do 2 pipe steam systems have venting on roof?

cdazulay

is it possible that they need to vent on the outside of the building/roof?

nicholas bonham-carter

Are you referring to the flue vent, or the system
vent?
The exhaust vent should go outside, and the system vent will be in the basement on the dry return or main.--NBC

Fred

There is a two pipe vapor system that vented into the chimney to allow the draft to pull a vacuum. Someone here, like @Steamhead and @Jamie Hall will probably be able to comment but I'm sure they will want more details about the system and some pictures.

Jamie Hall

@Fred 's right -- there were actually several types of vapour (low pressure) steam systems which vented into the chimney -- or sometimes elsewhere! -- back in the day. They also almost always, if not always, had a a condenser (sort of a very large radiator) in the vent before it went into the chimney -- or sometimes some other sort of nifty gadget to prevent steam and condensate from escaping.

Times have changed, and the preferred approach now is to have one (or more) large main vents on the dry returns just before they drop to go into the boiler.

As @Fred says, though, a few more details about the system and some pictures would help!

EBEBRATT-Ed

If the system has a condensate pump I have seen those tanks vented outside. Not likely in residential work