Why Insulate the Floor?

[Tomterrific]

I used a heavy 3/4" ply floor bolted directly to the trailer frame. Why would so many folks sandwich insulation between two pieces of heavy plywood? Heat goes up and we sleep on a thick mattress so I doubt there is any comfort involved.

Tom, the curious.

[DrewsBrews]

Moisture control could be one reason. Condensation can build up on uninsulated surfaces during cold days and wick up unto your mattress or bed linens.

A DIY retrofit could be sections (small enough to get in the door) of foam insulation with a thin ply/luan glued on to prevent smashing in the insulation over time kneeling/sitting.

I have also seen mats of closed cell foam used for this (similar to a thick yoga mat). This could help comfort too if you can feel the floor through the mattress still.

[aggie79]

The question about insulating or not insulating a floor (or walls or roof) is almost like debating political party preferences.

If you camp in dry areas and/or areas with little temperature variation, insulation is provably not needed. On the other hand, If you camp where there are large swings/differentials in temperature and humidity (where we live and camp), an insulated floor (and walls and roof) minimize condensation inside the teardrop. If you don't have an insulated floor when camping in these conditions, condensation can occur in the mattress. That said, if you partially lift you mattress during the day to allow air to circulate, any moisture from condensation should dissipate.

My insulated floor is a "sandwich" of 1/4" plywood, 3/4" framing and insulation, and 1/4" plywood. The weight is approximately the same as 3/4" plywood. Others have successfully made an insulated floor with 1/4" or 1/2" plywood over 3/4" framing and filled the voids with insulation.

[DrewsBrews]

.... That said, if you partially lift you mattress during the day to allow air to circulate, any moisture from condensation should dissipate.

A good idea anyway even if it doesn't affect your comfort. I have heard of foam bedroom mattresses placed over plywood indoors growing mold just from perspiration build up since the mattress can't breathe through the plywood.

[lrrowe]

If you camp in cold areas, I believe the cold air under the trailer can move through an uninsulated floor. Or more correctly stated, warmth moves to the cold so my trailer heat is moving to the cold area under the trailer. I have a 3/4 in floor, 1 1/2 foam insulation and then 1/2 in subfloor over that. The temp of my floor when checked reads the same as the walls and the ceiling. I am well insulated and ready for the cold weather. I also heat with the water from a 6 gal RV water heater set at the lowest setting.

But then again, I am in a CT, while TD'rs have a mattress on the floor and do not have the same issues as I do.

[Tomterrific]

We just went on a week long camping trip where the night time temperature was in the 40's and 30's. I did think about moisture building on the bottom of the futon mattress we use but all was good. I have thin carpet tiles on the floor so this probably gives some air space insulation. I don't believe the insulation is needed and consider it 'over built'.

Aggie, I read your sandwich is very light weight, I can understand a light stiff structure. My roof is made the same with 3/4" ribs and styrofoam insulation between underlayment. We had extremely heavy rain one night in Kentucky, cold all nights. We were in NC by the Smokies. We have allot of ventilation in our tiny camper. Two jaulosie windows, a roof vent and door props to crack open the doors 3". The way we like to sleep, with much ventilation, might be why we have never had a condensation problem.

Tom

[bobhenry]

SNOW !

[halfdome, Danny]

Tom, I insulated the floor on my first teardrop and ditched the extra work after that.
I put plam (plastic laminate) on both sides of the floor.
We don't camp in severe cold weather and the floor is 18" above ground and the chassis is covered with the side walls.
If and when we think we need an insulated floor I have two half sheets of 1/2" foam insulation with white duct tape to protect the edges.
I just slip them under the mattress and all is well.
It's a good idea, no matter if you insulate or not, to annually remove the foam mattress, spray it with bleach and allow it to air dry.
That will kill any possible mold spores since we all put off moisture when sleeping.
Danny

[Tomterrific]

9grand, Okay, I see your point. :-) Too cold for us! Danny, I did remove the futon when we got home as our son uses it for a couch in his room.

Tom

[sincere01]

The other thing to consider is though heated air typically rises as its less dense than air that is relatively colder, heat wants to dissipate from where there is more of it to where there is less. When you have air that can easily move under your trailer that is colder than inside, a lot of that heat will find its way thermal bridging through the plywood and being pulled away by the air moving underneath. A small layer of insulation can significantly minimize this effect.

[lrrowe]

The other thing to consider is though heated air typically rises as its less dense than air that is relatively colder, heat wants to dissipate from where there is more of it to where there is less. When you have air that can easily move under your trailer that is colder than inside, a lot of that heat will find its way thermal bridging through the plywood and being pulled away by the air moving underneath. A small layer of insulation can significantly minimize this effect.

What I was trying to say...but you did it better.

[kayakdlk]

I did it to save weight. I used 1x3 pine frame with 1/8 plywood on both side and 3/4 foam in between. My floor is 5'x10' and I could easily pick it up. With the SIP panel construction I could also stand on it.

Dan

[lrrowe]

I did it to save weight. I used 1x3 pine frame with 1/8 plywood on both side and 3/4 foam in between. My floor is 5'x10' and I could easily pick it up. With the SIP panel construction I could also stand on it.

Dan

That is a great method is it not?

[MtnDon]

If you insulate the floor by building a sandwich of plywood / rigid foam sheet / plywood, like a SIP, you do not need any framing withinthe field of the floor. Only 2x around the perimeter, unless you have a need to screw something down to a solid piece of wood. The foam has sufficient density to not be crushed. Many foam infilled floors seen here have a web of 2x sorta like floor joists. It is not needed. Houses are built on slabs with the concrete poured directly over one or two inches of foam.

[noseoil]

My floor is similar to Dan's. Here's a picture of the framing being glued up.



It's 1/8" baltic birch on the top & bottom, with 3/4" foam on the inside sandwiched between the skins & 3/4" poplar as the frame. I added a few extra pieces of wood to reinforce where the weight would be on an open span without any steel under the wood. The battery is in the galley, so there are blocks there & a couple of smaller ones to act as the eye-bolt hard points for the battery box hold-downs. The conduit runs have a block for solid wood to drill through, the frame bolts have solid wood as well. Any penetrations have plastic bushings set in epoxy to hold them in place (the conduit & battery box bottom vent).

Here's the frame with a little more blocking in place but prior to the insulation going down & the top skin.



Deck with the top layer of 1/8" in place. Still pretty light & very strong.