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Old 01-20-2014, 09:58 PM   #1
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Insulating the floor

When I opened up the belly, I discovered a remarkable absence of insulation. Up by the propane tank I add 2 pieces of r-13 insulation. Behind that I added 1 piece of r-13 on each side. This will not interfere with the mechanism for the slides. In the middle I added 2 pieces of r-30. That is 4 pieces sided by side. Each piece was 15 inches wide. The RV only gets down to 62 with the outside temp of 30 now. The floor is no longer cold. I was extremely satisfied. I also opened up the front belly but discovered the black and grey tanks are very well supported and i was only able to add 1 piece of insulation under a grey tank.
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Old 01-20-2014, 10:10 PM   #2
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imo, over time the batting insulation will get a lot of moisture on it and retain water, sag, the paper will disintegrate and you may have a mold problem. could you have tried to install some type of solid board type insulation?
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Old 01-20-2014, 10:16 PM   #3
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The furnace blows hot air into the belly through several holes in the duct. I can always open it up and remove the insulation. I hope with the flow of air through there it will carry off the moisture. I have read several forums and there was no good remedy that did not have negative consequences. 3/4 inch foam board with foil backing only has r-5 value. It would be difficult to get sheets into the middle area due to the ladder cross member. If I experience negative results, I will post them here.
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Old 01-20-2014, 10:23 PM   #4
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The furnace blows hot air into the belly through several holes in the duct. I can always open it up and remove the insulation. I hope with the flow of air through there it will carry off the moisture. I have read several forums and there was no good remedy that did not have negative consequences. 3/4 inch foam board with foil backing only has r-5 value. It would be difficult to get sheets into the middle area due to the ladder cross member. If I experience negative results, I will post them here.
I was told that I have a 'heated underbelly' and when I when I pulled down the under board a little just saw the furnace duct tubes going the length of the TT. By your statement above, have you seen the 'holes in the ducts'? I assumed that it was just residual heat and not have actual holes in them.
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Old 01-21-2014, 08:15 AM   #5
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Yes there are actual holes in the duct to heat the underbelly. This is under the island and goes straight through the duct there is a smaller hole further back ad well. Look in your floor grill on the front side of the island. You may see some foil tape. It is holding your water lines in place. There has to also be a hole further forward to get the lines inside the duct. That makes 3 holes.
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Old 02-06-2014, 01:16 PM   #6
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I can confirm Ron's comments. There was NO insulation inside the under belly. Now I have my drain valves freezing closed. Argh! Told my dealer this is unacceptable and we are trying to formulate a plan for resolution. I like Ron's idea of installing the batting like you would a roof. Have a continuous piece the entire 38 foot length and the width of my 2008 Cedar Creek and had ZERO freezing issues.

More to follow...

John (S/N 409)
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Old 02-06-2014, 02:19 PM   #7
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Quote:
Originally Posted by Priusron View Post
The furnace blows hot air into the belly through several holes in the duct. I can always open it up and remove the insulation. I hope with the flow of air through there it will carry off the moisture. I have read several forums and there was no good remedy that did not have negative consequences. 3/4 inch foam board with foil backing only has r-5 value. It would be difficult to get sheets into the middle area due to the ladder cross member. If I experience negative results, I will post them here.
I have never heard of wholes in your duct for heat in the underbelly, what TT do you have. Most units come with a 2" duct in the underbelly off the furnace. heated tanks and heated elbows take care of the other problem. There is some silver insulation on top of the underbelly which is about 1/4" thick with an
R value of 3.75. But can go up to R24. It is sold at HD and lowes in rolls mostly used to wrap water heaters but it is the same comes in widths up to 48".
It is sealed foiled front and back. Even if you have to double it you would never have a problem as Les brought up. Not cheap by any means. I will say this, if the factory cut wholes in my duct runs they would be replacing them.
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Old 02-06-2014, 05:59 PM   #8
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Priusron, please advise of any problems. I am curios why you did not fill up the space with insulation? Are the large gaps are counterproductive? Also I can not tell if the picture is right side up or upside down; Shouldn't the vapor barrier be on top towards the interior floor?
I'm totally ignorant on this issue, yet it seems so logical to do, and why isn't done at the factory with spray in insulating foam? This is pretty much the standard now for quality homes. Seems like that would be cheaper, easier and whole lot more efficient with no moisture and mold issue down the road. However, as I write I am thinking it may be a weight issue?
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Old 02-06-2014, 06:49 PM   #9
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Dave 01, the vapor barrier should be seen from looking in. The fiber glass should be against the floor. That is the correct way to install paper backed insulation. That insulation might not have vapor barrier on it. I can not tell from the picture either of how it was installed. The expandable insulation that is sprayed is really lighter and it even has a better R-value. that is why these units are called 3 season and not 4 seasons.
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Old 02-06-2014, 07:51 PM   #10
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I have a 3950 rl. There are holes in the duct to heat the belly. No vapor barrier in the insulation. If you spray foam any repair to wiring or plumbing is extremely difficult.
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