Foil face batt insulation

[Rider Rick]

When do you install batt insulation with the foil to the cold side of an exterior wall?

 

[mark handler]

In colder climate areas, vapor retarders are placed toward the heated or conditioned side of the wall.

This is done to reduce water vapor penetration into the wall from the building interior.

Conversely, in predominantly hot, humid climates local place the vapor retarder toward the outside of the wall cavity.

 

[mark handler]

http://www.insulate.org/tb6.pdf

Vapor retarder should be installed at the warm-in-winter side of the framing .

In hot, humid climates, vapor retarders are sometimes omitted or installed outside the insulation .

 

[RLGA]

It is never installed on the colder side of an exterior wall.

 

[Rider Rick]

What would be the correct way to install in Los Angeles?

 

[mark handler]

What would be the correct way to install in Los Angeles?

What CA energy code climate zone? There are 16 climate zones in CA. I belive there are more than eight in the So. CA area.

6 in LA county

So it depends.....LA has deserts, beaches and mountains

Typicaly toward the outside of the wall cavity.

 

[Rider Rick]

Mark,

It looks like #6 South Bay Redondo Beach.

 

[mark handler]

Mark, It looks like #6 South Bay Redondo Beach.

Toward the outside of the wall cavity.

 

[Rider Rick]

Thank you Mark,

Does heat go to cold with a dew point around 59 degree.

 

[mark handler]

Talk to your Mechanical Engineer

I only use vapor barriers when required.

I don't like to trap the moisture in the wall, floor or attic.

 

[brudgers]

Is the foil being used as a radiant barrier?

 

[tmurray]

Does heat go to cold with a dew point around 59 degree.

You will need a psychrometric chart, your inside design temperature and your humidity level (typically from 20%to 40%). this information will tell you at what temperature the dew point is.

Now the hard part, in order to determine where in the wall assembly your vapour barrier needs to be placed you need to know the heat loss from the building through all the portions of the building envelope (walls, ceilings, exposed floors, perimeter of concrete slab, ect.) you also need to know all of the forms of heat gain (solar heat gains through windows, doors walls, and ceilings, gains from people and equipment, ect.) once you have all this information you should be able to pinpoint exactly where your vapour barrier must be placed within your wall assembly to prevent condensation from forming on the inside of your wall.

 

[Rider Rick]

I'm not sure what the foil is being used for.

The foil is on the inside of the shear wall plywood with building paper on the outside.

This building is going to be new classrooms at a public school.

 

[brudgers]

I'm not sure what the foil is being used for. The foil is on the inside of the shear wall plywood with building paper on the outside. This building is going to be new classrooms at a public school.

If it is being used as a radiant barrier, it doesn't matter which way it faces. The airspace is provided by the batt insulation.

Assuming it is on batts.

 

[Rider Rick]

Update:

Job site visit today

.

Under insulation section J.

Stud Framing: Place foil side of thermal batts toward inside of building by attaching at 6 inches oc.

1.Batts under framing: Attach flanges to studs at 4" centers and ensure batt facings form continuous vapor barrier. Provide tightly stretched string wires along center of horizontal or sloping batts where support spacing exceed 16" on centers. Install batts in exterior walls with vapor barier facing room.