Why must HVAC decisions be so complex? (Or… Is geothermal worth it?)
In another thread, my choice for HVAC was appropriately questioned. The system seems inordinately complex, costly, and convoluted. At least, on the surface. But digging deeper, the reasoning behind the design becomes clear. But, does that make it right? Is this the best HVAC design, or is it redundant and wasteful?
Here are the pertinents:
• Climate Zone 6
• 2700 sq. ft. finished space in story-and-a-half (bungalow style) house
• 2000 sq. ft. unfinished basement (future completion for aging parents)
• 4 Bdrm, 3 ½ bath house
• Tight, highly insulated home
• Manual J heat load calc 56,000 BtuH, total cooling load 32,000 BtuH
Features important to my wife and I in designing the HVAC:
• Warm feet
• Low operating costs
• Ability to control zones as we have kids leaving, but may have aging parents coming
• Quiet, “I hardly know it’s there”, operation
• Right sized for our needs
After listening to our desires, the HVAC contractor designed the following system:
1. Geothermal ground source heat pump
a. 4 ton water-to-water unit – hydronic heat to basement and non-hardwood flooring areas of main floor
b. 3 ton split system – forced air for cooling of entire house, and forced air for heating areas not served by hydronic heating (loft area and hardwood floor great room/entry
c. Domestic hot water generation
2. Gas furnace with variable speed (ECM) blower
a. To serve as the air-handler (AH) for geothermal split
b. To provide for back-up heat to allow us to take advantage of reduced electric rates on geothermal system.
When presented with the estimate for installation, I about choked. I then began researching and exploring other options, and am STILL exploring other options. Such options include:
1. Trad’l gas furnace with central A/C
2. Ductless minisplits
3. Gas boiler for hydronic, with mini-splits for cooling and spot heat
4. Boiler for hydronic, with furnace for hardwood areas of home, and trad’l A/C
5. Geothermal forced air system alone
6. Ducted mini-splits
All involved a significant compromise, and systems I thought would be more cost effective proved not to be, when the cost of rebates, tax breaks, reduced electricity rates, operational costs, and functional efficiencies over the 25 years we intend to inhabit the house were considered.
I planned to start digging the geothermal pit for the loops in 2 weeks, but as yet, I’m not locked in. I invite all interested reader to criticize my HVAC, and discuss the alternatives. I very well may be missing something!