Pop the wall open to insulate the steam pipe or not?

Agurkas, dry steam is produced right at the boiler. It is the moisture content of the steam, should be no more than 2%. Are you seeing the boiler water level dropping quickly because the steam leaving the boiler is pulling water with it? The header should remove this water from the steam. The rad vents may be spitting because the rads are being vented to quickly, the steam entering doesn't allow the water to drain. The rad is pitched wrong, or the rad valve is not opened completely. The condensate from the steam condensing in the mains should be going down either the dry return or the wet return. From what I remember your boiler is oversized. The increase in the velocity of the steam because of this might be causing the spitting.

Shipping is a huge component of insulation cost. If you can find a local supplier and pick it up yourself it might be worth it. One of the big online suppliers is in West Paterson, NJ, but I forget which one.

Agurkas, I know you played around with that spreadsheet but the whole point of it was to demonstrate that the choice between 1" and 1.5" was anything but a "no-brainer."

I still feel a lot of the heat lost ends up in the home anyway. It has to.

I think insulating steam mains is not primarily about ROI or even efficiency. In many cases it's about preventing water hammer. ChrisJ is right, you can't consider heat lost to a conditioned basement as a total loss. Insulating can also help keep a conditioned basement from getting too warm.

The relative or marginal utility of pipe insulation is not dependent on operating hours or fuel costs. If a bare 2" pipe loses 168 Btu/ft-hr and a 1" insulated pipe loses 23 Btu/ft-hr, you can say the 1" insulation has a utility of 145 Btu/ft-hr. But a 1.5" insulated pipe loses 18 Btu/ft-hr. So the marginal utility of 1.5" insulation is just 5 Btu/ft-hr or 3.4% better than 1".

In other words, by choosing 1.5" insulation over 1" you are paying about 1.7x the cost for 3.4% more performance. The caveat is that installation labor is the same, and when you factor that in the difference in total cost between installing 1.5" and 1" may not matter much to you.

I think my last comment is the "Cliff notes" version. Why you would consider 2" pipe insulation at 2% marginal utility and not be putting the money into air sealing and insulating your rim joist instead is perplexing.

I am just going to chime in here with my 2¢..

I am also just a mere homeowner but I also chose to go with the 1.5" insulation. I did it not because of the extra R value, but because I could use the mitering technique and still have about an inch of insulation at the T's and elbows.

Granted, I could have saved money if I went for the 1" insulation but I would either have to buy all the fiberglass joint covers or just use rock insulation and ASB tape (which would look horrible). For me, it made sense, I am about 3/4 the way through the insulation job and it really looks great.

Also, about the steam condensation in the pipes..
Before the insulation, I never witnessed my boiler building any pressure. Now that the pipes are only partially insulated, I actually have seen my 3psi gauge finally climb to the 1.25psi mark. This tells me that the system is filled with steam (plus some extra for pressure) and the steam is not condensing faster than steam can be produced.

@TheRooster‌

I heat my house currently with around 1/4 of an ounce of steam pressure. Not sure why you would interpret pressure climbing to more than a pound as a good thing? I removed my 3 PSI gauge as it was useless but may install it with a valve just to test my Pressuretrol yearly to make sure it still works as a safety device. At 4 ounces my system gets forced into hold mode for 10 minutes to allow steam to condense and the radiators to cool a little as this only happens when all vents are shut and radiators are full.

I'm currently in the process of finishing insulating my returns. Dry returns are done but I want to do something with the wet return.

ChrisJ, the before/after picture was superfluous. You painted quite a word picture!

ChrisJ said:

When I insulated my piping in the crawl spaces, especially the tight crawlspace that I barely fit in I didn't do any cursing but I did do a lot of laying there feeling sorry for my self and pondering the universe.

This is a before and after of the worst crawl space though I still have not done the elbows yet. That may not look that tight but in all honesty I'm fat, and for me it's tight. The before picture everything is soaked because someone had drilled an 1/8" hole in it to drain condensate as it was pitched wrong. Lovely conditions to work in not to mention the bag of lime that was in the way. We all know how great lime is to roll in when you're all wet.

This is probably the funniest thing I read in a long time. Back in my days as an electricians apprentice, I spent many hours pondering the universe in crawl spaces.

I've found that Insulation to a steam system is the cherry on a sundae. In and of itself, it not going it's not going to make dry steam and will often not compensate for underfired burners, undersized and oversized piping. After, I get everything squared away with a problem, then, and only then will I reinsulate. Mad Dog

I am in the process of insulating my steam pipes (I'm going to go with either 1" or 1.5" thickness and most of the pipes I need to insulate are 2" pipes). I tried looking for videos explaining the mitering technique for elbows (and there is something similar for tees), but could not find anything. Would someone be able to share a link?

Thanks!