My project is getting closer to HVAC time.  I am toying with a geothermal (lines in a lake) system, 'normal' heat pump, or gas furnace separate AC.  The house is located in central Alabama.  Is there an easy answer in terms of most efficient and money saved?  The house is approximately 2000 sf and has three levels.  Basement is mostly ICF, 1st floor is SIP, and attic (master bedroom) is SIPs, including the roof.  I will also need an air handler.

I am most concerned about proper sizing and proper placement of ducting.  Not so impressed with some of the HVAC contractors I have seen so far.  All want to go with 'rule of thumb' sizing.  Unless I am missing something, I have been lead to believe that is just not the case in this situation.  I envision two systems, one for basement and 1st floor and one for the attic? or any other suggestions?

Thank you in advance for any suggestions.

Bill

Need a room by room load calculation. Either pay someone to do it (rule out any contractor not willing to do one) or pay $50 for HVAC-Calc and do it yourself.

engineer,

exactly what I'm looking for. I will try and find someone with that skill before I make any commitments one way or the other.

Thanks

Bill

Agree with engineer.

One problem with "rule of thumb" estimates is who's thumb are you using :) ? Contractor rule of thumb here abouts in Florida is about 1 ton per 450 - 550 SF. A study by Florida Solar Energy Systems found this grossly oversized the units (less efficiency, worse humidity control). Their study showed about 1 ton per 700 SF produced better sized units for Florida.

You are going to want 2 systems if you want comfort. The top floor will need more cooling for sure and may or may not need more heating.

Zoning can allow a single unit to serve 2-4 zones, often different floors. An efficient house of 2000 SF will likely have individual floor loads well below many manufacturer's minimum unit size.

ICF, SIP, good insulation (sprayed foam) tight windows and doors can result in loads as low as 1 ton per 1500 SF, depending on climate. I'm in North Florida and my 3000 SF ICF house did fine all summer with a nominal 3 ton unit running in low stage (~2.5 tons)

Mine is 3 floors with 4 zones. Two zones are a tad small resulting in a little bit of noise from registers, but the versatility and efficiency means I'd do it again in a heartbeat. If anything, my unit is oversized, but won't be if down the line I lose the ability to run open loop water.

You've clearly picked some high efficiency building components - don't blow it now with a half-baked HVAC system. With ICF and SIP virtually anyone's thumb will need major recalibration. Thumbs work well opposing fingers, not so well sizing HVAC systems or components.

You may have a heckuva time finding an HVAC contractor willing to do it right, and that individual, if he she exists in your area, will almost certainly NOT be the low bidder. Persevere - it'll be worth it.

Thanks to all. I am going to do my best to find an expert to get this project sized properly. This indeed will not be the part where I skimp, I kind of did that with the backfill and am paying for it!

Thanks again to the online experts online here, always a pleasure receiving all the opinions.

Bill

An often forgotten point in the fossil vs geo question is that most geo contractors are (on the average) better duct designers due to the higher demands of the heat pumps for air flow. I often have to point this out in new home bids as the low bid fosssil guy is often doing very low end ducting.
I wouldn't recommend a geo contractor (or fossil) that doesn't do a heat load. I'm often suprised at how low the requirements are of a new home.
Joe