100 SW Main Street #1600 Portland, OR 97204 P: 503-382-2687 F: 503-382-2262
100 SW Main Street #1600 Portland, OR 97204 P: 503-382-2661 F: 503-382-2262
100 SW Main Street #1600 Portland, OR 97204 P: 503-382-2738 F: 503-382-2262
Clark Public Utility Electric Utility 1200 Fort Vancouver Way Vancouver, WA 98663 P: (360) 992-3000
NW Natural Gas Gas Utility 220 NW 2nd Ave Portland, OR 97209 P: (800) 422-4012
Section 1 – Executive Summary
Martin Luther King Jr. Elementary School (MLK) is a new 68,000 sf elementary school providing learning opportunities from kindergarten through 5th grade. The school will be designed for full-time enrollment with an approximate 500 student occupant load. The school will be comprised of administration areas, classroom spaces, gym, common corridor/study areas, and a dining area. The proposed building will be designed with high performance energy efficiency measures in mind to reduce building energy consumption.
Above grade exterior walls are framed using steel framing at 16 inches with R-21 batt insulation with additional 2-inch polystyrene rigid insulation with a brick, fiber cement, or CMU veneer. The windows are double-pane, fiberglass frames, with a low-e coating. All envelope prescriptive requirements were met, and no further analysis of alternates was necessary. Window shades have been strategically placed to enhance daylighting, reduce summer solar gains and maintain winter passive solar gain.
LED lighting fixtures are used throughout the majority of the facility. Occupancy sensors control lights in classrooms, administrative spaces and other selected areas. The lighting systems for the proposed design meet the prescriptive requirements so no further alternates were analyzed.
Multiple HVAC systems were analyzed for the proposed project. The Alternate #1 (baseline) and Alternate #2 (high-performance system and proposed system) systems are similar in all aspects except for the heating water source. The Mechanical Alternate #1 utilizes VAV rooftop units with heating water reheat coils heated by two standard efficiency gas boilers, while the Alternate #2 will use gas-fired condensing boilers to meet the heating load. Other systems are incorporated into the rest of the design, but the majority of heating and energy use/savings come from the hot water loop.
For the renewable energy alternative, Alternate #3, a geo-thermal ground loop system was paired with heat pumps in the building design. The net-zero ready alternative, Alternate #4, utilizes an air-cooled chiller serving active chilled beams for the classrooms and offices with systems similar to Alt #1 and Alt #2 for the larger, single-zone spaces.
The proposed HVAC system includes the use of control features such as optimized start and stop, trending, morning warm-up and evening purge. Economizers were included in all HVAC systems analyzed.
The domestic hot water system uses a, gas-fired 97% efficient water heater to supply domestic hot water for the school. This system, in conjunction with low-flow water fixtures, meets the ELCCA prescriptive requirement for domestic hot water.
Mechanical Alternate #2 is the recommended system. Annual energy cost estimates for the recommended building total $26,194. This should not be used for budgeting purposes but only for comparison to similar buildings with similar occupancy schedules and uses.
Table 1- 1: Public Facility Energy Characteristics
Figure 1- 1: Building Energy Use - Alternate #2 [MBtu]
Figure 1- 2: Building Energy Cost – Alternate #2 [Dollars]
Table 1-1: Summary of costs of each alternative analyzed
Work Plan Timeline Update
The current goal is to have the project under construction by June 2019 and completed by the fall of 2020 for the 2020 school opening.
Utility Incentive Programs
Clark Public Utilities offers the CLIP (Commercial Lighting Incentive Program) to help implement approved energy efficient lighting measures.
The intent of this project is to construct a new elementary school in Vancouver, WA. The new facility will meet the School District’s current educational delivery system and technology needs, current building code requirements, and be designed to exceed prescriptive requirements to reduce overall energy use, as well as adhere to other appropriate criteria.
PROJECTGOALSANDDESIGNAPPROACH
The new Martin Luther King Jr. (MLK) Elementary School building will provide an uplifting space that will conserve at minimum 20% energy over a standard building of its size, while remaining a comfortable environment for the enrichment of students’ hearts and minds. The design will suit these goals through an effective and efficient HVAC design utilizing constant volume and VAV air handling units with zone reheat coils served by high efficiency boilers.
PROJECTDESCRIPTION
The two story project is located away from major buildings that would provide external shading. The length of the building stretches east to west to maximize passive solar heating in the winter. External shades are provided on south facing windows and have been located and sized to block summer solar gain without blocking passive solar in the winter.
The school will be designed for full-time enrollment with an approximate 500 student and 50 staff occupant load. It will be composed of administration areas, classroom spaces, gym, common corridor/study areas and a dining area.
Annual usage: Administrative areas will operate according to a normal public school year with spring and winter breaks and closure during the summer months between June and August. The gym and commons area will remain open during the summer months. Differences in annual operation schedules have been accounted for in the energy models.
The following schedules were inputted into the energy model.
Table 2-1: Energy Model Schedules
Section 3 – Simulation and Economic Assumptions
The primary energy modeling was done using IES-VE software, which is supported by the Apache simulation engine. IES-VE is comparable to eQuest in that it uses 8760 TMY file for the energy simulation. In addition IES-VE simulates down to a 2 minute time step, uses the ASHRAE heat balance load method for system sizing and uses Radiance ray tracing algorithms for daylight calculation and simulation. The software is developed to simulate annual energy consumption of proposed buildings on an hourly basis.
The purpose of the energy analysis is to evaluate the proposed baseline building alternative mechanical systems. Applicable alternatives were analyzed and, as a result, recommendations made. The envelope, lighting and DHW systems meet or exceed prescriptive values and no further analysis of alternatives was necessary. The baseline system, a high-performance alternate, a renewable alternate, and a net-zero ready alternate were analyzed and are discussed further in Sections 6, 7 , and 8.
The following inputs were used in all models:
1. Outside air rates per ASHRAE and Washington ventilation standards.
2. Infiltration: 0.15 ACH
3. Occupancy: Classroom – 30 people per room, office – 3 people per room.
4. Miscellaneous loads: spaces range by type from 0.2-0.5 W/ft2 .
5. Envelope constructions were input layer-by-layer as per the typical construction detail shown in this report including appropriate heat capacities.
6. Thermostat Set Points:
a. Occupied Hours: Heating – 70°F, Cooling - 75°F.
b. Unoccupied Hours: Heating – 60°F, Cooling – 80°F
7. During nighttime unoccupied hours, outside air dampers were modeled as closed with cycling allowed to meet space temperature set points.
8. Airside economizer operation enabled at 75°F per ASHRAE standard 90.1, Appendix G.
9. Minimum airflow at VAV terminal units set at 30% of supply airflow.
Although every attempt has been made to model the actual building conditions that will exist when construction is complete, with the most accurate energy simulation program and calculation methods available, energy consumption, and operating costs outlined in this report should not be interpreted as a precise prediction of actual performance once the building is built and occupied. Actual energy consumption and utility costs are likely to differ from results presented herein due to unpredictable variables beyond the control of the modeler. This occurs where the actual building varies from the modeled design and assumptions used in the modeling process. These may include changes in occupancy, schedules, equipment selection and installation, space temperature set-points, building construction, commissioning, weather variations from typical year data used, and other unforeseen circumstances.
Included in this section are the natural gas and electric rate schedules for this project. These rates were used in energy cost estimates included in this report. Detailed schedules used in models are included in this section as well. Clark Public Utilities electricity schedule 34 was used because the proposed model’s demand was around 100 kW. NW Natural gas general sales service schedule 3 was used since natural gas consumption due to heating boilers for primary heating is substantial and this is a non-residential building.
Clark Public Utilities - Electric Utility Rates
NW Natural - Natural Gas Utility Rates
Section 4 – Building Envelope
Alternate #1 matches Washington State Energy Code values for the building envelope values.
Alternates #2 and #3 use slightly more efficient envelope values to help save energy:
Roof: Building roof membrane with R-38 rigid insulation.
Exterior Wall: R-21 batt insulation between metal studs with an additional R-8 of continuous rigid polyisocyanurate insulation outside.
Glazing: Double pane ¼” glass, low-e coating with aluminum frames. Assembly U-value of 0.38 and solar heat gain coefficient of 0.21.
- Classrooms: Cable mounted suspended linear LED downlights will be specified in typical classrooms. Recessed LED direct downlights will be specified in art and STEM classrooms with drop ceilings. Recessed linear LED row downlights will be specified in media classrooms.
- Offices: Recessed LED fixtures will be specified in lieu of traditional linear fluorescent fixtures.
- Corridors: Suspended LED pendants.
- Gymnasium: High-bay LED pendants with wire guard.
- Storage Areas: Fixtures shall be specified as surface mounted LED strip lights.
- Mechanical/Electrical Spaces: Fixtures shall be specified as surface mounted LED strip lights.
Refer to the PFEC for average lighting power densities. Note that these LPDs have been calculated based on the design development lighting drawings, and although they are below ELCCA prescriptive level, they are different from the LPDs listed in the work plan.
Section 6 – Mechanical Systems
For each system analyzed, the Building Energy Performance Reports outputted from IES-VE are summarized in Appendix A. ELCCA spreadsheets are provided for each mechanical system.
Proposed Mechanical System
The proposed mechanical system is Mechanical Alternate #2.
Mechanical System Similarities:
Alternate #1 and #2 are similar in all aspects except for the heating water source. The following system narratives apply to both Alternate #1 and #2:
1. Ventilation: Ventilation systems serving each area of facility are as follows.
a. Classrooms - CO2 sensors will be provided for demand ventilation control.
b. Corridors - VAV terminal units shall be provided to serve corridor spaces to serve overhead supply air diffusers providing minimum ventilation of the main central variable volume air handling units serving the classroom or other adjacent spaces. Corridors will also be served off unitary space recirculation heating/cooling constant volume AH units located above ceilings.
c. Commons, Fitness, Music Room, and Dance/Movement - Air handling unit system with conventional overhead ductwork distribution system. CO2 sensors will be provided for demand ventilation control.
d. Offices/Classrooms – Central variable volume air handler serves VAV terminal units to conventional overhead supply air diffusers.
e. Natural Ventilation – Ventilation will be provided through the central air handler units.
2. Heating/Cooling: The main source for heating and cooling serving dedicated zones are as follows:
a. Classrooms and corridors - Heating water supplied to terminal units, with a unit for each classroom. Coil provided at each terminal unit to temper ventilation air. Cooling is provided from rooftop VAV air handlers with DX cooling.
b. Gym and commons- Conventional overhead single zone system with heating coil and DX cooling provided at central air handling unit.
c. Administration - Conventional overhead VAV system with terminal unit heating water coils and DX cooling provided from rooftop VAV air handlers.
3. Boilers: High efficiency condensing gas fired boilers to be provided for Alt #2.
4. Hydronic System: Interior building hydronic system will be a two pipe system to provide heating for facility as space occupancy demands. Building heating system piping will be served by base mounted split-coupled variable speed pumps. An air separator, expansion tank and chemical filter feeder is provided on each system.
5. Exhaust Systems: Dedicated exhaust fans will handle exhaust air for custodial rooms and toilet rooms adjacent to classroom wings and art classrooms. Fans will have electrically commutated motors where available.
MechanicalAlternate#1(Baseline)
Alt#1 utilizes two 1600 MBH cast-iron boilers for the heating water loop. The cast-iron boilers are 80% efficient. These boilers are the least energy efficient option possible that meets code requirements.
MechanicalAlternate#2
Alternate #2 utilizes the same HVAC systems as Alt #1, with the exception of two high-efficiency condensing boilers to replace the cast-iron boilers in Alt #1. The condensing boilers are 96% efficient.
MechanicalSystems: Conclusion
Alt#1 and Alt#2 both had the same envelope, lighting and HVAC distribution systems. These systems contributed to the energy savings. Alt#1 had an overall reduced first cost and lower costs to maintain, however, it was less energy efficient. Thus, the total lifetime cost of Alt #2 was lower due to system efficiency. Overall, Alt#2 was chosen as the recommended system due to its higher energy efficiency and lower life cycle cost.
Section 7 – Renewable Energy System
The renewable energy system alternate utilizes geo-exchange heat pumps for the classroom and office spaces and single zone VAV geo-exchange heat pumps for large spaces such as the Commons, Fitness, Music Room, and Dance/Movement. This system transfers heat from the ground to refrigerant piping which then serves the building in heating. In cooling heat is rejected from the building into the refrigerant and back into the ground. The following system narratives apply to this renewable Alternate #3
1. Ventilation: Ventilation systems serving each area of facility are as follows.
a. Classrooms - CO2 sensors will be provided for demand ventilation control.
b. Corridors – Fan coil units to be provided to serve corridor spaces, moving air through overhead supply air diffusers providing minimum ventilation.
c. Commons, Fitness, Music Room, and Dance/Movement – Single-zone VAV geoexchange heat pump systems with conventional overhead ductwork distribution system. CO2 sensors will be provided for demand ventilation control.
d. Offices/Classrooms – Geo-exchange heat pumps serve fan coil units providing air to conventional overhead supply air diffusers.
2. Heating/Cooling: The main source for heating and cooling serving dedicated zones are as follows:
a. Classrooms and corridors – Heating and cooling provided by geo-exchange heat pumps serving fan coil units, with a unit for each classroom.
b. Gym and commons- Single zone VAV geo-exchange heat pump systems.
c. Administration - Heating and cooling provided by geo-exchange heat pumps serving fan coil units, with typical overhead air distribution.
3. Exhaust Systems: Dedicated exhaust fans will handle exhaust air for custodial rooms and toilet rooms adjacent to classroom wings and art classrooms. Fans will have electrically commutated motors where available.
Renewable Alternate #3 has a 19.1% energy cost savings. This alternate has the highest life cycle cost and most up-front cost. It would not be an economical HVAC solution for this building.
Section 8 – Net Zero Ready System
Alternate #4 is a hydronic heated and chilled beam system serving the classrooms and offices. Systems similar to Alternate #2 will serve the larger spaces (Commons, Fitness, Music Room, and Dance/Movement). The following system narratives apply to this high-performance building alternate.
1. Ventilation: Ventilation systems serving each area of the facility are as follows.
a. Classrooms – CO2 sensors will be provided for demand ventilation control.
b. Corridors – A domestic outside air system provides minimum ventilation levels to overhead chilled beam units.
c. Commons, Fitness, Music Room, and Dance/Movement - Air handling unit system with conventional overhead ductwork distribution system. CO2 sensors will be provided for demand ventilation control.
d. Offices – A domestic outside air system provides minimum ventilation levels to overhead chilled beam units.
2. Heating/Cooling: The main source for heating and cooling serving dedicated zones are as follows:
a. Classrooms and corridors – Domestic outside air system supplies ventilation air to overhead 4-pipe active chilled beams providing heating and cooling.
b. Commons, Fitness, Music Room, and Dance/Movement - Conventional overhead single zone system with heating and cooling coils provided at central air handling unit.
c. Administration – Domestic outside air system supplies ventilation air to overhead 4pipe active chilled beams providing heating and cooling.
3. Boilers: High efficiency condensing gas fired boilers to be provided for all designs.
4. Hydronic System: Interior building hydronic system will be a four pipe system to provide heating for facility as space occupancy demands. Building heating and cooling system piping will be served by base mounted split-coupled variable speed pumps. An air separator, expansion tank and chemical filter feeder is provided on each system.
5. Exhaust Systems: Dedicated exhaust fans will handle exhaust air for custodial rooms and toilet rooms adjacent to classroom wings and art classrooms. Fans will have electrically commutated motors where available.
Alternate #4 has a 37.8% energy cost savings over the code baseline Alternate #1. Similar to the renewable alternate, this alternate has too high of a lifecycle cost to make it a viable option.
Section 9 – Control Systems
The proposed control system is a comprehensive Direct Digital Control (DDC) system. It will control all HVAC systems, exhaust fans, and domestic hot water recirculation pumps. Space sensors will be used to control the zone VAV terminal units. The system will allow trending, monitoring, and setpoint adjustment.
A controls system checklist for the proposed building is included showing the controls types for the HVAC, lighting, and domestic hot water systems.
Section 10 – Domestic Hot Water (DHW)
The domestic hot water system uses 97% efficient water heaters to supply domestic hot water for the school. Low flow fixtures will be used throughout the facility. The system includes the use of a circulation pump. DHW energy use accounts for less than 10% of the total annual building energy cost.
Section 11 – Other Energy Systems
There are no other energy systems included in the building.
Appendix A – ELCCA Work Plan
Appendix B – IES-VE Input and Output Reports for all Alternates
The following space summary and comparison of constructions are the same for all alternates.
Mechanical Alternate #1 – Energy Cost Budget Model
Mechanical Alternate #2 – High Performance System
Mechanical Alternate #3 – Renewable Energy Alternative
Mechanical Alternate #4 – Net-Zero Ready System
Each Alternate’s Energy Use in kW, KWh, and therms.
