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Incorporate high-performance energy efficiency measures into your new multi-family or assisted living development. You can reduce energy costs for years to come and qualify for incentives that will offset the cost of your improvements.
Photo courtesy of Related Midwest
The technical guides below explain how and why you should incorporate energy efficiency strategies into your next multi-family project.
Glazing properties are important because they affect thermal comfort and control the amount of solar heat allowed into the building. The two key properties are assembly thermal conductance (U-value) and solar heat gain coefficient (SHGC). Building codes have increased minimum performance requirements, but opportunities still exist to further improve window properties without moving to costly triple-pane glazing.
Many manufacturers offer low-cost residential and multi-family commercial glazing systems that exceed code minimum properties. Cost and energy savings can be balanced by specifying good double-pane glazing units and thermally broken frames. Higher-performing glazing may reduce HVAC system size and cost, and may eliminate the need for perimeter heating systems. Costs for better glazing can be comparable to code-minimum glazing, making payback immediate.
Window properties can have a big impact on occupant comfort, daylight harvesting potential and overall quality of space. Selecting higher-performance glazing can improve the thermal comfort in areas adjacent to windows. Spectrally selective coatings allow transmission of visible daylight but limit solar heat gain.
Many excellent glazing products are available. Special attention should be given to framing systems, since overall system performance matters most. Good quality frames limit thermal transmission and air infiltration.
South, east and west glazing should be specified with an SHGC of 0.35 or less. Note that center-of-glass (COG) U-value is not the same as assembly U-value, which takes into account both COG U-value and frame conductance.
A thermal modeling report should be completed for curtainwall systems to determine the assembly (glass and spandrel) U-value. For factory-built windows, confirm assembly U-value and SHGC meet requirements based on National Fenestration Rating Council (NFRC) data.
It's about more than choosing LEDs. Yes, LED light fixtures provide higher-quality illumination and use less energy than other types of lighting. Reduce lighting power without sacrificing functionality by decreasing total installed wattage through thoughtful design and consideration of necessary light levels.
High-efficiency LED lights have longer lifespans and can significantly reduce or even eliminate maintenance costs. No additional cost is required for disposal of hazardous materials, as is needed with fluorescents.
By using LED fixtures and light levels consistent with Illuminating Engineering Society of North America (IESNA) recommendations, a best practice interior lighting power density does not cost significantly more than meeting the baseline with fluorescent fixtures. Simple paybacks are often less than 3 years.
QUALITY
LED lighting offers better glare control and uniformity than alternatives. High-quality lighting enhances other design elements and contributes to marketing, leasing and unit sales.
Improved lighting quality is linked to improved occupant satisfaction and health. Lower installed lighting power density contributes less waste heat, which can result in an ancillary benefit of reduced cooling costs in summer.
Specify LED fixtures and light levels consistent with IESNA recommendations. Target a lighting power density of 0.43 W/sf or less for all corridors, stairs, lobbies and other common areas. Select fixtures meeting DesignLights Consortium® Qualified Projects List (DLC QPL) premium performance requirements:
Consider providing hardwired fixtures for all parts of dwelling units, rather than just switched receptacles for living and sleeping areas. Hardwired fixtures reduce the need for tenant-installed lamps and increase energy savings potential.
A thoughtful lighting control scheme reduces energy use and increases lighting lifespan without affecting the comfort or productivity of building occupants. Even the most efficient design can benefit from good lighting control strategies. Inherent dimmability of LEDs allows for lighting reduction as an alternative to shutoff controls.
Lighting controls are already required in many common area spaces. Expanding the use of controls to include corridor spaces and stairways is a low-cost energy efficiency upgrade. Implementing a more aggressive control strategy in other common areas where already required by code adds little to no additional first cost.
Implementing best practice lighting control strategies in corridors, stairs, and other common areas typically pays back in 6 years or less. Longer lamp life reduces maintenance cost and improves economics further.
Unlike fluorescent lights, which have a reduced lifespan with frequent switching, LED lights are not adversely affected by frequent switching. In fact, LEDs last longer with a more aggressive controls strategy due to reduced run-hours.
Occupancy-based control for corridors, stairways and other spaces is becoming more common. It is required for buildings seeking to comply with ASHRAE Standard 90.1, and many reliable products exist for these applications. When properly designed and commissioned, controls are responsive to occupants and contribute to perceptions of safety and quality.
Design lighting controls with more granular zoning to increase savings potential and to allow for short time-delay-to-off following vacancy without impact to functionality.
Alternatively, implement multi-level or stepped shutoff control of light output, such as a 50% reduction within 10 minutes of vacancy, followed by an 80% reduction within an additional 5 minutes of vacancy.
Consider networked lighting controls, which allow for advanced lighting control strategies such as task tuning to further increase savings, functionality and ease in making changes.
As with interior lighting, exterior lighting efficiency is about more than just choosing LEDs. Thoughtful design addresses any security concerns strategically while not exceeding recommended light levels. Designers should incorporate high-efficacy fixtures from the array of LED products on the market.
High-efficiency LED lights have longer lifespans and can significantly reduce maintenance costs. Additionally, instant on/off control reduces need for supplemental life safety lighting components.
Buildings that implement best-practice efficient exterior lighting can expect to save 2–4% of energy costs, with payback in one year or less due to low initial cost.
LED lighting offers better glare control and uniformity than alternatives, contributing to improved facial and object identification. Customer satisfaction and comfort can be achieved with lower installed lighting power designs, while reducing light pollution and trespass. Safety and security concerns can be met without exceeding desired light levels. The inherent dimmability of LED fixtures provides potential for tuning light levels post-installation, providing opportunity for additional energy savings.
Compare your project's watts per square-foot of parking and drive area and watts per linear foot of doors to the recommended targets in this guide.
Do not exceed Illuminating Engineering Society of North America's (IESNA) recommended light levels (0.2 to 0.5 foot-candles for parking lots) for the building's exterior lighting zone.
Confirm any specific security issues requiring enhanced lighting.
Target selection of DLC QPL premium performance requirements:
Even the most efficient lighting designs can further benefit good lighting control strategies. Dim building-mounted and pole-mounted fixtures during nighttime hours with little to no activity while turning off landscape and accent lighting.
https://betterbuildingssolutioncenter.energy.gov/sites/default/files/attachments/exterior_lighting_savings.pdf
Energy associated with water heating can account for up to a third of a multi-family building’s total energy consumption. Perhaps the most effective way to reduce water heating energy consumption is to first reduce hot water demand, specifically through the installation of low-flow faucets and showerheads. EPA’s WaterSense program provides an easy way to find fixtures that perform effectively at lower flows.
Low-flow plumbing fixtures typically are low-cost measures. The full installed cost (including labor) is around $8 for faucet aerators and $12 for showerheads, with a typical lifespan of 10 years. The incremental cost going from baseline to low-flow is even less. The simple payback for low-flow hot water fixtures can be less than a year just considering energy cost savings, not including water savings.
These strategies have the additional benefit of reducing potable water usage which, like energy efficiency, is a key component of sustainable building design. This is recognized by building rating systems and can be part of a building’s environmental brand and marketing. In addition to water heating fuel savings, reducing potable water consumption also saves significant energy expended in purifying, distributing and subsequently treating water, an important part of the total energy picture of the built environment.
Low-flow plumbing fixtures have wide market penetration and are available in many styles. Look for WaterSense-labeled products when specifying plumbing fixtures. Consider sink faucets with sensor-actuated valves to further reduce water waste and promote a sanitary environment.
Multi-family dwelling units can use a variety of air conditioning (A/C) and heating equipment. A/C systems are rated for energy efficiency with a Seasonal Energy Efficiency Ratio (SEER). Heat pumps in heating mode are rated by Heating Seasonal Performance Factor (HSPF). Higher SEER or HSPF numbers indicate better efficiency. A/C and heat pump units should be rated by the Consortium of Energy Efficiency (CEE) as Tier 1 or higher. If the equipment type is not listed by CEE, equipment should be ENERGY STAR certified wherever possible.
Higher-efficiency A/C Units and heat pumps are a low-cost energy efficiency upgrade. Units may cost $100 to $300 more per unit, with a typical incremental cost of less than $0.20/gsf.
Cooling electricity cost is reduced by 7% or more in a typical application, resulting in a simple payback of approximately 2 years.
Heating fuel use is reduced by 10–15% or more in a typical application when using condensing furnaces or boilers.
Condensing boilers cost 20–25% more than a standard boiler and should generally have a simple payback within 4 to 5 years.
Condensing furnaces can cost $20 per MBH more than regular furnaces, with a typical payback period of 6 to 8 years.
The most efficient A/C and heat pump units have variable speed compressors and fans with integrated controls. These systems can match the exact cooling load required, creating a more comfortable space while also saving energy compared to staged compressors, which tend to overcool the air at part load conditions.
If feasible, more centralized systems, such as VRF or water-source heat pumps, should be used to improve efficiency and recover heat between zones that are simultaneous heating and cooling.
Condensing gas-fired heating technology uses a heat exchanger to capture heat from the waste vapor in the combustion process.
To take full advantage of a condensing boiler system, the hot water return temperature should be as low as possible. For condensing boilers, the hot water return temperature should be kept as low as possible to maximize energy cost savings.
Properly maintaining the products of combustion is an important part of a condensing furnace or a condensing boiler. Check with your designer about proper disposal of condensate water.
Specify or schedule an A/C unit that meets CEE High Efficiency Commercial Air Conditioning and Heat Pump Initiative Tier 1 minimum efficiency ratings. For even better performance, specify rooftop units at CEE Tier 2, CEE Advanced Tier, or even higher SEER or HSPF.
Centralized heating and cooling equipment, or equipment not listed in CEE, should be 10% better than code minimum efficiency.
Specify condensing furnaces or condensing boilers with a minimum gas heating efficiency of at least 92%. Specify higher efficiencies for even greater savings. Condensing heating equipment has a maximum efficiency of around 96%.
Fans are used in multi-family dwelling units for multiple purposes including range hoods, bathroom exhaust and dryer exhaust. Specify individual bath and utility fans with no less than 6.0 cfm/W. Specify range hoods with no less than 3.5 cfm/W. Specify fans over 1 HP with no more than 0.82 W/cfm (constant volume) or no more than 1.11 W/cfm (variable volume).
Simple bathroom fans can be upgraded to more efficient bathroom fans for as little as $40 per fan. Implementing higher-efficiency fans can payback in 4 years or less. Higher-efficiency fans can add value to your project—as much as $0.05/gsf net present value.
Energy-efficient fans tend to be quieter than alternatives.
The most energy efficient fan is one that is off. Use integrated controls that can shut off small fans when not in use.
To reduce speed, small fans should have electronically commutated motors (EC motors) and larger fans should have variable frequency drives (VFDs). Any air exhausted from a building must be replaced by air from the outside, either from a makeup air unit or through windows and doors. Implementing ventilation controls with the exhaust and makeup air unit can significantly reduce the heating and cooling costs.
Specify the following minimum fan efficacy on your drawings:
Consider true kitchen exhaust hoods ducted to the outdoors to improve indoor air quality.
Adequate wall insulation and a tight envelope provide a thermal barrier between the conditioned interior of a building and the outdoor conditions. Ensuring that wall insulation meets energy code requirements. Reducing infiltration improves occupant comfort and minimizes the need for mechanical heating and cooling.
A high-performance envelope will reduce annual energy consumption of the building. In some cases, it may reduce the sizing of HVAC equipment by reducing peak loads. This is usually in conjunction with installing improved windows.
In addition to energy benefits, an improved envelope leads to a more thermally comfortable space for occupants. A well-designed thermal envelope discourages mold growth and other potential moisture issues, contributing to good air quality and health.
Installing continuous insulation to comply with code requirements and increasing envelope tightness to reduce infiltration typically have a payback of less than four years. The thermal comfort, health and energy savings benefits continue for decades over the life of the building.
Designers should specify that the vertical envelope feature a continuous layer of at least R-5 insulation. The overall assembly U-factor, C-factor or F-factor should meet or exceed the requirements in IECC 2018 based on the area weighted average (UA method) of the entire envelope component, not just the representative assembly of the clear field. Thermal bridging at floor-to-wall interfaces, wall-to-corner interfaces, slab edges, window bucks and balconies must also be accounted for.
Continuous insulation may be rigid foam—extruded polystyrene (XPS), expanded polystyrene (EPS) or polyisocyanurate (polyiso)—though some building codes now require exterior insulation to be rigid mineral wool insulation boards or other non-flammable material types. Batt insulation or spray foam may also be used in wall cavities of masonry, wood or steel-framed wall systems, but those applications require careful consideration of moisture transport.
Specify envelope infiltration no greater than 0.3 cfm/sf of envelope area when tested at 50 Pascals (Pa) (or 0.4 cfm/sf at 75 Pa). Building tests should comply with ASTM Standard E779-10, as applicable, using a whole-building blower door test, a floor isolation blower door test or compartmentalization testing of no fewer than seven individual dwelling units.
Energy associated with water heating can account for up to a third of a multi-family building’s total energy consumption. Along with specifying low-flow fixtures, efficient water heating equipment can reduce this energy significantly.
Due to the significant water heating load associated with multi-family buildings, energy conservation measures typically have attractive payback periods. For in-unit water heaters that meet ENERGY STAR requirements, expected payback periods are around 8 years. For central gas systems, expected payback is around 7 years.
Quality water heating devices and system designs deliver hot water to residents quickly while reducing energy consumption.
Increasing insulation levels on domestic hot water piping is another way to save energy. IECC 2015 requires that most pipes used for domestic hot water be insulated to only R-3 in low-rise multi-family and up to R-5 in most high-rise multi-family applications. Increasing pipe insulation saves on water heating cost, especially for recirculating systems.
Designers and owners should specify efficient in-unit water heaters that meet or exceed ENERGY STAR requirements. If a central system is used, specify a thermal efficiency of at least 90%. For recirculation systems, minimize return water temperature to ensure that boilers operate in condensing mode at all times.
In all scenarios, set the domestic hot water supply temperature to 120°F, which is safe practice according to the Consumer Product Safety Commission.
The ENERGY STAR program, developed by the U.S. Environmental Protection Agency, sets water and energy efficiency performance standards for appliances. Appliances with ENERGY STAR certification use up to 33% less energy and 40% less water than conventional appliances, without affecting functionality or performance.
Additional cost for ENERGY STAR appliances ranges from $0 to $190 per unit, which is typically recovered in 2-5 years depending on appliance type.
ENERGY STAR appliances are certified by third parties and are subject to ongoing testing and verification.
In many cases, energy-efficient appliances also operate more quietly than alternatives, contributing to overall comfort and space quality.
The ENERGY STAR logo will be included on the product spec sheets and/or brochures for any certified appliances. Click here for a listing of certified products.
Within appliance categories, there are additional choices that can further improve energy efficiency:
US EPA, September 2012. "Choose ENERGY STAR Certified Appliances." Brochure. EPA 430F-12-004
2019 Illinois Statewide Technical Reference Manual for Energy Efficiency. Version 7.0. Volume 3: Residential Measures. September 2018.
Advanced thermostats, also known as "smart" thermostats, include connected features to control heating and cooling based on occupancy, weather, individual preferences or historical trends. This goes beyond simple manual thermostats that only account for temperature setpoints, or programmable thermostats that run on a schedule. Advanced thermostats are easier to program than other thermostats, and they give residents added convenience, insight and control.
Incremental cost for advanced thermostats can vary significantly based on the specific model selected, however the average is around $125 per thermostat. Advanced thermostats save about 6% of heating and cooling energy compared to standard programmable thermostats, resulting in simple payback of about 4 years.
When selecting a smart thermostat, consider these additional features:
Eligible smart thermostats are listed on the ENERGY STAR website.
ENERGY STAR Certified Smart Thermostat Fact Sheet
Deciding whether to include roof-mounted solar photovoltaics (PV) in a new building design can be complicated and require input from multiple stakeholders. However, a few simple choices during design can ensure the building is solar-ready and can reduce retroactive solar construction costs by up to 60%.
Solar PV systems perform best when shading from vegetation and neighboring structures is minimized. To the extent possible, site buildings in the least-shaded portion of a lot, designating shady areas for parking and driveways.
Rooftop solar systems weigh three to six pounds per square foot, so a solar-ready roof must be able to support this. Minimizing the amount of rooftop equipment and placing all such equipment in a centralized area on the north side of the roof will maximize space and minimize shading for a future solar energy system.
To accommodate photovoltaics (PV), the electrical system must have conduits routed from the roof to the main electric panel. Space should be left near the panel for such equipment as inverters, controllers and switches.
In all as-built drawings and submittals, be sure to record details about design choices made with solar in mind. Consider including details on the code sheet.
If the approximate size and location of a building is known, the ComEd solar calculator can be used to estimate system power and energy production.
On the site plan, indicate the portion of the roof designed to accommodate future PV panels. Provide sufficient roof structure to support this load.
Size the electrical room to accommodate future solar PV equipment.
Visit ComEd.com/Solar to determine if solar is right for you.
