Insulation and Barriers

1. Soundproofing

The most common form of soundproofing for a conversion is automotive butyl and foil sound deadening (link). It has a sticky side and a reflective side; remove the sticky paper and place it in the center of a panel or surface. Only 25-50% of the surface needs to be covered for the desired effect, so no more than 50SF should be needed for a standard sized van. After it’s placed, use a roller like this one (link) to press the deadener until the patterns on the foil surface are smoothed out.

Now this isn’t the type of soundproofing where people outside the van can’t hear what’s going on inside. Sound deadener is designed to reduce engine noise and road noise. Besides sound deadener, certain types of insulation and surface materials can reduce road noise and muffle sounds coming from inside the van. Closed cell foam and thinsulate are great insulating materials because they have soundproofing properties as well.

2. Insulation for Walls, Ceiling, and Floor

Insulation can be a contentious subject among vandwellers, but a few fundamentals are indisputable. There are 3 types of heat transfer to be mindful of: convection, radiation, and conduction. Convection is where heat is transferred through a gas or moving liquid, like using a fan to move cool air into a van and warm air out. Radiation is where contact is not required, like feeling warmth from the sun. Conduction is where heat is transferred through solid materials, like the inside wall of a van feeling hot to the touch from being in the sun all day.

Reflective insulation (ie. Reflectix) only slows down radiant heat; if the reflective portion is in contact with a wall, it won’t work as intended. An air gap between the reflective insulation and wall is needed. Materials like Reflectix are great for covering windows to reflect outside heat from the sun and inside heat from a heater.

All other insulation in a vehicle is installed to slow down conductive heat transfer. It doesn’t completely stop heat transfer; no matter how much insulation you have, the inside of a vehicle will eventually reach the outside temperature unless you have a heater or AC.

The effectiveness of insulation is measured by its ‘R-value’. It’s cost, rigidity, and resistance to moisture and mold should be considered.

Insulation Type R-value per 1” Structure Absorbs Water? Cost for 1” over 100 SF Notes
EPS board 3.85 Rigid Yes $41 Can break down over time
XPS board 5 Rigid No $72 Great for floor
Polyiso board 6 Rigid No $71 Great for walls, ceiling
Closed cell spray foam 6.5 Foam No $110 Great for gaps, structural ribs, hard to reach places
Reflectix 1 Flexible sheet No $37 Great for window covers
3M Thinsulate 3.2 1.8” flexible sheet No $250 Low R-value per cost
Fiberglass 3.7 3.5” thick rolls Yes $16 Harmful to breathe in
Denim 4.2 1.6” thick rolls Yes $112 Environmentally friendly
Mineral wool 4.3 3.5” thick batts Yes $132 Easy to work with

XPS and polyiso rigid boards are cost effective and do not absorb water. XPS is recommended for the floor because it has a higher compressive strength than polyiso, which is sufficient for walking on. Polyiso may come with a reflective side, so these should be installed if there will be a small air gap. First create paper or cardboard templates of the spaces in the wall, and then use those to cut the insulation with a handsaw or jigsaw.

You can glue polyiso insulation to the walls by spraying closed cell foam along the edge of the boards and holding them to the wall. Standard packing tape can keep them adhered to the van ceiling.

Closed cell foam can be used to fill in hard to reach places; it can be used for insulating an entire vehicle, but this would require a full kit and an intensive installation (can be $400 or more).

Conduit can be placed along the floor between insulation so it’s easy to install wiring across your van.

Don’t forget to insulate doors as well!

3. Waterproofing

Some vehicle dwellers add a thin layer of plastic as a waterproofing layer either over or under wall insulation. Theoretically, it would be great for keeping your insulation and bare metal walls from getting wet, which can potentially lead to mold and rust. However, like hiking boots, water may find a way in and then get trapped inside. This isn’t necessary if you regularly ventilate your vehicle.

4. Window Covers and Partition

Window covers are essential for insulation and privacy over any vehicle windows. Window covers can be made with Reflectix on one side and black cloth on the other (cloth for privacy, Reflectix for reflecting solar heat out during the summer and van heating in during the winter). Sew magnets (link) inside the covers or Velcro on top of the covers to keep them up.

A partition for privacy can be made with insulating black-out curtains on a ceiling track and magnets on the edges.