Insulation R Values

[d30gaijin]

I did a search here but came up with more threads that weren't specific and sadly I don't have the time to read through the hundreds of build threads.

My question relates to the various foam board insulation R values. The blue Dow would be my preferred since it has the highest R rating (6.5/inch), the pink Corning next at 5/inch, and the white R-Tech Insulfoam that appears to come in at about 4.5/inch. The blue Dow, which I would prefer for its higher R rating is not available to me locally. Lowe's on-line lists it but shows it as "Not available" at any store local to me. The Pink Corning is available at my Home Depot as is the white Insulfoam R-Tech, the latter being cheaper by about $4 per 4'x8' sheet. I am not that cost concerned but is it worth the extra $ for an added value of approximately .5 on the R scale?

Needless to say I would much prefer the blue Dow but it doesn't seem to be available locally (I did email Lowe's to ask what's up with it not being available locally when it is shown on their web site but hold out little hope of getting anything other than an "Sorry" reply).

I live in southwest Idaho, which can go from -20f to +110f over the course of the year so I am interested in the best insulation I can get in the space I have (1"). Is a value of 4.5 to 6.5 significant, I suspect it is but I don't know just how significant?

Thank you for any help you can provide.

Don

[caseydog]

One thing to remember, as you choose insulation, is that you are insulating a very small space with a teardrop camper. It isn't like insulating a house. You don't need a whole lot of insulation to stay warm in a 5 by 8 sleeping compartment. Two people inside that size space generate a lot of heat.

If you plan to camp in -20 degree temperatures, then you will need some insulation, but perhaps not as much as you think. I have camped in temperatures cold enough to snow with no insulation at all, and my little heater kept me very comfortable. If I had not had electricity, a down comforter would have been more than adequate to sleep comfortably.

And, as far as summer heat goes, I live in Texas, and my $89 air conditioner is more than enough, even with no insulation.

So, I wouldn't get obsessed with R-values. I really don't think you need as much insulation as you may think you do.

CD

[d30gaijin]

Caseydog,

Thank you for your response. I am converting a 6'x10' cargo; would your response apply equally to a slightly larger living area?

Again, thank you for your response it is truly appreciated.

Don

[starleen2]

Caseydog,

Thank you for your response. I am converting a 6'x10' cargo; would your response apply equally to a slightly larger living area?

Again, thank you for your response it is truly appreciated.

Don

Our ladybug is about that size and we have it insulated with 3/4 foam insulation - I can echo the same thing CD said. I've used a hair dryer as a heater in a pinch when it snowed on us - and still had to leave the window cracked!

[hunter535]

Don,

I used the Blue Dow in my CT and I am happy with it. Coldest camping so far has been 26 degrees outside and the inside was warm enough to kept the chill off. Granted, at the time all I had for a heat source was my catalytic tent heater. I went with the 1 inch foam because my metal wall studs are 1 icnh square. My only weak spot know is my floor. Not insulated yet. Not sure if I am goint to insulate or not. Rug works good for know!

Hunter

[Engineer Guy]

Having Camped in environments including a Milk Truck Van; an uninsulated 8'x8' Shed at 9,000' in the Rockies where we could 'see' our breath; a Tent Trailer; a spray foam-insulated 31' Avion at 6,100'; and now a super-insulated Solar House, I'm an admitted Insulation 'junkie'. You don't have to replace energy you never lose. My own future CT build [when our House is done] will be highly insulated simply because then a small Heater and Evaporative Cooler will handle temp extremes to maintain an internal comfort level. This will allow us to boondock in extreme temps, or relocate to cooler temps.

R Factor effectiveness ratios are simple math generally. R 6.5 Foam has ~62% better heat- or cold-stopping effectiveness [resistance to energy transfer] than R 4.0. R 6.5 is ~45% more efficient than R 4.5. Any R Factor listed has the fine print of test conditions. All Insulations are installation-dependent and imperfect typically...

What max available Insulation does is allow heating or cooling with less energy in a given space [volume]. This is why a Catalytic Tent Heater - rather than a higher output Heater - works OK in a CT that's insulated with Blue Dow.

From a Conversion Table online: 1 watt = 3.41 BTU/hour

A 1,000 Watt Hairdryer run for ~15 mins = pumping 852 BTUs into a given volume or 3,410 BTUs/hr. This is about 1/2 the output of one Little Buddy-style Heater.

A square 5'x8'x4' TD would have ~200 sq. ft. of surface area. A 6'x10' x 6' CT has about 312 sq. ft. of surface area insulated to whatever R value you decide on. Most TDs aren't square, and have less surface area for heat transfer. This is why human + dog + appliance heat would seem to work in such a small volume as a TD. For the sake of illustration, the 6'x10' CT has ~55% more surface area. It relatively has more in the real world where rounded TDs have less surface area than square TDs.

One fellow here has mentioned the very cold 'ribs' of his CT conducting 'cold' to the inside. In the overall picture, uninsulated Ramp Doors and Floors transfer heat and cold.

The Big Box Stores bring in product on Trucks constantly. So, consider pressing them to get you Dow product if that's what you want. In the temps you mention, the higher R value will translate to improved comfort while using less Propane. Heat rises, so my House Ceiling has ~2x the R value of the Walls per std practice.

I used taped-off 'Astrofoil' throughout our new House. It reflects Infrared [IR] and acts as the Vapor Barrier. A scrap piece of it outside on a person acts just like a Space Blanket in reflecting body heat. Spectacular stuff, and highly advised as the top layer to whichever Insulation you decide on. A piece of Astrofoil under our bottom sheet really helped keep us warm in the Shed at sub-freezing Fall temps. That >9,000' elevation dictated only fair weather Camping, so I never insulated.

http://www.astrofoil.net/

Just as moving air at the back of a towed CT creates lower pressure, wind creates lower pressure on the leeward side of a stationary CT. This pressure differential more vigorously moves warm air inside a CT to outside through voids. Moving air also chills CT skin a la a type of wind chill factor. Factors to consider in choosing an R Factor when Camping in the real [not theoretical] world...

DAP, or other moderately-expanding Foam, can fill in other voids and corners. Voids can add up to >15% of uninsulated surface -> heat loss.

From your Forum moniker, I take it you've been to Japan also and experienced their uninsulated, thin wall cold spaces perhaps? ;-0

[astrotrailer]

I just got back from a 4 night astronomy party in northern California with my wife.
I insulated my 5x8 trailer last year with 1 inch white rigid foam board in the side walls and
between the ribs below the roof. I also added 1 inch closed cell foam below the ribs to
make it softer on my head when I forgot to duck. I put 2 inch white foam board under
the deck and covered it with fiberglass reenforced plastic. The inside floor, ramp door and
side walls have 1/2 inch closed cell foam over the plywood and are covered in carpet.
The insulation helped keep down the heat in the morning sunshine when we want to sleep
into 11 or noon after staying up to 4:30AM looking at the stars. Last winter I added
a small Atwood hydroflame furnace to take off the chill when I observe in the winter.
My wife really enjoyed the furnace last weekend. It was down to about 36 degrees Thursday
night and she would go in the trailer and turn on the furnace to warm up. We set it
at about 50 degrees when we finally went to bed and it kicked on 2 or 3 times through
the rest of the night.

I think a cargo trailer has a lot more interior volume and the insulation and furnace is
quite useful to help keep it warm. The insulation is also great to keep it cooler if you
run an air conditioner. Our furnace pulls less than 2 amps DC when it is running so
we don't have a problem with running down the battery. We also have 160 watts of
solar to recharge the next day. We camp in the higher and dryer west so we don't need A/C
but a furnace can be nice. Last year I was using a little buddy heater but I feel safer
with a forced air furnace that pulls in combustion air and sends the exhaust back out.
With the heat exchanger we don't have any worries about CO or adding moisture.
I put in fire/smoke, propane gas and CO detectors to play it safe.

[astrotrailer]

...removed double post.

[vtx1029]

I agree that I would not fret that much about the difference in R value. Last summer while camping in yellowstone with our 8.5x18 trailer that has no insulation it (single sheet of aluminum for a roof) was 50 when we went to bed and 23 in the morning and we stayed plenty warm with just a cheap $20 space heater from walmart

[d30gaijin]

R Factor effectiveness ratios are simple math generally. R 6.5 Foam has ~62% better heat- or cold-stopping effectiveness [resistance to energy transfer] than R 4.0. R 6.5 is ~45% more efficient than R 4.5. Any R Factor listed has the fine print of test conditions. All Insulations are installation-dependent and imperfect typically...

Engineer Guy, thank you for the numbers, those are something I can understand. I did find that my local Lowe's carries the blue Dow in 1" sheets but only in 20" by 8' sheets. I'll end up with extra waste going that route (based on 16" frame centers) but it appears it will be worth the R6.5 value.

From your Forum moniker, I take it you've been to Japan also and experienced their uninsulated, thin wall cold spaces perhaps? ;-0

Nope, never been to Japan but I am well familiar with the Gaijin term. Actually the moniker was given to me by a gent in Japan based on a a long forum conversation we engaged in back in 2001 when Canon came out with their D30 digital SLR camera, the first aimed at the serious amateur photographer/consumer price level (if you could call a $3000.00 camera consumer priced LOL!). But back in those days it was a break through and my Japanese friend (Pen Pal if you will) was hooked on the Nikon D1 so we engaged in friendly banter back and forth. Based on that banter he hung the nick name on me and I have worn it proudly since.

Thank you for such an excellent and detailed response to my question.

Don

[d30gaijin]

I just got back from a 4 night astronomy party in northern California with my wife.
I insulated my 5x8 trailer last year with 1 inch white rigid foam board in the side walls and
between the ribs below the roof. I also added 1 inch closed cell foam below the ribs to
make it softer on my head when I forgot to duck. I put 2 inch white foam board under
the deck and covered it with fiberglass reenforced plastic. The inside floor, ramp door and
side walls have 1/2 inch closed cell foam over the plywood and are covered in carpet.

Jeff,

Thank you for your excellent input. I too am an astronomy buff and that is part of the plan, to take a couple of my scopes with us on our camping outings to dark sky sites.

The wife wants no carpet in the CT other than a throw rug or two on the linoleum floor we'll be installing so I need to get as high an R factor in the wall space as I can. I'll reinstall the original 3/8" plywood over the insulation then put a bright or white colored paneling over the plywood for max interior brightness.

I'm curious about being able to insulate under the wood floor i.e., the underside of the CT that will obviously be exposed to road rain/water and how to keep moisture/water from getting between the insulation and the wood floor to prevent rot of the flooring. Any thoughts?

Not to get off topic but what scopes do you use? For most of our tent camping I took along a Pentax SDHF 75mm refractor but with the CT will be taking a 6" Russian Mak and a vintage orange tube Celestron C8 along with Pentax SDHF 75 all mounted on a William Optics EZ Touch alt/az mount. I also have a vintage orange tube C14 but it's a beast and won't be going on many trips.

Don

[astrotrailer]

I first sealed the top and bottom of the deck. I put in 2x4s under the deck after ripping them to be the same depth as the steel.
I sealed the added 2x4s and then filled in all the spaces with 2 inch rigid foam. I caulked in the remaining gaps and put in
fiberglass reenforced plastic over the foam, wood and steel. I used silicone to seal the edges before screwing in the FRP into
the wood. The 2x4s also stiffened up the floor. I use the trailer to image in the winter and the insulated floor really helps keep
it warm. I think my deck is better protected than most builds.

I have a ramp door and roll in a 20 inch F5 Obsession dob that belongs to the Astronomy Society of Nevada. I keep it at my home
and haul it to as many events as I can manage. I also have a Stellarvue SV115T triplet APO refractor. When I don't have the big
Obsession, I take a smaller 12 inch Zhumell dob or my Celestron C925 SCT. The front of the trailer has a desk for holding my
laptop for running my imaging cameras and guiding my mount. I have a 130 amp hour battery that is recharged by 160 watts
of solar on the roof. I did the cargo conversion mostly for supporting several day star parties and imaging off the grid. I cover the
windows and roof vent with foam when I go to sleep and I can stay asleep until at least 11AM. This beats getting sun baked out
of a tent by 8AM.

[Trackstriper]

Back to blue vs. pink, they are both extruded polystyrene and I doubt there is any significant r-value difference between the brands. The expanded white bead board has a lower r-value, maybe around 4 per inch of thickness, and the foil faced polyisocyanurate foam is somewhat better than the extruded insulation. The extruded product, either blue or pink, will serve you well...they are durable and don't break up into a jazillion little uncontrollable beads while cutting like the bead board does. The polyiso is nice if you can find it in the right thickness.

Helpful links:

http://www.glacierbay.com/Instresult.asp

http://www.glacierbay.com/gbInsultest.asp

[d30gaijin]

Back to blue vs. pink, they are both extruded polystyrene and I doubt there is any significant r-value difference between the brands. The expanded white bead board has a lower r-value, maybe around 4 per inch of thickness, and the foil faced polyisocyanurate foam is somewhat better than the extruded insulation. The extruded product, either blue or pink, will serve you well...they are durable and don't break up into a jazillion little uncontrollable beads while cutting like the bead board does. The polyiso is nice if you can find it in the right thickness.

Helpful links:

http://www.glacierbay.com/Instresult.asp

http://www.glacierbay.com/gbInsultest.asp

Trackstriper,

Thank you for the links, some very interesting information there. Today I went for the blue (before reading the links you sent) because as best I could tell the 1" pink claims an R value of 5 and the 1" blue an R value of 6.5. Be that as it may, after reading the links you posted "claimed" and actual can be two very different numbers. Oh well, I like the blue color better even though the wife wanted pink. I convinced her to go with blue because of the higher "claimed" R value. Of course once installed we'll never see it again but it makes me feel better knowing I have blue stuff between my walls rather than pink stuff.

Don

[Trackstriper]

Don, here's an update. This week I've been working in the Boston area, a little ways from home base. After dinner tonight I cruised the Home Depot and Lowes stores to see what you were looking at with the 6.5 R-value. Both stores had a lot of polyisocyanurate insulation, I suppose folks in this area have to pay attention to their insulation like you do. There was only a small selection of extruded polystyrene and very little expanded polystyrene.

Now, Lowes had 1" thick Dow polyiso 4x8 panel that had silver foil on one side and blue foil on the other....rated at R-6.5 (Home depot had a similar product that was silver foil on both sides). Maybe that's what you got, and if so, well done. The polyiso foam tends to be a light tan/off white color and usually has a foil face on both sides to slow degradation. The pink and blue extruded polystyrene have color throughout the foam, that's how you can tell the difference readily.

What I have found interesting as I've been in different parts of the country is how the box stores will favor one type or thickness based on local demand. I couldn't find any 1" board stocked in Atlanta, but it is a standard item in South Carolina...so I bought some there while working on a project at Clemson University. When I made my earlier comment, I'd forgotten that the market varies a lot, and I'd assumed your blue board was the extruded material.

Bruce