Fly Ash - Another Brick in the Wall for Greener Buildings

It’s a win-win equation for the construction industry and the environment, a distinct rarity. The construction industry has come under repeated fire for environmental damage in countless ways – construction waste, air, water/ soil pollution and the release of tonnes of carbon dioxide into the atmosphere. In fact, carbon dioxide has been calculated to contribute up to 26% of all greenhouse gases* plaguing the environment. In addition to the reduction of carbon dioxide emission, the use of fly ash bricks in construction has introduced a range of environmental benefits. As the world moves towards developing green buildings, the manufacture and increasing the use of fly ash bricks in construction has the potential to effect substantial environmental change.

The basic ideology of fly ash brick technology is the manufacture of climate-friendly bricks without using coal for the process. Traditional brick-making burns large amounts of coal and results in the emission of tonnes of carbon dioxide every year. Also, valuable topsoil is used for the manufacture of clay bricks. If fly ash brick use is adopted on a global scale, it has the potential to eliminate carbon emissions from the brick-making industry.

Understanding fly ash bricks - what they are made of, how they are made and how they are used – is essential to understanding the extent of their benefits. To get right into it, fly ash is an unwanted residue, resulting from coal-fired power plants. Typically, fly ash was disposed on large areas of land, resulting in both environmental damage and human health issues, especially around power plants.  An Increasing need for power drove the extensive mushrooming of coal-driven power plants, generating sizeable amounts of fly ash. Decades ago, fly ash bricks were developed without the use of coal. Fly ash is combined with lime and gypsum to produce fly ash bricks.

These bricks can be made in a range of sizes and strengths, perfect for their use in building construction. They need less cement and mortar than clay bricks. Cement wall plastering on exterior walls is not required when using fly ash bricks, as they are grey, already have a smooth, uniform texture and absorb substantially less water than other bricks. Lighter in weight than other bricks, fly ash bricks can be easier to transport. In addition, fly ash bricks do not require to be fired in huge kilns, a process for clay brick production that requires large amounts of burning coal, which adds to the greenhouse gas effect. This means that they do not contribute to environmental pollution.

Recognising their far-reaching impact, the World Bank is supporting a project to promote fly ash brick technology by granting entrepreneurs the chance to earn carbon credit revenues. A carbon credit is a certificate declaring that a company has paid to have the equivalent of one tonne of carbon dioxide or equivalent greenhouse gas removed from the environment. More than one hundred fly ash brick plants have earned close to $3.2 million*.

So, how does it work?

Traditionally, bricks were made with clay and sand or soil moulded together and dried and burnt. Burning these bricks used a considerable quantity of fossil fuel, which then generated carbon dioxide, contributing to global warming. A method called FaL-G, or Fly ash Lime-Gypsum, replaces the soil ingredient of traditional clay brick manufacture with fly ash. The bricks are made at room temperature, instead of over 2000F (for clay bricks), thus eliminating the generation of greenhouse gases. By preventing fly ash from being deposited on land, this method reduces water, air and soil pollution. In addition, human health benefits include the reduction of respiratory ailments of residents near power plants.

The quality of clay bricks had been deteriorating for some time, due to the poor quality of topsoil used to manufacture them. The FaL-G brick method has produced strong bricks. They can be created in different sizes and strengths and can speed up the construction process, while saving mortar. Here’s how:

Fly ash and water are compressed at 4000psi and then cured for 24 hours in a steam bath. The bricks are then toughened with an air-entrainment agent. Due to a high concentration of calcium oxide, the bricks can be considered self-cementing. This method saves energy and reduces mercury pollution in the environment.

Materials used to create fly ash bricks include:

• Fly ash
• Fine sand or stone dust
• Lime – a source of calcium carbonate
• Gypsum – to help shape the bricks
• Cement – to increase cohesion and strength

Once manufactured, fly ash bricks enable a host of benefits.

Benefits of Fly Ash Bricks

• Low absorption of water (13-15%, compared to 20% for clay bricks), thus near absence of wall dampness
• Lightweight
• Fuel saving 
• Reduced drying losses
• Reduced linear drying shrinkage
• Strength – ideal for construction
• Clay conservation
• Conform to IS:3102-1976 standards
• Uniform shape, size, thus minimal plaster use
• Gypsum plaster and plaster of Paris can be directly applied
• Reduced need for cement mortar
• Resistant to salinity and water seepage
• Reduced bulk density - reduced resultant load on load-bearing walls
• Reduced wastage of bricks, compared to clay bricks

Fly Ash Properties that Are Advantageous in Construction

• Round shape: Fly ash particles are round, so they are easy to mix.
• ‘Ball bearing’ effect: Fly ash particles create a lubricating action when the mix is in a plastic state.
• Strong – Combines with free lime for increased structural strength over time.
• Dense – Fly ash is dense, resulting in decreased permeability and increased durability
• Resistant to the harmful effects of sulfate, mild acid, soft water and sea water.
• Reduced drying shrinkage, due to reduced water content
• Reduced heat generated when reacting with lime, thus reduced thermal cracking
• Improved cohesion leads to reduced segregation, which could have caused rock pockets and blemishes

Since green buildings are also defined by their energy consumption, one of the additional advantages of using fly ash bricks is its ability to provide effective thermal insulation. This means that buildings consisting of fly ash bricks are cool in summers and warm in winters, reducing the energy consumption of the buildings.

Even sounds are more effectively absorbed, since fly ash bricks are sound absorbent and restrict sound transmission, making interiors quiet. Fly ash bricks also have high fire resistance, making them a great choice of material for fire prevention services.

All these advantages have enabled the use of fly ash bricks in factories, warehouses, power plants, as well as homes and high-rise buildings. With the right architectural CAD services support, especially from accurate, experienced and cost-effective drafting services in India, homes and other buildings around the world can be designed to effectively use fly ash bricks to their advantage in creating ‘greener’ buildings.

Chilled Beams – Why Are They Popular?

We need them for shelter, warmth or cooling, but buildings are required to be more than that these days. They need to look good, feel good and be good. By being good, we mean they need to be energy efficient. Ideally, designers or Building Services Design Consultants must plan for energy-efficient mechanical, electrical and plumbing (MEP) engineering design, and chilled beam technology is one of the options that hydraulics and plumbing design services offer for energy-efficient systems, with the close collusion of heating, ventilation and air conditioning (HVAC) mechanical engineering consultants or .

Growing in popularity in Australia, Scandinavia, central Europe, the US and the UK now, the first stirrings of chilled beam concepts, surprisingly enough, occurred in the early 1900s. In those days, under-sill inductions units were being developed. Then, during the 1960s, water from the River Thames was used by Shell Oil Headquarters in London to cool their building (using a secondary heat exchanger in the plant room). At the time, it was both efficient and just a little bit sci-fi. The significance of this system lies in the nature of building services energy consumption.

It is widely accepted that HVAC systems are responsible for almost half (49%) of all building services consumption. Cooling and humidification account for 3% of the total. A component of MEP systems that can reduce that percentage is always welcome. So, what’s so special about chilled beams? Just what are they?

Chilled beam systems are a specific type of air conditioning system that can both heat or cool large buildings. Funnily enough, chilled beam units appear similar to fluorescent lighting fixtures and are not necessarily always chilled. Essentially, chilled beams cool spaces using water rather than air. Copper pipes carry chilled or heated water and are passed through a ‘beam’ (a heat exchanger or radiator) which is hung a short distance from the room’s ceiling. A coil of aluminum fins on copper tubing inside a metal casing is what makes up the beam. A chilled water system cools water to between 55°F and 65°F. The beam thus cools the air around it, and the air becomes dense and moves downward. Warm air moves up from below to replace it, is cooled and then circulated back down, causing a constant flow of convection and cooling of the air in the room. 

Chilled beam systems typically use three main components: air handling units (AHUs), chillers and pumps. If the system is required to provide heating, a boiler is used. These units form a ceiling-mounted HVAC system that ultimately saves energy, increases interior comfort and happens to be a quiet operator.

There are two main kinds of chilled beams – active or passive. Active chilled beams connect to a system of ducts served by a central AHU (air handling unit). This system delivers fresh air through induction nozzles. The nozzles use a heat exchanger coil to induce secondary room air. Supply air is mixed with chilled air through the ventilation nozzles. Heating in active chilled beams works the same way, delivering warm air into the living space. Heating and cooling capacity is increased with this forced circulation. Using active chilled beams results in the need for reduced energy to operate fans, due to low pressure and the reduced amount of primary air that is circulated. 

Passive chilled beams circulate air through natural convection means, without using a fan. Exterior air is supplied through a separate diffuser or grille into the space. Water passing through it chills the beam and the air around it is cooled. As the surrounding air cools, it becomes denser and moves down in the room space. Warm air, which rises, then replaces the cool air. A chilled water temperature of 14-16˚C is maintained by chillers to flow through the system. The return temperature will be a few degrees warmer. The chiller works more efficiently because of the higher chilled water temperatures in chilled beam systems and lower temperature lift. 

A third type of chilled beam that has made a recent entry into the industry is a multiservice chilled beam, or MSCB. These are specifically designed for each project and provide heating, cooling, ventilation, lighting and sound, fire and cable pathway services. They are typically preferred in commercial buildings in Europe. 

All chilled beam systems reduce energy. The AHUs can be installed with energy-recovering devices so that energy can be recovered from the exhaust air and transferred to the supply air. Due to the higher chilled temperatures, free-cooling can be used for longer, where exterior low air temperatures can be used to chill the water. Both chilled water and hot water can, at low temperatures, be produced by air and ground source heat pumps. These heat pumps use less energy than boilers and chillers.

Saving Energy 

So, what kind of savings in energy result from using chilled beams?

The potential to save energy using chilled beams may range from 20% to 50%, depending on the weather and type of building. Water is known to transfer more energy than air. The use of water in chilled beam systems result in less energy usage. Also, since heating and cooling is delivered directly to the relevant space, chilled beams help facilities reduce the energy required for ventilation fans, saving money in the process. Overall heating and cooling costs are reduced because chilled beam systems transfer outside air to interior spaces where it is needed, rather than bring it into the entire facility and then condition it.

Benefits of Chilled Beam Systems

Chilled beam systems offer other potential advantages besides energy savings, including: 

• No moving parts result in quieter operation
• Not requiring mechanical rooms or large ducts results in an increase in available space
• Buildings with limited space to accommodate conventional conditioning systems can be retrofitted
• Maintenance needs are reduced, since there are no filters to maintain and beams stay dirt-free
• Widely applicable for commercial buildings
• Significant thermal efficiency
• Requires less ceiling space and height than traditional systems, thus facilitating shorter buildings with the same floor space for tenants.

Further benefits may be environmental, in that recyclable materials, such as steel, aluminium and copper, can be used to manufacture chilled beams. Potential resale value is increased and the procedure for decommissioning is easier, as scrap metal merchants prefer the materials free of refrigerants and oils. Also, chilled beams contribute to long-term sustainability in both new and renovated buildings.

Typically, a conventional cooling or heating system uses forced air. A forced air system is less efficient and more expensive due to the requirement of large ducts in taller buildings. A typical chilled beam system requires less outside air to operate than a forced air system. It only needs one air change every hour and uses air from the outside air to pressurise the space. Using a forced air system, eight to ten air changes of fresh air are needed.

Also, chilled beam systems can be prefabricated off site and then installed on site, reportedly saving up to 75% in labour costs.

The diverse benefits of chilled beam systems, including long-term costs, make these systems a preferred choice for hydraulics and plumbing design services in a building’s MEP engineering design and also Building Services Coordination. With experienced and technically certified HVAC mechanical engineering consultants on board, the trend of chilled beam systems seems to be headed in the right direction for sustainable construction.