Adding Attic Insulation With Poor Vapour Barrier

[Industrial Toys]

I need to insulate my attic. It's long, long overdue. I wished I could have used blown rock wool which I am told is not available anymore. So I will probably go with blown cellulous. The light fluffy one, not the shredded (dusty) newspaper kind.

The original glass bats were of the tar paper lined variety, so not a great vapour barrier.

Is this going to be an issue?

Oh, I should add. This is in a Northern climate, half year heating season.

Thanks in advance.

 

[bigtiller]

I don't think a vapor barrier is necessary in the ceiling. The walls need one, but if there is one in the ceiling, how will the moisture get out?

My house was built in '98 without one in the ceiling and with blown in fiberglass insulation.

 

[teejk]

I don't think a vapor barrier is necessary in the ceiling. The walls need one, but if there is one in the ceiling, how will the moisture get out?

My house was built in '98 without one in the ceiling and with blown in fiberglass insulation.

That vapor barrier debate seems to be one that will go on forever (kinda like whether coffee is good or bad). Actually not sure which side is winning right now.

 

[jack707]

Coffee and tea are good for you.

 

[Larry Caldwell]

A coat of paint will provide a good vapor barrier if it has a membrane surface, like semi-gloss or eggshell. Flat latex is a lousy vapor barrier. You can also buy vapor barrier paint that is specifically formulated for that purpose. All major paint manufacturers offer vapor barrier paint. You may have to go to a paint store rather than Home Depot to find it.

 

[Qapla]

Have you considered having icynene sprayed in/on?

 

[EddieWalker]

The vapor barrier on the walls of a house is more for wind then anything else. Cold air gets through the siding and pretty much makes cancels out any benefit from the insulation. Since heat and cold go up and down, not sideways, wind is your biggest concern with a vapor barrier.

For attic spaces, gaining the desired R rating is all that matters. You will find ceiling bats with a vapor barrier on one side, all four sides and not on it at all. I think that's more for installation then any measurable improvement to heating and cooling a house. I personally like Attic Cat a lot for blowing in insulation. There is no need for a mask, it's super easy to load the machine, it never clogs up and it's easy enough to have just about anybody help you keeping it loaded while you handle the hose.

Home Depot gives you the machine to use for free when you buy ten bags of insulation. Each bag is a lot more then the other brands, but when you figure out the math comparing coverage, it's all pretty much the same. Here in Texas, heat is our main concern, but it does get down into the teens in the winter and we can go all week and never get above 30. We also get snow here, but not very much and it never lasts very long. Our standard is now R60, which is just under 2 feet thick.

When I did my parents house, it was brand new and it took me close to 6 hours to do 3,000 sq ft. That's a long time to be in an attic, but I was never bothered by the insulation, just tough on your back, feet, ankles and legs walking around on rafters that long. Most houses that I do, it's usually about 3 to 4 hours since they already have some insulation in there.

 

[teejk]

The vapor barrier on the walls of a house is more for wind then anything else. Cold air gets through the siding and pretty much makes cancels out any benefit from the insulation. Since heat and cold go up and down, not sideways, wind is your biggest concern with a vapor barrier.

For attic spaces, gaining the desired R rating is all that matters. You will find ceiling bats with a vapor barrier on one side, all four sides and not on it at all. I think that's more for installation then any measurable improvement to heating and cooling a house. I personally like Attic Cat a lot for blowing in insulation. There is no need for a mask, it's super easy to load the machine, it never clogs up and it's easy enough to have just about anybody help you keeping it loaded while you handle the hose.

Home Depot gives you the machine to use for free when you buy ten bags of insulation. Each bag is a lot more then the other brands, but when you figure out the math comparing coverage, it's all pretty much the same. Here in Texas, heat is our main concern, but it does get down into the teens in the winter and we can go all week and never get above 30. We also get snow here, but not very much and it never lasts very long. Our standard is now R60, which is just under 2 feet thick.

When I did my parents house, it was brand new and it took me close to 6 hours to do 3,000 sq ft. That's a long time to be in an attic, but I was never bothered by the insulation, just tough on your back, feet, ankles and legs walking around on rafters that long. Most houses that I do, it's usually about 3 to 4 hours since they already have some insulation in there.

I think the debate comes in with "too tight" houses (I think they call it "sick house syndrome"). My shop has a metal ceiling and there it was necessary to have the vapor barrier to prevent rusting from above. Other than that I don't really know where the debate stands right now. Btw, on the shop people forgot to put in the "stops" on the eave edges that are an integral part of the air flow (eaves to ridge vent). We banked it up with 2 layers of thick batts...got to R50 with special order stuff and filled in the field with blown in. Was 30x40 and I think I paid the guy $1,000. Trusses are 8' OC (with 2x4 nailers). That's a little more gymnastics for this old body.

 

[Industrial Toys]

Thanks.

Yes. I have spent too much time in attics, being in the security bus. Rich people have bigger attics these days then the size of my house. They arn't too bad, except you don't want to compress their insulation, and always get insulation on their fancy clothes which is where the attic hatch usually seems to be.

I just envisioned the moist warm air migrating up through my meager fiberglass bats and condensing in the new layer of blown in insulation. I know the old fiberglass pink is useless when wet.

 

[topbuilder]

I need to insulate my attic. It's long, long overdue.

I have never used vapor barriers used in attics. But, this is Texas.
The blown is good. It will make a dusty mess into a completed home. They usually have a minimum charge, for our area it's $500. I recently did a remodel where I had to tear out about a bunch of ceiling. So that had to be insulated and I had some some R13 batts over a previous room addition that needed to be brought to R30 +. My scheduled blow guy did not make it by my deadline and I ended up laying r30 batts, no paper. $250 for insulation and a couple hours work. The think I don't like about the blow in is if there is any foot traffic afterwards, there goes your R value. Trapped air is what you are looking for.