casestudy
project
cost/savings•••
Billings, Montana
History
Total Cost: $35,475
NWE Incentive: $5,132
Completion Date: February
Boise Cascade Warehouse
2009
Customer Cost: $30,343
Annual Savings (kWh): 167,951
kWh
Monthly Demand Savings: 26.51
kW
Simple Payback with Energy Savings for
the Customer: 2.34 Years
project
features•••
• Removal of (47) 400 watt metal
halide fixtures that operate
approximately 100 hours per week
• Installation of (94) 6 lamp 32 watt
T8 fixtures
• Installation of (94) integrated,
passive infrared occupancy sensors
• Improved foot candle readings with
additional lights from 3 - 5 (fc)
before to approximately 20 (fc) after
• Estimated lighting electricity usage
decrease of over 60% (based on
modified base case of (94) 400 watt
metal halide fixtures)
• Quality lumen output within
building’s ambient temperature
range
Boise Cascade’s distribution warehouse, located in Billings, is a 65,000
square foot facility that houses a variety of building products for
distribution to vendors. A combination of mobile equipment and foot
traffic occurs within the warehouse, and company management
estimates that lighting is required within the structure approximately
100 hours per week.
Prior to the lighting upgrade, not only were less efficient metal halide
lamps being used, but analysis by NorthWestern Energy Efficiency
Contractors documented light level readings considerably lower than
recommendations suggested by the Illuminating Engineering Society
(IES). As a result, the retrofit addressed both the efficiency and
illuminance within the building.
In the funding agreement,
NorthWestern Energy agreed
to provide incentives for all
of the new fixtures required
to raise the light to adequate
levels – as opposed to paying only for replacement of the
existing metal halide lamps.
Lighting Upgrades
Boise Cascade chose to replace the metal halide lamps with 6 lamp
32 watt T8 fixtures, fitted with occupancy sensors. The increase in the
number of fixtures also involved a planned layout to address specific
traffic corridors within the warehouse space. The fixtures were mounted
with passive infrared occupancy sensors with adjustable timers.
The IES notes that fluorescent lamps, as a linear source, offer
potentially more uniform lighting, less shadows and less glare than
metal halide lamps. This is an important feature for multi-use
warehouse spaces.
In a fixture-by-fixture comparison, the T8 units use approximately 40%
of the electricity of 400 watt metal halide fixtures. Additional savings are
realized through the use of the occupancy sensors. Prior to the retrofit,
the metal halide fixtures were left on continuously because of the ten
minute re-strike time. This included lunches and planned breaks when
the building was unoccupied.
The T8 units are also conducive to planned “re-lamping” – they have
considerably lower lumen depreciation than metal halide lamps, as
well as a predictable lamp life. Therefore, cleaning and replacement of
lamps on a scheduled basis can significantly reduce the lighting
maintenance costs of the facility.
T8 Lamps as Replacements for Metal Halides
Metal halide lamps can emit up to 36,000 initial lumens, but many factors
must be included when calculating the “useful” light of the lamp and fixture.
The fixture body most frequently used in metal halide applications is
characterized by a spun reflector and lens. This configuration leads to an
overall fixture efficiency of between 60 and 70%. Comparatively, T8 high bay
fixtures usually have between 80 and 90% fixture efficiency.
Of primary importance when comparing metal halides to T8s is the lumen
depreciation. Metal halide lamps experience a steep depreciation in the first
40% of their life, followed by a steady decline until the end of the lamp’s life.
Conversely, T8 lamps experience only a 5-7% depreciation during the lamp’s
life. After approximately 4,000 hours, most 6 lamp T8 fixtures produce more
lumens than 400 watt metal halide lamps.
Lumen Depreciation Comparison
The Boise Cascade warehouse is
similar to other industrial and
agricultural buildings in Montana that
are insulated, but not heated. Except
in extreme weather conditions, the
interior temperature of the building
does not drop below freezing.
Most higher quality T8 lamp and
ballast combinations start down to 0˚
F without the need for a costly, cold
weather ballast.
The T8 units work well in the most
common temperature environments
found within insulated warehouse
spaces (50-80˚ F.) - and they have
lower lumen losses up to 77˚ F when
compared to T5 HO lamps.
Metal Halide vs T8 Fluorescent Lamps
40,000
Total Lumen Output
other potential
applications•••
30,000
T8 Six-Lamp Fixture
20,000
400W Metal Halide
10,000
Source: U.S. Department of Energy
28,000
24,000
20,000
16,000
12,000
8,000
0
4,000
0
Hours of Operation
6 lamp T8 fixtures also have a more natural color rendering index than metal
halide lamps, and provide slightly more foot candle output below and
between fixtures.
T8 lamps operate well in warehouse applications where inside temperatures
may be lower (similar to the Boise Cascade application). This is due to the
fact that T8s provide peak output at 77 degrees F.
The Correct Amount of Light
project contacts
and resources •••
Building Owner:
Boise Cascade
Shawn Egan (406) 652-3250
A common misconception that leads to inefficient and/or ineffective lighting
is that more light translates into higher quality light. An audit and consultation
with NorthWestern Energy Efficiency Contractors addresses not only
efficiency, but also quantity and quality. Part of the process is to determine
the appropriate light levels for an area; an exercise that showed deficiencies
in Boise Cascade’s original lighting design.
NorthWestern Energy E+ Contractors:
KEMA, Mike Horner
(800) 823-5995
Measured in foot candles, the IES recommends the following levels:
Pioneer Technical, Mitch Mihailovich
(406) 782-5177
Application
Application
Application
Reading/Writing - 50 fc
Stockrooms - 10 fc
Retail (Low Volume) - 30 fc
Office Ambient - 25 fc
Loading Docks - 10 fc
Roadways - .3 - 1.6 fc
Office Task - 25 fc
Rough Warehouse - 10-20 fc
Parking Lots - .8 - 3.6 fc
Hallways - 10 fc
Retail (High Volume) - 100 fc
Building Entrance - 5 fc
NCAT, Dave Houser, P.E.
(866) 723-8677
NorthWestern Energy:
Dave Bausch, P.E.
(406) 497-2322