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Energy and Buildings 75 (2014) 430–438

Contents lists available at ScienceDirect

Energy and Buildings

j ourna l ho me pa g e: www.elsev ier .com/ locate /enbui ld

nalysis and feasibility study of residential integrated heat andnergy recovery ventilator with built-in economizer usingn excel spreadsheet program

unlong Zhang ∗, Alan S. Fung, Sumeet Jhinganepartment of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, Canada M5B2K3

r t i c l e i n f o

rticle history:eceived 30 August 2013eceived in revised form 10 February 2014ccepted 13 February 2014

eywords:eat and energy recovery ventilationconomizerxcel spreadsheet

a b s t r a c t

Currently, heat recovery ventilator (HRV) and energy recovery ventilator (ERV) are commonly studied.Nevertheless, there is limited information regarding the dual-core approach energy recovery. This paperinvestigates the feasibility of an integrated HRV and ERV system, namely HERV, with a built-in econo-mizer used in the residential sector to reduce dependency on furnace and air conditioning systems. Inorder to achieve this goal, an excel-based analysis tool was developed, providing a quick estimate ofsystem performance and comparison with the HRV and ERV that are currently being used in researchhouses. The potential of integrated heat and energy recovery ventilator was evaluated based on its cal-culated operating cost ratio (OCR) and its payback period. Results collected for Vancouver and Toronto,

corresponding to temperate and continental climate, indicated that the OCRs of the HERV were four timessmaller than the ERV’s, meaning that the proposed system was cost-efficient. It was also evidenced thatthe high demand on the economizer resulted in higher energy saving and shorter payback period of thesystem. In conclusion, the integrated HERV system with a built-in economizer could be a feasible optionfor both temperate and continental climates.

© 2014 Elsevier B.V. All rights reserved.

. Introduction

The growing energy crisis has resulted in an increased emphasisn energy conservation. In Canada, due to its cold climate, many ofur homes require year-round indoor climate control to maintainr provide a comfortable living environment. As a result, energyonsumption for space heating and cooling contributes to approxi-ately 65% of the total required energy in the residential sector [1].

oday, residential houses are increasingly being built as airtightouses (e.g., R-2000 house) to improve the efficiency on energyse [2]. The well-insulated envelope, however, leads to a dilemmaor indoor air quality, which has caused a rise in demand for thencreasingly popular residential heat recovery and energy recoveryentilator. These systems provide a mean for utilizing the wasteeat within the exhaust air instead of releasing it directly to theurroundings.

Heat recovery ventilator (HRV) is a sensible heat exchanger thatakes advantage of the temperature difference between two air-ows. In contrast, energy recovery ventilator (ERV) allows both

∗ Corresponding author. Tel.: +1 647 721 2737.E-mail address: jun.zhang@ryerson.ca (J. Zhang).

ttp://dx.doi.org/10.1016/j.enbuild.2014.02.036378-7788/© 2014 Elsevier B.V. All rights reserved.

sensible and latent heat to be transferred from one airstream toanother. It was confirmed that the ERV provided a better overallthermal performance in hot and humid regions (e.g., south China)[3–5]. These different designs all try to serve the same purpose, butone may be more efficient than the others depending on the core.As a result, core design is usually pursued in the current design onthe market. In the recent decades, there has been a distinct focuson investigating the potential of ventilation heat recovery and fac-tors that affect its thermal performance. In the study conducted byGieseler et al. [6], air-to-air heat recovery system was found to bemore cost-efficient than an earth-to-air heat exchanger. Marsik andJohnson [7] simulated the energy performance of a HRV-equippedhome in Fairbanks. Dodoo et al. [8] conducted a study to investi-gate the primary energy savings from the ventilation heat recoverytechnique in conjunction with different types of end-use heatingsystems. The potential of free-cooling was studied by Hüsamettin[9]. This study showed that, for a conditioned space with supply airtemperature of 24 ◦C, a dry-bulb temperature economizer resultedin a cost saving of $342/year for a chiller system.

Currently, single core heat/energy ventilation systems dominatethe market, which leaves room for a dual-core system that couldpossibly outperform them. Nevertheless, there is limited informa-tion regarding the dual-core approach energy recovery. Therefore,

J. Zhang et al. / Energy and Buildings 75 (2014) 430–438 431

Nomenclature

ERV energy recovery ventilatorHERV heat and energy recovery ventilatorHRV heat recovery ventilatorNbin frequency for a particular binq actual heat transfer (kJ/h)q′ total heat transfer for a particular bin (kJ)qmax maximum available heat for recovery (kJ/h)qfen heat gain/loss through transparent fenestration sur-

faceqint internal heat gain/lossqopa heat gain/loss through opaque surfaceqven ventilation heat gain/lossRH relative humidityT air temperature (◦C)SEER seasonal energy efficiency ratioVHR ventilation heat recoveryw humidity ratio (kg/kg)

Greek symbolsε efficiencyε′ weighted annual efficiency

Subscriptsavg averageL latentout outdoors sensibletot total

tiaEth

2

2

adsdcflhUetaivuosipd

Table 1Leakage-infiltration ratio (No).

U.S. Canada

Phoenix 22 Edmonton 19Los Angeles 25 Vancouver 22San Francisco 22 Winnipeg 16Colorado Springs 19 Fredericton 19Miami 22 St Johns 16Atlanta 22 Halifax 19Chicago 19 Toronto 19Indianapolis 19 Montreal 19Boston 19 Saskatoon 19Minneapolis 16 Inuvik 19St Louis 19 Churchill 19Las Vegas 22 Eureka 19New York City 19 Mould Bay 19Oklahoma City 19 Whitehorse 19Salt Lake City 19 Summerland 19West Palm Beach 22 Iqaluit 16

presented in Table 2.

Table 2Airtightness at 50 Pa for different types of house [12].

his study aimed to provide a preliminary system analysis for anntegrated heat and energy recovery ventilator (namely HERV) with

built-in economizer using a simple Excel spreadsheet tool. Thexcel tool was developed with the intention for non-technical userso evaluate the potential benefits of the combined HERV for a givenouse envelope and climate condition.

. Methodology

.1. Earlier and present works

In 2012, Chen et al. proposed a conceptual design for HERV in parallel flow arrangement [10]. The paper concluded that such aesign is a feasible option for dry and continental climates. In thistudy, an excel-based analysis tool (Ebat) was described, which waseveloped to measure quantitatively the feasibility of the HERV in aounter-flow arrangement. The design schematics for the counter-ow HERV are shown in Fig. 1. Basically, the developed analysis toolas four divisions: Inputs, Database, Computations, and Outputs.sers only need to fill in the required inputs (e.g., house envelope,tc.) for building load calculations, and the program automaticallyransforms these inputs into outputs by deploying the databasesnd the computational functions programmed in it. The lists ofnputs and outputs are shown in Fig. 2. In addition, the tool pro-ides a comparison between a conventional HRV/ERV defined bysers and the combined HERV in order to clarify the pros and cons

f these systems for different climate conditions. This paper con-ists of a short exposition for the methodology and formulas usedn Ebat, followed by a case study that intended to study the pro-osed HERV using the accessible HRV and ERV performances as theefault performance data.

Albuquerque 22

2.2. Natural infiltration

Air infiltration is often measured in terms of air change per hour(ACH), which describes the rate the air in a space is replaced by out-side air. This measurement is needed to calculate the sensible andlatent heat gains of a house, as well as the net mechanical ventila-tion rate. An exact calculation of annual ACH is impractical becausethe instantaneous ACH varies continuously over time. To simplifythe process of analysis, an average ACH was used. In 1987, basedon the Kronvall–Persily estimation model and the LBL infiltrationmodel, Sherman [11] derived an equation for the estimation ofannual average air change rate (ACHavg) in dwellings using hourlyair change rate at 50 Pa (ACH50) and leakage-infiltration ratio (No).

ACHavg = ACH50

No × H1 × S2 × L3(1)

The leakage-infiltration ratio (No) is a site climate indicator thataccounts for the physical and environmental properties of singlefamily houses. The typical leakage-infiltration ratio can be obtainedfrom the plot of leakage-infiltration indicator, which was developedby Sherman for typical houses. Table 1 lists some of the No factorsthat were used in Ebat. For a particular house, correction factors forbuilding height (H1), site shielding (S2), and leak type (L3) can beused to correct the indicator No. Furthermore, the above expressionrequires house air change rate at 50 Pa (ACH50), which in generalcan be obtained from blower door test. However, this test is uncom-mon to many households because it is usually unnecessary and/orcostly. As a result, an alternative approach was proposed by provid-ing a customized option that allows the program to determine theassociated ACH50 of a house based on its air tightness type. Accord-ing to Fung et al. [12], the air tightness of residential houses can begrouped into four main types—loose, average, present and energyefficient house. The associated ACH50 for each air tightness type are

House Type ACH50

Loose 10.35Average 4.55Present 3.57Energy-Efficient 1.5

432 J. Zhang et al. / Energy and Buildings 75 (2014) 430–438

to col

2

eghvasElctatettdir

ε

o

ε

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q

temperature (row) and relative humidity (column) bins of 2 C and5% increments, respectively. A sample bin table is given in Table 3.For each bin, the total bin hour (Nbin) of each particular outdoorcondition was counted. Therefore, the annual total exchanged

Table 3Sample bin table.

To Range (◦C) �o Range (%)

45 50 55 60

Fig. 1. Basic design architecture schematic. (For interpretation of the references

.3. Efficiency and space loads

The efficiency of heat/energy recovery is an important param-ter for the estimate of system performance. This parameterenerally varies depending on the outdoor weather conditions, andence, correlations are needed. Two projects led by Ryerson Uni-ersity already tested the potential of HRV in Mattamy house [13]nd ERV in TRCA Archetype Sustainable House-B [14]. For the casetudy presented in this study, the performance data of the HRV andRV were applied into the tool as the default performance data. Ainear equation was developed from the monitored sensible effi-iencies of the HRV in Mattamy house. Fig. 3 and (2) demonstratehe linear relationship between sensible recovery efficiency (εS)nd outdoor air temperature (Tout). For outdoor air temperaturehat drops below 0 ◦C, this equation predicts that there is a sensiblefficiency lower than 65%, and vice versa. In order to clearly identifyhe potential of the HRV and ERV in different climatic conditions,he equation of sensible recovery efficiency was also used to pre-ict the sensible efficiency of the ERV, and hence, both systems used

n the case study would have the same potential of sensible heatecovery.

S = 0.6561 + (0.0058 × Tout) (2)

The linear equation for latent recovery efficiency (εL) was devel-ped based on the ERV monitored data.

L = 0.4542 + (0.005417 × Tout) (3)

The HERV used for the case study was assumed to be consistingf a similar sensible and enthalpy core, so both (2) and (3) weredopted to predict the efficiency of each core. It is worth notic-ng that the efficiency equations of HRV, ERV and HERV could beeplaced by the users accordingly in the future. Besides, accordingo ASHRAE Handbook [15], a multiple-pass heat exchanger is about.2 times more efficient than a single core heat exchanger. Thispproximation was adopted, meaning that the sensible efficiencyf the HERV was 1.2 times higher than the HRV and ERV. Basedn the efficiencies for all possible outdoor weather conditions, theensible and latent heat being exchanged across the process (q) can

e determined by multiplying the efficiency (ε) to the maximumvailable heat for recovery (qmax).

= qmax × ε (4)

or in this figure legend, the reader is referred to the web version of this article.)

In order to study the impact of heat/energy recovery on spaceloads, it is necessary to calculate the rate at which energy mustbe added to/removed from a space, or in other word, heating andcooling loads are needed. According to ASHRAE Standard, both sen-sible heating and cooling loads (qs) of a house are the sum of heatgains/losses from occupants, appliances and ventilation, as well asthe heat gains through opaque and transparent fenestration sur-faces. In contrast, the latent load (qL) of a house is the sum of internaland ventilation heat gains/losses [16].

qS = qopq + qfen + qven + qint (5)

qL = qven + qint (6)

2.4. Bin method

Energy calculations sometimes are computed using the averageoutdoor conditions to provide a quick prediction on the heatingand cooling loads for a structure. However, for HVAC equipmentwhose performance depends on outdoor weather conditions, thisenergy-estimating method becomes insufficient as the thermalefficiency of the system may not be constant. Therefore, bin methodwas applied to evaluate separately the recovered heat at differentoutdoor conditions. Historically, bin method has been adoptedby Kavanaugh and Lambert [17] into their heat pump energyevaluation program to calculate the annual energy use for ground-coupled heat pumps. In this study, Ebat was designed to be ableto import hourly weather data. These data were then sorted in air

◦

20 Frequency of each bin222426

J. Zhang et al. / Energy and Buildings 75 (2014) 430–438 433

Fig. 2. Process flow chart for Ebat. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Effici ency (%) = 0.0058 (Tout) + 0.6561

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

-30 -20 -10 0 10 20 30 40

Effici

ency

(%)

Outdoo r Tempe rture (oC)

Ma�amy HRV Effici ency vs. Outdoo r Te mperat ure

Fig. 3. Correlation for sensible efficiency [18]. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

4 d Buildings 75 (2014) 430–438

ed

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Table 4Specifications of the Archetype Sustainable House-B [20,22].

Features House-B

Story 3Floor area 325 m2

Internal volume 931 m3

Window area 46.36 m2

Windows insulation Triple glazed (1.59 m2 K/W)Roof insulation Structurally insulated panel

RSI 7 (R40)Wall (above grade) Heat-lock soya polyurethane foam

Icynene spray foam7.62 cm Styrofoam

3.2. Annual mode demands

The noteworthy advantage of the spreadsheet program isits capability of illustrating the need of each operating mode

Table 5Average solar heat gains through windows (kJ/hr).

Months Miami Las Vegas Vancouver Toronto Iqaluit

(Zone A) (Zone B) (Zone C) (Zone D) (Zone E)

Jan. 3878 3806 1260 2430 499Feb. 4435 4560 2318 3325 2105Mar. 4922 5266 3489 4076 3632Apr. 5126 6090 4430 4602 5835May 5514 6767 6047 5691 7118Jun. 5725 7303 6461 6172 6672Jul. 5723 6883 6323 5877 6150Aug. 5128 6257 5266 5346 4654

34 J. Zhang et al. / Energy an

nergy (q′) for each temperature-humidity bin can beetermined.

′ = Nbin × q (7)

In addition, the counted bin hours also enabled the estimationf weighted annual efficiency of the system. This value can be cal-ulated based on the weighted number of each bin hour of theear.

′ =∑ Nbin

8760× ε (8)

.5. Climate zone classification

The dual-core total recovery ventilator (TRV) is an existing prod-ct that resembles the proposed HERV. The TRV, according to theanufacturer’s recommendation, is feasible for markets with tem-

erate climate [18]. The proposed HERV was designed to contain built-in economizer, and hence, was also thought to be feasibleor other climates. The Köppen climate classification system waspplied to sort the cities of North America into various climaticones. This classification system was to further aid in the predic-ion of HERV behaviours in these general zones. The Köppen climatelassification system was introduced by a German climatologistamed Wladimir Köppen in 1990. With the temperature and pre-ipitation index, as well as the five vegetation groups defined bye Candolle, Köppen classified the world’s climate with three let-

ers [19]. The first letter represents a particular climate zone, whilehe second and third letters explain the precipitation and annualir temperature of that zone. The following presents the five majorlimate zones:

A) The tropical climate.B) The dry climate.C) The temperate climate.D) The continental climate.E) The polar climate.

.6. Control strategies

The project scope requires the HERV to be able to operate inour different modes: sensible, latent, dual-core, and economizer

ode. Therefore, it made the control, as well as the overall calcula-ions became more complex. As a result, simple control strategiesere developed and implemented into the spreadsheet tool to help

elect the appropriate operating mode. These controls evaluate theifference between the indoor and outdoor air conditions. The sen-ible mode is needed when moisture recovery is not needed, whilehe latent mode is needed if �T ≈ 0. Therefore, the dual-core modes desired only if both of the above conditions are met simulta-eously, while the system allows direct free-cooling if they are notet. For indoor set point temperature of 23 ◦C and relative humid-

ty of 50%, the conditions that triggered the economizer modere:

out ≤ 23 ◦C and wout ≤ 0.00871 kg/kg

. Results and discussion for the case study

.1. Sample house

The next step upon the completion of program description waso conduct a feasibility study for the HERV. The energy calcula-ions were carried out in the context of an airtight environment:he Archetype Sustainable House-B (ASH-B) located in Vaughan,

RSI 5.64 (R32)Wall (below grade) Durisol blocks

RSI 3.54 (R20)

Ontario. This house has achieved a LEED for Homes Platinum certi-fication, and it is currently used to demonstrate the potentials of anaffordable energy efficient house that can be mass-produced witha small ecological footprint [20]. The details of the house descrip-tion are listed in Table 4. The internal heat gain of the house wasmeasured to be 23.6 kW h per day [21] and was assumed to beconstant throughout the calculations. In contrast, the solar gain ofASH-B was obtained via the transient simulation program TRNSYS,as shown in Table 5. Furthermore, the required ventilation rate ofthe house was 0.0708 m3/s. The energy consumption for HRV andERV were 0.41 W/CFM. The unit price of natural gas from Enbridgewas $0.2658 per cubic meter (as of July 1, 2013), and the price ofelectricity from Toronto Hydro was $0.1325/kW h (as of May 1,2013).

In addition, a few assumptions were made for the case study:

(1) Effects attributable to condensation and freezing wereneglected.

(2) Cooling season set points: T = 23 ◦C and RH = 50%.(3) Heating season set points: T = 21 ◦C and RH = 30%.(4) SEER for air conditioner was assumed to be 15.(5) A new gas furnace was assumed for space heating, and the

corresponding efficiency was 78% based on RESNET MortgageIndustry National HERS Standards [23].

(6) Unit size 3 GE ECM motor was employed, which consumedapproximately 0.1 W/CFM at 0.0708 m3/s [24].

(7) The investment cost of the proposed HERV system was $2500,which was assumed according to the total cost of the compo-nents needed to assemble the prototype [25].

Sep. 4613 5633 4127 4251 3493Oct. 4515 4949 2685 3258 1770Nov. 3995 4202 1519 1867 552Dec. 3738 3575 1000 1737 206

J. Zhang et al. / Energy and Buildings 75 (2014) 430–438 435

Table 6Zone-by-zone analysis for the three mechanical ventilation systems.

Capital costs HERV ERV HRV

$2500 $1610 $1170

Annual cost savings ($) Operating cost ratio (%) Payback period (year)

Zone City HERV ERV HRV HERV ERV HRV HERV ERV HRV

A Miami 498 411 −95 5 21 704 5.0 3.9 –*

B Las Vegas 469 369 −22 5 23 125 5.3 4.4 –C Vancouver 155 50 −4 15 69 104 16.1 – –D Toronto 260 149 28 9 42 79 9.6 10.8 –

gurtTstyOecptoa

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3

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E Iqaluit 419 301 153

* ‘–’: Payback period is longer than 20 years or negative payback.

raphically based on the counted bin hours. This illustration allowss to better understand the potential of the defined heat/energyecovery ventilators. Five cities of North America were selected forhe case study, corresponding to the five Köppen climate types.ype-A climate zone (Miami) is characterized by humid and con-tantly high temperatures throughout the year [19]. Fig. 4 showshat the sensible mode might not be significant for 39.8% of theear, while the latent heat recovery was nearly always required.verall, the general requirement appeared to be squinting towardsnthalpy recovery. Cities that have temperate (e.g., Vancouver) orontinental (e.g., Toronto) climate in general have an outdoor tem-erature above 10 ◦C during their hottest months [19]. Fig. 4 showshat the economizer mode could be beneficial in Vancouver for 30%f the year, while Toronto had a lower frequency (20%) due to hotternd wetter outdoor condition.

Overall, the estimated demands showed that the house oftenequired dual-core mode to minimize energy demand attributableo outdoor air. However, this information might not reflect thectual saving potential of the heat recovery systems. For example,ual-core mode was required 91% of the year in Iqaluit, and it iselieved that the sensible part of this number was actually domi-ating. Therefore, even though the HRV did not recover latent heat,he dominated sensible portion could be satisfied 91% of the time,eading to a saving that would be better than the humid regionMiami).

.3. Cost savings of the house

The next step of the study aimed to determine the cost sav-ngs of the house based on the annual energy consumption of the

3.4% 4.7%

19.5

%

39.8

%

11.2

%

0.8%

56.8

%

84.2

%

0.0%

0.0%

M I A M I L A S V E G A S V A N C O U

MO

DE D

EMAN

D

Sensible Lat ent Dua

Fig. 4. Annual mode demand. (For interpretation of the references to color in th

5 24 37 6.0 5.4 7.6

house. Fig. 5 presents the energy consumption of the house in termsof the energy use for furnace, air conditioner, de-humidifier andhumidifier. For Miami, the house with the HERV required approx-imately 6014 kW h in order to maintain the house temperature atthe set point. In addition, the house with the ERV consumed 45% lessenergy for dehumidification than the HRV’s, and the cost associatedwith this difference was $506, as shown in Table 6. As mentioned,both the HRV and ERV were assumed to have the same potentialof sensible heat recovery, so a negative cost saving in the HRV-equipped house was attributed to the high demand in latent heatrecovery. In contrast, the HERV resulted in a saving of $87 higherthan the ERV’s. However, this benefit was offset by its high initialinvestment, resulting in a slightly longer payback time (about 13months).

Fig. 5 indicates that the sensible heating load was usually dom-inated, especially in cold regions. For example, the difference inenergy use between the HRV and ERV in Iqaluit and Las Vegas wererespectively 3% and 15%, meaning that the latent heat recoverybecame less important in cold areas. However, due to the high oper-ating cost for moisture control, the saving from the ERV in Iqaluitwas still $148 higher than the HRV. In both Vancouver and Toronto,the saving attributable to the economizer mode during cooling sea-son accounted for 7% and 3% of their total savings, as shown inTable 7. These savings further reduced the annual energy use andthereby shorten the payback time.

3.4. Sensitivity study

Upon the completion of the cost saving analysis, sensitivity anal-ysis was also conducted to verify the performance of the HERV in

9.3%

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67.5

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90.7

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20.4

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V E R T O R O N T O I Q A L U I T

l-core Economizer

is figure legend, the reader is referred to the web version of this article.)

436 J. Zhang et al. / Energy and Buildings 75 (2014) 430–438

Fig. 5. Energy consumption of the case study house. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

F pretatv

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TB

ig. 6. Energy consumption of the case study house (temperate climate). (For interersion of this article.)

ther regions across North America (Table 8). These results resem-les those in Table 6, especially for climate Type-A where theariations are small. The performances of the HERV were excel-ent in cities with temperate climate; however, some discrepancies

ere detected. The HERV was found to have a shorter paybackeriod than the ERV in both Los Angeles and San Francisco, but

onger in Atlanta. Based on the Köppen-Geiger climate type map fororth America [19], these two cities belong to a sub-climate that

s different from Atlanta; therefore, they possess different climateharacteristics. The sub-climates are defined by the second andhird letters of the Köppen climate classification system. Both Losngeles and San Francisco belong to Type-Csb, where the second

able 7enefits of free-cooling.

Zone City Cost savings ($) Percent saving(%)

Payback reduction(months)

C Vancouver 10 7 13.2D Toronto 7 3 3.6

ion of the references to color in this figure legend, the reader is referred to the web

letter s and the third letter b denote dry and warm summer, respec-tively. In contrast, Atlanta belongs to a slightly different sub-climateType-Cfa that is characterized by humid (f) and hot summer (a). TheHERV-equipped house in Atlanta needed 3112 kW h for latent load,which was higher than Los Angeles and San Francisco, as shown inFig. 6. Drawing a connection between Miami and Atlanta, it appearsthat the proposed HERV lost competitiveness against the ERV in thehumid regions because we were paying more for the same latentheat exchange.

3.5. Feasibility of the HERV system

To make a precise comparison between the energy efficiencyand the investment recovery of systems, the operating cost ratios(OCR) were determined, as shown in Tables 6 and 8. These ratiosmeasure the expense of the system as a percentage of revenue.

By implementing the ECM motors, the OCRs for the HERV werealways lower, and hence, it can be understood that the system wasmore cost-efficient than the single core systems. In both Miami andIqaluit, the HERV system required slightly longer payback period

J. Zhang et al. / Energy and Buildings 75 (2014) 430–438 437

Table 8Zone-by-zone analysis for the three mechanical ventilation systems (continue).

Capital costs HERV ERV HRV$2500 $1610 $1170Annual cost savings ($) Operating cost ratio (%) Payback period (year)

Zone City HERV ERV HRV HERV ERV HRV HERV ERV HRV

A West Palm Beach 473 381 −101 5 23 1161 5.3 4.2 –B Phoenix 311 223 −18 7 31 122 8.0 7.2 –B Albuquerque 338 246 −18 7 29 121 7.4 6.6 –C Los Angeles 220 127 −85 11 47 390 11.4 12.7 –C San Francisco 156 53 −38 15 68 153 16.1 – –C Atlanta 363 265 −31 7 30 139 6.9 6.1 –D Montreal 283 169 35 8 39 75 8.8 9.5 –

8

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D Halifax 230 120 2D St. Johns 228 119 3E Eureka 323 238 12

han the ERV even though the OCRs for the new concept were small.n comparison, the HERV was found to have the shortest paybackeriod in both Vancouver and Toronto, corresponding to 16.1 and.6 years. Therefore, the integrated HERV could be a feasible choiceor regions with either temperate or continental climate. The cal-ulated OCRs and payback periods also revealed that the HRV wasaking underwriting profit only in cold regions such as Iqaluit. The

RV, on the other hand, provided greater savings in Miami. Overall,oth the HRV and ERV systems experienced substantial increasef OCR in regions with temperate climate: the ERV system had anCR of 69% in Vancouver, while the HRV had 104%. Although the

nitial investments of the heat/energy recovery ventilators werencluded, the maintenance costs were excluded from the calcula-ions. The lack of available historical data for this new concept washe prime reason of this exclusion.

. Conclusions and future works

In this study, the feasibility of an integrated heat and energyentilator (HERV) with a built-in economizer was evaluated quan-itatively using an Excel based analysis tool. The calculated resultshowed that the proposed HERV was recommended for bothemperate and continental climates. In addition, the HERV oftenesulted in a lower OCR, however, the system sometimes experi-nced a substantial loss of competitiveness against the ERV due tots high capital cost (e.g., Miami). Results also revealed that the ERV

as suitable and recommended for hot and humid regions, whilehe HRV system was more efficient in cold regions. With the currenteaning towards energy conservation, the proposed approach isaluable for future net-zero energy building design in North Amer-ca. In theory, the findings from this paper contribute to the field ofnergy conservation by providing a preliminary study to supporthe pending thought that integrating the HERV ventilation systemith an economizer could be promising. In practice, the develop-ent of Ebat provides an easy-to-use and yet, editable analysis tool

or non-technical users to provide a quick estimate of system per-ormance for evaluation without having an expert to develop andun a detailed simulation. Finally, the performance data of the HRVnd ERV from past research was used as the default data in the Excelool. The sensible and latent efficiencies in the tool were designedo be replaceable by the users in the future. As part of this inves-igation, a detailed TRNSYS model will be developed, followed byurther experimental results.

cknowledgements

The authors would like to acknowledge the financial sup-ort from the Natural Sciences and Engineering Research Council

[

10 47 79 10.8 13.4 –9 47 74 11.0 13.5 –5 22 35 7.7 6.8 9.3

(NSERC) of Canada Smart Net-Zero Energy Buildings Research Net-work (SNEBRN), MITACS/Accelerate Ontario, and ASHRAE.

References

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[2] Natural Resources Canada, Energy-Efficient Homes, 2013, Retrieved February7, 2013 from http://www.nrcan.gc.ca/energy/efficiency/housing/home-improvements/4995.

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