Multi-family HVAC update options?

vitel2

Hello,

My apologies if this topic is covered elsewhere. If so, feel free to point me to it.

We are about to acquire a 10+ unit multi-family residential building in Chicago built c. 1970, and are exploring options for updating the HVAC.

There is currently a hot water boiler (three actually, and the original ones) for baseboard heat common to the whole building. Also, there are common domestic hot water tanks (gas paid by the owner), and a single gas meter so all tenants' cooking gas is paid by the owner as well.

We are exploring options for reducing the high gas-utility expense. Ideally, all of the tenants would pay for their own gas use (they are currently metered individually for electricity). The cost of doing so is the main question we are exploring.

The main unknown: the logistics/cost of running individual gas lines to each unit and giving each a separate gas meter.

Here are some of the options we are considering:
1) Keep the system basically as is, but update it for greater energy efficiency.
- Install two new high efficiency condensing boilers, and update windows and insulation for better heat loss performance.
PROS - a) minimally invasive; b) can provide 15-30% reduction in heating costs (we are told).
CONS - a)total gas expense is still paid by the landlord; b) individual units won't have individual control (except for a thermostat controlled shutoff valve for heat/water in each unit); c) AC would be available on with in wall/window units.

2) Try to individually meter each units' gas and provide each with a traditional forced air heating/cooling system.
PROS: a)gas expense could be completely removed for landlord (huge)- even tankless hot water could be installed in each unit; b) each unit would have their own climate control.
CONS: a) constructions costs of running new gas lines and soffiting sheet metal duct work. b) highly invasive with collateral construction costs; c) future costs of maintenance on multiple systems vs a single building-wide system.

3) An electric based heating system
- This is tricky in my mind because of the high cost of electric heat. We live in Chicago with harsh winters and expensive electric supply costs. I can't imagine shouldering that expense as a tenant, although I've been told that there are a number of nice buildings that utilize primarily electric heat.
- Also, we would have to run 220 lines to each unit.

4) Mini-split system.
PROS: a) minimally invasive; b) individual unit and in-unit-zone control; c) high efficiency
CONS: a) given Chicago's extreme cold snaps in winter, they cannot be (according to code) used as a "primary" heat source.
- One possible solution would be to keep the existing boiler/baseboard system for backup and/or use in extreme cold (possibly triggered by an outside temperature sensor). Then, of course, we haven't eliminated the heating gas expense, only reduced it. To what extent, is the question.
- Another solution would be to supply supplemental heat via electric baseboard heaters.


There a few moving parts to figure out here.

I'm sure that many people have experience with this very issue, and I'd love to hear about it!~

Thanks!

nicholas bonham-carter

Are the three boilers staged? How are they controlled? What is their age? What is the average size of a typical apartment?
I would do a heatloss survey on the building now, (with, and without insulation/window upgrades), and compare that to your present actual energy use, (Slant/Fin.com). A Flir attachment for a smart phone would enable you to see major heat leaks in the outside walls.
You may find some problems with the present system, which when solved, and in conjunction with envelope improvements will make the heating/DHW cost more affordable.
Your baseboard radiators may not give you the efficiency you seek, as they may require higher temperature water to provide heat, however, a condensing boiler might be advantageous in producing water. Certainly, keeping the hot water will be more cost effective than putting in forced air/ac.—NBC