Geothermal, Ground Source Heat Pumps

 

Ground Source Heat Pumps GSHP is a term preferred over Geothermal. They are one of the most energy efficient mechanical systems available for heating and cooling in most climates. They have all the advantages of typical heat pumps but are capable of using less electricity. 

                                            

Typical heat pumps use the outdoor-air as the exchange medium.	Ground source heat pumps use the earth. Condenser units can usually be moved inside.

 

GSHP enjoy good reputations. In addition to energy efficiency gains, they can eliminate the noisy, unsightly outdoor-unit and have longer warranties with less maintenance needs. Some models are capable of providing water heating at very low costs.

These GSHP benefits come with high upfront costs. Ground tubing and trenchwork can more than double the costs of a traditional air-source heat pump. This is a high risk investment for those that don't do their homework.

Compare Extra Upfront Costs with Expected Energy Savings

GSHP tends to make the most financial sense for big homes, long-term ownership and inefficient building envelopes. If upfront costs are not paid back by energy savings, then its not a good investment and probably has questionable environmental benefits.

Well designed homes with high performance building envelopes delay expected simple paybacks. Airtight, thermally efficient homes can put GSHP paybacks into the 20-50 year range which could be close to the end of the mechanical equipment's life.

 What is a Building Envelope?           The Blower Door Test.           Outdoor-Air Ventilation

In terms of cost-effective energy efficiency, new homes will benefit most from smart design and careful assembly of the building envelope. These more affordable measures push the paybacks of GSHP into questionable territory. Bigger, less efficient homes are a better fit for an expensive GSHP investment.

Some energy experts question whether GSHP save energy at all. Newer technology and proper installation overcomes many of the energy concerns raised but the high upfront costs dont seem to be going away.

A Technology Dependent on Tax Incentives

Tax incentives are a main variable for the fiscal viability of GSHP. With federal credits of 30% and a NC credit of 35%, taxpayers are burdened with 65% of the costs for these expensive systems. Unlike solar PV which is a renewable, GSHP is a conservation measure only. They don't help the community in the way that grid-tied PV does. If trying to choose between the two, grid-tied PV is often a better financial and environmental investment. Energy experts concerned for the envrionment question the large tax incentives GSHP technology enjoys.

Ground connections

A big variable of GSHP design is the ground loop configuration. More affordable installations can be done on nearby bodies of water like ponds and lakes that don't freeze through. Many existing systems use open-loop wells. Horizontal installations can be more affordable depending on the site conditions, but most of the industry prefers vertical closed loop designs which require a well drilling contractor. 

An important aspect of GSHPs is proper installation and commissioning. A strong team is needed for the players: homeowner, builder, rater, HVAC contractor, equipment supplier, and ground tube installers or well drilling contractor. Ensure the system is working properly by closely monitoring costs and performance. 

For brands in our area, Water Furnace has been the leader but the new Bosch GSHP line (formerly Florida Heat Pump) should see quick market presence being carried by Ferguson, a national supplier with good customer service. 

One of our custom homes most recent GSHP installation with Bosch equipment. This model combines the air-handler and condenser into one unit and features a desuperheater which pre-heats domestic water on it's way to the heat pump water heater. A cheap, un-energized water heater serves as a buffering tank. Well drilling for domestic water yielded two, dry wells letting GSHP capture otherwise wasted costs. One, 700' well was enough for this home.

GSHPs are a great choice for heating and cooling in our climate depending on the project's scope. Make the investment carefully, choosing the right team as a priority to equipment. Radiant floors are another subject falling into category of questionable fame. Are radiant floors the Kim Kardashian of sexy building technologies?

Radiant Floor Heating     Heating and Cooling in WNC   Choosing Heat Pumps      

Springtime Builders is an Asheville NC custom home builder committed to building science best practices and cost-effective energy efficiency. 

Posted in Heating and Cooling