If my building is already efficient will a GCHP system be worthwhile?

You might have been told that if your building is already well insulated and energy efficient there's not much point in considering a GCHP system. There simply wouldn't be a payback because of the cost of installing a GCHP system and GHX is so high that I'd never get a return on my investment.  I'd like to dispel that myth!

One of the problems in the geothermal heat pump industry is that too often designers and contractors use "rules of thumb". There are projects that have been designed and specified for contractors to bid on simply using rules of thumb. Let's look at an example using a 50,000 square foot (4,650 m2) building:

• Heat loss = 50,000 square feet x 25 Btu/hr = 1,250,000 Btu/hr (366 kW)
• Cooling load = 50,000 / 350 square feet / ton = 143 tons (502 kW)
• Borehole required = 143 tons x 180' / ton = 25,740' of drilling
• Borehole configuration should be 1 borehole / ton = 144 borehole (round up to a non-prime number) x 180'

Great...12 boreholes per supply & return runout pair x 12 pairs of 2" runouts and there's your design. Done!! On to the next one, right?

The sad truth is that, many times, such a system, if it's not too expensive to install, will work, and it may even work reasonably well 80% or 90% of the time. But if the building is well designed, and the GCHP and GHX designer uses detailed energy modeling as a design tool, it is likely that actual building loads are much different than the rules of thumb would guess at. This means the capacity of the heat pumps needed will be much lower than rule of thumb estimates, and implications on the size of the GHX can be enormous. 

And if the designer has an opportunity to work closely with the owner and his or her design team, using the energy model as a design tool it's possible in most projects to reduce the size of the heat pump system and the size and cost of the GHX, while creating a more efficient, robust system. This can have a large impact on the return on the owners investment.

To answer the question about the return on investment in a very efficient building: It an be a very appropriate system and provide a very solid ROI IF the designer takes the time to go through the design process needed to design a GCHP system and GHX. 

The Certified GeoExchange Designer (CGD) commercial geothermal system design course offered by IGSHPA and AEE is a 3 day course that goes over in considerable detail the design process that is needed to optimize the design and performance of a GCHP system. 

An example of the impact this approach can be seen in a presentation at the QUEST Conference in Winnipeg, November 2012