It is probably about time that we started looking at strawbale building as a design medium as well as a building medium. All building materials and methods have their own innate design strengths and weaknesses. The type of material used will dictate up to a point how it can be used structurally. This then sets the limits of its design capabilities. To force a material to perform a function that it is not capable of is to design a building that will not work. This not only applies to the structural aspect of things, but also to the character of the building in question. A building material can be made to look as though it is performing an impossible task, but that actually detracts from its appearance as common sense tells the observer that what they are seeing isn't real. So how does all of this apply to strawbale? There are two aspects to this question which are bound to upset the status quo.
Strawbale design has two paths that it can follow. As an infill or veneer method it follows the dictates of the materials used to create the framework in which it resides. As a result the structural characteristics of strawbale are irrelevant. Apart from its thermal properties no advantage is taken of its inherent structural capabilities. In fact the situation backfires when the time taken to render is considered, which casts it into a less than flattering light when compared to other infill options. In fact I would go so far as rejecting the term "infill" and replace it with the more accurate "strawbale veneer". Let's face it, the main definition of a building is the structure that holds the roof up. Thus in Perth a "brick" house indicates a double-brick load-bearing wall, where as "brick veneer" indicates anything but. The same applies to strawbale. A strawbale house is load-bearing strawbale structure. Anything else is just anything else with a veneer, be it strawbale or whatever. The wall cladding does not determine the type of building per se.
If strawbale is used as a load bearing medium, then it does have certain design limitations. The wall height is limited to seven or eight bales, ie. 2.5m to almost 3m. In a one and a half storey or loft application an extra two or three bale height could be added to the already tensioned wall and then tied down, but that is about as far as it goes. So there is a limit in height. There is also a limit in wall length. Six metres is regarded as about as far as a wall can go without some kind of structural support, be it a buttress, another intersecting wall or a ninety degree change of direction. A load bearing strawbale wall also loses its integrity when openings of more than 50% of the wall area are inserted. So the building material does have its design limitations.
Is there a problem with this? Of course not. Brickwork will not span a six foot gap - it needs a lintel or to be arched. The same can be said for concrete and stone. Steel wire cables cannot stand up on their own, but they work particularly well at bridging gaps in suspension. Steel beams will bridge a greater gap than timber but you can't then just bang a nail into them. All building materials have their limitations, but when they are allowed to perform in the field that they are suited to then they are an exercise in functional beauty. So how does this apply to strawbale? Quite simply. Strawbale has its limits, but once they are identified and taken into account they become design strengths.
Strawbale lends itself to the adage that small is beautiful. By building in loadbearing strawbale you have to look at needs as compared to wants. By specifying a design in strawbale that can't actually be built in that medium without other structural props, you have not only insulted the integrity of the building material but you have also not looked at what that building material can teach you. This is where my concept of building starts to ruffle feathers, and I suspect that the two aspects that I am about to address will really get the feathers flying. The first concerns the size of buildings and thus the consumption of materials, and the second is the problems of passive solar design and how they relate to strawbale.
Unfortunately the two problems are interwoven, so one can't address one without addressing the other. As long as people keep insisting on huge open-plan designs with acres of glass to the north and stereotypical plans for thermal mass and greenhouses to the north, not to mention recycling of secondhand materials, then loadbearing strawbale will always be pushing the proverbial uphill. So we may as well start with the solar aspects of strawbale as that also influences its structure.
One of the curiosities of climates that are very cold is that they build buildings with very thick walls and small windows. But one of the curiosities of climates that are very hot is that they build buildings with very thick walls and small windows. So what's the difference? Nothing. They are both using the principle of insulation, except one is keeping the heat in, and the other is keeping the heat out. Strawbale has huge insulative properties which can be used to advantage if one plans a house with that in mind. For some reason everyone gets their knickers in a twist at the supposed savagery of winter. This is Western Australia for crying out loud. It doesn't get that cold in Perth, although it can get somewhat chilly in other parts of the state. And winter doesn't last that long - not like the long stretches of hot weather that can be endured over the summer months. Thermal mass - for when? If house design takes into account the insulative properties of strawbales, with small scale design, steering away from huge windows and making use of verandahs and courtyards, then winter heating consists of little more than normal use of the kitchen.
The problem seems a combination of unreal expectations and of people wanting their cake and eating it too. As a designer, I am often approached by people who are interested in building in strawbale, but then rattle off a list of requirements that run counter to not only the constraints of that medium, but also defy the concepts of environmental restraint. It seems to be the attitude today that a family of three couldn't possibly live in a house smaller than 150m2. The northern side of the house must be as much glass as possible, pergolas are essential, and that adults need to be separate from their children. The emphasis is on recycled materials, particularly timber, and the use of natural materials. To assuage their environmental conscience, they can justify using three houses worth of recycled floorboards to build their Taj Mahal, yet not think of it as looting a finite and rapidly depleting resource. Recycled materials, particularly floorboards are already becoming a scarce commodity in Perth. Salvage yards are now moving into the era of the late sixties and into the seventies, where concrete slabs and associated flooring materials are now the norm. Not much there to recycle. Whilst CALM loots the forests, baby boomers are looting the salvage yards.
This leads all too often to the situation where if a house of alternative construction can be built for say half the cost of a similar sized conventional house, it won't be. The size will be doubled so that twice the house is gained for the same amount of money. Sounds like a bargain? Not really. Environmentally and socially there is a high price to pay.
The achilles heel of strawbale is precisely this dilemma. As a building material it encourages owner involvement in building and construction. It is an empowering medium that allows almost anyone to create their own home. As a medium for design though, it collides head on with the contradictions of "conventional" solar design, perceptions of space and the light footprint. People who think of themselves as environmentally aware and wish to build sensitively are often the first to fall into the trap of believing popular dogma and establishing selfish expectations. One of the reasons I suspect that load bearing strawbale building may struggle for acceptance is because it is an uncompromising form of building, and challenges the lip service so often spouted in the place of real and serious belief.
As to the aspects of solar design, some things need to be challenged. I have had people explain to me how they wish to design a mud brick wall inside their strawbale house for thermal mass, describe fancy pergolas, quote reams of figures about the angle of the sun at whatever time of year and wax lyrical about the magical properties of Feng Shui.
Thermal mass in a building as well insulated as a strawbale house is an unneccessary complication and expense. Remember, we are trying to design for a summer climate here. The short winters will be handled by simply living in the house. As for pergolas, invariably they don't supply the shade you need in summer and I have yet to stand under one in the rain and not get wet. I find it hard to believe that people would go to the effort and expense of roofing an area in such a way that it doesn't keep the rain out. What ever happened to the joys of sitting on the verandah, listening to the sound of the rain and smelling the freshness of newly dampened soil. Oh I forgot - I should be sitting inside my designer house and watching all of this through the large feature windows. Like it's on telly! So much for being in harmony with nature.
So we now come to the issue of light. This is not to be confused with thermal characteristics. Sun angles and verandah depths don't play much of a role here. Light can be introduced into a building in all sorts of ways. Skylights, dormer windows, clear roofing on the verandah over windows and cloistery windows are just some of tricks that can be used. Plenty of light can be let in without sacrificing the insulation advantages of strawbale. As for incorporating foreign superstitions into building design, I would rather rely on common sense. But we might leave that one well alone!
Over and above all of this though, is the excessive emphasis we put on building. Personally I think it is all a bit over rated. Our society places such a huge importance on home ownership, to the extent that most of us work with the main motive of paying our home off before we retire. A symbol of achievement, and an excellent way of keeping a large part of society distracted and docile. The perfect example of disempowerment that gives rise to a whole class of "experts" who plan, design, approve and construct. In most other societies around the world it works in reverse. Building is not a specialized science but a communal glue. Building skills are known to all, and all can be involved. A house is built and then what is done for the rest of life is something else again. Unlike our society, the owning of a home is the beginning of a working life, not the end result of enslavement to an inequitable economic system. But that is whole different subject in itself.
So designing and building in strawbale does require some changes in attitudes and lifestyles. It not only encourages a small scale and thrifty approach to building, it positively demands it. To design in loadbearing strawbale is to set limits in material consumption and to define what you really need in life. I suspect that if it, as a medium, leaves you wanting more than it can deliver, then I would suggest that questions not be asked of its suitability, but of your wants. You may be surprised.