| Embodied energy is the energy required to extract, | | | | buildings. The straw bales are laid on a bed of stone |
| transport, process, install, and dispose of, or recycle | | | | so they will not retain moisture. A cement screed is |
| the materials that make up the building. | | | | cast in the bottom of the trenches on the conc. |
| For this study, the total embodied energy was not | | | | footing to be sure that any water that might find its |
| used to compare the two construction types, only | | | | way into the trench would be directed away through |
| the energy for the material manufacture was used, | | | | the weep holes on the sides. These are the only |
| because energies used to transport, install etc. would | | | | bricks used in the strawbale dwelling, thus embodied |
| in most instances be the same for both construction | | | | energy values for mortar and bricks are a lot less for |
| types and cancel each other out, and because almost | | | | this type of construction. The foundations for |
| 70% of the total energy invested in a building's | | | | strawbale buildings are shallower (200mm deep), thus |
| construction (Embodied energy) is embodied in the | | | | less conc. Is used as well. |
| materials themselves, one can compile a rather | | | | The last main difference is, of course, the wall |
| accurate comparison with using just the energy used | | | | material which differs hugely in the amount of |
| for the material manufacture alone, however, when | | | | embodied energy to produce & install them. |
| referred to the energy used to manufacture the | | | | Embodied energy for straw bales is 31MJ/m3 |
| materials I will refer to the "Embodied energy". | | | | compared to the 5200MJ/m3 of stock bricks, thus |
| Materials which will be more or less the same in | | | | because the walls have the greatest material volume |
| quantity / volume eg. ceiling boards, cornices, | | | | of all the building components, it is understandable |
| skirtings, floor slab & finishes, because of the | | | | that the strawbale dwelling will have a much lower |
| same floor area, have been omitted for they will | | | | total embodied energy value than it's rival as is |
| have no impact on the embodied energy outcome. | | | | indicated below. |
| Construction | | | | Conclusion |
| To compare the two types of construction, I started | | | | Straw is a viable building alternative, plentiful and |
| with a 12000mm x 6000mm brick building and included | | | | inexpensive. Straw-bale buildings boast super-insulated |
| 2 bedrooms, a bathroom, open plan kitchen & | | | | walls simple construction, low costs, and the |
| living and a garage. To justify the comparison, I | | | | conversion of an agricultural byproduct into a valued |
| designed the strawbale dwelling with the same rooms | | | | building material. Properly constructed and maintained, |
| and exactly the same floor area for each room, but | | | | the straw-bale walls, plaster exterior and interior |
| because of the bales' rather wide (approx. 480mm) | | | | remain water proof, fire resistant, and pest free. |
| module width I ended up with a 13200mm x 7250mm | | | | Because only limited skill is required, a community |
| external envelope for the straw bale dwelling. This | | | | house-raising effort can build most of a straw-bale |
| made quite a difference on the material volume of | | | | house in a single day. This effort yields a low-cost, |
| the roof and roof trusses. Both the dwellings' | | | | elegant, and energy-efficient living space for the |
| received one plaster coat, but vary in thickness. | | | | owners, a graceful addition to the community, and a |
| Conventional brick wall plaster width vary from apprx. | | | | desirable boost to local farm income. I think, especially |
| 12mm - 18mm, compared to the 30mm plaster coat | | | | in this country, residential straw bale buildings could be |
| for strawbale walls because of the greater surface | | | | a very sustainable viable alternative to residential |
| un-evenness among other reasons. | | | | architecture. |
| The foundation details differs from conventional brick | | | | |