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ENERGY STAR GOESMULTIFAMILYAlong with beautifully designed brickwork and a landscapedbackyard with a children’s play area, residents of 1212 MLKApartments can enjoy affordable apartments, low energy bills, and healthy indoor environments.

by MARC ZULUAGA andGAYATHRI VIJAYAKUMAR

1212 MLK Apartments contains 54 units of affordable housing: 10 studios, 15 one-bedroomapartments, 28 two-bedroom apartments, and 1 three-bedroom apartment. A dozen energy efficiencymeasures have been implemented. The building is the first to earn Energy Star status through a pilotprogram for multifamily buildings.

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mance and markUp until recently,high-rise mul-

tifamily buildings have notbeen able to reap the perfor-

eting benefits associatedwith the Energy Star label.That changedwhen, earlier this year, EPA launched itspilot program for Energy Star multifam-ily homes in New York,Wisconsin, andOregon. As the New York Energy andResearch Development Authority(NYSERDA) has taken a national lead-ership role in developing the pilot, it isperhaps not surprising that New York isthe location of the first of the pilot pro-gram buildings to be completed. Builtby Dunn Development Corporationand Beulah HDFC, Incorporated, 1212MLK Apartments is a six-story buildingon Dr. Martin Luther King, Jr., Boule-vard in the Highbridge neighborhood ofthe Bronx.The first tenants moved induring the summer of 2006.

The company we work for, StevenWinter Associates, served as an energyconsultant for the project and assistedDunn Development in meeting theprogram requirements. NYSERDA isusing data from the pilot to establish theup-front cost of efficiency and to setcost-effective efficiency goals for futureconstruction projects. The experiencegained from the pilot project in NewYork will help EPA generate standardsfor Energy Star labeling of high-risemultifamily buildings nationally.

Affordable Housing at Its Best

1212 MLK Apartments contains 54units of affordable housing:10 studios,15one-bedroom apartments, 28 two-bed-room apartments, and 1 three-bedroomapartment. In addition, the first floor hasa community room with a kitchen andbathroom,a laundry room,utility rooms,and three offices. Residents and theirguests can enjoy a beautifully landscapedbackyard with a children’s play area andplenty of benches. The building totals51,000 ft2, including apartments, com-

mon areas, and other first-floor spaces.The brick and concrete masonry unit(CMU) block walls rest on a crawlspacefoundation.The boiler room is locatedon the roof.

In order to meet the NYSERDAprogram requirements, 1212 MLKApartments includes a dozen energyconservation measures (ECMs) thatwere incorporated into the design inorder to reduce the modeled whole-building energy use by 20% comparedto a baseline ASHRAE 90.1-2004-compliant building (see Table 1).

The building walls are insulated withR-4.3 Roxul 1-inch rigid (mineralwool) insulation and R-13 fiberglassbatts within 3 1/2-inch interior steelframing. The rigid insulation, placedbetween the steel studs and the CMUblock wall, minimizes thermal bridgingthrough the steel. In New York City, formultifamily buildings with more thanfour units, the Energy ConservationConstruction Code of New York Staterequires a continuous layer of R-3 insu-lation with metal framing.However, thisrequirement is usually ignored, resultingin a standard practice for new construc-tion that does not address thermalbridging through steel studs.

The windows are low-e, argon-filledaluminum frame with a thermal break,

resulting in an assembly U-value of0.44.These windows also feature a cus-tom-made removable panel below astandard double-hung unit. During thesummer, an insulated replacement panelwith a cutout for a window A/C unitwill be installed in the bottom sectionof those windows where tenants desirewindow air conditioning.The panel forthe A/C is replaced with a windowpanel during the winter to provideextra light. The developer decided totry this new window design approachin order to avoid air conditionersleeves, which are prone to air leakageand limit the potential efficiency ofA/C equipment.

Two 87% efficient, direct-ventLochinvar boilers meet heating needs—

a significant improvement overconventional 80% efficientatmospheric equipment. Theseboilers have a fully modulatingfiring rate of 25%–100% and areused in combination with two119-gallon indirect storage tanksto meet domestic hot water(DHW) needs efficiently.Whilecombustion efficiencies of90%–95% are possible with con-densing boilers, actually achievingthis performance level requires aboiler return water temperaturethat is low enough to allow forcondensation. The boiler returnwater temperatures of140ºF–180ºF in a standardhydronic baseboard loop will not

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yield condensation in thecombustion stack. In thistype of conventionalapplication, a condensingboiler will result in com-bustion efficiency com-parable to that ofdirect-vent equipment.

It is possible to lowerreturn water tempera-ture enough to takeadvantage of condensingequipment by increasingthe radiation output ofthe hydronic loop withlarger baseboard units.The cost-effectiveness ofthis type of approachwas not evaluated,

although it may represent thenext logical step in improvingheating-plant performance.

More than any other factor,mechanical ventilation drives theheating load in new multifamilybuildings in New York City.Small apartments comwith strict exhaust requirements in the city’sbuilding code result inrelatively high mechani-cal air change rates. At1212 MLK Apartments,the ventilation systemwas designed to mini-mize overall apartmentair change rate while stillmeeting code. Thedesign exhaust ventila-tion rate for all bath-rooms is 50 CFM. Mostkitchens qualified as “super kitchens,”which are greater than 59 ft2 floor areawith a pass-through to an adjacent roomwith operable windows, and did notrequire mechanical ventilation.The stu-dio kitchens are smaller than 59 ft2 andcan’t use the living area as a pass-throughto get to an operable window. Indeed,the living area is also a sleeping area in astudio apartment. The small kitchenstherefore required a provision for 120CFM of mechanical ventilation (notnecessarily continuous). Ironically, thesmallest apartment requires the mostventilation by code.

binedCFM

These ventilation requirements aremet by a central exhaust system withroof-mounted exhaust fans connected toduct riser shafts with takeoffs at each floorfor bathroom and kitchen exhaust grilles.Bathroom doors are undercut to providefor makeup air. As an improvement onthis standard-practice ventilation system,1212 MLK Apartments also incorporatesAldes Constant Air Regulator (CAR)dampers at each bathroom exhaust pointin order to assist in balancing exhaust airflows from floor to floor and from seasonto season. CAR dampers incorporate asilicone bulb that expands when the pres-

sure drop across the damperexceeds 50 Pa in order to regulateair flow. At 1212 MLK Apart-ments, the CAR dampers are inte-grated with an exhaust grille andfire damper assembly.

High-efficiency fluorescentlighting is used throughout thebuilding.Apartments feature wallsconces with four-pin CFL bulbs(2 x 13W),T-8 lamps with elec-tronic ballasts for kitchens (2 x32W), and 55W fluorescents forthe bathrooms.Overhead fixturesin public corridors are CFLs (2 x26W), also with electronic bal-lasts.To further minimize electric-ity bills, occupancy sensors wereinstalled throughout the offices,community room, and janitorclosets. In each public corridor,ceiling-mounted long-rangeoccupancy sensors are wired to apower switch pack (PSP) thatturns off every other overheadlight fixture when these spaces arenot being used. The overhead

ps that are not controlled the PSP are designatedemergency fixtures withbattery pack backup forpower failures.

light lamby

CompetitiveCosts

SWA compared thespecifications and com-ponent costs for a base-line building to theMs implemented in theEC

building (see Table 1).The baseline build-ing specifications were determined usingAppendix G of ASHRAE Standard 90.1-2004 along with a few minimum-perfor-mance standards required by NYSERDA.Since ASHRAE 90.1 is a relatively strin-gent standard, baseline requirementsexceed standard practice for New YorkCity. Pegging the program to a nationalstandard will eventually allow for the nor-malized comparison of buildings in differ-ent parts of the country, as is done withsingle-family homes. From a developerstandpoint, this baseline approach doesnot give credit for those specifications that

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The building walls are insulated with R-4.3 Roxul 1-inch rigid (mineralwool) insulation and R-13 fiberglass batts within 3 1/2-inch interiorsteel framing. The rigid insulation, placed between the steel studsand the CMU block wall, minimizes thermal bridging through the steel.

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Table 2. Simulation Summary—1212 MLK Final design Baseline simulation simulationAnnual energy cost, all fuels $65,000 $52,000Electricity consumption 262,000 kWh/year 210,000 kWh/yearAll other fuels consumption 1,700 MMBtu/year 1,300 MMBtu/yearTotal estimated energy 2,600 MMBtu/year 2,000 MMBtu/yearconsumption

Estimated Annual Energy Costs, MLK Apartments

Lighting: $14,800(29%)

Appliances: $19,400(37%)

Heating: $8,000(15%)

Hot water: $7,200 (14%)

Cooling:$3,400(5%)

Estimated Annual Energy Costs,Baseline Building

Appliances: $24,900(39%)

Lighting: $17,100(26%) Heating:

$11,200(17%)

Hot water: $8,900(14%)

Cooling: $2,300(3%)

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Figures 1 and 2. Installing four high-efficiency front-loadingclothes washers in the first-floor laundry room was the most cost-effective ECM. Both electricity and hot water use of clothes washersis reflected in the “Appliances” wedge of the pie charts.

1212 MLK Apartments also incorporates AldesConstant Air Regulator (CAR) dampers at eachbathroom exhaust point. In order to regulate airflow, CAR dampers incorporate a silicone bulbthat expands when the pressure drop across thedamper exceeds 50 Pa.

are found in ASHRAE 90.1 buthave not been included in adeveloper’s previous projects.However, the goal of this pro-gram is to raise the bar andencourage the construction ofbetter buildings.

Whole-BuildingEnergy Performance

Energy savings were evaluatedby comparing simulations of thebuilding to the baseline building.All simulations and projectedenergy savings have been devel-oped using TREAT, Version3.0.19 software.The final designresulted in a 20% reduction inestimated energy consumptioncompared to the baseline build-ing. Put another way, the energyperformance of 1212 MLKApartments is 20% better thanthat of an already pretty good(ASHRAE 90.1-compliant)building (see Table 2 and Figures1 and 2). Projected costs arebased on energy prices of$0.15/kWh and $1.49/therm.

Installing four high-efficiency front-loading clothes washers in the first-floorlaundry room was the most cost-effectiveECM.Both electricity and hot water useof clothes washers is reflected in the“Appliances” wedge of the pie charts.Based on an assumption of nine loads oflaundry per day per washer,upgrading theModified Energy Factor (MEF) of equip-ment from 1.04 (baseline) to 1.89 (asbuilt) will result in a savings of $5,127 peryear.As is typical in New York City,wash-ers and dryers are leased, which meansthat one of the most important ECMdecisions was not finalized until the veryend of the construction process.

Installing top-of-the-line OTIS Gen2“machine room-less” elevators was theleast cost-effective ECM. Using an on-line Otis Energy Expense calculator,SWA estimated a savings of 800 kWhper year.This savings estimate was basedon an assumption of 360 rides per dayfor the building that was derived fromresearch done by Henry Gifford inanother six-story New York City build-

ing.These results indicate that in a six-story multifamily building, state-of-the-art elevator technology is not justifiedbased on energy savings alone (there are,of course, maintenance and reliabilitybenefits associated with new elevatortechnology).

Next Steps

Now that the 1212MLK Apartments areoccupied, SWA will col-lect utility bills for a yearin order to provide a real-ity check on simulationresults and to providefeedback to Dunn Devel-opment Corporation andBeulah HDFC, Incorpo-rated, on building perfor-mance. In addition, withfunding from HUD’sPartnership for AdvancingTechnologies in Housing(PATH) program, SWAalso installed long-termmonitoring equipment to assessventilation system performancein one line of six apartments.

Dunn Development Corpora-tion has already incorporatedsome details from 1212 MLKApartments, such as the 1-inchRoxul insulation, into its standardspecifications for future projects.SWA hopes that information fromthe field monitoring will prove

useful, both by giving the developerconfidence in the performance of newbuilding systems and by helping toidentify opportunities for furtherimprovement.

Marc Zuluaga and Gayathri Vijayakumar areengineers at Steven Winter Associates.

Steven Winter Associates would like to thankMike Colgrove at NYSERDA for his work indeveloping the pilot program and Mark Zimetat Dunn Development for his open mindthroughout the whole process.

FOR MORE INFORMATION:

For more on 1212 MLK Apartments, goto www.dunndev.com/L3/mlk.html.