SANS 10400XA and SANS 204 both cover Energy Efficiency in Buildings
and were published in September 2011. They specify the compulsory
design requirements for energy efficiency in buildings and for services in
SANS10400XA includes SANS 204 as a Normative reference, meaning
SANS 204 should be read as an integral part of SANS10400XA.
SANS10400XA however, can only be described as a partial copy of SANS
204 so if you read SANS 204 you can ignore SANS 10400XA.
We will therefore cover SANS 204 here. But, if someone understands why
there are two different standards, will they please explain it to us.
SANS204 is a compulsory standard, and all the requirements have to be met. The standard focus mainly on domestic buildings.In our opinion, the standard results in little more than an irritation. To demonstrate this, let’s take lighting where the standard implies a minimum of 60 Lumen per Watt. Geysers must effectively be insulated to a R-Value of two, etc.We found that lights, geyser insulation, in fact, everything that we checked in hardware stores, will not result in compliance to the standard. The problem is therefore that you cannot readily source items which will result in a compliant building.There also seem to be no as-built enforcement of the standard, meaning that, after plans are approved, sub-standard energy performing products can be used with no consequence.In the paragraphs below, we will focus on the application of the standard to a 300 square meter house as an example.
The requirements at a glance
The requirements are described in paragraph 4.1 thru 4.6 as follows:•4.1 - Site orientation•4.2 - Building orientation•4.3 - Building Design•4.4 - Building Sealing•4.5 - Services•4.6 - Ventilation and Air ConditioningThe standard refers to climatic zones throughout. These zones are shown below. In the standard all quantitative requirements are listed by zone. You can immediately see that the blue zone and the dull yellow (or whatever) areas hardly represent equi-climatic zones. Midrand and Sutherland are classified in the same zone. That should tell you something.
4.1 and 4.2 - Site and Building orientation
It is clear that the authors of the standard believe that all bedrooms and living areas should point north. This also implies that a house in South Africa has a bigger heating than cooling requirement.They refer to Annex B to illustrate the energy (heating and cooling) consumption. The energy consumption for six major cities are listed. A North pointing house in Johannesburg is listed on a graph as needing about 500 kWh pa heating energy consumption. This implies that the energy consumption is independent of the house’s size, which sounds wrong, so we have to assume it’s per square meter.So, according to the standard and the above assumption, a 300 m2 house will consume 12,500 kWh per month, i.e.: an electricity bill of R 15,000 pm for heating and cooling only. That is unlikely but possible and we have seen it twice: The first one was a house on a golf estate where the kids had air conditioners in their rooms and left their sliding doors open with the air conditioners running daily. The second one was a house on an estate that also had most sliding doors open and had the underfloor heating at 30 degrees.A normal house should consume 20% of the specified consumption, and an energy efficient house should consume 10% of what the standard says.
4.3 - Building Design
There are two energy consumption tables listed under paragraph 4.3. They indicate the maximum demand and the annual energy consumption. Here they mention “per square meter” and the figures more or less agree with Annex B.Again the figures are so high that they are meaningless. A hotel, for example, is specified at around 600 kWh / m2 pa (inland). That should be about 320 kWh / m2 pa and greed hotels should be closer to 200 kWh / m2 pa.The maximum demand specified is over 25 kVA peak for my 300 m2 house example, which is again double of what one would expect. A 60A single phase connection is only 13.8 kVA.
The standard specifies that floors must be insulated to an R-Value = 1 around the edges of the slab (for a house <500 m2) and if you install underfloor heating, then under the slab as well. This is a sensible requirement.
If you consider the standard applying to residential buildings, then they are actually specifying a cavity wall with about 35 mm of good insulation between the two layers of brick. That is for equally cold cities like Sandton, Midrand and Sutherland (it would have been funny if it was’nt serious). Most owners struggle to get builders to install damp proofing, so make that happen!
Fenestration (that is Windows in English)
Considering that South Africa uses single glazing with clear windows, the fenestration requirements are in my opinion too tight. If you want to fit, for example, sliding doors on bedrooms, forget it. The maximum window area for warmish zones are determined as follows:Take the room Area times 1.4 divide by 5.6 for wooden frames (divide by 7.9 instead of 5.6 if you have aluminium frames). That works out to 25% of room area for wooden frames and 18% for steel and aluminium frames. For Johannesburg it works out to 15% for steel and aluminium and 21% for wooden frames.So, to fit a 2.4 meter aluminium sliding door in Johannesburg, the room has to be the size of a double garage, and then you may not have any other windows in the room. Does that sound right?We are not going to go into the complexities around shading etc. which impact the calculations. If you calculate the solar heat gain which they must have considered, they seem to have forgotten that most houses have curtains or blinds.The standard essentially calls for dark dungeons for houses.
A lot of heat is gained and lost through a ceiling, so we are all for adding insulation to a ceiling. A ceiling board plus the surface air film resistance won’t contribute a lot more than R = 0.2, so the insulation R-Value must be around 3.0 to comply to the standard. That is a bit excessive for South Africa. A thickness of 50 mm, which translates into an R-Value of 1.25, sounds right. This is over specified.
One of the facts that everyone including the SANS committee apparently missed is that roof lighting replaces light bulbs. Our estimate is that sunlight shining through a roof is about 80 Lumen / Watt. That is a pretty good bulb with little heat for the given light levels, so we would not have bothered to specify roof light heat gain.
4.4 - Building Sealing (air tight)
In Germany, for example, they pressure test newly build houses. The most cost effective way to build there, is to buy a factory built house and have that installed. Then the cost is only double the cost per square meter of a luxury house in South Africa. Testing a house for air leakage is South Africa? Get real.
4.5 - Services
Lighting and Power
SANS 204 (Table 12, Occupancy class H3 and H4) specifies that a house should not use more than 5 Watt per square meter and refers to SANS 10114 for light levels. SANS 10114 is not all that clear about light levels for different rooms but 200 Lux is about the minimum going up to 500 for reading and other work areas. Let’s work on an average of 300 Lux. This means we need lights giving us 60 Lumen per Watt.Incandescent lights hover around 15 Lumen per watt with halogen being a little better at about twenty but still far under the 60 that we should aim for. So, all incandescent types of light are out and Fluorescent and LEDs are in. Note that most LED lights sold in hardware stores are under 60 Lumen per Watt, so they don’t comply. Hence my comments in the summary.
The standard is simple. More that 50% of hot water heating must be provided by methods other than electrical resistance heating. We understand the intention, but the wording and criteria seems wrong. What they should have said is that hot water systems must be designed such that the total heat energy gain of the water must be at least double that of utility supplied energy.The standard also specifies that exposed hot water pipes must be insulated to an R-Value of 1 (if <80mm in diameter). This is sensible and very cost effective. It translates into an insulation thickness of about 22 mm when using a good insulator on a domestic water pipe. Again the 10 mm thick insulation sold at plumbing and hardware stores do not comply.Geysers should be insulated to an R-Value of 2. Here the standard is on target. This is higher than the SABS specification for geysers, as sold, where the R-Value is about 0.55 - 0.75. Therefore the insulation added to a geyser during installation should have an R-Value of around 1.25 to 1.45. That excludes the 25 mm thick insulation sold at some hardware stores. Look for the R-Value on insulation product packaging, else don’t buy it.On pipe lengths the standard is too soft stating that it should be minimised where possible. In practice, if you have a 22mm hot water pipe and insulate it to an R-Value of one, it would loose the same heat than if you use 10mm instead of 22mm insulation and reduce the pipe length by 33%. Now add the heat loss because you have to flush the cold water from the hot water pipe, before you have usable hot water, and you realise that the focus should be on pipe length, i.e.: the geyser position in the house.
4.6 - Ventilation and Air Conditioning
The standard specifies a fair bit around the design of air conditioning systems. It all makes sense and represent best practice. There is one specification in paragraph 184.108.40.206.3 b) which specifies that 75% of energy for reheating shall be recovered from site. If you look at the performance of the best heat recovery methods used in Industrial applications, you will see that that is pretty impossible.We also maintain that the only practical situation for heat recovery is where you replace heat for reasons other that to make up for heat gain or loss, i.e.: where you have a hot or cold stream leaving the building. (Food drying, volatile gasses etc…)One of the design criteria, which we believe should have been included is that the temperature of the air intake of outdoor units under stable full load conditions should not differ from the ambient air temperature by more than say 2 degrees. This is to prevent the bad practice of outdoor units being installed in badly ventilated areas (such as basement parking areas) which reduces the efficiency by at least 30%.
You may have noticed that we are not very impressed with the standard and we believe the whole approach is wrong. Granted, it is version one and version two cannot see the light of day soon enough.The standard oscillates between too little and too much with very little hitting the sweet spot. Maybe the standard should simply put a tighter limitation on the overall energy consumption of a building and leave it to industry and green building associations to achieve that.Our second biggest concern is that the standard gives little consideration to the practical aspects of proving compliance. In practice it now means that the plans must show all the good stuff, but whether it actually materialises is another question. If there are still building inspectors around, we have not seen them.