ENERGY MODELLING

MANUFACTURERS OF ENERGY EFFICIENT WOODEN WINDOWS, DOORS AND MOULDINGS K.Parker Joinery SAFIERA Accredited Manufacturer of Energy Efficient Wooden Windows and Doors GREEN BUILDING Here is an interesting article I received from Mike Barker of Building Physics. Mike is helping us to improve the standard of our products through simulations of U value. SHGC and Visual Transmittance. Striking a Balance The energy modelling approach allowed for by SA’s building energy usage regulations provides an attractive alternative to SANS 204 Is it possible to put up a better building at a lower cost and without the limitations of SANS 204? South Africa’s building energy usage regulations are not as restrictive as some may lead you to believe. The energy modelling approach allowed for by the regulations provides an attractive alternative. Project managers often act as client representatives and in doing so they take on the role of optimising the budget rather than just meeting it. In other words, they seek to squeeze the most value out of a project – both in terms of the delivered building and its long-term operating overheads. Avoid the constraints PMs will therefore be most interested in all the compliance routes allowed by SANS 10400 Part XA: “Energy usage in buildings”. Made mandatory on 9 November 2011, the amendments to the act require that buildings are designed and constructed so that they “are capable of using energy efficiently”. SANS 10400 XA, in turn, references the SANS 204 Standard: “Energy efficiency in buildings”. This is where a good deal of confusion arises. SANS 204 has been around for a few years and it’s easy to assume it’s the only game in town. But blindly following the SANS 204 prescriptive route will not necessarily deliver the least costly design or save the most energy. It is also important to bear in mind that 204, while a good starting point, is immature and untested. It does not take much to improve a typical South African building and therefore 204 did not have to do much to appear effective. However, what little it does, is very restrictive. Compared to other international building codes that are now over 30 years old and have had the weaknesses knocked out of them by good architects, wise quantity surveyors and even lawyers, SANS 204 has a long way to go. There will always be better ways to go about the business of designing energy efficient buildings. Two alternative compliance routes are expressly detailed in the act: 1. A rational design approach that demonstrates the energy usage of the building is equal or less than that of a baseline SANS 10400 XA building. 2. The theoretical energy usage, determined using specific software, is less than that of a baseline building as specified in SANS 10400 XA. How exactly is all this done? The answer lies in modelling the energy used by the buildings, using specialist software to simulate the annual operation of the building. This can then be utilised to improve a building’s design and to make informed decisions about the cost trade-offs. Energy modelling is a tried and trusted method widely used by modern integrated project delivery processes that are promoted by architects and engineers (e.g. American Institute of Architects, Royal Institution of Chartered Surveyors, and even PMBOK to a degree). Integrated design requires a detailed understanding of interactions in a building, and modelling should be incorporated early in the design process. To gain extra credits, energy modelling has been used extensively on over 15 000 LEED buildings and by the GBCSA’s Green Star rating tool too. Using a set of detailed equations that factor in every effect – from that of the envelope’s solar gains to HVAC performance – modelling calculates the energy used every hour of the year. A typical weather file and the schedule of the operations of the building are used. Such detailed calculations are precise, repeatable, and a least-risk rational design. Modelling is all about getting the balance right, of ensuring the design uses fenestration, thermal mass, and insulation in the right quantities and in the right circumstance to provide a building that is not only thermally and visually comfortable, but uses energy and materials responsibly. PMs need to be aware that Part XA further requires that an accredited energy modelling software be used. There are two Agrément SAapproved packages available currently. Moving toward net zero buildings Legislation in Europe requires new buildings to be so efficient by 2030 that they will have an annual net energy consumption of zero. This effectively avoids having to build new power stations, which has made our government take notice. Government is expected to follow up SANS 10400 Part XA with legislation requiring buildings to display labels showing their audited energy usage. The results of an energy efficient design will be there for all to see, with the building’s owners and prospective tenants able to pass judgement. Energy modelling as a rational design route is open and transparent and can withstand scrutiny by all parties involved. It assists the whole team to make decisions based on well-established building science. As such it is the least risky design option, and an invaluable tool that is available immediately to optimise building costs. Mike Barker (www.buildingphysics.co.za) A Committee Member of the International Building Simulation Association, and a member of ASHRAE & CIBSE. BuildingPhysics provided modelling for Africa’s first LEED NC 2009 Gold and Silver Buildings. Contact Mike: +27(0)11083 6987 / mike@buildingphysics.co.za