This is weird... I click on this insulation-heavy conversation today, of all days.

I've got a storage room in the basement, the door of which has been blocked by the washing machine for nearly a decade. I've known it's full of junk, just haven't gone in there.

Well, I went in this morning because a friend with a truck offered a trip to the dump.

After clearing out an over-loaded half-ton worth of old lumber and junk furniture, lined up against the back wall of the room is 11 full, unopened, man-sized packages of pink insulation bats!

I stone-cold forgot I bought them for the attic - 9 years ago - when I noticed the original 1950's insulation up there was degraded.

After thinking about it, I know why I left the insulation down in that room. Getting rid of the old insulation is going to be a disgusting job.

jamiepan (imported) wrote: Fri Oct 14, 2022 7:24 pm This is weird... I click on this insulation-heavy conversation today, of all days.

I've got a storage room in the basement, the door of which has been blocked by the washing machine for nearly a decade. I've known it's full of junk, just haven't gone in there.

Well, I went in this morning because a friend with a truck offered a trip to the dump.

After clearing out an over-loaded half-ton worth of old lumber and junk furniture, lined up against the back wall of the room is 11 full, unopened, man-sized packages of pink insulation bats!

I stone-cold forgot I bought them for the attic - 9 years ago - when I noticed the original 1950's insulation up there was degraded.

After thinking about it, I know why I left the insulation down in that room. Getting rid of the old insulation is going to be a disgusting job.

Or, if you have enough room, leave the OLD insulation there, and install those bats over it.

Losethem (imported) wrote: Sat Oct 15, 2022 1:55 pm Or, if you have enough room, leave the OLD insulation there, and install those bats over it.

Is that okay to do?!

I'd totally do that, but I figured the old stuff would kinda HAVE to go.

If I can just lay the new over top (I just checked, there is room), I'm gonna do that.

If it's only been there 9 years, and it looks OK, use it.

jamiepan (imported) wrote: Sat Oct 15, 2022 6:28 pm Is that okay to do?!

I'd totally do that, but I figured the old stuff would kinda HAVE to go.

If I can just lay the new over top (I just checked, there is room), I'm gonna do that.

I think the only risk is having gaps in the new insulation, but more is always better. Just make sure the vapor barrier (paper side) is pointed toward the inside of the house as if you were laying it on the floor with the fiberglass pointing on top paper underneath. The vapor barrier ALWAYS faces towards the heated space.

THE DIFFERENCE BETWEEN AIR BARRIERS AND VAPOR BARRIERS

https://www.ecohome.net/guides/2316/the ... -barriers/

It is important to distinguish between air barriers and vapor barriers

The job of a vapor barrier is to prevent vapor diffusion, and the job of an air barrier is to stop air leakage through differences in air pressure.

A wall system should have one vapor barrier, but can have many air barriers.

A vapor barrier can act as a very effective air barrier, but an air barrier does not (and should not) always stop vapor from difusing.

A wool sweater for example, is a good choice of natural insulation and will keep you warm when there is no air movement, but will allow the wind to howl right through it. A wool sweater with a raincoat will keep you warm but hold moisture inside and soak your insulation. A wool sweater with a windbreaker will keep you warm, stop the wind from stealing your heat, yet allow moisture to difuse through it.

So think of a windbreaker as an air barrier, and a raincoat as a vapor barrier. That is about as far as I can stretch the human to house analogy, hope it helps.

In order to prevent condensation from forming, a vapor barrier should be placed on the warm side of your insulation to stop warm, moist air from condensing on a cold surface inside your wall.

In cold climates like Canada, for most of the year the vapor barrier should be on the inside of the insulation.

In hot climates like the southern U.S. for example, vapor barrier should be installed on the outside of the insulation, especially where there's air-conditioning involved to prevent condensation and mold.

In both cases, the vapor barrier is tasked with preventing warm, humid air from shedding its moisture as it meets a cool surface, no matter which direction it is travelling.

The most important thing to realize is that there is no fixed rule regarding vapor barriers. Building practices should always be determined by the climate in which you are building.

Vapor barriers

The rule for vapor barrier installation in cold climates is to have it on the interior with at least 2/3rds of your insulation on the outside of the vapour barrier. Air barriers on the other hand can come in the form of house wrap (WRBs), tightly sealed sheathing, insulation that slows airflow, and well-sealed gypsum board (drywall).

To explain this further, Gypsum board (drywall) is vapor permeable, but stops air flow. This means water vapor can diffuse through it, but air cannot pass through it.

If you think of how a polyethylene vapor barrier is installed, it will be cut, stapled and taped, then have nails and screws put through it to install strapping and drywall, along with breaches due to electrical wires and boxes. In most cases, the vapor barrier will be perforated thousands of times during the building process.

But a perforated vapor barrier would actually not be a problem if you have a tight air seal. Like that gypsum board box, the amount of water vapor that can pass through a ripped and torn vapor barrier is insignificant as long as the air seal is intact.