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A Shoulder Season Problem

Long timer lurker, very infrequent participant.

I've been in my current house for a bit over three years, now. Little background my house is heated by 1 pipe steam, which generally runs very well, with one exception, the finished attic space in the shoulder season.

This room is generally between 3 and 6 degrees colder than either the first or second floors during mild weather, basically any out door temperature in the 30's or above. Once we get below that it's fine.

An un-related issue with an animal getting into the knee walls has given me the "opportunity" to open them up and repair the ducts work for our AC system and while I'm solving that issue I plan on addressing the heat issue too.

The room is heated by one single pipe radiator which is oddly placed pretty far about 15' away from the actual riser from the basement. I've not yet opened that part of the knee wall but I believe that the pipe just runs along the floor and is pitched the wrong way as it bangs a bunch in the beginning of every cycle.

At minimum I plan on moving and re-piping this radiator and moving it to be closer to the riser since it's location really doesn't make much sense where it is.

I also plan on adding better insulation when I have all the knee walls open. The issue is I'm not sure that these things will actually be enough to fix the general issue.

With that said this will be a pretty sizable project and so I want to just do it once. Here's my worry, I will be improving some of the insulation but the general ceiling is going to stay somewhat poorly insulated and I'm not really sure how much of an improvement insulating the knee walls will really make. Additionally the radiator does get heat it's just noisy so I'm not sure if moving it will actually make the room heat that much more/faster once it's moved I'm mostly just addressing the noise issue.

My thought is to do one of few things I'm considering:

1. Move the radiator, fix the slope on the piping and add better insulation in the knee walls (least effort)
2. Move the radiator, fix the slope and insulation and also add a second radiator (medium effort)
3. Remove the radiator entirely run an hePex hot water loop off the boiler and do radiant walls with a separate tstat (most effort)

I lean toward #3 largely because this room often needs heat long before the thermostat in the lower level calls, and generally looses heat very quickly, having a separate thermostat would solve that issue but also better insulation might minimize some of that problem.

# 2 might help the room recover more quickly in the evenings when the boiler is running more often but during the afternoon and evening when the boiler doesn't need to run it would still get cool.

Opinions appreciated!


  • Fred
    Fred Member Posts: 8,542
    How large is the current radiator? How many EDR? Have you done a Heat loss for that room? It may be that the current radiator is just too small. If it were me, I'd:
    - Make sure the radiator is sized correctly
    - make sure the supply pipe is sized adequately to support the correctly sized radiator
    - shorten the horizontal run, especially if the radiator isn't where you want it
    - Correct the pitch of the horizontal run
    - Insulate as best as possible and factor that into your heat loss
    - Install a vent at the top of the vertical run to that radiator so that air is evacuated as quickly as possible and so that radiator get steam as quickly as possible.
    All of these things should help during the shoulder season and if it gets too warm during the regular heating season, use a variable vent on the radiator to slow it down.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    Without ripping out the first and second floor for running new risers . Cut out and cap the attic radiator and run electric strip heading for a separate zone . Every floor or wing should be zoned for comfort . They all will have different heat losses ..
    I have enough experience to know , that I dont know it all
    EBEBRATT-Ed Member Posts: 15,526

    If any zone , and that's what the attic is if the zones heat loss is very different from the rest of the floors (and the thermostat is on the other floor) you won't get it comfortable....ever.

    More insulation will help, and I would encourage you to do that.

    1. Move rad and fix piping
    2. insulate
    3. If that doesn't fix the issue (and it probably won't) add a pc of electric baseboard as @Big Ed_4 mentioned.

    You say it's fine when the weather is severe so the electric heat will only be a "booster" during mild weather
  • BobC
    BobC Member Posts: 5,478
    Your greatest heat loss is from the ceiling and any air leakage is also a huge factor
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
    STEAM DOCTOR Member Posts: 1,971
    As others have mentioned,  the two obvious troublemakers are the different heat losses and the poor radiator piping. You did mention that when it's very cold, the attic heats properly. This is quite possibly due to long run times. I am wondering if longer heating cycles are the simplest of solutions. What is the cycle per hour or swing setting on your thermostat? I have solved many such problems by simply changing the thermostat cycle per hour setting 
  • dabrakeman
    dabrakeman Member Posts: 552
    I assume you have already tried to regulate it to some extent just with a variable radiator vent. I.e. a Hoffman 1a? Run it wide open when the weather is mild and throttle it down a bit when the weather gets cold. This may require a little more sqft of radiation in the room than you currently have depending upon how fast you are already venting it. Combine this of course with some insulation and the piping fix. I run variable vents on all my radiators because as you say, conditions change and the ideal balance changes along with it. What is on that 3rd floor radiator right now?
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    In Dan Holohan’s Lost Art Of Steam Heating ( you should consider a copy) a simple solution is noted. Big problem is that effectively the main to that radiator is long and you are venting with a radiator vent.  So there’s a delay.
    So do what Fred said. Remove the angle radiator valve, install a tee and mount a Gorton #1 on top and from the side install a full port ball valve rated for steam to the radiator with a union. The gorton handles venting the riser, the radiator vent, well, vents the radiator alone. 

    You know it heats the space fine when the steam actually gets up there. Why over complicate things?
  • johncharles
    johncharles Member Posts: 50
    edited November 2020
    Thanks for all the feedback,

    1. To what STEAM DOCTOR said, my thermostat is set to a 0.5f diff but looking at beestat it looks like the boiler actually shuts off closer to 0.3f, you'll see in this screenshot that the boiler is off but the house is still only at 70.8 you would expect the boiler to have stayed on until 71.0 if it was truly running a 0.5 swing most of the cycles are between 17 and 22 minutes at this outside temp.
    2. A couple other people have commented to add venting to the riser currently the radiator has a MOM D on the riser and a Gorton C on the radiator itself:
    3. About the size of the radiator I have not done a heat loss of the room, I would need some additional knowledge of how to do that but the radiator is a 16 section burnham slimline per the documentation on their website running on steam it should be able to output 48 EDR or 11520Btu's given that the room is comfortable in the colder weather I think the radiator is sized correctly.
    4. About the roof/ceiling when it snows it's the peak/middle of the roof that keeps the snow the longest the areas which melt most quickly are the edges around the perimeter over the knee wall area.

    Is there a decent guide for running a proper heat loss calculation? I've found a few calculators online but they mostly only deal with square walls and flat roofs.
  • johncharles
    johncharles Member Posts: 50
    I just recorded the banging as a cycle just ran, I don't want to do all the stuff to upload it as I'm sure you all know what banging sounds like.
    The riser to this radiator is the last connection on the main, the main is about 40ft and has 2 Gorton 2's on it, and steam makes it all the way around in about 4 minutes. Of note is that from when the banging started to when the radiator get's steam is an additional 4 minutes, so out of a 17 minute cycle this radiator is only getting steam for about 9 minutes where the rest of the house is getting steam for a longer period.

    On setting a larger swing the ecobee does that when you enter away mode automatically and with a 1.5f swing this room is just about as cold even though the boiler runs longer per cycle because the room has much more time to cool down. Despite issues with the radiator the first and second floors just don't loose heat as quickly as this room.
  • johncharles
    johncharles Member Posts: 50
    edited November 2020
    Also of note, none of my second and third floor radiators actually have valves on them, just elbows straight into unions. This was the way it was when I bought the house.
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    Well then. Seeing the vent there, I guess it’s time to overcomplicate things. Or, I should say, someone already did by putting a sizable modern slenderized radiator at the end of a horizontal that’s likely too small for counterflow operation, let alone the fact that there’s no way that line is pitched 1” in 10’ back to the vertical riser. That runout could only work (possibly) if that were a two pipe system. Moving the radiator to shorten or eliminate that runout could address the water hammer.
    Stating what has already become obvious, your heatloss and temp swings remain even if you’re freed of hammer. 3rd floors can be like that if they aren’t meticulously insulated.  As others have presciently said, insulation and an auxiliary heat source (with an actual heat loss calc) may be the best approach, after seeing the photo. I’d be inclined to keep the radiator but in a more functional location so the aux heat doesn’t have to run when unoccupied. But that’s a judgment call.