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SUSTAINABLE UPGRADE FOR COMMERCIAL BUILDINGS

There are many commercial buildings that can benefit from an upgrade using sustainable principals.

 

There are many options to upgrade to an existing commercial building without having to demolish and redevelop to achieve an acceptable return. The main advantage of course is the saving in capital expenditure and lower risk resulting from a lesser spend.

 

Providing a refurbishment upgrade to an existing building can result in a new lease of life for many years to come and result in a building that is much easier to let as well as save on running cost through lower energy use. The design aesthetic can be up with the most creative and modern trends that are proving to be most popular in the market place today.

 

Looking at the big picture, designing, constructing and refurbishing for efficient buildings today will avoid locking in emissions and energy intensive assets for many decades. Importantly, scaling up efforts to improve energy performance will build industry experience, helping to reduce costs.

 

Energy in Buildings: Best Practice Initiatives can help property owners or managers reduce energy costs and cut emissions for their buildings.

 

In the office sector, best practice projects are readily able to achieve a 5.5 star NABERS Energy rating. There are buildings that have already achieved a 6 star NABERS Energy rating without any Green Power contribution.

 

It’s also important to recognise that buildings designed now, for completion in two or three years, will enter a market where they will be competing with an increasing volume of higher performance building stock. Some projects are even pursuing a target of ‘Net Zero Energy’ – whereby any energy drawn from the grid is offset in full by clean energy generated on site and exported to the grid over the course of a year.

 

In the past five years LED lighting and EC (electronically commutated) fans have leapt from the fringe to standard practice in many buildings. Solar photovoltaic systems have also reached a tipping point, with the number of large scale installations planned increasing rapidly over the past 12 months.

 

The following key points will offer opportunities to upgrade your commercial building and achieve beneficial results for everyone.

 

Architectural Built Form

Reduces heating , cooling, lighting and ventilation energy use ‘Passive design’ aims to exclude direct sun during hot weather, admit direct sun during cold weather, optimise natural daylight, control glare – and in naturally ventilated buildings, maximise access to breezes. A rectangular building footprint stretched from east to west helps minimise direct sun from angles where it is difficult to control. Optimising the size of external windows is important – for curtain walls a raised sill is helpful. A narrow floor plate is desirable, atria can be included, and often a central core is preferable. Incorporating prominent stairs can also help by reducing lift energy use.

 

Colour & Reflectivity of External Materials

Reduces cooling energy use.

 

When high reflectance (high ‘albedo’) materials are used on the exterior of a building – in particular the roof – it decreases the amount of heat that is absorbed from direct sun, reducing air conditioning energy. It also helps keep the local air temperature around the building cooler, which can reduce air conditioning energy. Materials that are very light in colour are ideal, but colour is not the only factor – the chemistry of coatings can be altered too. Specialised paints can be used to increase the reflectance of existing buildings. Low-rise buildings with large roof areas are ideal candidates.

 

External Shading

Reduces cooling energy use.

 

External shading is used to exclude direct sun before it reaches a building’s windows and control glare. Horizontal ‘fins’ are the best type of ‘fixed’ (non-movable) shading. for facades facing North (and South, for northern locations); vertical fins are best for East and West. ‘Operable’ (movable) shading can be used to admit direct sun when it’s needed, exclude it when it’s not, and improve natural daylight – but also takes longer to pay back. Shading structures must incorporate a ‘thermal break’ to avoid decreased insulative performance. Vegetation can be used as shading, with deciduous plants being very effective in temperate climates.

 

Enhanced Daylighting

Reduces lighting energy use

 

Green Roofs & Green Walls

Reduces cooling energy use

 

Green roofs and walls provide enhanced thermal mass and isolation performance, and help keep the local air temperature around the building cooler – reducing air conditioning energy. They also provide acoustic and stormwater quality benefits. ‘Intensive’ green roofs have deeper soil, larger plants and can be used as rooftop gardens – but are also very heavy. ‘Extensive’ green roofs have shallow soil, ground covering plants, and are lighter. A wire trellis with creepers can provide excellent shade, but a true ‘green wall’ has a dense population of plants growing out of a vertical medium with an automatic watering system.

 

Internal Thermal Mass

Reduces heating and cooling energy use.

 

Thermal mass – provided by high density materials like concrete, brick and ‘phase change’ materials – helps to smooth out changes in indoor temperature without using. energy. In winter, it can absorb heat from direct sun which is released back overnight. In summer, heat which accumulates in the thermal mass can be cooled down using ‘night purge’ ventilation. Thermal mass is most effective when it’s located inside of insulation, and when it’s not covered up by internal finishes – examples include ‘reverse brick veneer’, insulation under polished concrete floors, and insulating around the edge of each floor slab.

 

Air Tightness

Reduces heating and cooling energy use.

 

When the wind (or a ventilation system) causes a pressure difference between inside and outside, air tries to move from one to the other – increasing heating and air conditioning energy. ‘Blower door testing’ is used to measure how air tight a building is, and can be a useful diagnostic tool. Revolving doors perform much better than sliding doors – and where secondary swing doors are required they should be on push-button release to discourage their use. Taped ‘weather-tightness membranes’ can be used instead of conventional building wrap – and very high performance buildings can also use internal ‘air-tightness membranes’.

 

Enhanced Insulation & Thermal Breaks

Reduces heating and cooling energy use.

 

The thermal resistance of insulation (measured as ‘R-value’, where higher is better) and its continuity as it wraps around a building help to minimise heat transfer – as does the avoidance of ‘thermal bridges’ (localised points in steel or concrete structures where heat transfers more easily). Exceeding the minimums in the National Construction Code is often worthwhile. Rigid insulation can be installed outside of the structure – for example ‘insulated sandwich panel’ for roofs, or ‘insulated sheathing’ for walls. Structural ‘thermal break’ products can help where a structural element penetrates through the line of insulation.

 

Glazed Facades – Solar Control

Reduces cooling energy use.

 

The solar control performance of windows (measured as ‘SHGC’) affects how much heat from direct sun enters the building, which affects heating and air conditioning energy. Tinted glass and ‘ceramic frits’ are common ways of achieving better solar control, but both also come with proportional reductions in natural daylight. ‘Soft-coat low-E’ coatings provide the best possible solar control for only a slight reduction in daylight. ‘Interlayers’ (inside laminated glass) and films can also be used. ‘Interstitial shading’ – wood or metal inside a double-glazed unit – is another option, but this reduces insulation performance.

 

Glazed Facades – Insulation

Reduces heating and cooling energy use.

 

The insulation performance of windows (measured as ‘U-value’, where lower is better) affects how much heat transfer occurs between inside and outside. Double-glazed units (‘DGUs’) perform better than single-glazing, and filling the cavity with argon gas improves their effectiveness. ‘Low-E’ coatings can improve both single and double glazing, with liquid-applied coatings available for pre-existing windows. The window framing system also has a major influence – one large pane performs better than many small panes. Timber performs better than metal, but metal window frames and curtain wall systems can be ‘thermally improved’.

 

Double Skin Facades

Reduces heating , cooling, lighting and ventilation energy use.

 

Double skin facades involve a secondary line of glass outside of the main glass facade. They allow the introduction of movable external shading on high rise buildings, which enables very clear glass to be used (improving natural daylight) and enhanced solar control (reducing air conditioning energy). Double skin facades generally have a better overall insulative performance, and can be designed to deliver effective natural ventilation in high rise buildings. They can be ventilated or sealed, and the distance between the glass can be wide or narrow. When narrow and sealed they’re called Closed Cavity Facades (CCF).

 

Internal Blinds

Reduces cooling and heating energy use.

 

Well-designed internal blinds can significantly improve the energy performance of windows. To provide the most benefit, they should have a light coloured backing and automatic control based on when the glass is in direct sun or the space is unoccupied. To reduce the amount of heat transfer, thicker blind fabrics or ‘Low-E’ fabrics can be selected, as can fabrics with a reflective metallised backing. In mechanically ventilated buildings, slots can also be designed into the blind ‘pelmet’ to suck out the hot air that accumulates between the glass and the blind fabric before it reaches the occupied space (which may reduce air conditioning energy).

 

Solar Photovoltaic Panels

Generate s electricity on-site.

 

Solar photovoltaic (‘PV’) systems use ‘strings’ of panels to convert sunlight into DC voltage that ‘inverters’ then convert to useful AC electricity. If strings face different directions a ‘multi-string’ inverter can be used, or every panel can have its own ‘micro-inverter’. Ideally panels face north, with a tilt roughly equal to the location’s latitude – but if space is limited then other options are worth considering. System efficiencies vary; typically the more efficient the more expensive. ‘Embedded networks’ enable local sharing of excess solar electricity, which can improve the business case.

 

LED Lighting

Reduces lighting energy use.

 

Light Emitting Diode (LED) lighting provides more light for the same amount of electricity when compared to fluorescents, metal halides and halogens. Less waste heat also means less air conditioning energy. LEDs reach full brightness instantly and can be turned off and on again quickly, allowing controls such as occupancy detection to be used. In the majority of applications it is important to choose LEDs with a high Colour Rendering Index (‘CRI’, measured out of 100), which affects how accurately the human eye perceives colour. They also tend to have exceptionally long lifespans, meaning less maintenance.

 

Occupancy Detection

Reduces lighting, ventilation , heating and cooling energy use.

 

Occupancy detection uses sensors to identify when people are no longer using a space and switches-off (or turns-down) building systems, saving energy. This is common for interior lighting, but it’s also effective for heating, ventilation, air conditioning and exterior lighting. There are a variety of different sensor types, suitable for a range of different distances. Some are designed to detect movement; others detect ‘presence’ (when someone is present but not moving). Systems are even available that have one occupancy sensor per light, providing a high level of responsiveness and energy efficiency.

 

Daylight Dimming

Reduces lighting energy use

 

Daylight dimming (sometimes called ‘daylight harvesting’) uses sensors to identify when there is a good amount of natural daylight available and turns down lighting, saving energy. The sensors used are called ‘PE cells’ (photoelectric cells) – for external lighting it’s normally just called ‘PE cell control’. A sensor can either be built-in to every light or shared between a group of lights – but it’s important to keep groups of lights small (because, for example, blinds might be adjusted). Internally, it provides the most benefit near the facade, skylights and atria.

 

Power Factor Correction

Reduces peak demand on the grid.

 

Large buildings are often charged not just for how much electricity they use, but also for their ‘peak demand’ (the peak power drawn from the grid at any time). In many locations this is based on ‘apparent power’ (measured as ‘kVA’, where lower is better). For buildings that have a poor ‘power factor’ during peak periods, ‘power factor correction’ equipment can be installed which reduces the apparent power drawn from the grid, thereby saving money. The main causes of poor power factor tend to be ‘AC’ motors (including pumps, fans and appliances) and some ‘switched-mode’ power supplies for computer equipment.

 

Building Management Systems (BMS)

Reduces heating , cooling and ventilation energy use.

 

A Building Management System (‘BMS’) is a dedicated computer and network that controls all the equipment (such as pumps, fans, ‘dampers’, chillers and boilers) that are part of a building’s heating, ventilation and air conditioning system. They can provide very sophisticated control, but their influence on energy efficiency depends on how they are designed. Control philosophies differ – and shifting the emphasis from precise temperature control to energy efficiency can realise substantial savings.

 

Installing more sensors can also enable more sophisticated approaches and help to verify that the system is behaving as expected.

 

Solar Hot Water

Reduces hot water energy use

 

Solar hot water systems collect heat from direct sun, usually for domestic hot water purposes – reducing the requirement for gas or electricity. In ‘flat plate’ systems, water flows through a dark-coloured panel. In ‘evacuated tube’ systems, a liquid flows through dark-coloured double-walled glass cylinders, then transfers the heat to water in a storage tank. Evacuated tube type systems are more thermally efficient, particularly in cold weather. Usually solar hot water systems are fitted with a gas or electric heating element to ‘boost’ the hot water temperature when the solar contribution alone isn’t sufficient.

 

Under-Floor Air Distribution

Reduces cooling energy use

 

Under-floor air distribution (‘UFAD’, sometimes called ‘displacement’) systems deliver air through the floor and remove it at ceiling level. Rather than mixing the air in a space and diluting pollutants, air rises up gradually, carrying pollutants and heat away from people. Cool air delivered via UFAD is typically around 18°C (to avoid cold draughts) – not as cold as in conventional systems, which allows chillers to operate more efficiently, and increases how often they can be switched off as part of an ‘economy cycle’. Control of humidity without the excessive use of ‘reheat’ is an important consideration; the use of ‘split cooling coils’ is one approach.

 

In-Slab Heating & Cooling

Reduces heating , cooling and ventilation energy use

 

In-slab heating and cooling systems pump hot or chilled water through pipes to affect the temperature of the surrounding concrete and provide localised heating or air conditioning (or influence the temperature of the thermal mass). Pipes are either cast into the concrete slab, or laid on top and covered with a screed. Tall spaces are ideal candidates – the temperature above people’s heads can be allowed to fluctuate, which reduces heating and air conditioning energy. ‘Zoning’ of the system into a number of smaller areas should be considered to help compensate for relatively slow warm-up and cool-down times.

 

Ceiling Fans

Reduces heating and cooling energy use

 

Faster air movement results in people feeling cooler without any change to the air temperature. Because of this, ceiling fans can be used to keep people cool while providing less air conditioning (or no air conditioning) – saving a significant amount of energy. In tall spaces that have heating, ‘destratification’ fans can be used to push warm air down to floor level (which would normally rise up due to its natural buoyancy) – meaning less heating energy is required. Products are also available that achieve the same effect without the spinning fan blades. Fans with a low input power (measured as ‘W’) should be selected.

 

Chilled Beams

Reduces cooling energy use

 

Chilled beams are coils at ceiling level with chilled water circulated through them. The chilled water need not be as cold as that in other types of air conditioning system, and as a result chillers operate more efficiently. A ‘passive’ chilled beam has a fully exposed coil and air flow driven by natural convection, with a partially radiant cooling effect. An ‘active’ chilled beam has a fan that forces air across the coil. The dedicated outside air system required with either type needs to be carefully designed to avoid condensation problems. Typically larger buildings are better suited.

 

Guidance for Existing Buildings

NABERS Energy and Green Star Performance are the most common tools utilised to benchmark operational energy performance. For market sectors which they don’t cover, benchmarking is not as straightforward – but various organisations do have other tools under development. The most common place to start when trying to improve the performance of existing buildings is with an ‘energy audit’. Some in-house facilities management personnel have the skills and experience to undertake an energy audit, but it is also a service offered by a number of specialist and building services engineering consultancies.

 

The Australian – New Zealand Standard AS/NZS 3598 defines three different levels of audit. A ‘Type 1’ audit provides an introductory assessment of how energy is used on site (known as an ‘energy balance’), and identifies the broad-brush initiatives appropriate for implementation. At the other end of the spectrum, a ‘Type 3’ audit provides a highly detailed assessment, with detailed initiatives and accurate estimates of costs and savings – typically most appropriate where a Type 1 or 2 audit has already been undertaken. A number of organisations are now developing more specifically targeted ‘NABERS Roadmaps’ for their buildings, which lay out a structured program of works to achieve each additional 0.5 Star NABERS Energy rating increment.

 

The cornerstone of any Type 2 or 3 energy audit or NABERS Roadmap is good quality ‘interval meter data’ (energy use data in 15 minute, 30 minute or 1 hour increments) from on-site sub-meters. If this is not available or does not provide sufficient detail, then ‘energy data loggers’ can be temporarily fitted to electrical circuits. It is important to note that not all initiatives to improve the performance of existing buildings actually involve physical works. There are normally substantial improvements to performance that can be achieved via improved energy management practices, controls optimisation and retro-commissioning.

 

How to begin the Process and find out more.

Building design appraisal to upgrade aesthetic finishes, services, together with infrastructure & Energy Assessments

 

RBi Architectsis offering to undertake an on site inspection and appraisal of your building for a nominal fee.

 

A report will be delivered with recommended upgrade solutions and various approximate capital costs, as well as potential running cost savings and how they may relate to a pay back period.


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