Solar home with Sharp solar PV panels

It's an interesting study to see how home building techniques and materials have evolved over time, and how new ideas that were once radical have become common.  Drywall, for example, quickly replaced lath and plaster as the standard for interior walls, and radiators were replaced by forced air systems.  As we began closing the windows in the summer to keep our homes cooled by our central air conditioners, insulation and thermal windows came about.   All-electric homes were all the rage until electric rates cooled owners' interest.

Today we find ourselves on the verge of a new set of building standards.  With concerns about climate change and declining fossil fuel resources, many homeowners are looking to harvest the clean, renewable energy of the sun.  In the 1970s, the US led the world in the development of solar photovoltaic (PV) technology, where sunlight is converted to electricity.  As energy prices dropped in the '80s, our enthusiasm waned, since the payback was no longer as attractive.  The recent increase in worldwide demand has brought PV prices down, and the uncapped financial incentives have made the payback on solar better than ever.

Energy Efficiency

At The Energy Savings Store, we always encourage solar and wind prospects to consider energy efficiency first.  As much as half of the energy we use in our homes is wasted, either by inefficient appliances, inadequate insulation or ineffective stewardship.  Energy Star appliances are now readily available, and the added cost is quickly offset by the reduced energy requirements. 

It's critical that the "building envelope" - or exterior shell exposed to the elements - be tightly insulated.  There are a variety of methods to achieve this, including 2x6" frames, high-efficiency foam insulation, and insulated concrete form (ICF) construction.  The latter uses stay-in-place concrete forms made of hard foam that are assembled much like Lego blocks.  The concrete is reinforced with steel bars, making this shell extremely durable while minimizing thermal transfer.

For larger homes, ground-source heat pumps are a great way to use the constant temperature of the earth to heat and cool the home.  Geothermal systems are relatively expensive but, coupled with a super-insulated building exterior, dramatically reduce expensive heating and cooling costs.

Adding Solar

The key requirement for solar is southern exposure.  If your existing home has a south-facing roof (or within 30 degrees of due south), you can likely incorporate solar onto your roof.  If you're building a new home, be sure to consider this important requirement!  The slope of the roof should be somewhere between 25 and 40 degrees, with 38 degrees being optimal for this latitude.  Conventional panels can be angled on racks to adjust or optimize the pitch, but for new roofs it's best to design the southern facing slope accordingly.

While conventional solar panels are most commonly used, there are a variety of new options to incorporate solar into the building design.  A number of solar roofing tiles, including SunSlate and SolarSave, are used alongside metal or asphalt shingles, and can be installed on the front of a home without detracting from the appearance of the home.  Other metal roofs can take advantage of solar PV laminate systems like Uni-Solar.   Even if you're not ready to invest in solar, you can pre-wire your new home to minimize costs

Micro-inverters enable you to start out with a small number of conventional panels and add to the system as your budget allows.  Inverters are used to convert the DC power produced by the solar collector to AC power used in your home.  Rather than using a single inverter that is sized for the entire system, micro-inverters are installed onto each panel, converting the DC to AC right at the source.  Battery backup systems are also available to keep your essential appliances powered during an outage.

Water heating accounts for 20-40% of typical home's energy requirements, and solar water heating systems have proven to be a very cost-effective way to harness the sun's energy.  While these can be used in conjunction with solar PV, they are an excellent alternative if you have limited space.  The VELUX solar water heating system is an attractive complement to the traditional skylights that they're renowned for.  Solar air heating systems, such as SolarSheat, are also available.

There are many other ways to harness the sun's energy and protect your home from unwanted heat in the summer.  Natural daylight reduces lighting requirements, using windows, skylights and solar lights like Sun Tunnel or Solar Tube.  Strategically-placed shade trees and passive solar design can capture the warmth of the sun in the winter, but shade the home in the summer.  It is essential that you consider the sun, which is ultimately the source of all of our energy, when you build your next home.

For more details on these and other strategies for incorporating solar into your home, see the online version of the May 2009 issue of Solar Today on page 32.  For a fun look at what the futurists have imagined, check out The Green House of the Future.