What should I use to insulate the floor?

[mbatm01]

So, with these methods we are talking about here, what is the best way to insulate the floor?

With the shell off it seems easy to add insulation over the frame and deck on top, but using the shell on technique, do I insulate afterwards? It would seem that I would tear up any insulation sliding the new floor into place.

Kevin

[malconium]

I am also thinking about what approach to take for this. I found a previous thread titled "Under floor insulation" that had several suggested approaches. I personally am leaning in favor of using aluminum foil type insulation instead of fiberglass or foam. The foil is light weight, waterproof, vermin proof and performs well.

Here is a pointer to a major manufacturer who sells their products through ACE Hardware, Lowes and Home Depot:

http://www.reflectixinc.com

I have not made up my mind on how best to install the stuff. If I do use my proposed floor install technique (with the rim and splice around the edges) there would not be much need to slide the floor panels around much. In that case I might buy the 48" wide roll and install it similar to the way the fiberglass was intalled letting the foil dip down a couple of inches into each cavity. I would use the foil tape the vendor sells to tape the joint down the middle of the two strips. This would help leave an air gap between the floor and the foil that should help the foil do a better job. It would also create a trough for any water to collect into (if any would actually be in that area). My thought is to punch a small hole in the middlle of each dip to let any moisture run out into the belly pan.

By the way - Vintage Vacations does extreme restoration projects on older trailers and they used two layer of Rlectix brand foil insulation for the trailer featured on the following site. It was to be used as a full-time office in Colorado so the owner was ultra concernded about having good insulation. You can see that their note mentions the two layers and the brand name of the foil insulation.

http://www.vintage-vacations.com/195..._navigator.htm

Does anyone reading this thread think we should launch another thread to talk about this topic so we can pull in more comments?

Malcolm

[thenewkid64]

Split off the floor replacement thread

[malconium]

I called the Reflectix customer service person today to ask some application questions about their products. The person I spoke to was very helpful. One thing she said was that it was a good idea not to attach the foil directly to metal framing if possible since that could create some sweating. I discussed underfloor installations with her and she suggested attaching some sort of wood furring strips and then stapling the foil to that. I did run the idea I posted in my earlier note by her (about putting the foil over the floor cross memebers and letting it sag in between. She thought this would be OK but maybe not quiet as good as using some approach that kept all of the foil a couple of inches away from the bottom of the floor.

One thing I am wondering about with the foil is how to properly insulate around holding tanks and plumbing. There are foils from Rlectix that can be used directly on things like ducting, etc. The issue is that the reflective foil works best if there is an air gap on each side.

Has anyone in the forums used foil insulation? How did you apply it?

Thanks,

Malcolm

[silver suz]

We used Denny foil in our house that has solid wood flooring. Denny foil is aluminum foil backed by kraft paper. we taped the roll sections together with the tape you mentioned. The wood was solid and stapled together at an angle with a nail gun. It's worked for almost 11 years, (the rest of the house is tile.) It is also used in all the walls and ceilings. (which is why a cell phone doesnt work in here.) We are going to do the same thing in the trailer. A 3/8ths inch gap caused by the furring strips is an excellent heat/cold barrier, as long as there are no leaks. For under neath you should use the foil double backed that has tiny perforations to let the material "breathe".
This has given me the energy to open the two boxes sitting in the hall. We decided this time to use a heavier product that is about the thickness of a telephone cover book. Heavier aluminum on both sides with the kraft paper in between not perforated. This is used to create barriers with the foil tape between the person inside and any insulation smells etc walls, floors ceiling etc. The width is 48-52?" and as long a roll as you want. We got it from I think healthy-homes.com the seattle based one healthy.homes.com? Some combination of that sliver suz

[silver suz]

Wrong..wrong..wrong... try www.AFS-foil.com for the foil barrier stuff. suz

[malconium]

It is interesting to note that there are a lot of different kinds of foil products. The one I was thinking of using from Reflectix has a layer of plastic bubble pack type material between the two layers of aluminum. This provides a bit of insulation to reduce any conduction of heat between the two layers of foil. I don't know how much different the performance of this type is compared to having a layer of craft paper between the foil layers. The kraft paper is presumably more for overall tear resistance. Also Reflectix told me today that sealing around the edges of the foil was a good idea to create a dead air space that would actually help with insulation values. As I mentioned in my note I was thinking of adding a small hole in the middle (in the center of the foil sag in other words) that would allow any condensed moisture to run out into the belly pan. Actually it seems to me that having a good airtight seal might help protect the underside of the floor from moisture that might be splashing around in the belly pan area.

With foil it seems like there still is the issue of how best to insulate around the holding tanks which seem to go down pretty much to the bottom of the floor frame.

Malcolm

[silver suz]

Malcom, it seems I was misleading. We plan to use both. The kraft foil will go for instance on both sides of the wall between the kitchen and bed area. The reflextic roll (which is resting against another wall now)will also be our insulation. We are also debating on using the all cotton batting or the new woven fiberglass paper wrapped batting. Either foil product would seal that from the room inside. Yes, we are super insulating, but find in the long end it pays off with lower energy usage. Our family debate is whether and what to use next and with whom. One thing the reflextic comes with tabs that makes it easier to install on aluminum struts (or ribs, or whatever you call them.). It is a matter of packing a lot of insulation in a small space. We have also considered the expanding foam. We are going to be very careful to insulate and seal the refrig passage (we have 12 volt/120w) and any thing that gives off heat, such as the portable heater/ airconditioner, the dehumidifier, the washer/dryer, the small dishwasher (uses less water than hand washing and is more sanitary) all heat producers are ducted out in a sealed fashion, All pipes will be insulated, along with the hot water heater. We have an old jennair down draft cooking vent that will be installed along side the 2 burner top, and insulated and vented out. I am putting a layer of refletix in the curtains, between the decor material and liner material. I have an interesting concept for the skylight which is yellowed and too dificult to open. I will use thin glass blobs glued to plexiglass which will be fitted into the opening permantly. That way the light will come thru and create patterns of dark ,light blue and clear bubbles, allowing natural light in and having an air void to trap heat. I also have a similar idea for the vista vues. All the windows have been taken out and rubber seal replaced, re-vulkenized etc.
If I could figure it out, I would line all the awnings inside with the reinforced aluminum foil.!!!
There will be a 4" air lock fan to pull shower moisture out, and I could go on forever. suz
I also worry about the issue of letting the belly pan "breathe" or making it water tight.

[Over59]

Is the reflect foil serving any purpose at all behind an aluminum belly which is itself reflective. I would think that dollar of dollar an air pocket product would give more real world R value, like fiber glass or foam board. There's a huge difference between bench test lab results and real world insulted benefit. Glue shiny heavy duty aluminum foil to the underside of your floor and you'll save some money.

[Janets Husband]

I don't know how you feel about it but I would look at Sprayed In Polyurathane Foam.
Lots of advantages to other insulation. No air infiltration, water proof, light weight, high R factor per inch, ease of instalation. You can keep it from sticking to replacable items by coating them with patroleum jelly.
The only disadvantage I can find is Cost.

[Over59]

Like the jelly idea. I'll use that one. My Caravel has foam floor (PO). Problem is any water which gets in from the top gets stuck between the foam and floor. Leaks become a must avoid at all cost because one small one could take out alot of floor fast. Thats what happened in the front of my caravel. So if you foam leave an aire space under the floor for water to run away from the plywood. All said and done I think I'll go with fiberglass of some kind at least around the edges.

[silver suz]

Paul, I use the denny foil because it is cleaned of oils, which is good for people with chemical sensitivities. I know, we always have to pay more to get products that are "safe". Thanks, suz

[silver suz]

Any comments on how to let the belly pan "breathe" while wanting super insulation? I know from experience that a structure totally enclosed and sealed with foil builds up a huge humidity problem in hot humid weather. silver suz

[markdoane]

You're on the horns of a dilema. If you want it to breathe, you lose insulation effectiveness due to convective heat flow. If you seal it up, there is no place for excess moisture to escape. I'm also a little concerned that the foil backed insulation will be ineffective because there is little infrared radiation to worry about (it's all reflected by the outer skin and bellypan, like Paul stated), and the moisture barrier properties will trap any moisture inside and lead to mold or rot.

Everyone knows a neighbor or relative who has a supersealed and superinsulated house that has mold problems.

[silver suz]

The key is to keep a dehumidifyer constantly running. which means a hole for the water to run out and a way of dealing with the heat from the dryed air. know that problem- still havent figured it all out. But plan to have a dehumidifier on board. I often find the airconditioner needs to run longer and really make it colder than I want- just to get rid of the humidity- especially when it's 99% outside! Perhaps in a smaller space the dehumidifyer will work- best for no mold is to keep it at about 30% .Suz

[Chuck]

how about "tyvek" stapled to the underside of the plywood floor?

I can tell you that steel frame members don't "breath" very well when there's soaking, ringing wet fiberglass nestled up against it.

Friend of mine used the 2" foam boards, attached with long screws and fender washers. didn't ask how he dealt with the plumbing, though. another thing he did was removed the plate that covers the rear frame x-member and forms the front "wall" of the bumper storage compartment, in an effort to increase airflow.

[silver suz]

Tyvek isnt viable for me, i'm sure it's fine with others. My husband wants to use the woven fiberglass with paper wrap, but I don't He also wants to use the insulation made of cotton (used jeans micro shredded) and borax. Seems to me that would be a sponge and mold grower too. So far we haven't agreed on anything. Foam cell boards are too chancy for me too- after all a small airstream is just a big oven- outgassing like crazy! We still havent' come to a solution but we still have the floor ,plumbing, electrical etc to do! time to "discuss" suz

[Over59]

Ms. Suz
Prehaps you would find a more direct solution working from the other side. Unless you are planning on extended stays in sub 32 areas you may not need much insulation under the floor. Put it on top of the floor. Subfloor, insulating lay of an acceptible foam board, finish floor. I know there is a sensitive foam out there, I think it's soy based. So you give up an inch, big deal. The keeping cool challenge is tha damn thing couldn't be designed more like a solar oven if they tried, except painting it black. It's the walls not the floor that are the keeping cool problem. No?
Just a thought.

[mbatm01]

Isn't there a one way flap valve used in boats, almost like a valved scupper? Could be used to vent the belly pan...

Kevin

[malconium]

There is a an excellent explaination of the benefits of different types of foil installations at the following web-site:

http://www.tvmi.com/rfoil/physics.htm

Some thoughts or conclusions that I have after gleaning from the above site and others are the following:

1.) Even though an airstream has a relective skin it is not nearly as relective as highly shiny foil insulation. In the case of my belly pan I doubt it is all that effective as a relector (and never will be). If it is true that the aluminum skins are really that reflective and that such a large percentage of heat loss is reflective then we wouldn't be talkaing about the need to insulate at all.

2.) A very well polished airstream skin will in fact have less heat gain in the summer.

3.) Where the foil should be placed for best effectiveness depends on whether we are trying to keep heat out or keep heat in the trailer. I think this means that the outer surface of a well polished unit will help keep heat out but does not really help keep heat in. Maybe we should polish the inside of the skin as well?

4.) Foil seems to work best when its relective surfaces are not in direct contact with anything but air.

5.) There are 3 types of heat transfer mechanisms that all need to be considered to some degree (conduction, convection, radiation). Evidently 65% to 85% of heat transfer through walls is by radiation and up to 93% through floors.

6.) Reducing heat loss is not just a case of having a high R-value since R-value seems to only apply to heat transfer by conduction.

Some practical application thoughts:

If it is true that 93% of the heat loss through the floor happens through radiation then it seems like underfloor insulation could be accomlished quite well without actually sealing up the floor to air flow. What appears to be needed are at least two reflective surfaces - one pointing toward the interior and one toward the ground - somewhere in the underfloor cavitity. It seems to be preferable to have an air gap above and an air gap below the foil. Since the underfloor area seems to be quite capable of getting really dirty I think I would want to keep the foil near the top and try to block dust from getting onto the top surface of the foil (reducing its reflectivity). So I think the question still is how best to mount foil an inch or so below the floor. Maybe using sticky back foam tape might work? I think I would still want to have the area above the foil mostly sealed but still leave a weep hole or two for condensaction to drip out. It might make sense to staple a layer of foil directly to the bottom of the floor and add another layer about 1" below the floor. The layer on the bottom of the floor would help prevent moisture from attacking the floor and would give an extra barrier to summer heat gain.

From the examples given in the tutorial I sited above I think it would be great to have two layers of foil in the wall cavities. It is interesting to note that their example wall was only 1-1/2" thick. Again would sticky back foam tape be a good machanism for suspending the foil in the middle of the cavities?

I like the idea of some sort of proactive ventilation mechanism for under the floor. My son-in-law suggested installing a small fan under the floor that could be used to power vent the area. I am also aware that you can buy round louvered vent covers with a built in screen that are designed to be used in the soffit of your house (on the bottom side of your roof overhang if you are not familiar with the term soffit). The ones I am thinking of are made out of aluminum and are about 3" in diameter as I recall. The louvers are all nicely pointing in one direction. I think I will at least consider using some of these vents and maybe the fan too.

Malcolm