GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Insulating the floor of 3 season room 6′ above ground

BKSP | Posted in General Questions on

We are planning on adding a 3 season room onto the back of our waterfront house in Virginia. This room will be built 6-10′ above ground as we have a sloped lot towards the water. The question we have is how to insulate as best we can given that we will be using 5 and 6′ wide Larson Scenix windows which we know will at some point be left open during pop up thunderstorms so may occasionally get wet because of this.

We want to insulate as best we can as we will have no HVAC in the room and want to get maximum use. Main question: how to handle the floor, what type of floor etc. We can use PVC planks or PT lumber, but how do we handle the possibility of getting water thru floor which would be a problem with insulation under the floor? Don’t know all the options.

Any thoughts appreciated!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. rockies63 | | #1

    Virginia. Does Virginia get humid? That's another consideration, building an insulated raised floor in a humid environment - how will the moisture vapor get out of the floor system in a humid environment?

    But! If it's a 3 season room with no HVAC why insulate it at all, especially if you are concerned about water getting into the room through open windows and pooling on the floor? I would treat it as an enclosed screen porch and use deck boards with a bug screen underneath. You could even go to a non-wood board like Trex and a hidden fastening system if you didn't want any further maintenance issues. This way you could leave the underside of the floor system open to inspect it on occasion. Insulating the floor won't really provide all that much thermal comfort in the early spring or late fall. If it was a 4 season room though I would suggest insulation.

  2. BKSP | | #2

    The reason is that I want to extend the usability of the room. VA is humid at times. Also, the windows we are using are insulated and the walls are insulated, we may want to convert the room to a 4 season room at a later time.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |