Steam Pipe Exposure/Insulation, Basement Warmth

goonsquad

Hi All,

As we're finishing my basement as a small play room for the kiddos, I'll be hiding roughly 2/3 of my 2" steam supply pipes behind walls. For some reason, my supply pipes currently have no insulation. So here is my strategy

• For any supply pipes behind walls, insulate them with 1" fiberglass pipe wrap
  
• I intentionally had my general contractor leave about 1/3 of the pipe exposed, as you can see in the pic. Our intent was to put a decorative metal grate in front of the pipe. My concern was that if I insulated all my steam pipes, the basement would be cold and require supplemental heat. You'll probably tell me that it's better to insulate, and provide for supplemental heat if necessary, since having insulated pipes makes the steam system heat more efficiently, especially for the upper levels. But for now, the plan is to grate in front, and I'm thinking maybe of a heat reflector in back (maybe curved sheet metal painted matte, so that the heat is reflected into the room instead of lost behind a wall. Or maybe just pipe insulation applied on the back side.
  

As you can see in this image, the steam supply for this wall is framed out to allow us to put a grate in front. Any thoughts would be greatly appreciated.

Jamie Hall

There are two reasons to insulate the steam mains. The first it the one often thought of -- it allows the heat to go where its usually wanted, that is the installed radiation. The second is much less commonly remembered: it speeds the steam flow through the mains and sharply reduces the amount of condensate in the mains, particularly on startup. This second consideration may not be a problem for you -- slow heating of the radiators beyond the uninsulated section, at least -- but the increased condensate may be, if there isn't enough slope on the mains to provide excellent drainage. If these are parallel flow mains -- that is there is a drip at the end to a wet return -- then the pipe slope must be at least 1 inch in 10 feet. If they are counterflow, however -- that is the main is sloped back towards the boiler, whether it is one pipe or two pipe doesn't matter in this context -- then I would want a slope of at least 3 inches in 20 feet, as a minimum. Otherwise the possibility of some rather dramatic water hammer is very real.

As to the amount of heat they will give off... not as much as you would think. A 2 inch main (almost 3 inch outside diameter) has an effective EDR of about 0.75 per foot of pipe, which translates to about 180 BTUh per foot. It will take 20 feet of main to produce the same heat as an ordinary 1500 watt electric space heater. If you really need heat in that basement room, a hot water baseboard loop running off the boiler with its own thermostat and aquastat will give far more heat at much better efficiency.

KC_Jones

If you want to heat the basement, then heat the basement. If you want to heat the upstairs then heat the upstairs. What you will accomplish here is slightly slowing the main house and not doing much to heat the basement. Most of that pipes heating ability is radiant, which means line of sight. Anything you put in front of it will slow down. Even then the output ability of a 2” pipe is minimal.

2” pipe is 2.375” OD, which is 7.46” circumference which equates to ~.622 EDR per foot. That gives ~150 BTU’s per foot of pipe. It’s not much, hide it in a wall in any way and it’s even less.

How many feet did you leave exposed and how big is the room you are trying to heat?

goonsquad

First, thank you so much for the replies. I'm continually impressed by the feedback I have seen (and gotten personally) on this site.

I'm not surprised by your responses, and am kicking myself for having my builder go down this path. Hopefully it's not too late to just insulate the pipes and sheetrock.

As it turns out, I need a new boiler anyway. I have been experiencing some roll-out issues on my 27 year old boiler, and I'm now told I need to bite the bullet. I'll talk to my steam guys about what it would take to run a new steam loop just for the basement. As it stands, I have no idea how my basement temp will change given all these changes

1. New boiler running more efficiency, with less heat production, less heat rollout
   
2. Insulated pipes in the basement, most of which are also behind walls
   
3. Sound insulation (using rockwool) between basement and first floor
   

I may find that my basement is way colder, and may require a steam loop. Any thoughts on cheaper alternatives like space heater or electric baseboard? It's a small area, roughly 350 SF. I have been consistently surprised at the cost and labor involved in maintaining the steam heat system. Maybe I'm just unlucky in timing, and that after 90 years, the steam infrastructure is just coming to a head. We've had to replace the returns, and remove/replace some steam supply steel pipes.

KC_Jones

If you are replacing supply pipes I would suggest you have other issues causing that failure. The failure of steam supply pipes should be considered unusual and the person replacing them should be looking for the cause. Wet returns are a different story.

I do hope you have a true steam expert working on your system, but you being here and a few of the comments being made leads me to believe otherwise. Also, what issue is causing the roll out that you need to replace the entire boiler. Typically a leaking boiler is the only cause for replacement.

For basement heat, you also have the option of running a hot water zone off of the steam boiler.

Jamie Hall

Your best -- and by far cheapest in the long run -- bet for heat in the basement is a hot water loop run off the boiler. It won't require a larger boiler than you would otherwise need, and can have its own thermostat. Indeed, you can install that now, running off the existing boiler, and hook it up to the new one if and when you get a new one. If your "steam" man can't figure out how to do this, you need a real steam man -- you don't have one.

Like @KC_Jones , I'm puzzled by the need to replace steam mains -- supply pipes -- or dry returns. Wet returns that I can see, but steam mains? Vanishingly rare.

And also, with him, I'm puzzled by needing to replace a boiler because of rollout issues. Rollout is caused -- in almost all cases -- by poor combustion settings, inadequate combustion air, poor draught on the vent or chimney, or woefully inadequate maintenance of the boiler -- none of which would require or even suggest a need for a new boiler. I'll grant that 27 years is getting on for a boiler, but unless it is actually leaking, that doesn't mean replacement. I'd seriously question your "steam" man on that one.

lowballj

I just insulated 75 feet with 1" fiberglass and my basement is still very warm. I didn't go crazy insulating everything and left riser Ts and a few elbows bare.
My suggestion is insulate as much as you can, especially near boiler piping, and then see what the temp in your basement is like before adding additional heating

goonsquad

Well, I called my steam guy to address issues w/ the rollout switch tripping, and when he did, he said it was probably the result of a cracked heat exhanger, something another person from the same company had told me earlier. However, we both observed that you could hear dripping inside the boiler, something which he said was of greatest cause for concern. As for the replacement of supply lines, yes, I did a partial replacement which was really more of a removal. In fact, I posted about this last month. There had been leakage, and some ugly looking repair work on the leg of the supply closest to the drip. The steam guy told me that this had likely been caused by a clog/erosion in the drip, which had then caused a backup of water into the supply. I'll admit to having been skeptical of this. Yes, we had our returns replaced maybe 6 years ago, and the original black iron was heavily corroded and dripping in many areas, but an erosion bad enough to cause persistent backlog into the supply lines (5 feet higher) seemed a little iffy.

So anyway, yes, based on that, I decided I needed that leg of supply replaced and got 2-3 estimates. Each estimate was in the range of $2-3k, but what none of the salesmen told me was that the leg I was looking to replace was no longer necessary in the first place given the last radiator had been removed, and thus I was able to get away with removal of ~20 feet of supply (including the rusted piece), and move the drip back by the same 20 feet. The fact that it took little old me to come to the realization that this was the better (only) solution bothered me, but what can you do. Generally, I do feel like I'm not being well advised by my company or others.

I chalk it up to the economic climage in my state/area. I live in NJ, and live in a town with TONS of building / remodeling activity. I've generally found that only the very large projects get the attention from contractors, and have found even well reviewed/regarded/reputable contractors to be severely lacking in responsiveness. The company, which I've been loyal to, does all HVAC for residences, and have been in business for many decades. They do several new boilers a day, in addition to forced air systems, so at least in theory, they should know steam. My guess is that they do, but just don't want to spend the time / energy to actually provide sound advice and thorough work. On thing I've always appreciated about my steam guy is that he hasn't tried to force me into a new boiler. I've had him in for service/advice many times in the past few years, and until now, he's counseled me to stay the course until my boiler craps out, and today was that day. So I'm working with what i have, and am at the cusp of replacing the boiler.

So a question about the new steam line... how would this work given the need for the steam / supply to exist above the water line. Is the solution that I just need a radiator mounted high (such as in a built-in wall alcove), with its own drip back to the return? What I'm picturing in my head, in theory, could be very simple, and located very close (basically right in front of or to the side of the boiler).

Last, I do like the comment about seeing how the temp is after insulating. I think I will give that a try, and in parallel, talk w/ my steam guy.

Jamie Hall

Well now -- if you hear water dripping in the boiler, that's not good. That's not supposed to happen! Do you have any idea how much fresh water the boiler is taking to keep its level up?

We are not talking about a new steam line for the basement heat. What we are talking about is a perfectly conventional hot water line feeding conventional baseboard heaters in the basement. The hot water line is tied into the boiler -- there are a number of ways to do this, but commonly there is a tap somewhere below the water line for the feed, and the return often goes into the wet return before the Hartford loop. A circulation pump is provided -- usually quite small. The circulation pump is controlled by the basement thermostat, and there is an aquastat set for some convenient temperature -- 160 seems to be pretty common -- to keep the boiler water warm in the odd case that the house hasn't called for steam, but the basement wants heat. This is not rocket science! And very common.

gfrbrookline

I have a relatively large one pipe steam system that had steam radiators in the ceiling of the basement since they can't go under the waterline. They provided minimal heat to the unit. We did as @Jamie Hall suggested and installed a heat exchanger on the boiler and added a hot water loop in the basement with it's own tstat. It made a huge difference.

nicholas bonham-carter

The definitive test of a suspected leaking boiler is to overfill the boiler up to the header, when it has cooled a bit, and let it stay like that for a few hours. Any leaks will be seen as puddles or stains on the floor, or in the fire box.
Drain it back down to the normal water level afterwards.--NBC

BUSTERBATBOY

Please do not cover up your gas appliance flue