How do building simulation services help buildings become efficient?
Building simulation is a software based analysis used for optimising energy efficiency of the project building by architects during the design development stage. It consists of energy simulation, daylight and lighting simulation and climate analysis. It assists the architects and developers to study the impact of various factors such as incident sun radiation on the building, orientation of the building, shading devices, thermal insulation of building facade (glass, wall & roof assembly), energy efficiency of air conditioning and lighting equipment, renewable energy systems (if any), etc. on the energy consumption of the building. Typically more than half of the total energy requirement in a building is for air conditioning and lighting.
Considering most parts of India have hot climatic conditions, we do not recommend clients to go beyond 40% of glass facade. Energy conservation measures (ECMs) such as shading devices, recessed windows, high performance glass, autoclaved aerated concrete (AAC) or fly ash blocks for walls and solar heat reflective paint can considerably bring down the heat load for the building. These ECMs are included in the design and are simulated in the software to document the proposed energy savings. Based on the costing, developer selects the best combination of ECMs from the ones suggested.
The daylight simulation is a process to determine interior spaces that are well lit throughout the day-time operations and the areas where artificial lighting is necessary. Lighting simulation helps in designing the artificial lighting to maintain uniform lumens levels, in understanding the light distribution its throw and intensities in 3D visualisation, to reduce the lighting power densities or excessive lighting and to check whether the designed lighting flux is trespassing the site boundary.
Climate analysis includes solar analysis, sun path analysis, shading analysis and wind analysis. Solar analysis is extremely helpful at the early stages of design development, where day lighting and solar gains are important factor in defining the footprint and basic envelope. The sun path analysis helps in the design of exterior shading. Shading analysis helps an architect to design the sunshade/shading devices (its shape, size & location) and wind analysis helps in determining the wind movement analysis from micro-climate point of view to ensure the natural ventilation inside the building to mitigate the indoor air pollution.
For a building to be green, it has to be green from day one. That means the design. What does that involve?
Green building design is based on form follows function which is associated with modernist architecture. This principle rests on the concept that the shape of a building or object should be primarily based upon its intended function or purpose. This, however, should not be mistaken as a compromise in the aesthetic appeal of the design. In fact, buildings all around the world are being built with its functionality and sustainability in mind without losing out on its visual appeal. Therefore, the focus is on building something that is functional, aesthetic and sustainable at the same time.
Passive cooling techniques should be incorporated in the building design if it needs to be truly called a green building. Passive cooling is a form of building design that involves preventive and natural heat dissipation techniques for improving indoor thermal comfort at low or nil energy costs. Preventive techniques include orientation of the building facade along the north south direction, thermal insulation of the building envelope and optimal design of shading devices. Natural cooling could be achieved by way of cross ventilation and evaporative cooling techniques.
What are some of the conditions and insulation requirements to be kept in mind for green buildings?
Thermal insulation for building envelope, which consists of roof, fenestration, glazing and the exterior walls, is the most important aspect of a green building project. A thermally insulated building envelope involves using materials that reduce heat transfer by conduction, radiation and convection. It helps cut down the heat load in the building, downsizing the air conditioning equipment required to cool the spaces and hence, results in lowering of the capital costs for the project. Thermal performance of fenestration, glazing, and wall and roof assembly depends on solar heat gain coefficient (SHGC) and solar energy transmittance measured by U-value. Lower the SHGC and U values better are the thermal insulation properties of the wall, roof, fenestration and glass.
Using insulation materials like extruded expanded polystyrene (XPS) and moulded expanded polystyrene (EPS) decreases the SHGC value of the wall and roof assembly, thereby offering good thermal insulation. But due to incremental costs, developers restrict the usage of insulation materials to roof. As a cheaper alternative to insulation materials for exterior walls, one may opt for fly ash bricks or AAC blocks instead of clay or normal concrete bricks, as they have excellent thermal insulation properties. Fly ash acts as a good insulating material and is used in both Fly ash bricks as well as AAC blocks. The autoclaved aerated concrete is a versatile lightweight construction material which has low density and excellent insulation properties. The low density is achieved by the formation of air voids to produce a cellular structure.
Undertaking a green retrofit of a building brings about both tangible and intangible benefits to the owner. What are your views?
Buildings are an integral part of a city’s heritage, skyline and distinct character. Although seen by many as a valuable asset, they also consume significant energy, resources and investment. Existing buildings form the main bulk of the building stock, and they are a significant consumer of energy as well. Maintenance, new technologies and occupancy changes also need to be continually dealt with. Upgrading existing buildings not only helps to preserve the character of a place; it is an optimal solution for owners, tenants, the community and the environment.
There’s a misconception that green buildings cost more.
By using building materials with good thermal insulating properties, high efficiency HVAC and lighting equipment, solar water heating, rain water harvesting systems, etc. as a policy decision for all projects, the incremental costs can come down to as low as 1-2%.
Typically a certified or silver rated green building would have incremental costs in the range of 3-5% over conventional ones, whereas the cost can go up further for Gold or Platinum rated projects.
In commercial green buildings, these incremental costs could be easily recovered within a few years. We should understand that green buildings are more about sustaining the resources for future generations than about generating economic returns out of them.
What are appropriate building materials that revolve around the concept of science and easily available?
The choice of building materials and products play an important role in conserving natural resources like limestone used in cement, iron ore used in steel bars, aluminum used in claddings & frames, etc. by recycling waste, in reducing carbon emissions by purchasing locally available materials (within 400 kms) and in improving indoor air quality by eliminating or lowering the Volatile Organic Compounds (VOCs) found in paints, adhesives and sealants. Some of these materials are mentioned below:
Fly ash is the byproduct of coal fired electric generation plants in the form of finely divided residue resulting from the combustion of ground or powdered coal. Its bricks are used for load bearing walls and can result in making finer finishes with even surfaces. Though they are costlier than normal bricks by around 18 -25%, on a larger scale, the cost of the project can be reduced as the dead load over the columns and beams are lesser, wastages minimal and they require less labour time.
Lower VOC paints preserve both indoor and outdoor air quality and reduce the incidence of eye or respiratory irritation.
Composites are made from rubber and plastics and look like natural materials appearance like wood and slate with the added advantages of being extremely light, thus making construction much easier. Composites are often manufactured from recycled materials.
AAC blocks are a derivative of fly ash that is combined with cement, lime and water and an aerating agent. Made from non-toxic ingredients, it can help make construction process about 20% faster and 2.5% cheaper by reducing the running costs for commercial spaces such as hospitals, schools, etc.
Compressed earth blocks are made from clay, sand and cement and thus biodegradable and also easily available because it can be made locally from any soil with a proper mix of ingredients like sand and cement. It offers fire resistance and is sound proof. However, they are not suitable for smaller homes and buildings.
Particle boards are made of wood chips, sawmill shavings, or sawdust. More economical than solid wood, these ‘green’ particle boards can help bring down building costs to a great extent. Particle boards have low moisture absorption, high internal bonding and dimensional stability.