Our Journey to the Carbon Zero Home

Our journey to the “Carbon-Zero” home.

The world in not running out of energy resources. The way in which we consume energy in the future and the source from which it comes is where the rubber meets the road.

The Earth maintains a balance between incoming solar radiation and outgoing radiation. It’s this balance which determines temperatures on the surface of the earth.

Greenhouse gases in the atmosphere absorb radiation (heat which has been reflected or radiated  from the earth)  and then radiated  back to the earth, warming the earth’s surface. Without this process, the temperature of the earth would be below the freezing point of water, so the greenhouse effect is a natural, necessary process.

Carbon Dioxide (CO2) is the second most important greenhouse gas. Because CO2 seems to accumulate more than dissipate over time, herein lies the concern. If the natural balance of greenhouse gases is disturbed, the effect over time would be dramatic temperature changes on earth.

One way to measure the environmental impact of a home is by the amount of CO2 its operation puts into the air, most of which is produced by power plants supplying homes with electricity, oil or gas. The average home in the US is responsible for putting approximately 40,000 pounds of CO2 into the air each year. Compare this to a home using conventional energy sources in a tightly-built home with a photovoltaic system, which produces not only its own electricity for the year, but a small surplus. Homes whose operation produces no CO2 are called Carbon-Zero homes. In addition to money saved on utility bills for a carbon-zero home, the environmental savings are the reduction in the amount of CO2 which would otherwise have been produced by a conventional utility power plant.

Two common strategies for working to achieve a zero-carbon-emission home are conservation and supply strategies.

Conservation Strategies concentrate on designs or changes which will reduce the amount of energy needed.

Supply Strategies include installation of technical systems and components such as photovoltaics, solar, thermal, and passive solar design.

Supplying consumers with drinking water uses energy for extraction, pumping, treatment, distribution, and dispersal of wastewater. Less water consumption simply means less energy required. Conservation is the mantra.

Toilets are responsible for about 40% of indoor water consumption. Use Low Flow Toilets or Pressure-Assist Toilets. Install a displacement bag in the water tank or a Vacuum-Assist Toilet.  Dual-Flush Toilets let you choose between a liquid or solid flush. Composting Toilets contain a tank or multiple tanks in which sewage and waste are composted.

How about a Greywater System? (referring to wastewater from showers, tubs, sinks, laundries, and dishwashers). Filtered greywater can be reused for toilets.

Landscape irrigation is responsible for about 50% of home water use. Limit turfgrass to 20% of a landscaped area (Xeriscape). Store roof-water and use for irrigation. Use bubblers, micro-spray and drip systems to provide more precise water placement at lower volume. Group plants together that need less or more water. Wind sensors will prevent spray irrigation at windy times. Use a programmable system to budget water.  The best time to water is between 5AM and 10AM. Allow grass to grow up to 3 inches long. This will shade soil and reduce evaporation.

Value engineering is the term used to describe enhanced-efficiency rough framing methods for building construction. Wood and steel wall framing members act as thermal bridges in transmitting heat through the building envelope. By reducing the number of framing members, 24 inch centers instead of 16 inch means fewer studs and a greater percentage of the overall exterior wall filled with insulation.

The use of Structural Insulated Panels (SIP’s) or Insulated Concrete Forms (ICF’s)  result in a building system that is extremely strong and energy efficient because there are no wall studs to transmit heat to the outside.

Daylighting is the practice of using natural light to illuminate a building interior. Light Shelves bounce light deep into a building. Skylights allow passive light in. Light tubes use a special lens designed to amplify low-level light. Sunlight is channelled through a tube coated with a highly-reflective material, then enters the living space through a diffuser. Fiber Optic systems use bundles of light-conducting tubes. At the exterior, light is concentrated on one end of the tubes using a parabolic collector similar to a satellite dish. The other end of the tubes terminates at a hybrid interior light fixture which also contains a conventional bulb. A photosensor will increase light from the bulb as exterior light fades.

Use infrared (IR) sensors to detect human body heat and switch lights on and off as needed.

Author of this article: Bill Marston BSc,CFP,RFP,CIM   Certified Home Inspector

References:

Facing the Hard Truth     :           http://www.npc.org/

Energy Sources:                        http://www.eia.doe.gov/neic/brochure/renew05/renewable.html

Greenhouse Gases:                   http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html

The Earth’s Energy Balance:       http://earthobservatory.nasa.gov/Library/#

The Earth’s Energy Budget:        http://earthobservatory.nasa.gov/Observatory/

Sustainable Building:                  http://www.greenbuilder.com/Sourcebook/