The situation is that a friend’s first floor ceiling was sheetrocked without insulation being installed to separate the floors for RFH zones. The second floor has alum plates and 1/2″ PEX. The drywall on the ceiling in question is only 1/2″, 16″ o.c., put up with screws.
The best solution i can imagine so far to get insulation between the floors without some nasty drywall work in this occupied house is to blow cellulose in the bays using a hose and backing it out quickly…not dense pack. I don’t know if the 1/2″ drywall can handle the load bec i have always used 5/8″ rock or blown over plaster. I haven’t found any information on blowing cellulose between floors for this purpose nor span tables for drywall’s ability to hold up cellulose insulation.
Are there such tables? Does anyone care to hazard a guesstimate if my idea will work?
Replies
well, 1st... the zones are separated.. just not very well..
they are within the conditioned space, so it's not like one side is 70 deg. and the other is 0 deg.
but... if that's what they want..
yes , you can blow cellulose between the floors.. and i wouldn't worry too much about wether or ot you get a dens-pak
the pressure should NOT blow your drywall off the ceiling, but .. it might.. one caveat.. we furr our ceilings, so maybe our gypsum may be fastened better than yours
the problem is access, you need about a 2' slot to maneuver the pipe and hose
do you have a closet you can experiment in to develop your technique ?
Edited 5/14/2006 6:38 am ET by MikeSmith
The first floor has been like a sauna when the second floor is chilly bec the first floor has RFH in the slab, too. My pal needs a way to force the heat through the 1-1/2" of wood on top of the plates instead of it leaking out of only 1/2" drywall. I turned off the first floor tubes at the manifold for now, but that's not a long-term fix.
Usually, Pex manufacturers recommend at least R8 for under a radiant system in between floors. 2.5 inches cellulose settled will give you that.
I saw R-11 between conditioned space is recommended so that's what i'm shooting for and we've got 9" clear of space, but i don't know about blocking yet until we try snaking a hose through the bay.
I wonder if there is any bridging (blocking) between the floor joists. It would complicate things, even if it were just 'X' bridging.
You usually can "snake" a smaller hose through the bridging. Blocking means another series of ceiling openings.
I've got dense pack in my ceiling that's supported by 1/2 in. drywall.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
I think you pretty well answered my question, Andy. Do you remember the spacing on your rafters? I'm just trying to make sure it wasn't 12" o.c. or something unusual.
Edited 5/14/2006 1:00 pm ET by splintergroupie
Quite normal - 16 in.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
I guess we're good to go! Thanks.