1. HVAC for Educational Facilities
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TROX USA

2. Recent Developments Past practices
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Past practices
Mixed air systems with local fans and/or compressors
First costs and system familiarity were the driving factors
Increased interest in displacement ventilation
Proven IAQ benefits due to enhanced contaminant removal
Potential energy savings
Acoustics

3. Classroom Acoustics • • • • • • • • • • •
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Classroom Acoustics
Normal teacher voice level is 50 to 60 dBA
Signal at receiver should be 15 dBA above background
Background Noise
Classroom acoustical design should insure that all of the of students can hear and comprehend the instructor’s voice spoken at normal (comfortable) levels.

4. Annual cost of $6,300 ($7/FT2) per classroom
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Classroom Acoustics
Demographics
13 to 15% of students slightly impaired
10 to 15% of students learning in a language not spoken at home
Cost of Poor Classroom Acoustics
3% of children need out of class support services ($2,500 annually)
1% of children need outside placement ($15,000 annually) due to acoustics
Here are some statistics regarding students and classroom acoustics.
Annual cost of $6,300 ($7/FT2) per classroom
Based on a 900 ft2 classroom with 28 students

5. Classroom Acoustics Objectives of Standard: Provisions of Standard
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Classroom Acoustics
Basis of ANSI Standard S12.60
Objectives of Standard:
Establish SNR that will enable all students to hear teacher speaking at normal voice level
Academic improvement
Reduction of teacher vocal stress
Provisions of Standard
Reverberation times of 0.6 seconds
Background noise levels ≤ 35dBA in all core learning areas!
In 2002, ANSI adopted a new Standard for classroom noise levels. This Standard calls for a background noise level that does not exceed 35dBA (NC27) in all core learning areas.

6. Source: Classroom Acoustical Study (ATS&R, 2005)
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Classroom Acoustical Study
Minnesota school district
48 classrooms tested
45% over 50 dBA
15% below 40 dBA
None below 35 dBA
Source: Classroom Acoustical Study (ATS&R, 2005)
>55 dBA
10%
35-40 dBA
15%
40-45 dBA
21%
50-55 dBA
35%
45-50 dBA
19%
This slide illustrates the current state of affairs. Almost half of the classrooms tested in this study had background noise levels above 50dBA (NC 42) when the HVAC systems were operating. None of the 48 rooms measured would have complied with ANSI S12.60.

7. Classroom Acoustics • • • • • • • • • • • Current: Proposed:
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Classroom Acoustics
Current:
In new construction, plans submitted under WAC shall specify ventilation equipment and other mechanical noise sources in classrooms are designed to provide background sound which conforms to a noise criterion curve or equivalent not to exceed NC-35. The owner shall certify equipment and features are installed according to the approved plans.
Proposed:
Noise control — Construction requirements (1) School officials shall design ventilation equipment and other mechanical noise sources in classrooms to provide background sound which conforms to a noise criterion curve or equivalent not to exceed NC-35. School officials shall certify, or hire the appropriate person to certify, that ventilation equipment and other mechanical noise sources are installed according to the approved design.
This is the WAC stating NC 35. This is for the acousticians in the audience. The proposed has a slightly different verbiage where it basically states hire an acoustician.

8. Adoption LEED™ for Schools (2007) ASHRAE Handbook (Applications, 2007)
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Adoption
LEED™ for Schools (2007)
ASHRAE Handbook (Applications, 2007)
Various school districts
State of Connecticut
New Hampshire Department of Education
New Jersey School Construction Board
Ohio School Facility Commission
New York City Public Schools
Arlington County (VA) Public Schools
Like any ANSI Standard, its adoption into regulatory codes is optional, however more and more jurisdictions are adopting ANSI S In addition, organizations which drive classroom HVAC design have referenced compliance to the Standard as “good practice”.

9. Displacement Ventilation
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Displacement Ventilation
Over the past few years, thermal displacement ventilation systems have become more popular for use in classroom HVAC applications.

10. Displacement Conditioning of Classrooms
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Heat Source
Displacement conditioning systems utilize low sidewall or floor level supply outlets which discharge conditioned air at a very low velocity. If the conditioned air is cooler than that within the room, it falls immediately and spreads evenly throughout, creating a thin layer (4 to 6” thick) adjacent to the floor surface.
The presence of warmer ambient air above this layer prevents it from rising through the room to the return outlet located at the ceiling (or a high sidewall location) except in areas where convective heat sources (such as occupants and equipment) reside. Convective heat transfer from these sources to the ambient air creates a rising heat plume which induces air along its surfaces as it rises. Cool conditioned air is induced from the aforementioned reservoir near the floor to replace the air induced by the heat plume. This conditioned air is then drawn up over the heat source where it conditions it and serves as the source for inhaled respiration. When the air is exhaled, it is warmer than the ambient air around it, thus it escapes upward with the heat plume.
Heat plumes that emanate sufficiently higher than the conditioned air reservoir are replenished by already stratified ambient air and do not reduce the cooling capacity of the supply airflow. The convective contribution of these heat sources can be factored or ignored completely during the calculation of space supply airflow rates as it escapes to the overhead return due to natural buoyancy.

11. This short video illustrates a displacement system operation
This short video illustrates a displacement system operation. The air is supplied through the lower grille on the left wall. The only active heat sources in the room are the mannequins (heated to the temperature of a human body) and the overhead fluorescent lights.

12. Adjacent Zone Adjacent Zone
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Adjacent Zone
Adjacent Zone
Area where velocities greater than 40 fpm may exist
Occupants should not be located within this area
Defined by manufacturers’ literature
V ≤ 40 FPM
Finally, the employment of displacement conditioning may result in significant operational costs reductions, especially in mild, dry climates. Economizer operation may be extended due to the higher supply air temperatures used by the system. Higher chiller operational efficiencies may result from the use of warmer return water temperatures.
L0.2

13. Percentage of Room Height (X)
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Adjacent Zone TE
V ≤ 40 FPM
Adjacent Zone
Percentage of Room Height (X)
Occupied Zone
Finally, the employment of displacement conditioning may result in significant operational costs reductions, especially in mild, dry climates. Economizer operation may be extended due to the higher supply air temperatures used by the system. Higher chiller operational efficiencies may result from the use of warmer return water temperatures.
Maximum 5°F ASHRAE Standard 55
L0.2 TS
0.50
(TX – TS) / (TE – TS)

14. Adjacent Zone Area = ~190 ft2
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Adjacent Zone Effect
Adjacent Zone = 9 feet
Adjacent Zone Area = ~190 ft2
Finally, the employment of displacement conditioning may result in significant operational costs reductions, especially in mild, dry climates. Economizer operation may be extended due to the higher supply air temperatures used by the system. Higher chiller operational efficiencies may result from the use of warmer return water temperatures.

15. Adjacent Zone Effect • • • • • • • • • • •
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Adjacent Zone Effect
Trox Adjacent Zone = 9 feet
Adjacent Zone Area = ~120 ft2
VS.
Brand “X” Adjacent Zone = 21 feet
Adjacent Zone Area = 600 ft2
Finally, the employment of displacement conditioning may result in significant operational costs reductions, especially in mild, dry climates. Economizer operation may be extended due to the higher supply air temperatures used by the system. Higher chiller operational efficiencies may result from the use of warmer return water temperatures. This schools approximate construction cost was $200/sq ft. If we multiple that by the area that would be uncomfortable and could seat students that would adequate to $81,000 per class room.
Aprox. Cost For School Construction ~$200/Ft2
Cost of lost space due to larger adjacent zone:
$81,000 per Class room

16. Adjacent Zone Effect
So why is there such a difference between manufactures? Nozzles VS Perforated

17. Displacement Conditioning Advantages
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Displacement Conditioning Advantages
Low space acoustical levels
Displacement systems are also inherently very quiet because of their low discharge velocities (50 to 60 FPM). This is very important for classroom applications.

18. Displacement Conditioning Advantages
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Displacement Conditioning Advantages
Low space acoustical levels
Enhanced contaminant removal efficiencies
Independent studies
Minnesota elementary school
A Minnesota school district studied the effects of displacement ventilation versus mixed air systems in an elementary school setting.

19. Minnesota Elementary School CO2 Concentration (PPM)
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Displacement Conditioning Advantages
Minnesota Elementary School
Identical classrooms
Tests conducted over two week period
CO2 concentration at six foot level monitored
Mixed system: 1200 PPM
DV System: 400 PPM
1600
1400
1200
Mixed Air System (UV)
1000
CO2 Concentration (PPM)
800
600
Displacement System
Two identical classrooms were compared, one with a unit ventilator (UV) and the other with a displacement system. This slide illustrates the CO2 concentrations in each classroom throughout the school day.
Note that the CO2 concentration in the room served by displacement was (on average) less than half that of the room with the mixed air system (dilution ventilation).
400
Time

20. Displacement Conditioning Advantages in the Northwest
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Displacement Conditioning Advantages in the Northwest
Low space acoustical levels
Enhanced contaminant removal efficiencies
Reduced operational costs
More periods of free cooling
A Minnesota school district studied the effects of displacement ventilation versus mixed air systems in an elementary school setting.

21. 49% Increase in Free Cooling (ASHRAE BIN DATA FOR SEATTLE)
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Air-side Economizer Opportunities in the Northwest
A Minnesota school district studied the effects of displacement ventilation versus mixed air systems in an elementary school setting.
49% Increase in Free Cooling
(ASHRAE BIN DATA FOR SEATTLE)

22. Displacement Conditioning Issues in Northwest
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Displacement Conditioning Issues in Northwest
Enhanced contaminant removal
Excellent space acoustics
Reduced operational costs
Slightly higher supply airflow rates
Lower ΔT with conventional ceiling heights
Larger terminal units
Larger fans and ductwork
Separate heating system required
Use with DOAS is not feasible
Airflow requirement for sensible cooling is 2.2 to 2.5 times ventilation airflow rate.
65 to 70% of return is recirculated to room
That said there are some issues that have limited the use of displacement systems in North America.
In particular, the provision of warmer (62 to 65°F) supply air to the classroom requires special treatment at the air handling unit if the space humidity is to be properly maintained.

23. Advantages of DOAS Systems
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Advantages of DOAS Systems
Energy and IAQ Related Advantages
Free air-side cooling during a large portion of the year
Guarantees delivery of appropriate ventilation air to classrooms
Operational Advantages
Simplifies use of CO2 demand control ventilation
Minimizes likelihood of system modification
A Minnesota school district studied the effects of displacement ventilation versus mixed air systems in an elementary school setting.

24. Air-water Cooling System
Passive Chilled Beams
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Passive Chilled Beam
This illustrates the use of a chilled beam above the window to treat building skin cooling loads. A fin tube heating coil installed in a trough below the access floor provides space heating when required. Ventilation and dehumidification of the space is accomplished by manually or automatically controlled floor diffusers.
Such a perimeter temperature control strategy offers several advantages over the use of fan terminals or other all air strategies:
The amount of heat transferred within the floor plenum is insignificant as the beam has sufficient sensible cooling capacity to condition the space. The diffusers are only tasked with ventilating and dehumidifying the space.
Space cooling is independent of any thermal interactions between the façade and the slab
Fan terminals are virtually inaccessible once the tenants have moved into the space. Chilled beams can be easily accessed as the mount above the façade.
Building airflow rates can be substantially reduced by the use of the chilled beams.

25. Passive Beam Advantages and Disadvantages
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Passive Beam Advantages and Disadvantages
Separate heating system still required
Possible thermal comfort issues
Potential drafts below beams doing large amounts of cooling
Condensation potential
Chilled water must be supplied above space dew point
No condensate trays
Reduce space airflow requirement to space ventilation rate
Reduced air handling units and ductwork
Enables use of DOAS
Compliant Acoustics
Reduced transport costs
That said there are some issues that have limited the use of displacement systems in North America.
In particular, the provision of warmer (62 to 65°F) supply air to the classroom requires special treatment at the air handling unit if the space humidity is to be properly maintained.

26. Displacement Chilled Beams
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Displacement Chilled Beams
Induction Nozzles
Primary air delivered at 50 to 55ºF
Mixing within terminal elevates supply air to appropriate temperature
Integral Heat Transfer Coil
Room air induced through coil
Supplements space cooling
Eliminates separate heating system
Here is the result of our development efforts.
TROX QLCI displacement chilled beams are specifically designed for North American classroom applications and provide all of the advantages of displacement conditioning while minimizing the design issues previously stated.
The classroom is ventilated and conditioned in a displacement manner, identical to that in conventional displacement systems. However, the QLCI terminals also incorporate a series of induction nozzles and a heat transfer coil which allows the induction and reconditioning of room air within the terminal.

27. Displacement Chilled Beams
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Displacement Chilled Beams
Cooling mode operation
100% Exhausted
Return Air 420 CFM
(82 to 85ºF)
Primary Airflow 420 CFM
(52 to 55ºF)
Room Air 840 CFM
(75 to 78ºF)
This slide illustrates the operation of the QLCI in a cooling mode.
Primary air is delivered through the induction nozzles. The velocity of the nozzles induces room air through the integral heat transfer coil which is then cooled in accordance with space thermostat demands prior to mixing with the primary air.
The use of room air induction and reconditioning allows the use of 100% outside air as the primary air source. This outside air is cooled to saturation at 50 to 54ºF within the air handling unit, then ducted to the QLCI terminals. Mixing with the reconditioned room air elevates the temperature of the air mixture to a level which is appropriate for displacement conditioning of the space. The space thermostat regulates the amount of induced air reconditioning in accordance with the room cooling requirements, resulting in a constant volume, variable temperature (61 to 68ºF) discharge to the classroom.
Most classrooms can be adequately conditioned and dehumidified with a primary airflow delivery equal to (or just slightly above) the required space ventilation rate. Most applications allow the chilled water supply to the QLCI terminals to be maintained at least 1ºF above the space dew point temperature so that no condensation within the terminals occurs.
Note that the return airflow from the classroom is equal to the primary airflow rate so the return air is exhausted and no recirculation at the air handling unit is necessary. As such, the recycling of airborne contaminants to the classrooms served by the air handling unit does not occur.
Chilled Water
(57 to 60°F)
Supply Air
1260 CFM
(62 to 68ºF)

28. Supply Airflow 1260 CFM (82 to 85ºF)
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Displacement Chilled Beams
Heating mode operation
Primary Airflow 420 CFM
(55 to 60ºF)
Room Air 840 CFM (70 to 72ºF)
This slide illustrates the operation of the QLCI in a heating mode.
Primary air continues to be delivered cooler than the ambient air in the classroom. .It is is discharged through induction nozzles induces room air through the integral heat transfer coil. This air is cooled in accordance with space thermostat demands prior to mixing with the primary air.
The resultant air delivery to the space is a displacement type mixture of primary and recirculated air at 62 to 68F.
Hot Water (120 to 130°F)
Supply Airflow 1260 CFM (82 to 85ºF)

29. Displacement Chilled Beams
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Displacement Chilled Beams
Staggered heating operation
Primary 60°F
Coil Off
Primary 60°F
Coil Off
90˚F
68˚F
68˚F
90˚F
The number of terminals requiring four pipe coils is determined by the heating requirements of the environment in which they are operating.
Only the minimum amount of terminals required to satisfy the space heating load should be fitted with four pipe coils. This way a maximum amount of supply air will continue to discharge in a displacement fashion.

30. Displacement Chilled Beam Advantages
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Displacement Chilled Beam Advantages
Acoustic levels compliant with ANSI S
Heating and cooling supplied through same terminals
No concern regarding condensation
Simple system with minimal maintenance requirements
Reduce ducted airflow requirement to space ventilation rate
Reduced air handling units and ductwork sizes
Enables use of DOAS
That said there are some issues that have limited the use of displacement systems in North America.
In particular, the provision of warmer (62 to 65°F) supply air to the classroom requires special treatment at the air handling unit if the space humidity is to be properly maintained.

31. Heat Recovery (Optional)
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Displacement Chilled Beams with DOAS
Airflow quantities based on 6 classrooms per AHU
Exhaust Air F
Return Air
(82° F)
Heat Recovery (Optional)
Heating Coil
….and replaced it with this!
This is really just a dedicated outdoor air system whose air handling capacity is only about 1/3 that of the previously shown unit.
It handles 100% outside air and has no recirculation at the AHU, further enhancing the air quality in the classrooms it serves.
Outside Air F
Supply Air
(51 to 54° F)
51°F Dew Point
OA Damper
Filters
Cooling Coil
Blower

32. LEED Credits LEED for Schools Version 2007 Energy and Atmosphere
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LEED Credits
LEED for Schools Version 2007
Energy and Atmosphere
Credit 1 Energy reduction 4 to 6 points
Credit 4 Enhanced refrigerant management point
Indoor Environmental Quality
Credit 1 OA monitoring and maintenance point
Credit 2 Increased ventilation (30%) point
Credit 7 Compliance with ASHRAE point
Credit 9 Enhanced acoustical performance points
Credit 10 Mold prevention (RH < 60%) point
Innovation & Design Process
Dedicated outdoor air system (no recirculation) 1 to 2 points
12 to 15 Points
Finally, the displacement chilled beam system contributes to the achievement of as many as 15 points toward LEED™ certification.

33. Installation Examples
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Installation Examples
This is a photo of the installed system.

34. INSERT ADDITIONAL SLIDES WITH PHOTOS FROM MINNEAPOLIS SCHOOLS HERE
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Installation Examples
INSERT ADDITIONAL SLIDES WITH PHOTOS FROM MINNEAPOLIS SCHOOLS HERE
This is a photo of the installed system.

35. HVAC for Educational Facilities
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TROX USA