Your house does not need to "breathe"in the way you are thinking. Assemblies in your house need to breathe and in your area, to the dry inside. Nearly of your humidity problems in SE LA will come from outside. I would not listen to anyone about your HVAC and insulation issues except a qualified, impartial source. That is especially not a builder. Many contractors and builders are very conservative and want to keep building homes the way they were built 100 years ago before mechanical cooling was introduced. Your builder has indicated that he is conservative judging by your description. There are better ways to do it.

LSU has some great information on building energy efficient homes in this climate. That includes information about duct systems, insulation, sealing, ventilation and more. I suggest that you get your information there, from Florida university sources and from Buildingscience.com. It seems like you might be in position that it is too late for that and you need to catch up. I suggest that you hire an energy rater, energy consultant or something similar to help you out. Take a look at the BPI and Resnet web sites. A consultant can help design, design for some incentives (rebates and low-interest loans), test the house to make sure that your builder meets landmarks for efficiency and more. It would be well worth doing.

For starters, do not put any HVAC ducts or ducted equipment outside of the envelope of the living space of your new home.

Do you have the quote for a 6 ton Geothermal HVAC systems? I am skeptical it can be done for $24K. Do you have this price in writing?

Are you sure about the 30% local tax credit? Do you have a link describing this tax credit?

I would suggest telling the builder to remove the cost of HVAC from the contract, that you will take charge of that aspect of the project and coordinate with him its installation.

As for the ‘HVAC guy’ that told you, “1-well per ton, at 250ft/ton”, this would likely give you a VERY efficient geothermal system. It ‘sounds’ like more loop than what’s usually required but I don’t know your geology. This could be correct; it certainly sounds conservative which is OK in my book.

Best efficiency with ‘Liquid-to-Air’ geothermal heat pumps (liquid in the ground loops) occurs when boreholes are drilled one-ton per borehole, separated by at least 15-feet, connected in parallel, headers installed WITHIN the mechanical room, WITH the ability to VISUALLY measure the flow in EACH borehole! This will give you the capability to easily and quickly monitor, troubleshoot and balance the entire ground heat exchanger loop network. Money saved at this level by not doing this properly and taking shortcuts might become a VERY expensive curse later on should problems arise. You will get this money back when you cash out, sell your home and have an inspection done - if they know what they’re looking at!

A mechanical room should be built in the basement or the lowest level, preferably at the center of the house; an ERV is essential. The mechanical room must also contain an ‘AS Built Book’ that documents the complete design, specs, startup procedures and detailed startup measurements, as well as all the details and detailed location of the buried ground loops. You should also have a paper copy and digital copy of this document kept elsewhere in your home as well as at least one paper and one digital copy off site for safekeeping. Included detailed pics of EVERYTHING! This like having an electro-cardiogram of your heart done when you are well so that you have ‘baseline’ data to compare to as a reference when/if things go wrong and to also prove that they were ‘right’ at time of installation. It also affords you the ability to hire any knowledgeable tech to come on-site and quickly understand what’s going on. This is important if your installer goes out of business or if you have a falling out. It’s also vital for recouping the maximum value of your system at time of resale.

Stay away from attics for mechanical systems!

Find the right company to do the foam insulation; giving it the appropriate amount of time to cure and outgas and you should be fine. Check references and accreditations, this applies to the geothermal contractor and duct designer/installer as well.

One-way to further ensure the right size geothermal unit(s) would be to install variable speed unit(s), both fan coil and compressor. That way there’s some ‘play’ in the system and increased efficiency as well. The geo units will self adjust to whatever duct system they’re hooked up to, within reason and throttle down if there is too much capacity while still giving you proper dehumidification. Too small a system and you’re out of luck without expensive, extensive mods. Look into zoning - properly designed, installed and controlled!

The thing to ‘watch out for’ with ‘fully variable’ systems are flow centers or pumps, if you will, that are also variable speed, that they do NOT throttle down to a level where ‘turbulent flow’ in the ground loops changes to ‘laminar flow’. Without delivering a seminar on ‘flow’ in this forum, suffice it to say that you will need to have a discussion with your installer on ‘Reynolds Numbers’ and let them educated you and give you the seminar. If they seem clueless or flippant on this subject then you’re dealing with the wrong people that have not been properly trained.

Copy & Paste:

http://www.waterfurnace.com/literature/7series/BR2700AN.pdf

IMPO

SR

Here is a link that might be useful: International Ground Source Heat Pump Association at Oklahoma State University

Thanks for the replies, everyone!

@ionized

I started looking at documentation provided by LSU & I'm going to get to the other things you mentioned. These are invaluable. I've been arguing with the builder concerning how to lower tonnage & he's basically re-writing the basic laws of thermodynamics. To give you an example, he's attempted to tell me that since hot air rises, it's easier to cool a room with a ceiling height of 10ft vs 9ft (same square footage). I just shake my head at the idiocy. I'm sticking to 9ft, tyvm, lol.

Why would I be dealing with this joker? He's actually working on getting the house put together & I really only disagree w/ the HVAC, which in the end, even he said I have complete control over when determining what I want to do. His price is also fair (cost of materials + an overall percentage) & he's willing to work NOW. I can't find anyone to do any sort of work. I'm not sure how anyone in this field makes money down here. They work 30 days a year, it seems.

My original builder as been stringing me along for 8 months & I've been preparing my own property, where as with this guy, I'd have been fighting w/ him over hvac concerns,but I'd be in a completed home right now.

@ mike_home

The 24k is a ballpark guesstimate from what people have quoted here for 6 tons. I don't have an real estimate based j or d load.

I'm going to confirm this with a CPA, but we have a 30% local tax incentive for building green:

http://www.geothermalgenius.org/states/louisiana.html

That's how I get 60%.

@fsq4cw

What you're talking about is exactly what I've heard.

Both this builder & the original HVAC installer quoted 1 ton per hole, each hole is 250ft. Down here, the ground temp that low is only 70F-75F, most likely about 72F. I didn't know about the 15 spacing (wasn't sure what the spacing was, to tell you the truth). That's good info. I was planning on getting copies of the HVAC schematics, as well as taking pictures during the process (I bet they'll just love that). Thanks for reminding me.

I brought up the ERV to this builder (before you posted this) & he looked at me in such a confused state, it was almost hilarious. He's never heard of an ERV.

I do have one issue; I don't have room down stairs for a mechanical room. With the design of the house, it will be impossible. I was told to build a mechanical room in the attic; spray foam it, vent cool air (don't know if I'd need a return) & that should basically keep do fine. I can do that or foam the entire attic, which might be done anyways. If you're unfamiliar with the area, we don't have basements. 3' down & you hit water. At least the high water table should greatly aid in the heat dump of a geothermal.

I'd appreciate your opinion on where to put the AC unit.

Thanks for the last paragraph. I'll educate myself first on these things before even asking any more questions to anyone (shouldn't take TOO long).

What gets me about this builder is that he's looking at the house from a perspective of 1 ton per 500 sq/ft. Well, yeah, You'd need 10 to 11 tons for this house. Geo w/ properly installed foam, erv, etc should net 1 ton per 800-1000 sq/ft; so between 5 and 7 tons (rough guesstimate) . Like ionized said, builders want to do things the old way & I can see it right here with this guy.