Should we replace the cast iron boiler in our 1968 home?

Asked by Kathy L
Mount Holly, NJ

Brick one-story house is 2600 sq ft with 45 year old gas-fired cast iron boiler with baseboard hot water heating and 3 zones. Separate AC and separate gas hot water heater (ready for replacement). HVAC (employee of local gas company) said not to get talked into replacing the boiler, but is this still good advice? We don't want to waste energy/pay too much for gas/electric use. But we don't want to replace anything that doesn't need replacing.


Sean Lintow Sr

Answered by Sean Lintow Sr

Naperville, IL

SLS Construction & Building Solutions

September 25, 2013

Well Kathy that is a good question and quite honestly it is a pretty hard one to
simply answer.

While the person recommending you keep it may think that is the best answer, it really does come down to you.

  • Are there ongoing repair issues / how many more years will it remain trouble free?
  • How long do you plan on living there?
  • Is it still operating as efficiently as possible?
  • How well do you stay up on the maintenance?
  • Why do you want / are considering a replacement? Do you want something more efficient, less maintenance issues, have comfort issues which you think maybe caused by it?

In short I would get a whole house energy audit done and get the system checked along with the ductwork. You might find that there are some minor things you may wish to take care of first which would allow you to get a smaller unit or maybe an all in one unit which can heat your water and take care of your space heating needs using your baseboards. Or maybe you'll decide to go with a hydronic based furnace and AC combo.

An experienced auditor in your area that knows these systems should be able to crunch all those numbers for you and tell you which one would make the most sense based on initial and yearly costs while also balancing that with your needs and wants. That is, if you want efficiency and lower yearly costs, they should tell you the upfront and give you the best options based on the efficiency and yearly costs instead of fixating on initial costs which many tend to do with paybacks, etc.

One other item to strongly consider is how are these existing units vented. If they are atmospherically or power vented, I would strongly lean towards replacement with a direct vent unit.

My last caveat is do not assume, nor allow the contractor to assume that a replacement unit should be the same size. Not only are many units oversized, but by increasing the efficiency you actually reduce the size needed.

  • For example a 50k unit at 60% efficiency produces 30k usable BTU's whereas an 80% efficient unit would be producing 40k.
  • So if you only need 30k, a 40k unit would give you that and then some extra.


For more information:

The Find A Pro directory on GreenHomeGuide lists approximately 2,500 energy auditors and raters across the U.S. Click here to find one near you.

Read Sean's blog post "Energy Savings & Efficiency 101".


Tagged In: energy efficient heating system

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