1. Packaged Variable Air Volume (VAV) Rooftop Units (RTU) with Hot Water Reheat. 2. Geothermal Heat Pump VAV Rooftop Units with Hot Water Reheat

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1 July 6, 2017 City of Countryside Attn: Mayor Sean McDermott City Hall 5550 East Avenue Countryside, IL RE: New City Hall & Police Building HVAC Options Dear Mayor McDermott, Per your request at our meeting on June 22 nd, the following is a summary of the three HVAC system options that were presented for consideration for the project. Also attached with this letter are several of the slides that were used to illustrate and compare these options. The three systems being considered are: 1. Packaged Variable Air Volume (VAV) Rooftop Units (RTU) with Hot Water Reheat 2. Geothermal Heat Pump VAV Rooftop Units with Hot Water Reheat 3. Distributed Geothermal Heat Pumps with Rooftop Dedicated Outdoor Air System (DOAS) Units The 3 options are generally described in the following paragraphs. The attached slides include schematic drawings illustrating each option, as well as the comparative advantages and disadvantages of each system. Packaged VAV Rooftop Units with Hot Water Reheat The base HVAC option consists of two (2) conventional packaged VAV rooftop units, one serving City Hall and one serving the Police Building. These units have electric direct-expansion (DX) cooling and gas-fired heating. They introduce outdoor air to the system and supply conditioned air to VAV terminal boxes with hot water reheat coils for each zone. The VAV boxes modulate airflow and the hot water reheat coils temper the air to maintain the thermostat setpoint at each zone. Gas-fired boilers produce hot water that is circulated to the reheat coils year-round for supplemental space heating during the winter and tempering during the summer. A gas-fired water heater is used for domestic water heating. Geothermal Heat Pump VAV Rooftop Units with Hot Water Reheat This geothermal option is configured very similar to the base HVAC option described above, except that the two rooftop units will each contain a water-source heat pump to reject/reclaim heat from a geothermal bore field located on the site. Vertical bores up to 450 feet deep will be drilled with loop piping installed to circulate water between the bore field and the rooftop units to exchange heat energy. Page 1 of 2

2 Mayor Sean McDermott Countryside City Hall & Police Building HVAC July 6, 2017 In lieu of gas-fired boilers, a water-source heat pump will be used to produce hot water for the reheat coils. Another water-source heat pump will be used to heat domestic water. Heat rejected during the summer cooling season will first be reclaimed for the reheat coils or domestic water heating, with the remainder transferred to the geothermal field. During the heating season, heat will be reclaimed from the ground and used to heat the building. Distributed Geothermal Heat Pumps with Rooftop DOAS Units This geothermal option uses a water-source heat pump for each individual zone in lieu of VAV boxes. Two (2) smaller rooftop DOAS units will supply required outdoor air to each heat pump. The individual heat pumps will produce the heating or cooling as required by each zone. Each unit contains a fan, compressor, filter and coils and will be mounted above the ceilings. The geothermal bore field will be the same as the previous option, with loop piping to circulate water from the bore field to each individual heat pump. A water-source heat pump will be used to heat domestic water. Please refer to the attached diagrams and comparisons of the three options, and if you have any questions about the different systems described above please feel free to contact me. Sincerely, David J. Evers, PE, CEM, LEED AP Senior Associate Page 2 of 2

3 Designing For The Future Countryside Mechanical Design Energy Performance and System Selection David Evers, PE, CEM, LEED-AP June 22, 2017

4 HVAC Selection Factors First Cost Energy Cost Maintainability Complexity Comfort (temperature, humidity, noise, etc.) Life expectancy Flexibility for renovation Sustainability 2 Countryside Mechanical Design June 22, 2017

5 Base HVAC VAV Reheat 3 Countryside Mechanical Design June 22, 2017

6 Geothermal Option 1 VAV 4 Countryside Mechanical Design June 22, 2017

7 Geothermal Option 2 - Distributed 5 Countryside Mechanical Design June 22, 2017

8 Rooftop Unit VAV Reheat Advantages Lowest First Cost Average Energy Cost Easy to maintain Simple operation Good comfort control Good life expectancy Good flexibility for renovation Disadvantages Gas boilers Average Energy Cost No renewable energy 6 Countryside Mechanical Design June 22, 2017

9 Geothermal VAV Advantages Renewable Energy Low Energy Cost (all electric) Energy Recovery Easy to maintain Simple operation Good comfort control Good life expectancy Good flexibility for renovation Disadvantages Higher First Cost Less conventional 7 Countryside Mechanical Design June 22, 2017

10 Geothermal Distributed Advantages Renewable Energy Low Energy Cost (all electric) Energy Recovery Conventional heat pump system Disadvantages Higher First Cost Average comfort control (noise) Maintainability Many units to maintain Above ceilings Not as flexible for renovation 8 Countryside Mechanical Design June 22, 2017

11 HVAC System Comparison RTU VAV Reheat Geothermal VAV Reheat Geothermal Distributed First Cost Energy Cost Maintainability Complexity Comfort Control Life Expectancy Flexibility Sustainability TOTAL SCORE Countryside Mechanical Design June 22, 2017