Certainly keep your hot water system . Install any type of heat emitter you choose in the new rooms and find someone who will install split system ductless in those areas for A/C . GFA cannot and never will be as efficient nor as comfortable as Hot water heat . Make sure whomever you have do this performs a heat loss calculation for the old part of the home as well as the new . Install a new boiler that is efficient . Do not bite on a salesman's hook of a 90%+ boiler ,. These are modulating / Condensing boilers and will not ,I repeat will not acheive their advertised efficiencies with the high temperature return water that you have . See Lowered Expectations , John Siegenthaler (google it) . Get a nice boiler around 85% AFUE and install a variable speed pump and outdoor reset . Simple , inexpensive and the best you could want in your house . Don't be a prey item for someone who thinks he is intelligent ! Good luck with your Reno and if neccesary I can steer you to a professional blog that can assist you in finding the right man for this job in your area .

Also check out Thermal comfort : a 40 grit perspective for consumers .

I would suggest looking behind door number 3. If you install the mini-split heat pumps you will find that they will heat very nicely and do an excellent job on the cooling and dehumidification as well. If I was looking at a mid-80% efficiency boiler I would suggest a Buderus.

The Space-pak system works well but doesn't have near the technology of the mshp or the efficiency. They tend to be noisier as well due to the velocity of the air. If the install isn't very precise they can really sing a tune. The best brands of mshp are Fujitsu, Mitsubishi and Daikin. I'm sitting in a room heated by a Fujitsu 12 RLS as I write this. I'm a fan!

Can you describe your 5 year old boiler? It would be a shame to get rid of it.

Yes, there's another option that hasn't been mentioned.

You can install a geothermal liquid-to-water heat pump, keep all your cast iron radiators (why would you want to destroy the heritage value of your home!), keep your existing gas boiler as a backup, add supplemental hydronic fan coil units for both heating and air-conditioning and NEVER have to install ducts, HV or mini-splits - ever!

This system would be energy efficient in the extreme, require very little maintenance, greatly increase your resale value and not alter the heritage value of your home. Heating, cooling, cast iron - no ducts, no mini-splits on the walls!

Might be more expensive up front but may also be WAY less expensive over the life cycle of the system.

SR

Thanks to everyone for the comments so far; keep 'em coming!

Responses:

@HeProfessional: I will check out the links. I admit that the second one was pretty much incomprehensible to me, but that might have been my late reading time. I'll give it another try. I was worried about the return heat too. What is the maximum temp return heat for efficient condensing boiler operation? Also, does using the boiler for both heating and household hot water make any difference?

I would also love a reference to someone in my area who know hydronic and ductless HVAC as most of the information I'm getting so far is from GFA experts.

@Jackfre: My research has produced the same results; I think Spacepak is probably off the list.

@mike_home: It's a Peerless MI series. Link is below.

@fsq4cw: I'll look into that further. I did some research but rejected this option as we live in a flood plain and there are very strict rules on excavating needing to incorporate "make up" soil. Maybe I was too hasty.

Here is a link that might be useful: Peerless MI series

fsq....

You must get a commission on sales of ground source heat pumps, it's the only recommendation you ever make.

I think you've said you live near Montreal, an area with long and very cold winters and cheap electricity. It's great that you're so enthusiastic about this topic, but you should understand that many parts of the US have much higher residential power rates than you pay. You're not talking about small cost differences but very large ones, not just operating costs but also including the high equipment and installation costs of what you're suggesting.

When gas service is available, it's usually the best choice for heating. In whatever configuration, whether to heat air or to heat water.

Look at all the mini-split options in addition to high wall mounted indoor units. Also available are ceiling cassettes, and relatively easily-hidden small air handlers that can serve two or more rooms. Some kind of mini-split retaining the hydronic would be my choice having lived with hydronic, forced air and mini-splits.

Re: WinnetkaJAK

High conductivity Bentonite grout is almost universally used and should not be a problem as "make up" soil. You may have been too hasty or misinformed.

Re: snidely

I only receive commissions on those I sell or projects I consult on. May I sell you one?

I am in Montreal and in fact do recommend other systems as well, particularly when clients do not want to invest the capital that geo demands. Some projects are hybrid solutions involving natural gas and geothermal or air-source technologies.

I do understand that most parts of the US have higher electrical rates but have never come across a region where geothermal is not recommended by our industry due to electrical costs. In the end the client does what's best perceived for them, I'm just presenting another option.

I do appreciate your comment (sincerely).

SR

Clever comment, fsq. I too have never experienced a situation when a salesperson doesn't recommend their most expensive product, at least to start. I love salesmen, they make things happen, but the fact that something is recommended doesn't mean that the recommendation is sound.

Also clever word choice in calling the up front money an investment. Where gas is available and electricity is not cheap, getting a ground source heat pump is not an investment, because there's no return. It's a cost, and often a very expensive one.

Heat pumps are mostly unknown in my area for cost reasons. With $1.20/therm gas and $.30 per kwh electricity (top price tier hit with only about 350 kwh per month), you'll understand why.

snidely:

Where are you located?

SR

Coastal California between SF and LA. Check rates for PGE, the top tier is 35 cents per kwh (I was wrong with 30) on monthly usage over ~ 550.