Air source heat pumps don't make sense in areas where winter temps frequently fall below 32 degrees. Once you get below freezing, you will be running the auxillary heat a lot. If you decide to go the air source route, you will want a second stage gas fired auxillary heat. I live in the mid-atlantic region in the mountains and selected GT. That choice was coupled with a blown cellulose insulation package. My other choice was a propane heat/electric AC with a foam insulation package. Both options were roughly the same install cost. Both would have provided similar energy efficiency. At the time we selected, propane was 3.75 a gallon and rising (with no end in sight) so we went with GT. The delta cost for the GT system (above the cost for a HE propane heat and electric AC system) was $15,000 for the heat pumps and loop plumbing (including pumps) plus $17,000 for digging the pit. The pit excavation should not have cost as much as it did but it is a 12 ton system and the hole was gigantic (120' x 48' x 6'). We live on a mountain and hit a bunch of boulders that required special equipment to get out. Rocky soil also required a 1' base of stone dust to cover the loop piping. The total cost for the GT HVAC system including all ducting was $50,000 plus the pit excavation cost of 17K. It is a large investment and I would only recommend it if you plan to live in the house a very long time. My heating bills are great - maybe 300 dollars maximum a month during peak winter for an 8500 square foot home (5900 living and the rest a condiitoned but unfinished basement). Make sure that whatever equipment you choose can be maintained by more than 1 very qualified HVAC company who has many years of GT experience. In my area there is only 1 GT company who has over 20 years of experience but I am stuck with them for maintenance. There have been times when I wanted to fire them but cannot. Local competition is a good thing. Also - if you build a tight home make sure that you consider ventilation and dehumidification in the HVAC design. I wound up adding both a whole house dehumidifier and energy recovery vent after we moved in becuase we had basement moisture issues as well as stale air in the winter. Tight homes are great for energy efficiency but can create health issues too. It is easy to deal with as long as you plan for it. Good luck with the build.

Sounds like the aux is "stuck on" happens alot to heat sequencer (time delay) relays. Need to have them checked, also, aux will run a lot if the heat pump is not running right, low on freon, etc.

lots of reasons. some you can solve by lateral moves, others not so much. so think of this. you work at pizza hut. a customer comes in and wants to eat there, but brings their own pizza. offers to pay you to cook it..but minimal payment for use of your tools expertiese ect. sounds crazy doesn't it. but to the pizza hut worker/mgr..it is insulting, cheap and not something they would be willing to do. so how to get them to do it...overpay them. where is your profit from what you saved online now? and hopefully, before they slid your pizza into their pizza oven..the didn't spit on it. why...cause its human nature. think about some wisea$$ comming to your job and expecting you do do whatever you do..for lesser cost, cause they got a deal. people want to save money..we get it. and online prices look so much better than actually paying for the things you don't see when you purchase your equipment from hvac installer. we have experience, insurances, support if things go wrong. even then for you online shopper... who warranties the equipment? sure you can go online & warrenty with mfg but that leads to second question...who services the unit? the guy you hired to install it? see...when you 'think' you know more than the company you hire..it leads to some very human responses. hvac company will charge you a premium price to install equipment you purchase from someone else. they will hesitate to do the work..then as things go wrong..you'll pay over and over for undercutting them in the first place. so..think it would be simpler to hire one company to do the discounted profit install and another to do any work later? ahhh in a perfect to you world. we talk to each other..and in my area we all know who will jack us, pick apart every move we make..and who has the faith in us to just let us do our jobs. we charge them accordingly. ever wonder why one bid is $xx higher than the other one..your personality tips us off. so we know going in..that it will take longer than usual due to interference. so pita charge is added. we call it different things, but it is the cost of doing business with someone questioning every move due to some half baked idea that they know more than us. sure you can hire some hack..save a few more bucks..but we make really good money going back and straightening out these jobs. really good money. what you save upfront...you pay in the long run times 2 or 3 times more. this company who agrees to do work on the side is stealing from the company owner by doing work on the side. want to hire a crook to do your install? think of what they risk by doing this..losing their job..and having a hard time in the hvac community cause now every owner knows they can't trust them.. hey but you got a deal! good techs, are paid well by their employers and would NEVER do this. a company that agrees to do an install of online equipment..is either the low ball guy who does it fast bad & cheap..or you lucked into a good company going through a slow time who needs the work. the latter being about as common as wings on a pig. install is as important as equipment. you'll read us commenting upon that over and over. good equipment & bad install..you get crap. problems over and over. I'm in the trades. While I don't do hvac, I am licensed and have experience. Even went to school for it. I go to heat pump association meetings & know all the players in my area.and how they all gossip like a bunch of teenagers. so last summer...I was ready for my central install. ran all my duct, inside conditioned space, built fur downs for duct. converted my linen closet into heating closet. platform installed & sealed, supply plenum ready to be installed. Return sealed & filter rack installed. I had heating system(ahu) delivered & we sat it in place, did all the electrical. did electrical & pad for condensing unit. ran copper lines. ran wire for tstat and had tstat installed. condenser delivered. because I can buy from my local supply house, the first company I called to do the start up was realate to supply house manager. (and start up was ONLY to braise the copper lines & check refrig charge..sub cool & super heat) first cost quoted to me for this hour and a half job $1000. break down that cost for two guys. next price..$1050 getting the picture yet? and keep in mind this was just for using torch, gauges & maybe a little 410. so I did it myself. took me an hour. in the rain. borrowed torches & tank of 410, used my own gages. paid my friend a couple of hundred for use of torches & the lb of freon I didn't use. but..see..I know what I'm doing. you..you really don't have a clue. folks will always buy online, but if you check back with them..or read posts later from them...then you hear the issues. we hear them all the time. but..do what you will..its a free country. I'm not losing work on this...just giving you the benefit of my experience with this. best of luck

I'm leaning towards just heat pump with heat strips. That should be fine for your area. If you plan on keeping it that warm in the house as you say in your OP, I would get the Bosch Inverter heat pump as it produces heat clear down to about 5-6 degrees ambient and very efficient at what it does. Then use the strip heat as you need it. I don't know that you'll find a contractor though for this for a new construction job as Bosch just recently came to the Houston market a few months ago. The distributor network for Bosch is in it's infancy... so there are pros and cons for choosing this brand. For what it does / how it does it --- it's a game changer for my market. (Katy, Texas area) As a comparison --- an average run of the mill single speed heat pump will probably struggle once temps drop into the 20's for any significant amount of time. They are efficient when compared to strip heat (utility bill cost wise) but there are higher limitations with those. I've gotten email notifications from my electric provider that they are estimating my next electric bill at less than $50 for November. This may wind up being my lowest electric bill ever for my power rate of 12 cents per KWH. With that said, I keep it quite chilly during the winter and my house is all electric (no gas at all). I shut it off at night and really just use it to take the chill out of the house in the morning. If it gets really cold here, I will probably just heat the main part of the house over night --- as I have it attached to a 4 zone duct system. (This is to explain the how and why my electric bill is so low -- design of the HVAC system is a big part of it.)