In the last post we examined the elegances of Bilbo's earth sheltered dwelling as described in The Hobbit. Careful construction and design can yield a home requiring little energy for comfort, snug and dry and spacious inside. Twelve dwarves, Gandalf and Bilbo could gather in the dining room to feast on Bilbo's pantry without feeling cramped. Then they had a jam session and stayed up all night plotting Smaug's demise and the division of an uncountable treasure. All carried out underground.
Living underground is not always so nice. Later in the story the travellers are waylaid by three trolls, and in due course the trolls' cave is described. Not a nice place. Smelly, with stuff scattered about. Later, the group visit a goblin cave. Likewise, not a nice place. Wet, dark, confusing, windowless. That's the dark side of earth sheltered living. So take care: while you're being wooed by the fabulous energy profile of earth sheltered living, be warned about the several things that can go wrong.
Be aware that the concept of earth sheltered building does not rest on the insulating properties of dirt. The guiding principle, instead, is the thermal mass of the concrete membrane and the earth resting on it, enhanced often these days with layers of rigid foam board. The goal is to create a well-insulated envelope much like that of a conventional frame structure, but with a huge thermal mass on the inside of the insulation as well as on the outside.
Another unwritten but understood factor in American earth sheltered living is the electric heat added to the space by lighting and appliances. Without this incidental, or "internal" gain, the temperature of an earth sheltered dwelling would come to rest somewhere in the 50s. Call me a wuss, but I like to hunker down at home in less than a parka. And, notwithstanding the somewhat cheeky boast of earth sheltered builders that no hvac system is needed in their homes, most earth sheltered buildings feature a heat pump, furnace or stove to provide comfort as it's needed.
Moisture, the bane of many an otherwise well built house, will kill an earth sheltered home. A perfect membrane is important for sealing the concrete against moisture, protecting the insulation and keeping the earth mass dry, . The low air change rate in a concrete, foam and earth envelope can result in a humid, moldy cave, the kind only trolls would want to live in. Forced ventilation through heat-recovery vent systems is an excellent idea. Meticulous construction featuring approved and inspected membranes and a drainage network is also fundamental to success in below-ground living.
One advantage modern earth sheltered builders have over Bilbo's hobbit craftsmen is the technology that makes warmth, light, and air movement so much easier to design into a home. Skill with stone and wood will get you so far toward elegant American living, but without skylights, light wells, modern HVAC, kitchen equipment and tons of hot water, the idea of living in a well-designed cave would not appeal to most people. As it is, earth sheltered living is growing on us as a society, slowly. But that's the pace of change in the American building industry. Slow. And cautious. I think I like it that way.
Living underground is not always so nice. Later in the story the travellers are waylaid by three trolls, and in due course the trolls' cave is described. Not a nice place. Smelly, with stuff scattered about. Later, the group visit a goblin cave. Likewise, not a nice place. Wet, dark, confusing, windowless. That's the dark side of earth sheltered living. So take care: while you're being wooed by the fabulous energy profile of earth sheltered living, be warned about the several things that can go wrong.
Be aware that the concept of earth sheltered building does not rest on the insulating properties of dirt. The guiding principle, instead, is the thermal mass of the concrete membrane and the earth resting on it, enhanced often these days with layers of rigid foam board. The goal is to create a well-insulated envelope much like that of a conventional frame structure, but with a huge thermal mass on the inside of the insulation as well as on the outside.
Another unwritten but understood factor in American earth sheltered living is the electric heat added to the space by lighting and appliances. Without this incidental, or "internal" gain, the temperature of an earth sheltered dwelling would come to rest somewhere in the 50s. Call me a wuss, but I like to hunker down at home in less than a parka. And, notwithstanding the somewhat cheeky boast of earth sheltered builders that no hvac system is needed in their homes, most earth sheltered buildings feature a heat pump, furnace or stove to provide comfort as it's needed.
Moisture, the bane of many an otherwise well built house, will kill an earth sheltered home. A perfect membrane is important for sealing the concrete against moisture, protecting the insulation and keeping the earth mass dry, . The low air change rate in a concrete, foam and earth envelope can result in a humid, moldy cave, the kind only trolls would want to live in. Forced ventilation through heat-recovery vent systems is an excellent idea. Meticulous construction featuring approved and inspected membranes and a drainage network is also fundamental to success in below-ground living.
One advantage modern earth sheltered builders have over Bilbo's hobbit craftsmen is the technology that makes warmth, light, and air movement so much easier to design into a home. Skill with stone and wood will get you so far toward elegant American living, but without skylights, light wells, modern HVAC, kitchen equipment and tons of hot water, the idea of living in a well-designed cave would not appeal to most people. As it is, earth sheltered living is growing on us as a society, slowly. But that's the pace of change in the American building industry. Slow. And cautious. I think I like it that way.
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