So I have all of this info unfolding in front of me now.  It is becoming quite the head spinner...I'm sure the wife loves it even more

So here we are:  new highly efficient/near super insulated home to be built.  Heating zone 6, NE Iowa.  Single story house with walk out basement (to the north).  Front faces south, with as much solar designed options as I could do.  Triple pane u-.17 windows on the north (my views of the trees and hills are to the north). R-35ish walls, r-60ish ceiling, r-30ish ICF foundation, r-10-15 below slab (undecided).

Anyhoo, 1700 sqft up and down, so approx 3200-3400 total conditioned space.  Current load calcs have been around 26k BTU, but not sure if that is too high or not.  i have been using 7400 HDD.  I am hoping I can get it tested and reduce that amount even more. 

All electric, current rate is .1025 for first 600 Kw, then .04 after that for winter months which are Oct-May.  I believe it is .1025 during Jun-Sept. 


Here are the options.  The local utility has this very in depth spread sheet they provided to compare the different options, so i will use the numbers generated from that. 

The thought is to use GSHP with horizontal wells.  Use a DSH with that.  2 ton 2 ph WF with wells and DSH is running around 19k installed including HRV.  This is rated just under 20k BTU out, so a 7kw electric strip is added.   Less take credit of 30%, plus utility gives $450 puts me at....

$19,000- 30%-450= $12,850.  It is my understanding this will supply some of the hot water, but radiant in the basement slab is another thing.  I understand I need to go up 1 ton to provide for this?

So a 3 ton unit increases to $23,000, minus rebates above and you are looking at $15,650.  Puts out 27k BTu. 

Using my house numbers above, and using the 2 ton GSHP (using a COP of 3.8), it shows taking approximately $240 cost for the year.  The 3 ton drops to $225. 

Now for the ASHP.  In our climate it is not always the best.  However, the total cost of an 2 ton 2 ph 18 SEER system with electric strip in air handler is just under $12k.  Only about $700 total rebates here, so lets call it $11,000 total.  The spread sheet is showing that costing around $410 a year.  Basically a $170 savings over GSHP. 

12,850-11,000= 1850 cost difference.  /170= about a 11 year pay off.

My question is, are these numbers looking about right?

Now add the DSH into play.  My 2 things I am considering is a DSH with a HPWH as the holding tank/main take.  Only use 1 tank total.  The utility gives $500 rebate for this tank.   I have read many reviews about concerns of the tank keeping up.  I was thinking I would use an 80 gallon tank.  I also wish to use hot water drain collection.  My thought is the combo of the DSH, drain collection....the tank should preform pretty well?  or should I look into something like the Reem marathon tank? (again, use a single tank design).

Finally, the radiant option.  I am getting confusing info on this.  Some say larger unit (2 ton to 3 ton) some say just more wells.  The floor area would be approx. 1200 sqft for the radiant in the basement.  Any thoughts on the logical arrangement/sizing needed to add this into the equation?  The thought is to leave the slab exposed, stain and seal it for the finished floor.  There will be 3 bedrooms, an office, and a game room/movie room down there. 

Alot of info thrown into this post, hopefully its not complete confusion.  thanks

Why would the radiant option require more capacity or more wells?

i have a ge geospring hybrid water heater rheem also makes one, and it works out fine for me but you cannot have 6 family memebers all wanting to take showers 5 min apart from one another. i picked the ge one cause the element is not sealed and can be replaced not so with the rheem. but the rheem as slightly better efficiency. it was easy to install.

ya I do not know the reason for sizing up.  I have requested a more detailed explanation.

Another option I am toying with is a water to water hydronic geo pump to do full radiant heat in the house, and then a very small hp to do forced air cooling with a small air handler. 

i do not know if that is not cost prohibitive to that method tzerac. the seer rating is the air conditioning rating and wether a geo or conventional hp they are all more efficient in the air part than the heat part. plus you are adding ducts just ffor the air part.

How much cheaper is an air duct system just large enough for ventilation and AC (vs one sized for a full heating system)?

its really not. I think I will plan on proceeding with a water to air geo unit with a DSH to dump into the electric water heater (most likely Rheem Marathon), and then installing pex in the basement concrete to making it "radiant ready". Maybe add a boiler later. I am not 100% sure we will even need radiant down there.