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The Emperor’s new Speedos: how home energy ratings really work in the tropics

Does Australia's energy rating scheme for houses actually encourage the use of air-conditioning?
In the 2014 AS Hook Address, Adrian Welke and Phil Harris of Troppo, well deserved 2014 Australian Institute of Architects Gold Medallists, had this to say about minimum energy performance regulations: “…we pat ourselves on the back for tackling greenhouse gas emissions with approval frameworks that are predicated on the inclusion of energy-heavy air-conditioning. A sealed, insulated box – an esky – becomes the ultimate energy efficient building paradigm. Come on… the emperor’s turned up in the nude again!”
As an examination of the submissions to the Queensland Parliamentary Inquiry into Energy Efficiency reveals, Welke and Harris were voicing concerns held by many tropical housing design practitioners in relation to the Nationwide House Energy Rating Scheme (NatHERS) tools
1. NatHERS tools simulate the temperatures inside a house using a full year of hourly weather data and the heat needed to be added or extracted to maintain comfortable temperatures i.e. heating and cooling. There are 69 Australian climate zones with this data available. To rate a house, the tools extract or add heat in the simulated house until a comfortable temperature is achieved. The amount of energy required to do this will determine the house’s energy rating.
Contrary to what many practitioners believe, though, new research has shown that Nationwide House Energy Rating Scheme (NatHERS) tools do not assume a sealed box, nor do they assume heavy use of cooling. A report I completed in 2012 for what is now the Department of Industry examined how NatHERS rating tools work in hot climates
2. The analysis showed the NatHERS tools assume that ventilation is used to make the house feel cooler by opening windows much more than they close windows and artificially cool the house. Second generation tools, introduced in 2006, simulate the internal wind speed in a house and the additional comfort this provides. Before extracting heat to make the house cooler, these newer NatHERS tools will first open windows to see if this makes the house comfortable. They only extract heat if ventilation is not adequate to maintain comfort. NatHERS tools assume that heating and cooling is available from 7am to midnight in living areas and from 4pm to 9am in bedroom areas. While overnight heating thermostats are lower than daytime thermostats, overnight cooling thermostats are the same as daytime thermostats. 
Typical tropical house design strategies like deep verandas, louvre windows and light colours all led to significant improvements in NatHERS star ratings in climates where cooling loads are greater than heating loads.
In houses designed for the tropics I evaluated in Darwin, the tools assume that windows are opened annually for around 66% of hours (i.e. average 16 hours a day) and the house is artificially cooled to achieve comfort 16% of the time (4 hours), which is comparable with reported hours of cooling use in Darwin. In a Brisbane house that I evaluated, windows were opened for, on average, 11 hours a day and it was artificially cooled for half an hour. This report also showed that the comfort benefit due to air movement predicted by NatHERS tools was 50% higher in a house designed to promote cross ventilation (elevated, windows on opposite sides of all rooms) than in a typical volume market house. Maybe it should be even better, but it is showing a significant benefit. Further, typical tropical house design strategies like deep verandas, louvre windows and light colours all led to significant improvements in NatHERS star ratings in climates where cooling loads are greater than heating loads. This shows NatHERS tools do not assume a sealed box. With this level of use of ventilation, the emperor must at least be wearing his speedos.
So if all this is working correctly, why are experts so dissatisfied with the rating? One contributing factor may be that the better performance of bedrooms in traditional tropical houses isn’t being rewarded by the rating. In NatHERS tools, bedroom cooling loads are much lower than living room loads because they mainly cool overnight when outdoor temperatures are cooler and there is no sun. Bedroom cooling loads can be as low as only 12% of the total and are generally around 25%. As a result, their performance doesn’t have much impact on the star rating. NatHERS tools assume that the overnight cooling thermostat temperature in bedrooms is the same as the daytime thermostat. At night the body is insulated from heat loss by the bed, so comfort theory would support a lower thermostat temperature in bedrooms. Lowering the overnight bedroom cooling thermostat increases predicted energy loads in bedrooms. This would ensure that bedroom performance is better valued by NatHERS tools. The rating of a traditional tropical design with well-ventilated bedrooms would be at least a star higher compared to volume market houses if the NatHERS tools used a three degree lower overnight thermostat.
In reality, it is the relationship between architect and client and their design process that NatHERS tools can’t address. 
While further research is needed into how much lower the thermostat should be, the report I prepared for the Department of Industry recommended the use of lower overnight cooling thermostats. It may not be the only solution, but it will help. I would agree with the general sentiment of Welke and Harris’ comments, though because there is a limit to what can be assessed by NatHERS tools. Even if NatHERS is modified to better reward traditional tropical design techniques, there will be some specialist tropical houses that will never receive a good rating. Houses that are essentially no more than a set of permeable screens used to enclose spaces for living will never do well under NatHERS. Predicted cooling loads from NatHERS tools will always be high in such buildings because they let too much hot and moist air in. The temperatures in these houses are easy to simulate: outdoor air temperature minus an allowance for air movement. These houses are designed to match the comfort needs of the occupants – people who, as Phil and Adrian suggested, will “get out a beer” on those 60 uncomfortable days each year.
In reality, it is the relationship between architect and client and their design process that NatHERS tools can’t address. If occupants of lightly enclosed houses never use cooling appliances, regardless of their NatHERS rating, then they are meeting the policy objectives of the regulations. There is a reasonable argument that we need a formalised alternative solution compliance path for such houses in the tropics within the National Construction Code (NCC). My only concerns would be to ensure that:
  1. This doesn’t create a loophole for volume market houses – which will be air-conditioned – to get away with lower standards.
  2. The alternative solution is suitably robust – such houses should never be allowed to be air-conditioned without bringing the fabric up to an appropriate standard, although this would be hard to enforce.
  3. The alternative solution should be rigorous – it needs to have quantifiable criteria to ensure that the design will actually deliver the comfort it promises.
  4. Occupants need to understand what level of comfort they are getting – monitoring of naturally cooled houses shows that they can spend considerable time outside the conventional comfort zone in the hottest climates3. They are not for everyone, particularly those more sensitive to heat stress in the hottest climates.
For most Australians, however, a beer is not all they need in hot weather. Over 70% of Australian houses have air-conditioning installed. In the Northern Territory, over 90% have air conditioning and half of all houses have three or more air conditioners. I’m sure that air conditioning ownership would be less if there were more Troppo houses – but it wouldn’t be 0% either. Furthermore, continued global warming will only see increased use of air conditioning, so we need a regulatory approach like NatHERS that minimises heat gain and facilitates heat loss for conventional houses in hot climates.
NatHERS tools do not simulate a sealed box, and in fact pursue the use of ventilation aggressively as a solution to comfort. As I have said, the emperor is at least wearing speedos. And maybe, in a hot climate, that is all he needs – particularly if the NCC is modified to develop an alternative solution to deal with lightly enclosed houses, a condition that NatHERS was not designed to deal with.
CSIRO recently investigated whether a higher NatHERS star rating does in fact lead to lower energy use in hundreds of real houses located in Adelaide, Melbourne and Brisbane. While heating savings were even higher than NatHERS predicted, there were virtually no cooling savings associated with higher ratings. CSIRO threw some new light on these findings at a meeting I attended recently. It seems that the way in which higher ratings were achieved across the sample was to implement design changes that had a much greater impact on reducing heating loads than cooling loads. As a result the variation in cooling energy loads predicted by NatHERS across the sample was small and it is therefore not surprising that no cooling savings were associated with higher ratings. This points to another possible deficiency with the NatHERS scheme: it adds together heating and cooling loads and assigns a rating to the total. This means that in mixed climates, which have significant heating and cooling loads, you are not guaranteed to get lower cooling energy with a higher rating. The BASIX system in NSW sets a cap for both heating and cooling. Perhaps this is the way forward for NatHERS as well.

1. Queensland Parliament, 2010.“Energy Efficiency: Queensland’s First Energy Resource”, Report on the economic and environmental potential provided by energy efficiency improvements for households, communities, industry, and government, Report No.2 of the Environment and Resources Committee, 53rd Parliament, February 2010.
2. “Tropical validation study: an investigation into the impact of energy ratings on house design in hot climates for the department of climate change and energy efficiency prepared by tony isaacs consulting, with assistance from Michael Plunkett, Smartrate, and Ray Fogolyan”, Home Star Rating Australia, Canberra, 2012.
3. Soebarto, V. et al, “The performance of award winning houses”, PLEA2006 - The 23rd Conference on Passive and Low Energy Architecture, Geneva, Switzerland, 6-8 September 2006

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Roca launches its first products as BIM objects

Roca launches its first products as BIM objectsewyt7hxeaajj9epk5qmr
  • There are now more than 50 products available in this first phase release
  • By the end of 2015, the first part of the catalogue will be available on the BIMobject® Cloud as BIM objects

Roca, the world reference company for comprehensive bathroom products, will release their full range catalogue as BIM objects, thanks to the framework agreement with BIMobject®.
Since early 2014 Roca and BIMobject have been working with this project which will run throughout 2015 and beyond with the continued publishing on the BIMobject Cloud the full range catalogue of Roca products - more than one million of articles - as BIM objects, available and downloadable for professionals. Roca’s BIM objects are available as both, Revit and ArchiCAD.
A BIM object contains information that includes all relevant data regarding properties of a specific product designed and manufactured by a company. Within the collaborative working environment of BIM technology (
Building Information Modeling), BIM objects can be downloaded from the BIMobject Cloud to integrate into any BIM software. This cooperation is to ensure that professionals in the sector have access to the most advanced tools when creating their projects. By downloading Roca’s BIM objects, planners will automatically have access to updated information. This will mean faster processes, lower risks and costs but with higher quality and a more efficient workflow.
Roca and BIMobject® signed a frame agreement last May, this reinforces the Spanish company’s commitment to help the AEC sector providing the most advanced tools to improve their work.
With this launch, Roca is the first major company in the bathroom sector firmly committed to BIM objects as a format. Today, BIM technology is accelerating in use by professionals all around the world because of the power of digital BIM collaborative work environment for the development and management of projects.
”We face this project around BIM objects as a challenge and a big opportunity at the same time. An exciting challenge because it meets our goal of trying to stay one step ahead on the market and a great opportunity to learn more about key technologies that will define the future of our industry.” says Carlos Velázquez, Corporate Marketing Director Roca Group
“Today, many people will be more than happy to get all these ROCA products as BIM objects for free. It’s been a fantastic learning process to work together with ROCA so far. People involved in this project inside ROCA have shown a high level of knowledge and understanding about what Information means in terms of BIM. More exciting content will come from the Roca and BIMobject partnership" says Mario Ortega, Managing Director of BIMobject in Spain.

About Roca:

Roca is a company specialising in the design, production and marketing of products for bathroom spaces as well as ceramic floorings and wall coverings used in architecture, construction and interior design.
Roca’s commercial network spreads over 135 countries supplied by its 77 production plants and 21.000 employees worldwide.
The wholly Spanish-owned group is market leader in Europe, Latin America, India and Russia. It is also a major market player in China and the rest of Asia, Africa and the Middle East. Roca is the worldwide leader in its business sector.

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What's a sustainable home?

What's a sustainable home?
Pinning down exactly what constitutes a ‘sustainable home’ isn't too easy - because there are so many different things to consider. When people talk about building sustainability or green building, they’re normally referring to things like:
  • the extent to which the construction of the house uses energy and which materials are used
  • its ongoing impact on the environment in which it exists
  • the house’s design, and how that affects the need for things like artificial heating, cooling and lighting and water demands
  • energy and materials required to maintain or renovate the building over the course of its life
  • the overall lifespan of the building
  • the resources required to demolish the building, and how its byproducts are either disposed of or recycled.
Embodied energy
Regardless of how they contribute to your home’s efficiency, every material and product used in the construction of your house has a different environmental cost.
Solar panels, for example, are constructed using rocks, copper, aluminium and various other materials mined from the ground, and then fabricated into silicon panels, wires, frames, nuts and bolts. Energy’s used not just to pull these things out of the ground, but also to refine them, shape them into usable parts, apply protective treatments and assemble them. The energy used to extract the materials for a product and to manufacture and transport it is known as its ‘embodied energy’.
The embodied energy in an average household, according to studies carried out by the CSIRO, is somewhere in the order of 1000GJ (gigajoules). This is roughly the equivalent of the amount of energy consumed in an average household over a period of fifteen years (although this depends very heavily on how the building's designed). There’s also an environmental cost to either disposing of or recycling the products once they’re no longer being used.
What is a life cycle assessment (LCA)?
A full assessment of the environmental impacts of a material or product used in your home (from cradle-to-grave) is known as a ‘life-cycle assessment’, or LCA. Unfortunately, achieving an accurate LCA for most parts of your home (or your home as a whole) is a difficult affair. This is partly because so many products are built using such a broad (and broadly sourced) range of materials, and also in part because sadly, it’s not often in manufacturers’ interests to reveal how much energy is involved in every aspect of a product’s life…
The lifecycle assessment approach to understanding how much embodied energy each part of your home really accounts for is the most ‘honest’ way to think about the overall environmental cost of your home. Attitudes and regulations are slowly shifting towards a stronger focus on this approach to sustainable construction, and the energy used over your house’s lifecycle accounts for a very considerable amount of a house’s overall ‘sustainability’.
Where practical and possible, you should ideally aim to build using materials that have a low level of embodied energy – and take into consideration the volumes in which different materials will be used. Walls, for example, will use a lot of any given material, while smaller fittings and fixtures are likely to have far less of an impact. Also consider whether or not different parts of your house will be able to be recycled if and when your house reaches the end of its life.
Passive design, orientation and operational energy usage
The way your home’s designed will also determine how much energy’s required to keep you comfortable – particularly in terms of the indoor climate. A well designed home will make good use of heat from the sun to warm the house when necessary (called passive heating), and adequate shading to keep the house cool when the weather’s warmer (passive cooling). The house's general orientation and which parts are faced towards the sun makes all the difference - solar access (i.e. access to sunlight) is a big deal when it comes to heating and cooling efficiency. Heating and cooling - particularly air conditioning - can be seriously energy-intensive if a house isn’t designed to make best use of natural warmth and shade.
For passive design to be truly effective, it requires a tight
building envelope and excellent insulation to ensure that the climate inside the house is separated from the climate outside.
Energy efficient appliances, plumbing fixtures and lifestyle considerations also play a big role in operational energy use, as does the size of your family, and how you plan to make use of things like compost, rain water and waste. The possibilities here are limitless – compost bins, rainwater tanks, biolytic toilets - there are a million different ways to reduce and reuse waste.
Alternative energy sources
We’re all completely addicted to electricity and the many modern toys and gadgets for which it provides life. Probably the best way to reduce your home’s ongoing impact on the environment is to generate your own electricity using sustainable energy sources like wind or solar power.
Most of the power supplied by Australia’s energy companies is generated by burning coal, which is a notorious greenhouse gas polluter. As well as being able to service your own needs, a decent solar or wind setup can also feed excess energy back into the electrical grid, helping in a small way to reduce the overall net demand for fossil fuel power. Likewise, if you’ve got a battery backup system, you can also store power to be used even when there’s no sunlight or wind.
NatHERS star ratings for efficient houses
In Australia, we have what's known as the Nationwide House Energy Rating Scheme (or NatHERS, for short). This system allows houses to be assessed for their thermal performance using computer modelling. Under the scheme, houses are given an energy efficiency star rating - the more stars a house achieves, the better the thermal performance, and in all states there are basic minimum star ratings that new houses need to achieve.
NatHERS is a great way to get a basic idea of how much energy a house will theoretically require to keep it warm in winter and cool in summer, but it's only part of the picture. For the time being, these ratings are allocated based on modelling for the design of the home. Unfortunately this doesn't always reflect how much attention's put into making sure it's properly constructed. Star ratings are a pretty good indication of a home's theoretical efficiency, but they're not always a reflection of the thermal performance of the finished product - a serious builder who genuinely understands what's intended will make all the difference. It's also worth remembering that if you're buying a house with a given star rating, you need to know how it all works!
Long term benefits
Building or buying a ‘sustainable’ home might cost a bit more in the short term, but it’s not necessarily going to break the bank. In the longer term, things like savings in operational costs, energy independence and resale value are likely to far outweigh the extra expense of building a home with sustainability in mind.
Construction (1)

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