I did a search but unable to locate this information. Here is the situation. I am building a new ICF house in the panhandle of Florida on a bay. House is sited to take advantage of a 10KW solar array that will be installed as well as geothermal using vertical wells 250 ft deep which is customary for the installs I have seen here. This is to be a 5 bdrm two story house with a lot of south facing impact resistant windows. Does it make sense to use zoned in floor (tile) hot water for heating the bathroom of which there are 4 or just stay with forced air all around. I would expect that zoning each bathroom would make sense. It is unlikely that any other room would be in floor but certainly using a desuperheater for hot water is planned. Also we don't typically live year round in Florida from Oct to May leaving the hot months unoccupied and AC turned up to around 83F to avoid mold. I am a licensed engineer by trade but not in mechanical. One last concern is that for the previous homes I have owned in Florida every HVAC contractor has always overestimated the cooling required in tons. Currently I live in a Hebel (aerated concrete to include roof) home and disagreed with the HVAC contractors on size informing them that the current HVAC 3 1/2 tons short cycles and I don't want the new one to do that. They just don't seem to understand how to calculate with either hand calculations of SW programs the heat load with high thermal mass and excellent insulation. My biggest fear building this new home is to get a geothermal system way oversized for out needs. Sorry to be long winded but the entire greenbuildingtalk site is a Godsend to me...

AC turned up to around 83F to avoid mold.

I'd use a standalone dehumidifier and not worry what the temperature rises to. Cooling the house just means you need to remove more moisture for a given %RH value. Also consider a timer such that it isn't running all day (once per day drying stops mold).

Too bad you are outside my AO (Jacksonville, FL)...we routinely build (and properly size) geo HVAC for ICF homes. Ours typically come in at 1200-1600 SF / ton.

I think you'll encounter difficulty finding a local HVAC contractor able to properly design and install infloor radiant tubing for bathroom heat. You may be better off with electric resistance floor heat timed to operate only when needed. Another cheaper option is ceiling infrared - we have one in each of two baths on mechanical crank timers - give 'em a twist on the way into the shower and it is nice and toasty 10 min later. Installed cost less than $100 each and a couple pennies to operate each morning. A modern ICF house shouldn't have particularly chilly bathroom floors.

I'd go with an internet-enabled thermostat with humidity control in at least one big zone. If the HVAC is properly sized and two or variable stage, it should handle humidity just fine, especially if you are mindful of air infiltration (test at key points during construction). If everything is done right, HVAC should be able to hold 80-82*F and sub 55% RH during unoccupied summer periods for ~$10 per ton per month, hardly a major expense in the grand scheme of things.

Your most important design consideration likely relates to the fenestration coefficients of the windows and doors. A room by room Manual J calculation should incorporate the exact values of the windows you choose.

A 10 kW PV array may well be overkill for a home unoccupied during summer.

Thanks for the input. The in-floor heat is for my SO. I will need to chat with a couple friends that had geo systems installed 8 and 4 years ago respectively and see what if they are all forced air or a combination. Electric in-floor would fine for our application but just looking at what makes sense. Geo heating the water and valving for the circulation appeals to me for efficiency. But if electric used on a demand basis would be a good plan too and is being considered.
JAX is the same latitude as Niceville so it is good to get engineer's input since the temps are similar year round.

I like the idea of 1200-1500 per ton. My one friend had 13 vertical wells @ 250 ft for his 4500 sq ft house which is a single story with bonus room over the garage. He plans to use 7 wells for heating his pool and I was surprised that he was using 6 wells for a house that size.

Windows and doors are definitely the weak point from a thermal perspective as I have calculated around 1480 sq ft of window/ door area which 600 plus sq ft facing SW right into the sun. Overhangs are seriously important for this house.

Not back to Florida for two more weeks and then I can get some answers to questions I have.

I am very familiar with solar PV systems my background is systems and electrical engineering and the price of both inverter and micro inverter systems have come down so much in the last 3 years that I can now afford it. If this was 2011 I would never consider an array that large but hoping since I have unobstructed views to the SE-SW that my KW generator on a grid tied system with net meter will help keep electric bills reasonable.

All input is great appreciated. This is too expensive a house to make a mistake on.

Biggest issue I have is trying to pick the right window/ door package since this is a significant cost.

We don't plan to move from this house until we have to for health reasons. It is designed for us to age in place with all door widths 36" and elevator which are not as expensive as most people think...

We've moved away from closed loop in favor of open loop with reinjection - just two bores into the deep high quality Floridan (not Floridian) Aquifer. That pretty much guarantees entering water temperatures of 70-75 year round. Closed loop systems can't provide that.

Reviewing the data I could locate indicates a temp of 69-75F in this area. I know of no one here that I have met that uses open loop systems but I am only talking to those companies that friends or acquaintances have used thus not exhaustive. Understand that the closed loops will gradually transfer to the mass they are in thus the advantage of an open loop system. Don't you filter the water coming in to not contaminate the system and how deep do you normally to reach your water source?
Good information I can understand how you can achieve higher performance with a consistent entering water temperature...

Open loop systems tend to require more pump energy than closed so the operating cost may be similar in spite of consistant entering water temperature. Because of the passage of 100's of thousands of gallon through the system each year, the general feeling is if you need a filter (other than a coarse sediment blocker) then you should go closed loop.

Joe makes good points; we work to minimize pump energy by recognizing appropriate pressures and flows needed for open loop geo.

> Don't you filter the water coming in

The more serious problems that ground water may have in terms of geothermal use cannot be removed with a filter. Ie, pH, hardness, etc. And they cause more issues in warm climates.

I have a low water table since I am maybe 50 feet from the bay/ 8 ft above bay level that this house will be built on but don't see how I could employ an open loop system even though that would be more efficient.

Is there anyplace where I could locate a comparison of what cost to install geo in floor heating in 4 zones would be compared to using electric in floor heating for those same 4 zones?
I can assume that a forced air solution would be the most economical way to go but I am willing to trade off performance for comfort of a warmed floor.

Work it out using a load calculation, cost of each alternative's delivered Btus; typically figured on a million Btu basis. Ballpark annual cost via Equivalent Full Load operating hours for your area and the cost of electricity.

Having considered in-floor heat I'm aware of two distinct problems: 1) Very few HVAC contractors in Florida install it. 2) ICF wall require temporary bracing during concrete pour. Braces are typically screwed down to slab...I couldn't figure out how to guarantee brace screws wouldn't pierce in-floor heat tubes.

I am curious how the ICF pour will be done as well. My assumption was that the floor would be done after the first floor was poured. That may not be the case. Regardless of whether the floor is poured the outer wall bracing is going to be in sand. In this area I have seen the ICF walls built on footers with and without a floor dependent on the contractor doing the work.

I do have a question from a comment you mentioned before. I recall you mentioned you are doing mostly open loop systems in the Jax area. Can I ask how you are doing that? Meaning is a well dug and water pumped through the system then returned or returned elsewhere? Not everyone has a pond or lake or bay to dump into. I do have a bay as the house lot sits on the bay but it is too shallow to use for entering water (I think that is true anyway). Appreciate your input as no one I know of here has done open loop systems. Open loop would certainly be more efficient.
Thanks

We draw water from the Floridan Aquifer and then reinject it back to that same aquifer via a second well ~50' away. This became required for all open loop systems via a Florida Administrative Rule change during August 2014; but we've been doing them that way for several years.

I reviewed data here for the Floridan Aquifer and it seems to be not that deep. Will discuss with the geothermal contractor. Seems like an idea fit and I can understand the efficiency given the EWT doesn't vary much season to season.
Thanks I knew of the aquifer but was unaware that it covered this area too...