We are building a home that will have radiant floor heat on the first floor and basement in the slab. We would like to use the boiler for all the heat. The questions is about the second floor with carpet on the floor. Will anyone notice the difference in comfort between the heated floor and a less expensive baseboard heater?

They will notice. We use European panel radiators sized to the radiant floor design temperatures for the main floor. This will allow simplified boiler controls and give you room-by-room control with dial thermostats on each radiator.

http://www.badgerboilerservice.com/radiators.html

I'm confused. Are you saying that the heaters you are recommending are better than baseboard heaters or are you saying that those are used as supplemental heat?

radiators are better than baseboard, and can be sized to operate with the radiant temperature water, so any cost differential is usually mitigated back in the mechanical room.

I also like low cost radiant ceilings in carpeted areas if you have flat ceilings. avoids the wall clutter. same complexity reduction as the panel rads.

as for the floor temp, as long as you are heated below and carpeted floor comfort will be fine. though carpets are an air quality and cleanliness complexity....

What Badger is trying to explain is that when you add carpet over a radiant infloor system using the same boiler temperature there will be a significant loss in comfort heating the room. Carpet is a good insulator. To over come the resistance , the temperature of the water feeding that area would need to be higher than a non carpeted area. To do so would require adding controls and components to your system. Baseboard heaters can operate at the same temperature and provide heat to the space without adding a lot of cost to the project.

I may be looking at this wrong, but I wasn't too awful worried about the heat flow through the carpet. The house will have a conventional furnace, and the carpeted areas of the house are on their own zone. The radiant heat was mainly a comfort concern, although I would like it to be capable of heating the whole house. The thermostat would likely be set slightly lower on the gas furnace, so if a cold day prevented the floor from heating the whole second floor it would be able to keep warm still.

Also, we are talking about the second floor and attic of a house, so there will be a "stack" effect that will be helping the heat travel upwards anyway.

If you are going to the expense of radiant why do you need a forced air furnace.I would redesign your a/c loads around mini-splits or a vrf system.Anytime you have ductwork ,you are going to have efficiency losses.Multiple temperature zones in a hydronic system are not a problem if designed correctly

I looked at AC with the mini split system and didn't see any real cost savings. I'm looking at $15k for two independent 16 SEER systems of 2.5 tons each.

The furnace is basically free since an air handler is needed anyway.

There may not be a cost savings upfront but over the life cycle of the equipment there could be a tremendous savings in energy.Have you looked into the cost of gas vs electricity in your area. A heat pump with a fan coil would not be much more and would give you duel fuel capabilities of heating your home.

OK, you have my attention. I am particularly interested in the ducted mini split systems. I think I would need 3-4 4-inside unit models of approx 18000 btu each.

You should check out Daikin Altherma, this is a heat pump that can not only heat and cool using space conditioning type of equipment but is capable of delivering hot water for radiant floor heating as well as domestic hot water. Solar can also be added. Another manufacturer Mitsubishi City Multi "S" series is a possibility. Both of these systems are by no means inexpensive but the old saying is "You get what you pay for"