I just opened up a ceiling chase containing some 3/4" copper hot water pipes carrying water for a radiant baseboard system in order to add insulation around the pipes.  (they were wonderfully radiating into my unheated attached garage before)

I've finished doing the wrap of pipe insulation, as best as possible without completing detaching the pipes from where they've been attached to the studs.  I plan on filling the chase (about 2-3" space below the pipes) with fiberglass batting before closing the drywall back up.  I have, however, found some additional gaps in my building envelope where the pipes pierce into conditioned space.

My questions for the forum:  What is the advisability of using Great Stuff or similar large-expansion spray foam around the pipes?  Is it safe for me to more liberally spray big plugs into the odd areas within the chase to supplement or even replace the batts in some areas?  I can see black dust on the existing batt work which is usually indicative of a draft, so I'm somewhat inclined to just go nuts with the foam.

My inclination is that it ought to be ok to do this, but what do I know -- I'm just a homeowner.  The Dow Great Stuff Big Gap Filler data sheet () is not very helpful -- it only prescribes a max temperature (120F) apparently for storage, due to fear of container rupture, but there is nothing there I could see (or maybe I overlooked it?)  regarding application temperature.

Thanks for your help.

Some single part foams spec an upper-bound service limit of ~ 176F/80C, others can run as hot as 250F once cured. Installation temps are normally below 120F- don't apply it to a hot pipe. Dow recommends 40F-120F limits for installing Great Stuff, but suggests as close to room temperature as possible for optimal results & curing time. (see: http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/4583/~/what-are-the-application-temperature-limitations-when-using-great-stuff%3F ), but the service temp upper bound is probably at least 175F.

If you have a lot of gaps and sealing to do it's worth buying a 2-part foam sealant kit (eg Dow FrothPak), or at least springing for a single-part foam gun that takes the 25oz cans. eg: http://www.energyfederation.org/premierenergy/default.php/cPath/21_4843_65 (note the 176F service temp spec ) The guns are well-designed to valve at the tip- you don't waste a whole can on just a small job the way you can with the throwaways, the gun simply WORKS better than the throwaways, and it's a lot more STUFF than the throwaways.

Thanks, Dana!