Craftsmen of Homes

540-797-3059

Roanoke & Smith Mountain Lake, Virginia

Geothermal

Geothermal is also considered a renewable energy source, though it doesn't directly rely upon solar radiance to do so. Rather, the ground's near-constant temperature at a home site is used.

Heat Pumps

Heat pumps literally move heat from one environment to another. You've likely heard the term 'heat pump' used in relation to space heating and cooling. And it was likely used to reference an air-source heat pump (ASHP). For common air-source heat pumps, heat is 'pumped' into a building during winter, and heat is 'pumped' out of the building in summer. The 'pump' mechanism is the remarkable 'air conditioning' cycle, where refrigerants are expanded and compressed to either pick up or drop off heat.

Air-source heat pumps to heat and cool a house use the ambient air, outside the home, to pump heat into and out of. And therein rests a challenge:  this ambient air temperature continually fluctuates within an approximate range of 100 degrees. The transfer efficiency of an air-source heat pump is indeed affected by the ambient air temperature; the more extreme the ambinet temperature, the harder the pump has to work to move heat.

Ground-source heat pumps (GSHP) use the near-constant temperature of the ground as the place to move heat into / out of.  Ground temperature = geo thermal.

On the surface - no pun intended - ground source heat pump makes a lot of sense.

Deeper investigation in the practicality of these systems, for typical homes, shows that geo thermal is not necessary for high-performance home design and building here at Smith Mountain Lake, Moneta Virginia.  If you had to drive an Army tank to work every day, and your fuel MPG was less than 1 (correct - one mile per gallon of fuel), then the cost of each gallon would impact your energy budget severely.  If on the other hand you drove a new fourth-generation Prius hybrid, which is predicted to achieve an average of 55 to 60 MPG, then you would be insulated far better against fuel costs.  This same logic applies to the debate between air-source and ground-source heat pumps for homes.  If you have designed and built a higher-performance well-insulated home, the slight savings in fuel costs (the promised improvements in system C.O.P.s - coefficients of performance) don't mean that much to your budget; and in fact, the cost of a geo-thermal system install may never provide you a "pay back" in savings, especially when we consider most mechanical equipment needs to be replaced within a 20 to 25 year operating period.

It is true that IF a building (large residential, commercial, industrial, educational) consumes great amounts of heating and cooling energy - like our Army tank in the illustration above - then geo thermal heat sourcing likely could make a significant improvement in energy budget performance.

For most of the higher-performance homes we design and build however, we do not recommend geo-thermal heat pump systems - when the decision is based on payback time periods.  The market advancements for solar PV (photo-voltaic) electric systems, even in Virginia, make these a far more attractive investment.

 

Timber Ridge Craftsmen, Inc.                                                                               540.797.3059

One of Virginia's finest custom home builders, experienced building energy efficient homes. Smith Mountain Lake, Moneta, Bedford and Franklin Counties, in the beautiful Blue Ridge Mountains of Virginia.      Google +      Houzz