Energy Audit improvements in small office buildings

7/27/2019 Energy Audit improvements in small office buildings

http://slidepdf.com/reader/full/energy-audit-improvements-in-small-office-buildings 1/7

1 4 A S H R A E J o u r n a l a s h r a e . o r g O c t o b e r 2 0 1 2

Large commercial ofce buildings1 tend to be homogeneous in size

and shape, but small ofces come in a variety: old walkups, converted

strip malls, newer single-story buildings, old schools, houses, and more.

My hometown even has an old jail that was converted into a small ofce

building, appropriately and fondly still called, “The Old Jail.”

space, so envelope deciencies and as-sociated energy opportunities shouldnot be overlooked.

Small oce buildings typically do nothave energy management systems, socontrol improvements need to be exam-ined in a dierent way than or big build-ings. Small oce buildings also oten useresidential HVAC equipment, or smallcommercial equipment such as packaged

rootop units, almost all o which are di-rect-expansion cooling systems.

Chillers are virtually non-existent,and boilers are rare. This is the almostexclusive domain o small orced-airsystems. Ventilation and economizermode ree-cooling tend to be a chal-lenge or the very smallest equipment,as smaller unitary equipment (such as

About the Author

Ian M. Shapiro, P.E., is president of Taitem Engi-

neering in Ithaca, N.Y.

By Ian M. Shapiro, P.E., Member ASHRAE

Energy Audits, Improvements

In Small Ofce Buildings

Small ofce buildings are often old houses, such as this one in Ithaca, N.Y. (circa 1954 at right, present day at left).

And while large commercial ocebuildings get a good bit o attention,small oce buildings run the risk o being overlooked and underserved orenergy improvements because o theirsize. But taken as a group, small ocebuildings are signicant. I we looselytreat 25,000 t2 (2323 m2) as the up-per limit o “small,” more than 90% o oce buildings (by count) are small,representing 34% o all oce foor

space.

2

Common traits between small andlarge oces include their main spacetypes: primarily desk/oce space, butalso conerence rooms, storage/ling,kitchenettes and break rooms, bath-rooms, corridors, stairwells, copy/printareas, and computer rooms.

But with all the common traits, smalloces are very dierent rom largeoces in their energy characteristics.Small oce buildings tend to be enve-

lope-dominated, with little interior core

This article was published in ASHRAE Journal, October 2012. Copyright 2012 ASHRAE. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE. For more information about ASHRAE Journal, visit www.ashrae.org.



O c t o b e r 2 0 1 2 A S H R A E J o u r n a l 1 5

For small orced air urnaces, replacement with condensingurnaces is usually straightorward, and oers added benetssuch as integrated variable-speed blower motors, typically re-erred to as electronically commutated motors (ECMs). Pack-aged rootop systems still do not have integrated condensing

urnaces, although we are seeing some development activityin that direction. Variable speed motors are now common ineven small rootop units. High-eciency cooling also is anoption, although less cost eective in the heating-dominatedclimates o the North, just as heating replacement is less costeective in the cooling-dominated South.

For controls, the opportunities are also similar to those orlarge oce buildings. As a building class, oces have ex-tremely low hours o operation, averaging only 55 hours perweek. So setback o temperatures during heating and cool-ing are critical. Without an energy management system, thisis typically evaluated on the basis o savings with a program-mable thermostat.

When we combine the low operating hours with the act thatoces have the highest occupant density o the any o 13 CBECScommercial building classications (at 434 t2/person (40 m2 per person), compared to 501 to 2,306 t2/person or the other12 classications [health care, ood service, etc.]), we absolutelyneed to evaluate demand-controlled ventilation (DCV). For ex-ample, a small 3,600 t2 (330 m2) oce building with our oc-cupants might need only 260 cm (123 L/s) ventilation, accordingto ASHRAE Standard 62.1, but annual energy cost savings morethan $400/year still accrue i DCV is used. Thereore, the cost o DCV controls may be merited despite the building’s small size.

For those small oce buildings which rely on windows or

ventilation, we’re out o luck, but this will lead to a discussiono tightening the envelope, adding ventilation, and then apply-ing DCV to the ventilation (increasingly called “build tight,ventilate right”). For rootop units, DCV is oten an o-the-shel or retrot option.

High-eciency lighting is a solid improvement to evaluate,and generally ollows the same methods as or large buildings.Start with 24/7 corridor and stairwell lighting, and move righton to the oce lighting. But do not assume lighting that uses

T8 with electronic ballasts means there are no opportunitiesor lighting improvement. Check lighting power densities on aroom-by-room basis.

Take advantage o the ull range o IES lighting recommen-dations o 30 to 70 ootcandles (320 to 750 lux) or oces,3 and see what lighting power density is possible down at thatlower 30 ootcandle (320 lux) level (which is more than ad-equate or oces where people are sitting at computers). (Wereally need a better term or reduced lighting power density.“Reduced lighting power density” just does not roll o thetongue, or speak to building owners. “De-lamping” is not bad,but still sounds like we are taking something away rom thebuilding, as does “Reduced overlighting.” How about “right-lighting?”)

Consider evaluating task lighting at one lamp per desk. A

lighting evaluation is not done without ull evaluation o light-

residential split systems that are so common in small oces)oten do not integrate these unctions.

Small buildings typically do not have specialty loads suchas elevators or on-site transormers, and they have very ewlarge motors.

There are operational and structural dierences as well.Small buildings usually do not have on-site maintenance per-sonnel who might be tending to energy systems. Buildings be-low 5,000 t2 (465 m2) cannot be benchmarked in EPA Porto-lio Manager, so tracking o energy costs may be less common.Almost all (more than 90%) small oce buildings are one ortwo stories in height, whereas more than 50% o large com-mercial oces buildings are three stories or higher.

Small oces also oten tend to be integrated as part o amixed-use building, or example, as one foor o an apartmentbuilding, or as one section o a strip mall. Small oces are alsooten just old houses, with eatures such as pitched roos andbasements. This brings us back to the importance o envelopeenergy losses and improvement opportunities, as well as to theimportant emerging improvements relating to reducing distri-bution losses. The energy audit challenge or small oce buildings is sim-

ply that the small size makes or poor economy o scale. It isdicult to get in and out o a small building, and do a good

job in the time needed to keep the energy audit cost down toa reasonable ratio o the annual energy costs o the building.We need to nd cost-eective ways to serve these buildings.At least this is the perception.

In reality, a 5,000 t2 (465 m2) building with $15,000/yearin energy costs probably warrants something better than a

quick walk-through audit. But a small 1,500 t2 (139 m2)building certainly is a challenge to serve cost eectively.

This needs to be kept in mind as we develop energy auditapproaches. And, just because small oces are small, doesnot mean that engineers are not involved in energy audits. InNew York, audits or the state’s program or small commer-cial buildings are done by a group o engineering rms, withthe same rms also doing large commercial and industrialenergy audits.

Let us look at available energy improvements in small ocebuilding energy audits, and then look at a case study where en-ergy use was reduced by 60% in a small oce building. What

is possible? What is cost-eective?

Improvement Mix

A rst group o improvements sounds similar to those orlarge oce buildings: High-eciency HVAC, controls, andhigh-eciency lighting. Nothing new, right? Well, no, but itturns out we need to make a ew adjustments or small oces. To evaluate HVAC improvements in small oces, it is help-

ul to amiliarize onesel with the classes and energy eciencyterminology o residential and small unitary HVAC equipment,such as seasonal energy eciency ratio (SEER) and annual uelutilization eciency (AFUE). High-eciency HVAC replace-

ments can be an excellent and oten simple improvement.



1 6 A S H R A E J o u r n a l O c t o b e r 2 0 1 2

ing controls. A typical two-desk ocewith two or more light xtures shouldhave at least two light switches. There isno need or all the lights to be on in apartially occupied oce.

Occupancy sensors (or example, inte-grated with bilevel xtures) make senseor stairwells and corridors. Vacancy sen-sors (occupancy sensors that only turn alight o, but require a person to turn themon) are appropriate or print/copy areas,kitchenettes, conerence rooms, and otherareas where the lights do not need to turnon with every occupancy or where we donot want the lights to come on when peo-ple are just walking by the space.

Occupancy sensors also make sense inbathrooms and utility rooms such as lingand mechanical rooms. Occupancy sen-sors oten work or outdoor lighting whenused in combination with photo-sensors,so lights are kept o during the day.

Dierences between large and smalloce buildings really get ampliedwhen it comes to the building envelope.In small buildings, wood-rame oper-able windows dominate, compared to thetypical metal-rame xed windows inlarge oces. In small buildings, wood-rame walls dominate, compared to con-

crete and metal in large oces. And insmall buildings, pitched roos are re-quent, and with pitched roos come allthe complexities o attics, and a set o energy losses which simply do not existin fat-roo buildings. Finally, small o-ce buildings oten have basements, alsowith their own signicant set o energylosses and improvement opportunities. The good news is that small o-

ce buildings are small enough to useblower door tests to examine inltration.

Already common in residential energyaudits, we need to take advantage o thisgreat tool in small oce buildings.

Blower door tests are good not onlyor measuring inltration, but also ornding out where the inltration is, andor guiding air-sealing, and or qualitycontrol on the nished project. A typi-cal blower door test only takes an hour.Count two hours i more advanced di-agnostics are done or harder to nd airleaks. I predict that government and util-

ity programs will start requiring blower

door tests or all projects under 10,000t2 (929 m2), as has become standard orresidential energy audits, because the in-ormation gained is so valuable.

Likewise, inrared scans, widely used

in residential energy auditing, have agreat place in energy audits or smalloce buildings. Inrared scans are use-ul not only or identiying conductionlosses, but can also contribute to ndingair leakage as well. Insulation is a majorimprovement or small oce buildings,where it can be installed in uninsulatedwalls, attics, and basements.

Almost all oces have kitchenettes,and almost all kitchenettes have rerig-erators, most o which are residentialrerigerators. Evaluating replacementrerigerators is readily done with onlinedatabases o consumer rerigerators (e.g.,www.kouba-cavallo.com/remods.htm).For example, a typical old 1,200 kWh/year rerigerator can be replaced with anENERGY STAR rerigerator rated be-low 400 kWh/year or under $500, witha simple payback o under ve years.When evaluating rerigerators, it is im-portant to pay attention to the size andnumber o rerigerators. Are all rerigera-tors needed? Can smaller rerigerators be

used in the place o large rerigerators?Vending machines are another com-

mon plug load in oce buildings.Replacement ENERGY STAR vend-ing machines are available, along withcontrols which can be retrot to allowoccupancy sensors to turn vending ma-chine lights and compressors o. TheEPA reports that high-eciency vend-ing machines are 50% more ecientthan standard machines, and can savemore than 1,700 kWh/year. Again, like

rerigerators, go one step urther and askthe owner i all vending machines areneeded. Many small oce buildings cansimply use the existing rerigerator tocool drinks, and dispense with the vend-ing machine, pun ully intended.

An interesting load in small ocebuildings is the domestic hot water. I the building only has bathroom andkitchen sinks, this load can be very low,in act hot water is rarely used. So, in-stantaneous (and even point-o-use) wa-

ter heaters can make a lot o sense.

Adverti sement formerly in this space.




environmental not-or-prots, an acupuncturist, a solar energycompany, and a vet who does house calls. The oundation is a ull basement with poured concrete walls.

The building has its original wood-rame windows, althoughmost have aluminum storm windows. Interestingly, the houseoriginally had gas lighting, as evidenced by abandoned gaslighting pipes. The building is heated with a orced-air gas ur-nace, and cooled with a residential split system air conditioner.

Energy renovations were made to the building over 10 years,rom 2002 to 2012. What is interesting is that many o these

energy renovations were made separately, and so we can exam-ine the energy savings impact o these improvements separately.

Through the energy renovations, the building’s character andhistoric eatures were maintained, and this resulted in the build-ing receiving an award or historic preservation in 2011. The energy improvements began in October 2002, when

our engineering rm moved into the building, replacing about10 incandescent lamps in the lobby and two oces, changinglighting in one small oce rom eight to our T8 lamps, andinstalling an ENERGY STAR rerigerator.

Electric

Savings

(kWh/yr)

Gas

Savings

(therms/yr)

Installed

Cost

Annual

Cost

Savings

Insulate Walls, Air-Sealing,Storm Windows

163 326 $9,440 $514

Duct Sealing 134 267 $2,110 $421

Furnace Replacement 363 124 $4,980 $240

Duct Insulation 57 113 $980 $178

Attic Insulation and Air Sealing 41 82 $6,250 $129

Ductless Air Conditioning 510 0 $12,500 $77

Instantaneous Water Heater 0 49 $3,040 $74

V-Strip Window Weatherstripping 21 43 $550 $67

Lighting Improvements 715 –29 $950 $64

Table 1: Energy improvements at 109 South Albany Street.

Case Study

A case study gives us some insightinto what does and doesn’t work withenergy audits and actual improvementsin a small oce building. 109 South

Albany Street, Ithaca, N.Y., was builtaround 1910 as a 1,625 t2 (151 m2) sin-gle-amily house. It was converted to anoce building around 1980, serving asa doctor’s oce, as oces or a generalcontractor, as oces or a credit union,as the oces or our rm rom 2002 to2009, and currently as a multi-tenantproessional oce building, with o-ces or a diverse set o tenants: several

Advertisement formerly in this space. Advertisement formerly in this space.



2 0 A S H R AE J o ur na l Oc t o b e r 2 0 1 2

In August 2003, a multisplit ductless air-condi-

tioning system was installed, to replace the central

ducted split system. Indoor units are typically wall-

mounted, just below ceiling level. There are two

separate systems—one or each o the two oors.

In February 2004, an old standing-pilot residen-tial gas storage water heater was replaced with an

electronic-ignition instantaneous gas water heater.

In the all o 2004, we were visited by a local gas

utility representative. He had come to investigate

why our gas meter had ailed. But the gas meter had

not ailed! Our summertime gas usage had simply

dropped to nearly zero because hot water is rarely

used in the two bathroom sinks or kitchen sink, and

so the instantaneous water heater rarely fres.

In January 2009, dense-pack cellulose insulation was blown

into the walls, some air-sealing was done including weather-

stripping three doors, approximately fve storm windows were

installed over single-pane windows, and the old urnace was

replaced with a high-efciency condensing urnace with a

variable speed motor and downsized rom 120,000 Btu/h to

60,000 Btu/h (35,200 W to 17,600 W).

In March 2009, the ducts were sealed manually using mastic.

In July 2009, lighting improvements were made: our T8 lamps

were removed (two each in two ofces), one old T12 fxture was

From 2005, we adopted a policy to purchase ENERGY

STAR computers. As a trend toward using notebook comput-

ers increased, it was oset a bit by a trend or some people to

use two monitors. One person even started using three moni-

tors. With our growth came an increase in server power use.

Ater some o these early energy improvements were made,

we decided to do an energy audit in 2008 to see what good

improvements still remained. We proceeded to implement the

audit recommendations and continued examining actual en-

ergy savings.

Figure 1: Total energy use at a small ofce building at 109 S. Albany St.

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

200

180

160

140

120

100

80

60

40

20

0

M M B t u / y r

Advertisement formerly in this space.




replaced with a T8 xture, several vacancy sensors were installedin spaces such as the kitchen, and a photo sensor was installed ona small ront porch light. In December 2009, the basement ductswere insulated with 2 in. thick berglass insulation.

In January 2011, the attic foor was air-sealed (ater remov-

ing the existing insulation), the attic insulation was increasedrom approximately R19 to R50, and an unused replace onthe rst foor was sealed.

In September 2011, the ducts were sealed using an aerosol

sealing technology. Interestingly, more than 350 cm (165 L/s)in duct leakage was measured beore the aerosol duct sealing,even though the ducts had been sealed with mastic two yearsearlier. The mastic clearly had not eectively sealed the ducts.

The aerosol duct sealing reduced leakage to below 30 cm (14

L/s). In February 2012, the windows were weather-stripped us-ing vinyl V-strip weather-stripping. The number o occupants changed over time. In 2002, when

we moved in, there were about six people in the building. Whenwe moved out, in 2009, there were about13 people in the building. We were re-placed in 2009 by several tenants whowork part-time, reducing the occupancy toabout three ull-time equivalents.

Results o this work are shown inTable 1, Page 18. Installed costs and an-nual cost savings have been adjusted to2012 dollars. Almost all savings are ac-tual measured savings that are adjustedwith weather corrections. For some o the smaller improvements, or whichsavings could not be seen in the noise o the utility bills, the audit-predicted sav-ings are shown. In one case where twoimprovements were made simultaneous-ly, urnace replacement and wall insula-tion, the actual savings were proratedby the estimated savings rom the en-ergy audit. Likewise, almost all installedcosts were actual contractor costs, with

a ew exceptions where costs were nottracked, in which case energy audit es-timates were used. Table 1 combinesresults or the two duct sealing improve-ments into one improvement. The energy audit was accurate with

some predictions, and inaccurate withothers. For example, the energy audit pre-dicted 216 therms/year (6,330 kWh/year)savings or duct insulation, and measuredsavings were 113 therms/year (3,310kWh/year). The energy audit calcula-

tion relies heavily on an assumption o urnace run-time, and so we presume theaudit overestimated the runtime. The en-ergy audit predicted 58 therms/year (1,700kWh/year) savings or duct sealing, andmeasured savings were 267 therms/year(7,820 kWh/year). This dierence canlikely be explained by high duct leakageound in testing. A “panned return” (returnduct ormed by adding one side o sheetmetal to the space between foor joists)had heavy air leakage in a large space be-

tween a joist and the foorboards above.





The energy audit predicted 353 therms/year (10,350 kWh/year) savings or wall and foor insulation, matching reasonablywell against actual savings or a slightly dierent improvement(wall insulation, air sealing, and a ew storm windows), whichwere measured at 326 therms/year (9,550 kWh/year).

Note the signicant envelope savings (insulation and air-seal-ing), comprising 40% o the overall annual cost savings. The air-sealing improvements involved in-depth work, not just windowand door weather-stripping, by contractors certied in building

energy improvements, and guided by blower door diagnostics.Distribution improvements (duct sealing and duct insulation) arealso large, equal to 34% o the overall annual cost savings. Notealso the impact o lighting improvements (controls and “right-lighting”) even though the building primarily already had T8 fu-

orescent xtures with electronic ballasts beore the project began. The total reduction in energy use is signicant: a 60% re-duction over the 10 years, on a basis o total energy usage(Figure 1, Page 20).

Conclusion

Along with the dramatic reduction inenergy use, tenants repeatedly report thebuilding is much quieter ater the energyimprovements, despite a new busy citybus route on the street outside. Comortis also improved, primarily due to themulti-split air conditioners with thermo-stats in each oce.

With the 60% reduction in energy use,our plan now is to shoot or net zero. A6.7 kW solar photovoltaic system is beinginstalled this summer, and we are mullingconverting to an air-source or geothermalheat pump. With a little luck, we will havemade “100% to net zero in 10 years.”

Small oce buildings are a wonder-ul mix o sizes, shapes, and diverse oc-cupants. Substantial energy savings arepossible i attention is paid to detail.

Energy audit prioritization o cost-eec-tive measures should include evaluationo envelope improvements and HVACdistribution improvements, in additionto the more standard lighting and high-eciency HVAC plant improvements.

Acknowledgments

This research was supported by the Taitem Engineering C-NEW AppliedEnergy Research Initiative. The auditwas perormed through NYSERDA’s

Energy Audit program or small busi-nesses. Rob Rosen, Yossi Bronsnick,and Jim Holahan managed the energyrenovations described in the case study.

References1. Shapiro, I . 2009. “Energy audits in large

commercial oce buildings.”ASHRAE Jour- nal 51(1):18 – 27.

2. EIA. 2006. “Commercial BuildingsEnergy Consumption Survey (CBECS).” U.S.Energy Inormation Administration.

3. IES. 2011.The Lighting Handbook , 10th Edition. I lluminating Engineering Society.


Documents

Energy Audit improvements in small office buildings