You should ask someone local that can see the proposed construction of the house (construction drawings) and to calculate heating and cooling requirements.

New construction must have a heating and cooling load calculation done in order to determine the proper sizing. A system that is too big is just as bad, and some times worse, than having a system that is too small. You need to ask the HVAC contractor for a copy of the load calculation and have it explained to you. If he says the calculation is not necessary because he has many years of experience, then look for another contractor.

My initial reaction is a high efficiency 125,000 BTU boiler seems over sized for a 3500 sq. foot new construction house. Does the 3500 sq. feet include the walk out basement area? I also question the need for a 60 gallon hot water storage tank. I tend to want to keep things simple and would suggest you consider a stand alone hot water heater.

I assume the reason you are going with propane is because natural gas is not available and you want baseboard and radiant floor heating. If that is the case then it would make sense to install your our propane tank in order to get the best pricing.

Thank you both. I am sending an email with some of this exact wording asking for the heating and cooling load calculations...! I also asked for a quote with a stand-alone water heater.

Will these calculations also determine the lengths of the baseboards?

Yes, the 3500 sq feet does include the walk out basement area. The basement would be radiant heat and the other two levels are baseboard. So I guess that does require propane?

I had once heard or read that having both radiators (like baseboard units or otherwise) and in-floor radiant heat in the same house could be problematic. Because the ideal water temperature for each was different and so any given temperature setting could be good for one type but not for the other. This could be wrong so check with the experienced radiant heating person involved with your project.

If you want baseboard radiators and radiant floor heat then you will need some type of boiler. The fuel sources could be natural gas, fuel oil, or propane. Each has it pros and cons. I assume the will have duct work and AC. If that is the case you could install a forced hot air system at a much reduced cost. I do believe mixing baseboard and radiant heat may cause problem with a condensing boiler, This is something you should discuss with an experienced HVAC contractor who installs these type of systems and not just a plumber.

Hi Mike, thanks for your input. We will not have ducts. We are using a couple mini splits for AC in the bedrooms. We have been advised against forced hot air because it is supposed to not work as well in Vermont, though I can't recall exactly why. Maybe because of the extreme cold dry air in winter,

I will ask about concerns mixing the baseboard and radiant heat. Is the concern that they require very different temperatures of the water?

Something that you should be aware of to make more informed decisions regarding HVAC particularly in new constructions, is that HVAC is undergoing large transitions in both technology and efficiency.

You absolutely should have a proper, detailed room-by-room heat gain/heat loss calculation performed.

Heat pump technology has made gains that can now compete with natural gas or propane if designed properly - even if electrical rates are quite high.

The efficiency of a system is best examined as 2-separate part, source (boiler, HP) and distribution (fans, pumps).

As you are considering a hydronic distribution system for in-floor radiant and baseboard heat at a minimum, the place to start would be with the possibility of doing this with a heat pump, such as an air-to-water heat pump that 1-integrated system can provide space heating and air-conditioning, as well as domestic hot water (DHW) - all with just 1-integrated heat pump system.

The other consideration that impacts efficiency and design is what indoor water temperature will you be designing for, particularly in heating mode. The lower the water temperature, the greater the system efficiency and the less it will cost for energy. This is a separate question from hot water temperature and air-conditioning water temperature.

What it does mean is that for in-floor radiant, the floors have to be designed for tighter tubing spacing with lower hot water supply temperatures as well as larger panel emitters, again for lower supply water temperatures.

There is no problem regarding different water temperatures required for different zones due to different media. However, lower overall water temperature results in lowest operating costs.

You would still have to incorporate fresh air exchange via an ERV or HRV.

IMPO

SR

SpacePak Hydronic Heating & Cooling

Yes, what I heard was that radiant emitters (radiators of whatever kind) have optimal water temp range that differ from what's best for floor embedded tubes or pipes. Basements typically have low heat requirements anyway, you may do better passing on radiant heat there, may not be worth the cost.

Winter air gets dry when heated, no matter how heated, because the warmed cold air has low relative humidity when warmed to an indoor temperature. In a tight, well built new home, forced air versus radiant should be the same in this regard. You may need an installed, permanently plumbed humidifier either way.

Hi Isabelle,

Using mini splits for cooling parts of the house will work. I imagine Vermont has a short cooling season.

There is no reason why a forced hot air system could not keep a newly constructed house warm and comfortable on the coldest day in Vermont. Whoever told you a forced air system will not work well is not giving you good advice. Perhaps it is a heating contractor who specializes in boiler installations. Baseboard heating is very nice. The only drawback it could limit furniture placement in rooms. Radiant floor heating is even nicer. However it doesn't work will all types of flooring. Think about that before make your final choices.

Thanks everyone. I'll look into all the different permutations you've noted, including heat pumps. I've already learned a lot here, which will help me have the right conversations.

I'm a fan of hydronic baseboard heat and radiant heating for comfort--especially multi-zone systems. That said, LP gas is an expensive fuel source in most areas (which could get considerably more expensive if a carbon tax is implemented.) It's worth the effort to consider a range of alternatives so you can make an informed choice.

Hydronic baseboard heat can constrain your furniture layout, so give some consideration to that when laying out the heaters in each room.

Fresh air make-up requirements for your home will depend on the size of the home, how tightly it's constructed, the number of occupants, and the operating mode (on/off or continuous) of the exchanger. Check with your contractor to see how they arrived at the particular make/model for your home.

Thank you, Charles, I will ask about the fresh air make-up requirements, and I'll sound like I know what I am talking about thanks to you!