Best Three Season Bottom Floor Insulation

[TECMike]

Been trying to wrap my mind about how to go about insulating the bottom of our three season trailer. Our little Sunnybrook Harmony has exposed tanks and I am in the process of installing tank heaters. However I would like to add a little insulation to the bottom, which has a black composite material covering the bottom of the floor.

I have asked this question before, but am having a problem understanding how to choose a product that will not cause a problem with moisture to the existing floor structure.

Also I have eliminated spray foam as a choice as I can see it being a problem if I ever need to gain access to the underside flooring.

So is there a product that both breathes and provides insulation at the same time that might fit my application? Thanks in advance. Mike

[westend]

spike99 wrote:


I still don't understand why some folks don't like Spray Foam (CC - contractor grade) under their RV/TT. I applied under my RV/TT and its amazing stuff. And, it isn't too much work to install.

After seeing benefits of before and after with my own eyes, IM RV/TTs should use Foam (spray or vacuum bonded) as minimum factory build.

.

I think some are worried about moisture being held against the bottom of the subfloor and what would happen in the future if needing access to the underbelly. I believe these are both false issues. As you've outlined in your posts, a bit of prep is what's needed for future access or repair and the moisture issue is just not there. If anything, the foam should keep the floor decking drier than without. My rig has a continuous aluminum sheet under the flooring system and, when I pulled up the original plywood floor decking, the underside was like new. So much for moisture entrapment, not an issue.

Agreed, also, some type of foam should be factory standard. I've done this job on a couple of older trailers and the results are dramatic. Heating a trailer is tough enough with the heat loss from windows, doors, and the minimal wall cavities. Having a cold floor is the worst for keeping comfortable.

[wrenchbender]

Foam it, well worth the effort

[kckettridge]

On our previous TT, we had a leak under the bathroom sink which caused water to leak down under the TT, soaking the fiberglass insulation that the manufacturer used to insulate the underbelly. There was so much water that leaked under there that it also caused the black underbelly material to buldge. I had to make a slit in it to drain the water. After the water was drained, I hoped that the insulation would dry but after a week in 100 degree weather and two commercial fans blowing on it, it was still wet. I removed the black underbelly material and gutted all of the fiberglass out and installed OC Foamular Ridgid Foam Insulation It was alot of work cutting out the pieces (used my table saw to cut the Foamular) to exact size to fit between the floor joists but well worth it. Once I had the entire floor fitted and installed with the Foamular, I used CorPlast
and these fasteners to secure the CorPlast to the floor joists. Due to the lightweight of both the Foamular and CorPlast, I believe it actually lightened up our TT a bit.

[spike99]

For tank heating pads, surf: http://www.modmyrv.com/2008/07/17/rv-holding-tank-heating-pads

If using heating pads, suggest using 110-120V AC version - since 12V version sucks lots of 12V power from onboard batteries.

I still don't understand why some folks don't like Spray Foam (CC - contractor grade) under their RV/TT. I applied under my RV/TT and its amazing stuff. And, it isn't too much work to install. For comparison, surf: http://www.youtube.com/watch?v=IBu19XyBLLA

After seeing benefits of before and after with my own eyes, IM RV/TTs should use Foam (spray or vacuum bonded) as minimum factory build.

.

[TECMike]

Sorry to hear of your friend's problems. Wife and I always carry a generator in the back of our truck and plan to stop at rest areas to run it and keep the black water tank heating pad warm enough to keep things a least mushy when traveling.

We will probably put tank heating pads on the gray and white water tanks as funds and time permit in the future.

[Ron_Nielson]

One thing to keep in mind is that when you do that great job of insulating your underbelly area, if it gets cold enough that your tanks freeze, it will take a long time for them to thaw out. If you have some additional heat to prevent them from freezing, and thaw them if frozen, and that's the best way to do the job.

I had a friend who did an absolutely great job insulating the underbelly of his TT with spray foam, and then covered the underbelly with alum sheeting. Friend and GF were going to ski in AZ for a few days, then move on to Colorado for another week. They skied a few days in AZ and they didn't have time to dump their tanks before driving to Colorado. No problem, he thought, I'll just dump when I get to Colorado. Then drove 2 days thru extremely cold weather to arrive at the Colorado ski resort. When they got there, they discovered that their gray and black tanks were FROZEN SOLID, could NOT dump, and it took a LONG TIME to thaw out. OOPS!!! Great insulation job.

[TECMike]

Thank all of you for your comments. Believe me, I deeply appreciate them so very much. Perhaps I can move forward as time permits.

Installing a tank heating pad on the black water tank, along with covering it with reflextix, has been very successful. Wife and I will probably put tank heating pads on the gray water and fresh water tanks as time and funds permit.

And eventually we will get around to insulating the floor. Also, I am making window insulation panels using reflexix, which I am sure will extremely helpful.

Again, thanks so much for the information and help. Mike

[LarryJM]

westend wrote:
Could you guys that have improved the under-belly sections of your TT's comment on the results and maybe some changes you would/should have made?

Thanks for posting the different projects. It's a credit to you guys that have taken the time to take pictures to share.

I'm completely satisfied and think but don't have any factual numbers, but think it keeps the underbelly area and hence the floor warmer. Another HUGE benefit was making sure the water lines were as close to the floor as possible so they are in the warmest area of the underbelly. Only regret was I didn't take time to stuff the penetrations with metal wool since we have Chimpmunks in our yard and they tend to like to get under one cabinet area where the penetrations are for all the electrical from the converter and the water and drain lines are from the kitchen. We keep styrofoam containers in that area and they like to nest and chew those up in that cabinet area. They don't make a huge mess and in fact I actually put a roll of TP in there for them to use so they don't go looking for something I don't want them to chew on:B They are actually fairly neat when you look at what they have done when they get into that area of the trailer. That area is sealed from the rest of the trailer interior so they are somewhat confined which is good.

Larry

[westend]

Could you guys that have improved the under-belly sections of your TT's comment on the results and maybe some changes you would/should have made?

Thanks for posting the different projects. It's a credit to you guys that have taken the time to take pictures to share.

[LarryJM]

TECMike wrote:
Been trying to wrap my mind about how to go about insulating the bottom of our three season trailer. Our little Sunnybrook Harmony has exposed tanks and I am in the process of installing tank heaters. However I would like to add a little insulation to the bottom, which has a black composite material covering the bottom of the floor.

I have asked this question before, but am having a problem understanding how to choose a product that will not cause a problem with moisture to the existing floor structure.

Also I have eliminated spray foam as a choice as I can see it being a problem if I ever need to gain access to the underside flooring.

So is there a product that both breathes and provides insulation at the same time that might fit my application? Thanks in advance. Mike

Why not just enclose the underbelly area. Mine came with a single sheet of coroplast screwed into the edges of the frame rails. What I did because I was painting my frame is that I sectionalized the entire underbelly into 4' sections that can be individually removed for access to the underbelly area and while I was at it I added some of the board type insulation (R-5 rating) to about 65% of the area between the frame rails. The design I developed and used requires no holes to be drilled into the frame and could easily be added to a trailer w/o an existing enclosed underbelly for a reasonable cost ... in the neighborhood of $300 or so as a WAG with the biggest cost being the aluminum angle iron for the supports and the 1/4-20 nylon bolts, washers and nuts and of course I already had the coroplast material. THIS ALBUM shows the details with detailed descriptions in the captions to the various photos. That album has some additional info on my frame issues, gas line re routing, etc., but all the underbelly work is in there.

This mod would also allow you to add some sort of heating to that area if needed or desired.

NOTE: while I was able to use some of the existing holes to better secure the edges of my underbelly sections you could simple add sections of al. angle iron along the edges in place of where I put the sections of the acrylic "U" channel I made from some leftover wallpaper corner protector I had laying around.

Larry

[myredracer]

One thing many don't know about fiberglass batt insulation is that if you compress it, it substantially reduces the R rating. It's very soft an easy to compress. I realize it's very commonly used by the manufacturers though. It's going to get compressed under the tanks for sure.

If I were to do it, my first choice would be Roxul mineral wool insulation. It's denser and doesn't compress anywhere near as easily as fiberglass. It's relatively easy to cut and work with and if it ever got wet, it wouldn't turn to mush.

Closed cell rigid insulation would also be a good choice. You can buy it in various thicknesses. The problem I would see though is working around all the obstructions, tanks, pipes, etc. Do-able, but awfully time consuming.

The insulating would depend on what you are trying to achieve. If you just want to make the floor warmer to walk on, you could get away with an inch or two of rigid foam glued to the underside of the subfloor. If you want to prevent plumbing and tanks from freezing, I'd look at Roxul. If you have a heated underbelly, you don't want to block movement of air.

[spike99]

.

For my RV/TT's underbelly, I didn't over analyze the situation.

For my 2006 Jayco TT, I simply:
- Removed the underside coroplast (hard plastic) layer.
- Removed its soft fabric layer.
- Removed its water holding fiberglass batt insulation.
- Replaced its underside fabric heat duct pipes with real metal flex pipes.
- Installed its wiring within plastic wire loop and created smooth round corners - before securing wire loom to underside floor.
- Removed its thin 12 gauge linear brake wiring.
- Installed new thick 10 gauge STAR design brake wiring.
- Taped shinny plastic on areas that don't need over spray.
- Using wood, created access door under tub's gooseneck pipe.
- Using landscaping plastic fabric (from home hardware store), used staple gun and duct tape to apply between tank's gap. Thus, stopping spray foam getting between floor and tank gap.
- Called Spray Foam company and they sent over their mobile truck.
- The guy crawled under my TT, applied spray foam CC @ 2.5" - 3" thick
- I did after inspection - for their completion Sign-Off.
- I then removed over spray plastic areas myself.

Since I did before and after prep work myself, the spray foam company gave me a huge discount. And with their mobile truck, I didn't have to tow my RV/TT to their shop location either.

For water protection, I can then re-install the previously removed soft fabric sheet. And for even more water protection, I could re-install previously remove coroplast plastic sheets as well. Same water layer protection as factory build.

If (and if) a wire needs to be replaced or a tank needs to be replaced, I simply crawl under the RV/TT, find each end of the plastic loom piping and fish new wires. Or, cut around the plastic barrier around each tank, then remove the tank. Or, access the tub's gooseneck piping via trap door.

If you feel risk of replacing underbelly wiring is too high, simply install PVC electrical piping and where needed, use smooth 45 - 90 degree elbows and secure to underside floor. Then, fish wiring into these new 1/2" or 3/4" support pipes. Then, spray foam over the PVC piping. If wires need to be replaced, simply fish new wires down the much smoother PVC pipes (instead of corrugated wire loom plastic wire covers).

For my 2006 RV/TT, I never regretted spray foaming its underbelly. re: - click here - Today, they now make Spray Foam that is fire rated. And, its Closed Cell formula is much better (compared to formula I used 4 years ago). And when my RV's inner roof cavity and/or its inner walls need repair, I'll be using Spray Foam in these locations as well.

For me, replacing factory fiberglass batt with Spray Foam Closed Cell was very low risk / very easy solution. No brainer in my books.

Hope this helps..

[opnspaces]

I'm assuming your trailer has a black woven cover on the underbody with the tanks hanging under that. When the RV manufacturers insulate from this point they usually use fiberglass insulation (think pink spun fiberglass insulation from home depot)They hold this up with a large sheet of coroplast. This is like cardboard made out of plastic. They put the insulation up then they put the coroplast up, and run a bunch of self tapping screws through the coroplast and into the bottom of the frame rails. Add a bit of self expanding spray foam where the drain pipes exit the coroplast and you're done.

coroplast

[AlbertaNewbie]

roxul mineral wool, mold amd water proof, just need to keep it in place. can get it in dual density panels for easiest install.