Tag: energy efficiency

Energy efficiency in buildings, up to recently, has been a matter of choice. Having an energy efficient building is now, however, no longer just the preserve of those wanting to do the right thing – what was a voluntary standard was written into law in Sept 2011 and was implemented and has become applicable as of 11 Nov 2011. These are the new SANS 10400-XA: Energy Usage in Buildings, and SANS 204: Energy Efficiency in buildings. The only exception, as with the other new building regulations, is that where the design work on a project had commenced prior the publishing of the standard, an application may be submitted to the Local Authority within 6 months of the standard’s publication date, requesting that the application be dealt with in accordance with the prior regulations.

Not be confused with sustainable or ‘green’ building, which include criteria such as mbodied energy and renewable materials (i.e. timber); energy efficiency focuses only the energy usage of a building once the building is built. Typical issues effecting energy efficiency include orientation towards north, window sizing and positioning, shading, choice of materials with regards thermal and insulation properties, solar heating, natural cooling and daylighting. It is the planning and design of these aspects that are stipulated by the new regulations. SANS 10400-XA provides the ‘deemed-to –satisfy’ requirements for compliance with the National Building Regulations with regards energy usage, and SANS 204 specifies the design requirements to achieve the required levels of energy efficiency. An example of a deemed-to-satisfy requirement is, in the case of fenestration, where the total fenestration area is only up to 15% of the total floor area. It is in this case assumed that, given all the other requirements are met, such a building would not overheat or loose excessive heat due to fenestration. If the percentage is over 15% , which would be the case for most non-economic type housing ( or Victorian style houses with small windows) we get referred to the tables in SANS 204, which provide solar exposure factors for windows depending on orientation and climatic zone, as well as a host of other info, on which our calculations are based.

The success or not in achieving energy efficiency is the sum of many parts, as per the issues above, and in essence part XA tells us what sum of parts is required and SANS 204 provides guidelines and options on how to achieve this. As a rule, good design in terms of energy efficiency (as per SANS 204) will prevent the need to add potentially expensive measures, ie double glazing to large south facing windows (where a huge amount of heat loss would occur) or extra shading to west facing windows (which would otherwise cause the house to overheat), in order to meet the minimum requirements.

Below are some examples of the types of specification requirements:

Walls: Non-masonry walls shall achieve a minimum total R-Value of R2,2 in climatic zones 1 and 6, and an R-Value of R1.9 in climatic zones 2,3,4 and 5

Climatic zone map | Differentiation by climatic zone is an integral part of the regulations

Roofs: The insulation of roofs have been determined as the single biggest factor impacting on energy efficiency and this is where the most radical departure from ‘but this is the way we’ve allways done it’ (for the most part anyway) is required.

The mimimum R-Value of roof assembly ( ie all components of the roof and ceiling) required in Zones 1 and 4 is R3.7 with the other zones only marginally less. This means, for a clay tile roof for example, that once one has deducted the R value of the tiles, ceiling, airspaces etc. another 3.3 of R-value is still required by adding insulation. This equates to around 150mm of a typical cellulose fibre insulation, which is a lot more than has generally been specified up to now. For roof’s with exposed rafters it is even going to change the way we detail the roof construction – as with our current method of putting insulation between 76mm purlins there simply is’nt going to be anough space.

Solar Hot Water Heating: 50% of all hot water in new houses needs to be produced by methods other than electrical element heating – which, as solar water heating geysers still partially use electricity, it basically means all hot water must be supplied by solar water heating systems, or alternatively a heat exchange type heatpump.

Lighting: Lighting now also needs to be specified (as apposed to as previously just indicating a light point on the plan), taking in consideration light levels, energy demand and energy consumption.

So now, as designers, we really have our work cut out for us. I foresee some teething problems with the new regulations for some time yet as designers as well as local authority plans examiners get to grips with the new requirements. All architects and designers have to do a two day course in order to be recognized as ‘competent persons’ as required by the regulations in order to do the calculations, and expect some further delays in plan approvals until the building plans examiners are up to speed with the process.

While there has been a knee-jerk reaction and a cry of yet more over-regulation by some, this is a very necessary and well timed intervention in averting an energy crises. It is acknowledged world wide that the buildings are a massive consumer of energy, and this will position the construction sector in South Africa, as in some other parts of the world, as a leader in the move towards a sustainable future.

The standards can be purchased from :
https://www.sabs.co.za/index.php?page=standardspurchase