Autoclaved Aerated Concrete Envelope

I built the envelope of the house from autoclaved aerated concrete. After being blocked from building with strawbales, I had to find something that fit my priorities and conditions. And the best fit was AAC. It readily meets all construction codes throughout Europe. The material itself was slightly more expensive than the local, traditional combination of brick, mortar and reinforced concrete. But when the AAC system as a whole is compared to that of the local, traditional construction methods as a whole, then the total material costs are fairly close. Significantly, the AAC house systems and the material are easy to work with - requiring little extra expertise than those of a typical masonry worker, are flexible, and are quick to build, making it possible for me to build the house myself with some help from my wife and brothers. This enabled me to fulfill a dream of building my own house with my own hands. Furthermore, it allowed me to save a great deal of money since the norm is that well over 50% of the construction costs of a typical house are labor costs.

It is easy to build with because the AAC material is simple to work (it is easier than wood to cut, sand, chisel, drill, shape, etc.); the blocks are large but lightweight and easy to lift and handle; the blocks are a breeze to build into walls (because they are built to precise dimensions, have adjoining crevices and ridges on the vertical surfaces, and are joined together horizontally in ultrathin 1mm joints using special 'cement glue' that is applied with specific and easy to use tools); and the floor and ceiling/roof panels are easy to put in place (a small construction materials transport truck uses its mechanical arm to lift - with a special attachment - and place these long, thick, narrow steel-rebar-reinforced AAC panels onto the supporting walls, which is very fast and requires little effort). Furthermore, all these things make it fast to build. It is also quick to build because it is an all in one material - it is a durable, high load-bearing material (because it is a 'solid' material made of 'concrete'); it provides high thermal and acoustic insulation (because the material encloses innumerable air 'bubbles'); and it is completely inflammable and fireproof (because it is composed of the inert, non-organic materials of sand, lime and cement). The AAC walls, ceilings and floors also make secondary work relatively fast and easy because of the ease of working the AAC and because the surfaces of the walls, floors and ceilings are so flat and smooth.

An AAC house is safe and healthy to live in for a number of reasons. It is safe because the material is strong, durable and dependable. The house is completely fireproof - it is inflammable and does not offgas due to extreme, prolonged heat. The effects of freeze/thaw cycles on AAC walls is negligible since abundant rains can not get a sufficient proportion of moisture deep into the wall when the walls are left bare (walls are almost always finished off with a decorative, protectice layer such as stucco so this makes freeze/thaw cycles even more inconsequential). The sun has no impact on AAC. It can survive extreme weather and environmental phenomena. Forest fires, as mentioned, do nothing to the AAC. Flooding will not have a serious impact on the AAC structure. It can withstand high winds due to its relatively high weight. And AAC homes can be built with special corner and window/door blocks that are filled with reinforced concrete for earthquake prone areas. Since AAC is a tough inert, non-organic material, pests can neither eat the material nor make nests in it nor will microorganisms lead it to rot, ensuring the material's structural integrity and its durability; this also keeps the interior healthy by eliminating prejudicial animals, insects and microorganisms. The AAC helps maintain indoor air quality by regulating moisture; the AAC acts as 'thermal mass' for humidity, absorbing some from indoor air when there is excess and releasing some when it is deficient. Moreover, since the AAC is a 'breatheable' material, any water vapor that manages to penetrate its interior can find its way to the exterior, futher helping maintain adequate interior humidity levels. And because the AAC walls do not display capillary action upon the wet ground, the interior of the walls are further aided in remaining dry. The AAC is also non-toxic and non-gassing so that physical human contact is completely benign and the air does not get contaminated. And the good sound insulation helps keep out stressful exterior noise.

Finally, AAC has a large number of qualities that make it 'green'. An AAC house envelope establishes good thermal insulation because the material itself has good thermal resistance, the homogenous nature of the construction helps eliminate themal bridges, and the thermal lag characteristics help attenuate outdoor temperature changes. Good insulation levels are necessary to help keep the house warm in winter and cool in summer by eliminating losses of heat or cool; this energy efficiency leads to considerably lower yearly energy usage since home heating and cooling are usually the two biggest energy requirements of a house . AAC also has moderate thermal mass characteristics that help to palliate internal temperature changes, which is highly advantageous in a passive solar house. An AAC house will last many, many generations without need for significant maintenance or renovations. By using a long-life CFL bulb one displaces use of a large number of less energy-efficient incandescents over the same time period; the same applies to AAC homes with their very long lifespans and high energy-efficiency. Both material and energy resources are saved over the lifespan of an AAC house in comparison with other more conventional and less energy-efficient housing alternatives. AAC housing systems can result in very little construction waste and this waste can be used, for example, on site for foundation perimeter drainage trench filling since the material is completely inert and neither damages the soil nor groundwater. Furthermore, the material is recyclable. In comparison with traditional concrete, the embodied energy per unit of volume of AAC is only about a third; even in relation to wood housing, a material generally regarded as having low-embodied energy, the AAC compares favorably depending on what type of wood is used and the processes and treatments performed on the wood. While AAC is not made from a renewable resource, like wood, it uses materials (sand, lime, cement) which are in extreme abundance throughout the planet. Ideally, in this regard, one should use a construction material that is both renewable and extremely abundant. Strawbales fit this qualification nicely. Unfortunately, wood in most cases does not - it is renewable but demand for wood preposterously outstrips sustainable harvesting, contributing to continued global deforestation. In relation to the local, traditional construction systems, AAC's all-in-one nature and its light weight make for more energy-efficient transport. Unfortunately, one environmental drawback I had was needing to ship the material from central France to central Spain. Ideally, the closer the construction material is produced to its point of final use, the better as less fossil-fuel will be consumed for transport.