Development of a Trade-off Path for HVAC National Energy Code for Buildings 2011 Compliance

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1 Development of a Trade-off Path for HVAC Natonal Energy Code for Buldngs 2011 Complance Elsabeth Grgs 1, Mchel Parent 2, and Patrque Tardf 1 1 Canadan Codes Centre, Natonal Research Councl, Ottawa, Ontaro 2 Technosm Inc., Sant-Jean-Chrysostome, Québec, Canada 1 Introducton Abstract In developng the 2011 Natonal Energy Code for Buldngs (NECB), the need to smply dentfy the performance of a proposed heatng, ventlatng and ar-condtonng (HVAC) system relatve to a prescrptve buldng s HVAC system was dentfed. Ths paper dscusses the development of the trade-off paths for HVAC, and the analyss conducted pror code publcaton and durng the development of an Excel based trade-off path tool. The trade-off path developed, whch consdered the equpment and controls of the entre systems, allows a mechancal desgner to examne a system desgn and evaluate the overall performance for code complance. Code Development The Canadan Commsson on Buldng and Fre Codes (CCBFC) develops the Natonal Model Constructon Codes through a consensus-based process that reles on the voluntary contrbutons of publc and prvate sector experts from across Canada. Under the gudance of the CCBFC, nne standng commttees revew and develop proposed techncal changes to the Codes before they are submtted for publc revew. The changes must then be approved by the CCBFC before publcaton by the Natonal Research Councl of Canada (NRC). (CCC, 2014) The techncal content of the Codes s developed by the standng commttees of the CCBFC. Lke the Commsson, the standng commttees consst of volunteers from three sectors (the ndustry, the regulatory communty and general nterest groups) and from across the country. These members brng ther techncal expertse and experence to the code development system. The standng commttees make recommendatons on the techncal content of the codes to the CCBFC and t s the CCBFC that makes the fnal decson on the content. There are nne standng commttees. Typcally, the standng commttees conduct ther work through task groups. The Standng Commttee on Energy Effcency n Buldngs (SCEEB) was establshed n 2007 to complete the techncal update of the 1997 Model Natonal Energy Code for Buldngs (MNECB) (CCBFC NRC, 1997). The frst meetng was held n December 2007, and the work proceeded on an accelerated bass to produce the 2011 Natonal Energy Code for Buldngs (NECB) (CCBFC NRC, Natonal Energy Code for Buldngs, 2011). The typcal code development cycle s 5 years. The NECB s enforceable when adopted by provnces and terrtores. The requrements must be benefcal from a cost and mpact analyss, enforceable and constructble. Beng a code, the 2011 NECB dffers from an ncentve program n that t addresses mnmum requrements to be broadly appled for all new constructon of buldngs covered by Part 3 of the Natonal Buldng Code (NBC) (CCBFC NRC, Natonal Buldng Code of Canada, 2010). Labellng or ncentve programs may use a code as a benchmark from whch to evaluate performance mprovements, such as what was done by LEED Canada (Canadan Green Buldng

2 Councl, 2014) and NRCan s Commercal Buldngs Incentve Program (CBIP) (OEE, 2006) wth the 1997 MNECB. Part 5 of the NECB 2011 addresses HVAC systems and s concerned wth the HVAC equpment, the controls and components formng part of an HVAC system, and the nterfaces between them. The scope of ths part ncludes equpment szng, equpment effcency, ar dstrbuton systems, fan system desgn, ar ntake and outlet dampers, ppng nsulaton, pumpng system energy use, temperature control, heat recovery and, shut-off and set-back controls. For the 2011 NECB, the Part 5 techncal update work was lead by the Task Group on HVAC and Servce Water Heatng (TG-HVAC) NRC s Insttute for Research n Constructon (NRC-IRC) provdes techncal, research and admnstratve support to the CCBFC and ts commttees, as well as, to the Natonal Model Constructon Code Documents development system. Polcy drecton of the 2011 NECB The CCBFC provded polcy drecton for the 2011 NECB. The polcy drecton was developed usng nput from the SCEEB and followng consultatons wth the Provncal/Terrtoral Polcy Advsory Commttee on Codes (PTPACC) (NRC, 2014). A notable polcy drectve from the PTPACC was that the sole objectve of the 2011 NECB s energy based (.e. lmtng excessve energy use by a buldng). By contrast, the NBC has objectves relatng to safety, health, accessblty and fre and structural protecton of buldngs. The NECB addresses excessve use of energy used by the buldng. It does not codfy factors and costs related to energy source and local varatons. Some provsons do vary dependng on clmate zone as determned by heatng degree days. (CCBFC NRC C. C., 2013) The NECB s also n an objectve-based format. Code users have the choce of usng the acceptable solutons prescrbed n the codes or demonstratng that a proposed alternatve soluton provdes at least an equvalent performance. Convertng the 1997 MNECB to an objectve-based format has made t more accommodatng to nnovaton by clarfyng ts scope as well as the ntent behnd ts requrements. Each code provson s now supplemented by clearly stated objectves, functonal statements and ntents. Impact for Part 5 HVAC In the 1997 MNECB, there was no opton for HVAC other than prescrptve or full buldng modelng to demonstrate complance. In developng the 2011 NECB, the TG-HVAC at ther frst meetng revewng the 1997 MNECB and dentfed a need for a new focus on equpment as part of the HVAC system n the buldng. The change to objectve based requrements, hghlghted to the TG-HVAC, the mportance of acceptablty of the entre system n determnng HVAC complance. At ther second meetng, ths approach was developed further wth the presentaton of a possble method for calculatng overall systems effcency, by nputtng the ndvdual component effcences nto a formula wth weghtng factor for each component. From there the trade-off path was developed to provde an acceptable soluton for HVAC whch consdered the system energy performance. Ths approach was also appled to the Servce Water Heatng system of Part 6 but for questons of length s not ncluded n ths paper. Part 5 of the 2011 NECB therefore offers three complance optons wthn the acceptable solutons. The smple prescrptve path, whch s lke a recpe for complance: To comply wth the NECB HVAC requrements, smply do x and y. The trade-off path, whch consders HVAC system effcency as a whole, provdes more flexblty than the prescrptve requrements. Use of the trade-off opton n Part 5 s restrcted to HVAC systems only. No tradng s permtted wth other buldng parameters such as lghtng or envelope components. To accomplsh tradng between NECB Parts, the thrd opton the performance complance path

3 must be used. In the performance path, a whole reference buldng bult accordng to the prescrptve path requrements s compared to the proposed buldng bult accordng to the performance path provsons. Ths paper descrbes how the trade-off path was developed from ths concept of the TG- HVAC, the valdaton completed and consderaton for ncorporaton nto a code. 2 Methodology The trade-off path was based on the concept that a system s overall or total effcency wll be dependent on the components used and takes these nto consderaton. For example, the effcency of heatng ventlaton ar can be traded aganst how that ar s delvered to a space. Consderng the effcency of the system as a whole wthn Part 5, rather than of ndvdual components, s a change relatve to the 1997 MNECB for HVAC desgners. To develop the trade-off path, a revew of other strateges was conducted, the prescrptve values were revewed, the mpact of ndvdual components was establshed and smplfcatons for ncorporaton nto the code were consdered when requred. 2.1 Revew of other approaches for HVAC At the tme of development there were some examples of European standards movng the drecton of system effcences such as pren for SHW system effcences and pren for HVAC systems effcences. (CEN, 2005) These standards are used n mplementng the European Energy Performance for Buldngs Drectve (EPBD) (European Parlament and of the Councl, 2002). However at the tme, even draft standards such as pren dd not prescrbe calculaton procedures for system effcences but only presented possble alternatves. The draft standards offered a good vew nto the potental complextes of defnng global effcences for HVAC systems wth nearly 40 dfferent mechansms dentfed as havng an mpact on the energy requred by a system to meet ts load. It also mapped these mechansms to over 20 dfferent types of HVAC systems. In the UK, mplementaton of the EPBD does not go through smplfed analytcal equatons for system effcences but rather through a smplfed smulaton tool offerng an alternatve to a full performance approach (SBEM Smplfed Buldng Energy Model). System effcency for complex HVAC systems s usually not dependent only on ts components or controls but also on the loads beng served. A clear example of ths s a constant ar volume (CAV) system servng a constant load: as are observed n nternal zones. In such a confguraton, ths system provdes a potentally good performance. However, the same system servng zones wth varyng loads (nternal, external) would offer a potentally poor performance. 2.2 Prescrptve requrements of the 2011 NECB Snce the startng pont for the trade-off path was the code prescrptve requrements, establshng the prescrptve requrements for the 2011 NECB was an mportant step. When a code prescrptve requrement exsted, t was envsoned that t would only be a matter of defnng the value of the baselne effcency and producng varatons from that value. In practce, ths defnton was adapted and some absolute values rather than relatve effcences were used for smplcty n defnng a component. For example, t was determned to be easer and much more natural for a user to defne the actual total statc pressure of a system rather than enter an artfcal effcency defned as the total statc pressure dvded by a reference code statc pressure. In other nstances, a component mght not have any numerc quantfcaton attached to t. In these cases, t was necessary for a scale value to be defned. Most control components fall n

4 ths category. For example, there are no numercal values of effcences ntrnscally lnked to the control logc used for modulatng the supply ar of a varable ar volume (VAV) system. In such nstances the average mpact of the component for the varous locatons was obtaned and effcency values defned. From a code user s pont of vew, lookup tables for defnng the value to be used n the calculatons are provded. For mnmum equpment effcences, the 2011 NECB set the prescrptve value to current practce based on the medan of sales nformaton. A revew of equpment sales was completed and equpment effcency at the sales medan was determned. In certan cases, such as wth coolng equpment, f a techncal lmtaton exsted or nsuffcent Canadan sales nformaton was avalable, the requrements were set to the level of the Energy Effcency Act (EE) regulatons (NRCan, 2014). The NECB prescrptve requrement s hgher than the EE regulatons, and mples that, f the smple prescrptve path s used, a desgn s not consdered Code-complant f t ncludes equpment wth effcences below the NECB requrements. The reducton of equpment effcences to the mnmum level set by the EE regulatons would be permtted when usng ether the full buldng performance path or the newly created trade-off path whch was beng developed. 2.3 Method to determne systems and components to be ncluded n the tradeoff path To develop a total system effcency code complance path, a survey of the more commonly used HVAC systems and components was conducted. The frst attempts were focused on provdng a smple and easy to use complance approach. More complex systems would be nvestgated f the ntal results were favorable or t was deemed requred. Factors that affect system effcency such as zonng, outdoor ar flow and termnal flow are not consdered n ths approach snce there were many varatons possble and the path was ntended for code complance. These smplfcatons are taken wth the knowledge that the trade-off path could not be used to estmate absolute energy use. Also, alternatve heat sources and non-standard systems would not be permtted to demonstrate complance wth the trade-off path. To determne systems and components, the approach would focus on usng fndngs from EE4 and equest modelng of ndvdual components that were shown to have a sgnfcant mpact on system effcency (CANMET, 2013). A sngle archetype buldng was used as a standard n developng an equaton that would accurately descrbe an overall HVAC system effcency relatonshp. For systems and components consdered, tests were conducted. The equaton developed consder each components effcency n the smulaton and relatve to the system s overall performance. To select an archetype buldng, several methods were consdered. The TG-HVAC sought to quantfy the relatve mpact of components effcences on the overall system effcency. Prevous work done by Unted States Department of Energy (US DOE) towards developng representatve archetype was deemed to be a vald startng pont. (Offce of Energy Effcency and Renewable Energy, 2014) The medum offce buldng developed by the US DOE was selected as the bass for testng all the systems and components wthn ths project. Ths buldng s relatvely smple but large enough to reasonably accommodate all of the systems and components found to be potentally relevant from the ntal EE4 and equest modelng. In order to determne ndvdual component mpact on effcency, the archetype medum offce buldng was therefore modelled n equest. The humdfcaton set pont was 25% RH. 30 year CWEC weather fles from EE4 were used for smulatons at the followng 6 locatons: Vancouver, Wnnpeg, Toronto, Yellowknfe, Montreal and Halfax

5 2.4 Determnng Indvdual Component Impact on Effcency A methodology was needed to quantfy the mpact of each component on the system effcency. Ths could have been acheved analytcally through the development of relatonshps between a component energy mpact and the overall energy use, or by runnng a seres of smulatons and correlatng the results. Ths later opton was retaned due to the large number of components and ther complex nteractons makng analytcal models mpractcal. An ntal approach to determne ndvdual components mpact on effcency was based on a reference smulaton run for every system type, n every clmate zone. Varatons on each ndvdual component were then mplemented to determne ther overall mpact. There were 162 reference cases when consderng all selected clmate zones and HVAC system types. The estmated total number of smulatons requred to test all possble confguratons under all clmate zones amounted to approxmately An automated Excel spreadsheet was developed to comple all the nformaton from the numerous smulatons. Next, a system effcency equaton to map those results nto a set of analytcal equatons was establshed. These equatons predct the system effcency based solely on the ndvdual effcences of the components. The results demonstrated that the changes could not be correlated by a smple polynomal form. Changes n the coeffcents showed no dentfable trends and all attempts to use curve fttng algorthms faled. A second approach was therefore used. Instead of tryng to assess the absolute value of the system effcency, an approach based on relatve changes was consdered. Under ths approach, a reference system effcency was establshed usng a smulaton. Followng ths, the mpact of a change n a specfc component effcency was mapped aganst the changes n overall system effcency. Therefore, the resultng equaton dd not quantfy the expected global effcency based on a complex set of weghtng factors but rather focused on the devaton from a gven reference effcency due to changes to ndvdual components. One major advantages of ths modfed approach was analyss smplfcaton: a sngle component s analyzed at a tme. For each component, a set of 5 runs, (1 baselne run and 4 varatons) were conducted. Relatng ndvdual component effcency to system effcency was accomplshed wth an error mnmzaton routne. Ths task was programmed n spreadsheets used to comple the results. Coeffcents for each combnaton of system and components for each of the 6 clmatc locatons studed were obtaned. Mantanng the coeffcents prevously descrbed for each zone would have resulted n values. To reduce the number of parameters needed and to be publshed n the code, the system effcency was analysed wth the goal of obtanng a sngle set of coeffcent for a gven component regardless of the locaton. Heatng Degree-Days (HDD) and/or the Coolng Degree-Days (CDD) and Total Degree-Days (TDD) for the representatve ctes from the NBC tables were used. TDDs were used when a component was affected by both HDDs and CDDs and errors were mnmzed when accountng for both terms smultaneously. Quadratc curve fttng was used. In each case, the curve fttng routne was appled usng ndependently HDD, CDD and TDD. The best ft was selected for each component. 2.5 Translatng the mpact of ndvdual component effcency to a system effcency for code complance The methodology presented n Sectons 2.3 and 2.4 provded equatons relatng ndvdual components effcences to system effcency. One more step was requred for ths nformaton to be useful wthn the scope of an energy code. The value of a gven system effcency provded a benchmark aganst whch, under standardsed condtons, system could be compared to the mnmum code requrements. The trade-off path uses a system-to-same-system comparson. Therefore the complance of a system was assessed by subtractng ts effcency

6 to that of the reference system. A postve result demonstrates complance. The resultng equaton provded n the NECB s Equaton (1): found n Secton 3 of ths paper. Ths approach, n whch the energy consumpton of the proposed system must be less than that of the reference system, s consstent wth the full buldng modelng methodology of Part 8 of the 2011 NECB. Snce nether the MNECB nor the 2011 NECB Part 8 provde credts for changes to schedulng, any components whch has ts effcency based on a schedulng parameter was excluded from the trade-off system effcency approach. Its effcency was set to dentcal values for the proposed and reference systems. Specfcally the followng components are based on schedulng: fan control, heatng set pont control and coolng set pont control. The decson to allow or not to credt for ndvdual components was consdered to be coherent wth that permtted under an updated performance path of Part 8 the 2011 NECB. 3 Results Once the methodology was developed and the prescrptve requrements of the 2011 NECB had been submtted for publc revew, the coeffcents for the equaton were recalculated based on the fnal prescrptve requrements of the 2011 NECB. The trade-off path n the 2011 NECB ncludes 27 typcal system types, such as constant-volume reheat and packaged varable volume. They are lsted n Table 1. Dependng on the system, up to 32 nput parameters can be traded thus allowng small adjustments to the HVAC system to be made wthout havng to complete full buldng performance path modelng. The components n the 2011 NECB are lsted n Table 2 and nclude heat source generator effcency, heat-recovery system effcency, return fan motor effcency, ppng nsulaton and pressure losses,. The general equaton used to determne complance wth the trade-off path s Equaton (1). The frst summaton n the equaton characterses the effcency of the proposed system whle the second evaluates the base value from the prescrptve requrements. The α, β and γ are weghtng factors whose values for each component and system are lsted n look-up tables. Other look-up tables are provded to help determne whch components must be ncluded as part of a partcular system type. Although the calculatons can be completed by hand, t s lkely that a computer spreadsheet wll be used. The trade-off ndex (HVAC TOI ) acheved must be greater than 0 n order to demonstrate complance. Where: HVAC TOI ToV ToV 32 2 BaV BaV = counter for number of components ncluded n proposed buldng's HVAC system, α = frst order weghtng factor lnkng the component effcency varatons of component to the system effcency varatons determned by referrng to tables β = second order weghtng factor lnkng the component effcency varatons of component to the system effcency varatons determned by referrng to tables ToV = trade-off value of component for the proposed buldng: determned by referrng to tables BaV = base value for component for the reference buldng: determned by referrng to tables; and γ = factor to determne components to be ncluded determned by referrng to tables for the gven HVAC system. (1)

7 Table 1: HVAC System Descrpton HVAC-1 Bult-up varable-volume HVAC-2 Constant-volume reheat HVAC-3 Packaged sngle duct sngle zone HVAC-4 Bult-up sngle duct sngle zone HVAC-5 Packaged varable-volume HVAC-6 Packaged constant-volume wth reheat HVAC-7 Bult-up celng bypass VAV HVAC-8 Packaged celng bypass VAV HVAC-9 Powered nducton unt HVAC-10 Bult-up mult-zone system HVAC-11 Packaged mult-zone system HVAC-12 Constant-volume dual-duct system HVAC-13 Varable-volume dual-duct system HVAC-14 Two-ppe fan col wth optonal make-up ar unt HVAC-15 Four-ppe fan col wth optonal make-up ar unt HVAC-16 Three-ppe fan col wth optonal make-up ar unt HVAC-17 Water-loop heat pump wth optonal make-up ar unt HVAC-18 Ground-source heat pump wth optonal make-up ar unt HVAC-19 Inducton unt two-ppe HVAC-20 Inducton unt four-ppe HVAC-21 Inducton unt three-ppe HVAC-22 Packaged termnal AC splt HVAC-23 Radant (n-floor, celng) wth optonal make-up ar unt HVAC-24 Actve chlled beams wth optonal make-up ar unt HVAC-25 Unt heater HVAC-26 Unt ventlator HVAC-27 Radaton wth optonal make-up ar unt Table 2 : Component Trade-off Values, ToV, for the Proposed Buldng ToV1 Supply fan mechancal effcency ToV2 Supply motor effcency ToV3 Return fan mechancal effcency ToV4 Return fan motor effcency ToV5 Supply temperature control. ToV6 Arflow control effcency ToV7 Supply fan total statc pressure ToV8 Supply duct nsulaton ToV9 Return fan total statc pressure ToV10 Heatng col desgn temperature drop ToV11 Baseboard heater desgn temperature drop ToV12 Boler/furnace/heat pump heatng effcency ToV13 Chllers/drect expanson system/heat pump coolng effcency ToV14 Rejecton fan nput power rato ToV15 Coolng by drect use of outdoor ar (ar economzer) ToV16 Outdoor arflow control ToV17 Exhaust ar heat-recovery effcency ToV18 Coolng by ndrect use of outdoor ar (water economzer) ToV19 Ppng nsulaton hot water ToV20 Ppng nsulaton chlled water ToV21 Ppng pressure losses hot water ToV22 Ppng pressure losses chlled water ToV23 Pump mechancal effcency hot water ToV24 Pump mechancal effcency chlled water ToV25 Pump motor effcency hot water ToV26 Pump motor effcency chlled water ToV27 Hot water pump control ToV28 Chlled water pump control ToV29 Hot water loop temperature control ToV30 Chlled water loop temperature control ToV31 Hot water flow control ToV32 Chlled water flow control

8 4 Dscusson and Analyss The followng secton detals three types of analyss completed for the trade-off path. The frst s a peer revew of the coeffcents pror to publcaton of the 2011 NECB. The second s a supplementary analyss completed for a proposed publcaton of the 2015 NECB. The thrd conssts of fndngs from on-gong work n developng a macro-enable Excel tool to assst n demonstratng complance through the trade-off path. The values predcted by the trade-off path were verfed for range by comparng to a mnmum Part 5 HVAC prescrptve complant system. Many energy modelers and mechancal engneers provded comments throughout the valdaton process. The TG-HVAC and SCEEB members were most actve but feedback was also provded by nterested ndvduals. Ths partcpaton was facltated through meetngs or specfc analyss as noted below. 4.1 Analyss pror to code publcaton Enermodal Engneerng performed a peer-revew of the coeffcents pror to code publcaton. The varables, along wth a correspondng lst of coeffcents, were suppled. The mpact on system effcency of changng each trade-off varable from a base (reference) value was examned to determne for trendng n the proper drecton. Each system and varable was tested for the Toronto regon. An mprovement over the reference BaV (such as ncreasng motor effcency) would theoretcally produce a postve trade-off ndex, and the opposte was expected for makng a varable worse than the BaV. The results showed the trade-off varables were generally workng as ntended. However certan changes were recommended. Lowerng the temperature dfference of reheat cols resulted n a 1 x10-4 ncrease n effcency and therefore ths temperature dfference was removed from the lst of varables that could be traded off. Smlarly, removal of cold thermal storage showed an ncrease n system effcency. Snce cold thermal storage s not a common feature n buldngs t was also removed from the trade-off path. Orgnally, ncreasng the baseboard temperature drop from 20 F to 30 F lowered the system effcency. Ths effect was not the antcpated result as a hgher temperature dfference typcally ndcates more effectve heat transfer and less pumpng when a lower flow rate s requred. Furthermore, gong to a hgher temperature drop meant the boler would operate at hgher part load for shorter perods. The older part-load curve of DOE2 could also have been a factor. Operatng at hgher part load usually equates to hgher effcency for regular effcency bolers. A new set of polynomal coeffcents were developed wth a narrower range based on 20 F. Smlarly ncreasng the heatng col desgn temperature drop of a unt ventlator system lowered the system effcency. A new set of polynomal coeffcents were developed based on 20 F, rather than on the orgnal 40 F. The behavour of two values were found to produce results consstent wth modelng software but not desred for the smplfed approach of the trade-off path. Namely, ncreasng the pump mechancal effcency n an nducton unt (two ppe) system resulted n lowered system effcency. The behavour was determned to be reflectve of the whole buldng modelng results 1. To encourage the use of hgher effcency pumps, new coeffcents were developed whch took advantage of the decreased electrcal pumpng energy, whle decreasng the effect of the ncreased heatng energy. The result was more representatve of current desgn 1 Hgher mechancal effcency means there s more waste heat gong from the pump nto the buldng, causng the boler to run less than t would f the pump had a hgher effcency. Snce the boler used n the models s regular, non-condensng, 80% effcent boler the nteractve effect between waste heat generaton, and boler operaton was amplfed.

9 practces, where bolers tend to have a hgher effcency, and where nteractve effects between pump heat loss and ncreased boler load would be mnmal. Smlarly, decreasng the ppng pressure losses lowered the system effcency. 2 To encourage the desgn of more effcent ppng systems, new coeffcents were developed. The remanng components and systems ncluded n the trade-off path are presented n Tables 1 and Addtonal analyss for the proposed 2015 code As code requrements change, the trade-off path needs to reflect these changes. For the 2015 edton of the Code, a number of changes were proposed to the ppng and duct requrements n Part 5 (HVAC) by the Task Group on Ppng and Duct Insulaton. Modfcatons were made to the thckness requrements to algn the latest verson of the NECB wth the requrements of ASHRAE (ASHRAE, 2010) These changes were submtted for publc revew n the fall of The TG-HVAC of the 2011 code made a comprehensve revew of the HVAC equpment effcency (Table ). Where the effcency of equpment covered by the Energy Effcency (EE) Regulatons had surpassed those of the NECB, the Code requrements were algned wth those of the EE regulaton. It was proposed that Part 5 of the 2015 edton of the NECB have the followng new requrements: heatng effcency for packaged rooftop unts (RTUs), maxmum pumpng allowances for hydronc system pumps, and performance requrements for heat rejecton equpment (chllers). The concept of the Trade of Path (TOP) s unchanged from the 2011 edton of the Code. It s based on the overall systems effcency of 27 HVAC systems. If a system s not lsted n the Code, complance cannot be demonstrated usng the trade-off path. 4.3 Analyss durng tool development An Excel macro enable tool s under development by NRCan to ease demonstraton of complance wth the Part 5 trade-off path. 5 Conclusons A system approach to HVAC was developed and ncluded n the 2011 NECB as Subsecton 5.3. The trade-off path for HVAC was entrely new relatve to the 1997 MNECB. The approach recognzes the relatonshp between ndvdual components of an HVAC system and overall performance of the entre system. It also allows evaluaton of complance wthout full buldng envelope or lghtng desgn nformaton. Wth a system approach the 2011 NECB therefore had three complance paths for HVAC: a prescrptve path, a trade-off path that allows for trade-off of ndvdual parts, and a performance path. Ths permts greater desgn flexblty for the mechancal desgner to demonstrate complance wthn the acceptable solutons. Gven the complexty of predctng energy use, the trade-off path n ts current form should be consdered as t was ntended: as a complance mechansm, rather than an energy assessment method. The pass/fal provded by the ndex s relatve to the mnmum acceptable HVAC system permtted by the code s prescrptve requrements. The valdaton process 2 A lower pressure loss allows less pumpng energy to be used to move the same volume however the results were representatve of buldng modelng software output. Hgher pressure losses means there s more waste heat gong nto the buldng, causng the boler to run less than t would f the losses were lower. Snce the boler used n the models s regular, non-condensng, 80% effcent boler, the nteractve effect between waste heat, and boler operaton was amplfed.

10 of the trade-off path coeffcents solated modelng result of ndvdual components n an HVAC system. The effect of ndvdual components less sgnfcant n a whole buldng smulaton but were hghlghted when the HVAC system alone was analyzed. Notably, the authors fnd nterestng how certan varables produced results were expected by some energy modellers and mechancal engneers nvolved but not others. Future work may examne the proper balance between ease of complance, adaptablty of code provsons to technology changes and the level of detals needed. Agreement throughout dscussons was that not consderng the nter-relatonshp of elements of an HVAC system can lead to a poor energy performance. Gven the purpose of the NECB to reduce excessve use of energy of buldngs by provdng a mnmum performance level, the trade-off path s deemed useful n facltatng that determnaton. 6 Nomenclature HVAC Heatng, Ventlatng and Ar-Condtonng MNECB Model Natonal Energy Code for Buldngs NECB Natonal Energy Code for Buldngs SCEEB Standng Commttee on Energy Effcency n Buldngs TG Task Group 7 Acknowledgements Canadan Natonal Code development s a mult-stakeholder process and t would be dffcult to acknowledge all nvolved. Ths document draws heavly on the work of the Task Group on HVAC and Servce Water Heatng of the 1997 Standng Commttee on Energy Effcency n Buldngs. Task Group members were Peter Sectakof (Char), Deter Bartel, John Goshlak, Rchard Burke, Heather Haynes, Charles Coté, Strlng Walkes, Charles Coté and Mchel Tardf, and the SCEEB Char was Ken Newbert. Mchel Lamanque, Jm Comtos and Raymond Boulay of the Offce of Energy Effcency of NRCan are acknowledged for ther support of the development process. Mhalo Mhalovc s also thanked as he served as techncal advsor to the TG at the begnnng for the development of the trade-off paths. Enermodal Engneerng s acknowledged for ther peer revew of the trade-off path coeffcent of the 2011 NECB. 8 References ASHRAE. (2010). Standard , Energy Standard for Buldngs Except Low Rse Resdental Buldngs. Atlanta: ASHRAE. Canadan Green Buldng Councl. (2014, February). Gong Green wth LEED. Retreved from LEED: ED/default.htm CANMET, Natural. Resources Canada. (2013, 11 16). EE4. Retreved 03 02, 2014, from Software Tool: CCBFC NRC, (1997). Model Natonal Energy Code of Canada for Buldngs. Natonal Research Councl of Canada, Ottawa. ISBN CCBFC NRC, (2010). Natonal Buldng Code of Canada. Natonal Research Councl of Canada, Ottawa., ISBN CCBFC NRC, (2011). Natonal Energy Code for Buldngs. Natonal Research Councl of Canada, Ottawa. ISBN

11 CCBFC NRC, (2013, 02 04). ARCHIVED - Revew of Canada's Natonal Energy Code for Buldngs. Retreved 03 02, 2014, from Natonal Codes: Canadan Codes Centre, (2014, 03 02). Canada's Natonal Model Constructon Codes Development System. Retreved from Natonal Codes : CEN, T. C. (2005). Heatng systems n buldngs - Method for calculaton of system energy. European Parlament and of the Councl. (2002). Drectve 2002/91/EC of the European Parlament and of the Councl of 16 December 2002 on the energy performance of buldngs. Retreved from Europa: e_doc=drectve&an_doc=2002&nu_doc=91 NRC, Canadan Codes Centre(2014, 03 02). PTPAAC Terms of Reference. Retreved from Natonal Codes: NRCan, OEE (2014, 03 02). Gude to the Energy Effcency Regulatons. Retreved from Energy - Regulatons and Standards: NRCan, OEE, ( 2006, 03 03). Commercal Buldng Incentve Program (CBIP) for New Buldngs. Retreved 02 03, 2014, from Commercal and Insttutonal Buldngs: ca/commercal/fnancal-assstance/new-buldngs/ndex.cfm?attr=20 Offce of Energy Effcency and Renewable Energy, (2014, 03 02). Improvng the energy effcency of commercal buldngs. Retreved from energy.gov: