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Early CFD Analysis For Improved Energy Efficiency In Buildings

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Many of the decisions made in the early stages of a building's design have a significant impact on the energy efficiency at a much lower cost. Although many buildings have energy efficiency strategies embedded in their conceptual design, it is rare that these concepts would be fully analyzed and verified at the initial design stages. 

In this article, we explore how building simulations using a computational fluid dynamics (CFD) tool like EXN/Aero, can evaluate a variety of thermal characteristics and low carbon technologies at the early design stage, resulting in a more sustainable building and a higher rating of energy performance.

It is widely accepted that buildings have a large impact on energy consumption and CO2 emissions. In the UK alone, it is estimated that the energy consumption share of buildings, is about 46% of the total energy consumed, which results in the CO2 release of approximately 66 million tonnes into the atmosphere (C H Pout et.al 2002). In the United States, buildings account for 39% of CO2 emissions. Most of this energy use is for the provision of heating, cooling, lighting and hot water supply. The design of comfortable and energy efficient buildings can be deemed a successful way to reduce to building energy consumption and thereby CO2 emission. 

Earlier Analysis & Decisions

It sounds obvious, but decisions made during the very early stages of a building design process would have a substantial impact on the performance of the resulting building. At a time when building design is no longer merely a question of cosmetic appearance and functionality, environmental performance should be considered during the planning stage, using modern tools to facilitate a more informed approach to sustainable design.

Building performance analysis is often carried out by a contracted building services engineer during the latter stages of the design process, and at a time when decisions regarding fabric, shape, layout, glazing and orientation have been made and fixed. As a result, the ability to source and utilize appropriate passive measures will have been heavily restricted leaving mechanical conditioning systems as the only way to maintain occupant comfort. CFD simulation has the potential to assist with many HVAC challenges, even in the most complex environments.

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In addition, the diagram below shows the biggest impact (across a number of industry sectors) if CFD simulation was not used by design engineers.

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CFD - Used By Architects?

CFD simulation software is more affordable and accessible than ever before. As a result, it surely makes sense to place simulation tools in the hands of architects and planners, who could then integrate building analysis in the very early stages of building design. This would result in more informed strategic decisions to be made from the start, and could even improve building performance.

Let's face it, the global drive for sustainable design isn't going away. In addition to being a legal requirement in some countries (such as the Energy Performance Certificates that are compulsory in the UK), it is a huge issue at the heart of many clients and prospective home owners. Using CFD simulation during early building design could enable architects and engineers to identify key energy loads, test potential strategies or ideas, and to compare various designs to optimize the final outcome.

Previous barriers have perhaps limited the widespread adoption of CFD by those in the built environment. We recently explored these in an article highlighting the role of simulation in challenging HVAC environments. Software tools like EXN/Aero can be accessed via the cloud on a pay-monthly basis, and the easy-to-use interface makes it easier for those in the built environment to incorporate its use. Engineering services provided by Envenio (Onboarding Program and Discovery Project) are also being targeted at those without prior CFD experience, who are working in the HVAC sphere and want to learn more about simulation.

Learn More About CFD Simulations

Early Analysis For Improved Occupant Comfort

The pursuit for occupant comfort contributes to the majority of a building's energy consumption, and can be affected by many environmental factors. Cooling and heating is used to regulate comfortable temperatures, fans are used to ventilate and prevent moisture build-up, and lighting is used to provide visual comfort. Passive measures can be employed to reduce and even eliminate some of these loads. A clearer (and earlier) understanding of predominant building loads enables designers to implement strategies that best utilize passive measures. 

Pain Example 1 - In a naturally ventilated building, overheating issues are often commonplace, and carbon dioxide concentration can arise where sufficient fresh air cannot be delivered through natural means alone.

Pain Example 2Where buildings are designed with vast amounts of glazing, excessive solar gains can occur. 

The pains given above are just three examples of areas of concern in building design. Early analysis with CFD simulation can help to establish the merits of a particular design solution and help architects and engineers to achieve an optimal outcome. Where issues with thermal occupancy comfort arise, being able to identify the problem early in the design process can prove hugely influential in developing passive or low energy solutions, before successfully implementing these changes into a final design.

mean velocity2-4

A CFD Simulation of a proposed Concert Hall

Early Analysis For Cost Savings

Energy efficient homes and buildings are not only kinder to the environment, but are also cheaper to run. Using CFD simulation earlier in the design process could save costs further, minimising the need for changes to the physical design when built, and allowing the most efficient design to be built in the first place. Simulation has the potential to provide cost savings at every stage of a building's lifecycle, potentially impacting architectural consultancies, construction companies, energy companies, and homeowners.

Conclusion

Changing a design through the early stages (while it is most flexible) can result in the overall improvement of energy efficiency without compromising on thermal comfort for occupants.

In addition, equipping architects and those involved during the very early stages of a building's design, can enable more effective decisions to be made at the most convenient time, potentially saving costs and time further down the line. 

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Try It For Yourself

Whether you're working on an operating room, an indoor farming plant, a new residential building, office block or tourist landmark, a proper CFD analysis can save a staggering amount of money on initial capital costs. In addition, ongoing simulation use can help to improve the building's overall operating and energy costs, meeting the increasing energy efficiency requirements of the built environment - something that is a leading priority around the world.

There's no excuse to not being able to take advantage of simulation. Envenio has created the Discovery Project and Onboarding Program to further assist those without CFD experience. 

        Our general purpose, cost-effective CFD, cloud solver reduces simulation times by up to 20x, and the platform includes a meshing tool, the solver, and a post-processing tool, as well as plenty of storage for your files. If you're working on a building project - or have any other HVAC CFD simulation requirements - why not try a free demo of EXN/Aero today and start using CFD for building design? 

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References 

C H Pout, F Mackenzie and R Bettle, Carbon Dioxide Emissions from Non-Domestic buildings: 2000 and beyond, BRE Energy Technology Centre , 2002

CIBSE, Weather, Solar and Illuminance Data. Guide J Chartered Institute of Building Services Engineers, London. 2002

CIBSE 2000 TM 23, Testing Buildings for Air Leakage, Technical Memorandum No. 23, Chartered Institute of Building Services Engineers

DETR, Good Practice Guide 245, Desktop guide to daylighting – for architect

2018-06-6 | Categories: HVAC, architecture, BIM

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