Finishing attic and adding radiators

Bill_37

We have a 1904 house with two full stories plus an unfinished attic (hip roof, so LOTS of room up there). We are wondering if it would be feasible to cut into the supply/return lines on one or two of our second floor radiators and run lines up into the attic to heat a large finished off room. Our current system is simply gravity-fed, no circulators, and an old boiler. Would we have to run fresh supply pipes up straight from the basement?

Thanks,
Bill

Dale

Consider what you have

Take the time to read Dan's discussion on the left, heating Q&A and the still current thread that references an article on the topic by Dan. I don't think cutting into the rads you have will work, you could get the new ones upstairs really hot and have no heat in the second floor ones. What could work is if you can tap into the riser mains and returns and use an orifice or manual valve on the new top rad loop. If it were me I would put what I wanted in the new attic room give it it's own stat (controlling only a pump) and feed it supply and return from the basement with pex. I would use a small circulator for this little zone. Since your new wonderfully insulated room heat loss should be low the tubing size and flow should be small. Doing this you may have a pressure problem and need to add an expansion tank to get the pressure needed for the new higher rads.

Dale

\"unique\" post

I should have looked sooner. the post I'm refering to on gravity hot water is the "Unique" post active today. Grumpy's response there gives the link to Dan's article.

Mike T., Swampeast MO

Some ideas.

Is the attic currently insulated? Are you adding additional insulation during the attic remodel?

When you start heating the attic, a MAJOR component of loss in the space below disappears. It's quite possible that the rooms below will overheat (or overheat even more if insulation has already caused this problem).

As mentioned, it's often more difficult to keep the heat of a gravity system OUT of the 3rd floor than to get it there...

3rd floor radiators in gravity systems were sometimes fed via the branch of a tee in a supply riser. If you have a rad in a space that already tends to overheat (at least 1" supply/return pipes AND under the newly heated space) you might be able to do this--if you can go STRAIGHT up after the tee you could probably use a pipe as small as ½". In this case you could probably have the 3rd floor rad quite large--about the size of the one below.

Another possiblity might be to remove some radiator from the 2nd floor and extend its lines to the attic. Perhaps you have a big upstairs hall with its own radiator in addition to a radiator in the hall below (open through the staircase)? If so, you can VERY likely remove that 2nd floor hall radiator, extend the pipes to the attic and feed a radiator nearly 2-3 times the size of the one you removed.

Two-pipe gravity systems don't seem to be as unforgiving as one-pipe systems, but if you want to retain the gravity circulation you MUST pipe in the ways of the dead men!

Try to find a contractor really familiar with gravity systems--if this is a DIY, study, study, study. I'd honestly try to keep your new piping as accessible as possible until you're certain that everything is working reasonably!