Any problems with unfaced insulation on exterior walls?

[Lineman North Florida]

I am to the point that I am fixing to insulate my hunting camp walls, I used house wrap on the exterior over the OSB and am thinking about using unfaced insulation on the walls due to cost and was wondering if faced insulation would create moisture issues , so my real question is can I get by with unfaced insulation in the exterior walls without causing me any issues with moisture down the road?

 

[RNeumann]

Faced insulation is typically old school thinking and or a retrofit situation without house wrap. Fiberglass is terrible with any moisture or air movement so that was another theory about why paper faced was used.

Bottom line- I wouldn’t use it or recommend it in your situation.

 

[Deere Dude]

I am to the point that I am fixing to insulate my hunting camp walls, I used house wrap on the exterior over the OSB and am thinking about using unfaced insulation on the walls due to cost and was wondering if faced insulation would create moisture issues , so my real question is can I get by with unfaced insulation in the exterior walls without causing me any issues with moisture down the road?

Unfaced will work fine. But you will need a plastic vapor barrier on the inside. Either paper faced insulation to serve as the vapor barrier or a plastic covering will work just fine.

 

[RNeumann]

Unfaced will work fine. But you will need a plastic vapor barrier on the inside. Either paper faced insulation to serve as the vapor barrier or a plastic covering will work just fine.

Very old school- not recommended for years.......house wrap has a “perm” or “permeability” number. Plastic with a zero perm number was trapping moisture.
Check out buildingscience.com

 

[Deere Dude]

Very old school- not recommended for years.......house wrap has a “perm” or “permeability” number. Plastic with a zero perm number was trapping moisture.
Check out buildingscience.com

That I will do. I built 3 houses using that technique over the last 40 years and never had any moisture problem. Maybe wrap has changed lately.

 

[joeu235]

Since you are in the south, you should dry to the inside of the house, so no moisture barrier on the inside is actually correct.

 

[Lineman North Florida]

Thanks, for the reply's, I went over to a builder friend of mine who is building his own personal house down the road and he put in un-faced batts in his own personal house and said as long as house wrap is used on the exterior that un-faced batts are fine and an interior moisture barrier is not needed, that's what I will be using. Thank's again. Charlie.

 

[Storm56]

I built a new home in 2007 and used blown in insulation in the walls and ceilings. House wrap on exterior. Code mandated a moisture barrier on the walls and as such used plastic, ceiling was fine without one. I have had no problems with moisture in the home. In fact during dry periods in the winter I need to run a humidifier as there is a lot of hardwood in the home including ceilings and floors.

 

[PILOON]

Always a good sealed (taped) moisture barrier on the inside. On the outside you want something that breathes like house wrap.

Poly vapor barrier for inside is not the best choice as I have noticed that any exposure to UV simply deteriorates it and since it is a hunting shack/blind I doubt that you will cover it over.
Look for a mylar type product that resists UV.

 

[RayfromTX]

The original poster is in Florida. No building in the gulf coast region should have a vapor barrier on the interior face of the walls. Many hundreds of millions of dollars worth of damage has been done in the gulf coast region because of the use of interior vapor barriers. Hotels and motels by the hundreds have been damaged because the vinyl wallpaper trapped water vapor in the walls.

The dew point of the air outside is around 76 degrees or even higher. A house wrap such as tyvek allows this water vapor to pass freely through it. That may be a good thing in a cold northern climate but NOT IN FLORIDA! I would argue that you should never use an interior vapor barrier but in a cold northern climate it is routinely done successfully but NOT IN FLORIDA! When you maintain the interior space at a temperature lower than the dew point of the outdoor air and allow it to enter through a permeable house wrap and then stop it in the wall with an interior side vapor barrier on the cool interior side of the wall, you will fill your walls with mold. I have had many many people tell me that they have done it without any problem but the problems are there. The plastic hides the problem inside the walls where it leads to mold and rot. over and over and over.

OP, I would recommend that you use a latex paint on the inside of your exterior walls. Make sure you do not use products on your interior side of your exterior walls that are a vapor retarder. Unfaced will be ok but fiberglass insulation is my last choice. Use it if you want but there are better choices. For your hunting camp, no problem. Build the building as air tight as you possibly can and make effective use of properly sized exhaust fans for the management of moisture that is created by cooking and showering.

Tomorrow I am going once again to inspect and help in the planning of the remediation of the moisture problems in the walls of a very expensive home due to an interior vapor barrier and it is 150 miles from the gulf. The vapor barrier in this home is in the form of a foil faced cardboard sheet that is intended for the exterior of the wall but in this home was used as a backer for interior 3 coat plaster. It is a very expensive failure. The house has fiberglass insulation and tyvek on the outside of the plywood sheathing. The discussion will be about how to remove the vapor barrier, either by removing the masonry from the exterior or by gutting the interior of the building.

One other thing that I found interesting. They have issues in their interior walls as well. Usually we don't see this because people don't put vapor barriers in interior walls. In this case, they used the same product to back up the plaster on the interior walls. You may ask where the moisture came from. It was carried from the exterior walls into the interior walls through air leakage. It worked like this. When the air conditioning is in a vented attic the leakage in the supply ducts happens outside the living space. This creates a negative pressure in the living space and air comes in through the leaks in the exterior walls and elsewhere. The air travels through holes for wiring and other gaps in the framing where the interior walls meet the exterior walls. It then enters the space through the electrical outlets on the interior walls where they aren't sealed in the same way they are in exterior walls. As the humid outside air travels through the interstitial spaces it deposits on the cool surfaces inside the walls of the air conditioned living space. Since it is trapped between two vapor barriers it deposits on the surfaces just like a cold beer can.

It took over 10 years before they knew there was a problem. The house is 17 years old now and so much moisture has built up that the home is going to be almost demolished to repair the damage.

Please be careful about giving advice outside your field of expertise. It can be quite dangerous to give advice intended for zone 5 or 7 to someone in zone 2.