Steam riser inside exterior wall next to cold brick wall- how bad is that?

bipbap

We pushed back and rerouted a steam riser to run inside an exterior wall (due to it being right in the middle of a countertop) so now it is inside the wall between the 12" thick exterior brick wall and the drywall.

However there was almost no space left between the brick and the steam riser so it is difficult to insulate the pipe going up. I was hoping to have at least space to slip some 1/2" rigid foam between the brick and riser. There is rigid insulation on the left and right side of the pipe in the wall but just not all along the back where the pipe almost touches the brick wall.

This situation just occurs on the first floor because inside the first floor ceiling the riser jogs back so it is back inside the room on the 2nd floor and not sealed in the wall.

How bad is that in the scheme of one riser to be directly next to a cold exterior brick wall?
It will be a huge cost and headache to move the pipe out more and there really isn't any space.

What issues could arise from it running uninsulated next to a cold brick wall or will it probably be just fine?

Single pipe steam heat system with that riser serving 2 radiators above if that helps.
Thanks for the advice!

KC_Jones

First,I wouldn't put foam insulation anywhere near the steam pipe. Anything that gets close to the pipe or touches it should be fiberglass not foam.

Second the only issue you will have it the pipe losing heat to the brick and everything else. You may have to adjust the venting on those radiators to get the heat up there as that pipe is going to condense like crazy being in that wall. Once the brick warms up it will be less, but the brick will cool down quickly too.

I think this will fall into the hard to predict category.

ChicagoCooperator

It's pretty common in Chicago to have the pipes next to a brick exterior wall - you often see the notch that was built into the brick for them. That said, I don't know if they were insulated (I would guess not in builder grade apartment buildings), but it's not uncommon.

ethicalpaul

I can't stand it myself, but it seems pretty common. My wood frame house has 4 of them like that, and I'm going to for sure re-run the one that's in my bedroom to be within the living space. I can't stand heating up the neighborhood.

Fred

What size is that pipe? What size (EDR) are the two radiators it feeds? Is that wall a wall exposed to the wind? It may be ok but it may not. If the pipe is larger than needed to support those two radiators, you may be able to down size the vertical pipe one size by putting a reducer at the top and one at the bottom and get enough room to put some fiberglass insulation behind it. I say that but, in no way do I mean to do it before understanding that a smaller pipe can support both radiators.
The other option may be to move the riser to an interior wall and then carry it back, in the ceiling, to the connection for those radiators. You will have to maintain a good pitch but if you can run across the ceiling, between two joists and keep the pitch in the basement run-out, it is do-able.

EBEBRATT-Ed

I wouldn't give it a second thought. It's a riser it will drain all the condensate it needs to. If you have an issue it will be in the basement if the run out from the main can't handle the condensate. Besides once the riser gets hot it won't form much condensate. The heat loss inside the wall is what it is.

Maybe you can blow fiberglass in there

Gsmith

Can you wedge some plywood between pipe and brick, might be better than nothing.

bipbap

I didn't realize the rigid foam is not good to put next to the pipe.
Is it a mater of leaving a space so it doesn't actually touch or shouldn't be close at all?

If i just leave it uninsulated could that cause banging pipes or anything?

ethicalpaul

Looking at this chart, you can be ok with lots of foam. Just stay away from polystyrene

https://www.engineeringtoolbox.com/insulation-temperatures-d_922.html

This super-tuff stuff seems OK up to 300F to me: https://www.homedepot.com/p/1-in-x-4-ft-x-8-ft-R-6-5-Foam-Insulation-268417/100576728

This stuff is polystyrene and I'd avoid it (although in practice it's probably fine): https://www.homedepot.com/p/Owens-Corning-FOAMULAR-150-1-in-x-4-ft-x-8-ft-R-5-Scored-Square-Edge-Rigid-Foam-Board-Insulation-Sheathing-20WE/207179253

Maybe I'll do a test of each one on my NBP because now I'm curious

khkiley

I had a similar situation with an inaccessible, uninsulated riser in a cavity. Would have had to take a wall down to get in there to insulate it.

I filled the cavity with Perlite (like the kind from the garden store) from the top of the cavity. It is loose fill and found its way around the whole pipe. There was some leakage of the perlite, which I used some flashing tape or stuffed the gaps with Roxul Mineral wool insulation.

https://www.perlite.org/insulation/

bipbap

Ah geez, it’s the polystyrene foamular one.
Is it bad enough next to a hot pipe to consider ripping it out?

ethicalpaul

I mean, the foam isn't going to burst into flame or anything, it's only 212 degrees, like barely above its rating probably, and there is certainly extra built into that. And that's only where it is in direct contact with the pipe. Any distance at all and that temperature will be lower.

I'm not a lawyer, but I would just keep an eye on it. The foam might degrade or deform a little but I don't think it will even do that. Is the pipe in direct contact with it?

ChrisJ

I would be more worried about how the new piping is done.

It needs to be piped so condensate drains well. Level runs with 90 degree turns usually won't cut it.

apraetor

I had my rim joists sealed with 3" of isocyanate spray foam this autumn. A couple of my first floor radiators are close enough to the wall that their risers got entrenched in the foam right where they penetrate the floor. This was several weeks prior to when we turned heat on for the season, so the foam had plenty of time to complete curing and out-gassing.

I've gone down and poked at the foam even after the system has been fully heated for a prolonged period, and that foam is stuck as hard as ever to the piping. It wasn't deliberate -- I ensured all the lines were covered in 2" fiberglass, aside from a few elbows I hadn't got to yet -- but it's certainly tolerating the heat just fine. It even insulates better! There's maybe 0.25-0.5" of foam on the piping, and it never gets warm to the touch. The fiberglass pipe wrap doesn't get hot per se, but you can definitely feel a slight warmth when the pipes are up to temp.

ethicalpaul

Yeah that two-component iso-poly stuff is awesome. Closed-cell probably and can surely take the heat

Intplm.

12" is a lot of room . You say it's in brick? Is it possible to over size the hole. Make it oval rather than round above and below. Then pull or pry the pipe forward toward the room. Insulate around the created space?

gerry gill

exterior wall- depends how cold the pipe gets, and how much time elapsed between boiler firing. You may get hammering if it rains inside the frigid pipe when steam comes barreling in. Or it may be just fine. You will soon find out.