ANSWERS FROM BCA

1

a)         Is BCA considering to revise the outdoor visible light reflectance from 10% to say 12% to 15%? Recently, I received a request for sc value of 0.36 for a new factory. There isn't any 6mm monolithic coated glass with sc value of 0.36 that also meets the 10% reflectivity requirement. To use thicker glass of say 8mm would increase cost.

b)         Will the limit on reflectivity of 10% for glass windows be revised to facilitate design flexibility? The reflectance of double glazed clear glass is already 13%.

Ans:

In connection with enhancing ETTV, BCA is also reviewing the limit on reflectivity of 10% for window glass. The revised reflectivity limit will be implemented together with the new ETTV standard.

2

a)         To speed up the energy efficiency programme, is BCA approaching IRAS for further tax benefits over and above existing benefits provided by IRAS?

b)         What are the incentives available for building owners to go for energy efficient buildings? The savings in cost seems not immediate and upfront for owners/developers to the make the early commitment.

Ans:

The accelerated depreciation allowance scheme encourages building owners to replace old and less energy efficient equipment with more energy efficient machines. It also encourages the use of energy saving equipment such as computerised energy management system. The scheme is administered by the Ministry of the Environment. A committee is currently reviewing the list of energy saving devices with a view to expanding it.

3

Will the new requirement of 35 W/m² for OTTV be applicable to all types of buildings?

Ans:

The new requirement on 35 W/m² will be applicable to all air-conditioned buildings.

4

Is it better to control the ETTV for each building facade rather than considering the overall average as some facade may have extremely high ETTV?

Ans:

Averaging the ETTV of all the facades will allow designers greater flexibility in designing the buildings. If ETTV standard is applied to each façade, it will have significant impact on the design of east/west-facing walls, which have much higher Solar Factor.

5

When and how will the trial implementation of the enhanced standards be carried out and for how long?

Ans:

During the trial implementation period, which is from now till the new ETTV is legislated, new building projects will be identified by BCA and encouraged to comply with the new standards.

BCA plans to implement the enhanced standards early next year.

6

Is the requirement for buildings to comply with the OTTV standard still based on the cooling capacity of each equipment not exceeding 30kW?

Ans:

The relaxation will continue for the time being for small air-conditioned buildings which require air-conditioning system with cooling capacity of less than 30kW. Large air-conditioned buildings are required to comply with the ETTV standard regardless of the cooling capacity of individual air-conditioning equipment.

7

Can BCA consider relaxing the ETTV for shopping centre or mixed development? For good visibility shop front requires large expanse of clear glass which inevitably will not comply with ETTV requirement. There is a conflict between energy savings and visibility for shopping centre.

Ans:

For shop fronts with window display showcase, BCA allows the air space and the construction materials used for the construction of the showcase to be included in calculating ETTV. Hence, there is no necessity to relax the ETTV.

8

With ETTV and RTTV in place, is the maximum thermal transmittance calculation for roof of air-conditioned building still required?

Ans:

The RTTV requirement only applies to roof with skylight whereas the maximum thermal transmittance or U-value requirement only applies to roof without skylight. Hence, they are mutually exclusive.

9

With regard to CP 24 on the minimum energy efficiency standard, only the lighting power budget is implemented. Why not air-conditioning equipment also?

Ans:

At the moment only the lighting power budget is implemented. BCA plans to implement the COP standard for air-conditioning equipment together with the energy analysis method when the new standards are legislated.

ANSWERS FROM PROF S K CHOU

10

How can BEST be used for other building types such as factories, hospitals and libraries?

Ans:

BEST will use one of the 3 available generic building types; namely, hotel, retail or office that matches the operating hours of the building type in question for simulation. For example, if a library's air-conditioning equipment and lightings are operated from 9am to 6pm daily, then the office building type will be used to simulate the energy consumption of the library.

11

Is there a limit on the space input under the lighting form and receptacle form?

Ans:

There is no limit on the space input for both forms.

12

Why is there a difference on the space category between the lighting form and receptacle form?

Ans:

This is due to the difference in space categories for both lighting and receptacle power allowances that is reflected in the ASHRAE standards, which are referred to in BEST.

13

Numerals are used to identify the spaces. Can the spaces be identified according to their types of usage such as classrooms, stores etc.?

Ans:

The spaces are identified based on the space category that the end user chooses.

14

If the ETTV & RTTV comply with the prescriptive standards but lighting allowance & receptacle power density do not, has the building design complied with the energy performance standard?

Ans:

As long as the annual total energy consumption of the design building is less than or equal to that of the prototype building, the design building is deemed to have complied with energy performance standards even if there is non-compliance with any of the prescriptive standards.

15

Which algorithm is BEST based on or was it derived from 1^st principle like DOE?

Ans:

BEST is based on a cooling degree-day method, correlated with key parameters such as ETTV and part-load performance. The formulation and validation of this formula can be found in the International Journal of Energy Research, Vol 17 Pg 759-773, " Development of an Energy Estimating Equation for Large Commercial Buildings". Validation on simulation results is done using the DOE-2 code.

16

Has BEST been proven to be accurate? Has it been used to predict the consumption of an existing building i.e. is it accurate in predicting consumption levels or is it a design tool for gauging impact of certain measures such as choice of glass or operation hours?

Ans:

A comparison study was conducted for the simulation results obtained from BEST and DOE-2.1E. It was found that the annual cooling energy and total energy consumption differs by about 2-4%. To date, BEST has not been used to predict the consumption of any existing building. However, DOE-2 has been well validated.

17

In BEST, why are the prescribed values of ETTV and RTTV 70 W/m² and 62 W/m² respectively instead of 65 W/m²?

Ans:

These values will be updated to the revised standards once BCA conducts the trial implementation and subsequent legislature of the revised standards.

18

In the daylighting form, how are the transmittance values obtained?

Ans:

BEST runs an external program, TASK, from the Utilities submenu which can be used to calculate the values. Correspondingly, there is a data grid table in the daylighting form that provides such information on the various glass types.

19

The difference between OTTV and ETTV seems to be the replacement of weather dependent constants. These "constants" were derived since 1985. How are these "constants" relevant after 15 years?

Ans:

The constants for the ETTV formula were determined through vigorous computer simulations performed in NUS through the late 1990s using local annual weather data, and should remain relevant to the current environment.

20

What is the basic difference between OTTV and ETTV? Why not retain OTTV and change the requirement to 35 W/m²?

Ans:

The basic difference between OTTV and ETTV is the relative contributions of the three components of heat gain through the building envelope. The ETTV expression provides a truer annual value of heat transmission and therefore lends itself readily to energy calculations. The ETTV value has a direct link to heat gain through the envelope and provides and better feel of the measures implemented to reduce heat gain.

21

Can the unit for design outdoor air in cfm/person be converted to litres/s/m²?

Ans:

The conversion will be available in the updated version of BEST.

ANSWERS FROM PROF RAYMOND WONG

22

How many buildings have you audited and how is the reaction from the owners?

Ans:

About fifteen and mostly done as part of the ASEAN-US research project. The reaction from the owner is mostly positive as they are able to know how their building performs in terms of energy use.

23

How should the energy used by decorative lights be controlled?

Ans:

Clause 6.3 in CP 24:1999 recommends the lighting budget for floodlighting building exterior and also exterior spaces. Clause 6.4 recommends their mode of control to turn off exterior lighting during hours when such lighting is not necessary.

Energy monitoring in a building audit can be used to identify how energy is consumed. For example, in an audit of a commercial building the external decorative lighting was logged to have contributed to a significant amount of energy throughout the night. By switching off the lights after midnight some energy can be saved.

ANSWERS FROM PROF S E LEE

24

Are the data on the study of energy efficiency of office buildings in Singapore available on the website?

Ans:

Yes, the processed data of the 104 buildings studied have been posted on the website. They are presented as a series of cumulative percentile curves for total building energy consumption efficiency, landlord energy consumption efficiency and tenants’ energy consumption efficiency. In the latter case, only a few groups of tenants have been studied. The raw data are however not available. Some data about the study have been given in the paper presented at the BCA seminar. This is now available on the website.

25

A quality design building which considers other factors such as environment and aesthetics is also energy efficient building. But the converse is not necessarily true. Instead of energy efficient building we should therefore promote quality design.

Ans:

Agree! A quality design building may be an energy efficient building. It is also true that an energy efficient building may not be a quality building with good aesthetics. The BCA and various professional institutions, including the owners should promote quality building-design. For this, we first must know how to measure quality of buildings and classify them accordingly. It requires a holistic and balanced evaluation system taking into consideration the fundamental performing needs of a building. A hierarchy of performance mandates must be established. For example, it must start from physiological needs, then psychological needs, then social needs, and finally the self-actualization of the building or its owners. Frequently, basic needs are compromised to make way for other superficial beauty or other needs of a building for marketing reasons. For example, vast investment may be made on marble and granite in or on a building, at the expense of a quality air-conditioning system. What is more important? Good air for healthy and productive work environment or marble and granite to put up a front. Hence, the paper has emphasized the correct approach towards energy efficiency in buildings, and that is healthy, performing and energy efficient building with good environment. This clearly shows that the quest towards quality buildings must involve the professionals, the developers, and most of all the users.

26

One of the major steps taken in the US to encourage energy efficiency in buildings and industries is through performance contracting. Can you please comment why this approach has not been successful so far? Will we be reactivating this?

Ans:

First, I must clarify that performance contracting is only a business arrangement and strategy. It may or may not result in quality energy efficient building. It is however a strategy adopted by the US and Canadian Governments at one stage to promote the profession and business of Building Energy Services Companies (BESCO). The success, as I am aware, is largely due to their Governments’ policy to encourage the upgrading of public sector buildings to become energy efficient buildings. It is hoped that in doing so it will generate a significant market for the BESCOs, and that through the lessons learnt, best practices in energy efficiency will evolve and gradually be absorbed by the industry as a whole as standard practice. This of course enhances the professionalism of the BESCOs and sharpens them for foreign markets. Whether Performance Contracting will be reactivated in Singapore is not for us to decide, I think it will when the market environment is right.