earth-sheltered construction

Earth Sheltered Construction: A building type in which part of, or the entirety of the building, is covered by, or submerged into the earth.

Bermed and Underground

In bermed construction, the structure is built above grade or partially below grade in such a way that one or more of the walls are covered by the earth. Generally, bermed construction is done in an "elevational" design. Elevational design involves leaving just one face of the building exposed (typically the south face) while the rest of the faces -- including the roof in most cases -- are covered. In this format, the exposed face is largely glazed to allow for heat and light from the sun into the building. Typically, rooms that programmatically demand natural light (bedrooms, common areas, etc.) will be placed on this side of the building so as to benefit from the natural light and heat gain. Storage rooms, bathrooms, and the like would be placed on the opposite side as they have less demand for natural light -- though, skylights can be used to bring sunlight in should it be desired.

In underground construction, the structure is built entirely below grade. Usually these buildings feature a courtyard or atrium at the center to allow for natural light in all adjacent spaces as well as provide an open feeling despite being underground. A benefit of this type of design is that it creates a private outdoor space that is well protected from the wind. It's most ideal for sites lacking in views, dense developments, and/or sites with lots of noise in the area. A drawback of this type of design is that it tends to limit the amount of passive solar gain that can be achieved due to the positioning of the windows. Careful consideration should be taken for drainage and snow removal in the courtyard as well.

• protection from the elements (strong winds, hailstorms, natural disasters, etc.)
• natural thermal regulation due to the relatively unchanging ground temperatures
• less outside maintenance
• increased longevity of roofs (assuming the roof is covered) and walls
• a more harmonious relationship with the surrounding landscape
• energy costs are lower in the long-term
• reduced building footprint
• preservation of green-space and biodiversity

• initial cost of construction is higher (20% on average)
• higher attention to detail needed in construction to counteract the potential moisture problems
• higher level of care needed regarding soil considerations
• not suitable to all climates (climates with high humidity and relatively small temperature swings aren't ideal)
• materials aren't usually the most environmentally friendly (reinforced concrete is generally the standard for earth sheltered construction as it is well suited to withstand the weight of the soil and is relatively easy to waterproof)

Built in 2020, this home on the Mediterranean is recessed into the hillside, making it classifiable as bermed construction using the elevational method.

The temperature ranges from about 53 degrees to about 78 degrees on average and the humidity hovers rights around 70% year round. Thus, this building isn't necessarily benefitting much from the thermal regulation that the ground provides. However, by recessing the home into the hillside, it receives shelter from the strong northerly winds.

The main purposes for building into the hill are, again, protection from the strong northerly winds, as well as access to the "disarming views" and a desire to blend with the landscape. This building is a stellar example of how earth-sheltered design can still very effectively maintain an open/airy feel and provide ample access to natural light and views. The following is from MOLD architects:

Longitudinal walls of dry stone outline and protect the interior and exterior spaces. They consist the vertical borders, which lead the visitor’s gaze to the horizon line. In contrast to the sturdy stone walls, the transverse facades are light, made of glass and can open along their entire length. The front is fully open to the east view, while the rear windows frame indoor gardens, enhancing the air flow and letting light into the residence. Lighting and ventilation with front and rear openings, stone, a planted flat roof, suitable insulation, as well as energy-efficient glass panels adds to NCAVED excellent bioclimatic features.

Stone, exposed concrete, wood and metal are used with precision to create coarse inner shells. Perforated filters on the facades and the floor produce shadow patterns. Paired with large reflective mirror surfaces, they make up an eerie atmosphere in the private areas of the residence. Finally, the pergolas seem to float detached from the surface, denoting the physical aspect of the residence, which integrates to the landscape, yet maintains a dynamic presence.

Because it embraces the sloping nature of the hillside even its structural layout, the vast majority of the home has direct access to natural light. This applies even to its backside (uphill) where gardens, open to the sky above, are recessed down into the hill at floor level with large glass facades that open onto the gardens.

The CEGE Building was finished in 1983 and designed by David Bennett. The submersion into the ground is both a kind of tribute to the mining industry from which the civil engineering department finds its origins, and a functional design decision. Bennett wanted to the building to be energy efficient, with a relatively small footprint and aimed to attain lower cooling and heating costs. He later wrote on the subject:

During the late 20th Century it became evident that human activity has the capacity to alter the natural history of the world, destabilizing the global climate and poisoning the natural environment,” he wrote later. “Setting these indisputable facts against the complex pattern of political, economic, cultural, intellectual, artistic, religious and physical human activity and the tendency toward inertia throughout human history, vested interest and institutional memory, it is impossible to predict with any certainty the impact of these phenomena on the future. But some new directions have to be tried.

The earth sheltered design of the CEGE building was a trial of one of those new directions.

The CEGE building is in Minnesota, where temperature averages range from 8 degrees to 83 degrees over the course of the year. Thus, the earth sheltered design is well suited to benefit from the inherent thermal regulation that the earth provides.

While the building still has a fairly big surface footprint, it would be one of the tallest buildings in the portion of campus it resides if it weren't underground. Or, if it weren't seven stories, it would sprawl out to a significantly greater footprint than it now possesses.

The building allows for the preservation of green space over much of its footprint as can be seen in the courtyard photo above.

One of the key design features is the cupola which houses a solar optical system. The intent of this feature is to bring daylight down to the underground floors of the building using a system of mirrors and lenses. Unfortunately, either because it was too complex of a system, or because of cost cuts early on, the daylighting system isn't all that effective.

In these two examples, it's apparent that earth sheltered construction can be utilized in a variety of climatic conditions for a variety of intents. Two of the biggest benefits are thermal regulation (where applicable) and preservation of green space. While the cost is often higher up front, the savings over the lifespan of the building often offset those costs, and the benefit of maintaining or even creating new green space, while not monetary, is another reason to foot the higher bill. In some cases, even though thermal regulation isn't a concern, other climatic or contextual concerns such as shelter from wind, creation of privacy, or a desire to blend with the landscape can lead to an earth sheltered design being a potential solution.