apartment building steam - venting and insulating

ari

We have been upgrading the vents on our steam overheads to big mouths (candelabra style, as needed) and insulating those lines, and now are moving on to address the radiators and risers of our 6 story apartment building.
Some lines -generally kitchens- have risers which provide heat- no radiators. Should we install large (big mouth, etc) air vent(s) on the top floor?
Some risers which supply radiators are exposed. Should they be insulated?
Thanks.

Fred

I'd use the Barnes and Jones Varivent on the top of those kitchen pipes. That will allow you to adjust the rate air is pushed out of them since kitchens tend to have ovens/burners and cooking going on and may get too warm with a Bigmouth.
The other pipes that are exposed and feed radiators can be insulated if that additional EDR from those pipes isn't required to warm the space.

Jamie Hall

Six stories? I would very seriously consider putting Big Mouths on the top of each riser, assuming that you can do it without major hassles. It will help getting even heat on all the floors -- which is likely to make your tenants happier (if they notice...). I also would insulate risers which supply radiators, if you can do it in a way which is not obtrusive and pretty firm. Spaces which have risers running up through them and no other heat... When you come right down to it, the risers themselves don't supply much heat, either (a 2" riser with an 8 foot ceiling supplies a whopping 1,000 BTUh). Psychologically, though, they may be important to the tenants' comfort. I'd say it's a toss-up.

JohnNY

Chances are the heat given off by those risers were calculated into the warming of the rooms where they reside and the sizing of the radiators took that heat gain into account. Following that logic, you should leave them bare and let them give off heat. That's the long answer.
The short answer is that most systems like the one you describe were oversized in BTU output. You can insulate them if those rooms feel amply heated. I'm a big fan of directing all the energy delivered by the system to the heat emitters, so I'd insulate them.
And there's no downside to venting the tops of risers except for the cost it takes to vent them. It's most often worth doing.
I say go for it.

scott22nyc

Ari, I had this same question for some time now. The theory behind massive main venting (aiming for 1-3 min) makes sense. For a riser which supplies radiators the same should apply, which is, insulate and use main vents on the top floor so that each floor can receive the steam at near the same time to equalize the temps throughout. I would be interested to see what the professionals say for both your steam riser scenarios.

nicholas bonham-carter

I would use the bigmouth vents anywhere you need a main vent, as the quality is much better, and their big ports are less likely to plug up. This assumes you are running the system at a few ounces, verified by a 0-15 ounce gauge, and a vapor stat.
When the building is in perfect balance, you can reduce the target temperature in the apartment, most exposed to the wind to a constant 65 degrees.
You may need to put smaller radiator vents on in some locations, like Hoffman 40's.--NBC

scott22nyc

The 6th floor riser air vent hole is pretty small. How do you install such a large air vent like a big mouth?

Fred

Is that vent actually in a hole that was tapped into the side of the pipe or is it in a cap, on top of the pipe? You may be able to drill and re-tap the hole but I wouldn't try to tap a 3/4" hole in a 2" pipe. In reality, a 1/8" hole will vent about as fast as a Barnes and Jones Vari-vent. You can put a 1/8" nipple in the hole and use a coupling that opens up to 1/2" or 3/4" and then an elbow to install the vari-vent or the Bigmouth in.