The 3for2 Concept: Efficient Office Building Design 1

Wednesday, March 25th, 2015
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The ‘3 for 2 Concept’ allows the construction of three floors within the standard space of two floors, without any impact on perceived floor-to-ceiling heights, which researchers say could reduce energy consumption in offices by 40 per cent.

The efficiency is achieved through the use of new construction techniques and efficient integration of new technologies such as LED lighting panels, passively cooled ceiling tiles and high-performance chillers.

The methodology, devised by the Future Cities Laboratory (FCL) of the Singapore-ETH Centre (SEC), a joint Swiss-Singaporean research centre, is being implemented as a one-floor test case at the United World College South East Asia (UWCSEA), the world’s largest international school, in partnership with Siemens Building Technologies.

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Although the energy efficient office concept is currently being tested for the Singapore market, it is applicable to much of the world.

“Generally speaking, in regions that do not face particular height restrictions, there appears to be a general norm for ceiling heights in modern non-domestic buildings,” said Dr Adam Rysanek, 3for2 project manager, Low Exergy Research Group.

“From Singapore to China to North America, floor-to-ceiling heights seem to fall closely in the range of 2.7 metres, with floor-to-floor/slab-to-slab heights around 3.9 to four metres. There are regions with notable building height restrictions, such as Washington D.C., which fall away from this norm. However, in our discussions with developers, we have worked with what seems to be an accepted benchmark for modern high-rise buildings outside of Europe. “

For modern offices in Singapore, up to 25 per cent of vertical spaces are occupied by ductwork, structures and other technical systems that provide the services occupants need. Furthermore, roughly 60 per cent of electricity consumption is attributed to air-conditioning alone.

Large floor-to-floor heights increase the volume of space to be enclosed and conditioned, and also add to material cost, higher structural loads and increased solar and transmission gains from additional façade surface. The standard air-based, packaged cooling systems in current use are typically oversized and over-cool the supply air in order to manage humidity levels, resulting in uncomfortable spaces with unnecessarily high energy demand.

Through systems integration, the researchers propose to build three floors in the space of two by eliminating the excesses of standard design. At the same time, they aim to improve performance by implementing LowEx technology, which allows a switch from air-based to water-based systems that drastically reduce the space in a building dedicated to energy transport.

“Air-based” and “water-based” systems refer primarily to the medium by which space heating and cooling energy is transported to individual rooms in a building.

Radiators, used commonly for heating in Europe, are an example of “water-based” systems. In a typical installation, hot water is transported directly to radiators in rooms through a centralized hot water piping network.

Most air-conditioning systems in commercial buildings rely on the movement of cold/heated air through a centralized network of air ducts – hence they are air-based.

“A key advantage of ‘water-based’ over ‘air-based’ systems is that it requires considerably less energy to transport water throughout a building compared to air. They also require considerably less building volume,” said Rysanek. “One ‘con’ of water systems is that they are unable to directly control indoor humidity levels.”

A critical feature of air-based systems is that they provide controlled ventilation of individual rooms – they can forcefully replace stagnant indoor air with conditioned air as-and-when needed. Moisture can also be forcefully added to or removed from the circulating air stream through a mix of cooling coils, heating cools, and humidifiers.

Water-only systems such as the typical European context of radiator heating do not directly affect the moisture content of their surrounding air. Thus, buildings with water-based systems only must typically rely on natural ventilation through facades for rudimentary control of humidity.

In the UK, where air-based systems are uncommon in the domestic sector, damp conditions and mould growth can become an issue in poorly conditioned homes. This is in part attributed to the lack of ability for heating systems in these households to directly control indoor humidity levels.

The 3for2 concept proposes a decoupling of a conventional air-based air conditioning system into a decentralized network of water-based and air-based systems. This decoupling lends itself to a ‘thin’ system, with the pipework and ductwork of the decentralized concept requiring significantly less building volume than its conventional counterpart.

This is the heart of the 3for2 system; by minimizing the volume requirements for air conditioning distribution networks, the possibility arises to integrate both pipework and ductwork into a building’s structure, such as its floor slabs and facades. By using decentralized ventilation systems, this space requirement is further reduced.

At the same time, LowEx technology for space cooling increases system performance since chilled water supply temperatures can be increased. The technology consists of passive chilled beams, distributed ventilation units combined with an underfloor air distribution network and new control systems.

“Most of the ‘LowEx’ technologies in the 3for2 system are not inherently expensive,” explained Rysanek. “The type of system we are installing in Singapore today uses technologies that have been commercially viable in Europe, Australia, and elsewhere for some time.”

Rysanek cited the example of the 30 The Bond building in Sydney, which 10 years ago came to house Australia’s largest installation of passive chilled beams with the building purporting to reduce greenhouse gas emissions by 30 per cent against traditional buildings of its time.

“The supply chain also exists to provide these technologies globally, hence we do not see the provision of these technologies in Singapore as inherently expensive. What is costly, however, is the adaptation of these technologies into regions that have less experience with them – and thus less trained practitioners to understand, install, and commission them,” he added.

One thing Rysanek is keen to clarify is that the aim is not to tout 3for2 as a proven solution but to objectively evaluate it.

“Our future research agenda will be based heavily around data-based monitoring of our installed system, and publishing our performance data and findings publicly,” he said. “Whilst our simulation models have shown that our system, on the whole, may be more than 20 per cent more efficient than the current ‘best’ building energy benchmark for Singapore, we still need to test and prove/disprove this ourselves.”

As part of this, the team has created a living laboratory with the 3for2 concept implemented across a 600 square metre single floor section within a new 20,000 square metre building under construction by the UWCSEA.

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Click to enlarge

“Though our project covers only three per cent of the building’s floor space, this is more than enough,” said Rysanek. “Before we can really consider applying our concept throughout a 50-storey skyscraper, we need to make sure we get the basics right.”

Within the 600 square metre office space, a board room will be equipped with both the 3for2 aircon system as well as the standard aircon system that will serve the rest of the building. This will eventually allow the team to make a rare, like-for-like empirical comparison of the system on both the subject of performance and life cycle costs.

The construction phase of the living laboratory is well underway with installation and commissioning of the system to occur between May and October 2015 with doors open before the end of the year.

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  1. Glan Blake Thomas

    I think this challenge is admirable but I cant quite make the maths add up.

    with a 2.7 m headroom floor to ceiling, stacking 3 spaces will require 8.1m

    if 2 normal floors of 3.9m slab to slab are to be replaced they take up 7.8 so there is a shortfall before any structural thickness and services of any kind are added unless you change the floor to ceiling height as well, but then it is not really a true comparison.

    I totally agree that reducing height must be the challenge for the human race in creating the most sustainable buildings but most engineers will take argument with services that cant be accessed for maintenance and architects will take argument with design freedom, acoustic privacy and so on. As soon as you put cellular office space into the structure you will need horizontal distribution of services,drains etc as the article points out.

    I may be missing something here and would like to learn more but as a services engineer having worked in this area for many years I think the line would be more believable with saving 10% or getting 1 more floor within the height of 10 old floors. I await more details. Well done for starting the debate.