Best Insulation Thickness for Walls in Mild to Cold Climates

[NeilYoung]

i was originally thinking of using 2” xps in my walls. while watching tons of build videos, it seems folks are using 1/2” to 1”.
i dont have plans to sleep in negative temps but teens and 20’s are possible. plus im in texas so….

where’s the sweet spot between not enough and too much?

 

[Pmullen503]

Because of the need to ventilate the small volume inside a TD, you rapidly get to the point of diminishing returns for insulation.

If you are using commercial doors and windows, I wouldn't make the walls so thick that you'll have trouble mounting them just to make room for more insulation. Also, using a skeletonized 3/4 plywood core with the voids filled with 3/4" insulation is very popular. For most, that seems to be adequate insulation.

 

[NeilYoung]

thanks. ill do some research on that.

 

[Tom&Shelly]

We used skeletonized 3/4 inch ply walls with 1/4 inch ply sheets on either side. We filled the voids with 3/4 inch foam. For the ceiling/roof, we used 1 1/2 inches of foam. That has always been quite sufficient.

Coldest night we had was last year West of Austin, where it got down to the low 20's (maybe teens). We were comfortable with an electric heater (run off of shore power) and a wool blanket, with the windows and skylight cracked for ventilation. If we had a Propex propane heater, I'm sure that would have worked too.

Coldest night without shore power was below freezing at Chiricahua NP in Southern Arizona one January. Warm enough once we settled in, but a propane heater would have been nice insurance on that occasion.

Tom

 

[Tony Latham]

I find that 3/4's in the walls and floor is fine, plus 2" in the ceiling.

Keep in mind, 3/4" foam board can sometimes be hard to find.

Tony

 

[NeilYoung]

thanks!

 

[dt400]

My build is not going to have any wood in it. well not where it matters at least.
Virtually every camper I've dealt with has had rot issues unless the owner is very vigilant in doing inspections and re-cualking/repairs.

I chose 2" foam as the structure and will have chemically bonded exterior and interior fiberglass shells. The 2" just adds rigidity, it's 8 times more rigid and comes in the 25 psi density vs the 15 psi for thinner versions of the Owens Corning Foamular ins.
I doubt I'll ever camp in temps where I'll need the actual "R" value of the walls but since this is my first build I wasn't sure where I could simplify the design so it's probably a bit of overkill.
I will have issues with the windows but the doors should just make the thickness, but figured I'd deal with that at that point.

Darrell

 

[Tony Latham]

Virtually every camper I've dealt with has had rot issues

Welcome to the U.S. RV industry. They specialize in making a product that will reach the end of the three-year warranty.

A properly built camper will not rot, just like your home.

Tony

 

[Pmullen503]

If you're building a foamie, then go with 2" XPS for structural and ease of construction reasons. You'll have more insulation than you need.

If you need to, you can rout a recess round the windows to thin the wall in that area. Most people frame the inside of the opening with wood to attach the window frame.

 

[dt400]

Welcome to the U.S. RV industry. They specialize in making a product that will reach the end of the three-year warranty.

A properly built camper will not rot, just like your home.

Tony

I agree with you about the RV industry. All but one or two make complete crap with zero QC.

However, your home will definitely have rot issues if maintenance isn't kept up....both inside and outside. It's wood...it will rot if not taken care of.

Darrell