Deb,
Kind of long but some of many ideas and/or hints:
The Reflextix you are using also works great on the inside of the all the cargo storage doors and held on with Gorilla Tape. Cut the one piece Reflectix about 3/4" smaller than the door and put the tape ALL around the outside edge so it doesn't interfer with the rubber gasket. I am assuming your Laredo has a sealed and hopefully insulated underbelly as that's very important. Also adjust the cargo etc doors so they contact the seal all 360 degrees. if you can move the door or rattle it when locked, it's going to leak air.
Look carefully at the propane storage compartment on both sides, inside the RV and in the compartment itself. Many propane compartment backwalls and side/top walls are not insulated on the inside. If you can't get to the back side, lining the inside of the propane compartment with Reflectix is the next best thing. Again use Gorilla Tape as it lasts for longer than you'll likely have the 5th wheel. Remember to tape all edges and seams totally so there's no air transference. Also check the front bulkhead (back wall of the front storage compartment) to see if it's a one piece of wood construction or if it's 2 pieces with insulation between. Again, if deemed more insulation is needed, Reflectix and tape it abest you can and seal all openings around wire passthru holes and voids with Reflectix, or backed fiberglass, or caulk etc to stop air flow.
Open the refrigerator outside door and seeif there's any voids around the fridge metal to structure members or walls. Stuff any voids or again seal the openings to prevent airflow.
Very seriously check out the back of the front pin box (hitch) for any air flow voids. Tough to do but you can stuff the inside with cut pieces of block foam or even backed fiberglass insulation if you then cver it with Reflectix and Gorilla Tape so water and mist can't get in to soak up the insulation as it will sit in there and rust the steel members.
Look at the shore cord storage box area and be sure it well insulated or insulate it. Remember that outside air goes thru the same hole the powercord does and it a very sloppy fit.
Put 15" X 15" plus foam 2" thick into an appropriate sized small plastic garbage bag and tape it in place on the back side so you can't see the tape and push them into the 14 X 14 roof vents. Easy to remove when wanting to open a vent or shove back in. Don't have to remove the vent crank as it just pushes into the foam like it isn't there. The side you see will be nice and flat. We use white or cream colored garbage bags so the blend in and you won't even notice them.
Outside range vent should be clipped tightly closed if you can reach it outside or you can simply remove the inside screen in the range hood and put a plastic baggie (twist type closing gallon bag) over the screen and scotch tape it on the back side so the front side looks just like it did without the bag on and snap the screen back in. Snap it out to cook and snap it back in when done. Some of ours slide in but it still works the same way.
Take the roof A/C inside cold air return vent covers off and stretch plastic wrap over them smoothe on the side you see. We scotch tape the back side with a couple small pieces of tape just enough to keep the front side smooth and put them back on the A/C unit. Also close all A/C ceiling vents and good as you can to severely reduce rising hot air going to the roof/attic.
The established average standards for heat loss is 50% thru the roof/ceiling, 25% thru the walls, and 25% thru the floor. So, the roof is the most important for insulating, the floor is next as it has much less square footage area than the walls, and then comes the walls. You can't pressurize a building/RV or create a vacuum in a building/RV. If air is prevented for coming in, air won't go out. Insulation limits thermal transference, the more the better. Reflectix, foil bubblewrap, etc reflects both heat and cold and in opposite directions and is excellent as a vapor barrier at the same time.
For window thermal treatments, we always order atorm windows on our RV's. If not offered, I make my own from .220 (so called 1/4" but it's not) Lexan or even polycarbonate and they work as good or better than OEM glass storms. They weigh a lot less and don't break as easy as glass but you have to be a little careful not to scratch them. Your using of Reflectix on your windows sure does work good and are cheap to make but as you noted, you can't see thru them etc.
Just a few of many cheap and easy ways to weatherize an RV so it as comfortable or evn moreso than a well built home. A lot also depends on how well the RV is built and was insulated but there's so much you can do the make it still a lot better.
We have camped in way below zero temps in the U.P. and Canada for days many times and have never yet had a single thing in our weatherized RV's freeze including any and all water lines. Also you will find there are zero drafts or cold floors in the RV and so little sweating in the walls and ceiling which means must less or no mold, mildew, or rot over time.
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