Home heating question: Is the best the new thing actually best?
September 3, 2021 7:48 AM   Subscribe

We want to replace our "boiler" before the snow flies. We're interested peoples' experience with the newest tech, the condensing boilers with an AFUE of 95% or higher.

The house is an ordinary 3-bedroom split level in SW Connecticut, built in 1968. The heating system is gas-fired, baseboard hot water. Our inclination is to go for the latest and best in technology, but I've seen warnings that the newest units sometimes don't live up to the hype due to subtleties in system design and installation, and are more likely to require expensive repair than the older, tried and true models.

So, tell me, do you have one of these systems, and how well do they work for you.
posted by SemiSalt to Home & Garden (7 answers total) 3 users marked this as a favorite
 
I'm not sure exactly if you are asking this question, but there are much more efficient systems than 100%. It's counterintuitive, but a heat pump can get efficiencies of 300%.

Now, heat pumps are mostly for forced air furnaces. I'm not sure if the technology has been adapted to boilers. But if you're interested in the newest tech, a heat pump furnace is newest and most efficient!

https://www.youtube.com/watch?v=7J52mDjZzto

here's a long nice video about it! I love nerd-out videos on tech like this guy. One problem with this guy though is he doesn't always share "the other side" of the issue. So, here's another youtube on why... they might not be the future, also.

https://www.youtube.com/watch?v=GhAKMAcmJFg He basically says heat pumps don't work well in drafty or poorly insulated houses.
posted by bbqturtle at 7:56 AM on September 3, 2021


It depends...

For condensing boilers, installed costs are ~25% more and unit lifetime is ~25% less, so your HVAC engineer will need to make a numerically-based case that you will make that back in reduced fuel consumption, after also factoring in the expense of scrupulous maintenance.

If it's not a slam dunk, a mid-efficiency boiler may be the better choice for your home at the moment.
posted by Glomar response at 8:29 AM on September 3, 2021


a heat pump can get efficiencies of 300%.

That's for an air source, ground source can get more like 400%. They do cost more and they are not suited to everyone's land however. Some heat pump systems can also run in reverse to provide AC in the summer as well.

Whichever system you are getting it is worth considering whether your house is up to spec on insulation. Bear in mind not all energy efficiency improvements will pay back however, but some might, depending on what you already have installed.
posted by biffa at 9:49 AM on September 3, 2021


Best answer: If I were you I'd be more focused on getting off gas mid- to long-term vs. increasing efficiency the highest possible amount. Insulation and heat pumps keep getting better (and the climate keeps warming!), and the less you're using your boiler the less return you're getting on your investment.

What this means is getting a mid-efficiency boiler and putting the money you saved towards installing a cold weather heat pump when you replace your AC condenser. Later on you can improving your home insulation more broadly, which can be cheap (better door sweeps), midrange (replace double-hung windows), or expensive (passive house retrofit).

Once you have a heat pump you will probably reduce your boiler usage significantly but still have it for backup on super cold days, and if you address your insulation overtime you will eventually not need it at all.

tl;dr: Don't buy the best boiler ever, buy your last boiler ever.
posted by goingonit at 10:09 AM on September 3, 2021 [1 favorite]


Best answer: I have one. The installers did a poor job such that they needed to come back six times in the first year. Even after I found a competent heating company, it has not been as reliable as my old 1960s one (like, it will be unhappy about something so once I realize I'm freezing I need to go down and tweak something) and parts are indeed super expensive. I'm looking at replacing it now after only eight years, when the original one lasted 50 years.

It's entirely possible I've had a particularly bad experience due to the poor installation and bad luck on my particular unit, or that companies other than Buderus have less expensive parts.
posted by metasarah at 10:21 AM on September 3, 2021


Best answer: Condensing boilers don't generate condensation in their flue (and the noted efficiency gains) until the water returning to the boiler is under about 140 degF. This may or may not work well with your baseboard heaters.

If you always need hotter water to produce enough heat at the baseboard, you wouldn't see any gains. If that the supply temperature can be adjusted lower, such that the return from the baseboard to the boiler is less than 140, they could be an advantage. If the boiler can adjust its supply temperature to increase with very low outdoor temperature (to make sure you have enough heat in the dead of winter), but back off when it's merely cold, not frigid, a condensing boiler could also work well.

Sorry, I work with commercial systems, so am not familiar with the controls options for residential units, but the temperature ranges are thermodynamics and psychrometrics, so those should be consistent.
posted by BevosAngryGhost at 11:08 AM on September 3, 2021 [2 favorites]


Response by poster: The combination of the last three answers suggests replacing the present unit with something similar, and I think that's the right thing to do.

More background: I'm 75. We're not going to stay in this house long enough pay off the upfront costs of a major improvement. We do feel pressure to do good for the planet, but we also want reliability. We don't want to be cold for two or three days waiting for the fixit guy or a spare part. It's interesting that in just 6 replies, we got one case of dissatisfied user and one solid reason why the condensing unit might not deliver on its promise.

Thanks to everyone who took the time to answer.
posted by SemiSalt at 10:01 AM on September 5, 2021


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