Soon I will be removing a lot of the wood lap siding on our 1938 house and replacing it with fiber cement lap siding. The wood siding is in poor condition and we are adding a room on the back of the house which would make it impossible to weave in the fiber cement with the old wood siding. Anyhow, I'd like to add insulation to the walls from the outside while I have the siding removed. Currently the walls are not insulated. I live in northern California and the walls are standard 2 x
4 studs, no plywood sheathing between the studs and the siding. I was planning on using R-13 batt insulation but don't know which type- unfaced, kraft paper or encapsulated in plastic. My preference would be in order- encapsulated, kraft paper and then unfaced. I plan on covering the insulation with either house wrap or 15 lb. roofing paper. Is there any reason not to use the plastic encapsulated insulation, stapled to the outside of the framing studs and then cover it with either Tyvek or building paper and then the Hardiplank lap siding? The interior walls are lath and plaster. Thanks.
In northern California I would guess you should have the vapor barrier towards the inside. Check local codes or local builders. I would make sure it does have a vapor barrier. That leaves out the encapsulated stuff as the plastic is intentionally compromised to allow ventilation.
Not positive but I always thought vapor barrier goes to occupied side. Reading below shows me correct for my area. It could be different for Florida.
From Owens Corning, everything you wanted to know.
Faced and Unfaced Insulation
"Facing" refers to material applied to one side of a batt of insulation to prevent moisture from passing through the insulation and condensing on exterior or interior walls. This facing is called a vapor retarder. Insulation that does not have a vapor retarder applied to it is called "unfaced."
Vapor Retarders
Showers, cooking, washing and even breathing can put a surprising amount of moisture into the home-from 5 to 10 pounds a day! Washing and drying clothes indoors can add another 30 pounds. Vapor retarders help control the amount of moisture passing through insulation and collecting inside exterior walls, ceilings and floors.
In the winter, any moisture that passes through to these surfaces can accumulate and condense on the cold inner sides of exterior surfaces. Eventually, this condensation may blister the outside paint, form stains on drywall ceilings or walls, or even damage your house structure.
Whatever vapor retarder you choose, remember this important rule of thumb: In heating climates, the vapor retarder is always installed toward the warm-in-winter side (living area) of the house.
(In the Gulf Coast and Florida, local building practice may not call for an interior vapor retarder, or may call for the vapor retarder to be installed toward the outside in exterior walls. See installation instructions on package.)
There are three types of vapor retarders:
Kraft-faced Kraft paper attached to insulation with a thin coat of asphalt.
Foil-faced Foil-backed paper attached with a thin coat of asphalt.
Polyethylene A separate 4- to 6-mil polyethylene film applied over installed insulation.
Note: Never leave faced insulation exposed. The facings on kraft- and foil-faced insulation will burn and must be installed in substantial contact with an approved ceiling, wall, or floor construction material to help prevent the spread of fire in the wall, ceiling or floor cavities.
Insulating Irregular Spaces
Insulation must be gently fitted around pipes, wiring, electrical boxes and heating ducts - compressing the insulation will reduce its R-value. There should be no gaps or spaces between insulation pieces. These are places where energy would be lost for the life of the house.
On Wed, 08 Jun 2005 15:02:38 GMT, Joseph Meehan wrote: [vapor barrier goes on which side of insulation?]
Where it gets really confusing to me is areas that heat in the winter, and A.C. in the summer. The "warm side" changes with the season. In my area the vapor barrier goes on the inside even though (IMHO) the warm side is outside for more of the year, and the inside air while heating is typically _very_ dry.
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