Designing an Ultra-Efficient Home

Passive Solar Home Design

The main advantages of a passive solar home include lower heating and cooling costs as well as the potential to generate your own solar energy in order to supply parts or even most of your household’s energy needs. If you are considering a home that incorporates passive solar design, it is important to work with architects and contractors who are experienced with this type of a construction project.

A successful passive solar home needs to have an unobstructed view of the sun on its south-facing facade. Consider whether nearby construction projects or trees could impede your home's exposure to sunlight. A passive solar design works by having windows oriented to the south so that sunlight can be harnessed. Solar panels can be attached to the roof to capture the sun during the daytime. There are many major passive solar design elements to be considered, including insulation, air sealing, and thermal mass.

The building's thermal mass should be constructed to absorb heat during the day and keep that heat within the construction materials. Passive solar homes require particular conditions with regards to their location and shading; in addition, they require the glazing of windows as well as auxiliary heating and air conditioning systems that provide a backup source of indoor comfort on cloudy days.

One method of passive solar home design is with direct gains. The southern windows receive sunlight that passes through the windows to concrete or brick flooring and walls. The masonry absorbs the heat and stores it. At night, the thermal mass radiates the heat into the house.

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In addition to masonry, water can also be used to store thermal energy. A water thermal storage system makes use of a network of pipes and storage tanks that absorb heat and release it as needed. These homes are cooler in the summer and warmer in the winter.

An alternative design for a passive solar home is a so-called indirect gain design. In this design style, thermal energy is stored between the southern windows and the home's living spaces with a trombe wall.

The trombe wall has a glass external layer and an internal layer with a high heat capacity. These layers are separated by a layer of air for insulation. On the outside of the trombe wall, the roof extends to shade the windows from the higher arc of the summer sun.

The inclusion of a sunspace is a common design element in passive solar homes. The sunspace, sometimes called a sunroom or solarium, can be separated from the home's living quarters with doors or windows. They provide auxiliary heat in the winter and a sunny place to relax and grow plants during the warmer months of the year. Passive solar designs may include overhangs, retractable awnings, motorized window coverings or manually operated shutters. Reflective coatings or panels in addition to simple interior shades and thermal blinds can also be used in the summer to block unwanted heat gain.

Alternative Energy Efficient Home Designs

Earth-Sheltered Homes

Houses sheltered by earth take advantage of geothermal insulation. The cost of constructing one of these homes is higher and they tend to have issues with moisture unless they are built in places with low humidity levels. On the other hand, the benefits of earth-sheltered homes include a greater level of protection from extreme outside temperatures, less outdoor maintenance and better insulation from outside noise.

An earth-sheltered house is similar to a basement, except for the living quarters being partly underground. These houses blend nicely into the environment and function most efficiently when they are constructed into a hill. Building an earth-sheltered house into a steep slope requires less excavation in comparison to building one on a piece of flat land.

Granular and sandy soils are ideal for earth-sheltered houses because clay has a tendency to expand when it gets wet. Such expansion could lead to shifting and cracking of the home's walls and foundation. The construction materials used for an earth-sheltered home must be waterproof and thick due to pressure from the soil and moisture from the groundwater.

In most of these homes, concrete is used for the main part of the flooring and walls. Wood may be used for interior walls and to finish the floors. Modified bitumen and rubberized asphalt are commonly used for waterproofing the portions of the home that are sheltered with soil.

"87 Gedney Road, Long Sutton" by Harrall2 on Wikimedia Commons, licensed under CC BY-SA 3.0

Insulation levels in earth-sheltered homes are typically less thick but need to provide protection from humidity. Adequate ventilation must be integrated into the architectural plans.

In general, there are two types of earth-sheltered homes: underground and berm earth-sheltered houses. An underground earth-sheltered home does not allow for the direct penetration of sunlight. With a berm earth-sheltered home, the southern exposure does get direct light from the sun. The roof may also be above the ground level.

Straw Bale Homes

A straw bale home diverges from the traditional method of building and constructing a house. The advantages of straw bale homes include the sustainability of the materials, the ease of insulation and the cost-effectiveness of the structure. They are also highly energy efficient. A homeowner can design, construct and build their own straw bale house with a little knowledge and building experience.

Straw is a simple, flexible and organic material that can be grown with a minimal use of herbicides or pesticides. Its use in home construction can save up to £10,000 on an average house with three bedrooms. The high R-value of straw bales means that homes built with this material may have heating costs that are up to 75% lower than a house built with standard construction materials.

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In straw bale homes, the straw acts as both the building blocks and the insulation. When constructing a house from straw bales, the walls are primarily made of straw. A few adjustments are made to the home's foundation to accommodate this change. The plumbing, electrical and interior wall systems are constructed and installed using standard methods.

The efficiency of straw bale homes provides comfort all year long. Straw bale homes can be composted at the end of their useful lifespans and offer a net decrease in greenhouse gas emissions.

Energy Efficient Roofs

Every home needs a roof, and the roof's design and materials are critical to the structure's energy efficiency. Energy efficient roofing designs include cool roofs and green roofs. A cool roof reflects almost all of the infrared energy from the sun and dissipates it back into the atmosphere. To make a cool roof, designers can use metal sheeting, reflective tiles, and shingles or reflective paints. More modern design elements may include ceramics to finish the tiles.

The efficiency of a cool roof depends on the climate, with the highest level of energy efficiency in places that are sunny throughout most of the year. A cool roof lowers summertime air conditioning costs. These roofs also help to increase the comfort level of a home's upper level and allow for a loft to be finished into a liveable space. In addition, they can help to minimize the urban heat island effect.

Any kind of roof, including shallowly sloped and steeply sloped, can become a cool roof if the right type of exterior finishing material is used. A reflective pigment can be painted or embedded into all roofing types. On a low sloped roof, marble chips or grey slag may be substituted for black gravel or asphalt. Cool asphalt shingles or naturally reflective tiles can be used as the exterior material for a steeply sloped roof.

There are many factors in deciding whether or not to install a cool roof. Cool roof materials such as slate tile are more expensive than black asphalt shingles, but cool shingles do not cost much more than traditional black shingles. The climate is another issue to be considered. Asphalt shingles work well in places with moderate climates, while clay tiles work best in dry places. In humid areas, moisture control is a concern. A waterproof barrier can be installed onto the decking of any roof to help with leak prevention.

"Green roof" by Arlington County on Flickr, licensed under CC BY-SA 2.0

In addition to cool roofs, green roofing systems are growing in popularity. Their benefits include increased insulation values, natural cooling effects due to plant transpiration, a new habitat for native plants and the creation of a place where people can go to relax. A green roof can be added onto an existing building or built from scratch.

There are several different types of green roofs including intensive, extensive and patio roofs. Intensive green roofs have a thick soil medium and a wide range of plants, whereas extensive roofs contain a thin soil medium and limited plant choice. The patio roof has potted plants, which provides very little energy efficiency value but is the only option for some types of homes.

A green roof is a great choice for managing excess rain water. It is also a good option for people with a limited garden area who want to enjoy a green outdoor space. When you are considering a green roof, choose plants that can handle intense heat, direct sunlight and drought. You will also need to select plants with shallow root systems because a roof can only accommodate a limited amount of soil. Some ideal plant choices include sedum, perennial grasses, and native wildflowers. The soil of a living roof can include layers of crushed brick or stone, pebbles, sand and organic soil.

Energy Efficient Landscaping

Proper landscaping strategies have many benefits. They can help reduce your home's energy costs by blocking intense summer sunshine and cold winter winds. They also lower pesticide, water, and fertilizer consumption because energy efficient plants are naturally resistant and tolerant to extreme conditions. In addition, an energy efficient landscape design helps to control air and noise pollution.

When choosing plants, consider the shade they deliver. You will need to understand how the sun creates shadows over the course of the day and over seasons of the year. Planting deciduous trees on the south and west sides of the home can shade intense summer sun, while pine trees on the north side help to block winter winds. Pine trees act as year-long windbreaks and can help to lower home heating bills.

Plant shrubs closer to your home so that they can shade the lower portions of the walls. A vine covered trellis may also provide shade to your home's perimeter.

Conservation of water is another important factor in landscape design. Know how much water your plants need and water them in the morning. Try xeriscaping, which requires careful planning, plant zoning, mulching, limiting grass and improving the soil. Efficient irrigation and careful weeding and removal of pests are essential to xeriscaping your property.

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To sum up, ultra-efficient homes make use of alternative materials and renewable energy sources that optimize energy efficiency. When fully integrated, these homes deliver optimal comfort and many environmental benefits. Although they sometimes require higher initial costs, ultra-efficient homes are much more comfortable than standard houses and far less expensive to live in.