Insulation Methods – Roof/Floor/Walls/Other
I’ll be selecting a rig that has been tested for how long it will hold heat in a chamber during the test. We will be getting a rig that has double-pane windows, has reasonably insulated slides and is setup to reduce noise coming from the mechanical systems (air conditioning) and from outside the rig. We want a four seasons rig but don’t necessarily require the “best” insulation as we will avoid harsh climates. I know that we will be forced to except whatever insulation standards are available from whatever fifth wheel manufacturer we select to buy from. That manufacturer will not necessarily have the best all around insulation methods. Please read on if you want the details —
Here is what I’ve learned or believe to be true about RV insulation methods
First to study what an R value is and how it applies to an rv camper:
The best short definition I could find is “
Even the best materials can be installed incorrectly or used improperly. For example, if a piece of foam insulation has an R value of, say 11, and you cut part off to run a pipe through it, then the actual R value in that area of the insulation is less. If you have a metal wall stud that touches directly against the outside fiberglass of the rig, then the heat will transfer more easily because there is no insulation between them. These installation methods would obviously lower the rigs ability to hold heat. The home we live in today (2-22-15) has a solid piece of 5/8″ foam board running around the exterior that separates the wood stud from the siding. Of course even the nails used to penetrate the foam board allows heat transfer, and noise transfer for that matter.
I know in stick built homes, heat is lost first through the roof, then windows/doors and then walls. Of course with an RV we have the floor to think of. I’m going to view the entire package as if the rig is a tube and how long it will hold heat inside that tube. I know the more windows there are, for example, will have an effect. But I like windows and they can be opened to allow air flow, which again is something that is obviously necessary. I’ve been involved in building homes that were so air tight they had to pump-in filtered air through the heating and cooling systems. Although I know just opening the rigs door will allow a certain amount of the air in the rig to “change out.” Some of the “sick building syndrome” issues people had in their office buildings years ago had a lot to do with off-gassing of materials and poor building circulation. DARN IT, that just added another topic – green building.
Insulation and construction methods should also have an effect on noise levels. Noise is the transfer of energy and something has to absorb or deflect it to stop it. Double-pane windows and some form of full body wrap (over the studs) facing the outside of the rig should help. The ability to spread-out the stud spacing should also help, which is a benefit of solid foam insulation panels compared to rolled fiberglass. But I’m not sure how structurally sound that would be because they don’t do it in stick built home construction which is not moving down the road at 70 miles per hour and is only rated for 90 mile per hour winds (in Missouri at least). Okay, there is the last point. All of these insulation systems, especially the solid foam board, become part of the RVs structure. In other words, if you left the solid foam board out of a wall then the wall will not stand up to wind or whatever.
Also, in terms of noise, I’ve been reading and asking questions regarding different methods used for heating and cooling systems which have a huge effect on noise reduction. I’ll post about that is the mechanical section of this blog topic.
So here is some basic information I found about
Insulation Methods for RV construction
- Good video on R Values by Pete’s RV
- Post in RV Dreams about having seals replaced in double-pane windows.
Rolled fiberglass/wool mat like most houses have. In most homes they use fiberglass with a paper vapor barrier that is stapled to a wood stud to keep it from sliding down. In commercial building construction a paperless fiberglass is used and holds in place with friction (stuffed between the wall studs). DRV Mobile Suites is a respectable rv brand, they use wool mat that is held in place with glue. I see no reason why this type of insulation would settle over time if installed with glue even with the rig driving down the highway. Of course you have to trust the installer to have used glue in all the areas. Some companies are using mat insulation in their roof areas forming a blanket over everything below which is a good thing because of all the voids that would be hard to work around otherwise, such as ventilation runs. I can see why DRV uses 3″ studs in their walls. First, as the fiberglass/wool mat insulation is of lessor R value when compared to the same thickness of high density foam, you would have to use thicker pieces. Also, high density foam is an actual part of the walls structure. The fiberglass/wool mat insulation has no structural value. In my opinion, best stick with thicker walls if going the fiberglass/wool mat route.
Seems like a fairly common practice is to use some type of radiant barrier insulation to deflect heat/cold and add R value. I could see this helping especially if using foam board insulation that has cut-outs in it from running plumbing. This is something used under the floor and roof.
I’m leaning towards foam board. I’m sure they will have to use something more pliable on the caps like fiberglass/wool mat. Seen it used in residential in more than one application and it’s a good product. There are various types. Here is what NuWa has to say about it:
|Is the Blue Dow foam insulation NuWa uses really as good as they say?|
|Yes, probably better. The rest of the industry typically uses white bead foam insulation board. The same thickness of Blue Dow foam has more than 25% greater strength and insulation than the white bead foam. It would take a 2″ thick piece of white bead foam to match Dow’s superior characteristics with a 1 Â½” thickness. Few people are aware that white bead foam will “absorb” moisture, while the Blue Dow will not. The white bead foam actually gains weight with time. Why don’t more manufacturers use Blue Dow? The answer is simple; it cost more, and customers can’t visually see the feature. At NuWa, you can trust us to give you what you need, even if it cost a little more.|
It’s worth mentioning here that NuWa also uses an expensive high tech foil wrap insulation (originally developed for NASA) which covers the roof, floor, front and back caps, glide rooms, and underbelly / frame. This amazing material is a reflective barrier that rejects heat/cold outward and retains heat/cold inward.
As a side note, as of 2015 Peterson is building the NuWa Hitchhiker and the Excel. Reportedly, both are top fulltime rigs
On a cost-per-R-value basis, rigid foam is more expensive than rolled fiberglass, and it’s definitely more difficult to install around obstacles or in odd-shaped spaces. Here are the three main types of rigid foam insulation:
- Best – Polyisocyanurate (polyiso for short) foam has the highest R-value per inch (R-6.5 to R-6.8) of any rigid insulation. This type of rigid foam usually comes with a reflective foil facing on both sides, so it can also serve as a radiant barrier in some applications. Polyiso board is more expensive than other types of rigid foam.
- Better – Extruded polystyrene (XPS) rigid foam is usually blue or pink in color, with a smooth plastic surface. XPS panels typically aren’t faced with other material. The R-value is about 5 per in. This type of rigid foam won’t absorb water like polyiso and is stronger and more durable than expanded polystyrene, so it’s probably the most versatile type of rigid foam. XPS falls between polyiso and expanded polystyrene in price.
- Good – Expanded polystyrene (EPS) is the least-expensive type of rigid foam and has the lowest R-value (around R-3.8 per in.). It’s also more easily damaged than the other types of rigid foam.
- I’ve noticed some use a thin foam board material as a vapor barrier that is attached to the inside surface of wall studs, claiming this cuts out condensation. That sounds reasonable when used with dual-pane windows. But I would still wonder about moisture created inside the RV from running hot water and breathing. That’s why there are ventilation fans. In stick built homes when people don’t run the vent fan in a bathroom they are allowing mold to grow. Mold requires constant moisture so you don’t want condensation or anywhere moisture might be trapped.
- I wonder if high density foam walls are more sound reducing that fiberglass/wool mat? I’ve done some crude testing of sound “proofing” materials in the past and know separation by space is maybe the best method. More dense wall construction could also allow sound to travel vs a wall with some type of deadening product such as rubber.
- Whatever rig we get I want to make sure they paid attention to insulation in the slides as well.
- I’m interesting is what some companies are doing about air space in the “attic” area. Montana and NuWa I know both advertise their air space. I’m doing more research on this.
- Duraseal is supposed to be a great system for window seals. Read seals last about 10 years unless replaced with these seals.
- Suppose we will see rolled wool on end caps, some floors and ceilings. Might be useful because of cut outs that are running through the foam. If foam is used I’d like to see an extra layer covering everything – with no cut outs in the final layer.
- I’d like to see some type of radiant barrier insulation used to deflect the heat.
- I’m also leaning towards having electric heat pads for storage tanks so they can run while traveling down the road.
- Another big thing being pushed in 2015 and before is no usage of formaldehyde. I did not research the reasons which seem obvious. I’d not want to buy a rig that smells like a chemical factory. I’d worry about the carpet, chair fabric and similar. I’ll be reading forums for specific rigs we are interested in to make sure no one has been having problems.
- It’s not just DRV that is using glued fiberglass bat insulation, so does Cedar Creek and the top rated Newman Motor Home as of 2015.