Thorton Building Energy Audit Case Study

The Thorton Building is a five-story building in Butte that contains office space and a 900-square-foot data center in the basement. The center is a significant consumer of energy, due to its servers and their dedicated cooling system. The building houses a 45-year-old steam boiler that provides heat through terminal units to the basement, as well as the first and second floors. The boiler also provides heat to the remaining floors when needed, through a heat pump loop.

Cooling equipment for the server and the UPS rooms is comprised of six systems, including computer room air-conditioning (CRAC) units and packaged air-conditioning (AC) units.  The four CRAC units are water-source heat pumps. The piping and heat exchanger direct heat from the data center into the heat pump loop during the heating season into an adjacent mechanical room. Water serves as the heat-rejection medium, and it is pumped to the cooling tower at the top of the building. The heat pumps direct refrigerant through coils in the CRAC units to cool the data center. Two of the CRAC units are air-cooled instead of water-cooled.

MREP suggested the following, based on audit observations:

  1. None of the CRAC circulation lines are insulated. Insulating these lines is a low-cost opportunity for immediate energy savings with a short-term payback.
  2. Hot-water heating lines in other areas of the building do not appear to be insulated. Insulating these lines is a low-cost opportunity for immediate energy savings with a short-term payback.
  3. Seals around some of the piping and/or ductwork from the CRAC units entering the data center are leaky. This results in contaminated air entering the computer room, as well as in wasted energy.
  4. No computer room wall or ceiling insulation was observed. Installing insulation could reduce cooling load and provide energy savings.
  5. Contact the data center cooling equipment installer and request a scan of the most recent drawings of piping and equipment and have the installer come to the site and label all system panels and circuits.
  6. The owners expressed an interest in pursuing the idea of economizer cooling for the data center by placing a heat exchanger in the alley north of the building. Butte’s climate is conducive to economizer cooling for much of the year. MREP recommended an analysis by an engineer to determine system size, cost-effectiveness, effects on the relative humidity and air quality within the data room, and how such a system would interact with the existing cooling systems for the data center. If a well-designed economizer system were installed, it could likely meet a large part of the cooling load in the data center.
  7. Lighting in the basement contains T12 fluorescent lamps with magnetic ballasts, and the remainder of the building contains T8 fluorescent lamps with electronic ballasts. Potential savings are summarized in the following tables.

Building-Wide LED Conversion Cost, Savings, and Simple Payback:

Annual Bill Savings LED Cost Utility Incentives Annual KWH Savings Simple Payback (yr.)
$8,358 $33,367 $7,352 66,617 3.1

 Basement-Only LED Conversion Cost, Savings, and Simple Payback:

Annual Bill Savings LED Cost Utility Incentives Annual KWH Savings Simple Payback (yr.)
$2,174 $3,233 $1,020 17,576 1.0

 

Real Food Store

Energy costs in grocery stores can be quite high. But thanks to an energy audit performed by the Montana Resource Efficiency Program (MREP), an organic grocery in Helena has a variety of options to reduce those costs.

The Real Food Store is an organic grocery and deli, located in Helena, Montana. The one-story retail facility has an open floor plan that includes a group of offices, a break room, and a meeting room. The building consumes electricity and natural gas at a higher rate in summer months, as shown in Figures 1 and 2. This indicates that cooling is the largest energy consumption source.

Electric Usage, June 2015-May 2017

 

Electric Demand, June 2015-May 2017

HVAC Recommendations

The Real Food Store building’s HVAC systems consists of five rooftop units, or RTUs, each designed for different areas of the store. These rooftop units use natural gas to heat and electricity to cool with the condensers integrated into each unit. The ductwork is exposed and not insulated, and the addition of insulation could increase efficiency. Insulating the east and north perimeters of the crawlspace walls could also negate heat loss in winter months.

There are several employee comfort issues in the office area of the store, which is very cold in winter months. This problem can be contributed to a bad thermostat location or improper zoning for the thermostat. It could also be the result of incorrect venting, the need for weatherization of windows in the office areas, or a large return grille that is located directly across from the offices. MREP strongly recommended a retro-commissioning study to determine the source of uneven heating and cooling in this area.

The older rooftop cooling units do not have energy-saving options, such as variable frequency drives (VFDs) or electronically communicated motors (ECMs).  The store can retrofit the units with VFDs and ECMs to allow the efficient motors to work at speeds associated with demand.

Refrigeration is the largest cost for most grocery stores. There are a couple options that can help diminish the cost and energy use of the store’s refrigeration system. These options are expensive to implement and are recommended only if a complete overhaul of the system is necessary in the future. If a new design is required for the condensers, we recommend constructing a racking system for the condensers. This would combine the condensers into one control room and run them in parallel to maximize the energy efficiency.

Hot-water heat recovery is another energy-efficiency measure to consider. Grocery stores have a great opportunity to use the heat rejected by the condensers for domestic hot water heating. Hot-water heat recovery requires additional plumbing and equipment but can save a large amount of energy by preheating the incoming water before reaching the hot water heater and can save 300 therms of natural gas a month. This energy-saving measure could be implemented without an overhaul of the refrigeration system.

Domestic Hot Water Heating Energy Recommendations

According to the deli manager, the Real Food Store serves on average 170 hot meals per day and 170 cold meals per day. It is estimated that the store’s deli uses 2,890 gallons of hot water per day[1]. This adds up to approximately 500 therms of natural gas a month, costing upwards of $375 per month for hot water heating alone. Below are some recommendations for reducing this cost:

  • Install low-flow kitchen and bathroom faucets
  • If the dishwasher, ice machine, or steam cooker needs replacing, invest in an ENERGY STAR-certified model
  • Install high-efficiency pre-rinse spray valves for dishwashing

[1] ASHRAE (2011). Hot-Water Requirements and Storage Equipment Sizing. ASHRAE Handbook: HVAC Applications (pp.50.11-50.13). Atlanta, GA: ASHRAE.

Lighting Recommendations

The store’s lighting consists of metal halides, fluorescent tubes, CFL, incandescent, and PAR 30 bulbs. MREP engineers developed an LED conversion design with the following savings and payback:

  • LED Cost: $8,567
  • Utility Incentive: $2,120
  • Net Cost: $6,447
  • Annual Bill Savings: $3,570
  • Annual Energy Savings: 24,930 KWH
  • Simple Payback with Energy Savings: 1.8 years

Montana State Hospital Warm Springs

The Montana State Hospital Warm Springs exterior lighting consisted of a large variety of lights, including floods, yard lights, can lights, wall packs, and pole lights. A lighting project was completed replacing all of the exterior lighting with new energy-efficient LED lights. Over 280 lights were changed during this project. In addition to saving 413,920 in energy each year, the new LED fixtures provide a better quality of light and will require much less maintenance.

This project received $14,250 in utility lighting rebates. The utility rebate brought the net project cost to an estimated $116,705. The annual energy cost savings was estimated at $13,920. The simple payback of the lighting retrofit is 8.38 years, not including maintenance savings.

  • Project Cost: $130,955
  • Utility Incentives: $14,250
  • Net Cost: $116,705
  • Annual Bill Savings: $13,920
  • Annual Energy Savings: 174,008 kWh
  • Simple Payback with Energy Savings: 8.38 years

Livingston School District

Following a lighting audit and recommendations made by the Montana Resource Efficiency Program (MREP), the Livingston (Montana) School District is poised to save over $36,000 in lighting costs each year.

The School District is comprised of five schools, which collectively serve a student body of some 1,400 students from late August until late May each year. In addition, the district maintains a bus barn.

Based on recommendations from MREP, the school district is currently converting its lighting to LED.  The lighting throughout the District was primarily fluorescent T8 fixtures with the exception of the high school, which was retrofitted with 28-watt T5 fluorescents in 2011 when it was remodeled. Lighting accounted for nearly 25% of the districts electric consumption. Total electric usage for the district is shown in the table below.

Utility Annual Use (kWh) Total Annual Cost ($)
Total Electric Usage 1,465,124 $190,176
Park High School  757,620 $82,569
Eastside and Sleeping Giant 476,640 $52,507
Winans Elementary 61,888 $7,262
Washington Elem. 40,852 $5,635

The estimated cost to upgrade lighting in the schools was $30,750 after utility rebates were applied.  Annual energy cost savings is estimated at $36,692, for a simple payback of just over 10 months. This payback can be shortened further by rising utility rates and increased longevity of the LED bulbs.

Considering the cost of the short payback, this project was a sound investment for the District. Costs, savings, rebates, and payback are detailed below.

Livingston Schools Annual Bill Savings Est. Project Cost Est. Rebates Net Project Cost KWh Savings Simple Payback
LED

Conversion

  

$36,692

  

$74,862

  

$44,112

  

$30,750

  

319,627

  

0.84 years

Livingston Ace Hardware

Livingston Ace Hardware Energy Audit Case Study

The Ace Hardware in Livingston, Montana, is a 13,000 ft2 retail building.  The store owner contacted the Montana Resource Efficiency Program (MREP) for assistance with their lighting update.  The owner wanted more and brighter energy-efficient lighting in the store.  After a lighting audit and analysis,  an MREP engineer recommended upgrading the fluorescent tube lighting to 15-watt LED tubes.  After the change-out of over 800 bulbs the owner reported a better quality of light and is very happy with the upgrade.

The overall cost of the project was $8,544.  The project qualified for $3,961 in rebates from the utility’s rebate program, bringing the net cost to $4,583.  This project will also save Ace Hardware approximately $8,900 per year in energy bills, which brings the project a simple payback of less than one year.  Here is a summary of the financial aspects of the project:

  • Annual bill savings:  $8,899
  • Estimated project costs:  $8,544
  • Estimated rebate:  $3,961
  • Estimated net cost:  $4,583
  • Estimated kWh savings:  149,729
  • Simple payback: 0.52 years

Granite County Courthouse

The Granite County courthouse, located in Philipsburg, Montana, was constructed in 1913 of brick and Montana granite. The building is three stories tall and is comprised of heavy woodwork, large wood and granite columns, a large dome with a stained glass skylight, and tile mosaic floors.

The courthouse recently completed a large lighting project, which included the replacement of old light fixtures with new energy-efficient LED fixtures. The 140 fixtures changed during the project qualified for $7,000 in utility rebates from a lighting rebate program and will result in $4,928 per year in energy bill savings. The net cost of the project was $29,835, giving the project a simple payback of about six years. Here is a quick summary of the project:

  • Annual bill savings: $4,928
  • Project cost: $36,835
  • Rebate: $7,000
  • Net cost: $29,835
  • kWh savings: 64,056
  • Simple payback: 6.05 years

 

Front Street Market

The Front Street Market is a one-story grocery retail building with an unfinished basement. The main floor contains a commercial kitchen, office space, retail space, and a deli. The MREP team audited Front Street Market and identified several energy-saving opportunities for refrigeration and lighting systems.

There are 11 coolers, one walk-in cooler for beverages, one large freezer, and one walk-in freezer throughout the building, each using their own compressor. The HVAC system consists of two furnaces and a unit heater in each of the front rooms of the store. Each furnace is tied to a compressor for cooling. A conversion to high-efficiency compressors would increase the energy efficiency of these systems, particularly during summer months.

The market should also install variable-frequency drives (VFD) to existing cooler and freezer motors. The measure would save 30 to 60% of the motor’s energy usage, depending on the size and frequency of use. Additionally, there are two service doors located on the north and south sides of the beer cooler, and each door is slightly drafty, causing a loss in cooling. MREP recommended replacement of the deteriorated weatherstripping on these doors to prevent cooling loss.

Lighting within the building is comprised of 20-watt CFLs; 4-foot, 30-watt fluorescent tubes; and 8-foot 138-watt fluorescent tubes. Converting these lights to approved LEDs reduces the energy consumption in the building by 6,762 kWh annually.

  • LEDs Cost: $1,663
  • Utility Incentives: $916
  • Net Cost: $747
  • Annual Bill Savings: $762
  • Annual Energy Savings: 6,762 kWh
  • Simple Payback with Energy Savings: 0.98 years

 

Enterprise Holdings

Enterprise Holdings now has some specific energy-efficiency options that could improve its bottom line, thanks to a comprehensive energy audit of its facilities performed by MREP.

Enterprise owns seven rental facilities throughout Montana, each comprised of office space and a washing garage, as well as one main office in Helena. MREP experts visited all eight facilities to assist in identifying cost-effective efficiency measures for each building. The recommended measures include installing programmable thermostats for office spaces, insulating gaps in exterior doors, especially under garage doors, and upgrading lighting to LED.

PROGRAMMABLE THERMOSTATS

Programmable thermostats are simple to install and inexpensive, yet they can result in significant energy cost savings by reducing the set temperature during times when offices are closed, such as evenings and weekends. Five of Enterprise’s eight offices are recommend to install these thermostats.

  • Annual energy savings: 1,180 therms
  • Annual cost savings: $720
  • Projected cost: $160
  • Simple payback with energy savings: 0.22 years

DOOR INSULATION

A number of exterior doors have gaps present, allowing air to flow into the space and negate the heating or cooling from the HVAC systems. Fortunately, there is a simple solution: applying stick-on foam to doors to fill the gaps and help maintain comfort levels in interior spaces. Reducing drafts can also decrease the use of space heaters among office employees, further increasing energy savings.

Garage doors in car-washing areas had large gaps between the doors and concrete floors. The thermal image on the right shows the gap at the bottom of the garage door as it lets cold air in. Adding insulation here will help reduce the need for space heaters and save on natural gas costs.

Weatherstripping is a very inexpensive and cost-effective way to prevent the escape of heating or cooled air. This measure can also be applied to windows and window sills.

LED LIGHTING

Many of Enterprise’s offices and garages had fluorescent T8 tube lighting, and upgrading these to LED will save a significant amount of energy. MREP’s lighting analysis resulted in the following costs and savings:

  • LED replacement cost: $8,332
  • Utility incentives: $3,416
  • Net cost: $4,917
  • Annual energy savings: 43,344 KWH
  • Annual cost savings: $5,285
  • Simple payback with energy savings: 0.93 years

SOLAR PV SYSTEM

Enterprise Holdings also expressed interest in a solar photovoltaic (PV) system for its Helena and Great Falls facilities. MREP analyzed roof- and ground-mounted systems for the Helena facility and found that a roof-mounted system would be limited to 10.4 kW, which would produce 18% of the building’s electricity usage. A ground-mounted system would allow the maximum size of 50 kW and produce 76% of the building’s electricity usage. The Great Falls facility could accommodate a 10-kW roof-mounted system that would produce about 60% of the facility’s usage.

Currently, there is a 30% tax credit of the cost of the system to any tax paying business. MREP recommended that Enterprise take advantage of this credit while it is still in place as it is set to phase out starting in 2020.

Draught Works Brewery

A Montana brewery could save more than $4,000 each year on energy costs by implementing the recommendations of a Montana Resource Efficiency Program (MREP) audit.

Draught Works is a brewery in Missoula, Montana, that resides within a historic brick building built in 1931. The building contains one large room that consists of a taproom and brewery, located on opposite ends of the building. The Montana Resource Efficiency Program (MREP) conducted a detailed audit that focused on energy and water conservation, renewable energy, and operational improvements.

Current heating and cooling equipment includes a geothermal heat pump system (including well pump and circulation pumps). There are also two unit heaters. Ventilation is provided by two heat-recovery ventilators. Domestic hot water is provided by a high-efficiency instantaneous unit to sinks and a dishwasher. There is a 24′ x 24′ cooler inside the building and another refrigeration system for the beer-dispensing lines. The brewery upgraded its lighting LED in 2016.

Audit recommendations include installation of occupancy sensors, ECM motors (brushless, permanent magnet motor integrated with an electronic control module), walk-in cooler evaporator fans, compressed-air system testing and maintenance, and installation of heat recovery-glycol chillers.

The economics associated with the energy-conservation project are summarized below:

  • Total gross project cost: $8,525
  • Total annual cost savings: $4,282.5
  • Total utility incentive: $2,103
  • Net cost: $6,421
  • Annual energy savings: 7,406 KWh and 5,030 therms
  • Simple payback with energy savings: 1.5 years

 

Darby High School

Darby High School now has great options for energy efficiency in its heating, ventilation, and lighting systems, after an audit by the Montana Resource Efficiency Program.

The high school is a part of a school campus built in 1973 that also includes  elementary and middle schools. There is a small tunnel network below grade that is used for utilities and heating and ventilation system air supply. The building includes administration offices, classrooms, a gymnasium, and locker rooms. The school district replaced the existing natural-gas boilers with a wood boiler in 2003. Figure 1 provides an overview of the temperature and precipitation. Figure 2 illustrates electric consumption at the high school, and Figure 3 illustrates the monthly peak demand.

 

Figure 1. Darby Historical Weather Data
Figure 2. Electric Usage, 2015- 2017
Figure 3. Electrical Demand,  2015- 2017

 

 

 

 

 

Audit Findings:

There are issues with restricted return air that contribute to poor air circulation and temperature control, especially when doors are closed. This high return pressure on the air- handling unit also requires that the air-handling unit fan consume additional unnecessary electricity to operate.

Many of classroom and office heating coils in the branch ductwork in the tunnel have failed, resulting in poor temperature control in those rooms. The heating coils are likely well past their useful life, even though the controls are relatively new.  The school can replace or repair the coils to improve temperature control in the spaces.

The school can save energy in this air-handling unit by converting it to a variable-flow system utilizing a variable-frequency drive (VFD) on the fan and variable-air valves (VAV) on the ductwork to each classroom. This would allow the fan to slow down when less heat is needed and conserve fan power. This measure requires that adequate ventilation air is delivered to each space.

The school could also save energy by converting the heating hot water system to a variable flow system. This upgrade requires valve replacements and additional re-piping on the hot water system. The ventilation for this system comes from a louver in the exterior wall, which likely was originally intended to be open when the mixed air temperature could be maintained well above freezing. This would allow ventilation in all but the coldest periods, thereby protecting the downstream classroom coils from freezing. During the audit, this louver was found closed even though the return air temperature was 65° to 70°F and the outside air temperature was 37°F. Because it was not open, even partially, fresh ventilation air was not being delivered to the academic wing.

School maintenance staff and MREP auditors concluded that previous maintenance overrode the louver system and it no longer opens as designed. The outside air control should be retro-commissioned so that ventilation can be provided at all times, even in the coldest weather. This might require the addition of a preheat system for the outside air system so that the mixed air is sufficiently warmed before being introduced into the building.

In addition to these HVAC efficiency items, the school could save significant energy by converting fluorescent lighting to LED, as shown in Table 1.

Table 1. LED Conversion Project Cost, Savings, and Simple Payback

Project Annual Bill Savings Est. Project Cost Est. Rebate Net Cost KWh Savings Simple Payback
LED Conversion $11,236 $15,804 $10,110 $5,694 87,178 0.5