What Happens When Steam Pipe Insulation Is Removed? It's Worse Than You Think

When I first bought my house the entire basement had zero pipe insulation. We also had zero insulation in the walls and drafty windows. No main vents either so the whole system had to vent through the undersized radiator vents.

I swear it felt like we had radiant floor heating. The basement was in the 90's and by the time the radiators warmed up the floor was already toasty.

I installed 1 inch insulation around the pipes and it made a huge difference. Basement stays in the upper 50's now and with main vents the steam hits the radiators in a fraction of the time. I may go with thicker insulation some day…but probably not.

I'm a huge fan Ray and so I will share that condensate in a main near the boiler does not cause steam to collapse (unless it's cold and lying in a valley of course—not what we're talking about here).

In fact, when those drops of condensate form they usually get turned back into steam by all the hot steam flowing past them. I have seen it with my glass pipes (similar to the illustration you have in your video, except without all that water lying in the bottom).

Yes, as you get farther from the boiler the condensate will flow at the bottom of the pipe, but you are also getting all the condensate from all the radiators at the bottom of that pipe (the farther you go, the more of this "radiator formed" condensate you get. And yet the pipes don't knock, and the system isn't overwhelmed.

I'm speaking of one-pipe here which is the more drastic of the situations (due to all the extra "radiator condensate" the main sees). With two-pipe it's even less of a concern since the radiator condensate follows a different route, not through the main.

If the lack of insulation were important to the operation of the steam boiler, as you indicate in your video, you would experience all this water hammer every single cold startup. But this doesn't happen (at least not in an installation even remotely following manufacturer design). The cold pipe gets warmed gradually by the initial steam produced by the boiler.

And those uninsulated pipes condense WAY WAY more steam during cold startup than they do when they are hot (yes, even when uninsulated). We know that a pipe gives off a little heat, but a pipe alone can't heat a space of any size, you need radiators.

Absolutely, uninsulated boiler room pipes might (might) be putting heat where it isn't wanted or needed, but they do not cause hammer or other harmful conditions.

I wouldn't presume to give you a lesson, Ray, just sharing what I've seen, thanks!

I usually work with large multi unit single pipe systems. Last year a member of my Coop board asked my to look at a 3 floor unit that he owned that had water hammer. I determined immediately that it was because the pipes in the recording studio under construction in the basement were not insulated. Unfortunately, his contractor sealed up the ceiling and the two mains pipes running to the front extremes of the building. One of which was running next to a cold brick wall. It would cost over $10,000 to remove the ceilings and replace them and more to insulate the brick wall. I conducted a number of test and determined that if the mains temperature was below 120F at steam start up, there would be knocking. I also determined that when the pipe temperature reached 188F, all of the radiators [which had different venting] had received sufficient heat. I installed a system that uses what I call " Active Balancing" to turn the boiler on when the mains pipe temperature reached 120F and the thermostat called for heat and shut the boiler off when the mains pipe temperature reached 188F even if the thermostat called for heat. There was no more water hammer and the apartments were satisfactorily heated according to the tenants. One of them had complained to the the HPD and took the owner to court. The only disadvantage to this Active Balancing is that on days that it got suddenly cold after a warm spell, there would be slight knocking on the first cycle and it would take about 45 minutes for the heat all of the apartments.

I would wager there was a pitch problem that caused some water to sit in a length of main. When that water is warm or hot it's fine, but if it get too cool it will collapse the steam and cause hammer.

Insulation will help that issue, but is more of a bandaid than a cure because it just reduces the number of startups where the sitting water is cold. The problem will still occur on actual cold startups, whereas in a correct system I think any startup should be silent, with or without insulation.

I will now state for the record that I think insulation is generally a good idea, but its real purpose is to keep heat going where you want it, and not where you don't need it.

There was no pitch problem. If there was, I would have said so. The pipes were just too cold because of high convection due to poor or no insulation.

@ChrisJ

Bigger warm up load with uninsulated pipe or pipe in a cold crawl space.

Any space cooler than 212 deg will cause the steam in the mains to condense.

We could consider any steam that does not condense in the radiator as "lost steam" but if it condenses in the building it will help heat the building to some extent.

But if the pipe is uninsulated the loss in the average basement of 55 degrees is probably negligible. If the pipe is in a cold crawl space, run outdoors (which is common in steam plants and colleges) or uninsulated then a lot of those btus are lost.

But how is the boiler producing more steam than it does with a warm system?

The burner(s) are still using the same amount of fuel. Where's this extra condensate coming from that doesn't exist with hot piping while all of the radiators are condensing the steam? The boiler didn't become bigger because the piping is cold.

That's what I'm not understanding.

If anything, you'd think insulated piping would cause more condensate because you're returning the condensate back hotter. No?

I don't know, I don't get it I'm sorry.

That I understand and agree completely.

This is why even most of my returns are insulated. I'm just not understanding how it could ever cause hammering unless something was already borderline and not right.

I'm not sure who's right or wrong on this, I'm just trying to understand everyone's perspective.

Good discussion. My particular situation was 60 feet of 2-inch mains - all insulated, including take-off pipes. The basement (cellar) was not warm during the heating season (northern New Jersey.) I removed all the insulation so the space is now comfortably warm and dry. No measurable increase in burn time for radiator heat in upper floors. No hammer or boiler surge. So, for my situation, insulation removal was a win.

A few rambling thoughts… first one is that so long as the steam is condensing somewhere in the heated envelope, the heat is not lost. Problem, of course, is that it may not be where you want it to be. In that regard, insulation can be regarded as a control measure. There is no more steam being produced — the same amount is produced, it's just no condensing where you want it to.

Now as noted, on startup in a cold system, condensate will form in the cold pipes. If they are insulated, less will form — if they aren't, more. How much more? Too many variables — but more. That can cause water hammer problems on startup, but not when running, if the pipe slope isn't adequate to handle the extra condensate, and it's worse, of course, if the piping slopes down back to the boiler, as the steam is pushing ne way and the water is trying to go the other. Insulation can help in these situations, but it isn't fool proof.

I've never managed to see the point in insulating wet returns — there just isn't enough heat present, even with pretty hot condensate, to make it cost effective. At least in my mind. And I honestly see no point at all in insulating dry returns in a two pipe system since, if everything is working the way it should, there should never be steam in them anyway — although if they carry condensate, which they almost always do, they will get warm. But like wet returns, there just isn't enough heat there. To put a number on it, the heat in the return condensate is only a few percent of the heat released in the radiator or radiators which are served by the return., assuming the return manages to cool to say 110 or so F. And again, this heat isn't really lost so long as the return is in the heated envelope.

This explains something I noticed but thought it was just a coincidence, as I had been making other improvements to the system. After I repiped my boiler, I started replacing the pipe insulation. starting at the boiler and working my way out from there. The basement has always been the warmest place in the house in the winter, but when my wife nixed my plan to put sand on the floor and have beach parties down there, I figured I might as well insulate my pipes and stop wasting money heating a space where I spend maybe ten minutes a day on average. Surprisingly, after insulating every pipe I could reach, including the returns, the basement is still the warmest place in the house in the winter. The change is barely noticeable. But what I have noticed is that the upstairs raditors heat up faster and the bedrooms are much warmer than before. If this is what insulating your pipes can do for you, it's definitely worth the time and money. I recommend it to every steam heat DIYer, and pros should really be selling re-insulation jobs, especially to customers who complain of cold upstairs bedrooms. The work itself can be done year-round. In fact, it's much easier to apply insulation when the pipes aren't blazing hot.

@ethicalpaul

Beware confirmation bias/placebo effect

We are all guilty of that.

All of us………. without even knowing it.

Insulation is a no brainer. The problem I find is there is remaining asbestos from unlicensed removal of asbestos. Cannot touch it (last Man syndrom) I tell them to get removal certified. They seldom do.

You're right I'm not old enough.

But I'm well aware of White Rabbit. 😉

Kind of strange how I like a few Jefferson Airplane songs, but no Jefferson Starship songs.