Tarm wood fired boilers have an available water storage tank that stores lots of energy. Better sit it on 4" of eps foam

Not sure I understand. Can that be used with an oil fired burner?

The Tarm came to mind because the water in the tank doesn't change, it just has coils that run through it.

I actually found them on that site, seems there are called indirect hot water heater. Yet if they don't really save energy I'm not sure if it's the right move for me. I'll have to do some more research. Thank you for your help, you've pointed me in the right direction

So help me out here... what's the purpose of the tank? Is it to save energy? How would it accomplish that?

If your concern is energy waste, the tank won't help.

Energy in = energy out.

Energy in = oil

Energy out = heat to your home + efficiency losses of your burner + heat losses from distribution system (pipes running through spaces that don't need to be heated)

Adding a tank doesn't changed that equation much - more likely makes it worse.

Energy out = heat to your home + efficiency losses of your burner + heat losses from distribution system + heat losses from the tank

You can decrease energy usage by: sealing air leaks, insulating distribution/return lines, replacing your burner with one that is more efficient.

If your concern is wear and tear on the burner, a very well insulated storage tank, along with a heat recovery unit may reduce its operating time, but this would be unlikely to pay off as it would be an extensive (and expensive) upgrade.

AIW is correct.

It's possible I'm missing something (like short cycling losses or efficiency loss when running at less than full capacity) but that seems unlikely. I'm not seeing how a storage tank changes anything.

I was thinking that if the tank could hold the water temperature for long periods of time without making the burner kick on, I would save on fuel oil. I keep my heat very low in the winter and it helps in conserving oil, however, the burner still kicks on regularly to keep my domestic water at temp I think.

My burner is also in a framed room inside my garage, maybe it would be money better spent to add insulation on the walls around the burner unit

You want to be a little bit careful with that as well. If there are electronics in that room that control your system, ensure they can successfully operate in the new room temperature.

You could gain some efficiency with a heat recovery unit on the air exchange for the burner - use the heat from the exhaust to preheat the incoming air to the burner.

So, the thing here is to not guess.

There are several things to look at - but you have to keep in mind there are only three general areas:

1. Energy loss of the home. (windows, walls, ceiling, floor, doors) Also the heat distribution system (pipes in unheated attic and crawlspace) as well as walls of burner unit that you mentioned.

2. Energy efficiency of the heating system (how much heat goes up the flue).

3. Relative cost of fuel - Is a cost thing, not an efficiency thing. Electric resistance heat is almost 100% efficient, but is far more expensive than natural gas, for example.

Can you tell me the efficiency of the boiler unit? Also, what part of the country do you live and do you have any alternative fuels (like natural gas) available?