Does Eco Building Decrease Energy Consumption? May 30, 2008
Posted by Lizanne in : Community, Energy , trackback
The global environmental crisis is forcing us to take a long, hard look at our use of energy. Most of us have been guilty of firing away, using and abusing electricity and water without a second thought about it. But this kind of behaviour is simply impossible in a new era where environmental awareness and sustainability ranks among the top issues of our time.
In examining my own life, I realized that energy saving bulbs and solar powered water heating is certainly contributing to the international effort to get our act together. Still, with our terribly hot summers and icy cold winters in the Ceres Valley in South Africa, our use of energy to cool or heat our homes, simply transcends my minor efforts to act eco-conscious. And I suspect this is also felt in many places around the world. So at the beginning of a building process for a new eco mountain cottage on our farm, what can I do to lessen the need to cool or heat that home? Will the benefits to the people that will live there, add up to the benefits for the environment? With these questions on my mind, I set out on my eco search. You will see that my answers are not exclusive to any one area or climate.
During my search I came upon two alternative building methods that seem to be gaining trustworthiness in the building sector. The one is “Straw Bale Building” and the other is “Sandbag and Timber Pole Building”. Both appealed to me because they claim to reduce heating costs by up to 75% through natural insulation. Although I had initial doubts concerning a wolf blowing a straw and stick house to pieces, I must say I am certainly taking a hard look at using one of these two for the upcoming project. This article will look at Straw Bale Building and the next one will look at Sandbag and Timber Pole Building.
Straw Bale Building:
This method uses tighlty stacked straw bales as large “bricks” to build just about anything. All aspects of building remain the same as we have become familiar with in the 20th century (like plumbing, eletrics, roofing, etc.). The main difference would be found in the design of foundations, the type of wall building material, and the type of render/plaster. The straw bales are stacked on top of each other like bricks, with holes left open for windows. It is then covered with chicken wire and plastered for an even finish. Because it is usually not good to mix materials, gypsum plasters is not always a good idea when brick and cement isn’t used, but instead natural clay or traditional lime plasters are recommended.
The main pro’s about this building method is that it is a) energy efficient, b) cost effective and c) is easy to build. It is claimed that a straw bale building will reduce heating costs by 75% because of the great insulation of the thick straw walls. It will also cost you R140 000 (?10 000 / $20 000) less if used to replace brick and block for a normal 3 bedroom house. And ease of building is proved by the fact that people with no previous skills/experience can participate in the straightforward design and construction, which again saves on labour costs.
Its super and affordable insulation qualities can be explained via the next formula: the K value of straw in a strawbale is 0,09 W/mK. This, combined with walls typically over 450mm thick, gives a U value of 0,13W/m²K – which is two or three times lower than contemporary materials. This also extends to create a fantastic sound insulation barrier (two recording studios in the USA were actually built of strawbales for their sound proofing quality).
In looking deeper at the energy efficiency of straw bale building, it seems that over 50% of all greenhouse gases are produced by the construction industry and transportation associated with it. Straw, however, takes carbon dioxide and turns it into oxygen during its life cycle. Coupled with vastly reduced heating requirements, thereby further reducing carbon dioxide emisssion (greenhouse gas) from the burning of fossil fuels, strawbale building can actually cause a net decrease in greenhouse emissions. Straw is also an annually renewable natural product, grown by photosynthesis, fuelled from the sun. It means less pressure to use other more environmentally damaging materials.
But the advantages doesn’t stop at energy efficiency and low costs. The ambiance in a straw bale house is cosy, calm and peaceful. This is partly to do with the high level of sound insulation, partly to do with the air quality, and partly with the organic feel – a beautiful nurturing and safe environment to inhabit.
There is also a growing body of knowledge on the harmful effects of living longterm with modern materials that give off minute but significant amounts of toxins, the so-called “sick building syndrome”. Living in a straw bale house protects you from all that. It is a natural, breathable material with no harmful effects.
With all of these positives I am almost convinced to use this method. Two questions I have however, is whether the plaster wouldn’t crack quite a lot with such a seemingly non-solid material, and secondly, will such a building last through decades of heavy rain, wind and climate hammering?
If there are knowledgeable people around who would like to convince me, I am quite eager to be told of long lasting success stories.
Lizanne Malherbe holds an MA degree in Environmental Ethics at Stellenbosch University, South Africa.
She is currently pursuing a PhD in Environmental Design.
Comments»
what about special glassing to lessen or increase the effect of the sun, would that have some effect during daytime? I’m just curious.
Actually South Africa is a bit behind Europe as far as I know. In Europe they use double glazing to keep houses more energy efficient, while in South Africa we don’t. It might be because we don’t have such extreme weather (going far below 0 degrees Celcius ).
Yes that seems like a valid point to consider. What I’ve seen here in South Africa at a cob house, was that they used old windscreens (collected from a scrap yard) as windows. This seems like a very very clever way to reuse second hand materials, PLUS get your windows virtually for free. Ventilation is then controlled with holes in the walls at specifically placed high and low spots.
Regarding heating and cooling a building, it seems the most important things one can do are:
1. orient the building so that living areas face north for winter sun into the house (combine with thermal mass so that a mass inside the building is warmed by the sun and holds the heat through the night)
2. have overhangs or deciduous trees/vines on the north side so that living areas are in shade in summer
What you are referring to in comparing the ecological construction methods with mainstream methods is that the former contain less “embodied energy”
More nifty techniques that they’re using at the Sustainability Institute:
1. a rock bed below the floor: in summer they let cool air into the rock bed at night and during the day let it flow out of vents in the floor; in winter they pump warm air from the ceiling cavity into the bed and release the stored warm air through the vents during the day
2. Apparently 1-2 m down in the ground the temperature anywhere on earth is a constant 21C. So you run pipes containing water (?) through this layer and then up into your floors. So it tends to keep the floors at a constant temperature. I think they call it a geothermal heat pump.
You can often find good advice from locals. Their methods have been tried and tested over many centuries, if not millenia. I think specifically of the claybrick houses that still stand along the West Coast of South Africa, not too far from Ceres. The method is enjoying a revival, and you will find examples by visiting the Duinepos chalets in the West Coast National Park. So if you have any clay on or near your farm it might be worth investigating.
Get the book “Building with awareness” - the construction of a hybrid home DVD & guidebook by Ted Owens. It will answer all your questions.
In answer to the question: “Does eco building decrease energy consumtion”. The short answer is NO. The long answer is do your homework - no matter what you do, you consume energy and if you already have a home, are you going to break it down when you have built your eco house, or will some body else move in and continue burning up energy? Will you ever recover, in your lifetime, the energy you put into building your eco house? Can you show me a factory producing solar voltaic panels that derives it’s own energy from solar voltaic panels? So straw bales consume carbon dioxide, but how much diesel fumes were produced plowing the land, havesting, baling and transporting them? You need to take a global holistic view.
Yes, you’re right Terry. The energy that goes into being energy efficient is often not worth it. That’s why I like the claybrick houses idea. The bricks are sun-dried and made in old ice-cream tub moulds. The sense of creativity that it gives to otherwise unemployed people is something to behold. A good thing all round, provided the source of the clay is nearby.
Dear Lizanne and All,
I manufacture roof tiles out of recycled plastic and sand.
I am working with Eco-build (sandbag homes) and Imison (EPS - Expanded Polystyrene Homes) for contracts in 5 countries, excluding South Africa.
They are 2 builsing methodologies that are working right now. I personally agree that the straw homes are the best insulators of the lot, but the community involvement in sand-bag homes is truly wonderful and the speed at which both sets of homes can be erected, allows us to take on contracts for 1M homes in 5 years without even flinching. Hope this helps…