Converting central boiler to furnaces (75 unit property)

[Brad Weiner]

I am evaluating a 75 unit apartment complex (2 buildings) with 2 boilers that heat the units. The owners currently pays gas bills and the expenses are very high. I am considering converting the units to individual furnaces to reduce the expenses and remove the boiler. That said, I am trying to determine how much to assume per unit going from a central boiler to furnaces, including the duct work, for +/-75 units. Thank you 

[Larry Yinger]

It may be worth it to look into boiler replacement.  There are such things as 90%+ efficient boilers.  Some even rate at 98%.  If the boilers in your units are older, say pre-90s, the payback on the replacement could be relatively quick.

Quick, dirty math here, but $5-10k per unit wouldn't be unreasonable.  You would have to do all of the units that are fed by the same boiler, or you will still need to run your boiler.  So assume 40 are fed by one boiler, you'd be looking at $200-400k.  I would think you'd not only need to add ductwork to a space that presumably doesn't have any, but also run electrical circuits the new unit.  A boiler replacement could be had for a fraction of that.  Payback could be as quick as ten years with a service life far greater than that.

With that being said and knowing nothing of your system, you could do different things as well.  You could convert your boiler system to solar hot water which would pay back incredibly fast.  You might also look into variable refrigerant flow (VRF) if you want to add individual heat and cooling to the units as well.  VRF would likely require electrical upgrades.

More details (steam or hot water boiler, mechanical space in units, etc...) would give us a better idea of how to offer guidance.

My suggestion, talk to a reputable commercial mechanical contractor (or three) and have them propose to you options that list payback durations.  I don't think if I were in your shoes, that I could make a case for adding a ducted system.  I'd be happy to look things over for you as well.  That is the world I live in.