Hello All, hope you are safe and well in these unusual times. I'm a newbie here, but Mechanical Engineer by trade. I am about to start new (customized) construction, and want it to be as 'green' as possible...so trying to balance cost, eco-friendliness, reliability etc. of the various upgrades I have requested in my dream home. One of the biggest decisions is: Geothermal or not? I am considering a Climatemaster 6-ton "Tranquility 30" system w. horizontal ground-loop, desuperheater with supplemental heat unit...but if someone has an alternate system manufacturer in mind, would love to hear from them. Here are the spec.s, very much looking forward to the feedback - also thanks very much to all who kindly take their time to contribute in advance for your time! Stay safe... Location: Durham NC (27712) Design: based on Frank Betz "Northampton" Sq.Ft. (conditioned): 3700 (assume I'll need at a minimum a 6-ton unit with additional heater unit) Plot size: 1.05 acres Additional details: fully-sealed 4 ft. crawlspace, high-density spray-foam insulation throughout (none of that fiberglass stuff), brick exterior (I hear that has good insulation benefits as well as low maintenance / aesthetics), high-efficiency low-e windows.

What kind of wall do you plan to build, e.g. 2x4, 2x6, ICF, SIP, SCIP, etc.

I have done GEO in my last 2 houses and for heat Natural Gas is still over 20% cheaper to run(I have heated floors and can could run both houses on either system). For AC Geo works good. Mini Splits are the cheapest and efficient, especially if you have solar.

Good Luck we built our dream house 4 years ago....

Thanks Alton, currently planning on standard 2 x 4 - I didn't see any huge benefits on 6" thick walls from the articles I read, as we will be having the high-density spray foam insulation for all outer walls, crawlspace and roof plus the full brick façade cladding which should be a vast improvement in terms of insulation vs. 'traditional' fiberglass batts and cementitious siding. Thanks again for taking an interest! BR, Sacha

Thanks for the advice, and good to know...assume you are in Boston MA from your name, it's good to know that Geo is more expensive on the heating side. I'm hopeful we can offset the extra 20% heating bills for 3 - 4 months November - February we really need heat where we live in NC vs. the 6 months of needing AC in the April - September warm months...I know MA Winters are a lot worse than what we are used to here in NC! ;-) Out of interest, do you think a single 6-ton unit "should" be sufficient for a 3700 sq.ft. home, well-insulated and with the supplemental electric heater added to the system? It seems GEO is less good at heating vs. cooling; I checked the temps. at 6ft. depth here and they hold at 55 F. I'm also really interested to know how 'reliable' are GEO systems, what would you recommend? Thanks again for the support! BR, Sacha

In NC i think you should look into ducted mini-splits. Even looking into a cold climate one, you may not need any auxiliary heat.

No way a new house with spray foam needs 6 tons! Have an independent home efficiency company run a manual J heat loss/gain analysis.

Look into having rigid foam outside the 2 X 4 walls, reduce thermal bridging. Open cell spray foam in the walls is cheaper and better for the environment.

Chris

I agree with ChrisJ's comments. I asked about the composition of the wall because of the high HVAC tonnage. Far better to insulate outside with rigid foamboard and then inside with spray foam than to increase HVAC tonnage that carries a continuing energy cost.