Residential Geothermal – The Basics

One of the biggest (and greenest) trends in today’s residential and light construction market is residential geothermal installations. Geothermal isn’t yet the go-to solution for new housing but it is now a viable option when building new homes. People are beginning to figure in the cost for geothermal when they budget for a new home. Also, more and more contractors are becoming certified and trained in geothermal installations, which helps lower the cost for installation. 

It is too early to predict, but all indications point to the realization that geothermal HVAC in houses are great for home resale. It is very standard for homebuyers to ask for a month by month list of utility bills for the immediate 12 month past. Having geothermal in your home will give you the benefit of lower monthly utility bills  while you own the home, and the ability to market this information when you are ready to sell (not to mention bragging to your friends when they talk about how hot this summer was compared to years ago).

Alright, here are some highlights. 

Pros and Cons of Residential Geothermal 

Pros:

  • Highest efficiency option, lowest operation costs
  • Same homeowner maintenance – only a filter change
  • Provides heating AND cooling
  • No ugly condensing unit sitting outside your home
  • Two-stage/variable speed capability for even more efficiency option
  • Same ductwork routing as normal split/furnace/heat pump
  • More thermostat options
  • Can also replace your traditional water heater

Cons:

  • More expensive first cost
  • Not a good solution for a poorly insulated home
  • Fewer licensed contractors available
  • Installation of ground loop is an eyesore at first
  • Must have adequate land/pond available for ground loop

What do I need to know to get started?

First,

You must have some area to install a ground loop. If you have very little space, a vertical well field is a good option. This would require at minimum a 15’ by 15’ plot of ground for each well. Plan for one well per 1000 square feet in your home. 

If you have more land, and would like to minimize drilling costs, a horizontal well field is a good option. Although typically cheaper to install, horizontal fields aren’t quite as efficient as vertical fields. Regardless, budget a 150’ (long) by 15’ (wide) trench for every 400 square feet in your home. This trench will need to be at least five feet deep (preferably 6 feet).

If you have a pond on your property, this is a very cost effective option. Plan for a 4 feet wide trench from your home to the pond. Ideally the pond should be larger than 3/4 of an acre for adequate heat transfer.

Second,

Find a good geothermal contractor. You can search for these online (our tip is to Google “Geothermal Contractor YOUR STATE”) or ask for referrals. Searching online is great, but you often get what you pay for. Here are a few tips:

  • Search Geothermal Contractor YOUR STATE
    • Call them and ask for references.
    • Ask them what geothermal heat pump manufacturers they work with. If they are exclusive to one manufacturer, you might be paying too much.
  • Search Mechanical Contractor YOUR STATE
    • This is more broad, since mechanical contractors are more broad and work with many more system types. Translation: you must do more diligence to make sure you get a quality installation.
    • Ask for references.
    • Ask them if they are IGSHPA certified. If not, make sure they subcontract the well drilling to an IGSHPA certified driller.
  • Seek out geothermal installations in your area as references
    • Search for schools and hospitals that have been renovated or newly constructed. Geothermal is used more and more in these sectors because they realize fast payback due to high operational costs.

Do not skimp on doing diligence to find a contractor that has experience. You want a quality installation. One major reason we suggest certified drillers are due to the fact that once a well has been drilled and pipe installed there is no way to undo a mistake. It often has to be abandoned and another well drilled. We advocate doing it ONCE, and doing it RIGHT!

Third,

Contact your neighbors. This may seem trivial at first but if you and a neighbor could coordinate installations together, you could see HUGE savings. The largest savings here would be for drilling. If a drill operator can make one mobilization for two or three installations, you can very likely negotiate several hundreds of dollars savings. This is something that must be done early on, but could be a large motivating factor (for you and the driller).

But I already have a house with a conventional system…

Don’t worry! Residential geothermal retrofit options are a very good option. If your conventional system is greater than 10 years old, a geothermal retrofit is a great option.  There are lots of things you can take advantage of in a replacement scenario:

  • Keep your ductwork (in fact, this is a great time to clean it)
  • Keep your hot water storage tank
  • Your new heat pump will probably fit in the same space as your (now retired) forced air furnace
  • Throw away the condensing unit outside your home
  • No more combustible material or vent gases
  • No more fuel storage

As with the theme (this site is about pros AND cons, right?) there are some downsides:

  • You will have to drill through the wall or through the floor to route new geothermal piping
  • You will have to dig a trench from the home to the well field (bye bye landscaping, a small portion)

Retrofit options can be a great fit if your forced air furnace system is in decent shape. All of the aforementioned drilling and heat pump costs will still apply but you are saving on costs of ductwork and hot water storage when you pursue a retrofit. Consult with a contractor to see what’s best for your house.

Wrap Up

Using geothermal in residential settings is in its infancy, but will undoubtedly save you money. Also, with warranties of over 20 years on heat pump equipment and 50 years on piping (both are very typical), you will rest assured for quite some time. If things change, you can rest assured that geothermal will be a huge selling point when buyers are considering the value of your house.