Using intumesent firestop sealants to air seal electrical outlets in fire rated walls.
We are trying to determine if there are any issues with using standard firestop sealants such as STI LCI-305 or Hilti CP606 to air seal the exterior of electrical outlets. Looks like the stuff will shrink but is it enough to compromise the air seal ? Can anyone suggest an alternative product or method for air sealing outlets in a min. 1-hr rated partition wall ? The Hilti 601 product is elastomeric but costs a fortune, there must be an alternative. Thanks !
Asked by Greg Xikes | Feb 16
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Have you considered intumescent putty, such as STI's SSP? They even make a putty pad specifically for electrical boxes. Applied by hand, stays flexible. Rated for up to 3 hour fire walls.
http://www.stifirestop.com/product_information/product_selector/ssp_putt...
We looked at the putty pads but felt they would not create a good seal at the front of the box and to the back of the drywall.
I don't know if it will satisfy your fire code, but for air sealing outlets I've always used Lessco polypans (as part of the air-tight drywall system). Then sealant is required only where the cables penetrate the pan, which can be filled with fire-resistant mineral-fiber or cellulose insulation.
http://www.lessco-airtight.com/
Nutek makes airtight switch boxes with a built in drywall gaskets...2 hour fire rating.
On my own house I used the regular intumescent fire caulk and, after inspection, covered it with regular duct mastic to hold it in place long term, cheap except for the time and attention to detail required.
For my clients I just use the intumescent fire caulk and airtight drywall detailing.
I used the Airfoil boxes in my exterior walls. http://www.airfoilinc.com/index.html They have been really easy to work with and seal. I've been using spray foam but I would think a fire rated sealant would also work in these if the boxes meet your code.
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