Question

We'd like to go w/ DX geo heat & possibly retrofit w/ radiant heat. Can we combine for efficiency & what would the cost be?

Asked by Jenny Kerr
Bedford, IN

House is 100 y/o 2 st w/ finished bsmnt & attic, approx 3,600 sqft. No ducts, baseboard units, etc. Previously had a boiler/radiator system that "exploded" between the time we purchased and the time we moved in, it is completely non-functioning so would like to install all new and up to date high efficiency eco friendly system. Original hardwood floors through out that I would NOT want to tear out. Easy access to floor joists when ceilings are going to be replastered.

Answer

Michael Holcomb

Answered by Michael Holcomb

Byron Center, MI

Alliance for Environmental Sustainability (Headquarters)

October 14, 2011

Jenny,

Geothermal can be an extremely eco-friendly HVAC system when installed in a building that has been designed or retrofitted to reduce the BTU-requirements to heat and cool the structure.

I couldn’t begin to estimate the cost of the described system because there are too many variables that are unknown.

  • Equipment costs vary slightly but there are huge variations in cost with regards to the number of wells/ trenches needed to meet the heating/cooling load requirements.
  • The greater the Btu requirement the more expensive the installation (and operational costs).
  • Plus there are additional costs to match a geothermal system to the existing heat distribution system in your home.

Geo not the right fit for your circumstances?

Bedford has approximately 5600 heating degree days and 9000 cooling degree days. This means your primary concern for equipment sizing leans towards cooling.

  • Geothermal can provide both heat and cooling but significant modification to the delivery system would be required to make that happen.
  • Major modification typically equates to major cost.

You’ve indicated that the home has a finished basement and attic so upgrading to radiant heat is going to require a lot of destruction to ceilings, walls or floors. Since you aren’t set up to distribute cool air you won’t be able to take advantage of the cooling capacity of a geothermal system or the “free” associated potable hot water.

Geothermal sounds sexy but not necessarily the right thing in your circumstance.

  • The most eco-friendly strategy would be to reduce your Btu load.
  • The less energy you use to condition the air in your home the less pollution you will produce.

Reduce your BTU load

My best advice would be to have your home professionally audited by an independent energy auditor (Energy Home Chek, LLC 317-259-0759) to determine if the thermal envelop is adequate.

  • If you need significant upgrades to air sealing, insulation, and fenestrations (windows/doors) you might be wiser to install a high efficiency modulating boiler.  
  • Baxi wall hung boilers are very efficient. 
  • Using information provided by the energy auditor you can invest in thermal envelope improvements as time and budget allow.

Then, solar heated water

Once the Btu load requirement is sufficiently lowered you might supplement the boiler with a solar heated water system to improve your eco- friendliness.

  • Based on your climate zone you may be able to supplement a significant number of Btu’s for heating (and potable hot water in) your home using a solar water heating system matched to your boiler system.
  • Solar water heating systems are user friendly, cost effective and minimally invasive.

I have a system on my home (Grand Rapids, Michigan) that has been in service since 1974 and still provides the majority of our potable hot water needs.

Now that’s a wise investment in environmentally friendly technology.

Tagged In: heating cooling

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.