OTTV in UBBL · 2017-01-03 · MGBC NORTHERN CHAPTER ROADSHOW 2016 Baylon Tham 26112016 OTTV in UBBL MS1525:2007 CODE OF PRACTICE ON ENERGY EFFICIENCY AND USE OF RENEWABLE ENERGY

MGBC NORTHERN CHAPTER ROADSHOW 2016Baylon Tham 26112016

content

(i) OTTV in UBBL

(ii) what’s OTTV

(iii) ways to improve OTTV

(iv) case study: KOMTAR


OTTV in UBBL

MS1525:2007CODE OF PRACTICE ON ENERGY EFFICIENCY AND USE OF RENEWABLE ENERGY FOR NON-RESIDENTIAL BUILDINGS (FIRST REVISION)[Department of Standards Malaysia]

Clause 5.2The OTTV of the building envelope for a building, having a total air-conditioned area exceeding 4000m2 and above should not exceed 50 W/m2 and should meet the requirement specified in Clause 5.4.2.

OTTV < 50W/m2

Clause 5.4.2In order to take advantages of daylighting, the visible transmittance of the daylight fenestration system should not be less than 50%.


OTTV in UBBL

April 2016, MBPP announced to adopt new UBBL incorporate with OTTVrequirement and calculation for building plan submission.


what’s OTTV

OTTV vs Building Envelope

Building Envelope-The exterior portions of a building through which thermal energy is transfer.[Note: This thermal transfer is the major factor affecting interior comfort level and the air-conditioning load.]- The building envelope has to block out heat gain into buildings via conduction and solar radiation.

Overall Thermal Transfer Value (OTTV)-The design parameter that indicates the solar thermal load transmitted through the building envelope excluding the roof.[The OTTV aims at achieving the design of building envelope to cut down external heat gain and hence reduce the cooling load of the air-conditioning system.]


what’s OTTV

Climate & Building Envelope


what’s OTTV


Building Envelope to suit local climate


what’s OTTV


Building Envelope to suit local climate


what’s OTTV

concept of OTTV

AssumptionThe concept of OTTV is based on the assumption that the envelope of the building is completely enclosed.

In the OTTV formulation, the following items are not considered:1. Internal shading devices eg. curtains2. Solar reflection or shading from adjacent buildings3. Green walls


what’s OTTV

concept of OTTV

MS1525:2007 Clause 5.2.2 says

The formula for the OTTV of any given wall orientation is as follows:

OTTVi = 15α (1- WWR) Uw + 6 (WWR) Uf + (194 x CF x WWR x SC)

OTTV = + + HeatConductionthrough Walls

HeatConductionthrough Windows

Solar Heat Gainthrough Windows

0.2% to 5% 10% to 20% 70% to 85%


what’s OTTV

concept of OTTVOTTVi = 15α (1- WWR) Uw + 6 (WWR) Uf + (194 x CF x WWR x SC)




0.2% to 5%15α (1- WWR)

α = Solar Absorption = colour of wallsWWR = Window-to-Wall RatioUw = U-value of Wall


what’s OTTV

concept of OTTVHeat Conduction through Walls


black 0.99bare concrete 0.65

white semi-gloss paint 0.25

Solar Absorption


what’s OTTV



Window-to-Wall Ratio

> 50%± 50%

< 50%


what’s OTTV



Wall U-value

Aluminium Composite Cladding with Insulation, U-value = 0.92 W/m2k

Plastered Brickwall,U-value = 2.87 W/m2k


what’s OTTV





10% to 20%6 (WWR) Uf

WWR = Window-to-Wall RatioUf = U-value of Windows


what’s OTTV

concept of OTTVHeat Conduction through WindowsWWR = Window-to-Wall RatioUf = U-value of Windows


< 50%± 50%

> 50%


what’s OTTV

concept of OTTVHeat Conduction through WindowsWWR = Window-to-Wall RatioUf = U-value of Windows

Window U-value

Single glazed clear,5.7 to 6.2

Laminated tinted,4.5 to 5.5

Double glazed clear,2.6 to 2.9


what’s OTTV





70% to 85%194 x CF x WWR x SC

CF = Correction FactorWWR = Window-to-Wall RatioSC = Shading Coefficient


what’s OTTV

concept of OTTVSolar Heat Gain through WindowsCF = Correction FactorWWR = Window-to-Wall RatioSC = Shading Coefficient

Orientation CF

North 0.90North-East 1.09

East 1.23South-East 1.13

South 0.92South-West 0.90

West 0.94North-West 0.90

Solar Correction FactorsNote: Data collected indicates that the average vertical East surface solar radiation is significantly higher than the vertical West surface. This trend is seen to be caused by the normally clear sky in the morning and cloudy sky in the afternoon.


what’s OTTV



< 50%± 50%

> 50%


what’s OTTV


SC – major contributor to reduce OTTVSC = SC1 X SC2

SC1 is shading coefficient of glazingGlass Shading Coefficient is the amount of solar energy that passes through the glass, relative to a 3mm clear glass tested under similar conditions. Eg. A glazing with a SC of 0.45 would allow only 45% as much solar energy to pass through as would a 3mm clear glass.

SC2 is shading coefficient of external shading device (can be in the form of horizontal and/or vertical shading devices that help to reduce solar heat gain through the windows)


what’s OTTV

concept of OTTVSolar Heat Gain through Windows

Shading Coefficient of Glazing


what’s OTTV


Shading Coefficient of external shading device - Horizontal


what’s OTTV


Shading Coefficient of external shading device


what’s OTTV


Shading Coefficient of external shading device - Horizontal


what’s OTTV


Shading Coefficient of external shading device - Vertical


what’s OTTV


Shading Coefficient of external shading device – Egg Crate


ways to improve OTTV

Ways to improve OTTV

2. Review Solar Correction Factor (CF) in Table 4.

3. Review glass selection and its Shading Coefficient (SC1).

4. Review sunshades and its Shading Coefficient (SC2) in Table 5, 6 and 7.

5. Review WWR.

1. Identify which component contribute the most to OTTV.


ways to improve OTTV

Review sunshades and its Shading Coefficient (SC2) in Table 5, 6 & 7.


case study: KOMTAR

KOMTAR


case study: KOMTAR

KOMTARAssumption12 sides are almost circular and wall-to-window area are almost equally divided in each octagonal sector (8 sectors).

Wall Area (per sector)Perimeter length = 19.50mFloor to floor height = 3.05mWall Area: 19.50 x 3.05 = 59.48m2

Window Area (per sector)Perimeter Window Length: (8.5+0.7+0.7) = 9.90mWindow Height: = 2.40mWindow Area: 9.90 x 2.40 = 23.76m2

Total area for OTTV calculation:Tower (level 11 - 60) = 50 floorsTotal Wall Area (per sector): 59.48 x 50 = 2,974.0m2Total Window Area (per sector): 23.76 x 50 = 1,188.0m2


case study: KOMTAR

KOMTAR


case study: KOMTAR


case study: KOMTAR


case study: KOMTAR


case study: KOMTAR


case study: KOMTAR


case study: KOMTAR


case study: KOMTAROTTV 65.30 OTTV 51.51

OTTV 43.96 OTTV 46.09

OTTV 42.74 OTTV 45.2


case study: KOMTAR


thank youbaylon tham

www.mgbc.org.mywww.greenbuildingindex.org

Documents

OTTV in UBBL · 2017-01-03 · MGBC NORTHERN CHAPTER ROADSHOW 2016 Baylon Tham 26112016 OTTV in UBBL MS1525:2007 CODE OF PRACTICE ON ENERGY EFFICIENCY AND USE OF RENEWABLE ENERGY