PowerPoint Presentation

Saving Energy in Existing Multifamily BuildingsDuluth Energy Design ConferenceFebruary, 2016

Corrie BastianCenter for Energy and Environment

In accordance with the Department of Labor and Industrys statute 326.0981, Subd. 11,

This educational offering is recognized by the Minnesota Department of Labor and Industry as satisfying 1 hour of credit toward Building Officials continuing education requirements.

For additional continuing education approvals, please see your credit tracking card.

TopicsWho is CEEEnergy use in multifamily buildingsPerspective: Understanding the industryRetrofit highlightsEnergy impactMarketability Ensuring success: I, O & M best practices

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Who is CEEThe Center for Energy and Environment (CEE) is a nonprofit organization that promotes energy efficiency to strengthen the economy while improving the environmentWe conduct research and develop programs so that:Businesses operate more efficiently and profitably;Government agencies and nonprofits spend less on facilities and functions;Utilities achieve their energy-efficiency goals at least-cost; andHouseholds save money and improve comfort.

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The Center for Energy and Environment (CEE) is a nonprofit organization that promotes energy efficiency to strengthen the economy while improving the environmentWe conduct research and develop programs so that:Businesses operate more efficiently and profitably;Government agencies and nonprofits spend less on facilities and functions;Utilities achieve their energy-efficiency goals at least-cost; andHouseholds save money and improve comfort.

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What we doEnergy Program Design and DeliveryEngineering ServicesPublic PolicyLending CenterInnovation ExchangeResearchEducation and Outreach

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CELast year was CEEs 35 anniversary. Since beginning, working in energy efficiency research, Focused on practical and cost-effective energy solutions that really workAre field tested in real buildingsOur research informs our programs

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CEE multifamily experienceFacility assessments of over 2,000 buildings in MinnesotaCompleted over 20 research projects

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CEE has been involved in MF since early 1980sStarted w research on boiler controls and identification of other opportunities (study published 1984)Ran programs in MN, also involved for a while with Focus on Energy.

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Current multifamily research projectsCondensing boiler optimizationMultifamily ventilation optimizationDemand Controller recirculation loop controlsMultifamily aerosol envelope air sealingIndoor pool optimization

All funded through the MN Department of Commerces Conservation Applied Research and Development grant program.

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We are involved in CARD grant research funded through the Division of Energy Resources.Were also involved with a benchmarking pilot, through a company called EnergyScoreCards. We have about 500 MF bldgs throughout the state enrolled in this. The idea is well see if providing MF building owners and managers with a benchmark of their energy usage, compared to similar buildings, will provide energy savings in itself, sort of like an OPOWER for MF buildings.

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Current multifamily energy efficiency programsEnergy Star multifamily 3rd party verifierOne Stop Efficiency Shop lighting program with Xcel Energy Multifamily Energy Savings program with MN Energy Resources

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Understanding multifamily buildings

Now Ill talk about some characteristics of MF sector relevant to energy use.9

What we know about multifamily buildingsMultifamily buildings are a tough energy efficiency nut to crack

Why?Split incentive / diverging interests between resident and ownerLots of players in the orchestraPerception that technical challenges outweigh financial benefits

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Resident may pay bills, but have no influence over energy efficiency in building, or owner may pay bills but resident has no incentive to save or conserve.

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Market research on multifamily building owners and managers reveals perceptions of energy efficiencyExpensiveComplex maintenance and upkeepRealized savings are questionableImproved comfort is a big benefitHas to be durableTrustworthy energy efficiency advice is needed

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MN multifamily buildings are relatively fit buildingsSOURCE: Minnesota Multifamily Rental Characterization Study, Energy Center of Wisconsin and Franklin Energy, 2013; sampled 120 bldgs in MN (78 in Twin Cities, 66 Greater MN)

Natural gas = common heating fuel (~66%)Central hydronic = common heat system (83%)4-6 BTU/ft2/HDD

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Natural gas = relatively low cost heating fuel (compared to electric, fuel oil)Hydronic heat = less energy savings potential compared to steam, but easier to work compared to indiv forced airPost war buildings = tighter envelope (masonry buildings), more efficient heat (hydronic)FYI, unit size 1,000ft212

And yet outliers in (almost) every category

SOURCE: Minnesota Multifamily Rental Characterization Study, Energy Center of Wisconsin and Franklin Energy, 2013; sampled 120 bldgs in MN (78 in Twin Cities, 66 Greater MN)

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Water and space heating costs dominateSOURCE: Minnesota Multifamily Rental Characterization Study, Energy Center of Wisconsin and Franklin Energy, 2013; sampled 120 bldgs in MN (78 in Twin Cities, 66 Greater MN)

= 40%= 15%= 10%= 34%Average MultifamilyUtility Costs (per unit / year)

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A study came out last year based on 120 multifamily buildings in MN. Here is the average gas and electric usage for MN multifamily buildings, expressed on a per unit, or per apartment, basis.This is for centrally heated gas buildings, where the owner pays the entire gas bill (most common in MN)And resident pays own electricity, including A/C (window units)MORE DETAILS:Only 13% of units are individually metered for gas (of those with gas heat). Only 4% of units are NOT individually metered for electric. Lighting is 990 kWh of total or about 22% of total. Cooling is 530 kWh of total, or about 11% of total. **Based on 9 cents/kWh for master-metered accounts; 11 cents/kWh for individually metered accounts. **Based on 62 cents/therm for master-meterd accounts; 78 cents/therm for individually metered accounts 14

And yet they are a small piece of the expense pie

Average MN Multifamily operating expenses

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Utility expenses are not 1st 2nd or 3rd priority for spending, but more like the 7th or 9thWhen I get excited that I can save them 15% on their utilitiesmaybe $5,000its important for me to remember that this is within a larger expense pool of 275,000. Your efficiency improvement will save 1.25% of overall expenses. 15

A good investmentHas aggressive energy paybacks Lowers O & M costs Improves building comfort Makes things easier for staff Is tried and true Is easy to implementi.e. Energy efficiency marketability goes well beyond payback

Marketable energy efficiency strategies for MN multifamily

Now Ill talk about some characteristics of MF sector relevant to energy use.17

Good opportunities for energy savings beyond the laundry listOptimizing existing condensing boilersBuilding ventilation modificationsDemand-based hot water recirculation loop controlsAerosol envelope air sealing

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AcknowledgementsProjects discussed are supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through a Conservation Applied Research and Development (CARD) program

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We would like to acknowledge and thank the MN Division of Energy Resources and the Conservation Applied Research & Development (CARD) support that funded this research.19

Optimizing condensing boilers

Conventional boiler

SupplyReturn

Condensing boiler

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Achieving rated efficiency (>90% efficiency)CONDENSING TEMPSReturn water temperature

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Condensing boilers are more efficientbut how much more depends on how often they are able to condense23

Condensing?

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Benefits4-10% of gained efficiencyEliminate short-cyclingGetting what you paid extra for

THE KEY: Driving down return water temperatureMaximize heat transfer at heating elementsSend lower temp water out to the buildingMake sure boiler output matches demandMake sure your piping isnt dumping supply water into returnMake sure domestic hot water is not integrated with space heating boiler

How?Considerations for an existing condensing systemProper excess air levelsAdjusting outdoor reset and sequencing/staging controlsReducing maximum output tempVFD pumping for increased heat transferOR Considerations at time of replacementBoiler room pipingChoosing a boiler with good on board reset and sequencing/staging controls

Excess air can dictate boiler efficiencyImage source: industrialheating.com

ADJUSTMENT RANGE

Measured as % Oxygen in flue gas

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RUSS provided code min o2 levels:CO less than 0.04% air free 400ppmO2 induced draft: 4%-10%, power burner: 3-10%28

Condensing boiler sensitivity to excess airControlling excess air very importantExcess air reduces concentration of water vaporDewpoint decreases Low Excess AirHigh Excess Air

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Oxygen levels in flue gas

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Code allowance of oxygen levelsRuss will check and get back to me (max CO allowed)Tune valve to min oxygen, while keeping below max coEff readout from comb analysis tool will never read above 90does not factor in condensation30

Heating elements: Youre stuck with themIt isnt cost effective to add moreDirty or blocked radiation affects heat transfer

Control boilers for lowest possible outputOptimized outdoor resetFinding the lowest max output temp for the buildingSequencing and staging for optimal efficiency

Sequencing and staging: running boilers at low outputshow manufacturers curves for eff at lower input rate. Watch out for: short-cycling. Levels of control and control interaction.

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Control the boiler so it doesnt exceed demand

20F in March

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Outdoor reset lowers boiler water temperatureAs outdoor temps get warmer, the building heating load gets smaller and the boiler water temperature can be lowered.

Boiler water temperature with outdoor resetSpace 75F

Boiler water temperature, no control

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Great for any boilercan go further with condensing boilers34

Optimizing outdoor resetMin OAT for condensing moved from 34F to 22 FCan you go lower?Boiler water tempOutdoor tempAdjusted supply curveAdjusted return curve

Outdoor reset adjustment

14 unit building:9.5% space heating savings (no cost)Reduced building over-heating

At replacement: Identify boiler control limitationsThis boiler controls non-adjustable minimum outside temp of 0F is not ideal for MN

Boiler sequence and firing stage controls: matching output to load for best efficiencyLower output firing stages have increased thermal efficiency

Image source: Lochinvar.com

Lochinvar Knight boiler cascade strategies:

Image source: lochinvar.com

Sequencing boilers: mixed efficiency

41 unit building:11% space heating savings3 year paybackReduced short-cycling

Single stage combined with 2 stage controller2 boilers fired (condensing and non condensing). = shorter firing intervals, more efficientSolution: 3 stage control, no rotating lead40

Sequencing/staging: All firing on at once because they cant talk to each other

32 unit building:6% space heating savings5 year paybackReduced short-cycling

Excessive BTU output-may exceed building demandreturn water will come in hotter-shorter firing intervals (short-cycling)41

Variable speed pumps (VFDs, VSDs)Reduce the pump flow during part-load (when zones close) Allows for lowered return water temperaturemore potential boiler condensing conditionsElectricity savings

Little difference between boiler supply and return temperatures indicates potential for improvement

1- Adjust reset temps as low as possible2- VFD pump control optimizes heat transfer as zones open and close

Boiler room piping: address at replacement

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2

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RETURN

Building loop

Not ideal: Adjacent boilers warm return water

Better piping

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RETURN

Building loop

Domestic hot water can dictate return water tempsTraditional coil-in tank requires high boiler temperatures, limiting boiler efficiency during DHW callDirect-fired condensing water heaters will be more efficient

130F

Boiler180F

Water heater

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Better efficiency from sep direct fired condensing system. Sidearms require 180F boiler temps for hx46

Summary: getting condensing boilers to condense!Proper oxygen levels in flue gas contribute to optimal condensing conditionsMaintaining aggressive control settings prolongs condensing capabilities VFD pump controls reduce pump speeds at part loads to optimize heat transferBoiler room piping can dictate return water tempsChoosing direct-fired condensing water heaters over indirect (sidearm) water heaters will maximize efficiency

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Piping in seriesinclude diagramStraining cleaning before install??

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More info on condensing boiler researchFinal report will be published this summer12 sites (Education, Office, Multifamily facilities)Optimization improvements and energy savings analysis

Webinar on April 3rdMncee.org/innovation- exchange

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Optimizing ventilation systems

Optimizing ventilation systemsISSUESHigh fan electricity useExcessive ventilation airflowOccupant complaints of drafts, odorsDuct leakageClogging and other flow balancing problemsDifficult/costly to measure and quantify energy savings associated with retrofitting

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Central ventilation systems

Central apartment exhaustCentral corridor/make up air systems

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Out of whack buildings. Higher flows up top. Near zero flows near bottom. Balancing flows and reducing overall flows balances and delivers the appropriate amount of ventilation without over-ventilating.51

Ventilation Improvements corridor systemsReduce fan speed to provide code required ventilation flow

ISSUESDesign flow rates were much higher than current required flowFaulty controls/sensorsFlow rates not verified

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Corridor ventilation retrofit in MinneapolisProject: Re-sheave fan for lower flow4,700 cfm reduced9,611 therms saved7,244 kWh saved$6,899 annual savings Uncertain resultsVs.

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Eliminate need for fire caulking penetrations at wall cavities ?Would not eliminate leakage that happens after the sealing (cabinets install, tstat/lighting installs, etc.)2 parts to the prep: day ofsealing and covering. And days beforework coordination and inspect for readiness. Did 2/day on the first 4-5 hours eachNEED FOR BALANCED MECHANICAL VENTILATION! If design previously included bringing in air from outside, than that will need changing: trickle ventilation or balanced ventilation. Not supply only or exhaust only. 80

Marketable? BENEFITSReduced mid and high range noise transferReduced odor transferImproved comfortSimultaneous air leakage testing ensures resultsExpedited process, labor savings potential

CONSIDERATONSCostNot a solution for large air leak gapsRehab or new construction onlyBalanced ventilation is crucial

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How does material age?Toxicity? low ingestion hazard Main issue: person who works with it day-to-day. Rubber gloves and respirator when airing out unit.

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Stay tuned for more info (Fall 2016)Study will look at :6 test sites; Rehabs and new construction in MNEnabling commercialization of processAir leakage reductionsSound attenuationID leak site locations with fluorescent dye/black light photographyEvaluation of time and materials required

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When will study wrap up? Testing 3 new construction buildings, and 3 rehab sites. End of year final report (end of 2016).

How many total sites? 6ish

UC Davis and contractor on east coast awarded contract for moderately sized military buildings

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More info CEE programs and research: mncee.org

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Corrie Bastiancbastian@mncee.org612.244.2425

Questions?

Applications for the program up front

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