We are often asked what are the most important considerations when building a green or natural home. Before launching into how to build with Compressed Earth Blocks (CEBs) and the benefits of doing so, we ask home builders to consider the following:
Location, Location, Location . . .
A home that is oriented to take advantage of the sun’s solar energy is one that will
be more energy efficient and naturally lighted, then one that is oriented otherwise.
Passive solar used in conjunction with thermal mass provided by materials like earth
blocks will reduce heating costs.
Simply, the bigger your home the more resources required to build it and the more
energy to heat and cool it.
Design, engineering, and construction planning play an essential role when building any structure, and are especially important when building a “green home”. For example, it is important to do the initial soil testing to determine whether the soils on hand can be used for block making, or if soils have to be brought from somewhere else when building an earth block home. CEB code
Important considerations for deciding what a structure is to be made of include:
- Where are the materials from?
- What are the materials made of?
- How are they made (ie. clearcut logging, toxic waste byproducts)?
- How much energy is required to produce and transport the materials?
- Structural and thermal properties?
- Life span of materials and whether they can be recycled, reused, composted, etc.?
- Environmental toxins (ie. off-gassing)
- Ease of application and construction?
Foundations with a footer below frost line and a stem wall built to above grade are standard. The footer must be 33 percent greater then the wall width with the stem wall centered on the footer.
Rubble or shallow foundations, which have been in use for centuries, can also be used for CEB building. The advantage of these foundations is that they save money and use less valuable resources (ie. concrete and fossil fuels) then conventional foundations. For these foundations a trench is dug, filled with gravel/stone and a perforated drain pipe, and then a reinforced grade beam the width of the wall is poured. The perimeter of the foundation trench is usually insulated vertically or horizontally, depending on the design, with rigid foam insulation. Rubble Foundation Pictures
CEB walls are stacked in typical masonry fashion with the head joints of the blocks staggered so that the blocks overlap the previous row by at least a third, with the ideal being half. Blocks can be laid either across the width of the wall or turned the other way with the block length running parallel to the wall.
Double Wall System-Thermal Mass and Insulation
For the Midwestern climate we encourage home builders to go with a double wall/cavity wall system for exterior walls. This wall is built with two courses of block running parallel to one another with a space/cavity in between for insulation. Several insulating options are available with this wall system including vegetable based foam, perlite, and sawdust/lime. In this configuration the interior blocks provides thermal mass for heat storage and conservation and the insulated cavity prevents thermal bridging and heat loss to the outside. The exterior course of blocks provides a moderating effect against cold and, even more, against heat gain in the summer.
Whole Wall System
This is simply a solid wall of earth block. It is used for interior walls and for exterior
walls when rigid insulation is added to the outside of the blocks.
Hybrid Wall Systems
One of the unique attributes to CEBs is that they can be incorporated into several hybrid wall systems that are a combination of different building materials and design. For example, CEBs can be used on the interior of a new or existing stick framed home to replace the dry wall and add thermal mass and architectural beauty. CEBs have also been used in conjunction with strawbales, with the bales providing insulation and the CEBs providing thermal mass and the strength and beauty of masonry. In this example the CEBs are placed against the strawbales on the interior.
CEB construction, unlike standard masonry, does not require portland cement based mortars or thick mortar joints (1/4-1/2"), although we have seen CEB walls built this way. Earth block builders have dry stacked walls, stuck them together with a thin slurry made from the same material as the blocks, and mixed thicker mortars of clay and sand. We have found that the slurry method works well for unstabilized blocks because it penetrates the surface of the blocks and sticks them together. However, our stabilized blocks are water resistant and stick better with a thicker mix closer in consistency to standard mortar. This mix is made with 2 parts lime to approximately 5 parts 1/8" screened mason's sand. Because earth blocks do not require thick mortar joints, walls can be built quickly by workers unskilled in masonry.
Windows and Doors
Window and door rough openings are built similar to conventional frame construction and placed in the wall according to plans. They can be secured in place with screws through the framing into to the blocks, or expanded metal lathe nailed to the outside of the frame and laid between block courses. Lintels, similar to headers in frame construction, are placed over openings to carry wall and roof loads. Lintels can be made of wood, stone, steel, or concrete.
Electrical and Plumbing
Electric wires can be run in the cavity for a double wall system; woven between courses when using a solid wall system; notched into the walls after the walls are built, and then plastered over; or run through conduit in either double wall or solid wall systems. Electric boxes for switches and outlets are placed in the wall and built around.
Plumbing, which is typically run in interior walls, can be plumbed in first and then built around, or run through an interior framed wall or chase.
A reinforced concrete or wood bond beam is built at the top of a CEB wall to tie all of the walls together, level the walls, and provide an anchor point for the roof or the next story.
Interior walls are typically plastered or left exposed with the blocks visible. Plasters with a base of clay, gypsum, or lime are all appropriate for earth blocks. Earth blocks do not generally take as much time to prep and plaster as other natural building materials. Two coats, a base and then a finish is often enough, although a third coat or color wash is also common. Color is added in the finish coat of plaster, in a wash like an alise (clay paint or lime wash), or breathable natural paints like milk paints.
Once many homeowners see the earth blocks walls, they often ask if they can leave the blocks exposed. No problem, although we do suggest a sealer or wash to eliminate dusting and lighten the color of the blocks.
Dry wall has been put up over earth blocks although this is unnecessary and an added expense. Walls can also be covered with a wainscot, crown molding, or other trim details.
A finished earth block wall can look as smooth as conventional drywall, organic and flowing with ridges and undulations like many naturally built homes, or something in between. The choice is yours. Interior Photos, Preperation for Plaster
Exterior walls are finished with a stucco or lime plaster/render. Two or three coats of plaster are the typical application systems. There are earth block houses that have been sided with cedar, vinyl, and cultured stone although these are extras and are done so for appearances. Many homeowners like the exposed block look, but we have yet to come across a sealer that stands up to the test of time. We are continuing to test new products, and this may change soon.
There are a number of variables that influence the cost of a CEB home such as site location, soil availability and composition, and architectural design. We encourage customers to contact us with their plans for an estimate specific to their project needs. We do offer bulk discounts on blocks, and discounts to customers who provide their own labor, machinery, stabilizer, etc. Below we provide some general cost information that can help guide customers in their building decisions. It is important to note that with the ever increasing cost of fuel and lumber, the CEB cost advantage is continually increasing.
Because CEBs are used entirely as a wall system, the remaining costs, which can represent 80-90% of the total cost of the home, will be the same as conventional building. For example, the cost of the roof, windows, cabinets, etc. are the same for a framed and CEB home.
Building the wall of a home typically represents 10-20% of the total cost of a home. A CEB wall will average 15% more then a conventionally built wall. In other words if the wall of a conventional home cost $15,000 for a $100,000 home, it will cost $2,250 more for a CEB wall. Over the lifetime of the home, this is a small cost when one considers the energy savings, environmental benefits, and aesthetic beauty of an Earth Block home.
Cost on a per block basis average approximately $1.20 per (7" X 14" X 4") stabilized block and $ 1.00 per unstabilized. A 1000 square foot home will need approximately 5,500 blocks. So, $6,600 or $5,500 would be the block costs of stabilized or unstabilized. Once again, we have worked with customers who have provided their own labor and tractor for loading, and have brought this cost down to $.50 to $.60/block.