Here are some questions/clarifications.

When you say radiant heat, do you more specifically mean under the floor radiant heat? Because good old fashioned radiators are technically radiant heat too.

Do you need AC in the home too? Where do you live? If you need typical AC, then you will need to install the ducting system for that. And the air distribution system for AC is basically capable of running heating/cooling with a furnace, vs just cooling only with an air handler (that's the fan part of the AC indoor system).

So with an AC system, it is a lot more costly to add the expense of a boiler and all the piping system for it, and the radiators, than to just do a furnace. Boilers typically use natural gas (or propane or heating oil)

There are some underfloor systems that use electric. This may be what you have in a smaller space like a bathroom. To do electric floor heating for an entire home may have a higher cost of use than using gas. That can depend on where you live, what you utility rates are, and the price of gas vs electric.

So there are a lot of factors.

Basically, I would state that most parts of the country that need AC, it would really add a lot of cost to also have the radiant floors for the entire house.

And if you don't need AC, then it may be a good idea.

Thanks for the reply! Yes, I mean under the floor radiant heat. Our current radiant heat is a hydronic system, I believe, and not electric. It was here when we bought the house and only in the kitchen and bathroom which had been added on later.
We will also need AC, but if we do baseboard we will also need AC too so no matter what it will be two systems with only AC running through vents. We're also hoping we could put some sort of humidity system into the vents for the long cold winters when the house gets really really dry, but that's a whole other topic. We're in Mass by the way. Anyhow, I'm wondering if this is common to do or not and if not, why? Is it just the sheer cost or is it performance too? I've read about doing wood over radiant but not carpet and I imagine that can be a problem? But I'm just guessing. Thanks in advance for any other feedback, tips or input!

Radiant heat is expensive and that is why it isn't common. It is perfectly fine and generally considered better than any alternative.

For most people, when they look at the cost, decide to do forced air heat. Since that is drying, a humidifier is added. Then you get lower cost and humidity control.

I am going to throw some wild estimates out there to give you something to think about. 3000 sq ft house with 2 units - $15k for decent stuff (installed, new house) that includes forced air and humidifier. Just a/c alone - $12k. Hydronic - $30k so $42k for both forced air and hydronic. So most people decide that $27k is too much. Now - people can DIY hydronic for much less but barring that, the install is expensive. Baseboards are cheaper but I don't think you even see that used much (I live in NC and we certainly don't see that.) I've seen one hydronic system on a foreclosed house that was improperly winterized. The only system I've ever seen and it caused water damage.

forced air is the way to go. If you don't like it dry make sure you have a dehumidifier. You could also consider having a heatpump which provides heat that isn't so hot and dry. How much do you pay for electric?

I'm surprised to hear about the forced hot air. I always hear people mention it in a nagative light. Typically it's come up in "we did forced hot air because it was cheap and regret it" amongst the people I know who have built in the past ten years. Do the humidifiers really resolve how dreadful the air quality typically is? I've always known it was the cheapest solution, but if money were not an issue (that's in my dream world, of course!) would you choose it over radiant floor heat? And don't get me wrong, I would love to learn that forced hot air with a humidifier will be great, I'm just still skeptical because of my family's dry skin/eczema. For background, we did a reno ten years ago and we did install baseboard and a/c and I recall numerous people agreeing it was the better way to go. But a lot changes in ten years! Lastly, I know nothing about heatpumps - what does that do? Thanks again for the input!

In a heating-only environment I would never consider forced-air heat in new construction or in a studs-out remodel. Hydronic radiators or in-floor is the way to go. It is most quiet and comfortable. Adding AC changes EVERYTHNG. If you are going to have two systems you add expense and that kills it for most people as others have ably pointed out. In addition to that, if you don’t have in-floor radiant, you double the amount of heating/cooling “equipment” in the room, meaning that in addition to the supply and return grills, you have to deal with the radiators.

The take-home message for the next paragraph is this, if you have a leaky house, including the ducts, you will have a dry house in the heating season and a damp, clammy house in the humid, cooling season. If you have a tightly-sealed house with good ventilation control, you will have a more comfortable home. It does not matter how the heat is provided via blowing air or flowing water, heat pump or boiler/burner. I will elaborate in the following paragraph.

Any time that you hear or see something that indicates that says that forced-air, hydronic, or heat pumps are inherently more or less drying, raise your shields because the horse-hockey is flying. The relative humidity depends on the temperature and on the amount of water in the air. That noted, you have to think about what affects the water in the air. Input is obvious, cooking, bathing and breathing are the big contributors. If you have a big crop of plants growing inside, that is a factor too. In Winter, water goes out of a home via air leaks. In Summer it enters via air leaks and condensed by AC evaporator coils. Forced-air heat is probably perceived to be dry because it is associated with leaky ducts. Duct systems that leak up to 5% are considered good though 5% seems like a lot to me. When these leaks are outside of the home’s envelope, and they usually are, they cause pressure differentials. Your in-attic supply ducts are blowing your nice, moist heated air outside which causes (winter dry) outside air to be sucked in somewhere else to make up for it. Return air duct leaks can depressurize parts of the house as well. That is why, in addition to less noise and having the air blowing around, hydronic is better in a heating environment. Whenever you design a house with a big blower and ducts, you are going to generate pressure differentials

Heat pumps may be perceived to be less drying because they don’t suck in dry outside combustion air, like a conventional furnace. A condensing furnace will not do that, but it will still have those pesky leaking ducts.

OP, note that your scheme to add humidity to your home in the winter with the conventionally-designed AC-only ducts, grills and blowers probably will not work. In order to add significant water to any indoor air being circulated in those ducts, you have to raise the temperature significantly. Even if you did not have to inject the ducts with heat at the same time you add water, you would not like much the cool air blowing on you.

Thanks, Ionized! That's some great info and it sounds like the real focus should be insulating the house and keeping it air-tight? Is that correct? And how does one guarantee that? Is it through the HVAC design or making sure your GC is doing a stellar job? Sorry if that should be obvious, I'm new to the new construction thing. Also, since my original idea won't work, is there any way to truly increase humidity in the winter without turning my house into a giant solarium of plants ;-)

Chris,
I hear you saying that you value comfort over the cheapest system.

I recommend a modulating furnace, with a top-notch humidifier and air quality filter system.

What is a modulating furnace? In layman's terms, It is one that comes on in stages, (lower amount of heat first, and then adds more if space is still too cold) and has longer run times with lower air force. What does this get you? The air is blowing on you at a more comfortable temperature, and not at full blast. The house doesn't get "heated up", then cool off to get "heated up" again. The fan runs most or all of the time. Why is that good? That means your humidifier and air filter are working most or all of the time too.

Does this use more energy? Actually it does not. It's like getting your car up to cruising speed, and putting it on cruise control.

To get a higher featured system with a modulating furnace will not cost you that much more than a good mid-tier system. But you will get comfort added for what you spend. A good HVAC dealer will be able to explain this to you and go over the costs.

Juliekcmo - thanks!! I can't even explain how dry my family's skin is and I'm sure it's not actually uncommon :-) So really, while money is a concern, we would be willing to spend more in this area to make sure our home is as comfortable as possible. We'd be willing to give up other finishes we could do later because we hate the idea of moving into the house and regretting the decisions we made here since they won't be as easy to fix.
So it seems like our best route is to talk to an HVAC dealer. But is it just that you want to talk to a dealer or are their HVAC system designers who won't be swayed by what the end result cost to them as a dealer will be? Thanks again - you guys are all a HUGE help!

A good dealer is knowledgable about how to design your system AND run his or her business to make a fair profit. I guess what I'm trying to say is that it is someone who is experienced enough to know how things work, how long it will take to do the install and startup correctly, to troubleshoot, and to get leave you as a satisfied customer. So they haven't underpriced the job, tempting them to cut corners or slack off if something goes unexpected on the job. Proper Startup and troubleshooting have a lot to do with how long your system can last.

I would try to call a couple of the better known dealers in your area who represent different lines. York, Trane, Lennox. Tell each dealer that you call that that you are building, and you need to review your plans with one of their more experienced people to design your system, and that you are flexible and will wait for the right person to be available.

How to make sure the house is designed in a way that maximizes your comfort and efficiency for the money you will spend? Unless your architect is knows how to design LEED houses, interview some energy raters ASAP. Get recommendations. Tell them you are building a house and you want them to review plans, set standards that are met by the contractor and test the house to be sure the standards are met. Standards would be for air infiltration and duct leakage, maybe more. They will also keep an eye on how well insulation is applied. If good construction practices are not followed (like taping all the drywall seams and sealing supply boots into the attic or crawl space) The house will fail a blower door test and they will have to fix it before you pay them.

No, I am not an energy rater.

Thanks again for all of the great feedback - it's greatly appreciated!!!

Chris,

Our current house has radiant heat radiators, and we are building a new house too. SAme dilemma as you. Building in Wisconsin. We MAY do infloor radiant hydronic heat on the main floor and finished basement....plus ductwork for AC.

One benefit besides is the boiler for the radiant heat can also be used to heat the residential hot water...from what I hear doing this is pretty efficient way to heat residential hot water. Question....any downside other than cost? To me the benefit of radiant heat is worth the extra cost....ALSO hear that radiant heat is a more efficient way to heat the house...maybe not enough to offset the extra cost...but it would help....comments from those in the know????

Hi all,
I was going to ask the same question as this post, so I am happy to see so much information. I live in the northeast, have a 30 year old furnace that we know we might have to replace soon. Delivery system is forced air. I have a lot of health issues, including respiratory problems and allergies. We have central air, so we have to have forced air for some months of the year. If we were to change our heat delivery, how much more expensive is radiant heat in the floor?

Has anyone heard of radiant skirting? I saw info about it on a UK site.

There is one other potential problem with radiant (particularly if you don't have ducts for A/C). If your house is tightly sealed there will not be enough ventilation (the air becomes stale or humid). If you install radiant consider the cost of adding a HRV system as well. Less of an issue if you have ducts for A/C since HRV can be added without too much extra cost. However, you will have to cycle the furnace blower on occasionally.