Adding insulation into the roof

[RyanOBrian1]

So I have my roof off the camper right now and getting a new one put on due to hail damage.

My question is, now that I have the roof off maybe I should add a little more insulation? Right now it has the styrofoam insulation but it appears as though there is still about a 1 in gap that I can add some more insulation. I was thinking of adding Reflectix on top of the styrofoam. Do you think that would benefit me at all? Or would I essentially just be getting rid of the existing air gap between the sheet metal and the insulation? I wouldn't want to introduce a thermal bridge using the Reflectix.

 

[Wallowa]

Great view of the roof construction...construction photos are hard to come by...assuming that adding any insulation in the 1" space you describe will help then I would tend to go with another 'hard' foam piece..reflective material I would assume does best in reflecting solar radiation.

Question: Make certain that filling that 1" space does not promote condensation problems...remember also that trapped air is a good insulation [think down jackets]...

What does FWC advise?

Thanks again for photo.

Phil

 

[ckent323]

Seems to me that replacing styrofoam with high density foam is worth considering.

Extruded polystyrene foam (XPS) also known as blue board or pink board comes in many different thicknesses and edge profiles. XPS has an R value of 4.5 to 5.0 per inch of thickness.

It’s reasonably priced, light weight and easy to use. This product is also used to insulate the outside of foundation walls and even under slabs.

Cost = This product is the middle of the road for these types of foam board insulation products.


Polyisocyanurate also known as polyiso is seen in all kinds of commercial building applications and more recently with residential building projects. Polyiso is typically used with a foil facing and it has an R value of 7.0 to 8.0 per inch of thickness. The reflective foil facing makes it an excellent insulation board when radiant heat is involved. The foil facing also makes it very easy to seal with good quality foil faced tapes.

Cost = Polyiso is the most expensive of the foam board insulation products however it’s the highest R value.

Polyurethane and polyisocyanurate are both closed-cell foams. They contain low-conductivity gases in the cells (usually one of the HCFC or CFC gases.) The higher R-Values (R 7.0 to 8.0) are the result of thermal resistance of the gases in the cells. This can lead to a couple of disadvantages including: off gassing of HCFC or CFC gases, and reduced R Value over time as the gas escapes.

I'm not sure if having a foil face is a problem or not. This is where I would do a bit more research. It seems to me there likely will be condensation on the inner surfaces in cold and or humid environments no matter what is used so the foil may be a do not care. If the foil is a does not matter then I would go with the highest r-value foam.

I think there are spray on foams that are very good and they do not have a foil backing. Maybe that is the way to go.


https://www.homeconstructionimprovement.com/foam-board-insulation-values/

See also:

https://www.rvingplanet.com/blog/ultimate-guide-to-rv-insulation/


I recommend that you focus on minimizing conductive heat transfer instead of radiative or convective heat transfer. Conduction is far and away the main heating/cooling process mechanism in our campers.



BTW: Condensation occurs when water in gaseous form changes back into its liquid form. When warm air rises, or comes in contact with a cold surface it usually cools and loses its ability to 'hold' water.

The condensation collects on the cooler surfaces - often the ceiling and upper part of the inner walls of the camper because there is a lot of warm air with water vapor in it from your breathing and skin and/or cooking. As a consequence of the minimal insulation the side walls and ceiling of the camper they become cold enough (and rough enough) for the water to form droplets on the surface as it goes from gas back to liquid - i.e. condensation.

 

[Ace!]

I tend to think of insulation as the ability to warm and hold air.

 

[ckent323]

Thermal physics - heat always flows from hot to cold. Insulation does no warming, it slows the transfer (or flow) of heat.

More insulation results in slower heat flow, that is all it does.

As a simple example:

In the case where the outside is continuously hotter or colder than the inside (think winter in the snow or summer in the desert) then all the insulation can do is slow down the heat flow. Some other mechanism (heater/air conditioner) is needed to keep the temperature inside from slowly increasing or slowly decreasing over time.

If we assume the outside temperature is rising and falling over a 24 hour period then ideally one would want sufficient insulation that the heat flow through the surface would be minimized.

So say it is cooler outside than in the camper. ideally by the time the temperature drops to a point you want to turn on a heater from the heat escaping, the outside temperature has risen to the point that heat is starting to flow back into the cooler interior of the camper. Similarly if it is hotter outside the camper until it becomes cooler outside. The more extreme the temp differences the more (thicker) insulation is needed. At some point you have to add a heating or cooling source (air conditioner or heater) to keep it comfortable inside.

Of course we are severely limited to how much insulation we can add so ideally we use the highest r-rated insulation we can get in the thickest layer we can get (which is probably no more than 1" to 2" thick). The pop-up material sides are a complication as are the single pane windows. But they need insulation too.

I am talking conduction here because that is the primary heat transfer mechanism. Radiative and convective heat exchange is negligible in comparison in our camper application.


I hope that helps a little.

 

[DavidGraves]

Hello Ryan

Thanks for the image ...a great resource for us all...please take and post more as you re roof.

Is there really a 1 " gap or air space above the insulation ?

How thick is the insulation itself ?

What year model is your camper?

Thanks again

David Graves

 

[smlobx]

Building extremely energy efficient home is what my company does so let me give you my $.02...

If you have a 1" gap I would agree that adding insulation there would be of great benefit. The easiest would be adding 1" of foam board (commonly called Blue board around here). this would give you an additional R-5. Having a professional insulation company spray closed cell (2#) would be the best as it will be able to fill all the nooks and crannies but it expands when applied and will have to be shaved to allow the roof to be applied which is beyond the capabilities of the general public.

Regarding thermal bridging inFWC campers and the associated problems it causes this was the main reason I bought another brand.
I talked with the FWC guys at Expo East a couple of years ago about how easy it would be to minimize this but they didn't seem interested...

But if you would like to do it (and I would highly reccomend it) you could put a layer of DuPont Thermawrap over the insulation and metal studs to minimize it then install your roof on top of that.

Here's a short video that explains the benefits...

https://youtu.be/Z1BCBTQ80o4

If you were to do both you would have one of the best roofs on the market and the additional weight would be less that 5#.

 

[ckent323]

smlobx,

The therma wrap appears to be a fiberglass type insulation material with a tyvek backer. I like that approach providing a water permeable membrane on the insulation. For our campers I wonder how much it matters.

For example. I just returned from a 45 day trip to/from Alaska. We experienced overnight temperatures as low as 20 degrees but typically in the upper 30's to low 40's during our trip.

We kept the camper warm at night using the heater set to about 50 degrees or so but even at that we experienced ice formation along the top and bottom edges of the side material and along the wood strips which are attached to the aluminum support in the ceiling.

On the coldest nights the heater cycled on and off frequently. Clearly there is thermal bridging but clearly the amount of insulation is minimal and insufficient to slow the heat transfer very much.

We also experienced a lot of condensation inside which we wiped off with a towel every morning.

The major surface condensing water was the side walls of the pop up portion. To be sure there was condensation on the metal parts on the ceiling and along the wood strips under the Aluminum rafters in the ceiling (clear sign of thermal bridging) but the pop up material was the worst place.

Where I am heading with this is that even if the ceiling had really good insulation and a good vapor barrier, there would still be significant heat loss and condensation in the camper. So I cannot help but wounder how much effort and cost one would want to go to on just the ceiling.

More insulation is better and maybe the Therma wrap is as good as anything but I am thinking that the for this application the performance of the various insulation materials may not be much different and perhaps the main driver should be cost (probably why FWC used styrofoam to begin with). If therma wrap is similar in cost to say XPS then I think it is a sensible alternative to XPS.

I have a good understanding of thermal heat transfer but I am no expert on insulating RVs or campers.

Craig

 

[ntsqd]

Something that I'm not seeing addressed is the insulation's combustion by-products in a fire. The RV industry has some standards for this that ought be be known and the why of it understood before going in a contrary direction. Not saying don't veer from them, just to understand the why behind them to make better decisions about what to use and where.

 

[RyanOBrian1]

smlobx,

The therma wrap appears to be a fiberglass type insulation material with a tyvek backer. I like that approach providing a water permeable membrane on the insulation. For our campers I wonder how much it matters.

For example. I just returned from a 45 day trip to/from Alaska. We experienced overnight temperatures as low as 20 degrees but typically in the upper 30's to low 40's during our trip.

We kept the camper warm at night using the heater set to about 50 degrees or so but even at that we experienced ice formation along the top and bottom edges of the side material and along the wood strips which are attached to the aluminum support in the ceiling.

On the coldest nights the heater cycled on and off frequently. Clearly there is thermal bridging but clearly the amount of insulation is minimal and insufficient to slow the heat transfer very much.

We also experienced a lot of condensation inside which we wiped off with a towel every morning.

The major surface condensing water was the side walls of the pop up portion. To be sure there was condensation on the metal parts on the ceiling and along the wood strips under the Aluminum rafters in the ceiling (clear sign of thermal bridging) but the pop up material was the worst place.

Where I am heading with this is that even if the ceiling had really good insulation and a good vapor barrier, there would still be significant heat loss and condensation in the camper. So I cannot help but wounder how much effort and cost one would want to go to on just the ceiling.

More insulation is better and maybe the Therma wrap is as good as anything but I am thinking that the for this application the performance of the various insulation materials may not be much different and perhaps the main driver should be cost (probably why FWC used styrofoam to begin with). If therma wrap is similar in cost to say XPS then I think it is a sensible alternative to XPS.

I have a good understanding of thermal heat transfer but I am no expert on insulating RVs or campers.

Craig

Thanks for all your information Craig... super helpful and a lot more knowledge then me on the subjet. I've gone back and forth now in my mind, if I should put polyiso RMAX in place and then seal with ducting tape... and take out all the styrafoam. Or it may not be worth the effort. I use my camper the most in the winter sleeping in ski parking lots, so my camper sees below 30 regularly... so it may be worth it. I did already buy the foam cutting hot pen...

 

[smlobx]

Craig - Congratulations on your recent AK trip. I look forward to your TR!

As you mentioned you experienced significant condensation when the temps dropped and you had your heater on. As you probably know the two main byproducts of complete combustion of propane is Carbon Dioxide and water. You can also get carbon monoxide if the combustion is not complete.

Given that all pop up campers aren't really well insulated we face a significant battle in trying to manage the interior temps when the outside temperatures dip below freezing. As the warm air coming from the heater (with its associated moisture) comes in contact with the ambient air which is, in your case about 50 degrees, the relative humidity of the room exceeds 100% and results in condensation. This is also exacerbated by the moisture we expel as part of our normal respiration.

With campers that are metal framed and are attached directly to the metal exterior the transfer of heat from the interior to the exterior is significant. You can see in the video I linked previously .

Several years ago the use of metal framing in residential construction was all the rage here. A couple of years ago we were asked to meet with a homeowner who had just recently purchased a 12,000 SF house and was having problems keeping the second floor cool enough in the summer. Upon inspection there were dark stripes on the ceiling every 16 inches. It turned out that the heat being transferred from the dark shingles through the metal roof joists was burning the drywall paper! Long story short we ripped off the shingles and installed SIPS panels creating a thermal break and adding an additional R-10 to the roof and then installed a new roof. This solved his problems.

In our new construction even adding just a 1/2" foamboard (R-3) to the exterior sheathing will result in a 20% improvement in the walls thermal efficiency. So if the OP has the ability to add additional insulation and create a thermal break the improvements should be worth the effort.

 

[smlobx]

Thanks for all your information Craig... super helpful and a lot more knowledge then me on the subjet. I've gone back and forth now in my mind, if I should put polyiso RMAX in place and then seal with ducting tape... and take out all the styrafoam. Or it may not be worth the effort. I use my camper the most in the winter sleeping in ski parking lots, so my camper sees below 30 regularly... so it may be worth it. I did already buy the foam cutting hot pen...

Ryan you have a unique opportunity to see how your roof is constructed. I wished all manufacturers posted pictures of their build process...but I digress!

Is the existing styrofoam an open cell foam board (large beads) or is it more like the Dow board? The reason I ask is that I've never seen closed cell foam board that was white but that may be a regional thing.
Also I would think that there may be some form of attachment of the foam board to the rest of the roof but I'm just guessing. You might want to be careful if you decide to remove it...

 

[RyanOBrian1]

Ryan you have a unique opportunity to see how your roof is constructed. I wished all manufacturers posted pictures of their build process...but I digress!

Is the existing styrofoam an open cell foam board (large beads) or is it more like the Dow board? The reason I ask is that I've never seen closed cell foam board that was white but that may be a regional thing.
Also I would think that there may be some form of attachment of the foam board to the rest of the roof but I'm just guessing. You might want to be careful if you decide to remove it...

I believe it's open cell foam but I can give you more info later today as well as more photos if you'd like them. If I replaced this with polyiso would anyone recommend sealing it with ducting tape? I was thinking of filling in with foam but think it wouldn't work well with all the movement the roof does.

 

[knoxswift]

I believe it's open cell foam but I can give you more info later today as well as more photos if you'd like them. If I replaced this with polyiso would anyone recommend sealing it with ducting tape? I was thinking of filling in with foam but think it wouldn't work well with all the movement the roof does.

I would love to see more pictures of the roof construction.

 

[smlobx]

I believe it's open cell foam but I can give you more info later today as well as more photos if you'd like them. If I replaced this with polyiso would anyone recommend sealing it with ducting tape? I was thinking of filling in with foam but think it wouldn't work well with all the movement the roof does.

Yes I think several people would be interested in more pictures.
Taping would be a good idea as well but I'm not sure what type of tape would be best with polyiso....

 

[ntsqd]

Does the skin of the roof fit tight to the frame?

IF it does one way to break the thermal bridge, increase the strength of the assembly, and make the guy/gal who tries to remove the roof skin after you shout words his/her kids shouldn't hear would be to use some of the foam bodied VHB tape on the top of all of the frame members.

 

[RyanOBrian1]

So what I ended up doing is pulling out all of the existing open cell **** foam, tracing it onto the RMAX 1'' Polyiso and using a foam cutter to cut the piece and replace. I'm about half way done. There will still be a air gap between the foam and the sheet metal roof.

Ntsqd, already ahead of you.

https://imgur.com/a/ZavuP23

 

[ntsqd]

 

[smlobx]

Is the insulation you used 1 1/2" thick?

 

[Timothy McGowen]

For example. I just returned from a 45 day trip to/from Alaska. We experienced overnight temperatures as low as 20 degrees but typically in the upper 30's to low 40's during our trip.

We kept the camper warm at night using the heater set to about 50 degrees or so but even at that we experienced ice formation along the top and bottom edges of the side material and along the wood strips which are attached to the aluminum support in the ceiling.

Did you use the Thermal Pack?