I am looking at buying a slab on grade schoolhouse built in the 1950s in southern Ontario and am trying to decide how much of a nightmare it would be to heat more efficiently. It has been converted into living space and is currently heated by natural gas fireplaces with blowers in each the two large former classrooms, and with electric baseboards in the foyer and smaller rooms which would be bedrooms. There is no boiler. From reading this forum, I see that I would want to look at better insulating the building too, but what is there now doesn't seem like much of a heating system to begin with. Would installing a natural gas-run boiler and steel panel hydronic radiators be a better long term solution than the existing electric baseboards or would I be better to look at radiant heating over the existing concrete and terrazzo floors? Or are both options that would just depend on information that I haven't given here?

Just trying to figure out where to begin even thinking about this potential mega project. Any input much appreciated.

 

what makes sense depends on your local fuel costs, electric vs natural gas. typically natural gas is cheaper though.

You'll really want to think about the envelope though. If the floors are not insulated, for example, you'll probably want to build up a bit to add some insulation.

Thanks Rob. I do intend to look into insulation as well since I'm sure there is lots of room for improvement.

Natural gas is definitely cheaper where I live. Assuming I improve the insulation, I guess what I'm really wondering is if putting in a gas boiler and the plumbing required to run wall radiators would be as big a job but less efficient than in-floor radiant. Perhaps this is difficult to answer theoretically, but what factors should be considered?

Again I am wary of being dependent totally on fossil fuels to heat my radiant project.  That is why I have been wondering how solar can lessen my load.  I do have abundance of wood to burn but as I get older it is some work that I am willing to do.  Here we burn propane and it is not cheap.  Electricity may be cheaper .13/kw ?  But future PV panels could offset that cost?  At what expense?  etc etc.  But the main concern in this day and age is fossil fuel dependence.  What about electric boilers? Wood boilers? 
regards  jeff

panel radiators will be, most likely, a somewhat higher temp so less suited to alt energy as Jeff discusses. Radiant would probably be a lower temp, slightly more expensive, but a much bigger project (though if you build up the floor anyway, it is less of a big deal).

It would also likely be quite a bit more comfortable. But if efficiency is the only question, I would size the radiators for low temp (120 Deg F.) operation or so, and go from there. That would be the most cost effective way to maximize fossil fuel usage. If you're looking to "future proof", then radiant is likely a better choice.

Given that Ontario is rolling out Time-of-Use rates for the whole province, I think the perception that "gas is cheaper" needs to be revised.  Retrofit is usually more challenging, but if you can maximize your power usage to take best advantage of the T-o-U rate, I'd bet electricity would be your most economical choice.  But that's a pretty broad statement and subject to the particular details and challenges you face in the home.

If you use natural gas or straight electric, then the type of delivery (forced air, floor radiant, wall radiant) makes almost no difference in efficiency.  Large radiating surfaces do help efficiency with geothermal.

Time of use rates should help geothermal since the water aspects of it allow easier heat storage.

Every situation is different, but when budgets aren't infinite, on retrofit 1950s architecture the payback for improving the envelope is often much better than with high-efficiency heating systems. A tighter better-insulated building with a smaller mid-efficiency boiler/furnace will use less energy than a leaky drafty barn with a higher efficiency much larger heating system. You have to know your budget to break it down as to what the short & intermediate term solutions should be vs. the long term.

If it takes an 8 ton geothermal system to heat it in it's current state you can buy a lot of insulation & air sealing for the installation price. Reducing the heat load to something like 5 tons might be very reasonable by comparison. But spending even more on load-reduction and using an even smaller-cheaper boiler or air-source heat pump instead... If you build/buy a heating system sufficient for the load before fixing the building envelope you inevitably end up with an oversized system, which typically means higher-than-it-should be operating and maintenance costs, along with the very real up-front cost.

It's always an iterative process figuring out what makes the most sense, but investing in building envelope has a longer life-cycle (insulation doesn't often suddenly die and need replacement), and reducing the load lowers the size & price of the mechanical systems required to support that load. (In the extreme, it eventually makes the absolute efficiency of the mechanical systems somewhat irrelevant too.)

Do the current heating systems (in all their decrepitude) work? If yes, do you have any utility billing data on the place? Knowing where you're starting out will give you a better idea of what the eventual destination is, and where to spend first. Some peops like to take mega-projects on all at once and be done with it (and I can appreciate that sentiment), but it can sometimes be the more expensive path. If the heating system works I'd start in somewhere else and track it's operating cost performance against heating-degree-days as you fix stuff up.

Usually the bang/buck order of things on retrofits is:

*Tuning up/recommissioning the existing heating system bringing it to it's best possible performance

**Air-sealing the building

***Insulating the building

****Replacement heating system of higher efficiency

And of course there will be thousands of counterexamples that prove the rule. When you've maxed out on the first three, (which in your case is mostly the middle two) the amount of money left in the budget may determine where you go from there, but you'll then have a much better idea about the true target-size of the heat load will be and be able to choose the size & type of radiation more appropriately. In the longer run low temp hydronic delivery systems will be have more flexibility for heat sources than forced air or low-voltage electric-mesh-radiant etc. Electric boilers with high-mass slabs + tank thermal-storage may make the most sense for folks with off-peak rates at their disposal, but do the math, eh?