996, and

2008)

MERV4 or MERV8

Classrooms on all levels • Replace filters with like-for-like

Table 2: Summary of Recommendations without Significant Capital Expenditures

System Tag Existing

Filtration Level*

Serves Recommendations

AHU-3 MERV8 S.E. Auditorium • Rebalance OA to code minimum 1,236

cfm

RTU-01 (2011) & RTU-02 (2011)


rooms

• Rebalance OA to code minimum 672 cfm

(sum of RTU-01 and RTU-02 OA)

UVs (all) MERV4 or

8 Classrooms

• Set dampers to supply the minimum

ventilation required to meet the

current code

• Increasing the temperature of the hot

water may be necessary to maintain

heating

UV MERV4 or

8 Nurse’s Office 104

• Add standalone HEPA recirculating fan


Table 3: Summary of Recommendations Requiring Capital Expenditures

System Tag Existing

Filtration Level*

Serves Recommendations

AHU-1 MERV8 Band/Dance

• Replace unit

• Measure break horsepower and static

pressure during design to verify the supply

fan can accommodate a MERV 14 filter

• Measure the actual outside air flowrate to

verify that the ventilation meets the current

code

AHU-2 MERV8 Cafeteria • Replace entire unit

AHU-3 MERV8 S.E. Auditorium • Replace entire unit

AHU-4 MERV8 Aditorium Lobby • Replace entire unit

AHU-5 MERV8 Actors Theater and Work

Room • Replace entire unit

AHU-6 MERV8 N.E. Auditorium • Replace entire unit

AHU-7 MERV8 S.W. Auditorium • Replace entire unit

AHU-8 MERV8 N.W. Auditorium • Replace entire unit

AHU-9 MERV8 East Gym • Replace entire unit

AHU-10 MERV8 West Gym • Replace entire unit

RTU-01 (1993)

MERV8 Offices on East side of

Gym

• Replace entire unit

RTU-02 (1993)

MERV8 Offices on West side of

Gym • Replace entire unit

RTU-01 (2011)


rooms • Replace unit

RTU-02 (2011)


rooms

• Replace unit

UVs (1993, 1996, and

2008)

MERV4 or MERV8

Classrooms on all levels

• Replace all individual unit ventilators that

will support MERV14


Disclaimer

Performance guidelines provided in the report are for informational purposes only and are not to be construed as a design document. Recommendations implemented should be installed in conformance to all local code requirements. Ventilation and filtration recommendations are provided based on ventilation requirements in the Minnesota 2020 Mechanical Code and guidance from ASHRAE on limiting viral transfer. If equipment was installed under an earlier code that equipment is not required to comply with the 2020 code.


Introduction

Sheridan Elementary School was constructed in 1896. It was demolished, and the current building was built in 1932. An addition was built in 1967, and the building now covers 148,005 square feet. The classroom areas are located on the perimeter spaces of the three story building, and are ventilated by individual unit ventilators. The common areas utilize AHU’s and RTU’s. The AHUs that serve the gym were installed in 1967. The remaining AHUs are original to the building from 1932. The RTUs were installed in 1993 and 2011. Students have not occupied the school building since March of 2020 due to the COVID-19 pandemic. The SARS-CoV-2 virus causes coronavirus disease, or COVID-19. The SARS-CoV-2 virus is new and research into the virus and disease spread is still evolving. So far, we have learned that primary transmission route of the virus is via the air in droplets and aerosols. Recommendations for reducing the spread of COVID-19 focus broadly on: 1) maintaining social distance between people, 2) sanitizing and cleaning surfaces, and 3) reducing the number and circulation of viral particles in the air. HVAC systems can influence this last item. Adequate outdoor airflow, or ventilation, can dilute the number of viral particles in the breathing zone of a space. Effective filtration can remove particles from the air. However, viral particles are extremely small, on the order of 0.12 microns. Filters are typically rated by the size of particles that will be removed, for example, MERV 14 filters are rated to remove 95% or greater of particles down to 3 microns. While it will not be practical to rely only on filtration, increasing filtration levels will reduce the number of viral particles in the air. ASHRAE guidance is available online at: https://www.ashrae.org/technical-resources/reopening-of-schools-and-universities. This report provides the results for Bancroft Elementary School. KFI has performed the following scope of work:

• Reviewed the existing HVAC building plans and test and balance reports (TAB) to identify

recommended improvements to the systems to meet current ASHRAE guidance for COVID19.

• Performed an on-site assessment of the facility.

• Reviewed the building automation system (BAS) to determine potential control changes to

improve indoor air quality.

https://www.ashrae.org/technical-resources/reopening-of-schools-and-universities


ASHRAE Guidance

The American Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE) provides research, standards, and continuing education that typically define best practice in the HVAC industry. ASHRAE has been developing industry standards for best practice in reducing HVAC spread of airborne illnesses for years. ASHRAE has released guidance for schools and universities to prepare for the reopening of school buildings. This advice focuses on three core principles aimed at reducing the spread of COVID19:

1. Increase outdoor air where possible

a. Follow current ventilation standards at a minimum

b. Ventilate at least 2 hours prior to occupancy

c. Disable demand controlled ventilation during the pandemic

2. Increase filtration levels where possible

a. MERV15 filtration provides similar filtration levels as an N95 mask (95% of particles

entrapped to 3 microns in size)

b. MERV14 filtration is recommended where possible

3. Maintain indoor environments between 40% and 60% relative humidity and temperatures

between 68°F and 78°F where possible

This project focuses on the first two principles above. It seeks to evaluate the ventilation and filtration levels in the existing systems, to evaluate system capacity to increase outdoor air and filtration levels, and to evaluate building control systems to recommend changes. Temperature maintenance for buildings is provided in Board Regulation 3520A. Due to the complexity of establishing and maintaining relative humidity in a space, MPS is not evaluating the relative humidity as part of this study.


Building Assessment/Recommendations

HVAC System Filtration and Ventilation Classroom areas at Sheridan Elementary School are served by individual unit ventilators. Figure 1 shows a 2008 UV system with a heating coil and a DX coil for cooling. There are 46 UVs total. Units from 1993 and 1996 are not connected to the BAS and most likely do not have a DX coil for cooling.

Figure 1: BAS Schematic of a 2008 Unit Ventilator


Constant-air-volume (CAV) systems provide heating, cooling, and ventilation to one specific space within the building. The airflow is constant and does not modulate with an increase or decrease in load and is either on or off. Common areas such as the gym, auditorium, music, and cafeteria are ventilated by RTUs and AHUs which are a CAV system. These units operate with a supply fan, a heating coil, and dampers to modulate the amount of return air and outside air. Refer to Figure 2 for an image of a typical AHU and Figure 3 for an image of a typical RTU.

Figure 2: BAS Schematic of a Typical AHU

Figure 3: BAS Schematic of a Typical RTU


A summary of the systems in the building is provided in Table 4. A matrix was developed for the school systems with airflows, static pressures, filtration, and control details. This matrix is provided in Appendix A. Table 4: System Overview

System Tag Age Serves System Type

AHU-1 1932 Band/Dance CAV

AHU-2 1932 Cafeteria CAV

AHU-3 1932 S.E. Auditorium CAV

AHU-4 1932 Auditorium Lobby CAV

AHU-5 1932 Actors Theater and Work Room CAV

AHU-6 1932 N.E. Auditorium CAV

AHU-7 1932 S.W. Auditorium CAV

AHU-8 1932 N.W. Auditorium CAV

AHU-9 1967 East Gym CAV

AHU-10 1967 West Gym CAV

RTU-01 (2011) 2011 119 Classroom and Conference Room CAV

RTU-02 (2011) 2011 119 Classroom and Conference Room CAV

RTU-01 (1993) 1993 Offices – E side of Gym CAV

RTU-02 (1993) 1993 Offices – W side of Gym CAV

Unit Ventilators The perimeter classrooms and offices are supplied by individual unit ventilators within the space. The information available on these units is not sufficient to determine if these units meet the 2020 outside air code requirements. The outside airflow is determined by a set damper position when installed. The units installed in 2008 were set to supply 18% - 35% outside airflow depending on the unit. Information is not available for the units that were installed in 1993 and 1996. Due to the age and low filtration level of the units it is not likely that they will withstand the increase in pressure from MERV 4 (or in some cases MERV 8) to MERV 14 filters. We recommend replacing these units with new. During the design process ensure the new units are rated for a MERV 14 filter or can withstand the pressure drop of a MERV 14 filter. If replacement of these units is not feasible, we recommend adjusting the damper position, and verify that the outside air meets the current code. Increasing the hot water temperature may be necessary to maintain heating capabilities. The list of unit ventilators and the areas they serve is located in Appendix E – Unit Ventilator Report.


AHU-1 AHU-1 was installed in 1932, and is located on the basement floor in fan room B2. This unit serves the band, music, and dance classrooms on the first floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1962. Ventilation air flows and static pressures are summarized in Table 5. Table 5: System Ventilation and Static Pressure – AHU-1

System Area

Served [sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total

SP [in wc] Actual Total

SP [in wc]

AHU-1 7,237 NR NR 3,709 NR NR

Information is not available to determine if this unit meets the outside air requirement of the current code. AHU-1 is filtered at a MERV 8 level. The filter bank for AHU-1 is shown in Figure 4. Based on the information available and the age of the unit, AHU-1 cannot support an increase in filtration to the MERV 14 level, and it is recommended to replace the entire unit when capital funding is available. It is recommended to adjust filter clips, to prevent filters from blowing out, as seen in Figure 4.

Figure 4: Filter Bank – AHU-1


AHU-2 AHU-2 was installed in 1932, and is located on the basement floor in mechanical room B28A. This unit serves the cafeteria on the basement floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1962. Ventilation air flows and static pressures are summarized in Table 6. Table 6: System Ventilation and Static Pressure – AHU-2

System Area

Served [sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-2 8038 NR NR 9,344 NR NR

Information is not available to determine if this unit meets the outside air requirement of the current code. AHU-2 is filtered at a MERV 8 level. The filter bank for AHU-2 is shown in Figure 5. The break horsepower is within 4% of the nameplate horsepower, which indicates that it will not be able to support more load or an increase in pressure through the filters. Based on the information available and the age of the unit, AHU-2 cannot support an increase in filtration to the MERV 14 level, and it is recommended to replace the entire unit when capital funding is available.



AHU-3 AHU-3 was installed in 1932, and is located on the second floor in mechanical room M222. This unit serves the southeast portion of the Auditorium on the first floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1962. Ventilation air flows and static pressures are summarized in Table 7. Table 7: System Ventilation and Static Pressure – AHU-3

System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-3 1,301 1,205 NR 1,236 NR NR

The actual outside air is below the current code outside air flow requirement. This unit was designed under a different code and increasing outdoor air is not required for code. However, it is recommended to rebalance AHU-3 to minimum 1,236 cfm, as the unit has capacity for this adjustment. AHU-3 is filtered at a MERV 8 level. The filter bank for AHU-3 is shown in Figure 6. Based on the information available and the age of the unit, AHU-3 cannot support an increase in filtration to the MERV 14 level, and it is recommended to replace the entire unit when capital funding is available. It is recommended to adjust filter clips, to prevent filters from blowing out, as seen in Figure 6.



AHU-4 AHU-4 was installed in 1932, and is located on the second floor in mechanical room M222. This unit serves the front lobby for the Auditorium on the first floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1962. Ventilation air flows and static pressures are summarized in Table 8. Table 8: System Ventilation and Static Pressure – AHU-4

System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-4 1,194 555 NR 1,209 NR NR

The unit does not meet the current code ventilation requirement based on the actual outside airflow recorded. This unit was designed under a different code and increasing outdoor air is not required for code. This unit does not have capacity to increase outdoor air flow. AHU-4 is filtered at a MERV 8 level. The filter bank for AHU-4 is shown in Figure 7. Based on the information available and the age of the unit, AHU-4 cannot support an increase in filtration to the MERV 14 level. It is recommended to replace the entire unit when capital funding is available due to less than code required outdoor air flow and filtration level.

Figure 7: Filter Bank - AHU-4


AHU-5 AHU-5 was installed in 1932, and is located on the second floor in mechanical room M222. This unit serves the actors theater and work room on the first floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1962. Ventilation air flows and static pressures are summarized in Table 9. Table 9: System Ventilation and Static Pressure – AHU-5

System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-5 2,187 938 NR 687 NR NR

This unit meets the ventilation requirements of the current code based on the actual outside airflow that was recorded. AHU-5 is filtered at a MERV 8 level. The filter bank for AHU-5 is shown in Figure 8. Based on the information available and the age of the unit, AHU-5 cannot support an increase in filtration to the MERV 14 level, and it is recommended to replace the entire unit when capital funding is available.

Figure 8: Nameplate - AHU-5


AHU-6 AHU-6 was installed in 1932, and is located on the second floor in mechanical room M222. This unit serves the auditorium on the first floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1962. Ventilation air flows and static pressures are summarized in Table 10. Table 10: System Ventilation and Static Pressure – AHU-6

System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-6 1,301 1,259 NR 1,236 NR NR

This unit meets the ventilation requirements of the current code based on the actual outside airflow that was recorded. AHU-6 is filtered at a MERV 8 level. The nameplate for AHU-6 is shown in Figure 9. Based on the information available and the age of the unit, AHU-6 cannot support an increase in filtration to the MERV 14 level. It is recommended to replace the entire unit when capital funding is available.




System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-7 3,214 1,114 NR 3,254 NR NR

This unit does not meet the ventilation requirements of the current code based on the actual outside airflow that was recorded. This unit was designed under a different code and increasing outdoor air is not required for code. This unit does not have capacity to increase outdoor air flow. AHU-7 is filtered at a MERV 8 level. The nameplate for AHU-7 is shown in Figure 10. The break horsepower is within 11% of the nameplate horsepower, which indicates that it will not be able to support any more load or increase in pressure through the filters. Based on the information available and the age of the unit, AHU-7 cannot support an increase in filtration to the MERV 14 level. It is recommended to replace the entire unit when capital funding is available due to less than code required outdoor air flow and filtration level.




System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-8 3,471 1,123 NR 3,514 NR NR

This unit does not meet the ventilation requirements of the current code based on the actual outside airflow that was recorded. This unit was designed under a different code and increasing outdoor air is not required for code. This unit does not have capacity to increase outdoor air flow. AHU-8 is filtered at a MERV 8 level. Based on the information available and the age of the unit, AHU-8 cannot support an increase in filtration to the MERV 14 level. It is recommended to replace the entire unit when capital funding is available due to less than code required outdoor air flow and filtration level.


AHU-9 AHU-9 was installed in 1967, and is located on the basement floor in the east gymnasium. This unit serves the east gymnasium on the basement floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1997. Ventilation air flows and static pressures are summarized in Table 13. Table 13: System Ventilation and Static Pressure – AHU-9

System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-9 4,085 NR NR 1,634 NR NR

Information is not available to determine if this unit meets the outside air requirement of the current code. AHU-9 is filtered at a MERV 8 level. The unit is shown in Figure 11. Based on the information available and the age of the unit, AHU-9 cannot support an increase in filtration to the MERV 14 level. It is recommended to replace the entire unit when capital funding is available.

Figure 11: Gymnasium Unit - AHU-9


AHU-10 AHU-10 was installed in 1967, and is located on the basement floor in the west gymnasium. This unit serves the west gymnasium on the basement floor. It distributes constant volume mixed air to the spaces. This unit has a projected replacement date of 1997. Ventilation air flows and static pressures are summarized in Table 14. Table 14: System Ventilation and Static Pressure – AHU-10

System Area Served

[sf] Actual OA

[cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

AHU-10 4,085 NR NR 1,634 NR NR

Information is not available to determine if this unit meets the outside air requirement of the current code. AHU-10 is filtered at a MERV 8 level. The unit is shown in Figure 12. Based on the information available and the age of the unit, AHU-10 cannot support an increase in filtration to the MERV 14 level, and it is recommended to replace the entire unit when capital funding is available.

Figure 12: Gymnasium Unit - AHU-10


RTU-01 (1993) and RTU-02 (1993) RTU-01 (1993) and RTU-02 (1993) were installed in 1993, and are located on the north end of the basement roof on each side of the gymnasium. RTU-01 (1993) serves the rooms on the east side of the gymnasium. RTU-02 (1993) serves the rooms on the west side of the gymnasium. It distributes constant volume mixed air to the spaces. These units have a projected replacement date of 2008. Ventilation air flows and static pressures are summarized in Table 15. Table 15: System Ventilation and Static Pressure – RTU-01 (1993) and RTU-02 (1993)

System Area

Served [sf] Actual

OA [cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

RTU-01 (1993) 2,093 NR NR 222 NR NR

RTU-02 (1993) 2,130 NR NR 226 NR NR

Information is not available to determine if this unit meets the outside air requirement of the current code. RTU-01 (1993) and RTU-02 (1993) are filtered at a MERV 8 level. Based on the information available and the age of the units, RTU-01 (1993) and RTU-02 (1993) cannot support an increase in filtration to the MERV 14 level. It is recommended to replace both units when capital funding is available.


RTU-01 (2011) and RTU-02 (2011) RTU-01 (2011) and RTU-02 (2011) were installed in 2011, and are located on the north-west end of the first floor roof. Both RTU-01 (2011) and RTU-02 (2011) serve classroom 119 and the associated rooms nearby. It distributes constant volume mixed air to the spaces. These units have a projected replacement date of 2026. Ventilation air flows and static pressures are summarized in Table 16. Table 16: System Ventilation and Static Pressure – RTU-01 (2011) and RTU-02 (2011)

System Area

Served [sf] Actual

OA [cfm] Design OA

[cfm] Code OA

[cfm] Design Total


SP [in wc]

RTU-01 (2011) 1,454

191 NR 672

NR NR

RTU-02 (2011) 392 NR NR NR

This unit does not meet the ventilation requirements of the current code based on the actual outside airflow that was recorded. This unit was designed under a different code, and increasing outdoor air is not required for code. However, it is recommended to rebalance RTU-01 (2011) and RTU-02 (2011) to a sum minimum of 672 cfm, as the units has capacity for this adjustment. RTU-01 (2011) and RTU-02 (2011) are filtered at a MERV 8 level. The nameplates for RTU-01 (2011) and RTU-02 (2011) are shown in Figure 13. Based on the information available and the small motor size of the supply fans, RTU-01 (2011) and RTU-02 (2011) cannot support an increase in filtration to the MERV 14 level. It is recommended to replace both units when capital funding is available.

Figure 13: Namplates for RTU-01 (2011) on Left and RTU-02 (2011) on Right


Intake and Exhaust Separation All intakes and exhaust vents are separated by more than the recommended 10 feet of distance. There is no concern with recirculating exhaust air.

Building Automation System The building automation system was reviewed for temperature and humidity levels, and to review system schedules and control. Details are included in Appendix A. Before the building is occupied, we recommend changing the system operation schedules to have the AHU fans start 2 hours before occupancy – around 3 A.M. Many of the units (AHU-3, AHU-6-10, and 2008 unit ventilators) have demand control with CO2 setpoints. We recommend disabling demand control ventilation and introduce maximum OA. We recommend that the exhaust fans run on a 24-hour schedule to improve air quality and increase ventilation rates. Maximizing the economizer mode would help with ventilation when outside temperatures are 71°F or below. We recommend disabling the economizer sequence once outside air temperatures reach 71°F. The outside air temperature is displayed in the BAS as approximately seven degrees higher than the actual outside air temperature. We recommend reviewing the point mapped on all AHUs, RTUs, and 2008 UVs.


Nurse and Office Area Air Flow Summaries of the airflows in the nurse and main office are provided in Table 17 and Table 18 respectively. The air to the nurse’s office is supplied by a unit ventilator. There is a transfer fan which takes the air from the nurse’s office into the adjacent corridor. It is unlikely that the airflows in these areas meet the 2020 Minnesota ventilation code levels. Air from the nurse’s office is mixed with the general corridor return air so it would need a separate system to serve as an isolation area. A stand-alone HEPA filtration unit at a capacity of 12ACH located in the nurse’s office would limit the viral particles that are returned to the AHU. The nurse’s office is highlighted in orange and the main office area is highlighted in blue in Figure 14.

Table 17: Nurse’s Office Air Flow

Nurse area HVAC System

Supply Air Flow to

Nurse’s Office (cfm)

Area of Nurse’s Office

(sf)

Ceiling Height of Nurse’s Office (ft)

Current ACH Percent OA

UV NR 292 8.0 N/A N/A

N/A = Not Available

Table 18: Main Office Air Flow

Office area HVAC System

Supply Air Flow (cfm)

Area of Main Office (sf)

Ceiling Height (ft)

Current ACH Percent OA

UV-06 1,000 353 8.0 21.2 30%

UV-103 1224 973 8.0 9.4 N/A

N/A = Not Available

Figure 14: Location of Potential Isolation Room in Red, Nurse’s Office in Orange, and Main Office in Blue


Potential Isolation Areas An area has been identified that could be renovated to serve as an isolation room for students who fall ill during the day. This area would need to be designed around ASHRAE Standard 170-2017 Ventilation of Health Care Facilities for Airborne Infection Isolation (AII) Rooms. The airborne infection isolation room would need to be maintained with a negative pressure relationship to adjoining rooms with a minimum of 2 ACH of outdoor air and a minimum 12 ACH of total supply air. All room air will need to be exhausted. If the 12 ACH of supply air is not possible, a HEPA filtered recirculating unit could be provided to increase equivalent ACH requirements. When the room is not used for airborne infection isolation conditions, the room would need to remain with a negative pressure relationship and the minimum supply air rate could be reduced to 6 ACH. MPS directed KFI to review areas near the nurse’s office to identify areas that could serve as airborne infection isolation room. At this facility, the east part of the nurse’s office could potentially be converted to an isolation room. Table 19: Airflow of Potential Isolation Areas

Room or Area

HVAC System

Supply Air Flow

(cfm)

Floor Area (sf)

Ceiling Height

(ft)

Current Total ACH

Current ACH of

OA

Required ACH

Required ACH of

OA

104 Office

Transfer Fan

NR 116 8.0 N/A N/A 12 2


The potential isolation area is location is highlighted in red in Figure 15. The nurse’s office (104) is served by a unit ventilator shown in Figure 16. There is a transfer fan located on the west wall of the nurse’s office that is captured in Figure 17. If the east side of the area were to be converted to an airborne infection isolation room it would need to have a divider wall erected with a door, the room walls sealed, a new dedicated exhaust system at approximately 15 ACH (232 CFM) and new supply air VAV with reheat at 12 ACH (186 CFM). The west part of the nurse’s office would also need a supply air VAV with reheat. A new exhaust fan and room pressure controller will need to be added to maintain the required pressure relationship. The anticipated capital construction costs would be between $200,000 to $250,000. Access to the exam room is through the nurse’s office.

Figure 15: Location of Potential Isolation Room in Red, Nurse’s Office in Orange, and Main Office in Blue


Figure 16: Unit Ventilator in Nurse's Office 104

Figure 17: Transfer Supply to Adjacent Corridor (Left) from the Nurse’s Office Room 104 (Right)


Appendices


Appendix A – Matrix of Existing HVAC System








Appendix B – Building System Maps

cuhar001

Text Box

Redacted for Building Security Purposes


Appendix C – Building Equipment Location Maps Note: These maps of the basement and roof are from the 2016 addition drawings.

cuhar001

Text Box

Redacted for Building Security Purposes


Appendix D – MERV Filter Ratings


https://www.nafahq.org/understanding-merv-nafa-users-guide-to-ansi-ashrae-52-2/

https://www.nafahq.org/understanding-merv-nafa-users-guide-to-ansi-ashrae-52-2/


Appendix E – Unit Ventilator Report










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