SF Apartment : April 2018
A Lightbulb Moment
by Lowell Chu
February’s record-breaking low temperatures around the Bay Area had residents reaching for their overcoats, scarves, gloves and, most of all, thermostats. As outside temperatures drop, the demand for heat and hot water increases, making boilers, heaters and furnaces work overtime. In San Francisco’s older housing stock, much of this equipment is running well past its expected useful life. Indeed, such equipment was built to last, but despite that longevity, it poses a potential liability to property owners. The prospects of high utility bills, increasing maintenance costs, and reduction in resident services loom large as vintage equipment is pushed to its limits.
Often, a property owner has neither the time nor knowledge to make an informed decision on equipment replacement. Fortunately, the San Francisco Department of the Environment (SFE) has the programs and staff on standby to help with the process, from start to finish, at no cost.
SFE’s certified staff of building scientists work within the Bay Area Regional Energy Network Multifamily Building Enhancement Program (BayREN Multifamily). BayREN is a consortium of local Bay Area governments that implement energy-saving programs on a regional level in collaboration with the nine Bay Area counties. After an owner enrolls online at bayareamultifamily.org, SFE staff conducts a comprehensive site assessment, ascertaining as-built and field conditions.
Next, the owner will receive a detailed written report with recommendations, utility and maintenance savings estimates, a detailed financial analysis and next steps. The purpose of the report is to document the site visit and, more importantly, guide the owner on a path towards profitability via efficiency. Moreover, the BayREN Multifamily Program gives a rebate of $750 per dwelling unit for various projects, such as window replacement, installing insulation in roof-cap cavities and walls, steam and domestic hot water (DHW) boiler replacement, LED lighting upgrades, circulation pump upgrades, and cool roof installation.
By far, lighting upgrades and DHW boilers replacement are the most popular among property owners because those are among the most-used equipment. Whereas exterior lighting is only on during the night, common area interior lighting in multifamily buildings is on all the time. Residential hallways and stairwells, parking garages, laundry centers and emergency stairwells are constantly illuminated for fire-life safety reasons. That can add up to huge electrical bills using incandescent bulbs and fixtures, or considerable savings with the switch to LEDs.
Similarly, the DHW boiler makes hot water based on occupant schedules. Even when no one is using hot water, the boiler is working to keep up with the storage tank setpoint. These long operating hours mean that owners who upgrade to newer, more efficient DHW boilers have a very quick payback time thanks to much lower gas bills. When combined with BayREN Multifamily rebates, the simple payback on investment is often less than three years.
Therefore, more efficient lighting and boilers don’t just help the environment. With the combination of energy savings and rebates, upgrading to LED lighting and replacing old DHW boilers is also an excellent business decision.
The LED Revolution
We have come to a point in lighting’s evolution when solid-state technology, commonly referred to as LEDs (which stands for Light Emitting Diodes), has displaced a technology that has been with us for over 100 years: the incandescent filament lamp. Invented by Thomas Edison and perfected by many thereafter, the incandescent lamp deserves a requiem for its services and contribution to improving the human experience. For a while, halogens and the Compact Fluorescent Lamp (CFL) seemed poised for a takeover, but various deficiencies such as high energy consumption, a strange curly appearance, that irritating magnetic hum, and so-so light output posed little challenge for the incumbent. Then, along came the LED light and the king was suddenly usurped. LED lighting benefits include long service life, low power consumption, and accurate color rendering. In other words, LED lamps can do everything an incandescent lamp does for a fraction of the power.
Choosing the right LED lamp is not as easy as going to a big-box store and making a selection based on price-point, longevity and wattage. Additional critical performance criteria—such as Kelvin Temperature (warmth of the emitted light), beam spread (the cone of light), and Color Rendering Index (ability of a light source to reveal the colors of various objects faithfully)—require thoughtful consideration as well.
For instance, installing an LED lamp with high Kelvin Temperature (greater than 3,000K) will render a space cold, but the objects within will appear crisp and clean. An LED lamp with low CRI (less than 82) will distort colors, making reds appear orange (the classic yellow streetlamp is an example of low CRI lighting). Lighting selection should be made based on the amount of light required for the activity in the space, with careful consideration for architectural aesthetics, in addition to the performance criteria. Many SFE staffers are Lighting Certified by the National Council on Qualifications for the Lighting Professions.
As mentioned before, a typical multifamily building has continuous lighting in common areas such as residential hallways and stairwells, parking garages, laundry centers and emergency stairwells. Since these fixtures are continuously energized, upgrading to LED and adding dual-level lighting make excellent financial sense. For example, in an emergency stairwell, a 60-watt incandescent lamp is energized 24/7. This results in the use of 526-kWh annually. Upgrading to a 9-watt LED lamp provides more lighting output (lumens), but for one-fifth of the energy use—only 44-kWh annually. If an owner is paying $0.25 per kWh, the resultant annual savings is $121. Moreover, the LED bulb will last five times longer than the incandescent.
Moving to a typical parking garage, replacing a 32W four-foot T8 fluorescent lamp with a 12W four-foot T8 LED lamps will yield an annual savings of $35. At first glance, the savings is not as dramatic, but if the garage has six fixtures, that’s a total utility savings of $210 per year. Thus, because of year-long operating hours, upgrading to LED lighting in common areas makes sense both environmentally and for owners’ bottom lines.
Don’t Be Burned by Your Boiler
A typical central DHW system is quite simple and reliable. It consists of a water heater or boiler, copper distribution piping, valves, fittings, a circulation pump, a holding tank, faucets and drains. The journey from cold to hot begins at the boiler, where incoming water is heated to 180 degrees Fahrenheit and then pushed into the holding tank by a circulation pump. Inside the tank, the high-temperature water is mixed with return and cold water, resulting in 120-degree water for residents. Separately, another circulation pump on the return line is running constantly, pulling hot water through the building’s piping distribution system. This reduces wait time because when the hot-water faucet is turned, hot water is immediately available to the user.
Boiler designs and sizes vary greatly, but all DHW boilers use burners to mix air and fuel to produce combustion. The heat from the combustion is transferred to the circulating water through a heat-exchanger. Older boilers (in service for more than 20 years) typically employ atmospheric burners and copper coil heat exchangers. As the name implies, atmospheric burners rely on the atmosphere for the air needed for combustion. The burner mixes the air with the natural gas to produce a controlled flame through the center of the heat-exchanger coil. A pump circulates and pulls the water through the coil around the flame, resulting in toasty water for the holding tank. Such a boiler design has been effective and reliable. Aside from the pump, this design doesn’t have any other moving parts, so atmospheric boilers have soldiered on quietly for decades.
As concerns over flue emissions and fuel-efficiency grew, boiler manufacturers began switching to power burners. A power burner forces air into the combustion chamber with a mechanical blower (a fan) and is therefore able to mix more air with greater amounts of gas. Since the amount of air can always be controlled, excess air is eliminated and greater efficiencies are obtained. Furthermore, in the past few years, the industry has moved away from copper coil heat-exchangers and towards copper fin-tube units. As the name suggests, the tube bundles have fins, which more effectively increase the surface area for heat transfer, increasing efficiency and reducing the time to heat the water.
Since the DHW system represents a majority portion of natural-gas usage in any multifamily building, it also represents the greatest opportunity to reduce consumption and cost. For example, a recent BayREN project in the Tenderloin included the replacement of a 25-year-old boiler, rated at 80 percent efficiency, with a high-efficiency unit, rated at 90 percent. In addition to the boiler, the owner also decided to insulate all visible bare piping, upgrade the circulation pump from constant speed to variable speed (based on hot-water demand), and reduce the set point from 125 degrees to 120 degrees.
Together, the project resulted in nearly $1,000 of natural gas and electric savings. Furthermore, the BayREN Multifamily rebate reduced a significant portion of the total project cost, making for an even stronger, more compelling business case.
The conclusion of the article is underscored by fate’s irony: as I am typing in my office, I am wearing a parka because the heater in the office is defective. According to the building engineer, the electro-mechanical valve is stuck closed so, although the boiler is cooking and delivering 180-degree hot water in the coil, the valve is shut tight, eliminating any chance of heat exchange.
However, my heart and mind remain warm knowing that, since 2013, the BayREN Multifamily Program has completed projects serving over 7,000 residential units, and given $5,250,000 in rebates to San Francisco property owners. Many of these projects include both lighting upgrades and DHW boiler replacement because savvy owners leveraged the rebates and SFE staff expertise to facilitate the upgrade and replacement processes. With SFE and BayREN Multifamily Program, choosing to upgrade has never been easier, so enroll online at bayareamultifamily.org.
Lowell Chu, LC, CEM, LEED AP, is the Senior Energy-Efficiency Specialist at SFE, and has served the city’s multifamily properties for over ten years. He also enjoys spending time with his family and dog, and restoring old, rusty motorcycles.