How to Build an Earth Sheltered House?
Building an earth-sheltered house is a challenging yet rewarding endeavor, offering significant advantages in energy efficiency, temperature stability, and environmental integration. It requires meticulous planning, understanding of structural engineering, and careful attention to waterproofing and drainage.
Understanding Earth Sheltered Housing
Earth-sheltered homes, also known as underground homes or bermed homes, are structures built with earth against their walls, or completely underground. This design harnesses the earth’s thermal mass, providing insulation that regulates temperature and reduces energy consumption for heating and cooling. Beyond energy efficiency, earth sheltering offers soundproofing benefits, protects against extreme weather events, and blends harmoniously with the natural landscape. However, it also presents unique engineering and construction challenges that must be carefully addressed.
Types of Earth Sheltered Designs
Several common designs exist, each with its own advantages and disadvantages:
- Bermed: Walls are built above ground and then backfilled with earth on one or more sides. This is often the easiest and most cost-effective type to construct.
- In-Hill (Elevational): The house is built into a slope, with the roof and one wall exposed. This design allows for natural light and ventilation while taking advantage of the earth’s insulation.
- Underground (Chambered): The entire structure is buried underground, typically with a courtyard or atrium to provide light and ventilation. This offers the greatest temperature stability and protection but is also the most complex and expensive to build.
- Cut-and-Cover: A trench is excavated, the house is built within it, and then the trench is backfilled. This method offers flexibility in design but requires significant excavation.
Key Considerations Before You Begin
Before embarking on this project, several crucial factors need careful consideration:
- Site Selection: The soil composition, slope, water table, and sunlight exposure all significantly impact the feasibility and design of your earth-sheltered home.
- Structural Engineering: Proper structural design is paramount to withstand the immense pressure of the earth. Consultation with a qualified structural engineer is essential.
- Waterproofing: Preventing water infiltration is critical to maintaining the integrity of the structure and the health of its occupants.
- Ventilation and Lighting: Ensuring adequate natural light and ventilation is vital for comfort and indoor air quality.
The Construction Process: A Step-by-Step Guide
Building an earth-sheltered house is a multi-stage process that requires careful planning and execution.
1. Site Analysis and Design
This stage involves thoroughly assessing the site’s geological and hydrological conditions. Soil testing is crucial to determine its bearing capacity and drainage characteristics. The design should be tailored to the site’s specific conditions, considering factors like sunlight exposure, prevailing winds, and local building codes.
2. Excavation and Foundation
Excavation is a significant part of the process, requiring heavy machinery and careful planning. The foundation must be exceptionally strong and well-drained to support the structure and withstand the earth’s pressure. A robust foundation drainage system is essential to prevent water from accumulating around the foundation.
3. Structural Construction
The structural system must be designed to withstand the immense lateral pressure of the earth. Reinforced concrete is the most common material, but steel and other materials can also be used depending on the design. The walls and roof must be meticulously constructed to ensure structural integrity.
4. Waterproofing and Drainage
This is arguably the most critical stage. Multiple layers of waterproofing are essential, including a waterproof membrane, a protective layer, and a drainage system. The drainage system should effectively channel water away from the structure to prevent hydrostatic pressure.
5. Insulation
Proper insulation is crucial for maximizing energy efficiency. Exterior insulation, placed outside the waterproofing membrane, is the preferred method. This protects the waterproofing from temperature fluctuations and prevents thermal bridging.
6. Backfilling and Landscaping
Backfilling should be done in stages, compacting the soil to prevent settling. The soil should be carefully selected to ensure good drainage. Landscaping can further enhance the insulation and drainage, as well as integrate the house with its surroundings.
7. Interior Finishing
The interior finishing process is similar to that of a conventional house. However, special attention should be paid to ventilation and humidity control to maintain a comfortable and healthy indoor environment.
Frequently Asked Questions (FAQs)
Here are some frequently asked questions about building earth-sheltered houses:
Q1: How much does it cost to build an earth-sheltered house?
The cost varies widely depending on the design, size, location, and materials used. Generally, expect costs to be comparable to, or slightly higher than, conventional construction, especially considering the added expense of specialized engineering and waterproofing. However, long-term energy savings can offset the initial investment.
Q2: What are the advantages of living in an earth-sheltered house?
The primary advantages include energy efficiency, temperature stability, soundproofing, protection from extreme weather, reduced maintenance, and environmental benefits. Earth-sheltered homes also offer enhanced privacy and security.
Q3: Are earth-sheltered houses dark and damp?
Not necessarily. With proper design, incorporating features like courtyards, atriums, and strategic window placement, earth-sheltered houses can be bright and well-ventilated. Effective waterproofing and ventilation systems prevent dampness.
Q4: What type of soil is best for earth sheltering?
Well-draining soil is crucial. Sandy or gravely soils are ideal, as they allow water to flow freely and prevent hydrostatic pressure. Clay soils are generally not recommended due to their poor drainage. A soil test is always recommended.
Q5: How do I ensure proper ventilation in an earth-sheltered house?
Natural ventilation can be achieved through strategically placed windows, courtyards, and light wells. Mechanical ventilation systems, such as heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs), are also recommended to ensure adequate airflow and maintain indoor air quality.
Q6: Do I need special permits to build an earth-sheltered house?
Yes, you will need all the standard building permits, and possibly additional permits related to excavation and environmental impact. Check with your local building department for specific requirements. Compliance with local building codes is essential.
Q7: How do I waterproof an earth-sheltered house?
Waterproofing is critical. The process typically involves applying multiple layers of waterproofing materials, such as liquid membranes, sheet membranes, and bentonite clay. A robust drainage system is also essential to channel water away from the structure. Professional waterproofing expertise is highly recommended.
Q8: What kind of maintenance is required for an earth-sheltered house?
While earth-sheltered houses generally require less maintenance than conventional homes, regular inspections of the waterproofing and drainage systems are essential. Gutters and downspouts should be kept clear, and any signs of water intrusion should be addressed promptly.
Q9: Can I build an earth-sheltered house myself?
While it’s possible to do some of the work yourself, building an earth-sheltered house requires specialized knowledge and skills. It’s highly recommended to hire experienced professionals, including a structural engineer, an excavator, a waterproofing specialist, and a general contractor.
Q10: How do I finance an earth-sheltered house?
Financing can be challenging, as some lenders may not be familiar with earth-sheltered construction. However, it’s possible to obtain a mortgage by providing detailed plans, cost estimates, and assurance of structural integrity. Highlighting the long-term energy savings can also be beneficial.
Q11: What are the potential drawbacks of earth-sheltered houses?
Potential drawbacks include the higher initial construction cost, the complexity of the construction process, the risk of water infiltration, and the potential for limited natural light if the design is not carefully considered.
Q12: Are there resources available to learn more about earth-sheltered construction?
Yes, numerous books, articles, and websites provide information about earth-sheltered construction. Consulting with architects and engineers specializing in sustainable building is also highly recommended. Look for resources on sustainable building practices and alternative construction techniques.
Conclusion
Building an earth-sheltered home demands significant investment and expertise, but the potential rewards in energy savings, environmental responsibility, and long-term resilience are substantial. By carefully considering the design, materials, and construction process, and by working with experienced professionals, you can create a sustainable and unique living space that harmonizes with the natural world. The key to success lies in meticulous planning, unwavering attention to detail, and a commitment to building a structure that is both environmentally sound and structurally robust.