A lot is dependent on the design of the house.

Most people in climates like yours with radiant forgo any AC. Because you need a completely separate expensive system to add it. And you are already looking at the most expensive system possible for your heating. By a multiplication magnitude, not an additive one.

Put in the radiant floor heating in the second floor. You can always turn it down, but if it gets too cold up there and you don't have it...... Yes, heat rises, but heat loss through the roof is also the main sort of heat loss in the house.

Have you priced any of this out? Spending 30+ years of utility bills in advance, just because it is ”green”, doesn't make a whole lot of sense. Unless prices have dropped incredibly, you will never get a complete payback before the system has to be replaced. You may be surprised at how comfortable a well insulated home can be, with a standard and simple, forced air system. Then you get to have AC, because you already have the air handler.

Some people like radiant floors so they can walk on warm flooring.  It becomes a luxury as opposed to a functional alternative to forced air heating.  Personally,  I like forced air because it is quicker to control temperature and not get too much residual heat in the afternoon. But it seems people who have radiant tend to love it. If it were my home and I was already doing radiant heat on two levels, I would do the third as well.

We have radiant on all three levels — walkout, main and upstairs (and the garage) and love it. Here in the Rockies AC is rarely needed and dehumidification is not an issue. Having lived in the South so long, I really don’t like forced air which was a necessity there. I’m only half joking when I say was colder in the South (because of AC) than I am here. We do have mini-splits in the upstairs bedrooms and the main level master for those few hot summer days. Even on the hottest days, the walkout stays cool. Our upstairs us not open, but if I were you I would still run radiant upstairs because the incremental cost of adding that space shouldn’t be that much and you can keep that zone at a lower level.

Heat loss through the roof is not the main source of heat loss in the vast majority of new houses. Walls are number 1. Yes heat rises but having a thick barrier above the ceiling is not only easy, it is required by code. Walls are thin. And wall area is usually larger.

Typically, adding to attic insulation is measured in hundreds of dollars not thousands. It does depend on the technique - both attic style and insulation.

But going with common (and cheap) technique of an attic and unvaulted ceilings and then blown fiberglass means you can easily have very high R value at the ceiling. Like easily 5X higher than the walls. But typically it is 3X - because going higher doesn't help all that much.

Totally agree with Adama.

Use the 1/4 the money that you plan on using for the radiant and put in into insulation/wall construction. You will be very comfortable and save a lot of money.

If you are dead set on radiant, then of course, spend a few extra $$ on the 2nd floor - code will likely require it so the conversation is moot. You are already spending so much money anyway.

Hi, Brett,

Homes require heating, ventilating and air conditioning (HVAC) systems which address the climate conditions, the particulars of the home's construction, and the comfort and health of the occupants. The focus of most HVAC designs is the heating and/or cooling requirements; ventilation is largely ignored. Homes should, at a minimum, have a ventilation strategy to exhaust moist air generated by point sources (showers, range hoods, etc.) and to introduce fresh air. If you're not planning a heat-recovery ventilator, I suggest you consider one. They can be helpful in controlling indoor relative humidity. I live in a mixed-humid climate zone and I have dehumidifiers integrated into my HVAC system for "shoulder" seasons when neither heating nor cooling is required, but control of indoor relative humidity is needed. Most of those systems can be configured to introduce fresh air as well.

There is a tendency for folks to look at choosing between HVAC alternatives as a pick the highest return-on-investment decision. While budget is an important consideration, achieving a higher comfort level generally implies a larger investment. That's a personal choice.

Just a side observation - anytime someone is pitching a "more expensive than going with other alternatives" approach, the word "investment" pops up to sugar coat it. HVAC equipment is a cost, not an investment. Spending more gets more but the same is true with most things money is spent on.

We have in-floor radiant heat in my way-upstate NY home and love it. The house is very tight and is super-insulated and we also have a HRV system, No AC. On the hottest days, it becomes uncomfortable on our main floor, at night, it is rarely about 75°. The ground floor, where our home theater is located is very comfortable even in the daytime.

Our house will be 1 1/2 stories, radiant heat first floor only, geothermal system, electric heat pump for both heat and AC. We will also have very good insulation, windows, etc. Architect and engineers determined that in our specific house, we would not need 2nd floor radiant.

OP has mentioned he’s doing geothermal and in-floor radiant.

With 1-Geothermal Water-To-Water heat pump he can do virtually anything he wants to. Hydronic heating and cooling of type or variety, ducts or no ducts, in-floor or panel, fan coil or central fan coil heating and/or air-conditioning, domestic hot water (DHW), snow melt, pool heating - virtually anything you can imagine - if your wallet is fat enough!

(Are we allowed to still say, “fat” ! I don't care - "FAT"!)

IMPO

SR

2rickies - that is not the same of course. With your system limited description, I can say that you don't need 2nd floor radiant. Because you don't need first floor radiant either. You have a heat pump which is all you need.

You describe the most expensive option in every case - which sounds like wasted money to me.

I am not sure why you would do "very good" insulation and windows and then spend at least 3X what you would need for temperature control. At that point the insulation and windows should be "outstanding"..

Lomo - $5k to save $100k over time is hyperbole. Hyperbole is a nice rhetorical tool but isn't super helpful when trying to make rational decisions. It costs a lot more that $5k to make a house much better insulated than code and it doesn't save $100k over time.

No one who spends what it takes to build a new house today should ever have to sleep at 75 degrees. Somewhere below 68.

I get it - people don't like ducts/registers and they like warm feet. The truth is that with a tight house, the floor doesn't get particularly warm. And you need ducts/registers for a/c. If you think you don't need and won't ever need a/c - I suggest you ask people in Seattle about that. And to think you could have had it and saved a lot of money in the process.

I would say for insulation/tightness - expect to spend $10-$20k and recoup that in lower bills in about 10-20 years (unless you are crazy enough to be using oil or propane - then you might recoup in 3 years). It is more comfortable day 1 and it will mostly last the life of the house. Depending on the HVAC used, the initial outlay could be a lot less than that because you save on the HVAC install costs.

The other bonus is that you save on maintenance and replacement costs on the HVAC because it is smaller, cheaper and less freon to replace when fixes are made. And the last bonus is that your house stays maximally comfortable when the power is out or the fuel is gone.

@David Cary it's a GSHP, so it should last twice as long as a conventional heat pump, and it should be more efficient. When I said "very good," I didn't realize that descriptor would be taken literally as possibly inferior to "fantastic super-deluxe" insulation and windows. The insulation, windows, and doors are "outstanding." When we did the math on various systems that would work best in this project (which our architect, engineers, and so on, reviewed and analyzed ad nauseum), with rebates, the ground source system was only marginally more expensive than a more conventional system, and it was the most efficient for our building and its location, which is fairly unusual. One of my goals is to limit emissions as much as possible.

Should last twice as long.

A couple of facts that should be true.

GSHP costs more than ASHP even with incentives. Marginally more? - sure. Remember than incentives will be gone and also possibly the contractors that specialize in GSHP. Doesn't mean it is a bad option. But it is more expensive.

Radiant + A/C is wickedly more expensive than a/c alone.

So what you describe is the most expensive option.

With outstanding insulation, you should barely need HVAC. So then you are really spending a lot of money. Passive house doesn't literally mean completely passive but certainly close.

I am curious about your math. Not saying it is "wrong". But just curious. Our raters gave us a $100 a year savings with GSHP vs ASHP which means the only reason to do it is for hot water (and that is pretty marginal anyway). What about the emissions digging the trenches or hole? On radiant - how about the emissions in the radiant pipe's manufacture? You have to agree that sometimes incentives distort. Actually, they always do, that is the point. In the majority of the US, the GSHP incentive is not the ideal place for money given the tech advancements in ASHP and the pricing of wind and solar. Think of how many panels your house could have with that incentive. So you are taking advantage of an incentive but is a distorting one at least as far as where money could be going to do the best for emissions.

@David Cary I get that you're not a fan of geothermal systems. Yes, obviously there are emissions in the manufacturing process of every single option including renewables. But ongoing emissions will be lower with geothermal. Drilling a couple of extra holes when one is already drilling a hole for domestic water is not as big a deal (they are vertical wells). I've talked with a lot of people who put this kind of system in their homes (including radiant) and they find it comfortable and efficient. I really doubt contractors who work on gshp will be "gone" -- I don't see any evidence that the tech is going away, and as long as people have those systems someone will be making money working on them. I'd be more worried about finding contractors who work on a gas-powered conventional system 20 years from now.

We will be getting solar but later on. They like to have a year of data so they know what capacity we'll need. We won't be putting it on the roof, but in a field. I may also get solar battery back-up so we don't have to rely on a propane-run generator in a short-term outage (outages are frequent and sometimes long). Either way, in an outage, it will take less power to run a ground-source system.

Building a house, everyone decides where they want to spend and where they want to save. I think I made the right decisions, listening to the advice of the people who designed and engineered the house and its systems and are therefore the most familiar with what will work best there.

@brett corbett, meant to add, we will have ducts. What does your architect suggest? I don't know what your house design looks like, but that would play role in where you put radiant heat.

We are building with a GSHP, hydronic heat and also an air handler to match up with the water to water HP.

I would consider how much you would appreciate a warm floor upstairs. For us it is going to happen.

The situation is different though, it is not open to floor 1 and it is ~1080 SF

We also have a minimal cooling season.

The air handler can also add some quick heat in the heating season when needed, as the hydronics are best left to a set point for the season. It is slower to react.

Re: Kelly M

What heat pump(s) exactly (make/model number) will you be installing?

I’m asking this because although you could, it’s absolutely NOT necessary to have more than 1-GSHP for absolutely everything/every function (heating/cooling/DHW) - every variation and every combination. The main and virtually only reason, in almost every case for more than 1-GSHP in a residential installation would be for redundancy or for massive amounts of hot water. That could be all be handled otherwise.

If you are being told otherwise, you might be very ill-advised unless there are very special circumstances!

IMPO

SR

If you carefully read my post, there is only one heat pump mentioned. It can be combined with a water to air air handler.

In my case is is a Bosch 3 ton unit, matched with a Bosch air handler. It will cool, heat, hydronic, and has a desuperheater loop for the conventional hot water tank assist.

My brother's desuperheater loop got his water warm enough that he just left the breakers off to his hot water tank.

I'm DIY for virtually all of it and am well versed in the systems.

I chased around and looked at some of your other posts, and we are preaching to the choir so to speak.

I will over-loop it to keep the temperatures more favorable. An extra ton of loop costs me about $600 and is priceless once we are up and running.

I have the equipment at my disposal and about 100' irregular trapeziod of space to work with. Let's say 8500 sf?

My apologies, you are right, you did mention only 1-HP.

SR

Yes - if you are already drilling a well, then it can make GSHP more attractive. I was just giving you some crap for the claim about going for the lowest possible emissions. Overdoing things isn't really the best option for emissions. Obviously building a house in general is not the best way to do lower emissions which is why I think they should be as efficient as possible and not taking a sledgehammer to every component.

I really have no problem with GSHP other than its cost in the US (typically). If you are in an area where it is done often, already drilling a well and/or have extreme temps, then great. But, most of the time, in 2023 in the US, it doesn't offer enough of an advantage over ASHP to justify the cost including the federal government's component. I mean how many people like to call it geothermal when they know darn well it isn't real geothermal.

Hydronic systems do not really lead to a warm floor in a tight house. Because they don't need to run very much. This would be compounded upstairs - we don't run our heat upstairs (elderly guests - maybe 1 hour per night but other wise never) because our house is tight. It is warm enough from body heat and downstairs. If you crank hydronic heat up so that you feel a warm floor, you will overheat the house. Something to consider for such an expensive option.

We live in north central VT and our house has radiant throughout, in the basement and main floor (oil heated, we bought it like this). I'm now completely addicted to radiant heat! We did have to add a mini-split AC in our great room - with cathedral ceilings and western exposure, it becomes a heat box on those very warm/humid days (of which there have been more and more in the last 5+ years).

@fsq4cw this is awesome! Thank you for sharing, will definitely look into this

Re: tkin

You can also research the cost differential between Air-To-Water HP and Geothermal Liquid-To-Water HP after all the costs, rebates and tax credits are evaluated and compared. The big advantage of geothermal is that all mechanicals are indoors with an even longer life-cycle, no variation in efficiency due to outdoor air temperature and no defrost cycles - EVER! That is huge in cold climates with high energy costs, not to mention the wear & tear on an air-source HP switching back and forth between heating & air-conditioning in the coldest parts of the dead of winter. The effects of defrost cycles are completely under rated or not mentioned at all at time of sale when purchasing air-source heat pumps for good reason - they don’t want you to know!

IMPO

SR

I had never considered that before now, as I sat all winter under a split mini and listened to it go through DF cycles.

I think I may upsize my GSHP to the Bosch TW061 but keep the same 3 ton air handler. it is $2200 more for the larger HP. That's not much in the scheme of 300K in building materials.

Re: Kelly M

What make/model/features - exactly are you considering installing? Will your home have a mechanical room and basement?

I'm asking because it sounds like you might be installing a, 'Triple Function' GSHP. Full capacity hot water for hydronic heating, forced-air for heating and air-conditioning and a desuperheater for DHW.

SR

The heat pump is the Bosch green source CDi, model TW061 with a nominal 5 ton rating. That is a bit deceiving as that is the heat and cooling capacities from water loop and ground water systems.

The capacity is 54,400 cooling and 45,400 heating with a closed loop system.

It will have the heat recovery option AKA desuperheater plumbing. I will couple that with a standard residential water heater and Leeds standard circulation pump system to put hot domestic water where we want it.

The house sits on a full unfinished basement built with Insulated Concrete Forms (ICF), so it is really not unfinished other than the ceiling sheet rock. It is all conditioned space, there is no unconditioned space, no attic etc.

It has a generous mechanical room for the heating and cooling equipment, the water heater, the HRV unit and all other infrastructure.

I will use Heat Sheet R-10 Heavy in the basement slab to provide insulation and hydronic loop installation security.

https://heat-sheet.com/heat-sheet-heavy/

It is an easy to use 2x4 system that interlocks and acts as a vapor barrier as well.

I ran the house through LennoxPros Coolcalc room by room, and came up with :

25018 BTUh heating

21002 BTUh cooling

973 CFM

That seems very optimistic to me.

I will install 3/4" pex under slab where ever possible in the basement, save some footing and wall areas and an elevator pit. I was planning on 1' spacing everywhere in the home.

The main and second floors will have staple up 3/4" pex with aluminum shields, and I will use the staple up insulation methods outlined at Radiantec's extensive research library.

We are using staple up rather than warm board or lightweight concrete so we can install as "live" a floor system as possible. This will help with my wife's rheumatoid arthritis. I realize that I will lose the heat mass and stability of the other methods, it is a tradeoff we are going to make.

We are coupling the heat pump with the Bosch HY035 air handler unit for both cooling and the faster reaction heating.

It has plenty of CFM and BTUh capacity for our needs.

The vast majority of the heating will be done by the hydronics, and 3 tons of cooling is plenty when you look at the Manual J calculation above.

I will use hard ducting only for the HVAC, I can't see putting flex inside closed ceilings.

All the hydronic runs and also the ground loop runs are home runs to that mechanical room. I see no point in hiding fused connections in the ground or hydronic joints above finished ceilings etc. I made the equipment space generous for this reason.

The ground loops will enter the basement via 1.5" or 2" HDPE sleeves. I will install the loops so they can be isolated at the manifold if there is an issue, and spaced so I can replace a loop in the rare event of a failure.

All the manifolds will be built with copper ProPress fittings, and I will utilize mechanical unions at every valve so any failed valve can be readily replaced without completely draining and drying out the system for soldering etc.

I have not picked out the exact models in some cases but I have a little time for that.

By oversizing the HP in this instance, it will run in low mode for the vast majority of the time, at a better COP.

The same applies for the loop sizing. I will have enough loop so the entry temperatures will be more favorable. This too will improve the COP.

The house will have 10~12 KW of solar panels and is planned to be a net zero structure.

Does it pay off? It pays off for us far better than the average person who pays labor at every turn for these installations. I enjoy the design and implementation, the house design etc.

It is not for everybody.

Interestingly, I can tell when there is a defrost cycle and they are rare in my climate. Like once or twice a season rare. Surprised me since my last unit did it on a timed basis so much more regularly. If you don't have a basement (which tends to be the case in milder areas) you don't want units inside the house.

my brother's system is not in a basement. It shares a small equipment room with the water heater . It has been fine that way, it is a downflow GSHP with ducting in a crawlspace of a 1920's craftsman home. He added on that area and an attached garage.