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Air Vents Through the Roof?!

DaBoss Member Posts: 2
I am in a multi-family building, (27 units, 3 stories) which has a single pipe system. We regularly maintain it and have purchased a decent set of controls to maintain the system operating consistently. I am working on having the supply piping insulated.

The building was gut-rehabbed in 1998, and after walking on the roof the other day, I noticed there are air vents on the roof - located roughly at the top of each steam riser. I find this quite strange and haven't yet read anything that leads me to believe this is regular. In addition, we do have a 'bell' like air vent inside the building. These are located only on the third/top floor and above the radiator at the ceiling AND only in the kitchens (no where else). These 'bells' are located at the top of the riser (above the radiator by 6ft) and just before it extends through the ceiling and onto the roof.

I can only image this is like a belt-belt-belt and suspenders type of set up - with some amazing venting - however there are limited complaints about water hammering. Anyone experienced this type of set up or would suggest these air vents on the roof are unnecessary and could be removed at all locations? It seems like we are losing a lot of heat to the exterior! Thanks for your comments.


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,493
    Can you post pictures of the vents, so we can see what you have?
    Tall buildings (over 4 floors), with one-pipe systems frequently need air vents at the top of the risers. Usually these are vented to the inside. I would be worried about some freezing damage to any outside mounted vents, but if so far they have not suffered, then maybe you can leave them alone. If there are any signs of cracking, then they will leak steam when closed, causing the boiler to take on a lot of makeup water, resulting in an early death. As they are needed, then maybe they could be mounted on the inside. Proper main venting with adequate capacity, and low pressure is the key to even heating, with steam arriving at every radiator simultaneously. Maybe your new controls are in response to some imbalance of venting.
    I would be also worried about the possibility of roof leaks at the penetrations.--NBC
  • GreenGene
    GreenGene Member Posts: 290
    Supply piping has to be insulated, all of it, for the system to work correctly, a building that large especially, you're turning the steam to water before it gets to the radiators, = water in supply = steam meets water = water flashes back to steam = hammer.

    Rehab's in 98 eh?, bet they removed all the pipe insulation and didn't put any back on.
  • DaBoss
    DaBoss Member Posts: 2
    Here are a couple of pictures showing the roof vent and the interior "bell" vent located near the ceiling of the third/top floor. I didn't mention these pictures are from the end of the line, but are typical throughout each of the third floors.

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Um, I think the aluminum vents might be venting the exterior of the steam piping chases to help keep things cool inside the building, but I seriously doubt there are any actual steam venting vents or open pipes in the enclosure. The others labeled Gorton (looks more like an alarm clock than a bell) are definitely air vents for the steam system.

    Have you ever actually seen steam vapor coming out of the aluminum roof jacks?

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
    JUGHNE Member Posts: 8,666
    The aluminum roof vents in your first picture look too modern
    for a 1 pipe steam system. If the dead men provided a place for that inside Gorton 2 or any air vent, would they also have vented the system thru the roof?

    Are these roof vents near the kitchen sinks? They would even steam a little on a really cold day like -10 degrees if they were drain-waste-vents. (wouldn't smell like steam if you got your nose close). If you run water down the kitchen sink and listened with stethoscope or short pipe stuck to your ear that might tell you what's up.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,493
    Are there any main vents like that in the basement?
    From the apparent size of your building, I would say you need more main venting, such as Sailah's new product.--NBC
  • Abracadabra
    Abracadabra Member Posts: 1,948
    Those roof vents are used to vent the attic space on flat roofs.
    JUGHNE Member Posts: 8,666
    They must be larger than one might gather from the picture.
    Now that you mention it I have seen some that are 8-10" in diameter.