Boiler Confusion - Please help

Constantin

... I'm a fellow homeowner who just finished his home renovation and spent a lot of time on getting the place well-insulated. That's what I'd focus on in the short term. Insulation can be retrofit even in extant walls with dense-pack cellulose being a economical option. Once the place consumes less BTUs, your boiler choices can be narrowed down to the ones that meet your needs.

If you insulate the roof properly, you may end up with a lower heat loss with the space in use than you do now with the space being just storage or whatever. Fiberglass is notorious for allowing air to pass through so unless the deck between the living space and the attic is well-insulated and sealed, it may be a huge heat sink.

One inexpensive and effective way to weigh your options is to contact your gas utlity or energystar.gov to have an energy auditor come out and take a look at your home. With a blower-door test and a heat loss calculation in hand, it will be much easier for you to figure out what your best insulation options are. Once the house loses less heat in the winter and gains less heat in the summer, you get two forms of payback, which is less resources needed to heat/cool the place and smaller systems tool.

In the long term, it's a great idea to go with a condensing gas boiler if you have a tight house and lots of radiators to hook it up to. Venting it out the side will save on the installation cost, where and when it's legal to do so. Some towns and states are apparently thinking about restricting the locations, clearances, etc. of direct-vent piping outlets/inlets, so it may be a good idea to fully understand what the local situation is. A call to the local inspection office would clear that up. Plus, with the right model, you can always install them in the attic space when you build it out - they work just as well up there - and that gets around the whole DV issue.

If you want to heat with oil, there is one condensing oil boiler on the US market, the Monitor FCX. I have a low-temperature non-condensing boiler in my home and am very happy with its performance. Due to its low exhaust temperatures, it vents into a lined chimney.

Paul_50

I've had several estimates for a new furnace. My house is 1892 with hot water radiators. Only Kitchen, Bath and Laundry have insulated walls. Attic has wool insulation, which is not very effective. Windows have storms or are new wooden double pane low E. Sq. ft @ 2700 – 3000. I live in New England.

All three estimates sized the boiler similarly, between 160 and 175 input. I’m leaning towards the larger size b/c we want to eventually heat the third floor. My current gas boiler is 30 + years old and the gas water heater is 5 years old. Both vent into the unlined chimney.

2 guys want to stay away from the direct vent furnaces. Their reasons - because the water heater still venting into the chimney will have to be lined anyway, the fact that the boiler is 10 – 15 feet away from the exterior basement wall, that the system is to complicated, and that for the price the 10 % efficiency difference does not out way the cost of the furnace for many years.

1 guy who we haven’t received his quote from is putting together a few options. Direct vent with water heater. Direct vent and line chimney for water heater and lastly boiler venting into chimney. The highest efficiency that all three can give with this type of boiler is @ 83.2%.

My questions:

1) How much of a difference will 10% efficiency make compared to the extra cost?
2) Who the heck should I believe? They all have convincing arguments.
3) For the input that I need is @ 83.2% the highest for boilers that vent into the chimney?

Any help is appreciated!
Paul

Uni R

Is your boiler operational?

If your current boiler works, I'd see about getting your house insulated as best as possible. It would be the wisest way to start investing in efficiency.

Mike T., Swampeast MO

With iron radiators I'd truly suggest looking at condensing/modulating boilers and an indirect domestic water heater.

You'll avoid the cost of lining the chimney unless for some reason sidewall or new vertical venting cannot be used.

Cost will most likely be higher, but the cost of chimney lining (particuarly if tall or offset) can be extremely high.

This class of boiler thrives with cast iron radiators. You are almost certainly guaranteed significantly greater energy savings that implied by AFUE ratings.

Add some more insulation to the attic and you'll be on your way to a quite rapid payback of any increased cost by using the condensing/modulating boiler over a conventional.

If the heating contractor balks at using these "new boilers" find another heating contractor!

Joe Brix

Your WH might have a few years left

But with today's fuel costs, I get a condensing boiler with an indirect HWH. Better effciency and better fot the boiler to be used year round. Since the condesnser vents with PVC, you'd not need an expesive liner. You might look into running the PVC up the chimney if you have easy access.

jeff_51

gotta agree with mike

water heater efficency's are only about 75%, so a water maker is a very nice option, and those radiators are "radiant" heat and should be run at a lower than 180degree temp if sized that way. Seems like most EDR's I do, have the rads able to run about 140degrees when I compare with actual heat loss. This is of course where the condensing boilers really shine. It is after all what they were made for

Darin_3

Tjerlund(SP?) makes a sidewall vent kit that will adapt a lower efficiency boiler and make it sidewall vent which will eliminate the chimney if u use an IWH. The initial cost is kinda pricey but it seems to work well. Sometimes with the increase in efficiency, relability is compromised. good luck