A Net-Plus home or building is one that produces more energy than it consumes. This means that the excess energy can be returned to the grid.  This usually is accomplished through a line-tie system that connects the home’s photovoltaic system with the community grid. This is why these buildings are called Net-PLUS. Energy that is returned to the grid is then credited to the owner!

Can you imagine how great it would be to be totally self-sufficient? ……..to say goodbye to energy bills? …….in fact, to receive money back from the utility company?

A Net-Plus home can also capture more water than is needed for both irrigation and home consumption through proper water harvesting!  Excess water can then be returned to the landscape to replenish the aquifers below.

HOW IS THIS ACHIEVED?

There are steps to consider when designing a Net-Plus home.

First you need to have the building oriented correctly toward the south in order to optimize the energy of the sun entering the building through the windows. The sun can then passively heat or cool the structure’s high mass. Mass refers to a material’s energy storing capacity.  Thicker walls, concrete or tiled floors are all excellent ways to capture the heat of the sun or the cool of the evening.

Second, it is important to consider the placement of windows so that unwanted heat is avoided during the summer and the optimal capture of solar energy can occur during the winter months.

Third, insulation must be designed and applied carefully so that no heat (or cool) is lost.   The use of minimum R-5 windows and doors is an important part of the insulation process. Window quilts are also an excellent way to provide extra R-value.

Fourth, an active solar collector system (a photovoltaic or PVC system) provides electricity for lighting and appliances. If energy-efficient appliances, lighting and motor loads are chosen, the electrical energy used can be reduced by 50%. Today, there are so many highly energy-efficient appliances and lighting systems that a moderate PVC system is more than adequate.  And, with the excellent federal and state credits available for PVC and hot-water systems, the cost is quite minimal.  Sun-heated hot water (solar hot-water systems) can also provide in-floor heating as well as all domestic hot water needs.

Fifth, where needed, additional heating and cooling can be provided by running water through tubes that are integrated into the roof, floor and/or walls.  This water can be heated by the sun on the floors or walls or chilled at night by night sky radiation on the roof.  The cooled water is then run through the same tubes that are used for in-floor heat during the winter.

Finally, a rainwater catchment (or “harvesting”) system is the final ingredient. And, though it may be hard to believe, there is enough rainwater that strikes the roof of a moderate home in the desert climes of the southwest to easily satisfy a family’s needs.

There are several rating systems which score homes for energy efficiency.  The first is Energy Star.  Another is LEED for Homes which scores on a scale of 0 to 100 with zero being the best score.  A Net-Plus home can often EXCEED the LEED for Homes rating!

You are invited to comment or ask questions.