UBBL Clause 38A

PAM Northern Chapter Seminar

OTTV, Roof U-Value

& Proposed Implementation Procedures

Ar Von Kok Leong

11 Feb 2017

UBBL Clause 38A

Proposed Implementation Procedures

UBBL Clause 38A Amendment 2012

Energy efficiency in buildings (1) New or renovated non-residential buildings with air-conditioned space exceeding 4,000 square metres shall be – a)designed to meet the requirements of MS 1525 with regards to the Overall Thermal Transfer Value (OTTV) and the Roof Thermal Transfer Value (RTTV); and b) provided with an Energy Management System.

UBBL Clause 38A

Amendment 2012 Energy efficiency in buildings

“non-residential” includes industrial, institutional, commercial, retail “air-conditioned” means buildings with centralised aircond system “exceeding 4,000 sm” excludes shophouses or small non-residential buildings even though centralised aircond is employed.

UBBL Clause 38A Amendment 2012

Energy efficiency in buildings

(2) The roof for all buildings (residential and non residential) shall not have a thermal transmittance (U-value) greater than– a)0.4 W/m2K for Light (under 50 kg/m2) weight roof; b)0.6 W/m2K for Heavy (above 50 kg/m2) weight roof, unless provided with other shading or cooling means.

UBBL Clause 38A

At Building Plan submission stage (1) For non-residential building where the air-cond space exceeds 4,000 m2; - the PSP shall endorse and submit OTTV & RTTV calculations conforming to the latest version of MS 1525 (the 2007 and 2014 revisions stated the OTTV and RTTV shall not exceed 50 W/m2 and 25 W/m2 respectively). The submitted calculations shall incorporate the following documents :-

Implementation Procedures

UBBL Clause 38A

a) Plans and elevations, marking out walls & apertures used for the calculation in blue colour; and walls & apertures not used for calculation in red. Recommended scale is 1:200;

b) OTTV calculations for each facing wall/façade; c) Description of wall & aperture materials specified; d) Calculation of U-values for walls; e) Glazing specifications on Shading Coefficient and U-

values; f) Confirm provision of Energy Management System.

Implementation Procedures

UBBL Clause 38A

(2) For all residential and non-residential buildings; the PSP shall endorse and submit the Roof U-value calculations incorporating the following documents; a) Plans and elevations of the roof used for the

calculation marked in blue b) Description of roof materials specified c) Calculation of Roof U-value for all roof types d) Description and calculations of alternative means

of compliance.

Implementation Procedures

UBBL Clause 38A

• The submitted plans and calculations endorsed by the PSP shall be deposited with the Local Authority (LA) for record. Self regulatory

• This arrangement is similar to the submission of building structural engineering calculations by the Submitting Person which is kept by the LA for record.

• Such deposited plans and calculations will only be retrieved for checking in the event of complaints received. Not part of approved endorsed BP drwgs

• The LA may carry out random check of these documents and calculations.

Implementation Procedures

UBBL Clause 38A

Roof U-Value

UBBL Clause 38A

The calculation of OTTV does not include the roof plane, but the thermal transmittance (Roof U-value) of the roof construction is important.

Roof U-Value MS1525 Clause 5.5

U-values are worked out from the Thermal Resistance of the respective materials making up the Roof, similar to that for Walls.

ie, U = 1 / Rtotal The higher the R, the lower the U, the better.

UBBL Clause 38A

0.6 Heavy

(Above 50 kg/m²)

0.4 Light

(Under 50 kg/m²)

Maximum U-Value (W/m²K) Roof Weight Group

Roof U-Value MS1525 Clause 5.5.1

UBBL Clause 38A

R.C. Roof without insulation

Roof U-Value

UBBL Clause 38A

R.C. Roof with insulation

Roof U-Value

UBBL Clause 38A

Metal Deck Roof without insulation

Roof U-Value

UBBL Clause 38A

Metal Deck Roof with insulation

Roof U-Value

UBBL Clause 38A

Roof type “A”

“B”

“Pool”

“D”

“C”

Multiple Roof Types : Worst case applies

Plan View

Roof U-Value

UBBL Clause 38A

Roof type “A”

“B”

“Pool”

“D”

“C”

Secondary Roof

Plan View

Roof U-Value

Secondary Roof Over

UBBL Clause 38A

Roof U-value applies here

Roof U-Value Secondary Roofs

Habitable space, Res, Non-Res, AC, Non-AC

Section

Habitable or non-habitable space Primary Roof

UBBL Clause 38A

Coverage of Secondary Roof?

y?

Primary Roof

Habitable space, Res, Non-Res, AC, Non-AC

Roof U-value applies here

Roof U-Value Secondary Roofs

SRI (UHI)

Ventilation ? Habitable or non-habitable space

Section

Secondary Roof

UBBL Clause 38A

Q1 : Ventilation ? Can be natural or forced. Rate of ventilation (ACH) is important

Q2 : Height of secondary roof ? Affects ACH

Q3 : Coverage of secondary roof ? Uncovered Primary Roof requires insulation

Q4 : SRI ?

Roof U-Value Secondary Roofs

UBBL Clause 38A

0

1

2

3

4

5

6

7

0 1 2 3 4 5

ConcreteMetal Deck

Air space, (m)

Air Changes per Hour (ACH)

Secondary Roofs

Uninsulated Secondary Roof type :

UBBL Clause 38A

Horizontal pergolas or vertical screens

Roof U-Value Secondary Roofs

UBBL Clause 38A Roof U-Value

Secondary Roofs

UBBL Clause 38A

Difference in concept between Roof U-value and UHI

Roof U-value measures heat conducted through the composite Primary Roof construction

AND Applies where habitable or living spaces are found directly below it. Habitable spaces below Primary Roof need not be fully enclosed or

aircond, and includes outdoor dining etc

UHI is about reflecting away solar radiation to achieve a cooler micro-climate.

Once heat comes in, it takes a lot of energy to get it out, regardless whether the spaces below are occupied or not.

UBBL Clause 38A

Difference in concept between Roof U-value and UHI

Can secondary roofs eg horizontal pergolas or screens be used to calculate as part of the Primary Roof’s composite Roof U-value?

No, because they are not part of the composite roof

construction.

But they can be used to be a part of the calculation to reduce UHI

UBBL Clause 38A

Can PV be used in calculating Roof U-value? Similar to pergolas.

It will count only if it is BIPV, ie it forms part of the roof construction.

What is the SRI of PV surfaces?

SRI is about 40%

New technologies create PV with less SRI.

UBBL Clause 38A

Can insulation below rc slab be a part of Roof U-value? No, because the heat is already in contact with the

structure, and it will conduct to other parts of the building. Hence, insulation is better to be placed above the structure.

But in renovation works, where the original roof is not replaced, insulation below rc slab in ceiling space can be

considered.

Can mechanical plant, equipment or water tanks be calculated as a part of Roof U-value?

For plantrooms exposed to the sky, Roof U-values are calculated on the Primary Roof construction, and therefore

objects such as mechanical plant, etc do not count.

UBBL Clause 38A

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250 300 350

Insulation to lightweight roof

ROO

F U

-VAL

UE

(W/m

2K)

INSULATION THICKNESS (mm)

MS 1525 lightweight roof < 0.4 W/m2K

Roof U-Value

UBBL Clause 38A

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250 300 350

INSULATION THICKNESS (mm)

ROO

F U

-VAL

UE

(W/m

2K)

MS 1525 heavyweight roof < 0.6 W/m2K

Insulation to heavyweight roof Roof U-Value

UBBL Clause 38A

Clause 5.6.1 The concept of RTTV applies if the roof is provided

with skylight, and the entire enclosure below is fully air-conditioned.

Clause 5.6.2

The maximum recommended RTTV is 25 W/m2.

RTTV MS1525:2007 Clause 5.6

UBBL Clause 38A

Clause 5.2 OTTV applies to building envelope, where OTTV < 50 W/m2

Clause 5.5 Roof U-value refers to the thermal transmittance of the roof, where Roof U-value < 0.4 - 0.6 W/m2K

Clause 5.6 RTTV applies to roof with skylights, where RTTV < 25 W/m2

UBBL Clause 38A

Thank you