Strange Thing with MCI Frame

Glennman · July 16, 2021, 12:28:26 PM

I'm getting my ceiling/roof in my '02 MCI ready for spray foam insulation, and in doing so I'm drilling holes into the hollow framework so that I can fill it with spray foam from a can. I haven't finished yet, so I don't have a full understanding of it yet, but when I drilled holes into the center piece in the ceiling, it is completely hollow. However, when I drill into the side to side roof frames, they appear to be filled with yellow fiberglass. Very strange. Did MCI install fiberglass on some of the frame work, and not other parts of it?

hogi6123 · July 21, 2021, 11:48:50 AM

The side to side ribs are open on top, they were stuffed with fiberglass before the roof was installed.

The front to back ribs are closed on top, so there was no way to stuff fiberglass into them.

That's what I remember anyway.

oltrunt · July 21, 2021, 06:19:18 PM

I found filling enclosed spaces with canned spray foam (Great Stuff) didn't work because the foam must have humid air contact to kick off. After building the tube frame for my toad I carefully taped over the openings in the original unibody frame and filled the void with GS. It wouldn't cure and made a sticky mess that I had to remove before trying again. The second time I made quite a number of slits in the clear tape covering the holes in the frame and let the foam ooze out to be trimmed later. That worked. Jack

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dtcerrato · July 21, 2021, 07:41:05 PM

Spray misting helps to cure but of we don't have that problem.in Florida! I was used GS today. It won't come of my hands. It'll just have to wear off..

windtrader · July 21, 2021, 08:05:26 PM

Quote from: dtcerrato on July 21, 2021, 07:41:05 PMIt won't come of my hands.

Acetone - 100% quick wipe and gone

luvrbus · July 21, 2021, 08:16:24 PM

Quote from: Glennman on July 16, 2021, 12:28:26 PM
I'm getting my ceiling/roof in my '02 MCI ready for spray foam insulation, and in doing so I'm drilling holes into the hollow framework so that I can fill it with spray foam from a can. I haven't finished yet, so I don't have a full understanding of it yet, but when I drilled holes into the center piece in the ceiling, it is completely hollow. However, when I drill into the side to side roof frames, they appear to be filled with yellow fiberglass. Very strange. Did MCI install fiberglass on some of the frame work, and not other parts of it?

I was told they did that for thermo break my DL was the same and they told me it was ok to spray over the rib but not to fill the inside being slow I couldn't see the difference my self

chessie4905 · July 21, 2021, 09:00:31 PM

They fill roof pillars of cars with foam anymore, so I can't see where you couldn't do the same.

hogi6123 · July 22, 2021, 06:33:57 AM

Quote from: luvrbus on July 21, 2021, 08:16:24 PM
I was told they did that for thermo break my DL was the same and they told me it was ok to spray over the rib but not to fill the inside being slow I couldn't see the difference my self

Thermal break means no pieces of metal are connected to both the interior and the exterior through the insulation. Heat flows well through metal, so for best results you need to insulate over the ribs in addition to in and around them.

Heat also transfers pretty well through an air space, so it should be helpful to fill the ribs, I have no idea why someone would say don't do it.

When insulating, you also must think about moisture. When you breathe out, you don't want the moisture to go through your insulation and condense on the outer shell, mold will grow in there eventually.

luvrbus · July 22, 2021, 07:02:54 AM

Quote from: hogi6123 on July 22, 2021, 06:33:57 AM
Thermal break means no pieces of metal are connected to both the interior and the exterior through the insulation. Heat flows well through metal, so for best results you need to insulate over the ribs in addition to in and around them.

Heat also transfers pretty well through an air space, so it should be helpful to fill the ribs, I have no idea why someone would say don't do it.

When insulating, you also must think about moisture. When you breathe out, you don't want the moisture to go through your insulation and condense on the outer shell, mold will grow in there eventually.

Prevost are the same there has to be a reason, windows use bond breakers and air gaps to stop heat transfer,maybe its for the transition from stainless to steel I just sprayed over mine I wasn't going to drill holes every few inches

dtcerrato · July 22, 2021, 09:34:02 AM

Although our coach is very dated - owned for 42 years & remodeled & updated all through those years the one thing we did way back in the day was after finishing everything in the roof & ceiling area we put a continuous layer of 3/8" dense thermal/acoustical layer of foam carpet padding on all the ceiling & all the way down to the top of 100% of all the windows - front, back, & sides. Then went over it with carpet in the bedroom & living room & decorative Marlite (Hardboard) in the kitchen area. Maybe that's why to this day one 13,500 roof air is all we've comfortably ever needed. Wifey & I can't ever forget the intensive high & prolonged migraine we had from the WELL VENTILATED but not enough application of Weldwood contact cement on both layers of materials all ten gallons worth... Geeze
Young & foolish.

Jim Blackwood · July 22, 2021, 09:57:52 AM

I've seen many applications of foam sealant where rust has been accelerated around the foam. Can't say if some property of the foam caused condensation or if something else was going on there but indications were that rust would not have been a problem without the foam. Be cautious.

Jim

Glennman · July 22, 2021, 12:29:38 PM

Boy, did this thread explode or what! Great advice here. I know that filling the cavities does not take care of all thermal connection to the exterior, but I believe it may help. I've heard a lot about very thin layers of foam or ceramic material that may make the final break, but even the fasteners create a connection. I've seen screws transfer heat through roofs of commercial buildings that have the insulation installed on top of the roof framing. The screws extend from the roof surface, through the insulation, and into the framing, and condensate at the roof at those spots. On the curing of the foam, I left the holes open (like oltrunt said). I'll have to check (the best I can) to see if I can determine if it cured at all.

For a more complete thermal break, I'm thinking of installing a 1/2" iso board between the members and the plywood, but the fasteners are still a problem. I haven't figured out a way around that yet. Maybe a guy could install wood on the sides of the frame, then the fasteners for the ceiling would go into those wood members instead of directly into the frame (?) Where there's a will, there's a way.

ktmossman · July 22, 2021, 03:11:03 PM

I'm filling my frame with foam, but I'm using Ceratex for the thermal break.

chessie4905 · July 22, 2021, 05:07:52 PM

I would use the lower expansion foam.

luvrbus · July 22, 2021, 05:14:33 PM

Can you even buy the high density closed cell spray foam in a can I never saw any foam in a spray can worth the effort myself,I have tried some so called closed cell in a can but it was a long ways from from the hot sprayed closed cell foam in the bus