Thread: Insulation-Vapor Barriers for Exterior Walls Above and Below Grade

As I posted on another thread entitled "Showers", I am having to relocate, potentially new construction, due to mold illness from "toxic black mold" and have to be very careful about re-exposure.

I have been reading this board and others and have a few questions or so about insulation. I appreciate the opportunity to post here, and please pardon my ignorance! Thank you.

I am reading so much conflicting info about vapor barriers for external walls sub and above grade.

I am getting no to any vapor barrier (I think mostly below grade but not clear on that 'no") and I am getting vapor barrier exterior to insulation and drywall placed on top of that: warm side in winter.

Two problems here I don't get:

(1) Exterior walls, If this applies at all: Warm side Winter.. what about warm side summer? What happens to condensation in that case or is this not an issue for above grade exterior walls ( I may be really embarrassed to find the vaopr barrier is not standard or used at all in these application anyway?)

(2) Below Grade: again.. some say no vaopr barrier and some say Warm side Winter. I can see both points of view.. If water is coming through wall or moisture.. the that vapor barrier will trap it in. But how to protect drywall? What about foam board on the concrete wall interior? I am reading this is infact air permeable and then I am reading this acts like a vaopr barrier and some think this is great and others don't find this a good solution, either.. something about that Warm in Winter issue.. my mind is now turning to miush at this point...

I am seeing these to examples, neither with a vapor barrier IF the foam is not acting as a vapor barrier, rather a way to insulate and thus warm the concrete walls.

How to Finish a Foundation Wall | The Family Handyman

Any thoughts, info would be very much appreciated.

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Originally Posted by Robin Alexander

As I posted on another thread entitled "Showers", I am having to relocate, potentially new construction, due to mold illness from "toxic black mold" and have to be very careful about re-exposure.

I have been reading this board and others and have a few questions or so about insulation. I appreciate the opportunity to post here, and please pardon my ignorance! Thank you.

I am reading so much conflicting info about vapor barriers for external walls sub and above grade.

I am getting no to any vapor barrier (I think mostly below grade but not clear on that 'no") and I am getting vapor barrier exterior to insulation and drywall placed on top of that: warm side in winter.

Two problems here I don't get:

(1) Exterior walls, If this applies at all: Warm side Winter.. what about warm side summer? What happens to condensation in that case or is this not an issue for above grade exterior walls ( I may be really embarrassed to find the vaopr barrier is not standard or used at all in these application anyway?)

(2) Below Grade: again.. some say no vaopr barrier and some say Warm side Winter. I can see both points of view.. If water is coming through wall or moisture.. the that vapor barrier will trap it in. But how to protect drywall? What about foam board on the concrete wall interior? I am reading this is infact air permeable and then I am reading this acts like a vaopr barrier and some think this is great and others don't find this a good solution, either.. something about that Warm in Winter issue.. my mind is now turning to miush at this point...

I am seeing these to examples, neither with a vapor barrier IF the foam is not acting as a vapor barrier, rather a way to insulate and thus warm the concrete walls.

How to Finish a Foundation Wall | The Family Handyman

Any thoughts, info would be very much appreciated.

Well you lost me on most of your post...

If you have a concrete foundation/basement then you will have a waterproofing on the exterior that will stop water from penetrating the concrete. Then on the interior you will have your stud wall with insulation and the drywall. If you use batt insulation the Kraft paper will face inward towards the heated part of the home.

Above grade the rest of the home will have water resistant barrier (WRB) on the wall sheathing and then the cladding. The interior drywall will have insulation in the exterior stud walls and then the drywall. In some areas they install a wind barrier over the insulation and then they install the drywall(I do not like this method).

Follow the instructions on the insulation. With faced batt insulation, it will tell what side faces what direction. With some installs you will not have any facing on the insulation. I think you are getting confused with Water/moisture barrier and Vapor barrier.

The interior is the heated or warm area; think conditioned area if it makes it easier to understand.

Robin, my suggestion is to hire an experienced home inspector to be your consultant during and even before you build your home. If you are in VA you have some very knowledgeable folks in your state that could help you. It is very common for folks to hire inspectors as consultants for this type of work, I have three going on right now.

As far as conflicting information on the Internet, well it is the Internet! About half of what you read is questionable or just an opinion.

Robin,
Maybe you should consider constructing your home with metal framing instead of wood. In any case I suggest you (1) make sure your home designer is completely familiar with your medical requirements (2) Spend a lot of time identifying and vetting a custom builder who is small enough to devote very personal attention to your home. (3) Assure that your contract with the builder gives an inspector free reign during the construction. (4) Spend a lot of time identifying and vetting an inspector who can be heavily and frequently involved in your project.

You will learn much good stuff asking questions on this forum, but you will not learn all you need to know to protect you with your specific needs. A good small custom builder and a good inspector fairly compensated and enabled/allowed to do what they know how to do will take your problems as their own and provide a safe home for you.

I would recommend a good indepth study of vapor barriers beginning with Building Science Corporation Vapor Barrier Guidance — Building Science Information
Dr. Joe L. explains the science behing vapor and moisture transmission across the building assembly.
As Scott aluded to, an overall view of the building structure is needed, not just "where does the vapor barrier go." The climate, water proofing, insulation, and structure all need to be considered in the equation.

Thank you for the information. I will be reading! Any tips for finding a good home inspetor in my area? We did contract out our home but did not hire a building inspector to go through the process with us.

A problem here is finding land to build on that has not already been purchased by corporate builders. I found one (corporate builder, not sure I can name) who will make some changes for me but those are limited. For example, I can get low VOC paint with them and may be able to exchange a tiled shower for an enclosure and possibly will not benefit from any cost differential if there is one. This one does not use a plastic barrier or tar paper behind backer board but would do that for additional cost if I ask. I might be able to choose insulation types and request a moisture barrier (I am confused on the diff between mositure and vapor barrier...) under tile or hardwoods.. if even desired.

The same builder and no telling how many others in this area were using t-ply for exterior walls up until 2006-7 and green board to back tile (at least with a wax barrier), though not sure how efficient. This has elimnated in our minds most resales for us.

You all are absolutely correct; I need a good building inspector to help with this process, just not sure how to identify. Will start looking but tips would be appreciated if you have any to share.

Originally Posted by Robin Alexander

Thank you for the information. I will be reading! Any tips for finding a good home inspetor in my area? We did contract out our home but did not hire a building inspector to go through the process with us.

A problem here is finding land to build on that has not already been purchased by corporate builders. I found one (corporate builder, not sure I can name) who will make some changes for me but those are limited. For example, I can get low VOC paint with them and may be able to exchange a tiled shower for an enclosure and possibly will not benefit from any cost differential if there is one. This one does not use a plastic barrier or tar paper behind backer board but would do that for additional cost if I ask. I might be able to choose insulation types and request a moisture barrier (I am confused on the diff between mositure and vapor barrier...) under tile or hardwoods.. if even desired.

The same builder and no telling how many others in this area were using t-ply for exterior walls up until 2006-7 and green board to back tile (at least with a wax barrier), though not sure how efficient. This has elimnated in our minds most resales for us.

You all are absolutely correct; I need a good building inspector to help with this process, just not sure how to identify. Will start looking but tips would be appreciated if you have any to share.

What part of VA are you in? Let me know and I can most likely refer some to you.