PAPER 1 KOMPARASI NILAI PARTIAL-OTTV PADA EAST-WALL BERBASIS U-VALUE= 2,6 DENGAN U-VALUE= 1,6 (EAST WALL’S PARTIAL OTTV COMPARISON BY USING U-VALUE OF 2,6 AND U-VALUE OF 1,6)
Wied Wiwoho Winaktoe E-mail:
[email protected]
Appeared in: (1)Jurnal Permukiman, Volume 4 No. 2 September 2009, ISSN : 1907-4352, Akreditasi No. 222/AU1/P2MBI/08/2009. Link: http://www.pu.go.id/uploads/services/infopublik20131119124519.pdf This journal is under ministry of public housing who is responsible for OTTV/green building/energy efficient development in Indonesia (2) https://www.scribd.com/doc/217218770/jurnal-permukiman With 578 views
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ABSTRACT
Theoretically, East-wall (object of simulation) is required to have u-value of 2.0 which is difficult to obtain since the structure of popular wall (plaster-brick-plaster) will reach uvalue of 2.6. The increasing quantity of u-value denotes the decreasing quantity of resistance value (R) since 1/R = u-value meanwhile the consequence of the increasing uvalue towards heat-transmittance value is interesting to find out because u-value contributes to overall thermal transmittance value (OTTV). It is therefore this research is directed to find the impact of either u-value > 2.0 (i.e. 2.6) or u-value < 2.0 (i.e. 1.6) towards the OTTV at East-wall. Procedures involve certain steps: (a) modelling East-wall with u-value of 2.6; (b) modelling East-wall with u-value of 1.6; (c) put u-value of 2.6 into partial OTTV calculation using software of OTTV v1; (d) put u-value of 1.6 into partial OTTV calculation using software of OTTV v1. Results are (1) u-value of 2.6 produces partial OTTV of 21.28 W/m2 and (2) uvalue of 1.6 produces partial OTTV of 12.95 W/m2 . These come up with the conclusions that (1) u-value < 2.0 tends to produce smaller partial OTTV compared to u-value > 2.0 and (2) the smaller u-value created then the smaller heat-transmittance will be at the partial OTTV of East-wall. Keywords: thermal, transmittance, u-value, wall, OTTV
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INTRODUCTION Hot humid tropics Indonesia is categorized as hot humid tropics with[ 1:2]: radiation >900 W/m2 [ 2 ], temperature 470 -900 F (∆T/bulan = 22 0 , ∆T/hari = 60 -130 ), relative humidity (RH) 18 mm/Hg, precipitation 60 inch/thn” , however the wind velocities are unstable (0 or 30 m/sec) (SATWIKO, et al, 2000). Hot humid climate is the most challenging climate to deal with; the best expectation would be the equal condition between shaded outdoor and indoor (SZOKOLAY 1980:334).
Partial OTTV OTTV is a standard procedure to estimate energy usage in a building by observing that the heat gain which is transferred through envelope should ≤ 45 W/m2. This procedure is a mandatory component in construction service (ANONIM 1998). Similar to that, American Architects also included energy consideration into their practices as shown by several technical documents, e.g. energy economics (ANONIM 1982a), HVAC (ANONIM 1982b), energy evaluation (ANONIM 1982c), energy and site (ANONIM 1982d), and energy analysis (ANONIM 1982e). In Indonesia, OTTV was mandatory since 1993 (ANONIM 1993); furthermore, its calculation was enhanced in year 2000 (ANONIM 2000). The latest OTTV equation included several variables which 1
Victor OLGYA Y, 1963, Design with Climate, USA: Princeton University Press. 175 2 Prasasto SATWIKO, 2004, Fisika Bangunan I, Yogyakarta: Penerbit Andi.
can be determined by default or custom calculation. Partial OTTV (OTTVi ) is a calculation on certain façade prior contributing into total OTTV result. Its equation is as follows: OTT Vi
α Uw WWR TDEk SC SF Uf ∆T
=
α[(Uw x (1-WWR)] x TDek + (SC x WWR x SF) + (Uf x WWR x ∆T)
= solar absorbtance = opaque wall transmittance (Watt/m2 .K). = window to opaque wall ratio = temperature differential equivalent (deg K). = shading coefficient = solar factor (W/m2) = fenestration transmittance (W/m2 .K). = indoor-outdoor temperature differences; ∆T = 5 deg C.
Software OTTV ver1 U-value is one of the input which obtained through routines in OTTVi ; to overcome time consuming in that calculation then it is important to develop a algorithm which is able to give u-value output in timely manner. Based on that demand, software OTTV ver 1 (WINAKTOE, 2008) was formulated to increase designer/architect ability towards good time management for any uvalue calculation routines. Theory The whole building is suggested to be light in order to have good cooling at night. East and West wall are urged to (i) not having a windows to avoid soalr radiation at low altitude (ii) have a reflective surface, and (iii) resistive insulation (Szokolay 1980:334).
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External wall is also adviced to include time lag calculation to moderate internal temperature (Evans 1980:101). To have a quick response and low heat holding capacity then the width of the homogenous wall is < 75-100mm (Evans 1980:101). Table 1 . Wall thermal property guidelines for hot humid Element, climate and condition West wall East, south and north walls Walls shaded from direct solar radiation
‘ U’ value 2.0 2.0
3.0 4.0
Ti me lag 0-5 0-5
2.8
-
0-14
q/l
Procedure (a). East-wall model with U-value of 2.6 is constructed by Ecotect then shall be calculated using OTTV v.1 as Ecotect does not provide a glass box algorithm (Fig. 2). Following that, East-wall model with U-value of 1.6 would have same treatment (Fig. 4) (b). East-Wall with u-value 2.6 then becomes a calculation input towards OTTVi; its output is 21,28 W/m2 . (Fig 3). Similarly, u-value of 1.6 would produce OTTVi of 12,95 W/m2 . (Fig 6)
(Source: EVA NS 1980: 98)
Research Problem Table 1 shows that east wall, as subject of this paper, is required to u-value = 2.0; in practice, that value is difficult to provide due to the available material in the market (plaster-brick-plaster) tended to reach u-value=2.6 (Fig. 2). Furthermore, in relation with OTTVi, to have u-value outside the required value (2.0) needs also to investigate. It is therefore this research would like to investigate the effect of uvalue> 2 (e.g. 2.6) and u-value < 2 (e.g. 1.6) on OTTVi by using software OTTV ver.1, in particular u-value algorithm. Research Method Material and simulation tool Simulation model is an East-wall which is located at 7 southern latitude under solar exposure at 10 am, in March. (Fig. 1). East wall property shall be taken from library of Ecotect while the u-value and OTTVi shall be calculated using OTTV v. 1. Fig 1. East-Wall and climatic context
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Fig 2. East-Wall structure, U-Value= 2.6
Fig 4. East-Wal structurel, U-Value= 1.6
Fig 3. U-Value calc .= 2.6 for Partial OTTVi
Fig 6. U-Value calc .= 1.6 for Partial OTTVi
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RESULTS As it was explained, how much effect/increase which u-value may give to OTTVi in relation with its hot humid benchmark of 2.0 (Table 1) has not yet investigated. The total OTTV itself is expected to have value ≤ 45 W/m2 . Given 4 façade orientations (E, W, S, N) then on average each façade should have OTTVi ≤ 11.25 W/m2 . U-value of 1.6 and 2.6 structures are realistic for building market instead 2.0 (benchmark). For East wall case, simulation finds that u-value 1.6 produces 2 OTTVi o f 12.95 W/m while u-value 2.6 produces OTTVi of 21.28 W/m2 (Figure 7 and 8).
CONCLUSION By 1 difference in u-value, OTTVi difference for east wall may reach 8.33 W/m2 . Since u-value 2.0 is not available at the market while OTTVi is expected to have value OTTVi ≤ 11.25 W/m2 then to satisfy the latter it is suggested to use maximum u-value 1.6 ( OTTVi of 12.95 W/m2 ).
Fig 7. U-Value= 2.6 produces Partial OTTVi = 21.28 W/ m2 (Source: Winaktoe, 2008)
Fig 8. U-Value= 1.6 produces Partial OTTVi = 12.95 W/ m2 (Source: Winaktoe, 2008)
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REFERENCES
ANONIM (a), 1982, Architect’s Handbook of Energy Practice: Climate and Site, USA: The American Institute of Architects. ANONIM (b), 1982, Architect’s Handbook of Energy Practice: Economic Analysis, USA: The American Institute of Architects. ANONIM (c), 1982, Architect’s Handbook of Energy Practice: Energy Analysis, USA: The American Institute of Architects. ANONIM (d), 1982, Architect’s Handbook of Energy Practice: HVAC System, USA: The American Institute of Architects. ANONIM (e), 1982, Architect’s Handbook of Energy Practice: Simplified Energy Evaluation Technique, USA: The American Institute of Architects. ANONIM, 1992, Pedoman Tata Cara Perancangan Konservasi Energi pada Bangunan Gedung, Bandung: Departemen Pekerjaan Umum, Badan Penelitian dan Pengembangan PU, Pusat Penelitian dan Pengembangan Permukiman. ANONIM, 1993, SK SNI T-14-1993-03 tentang Tata Cara Perencanaan Teknis Konservasi Energi pada Bangunan Gedung, Bandung: Yayasan LPMB, Departemen Pekerjaan Umum. ANONIM, 1998, Keputusan Menteri Pekerjaan Umum Republik Indonesia, Nomor: 441/KPTS/1998 tentang Persyaratan Teknis Bangunan Gedung, Jakarta: Penerbit PU. ANONIM, 2000, SNI 03-6389-2000 tentang Konservasi Energi pada Bangunan Gedung, Jakarta: Badan Standardisasi Nasional. Martin EVANS, 1980, Housing, Climate, and Comfort, The Architectural Press Limited, London. Victor OLGYAY, 1963, Design with Climate, Princeton University Press, USA. Prasasto SATWIKO, Soesilo Budi LEKSONO, O.Th. KRISTIANTORO, 2000/2001, Proposal Collaborative Research Grant Program: Pengembangan Sistem Ventilasi Atap Tenaga Angin dan Surya (SIVATAS), Universitas Atmajaya, Yogyakarta. S.V. SZOKOLAY, 1980, Environmental Science Handbook for Architects and Builders, The Construction Press Ltd., England. Wied Wiwoho WINAKTOE, 2008, Laporan Akhir Penelitian Reguler: Model Komputasional Overall Thermal Trasmittance Value (OTTV), Surakarta: Lembaga Penelitian dan Pengabdian Masyarakat, UMS.
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