Insulation: blown vs. batt

[wifehatescar]

Did a search, hopefully this wasn't covered already...

I was at HD last night, they have blow in insulation for $0.19/sqft (to 6" deep/R19) and the R19 batts are $0.45/sqft. I might be missing something, but why would you get batts when you could save 60% and get the blow in? Does it have to do with having a vapor barrier? My garage is 3 car attached, unisulated but drywalled and painted with an A frame attic above, plenty of ridge and soffit vents. Could I just use 6-9" blown in the ceiling of the garage ($100-200 roughly) and be done?

PS-I'm looking at this for my garage ceiling, and for my house too which currently has R30 batting (I would blow over the R30).

 

[JCByrd24]

Not sure why its that much cheaper and but you do need a vapor barrier under normal conditions. In a garage thats already drywalled I'd be tempted to skip the vapor barrior. I'll be using the blow in stuff in my ceilings as well when I finish the upstairs of my cape because of the price difference. I'll add a vapor barrior to the warm side (under collar ties/ceiling joists) before drywall. If you want to do it properly you'd cut strips of vapor barrier and put them down between trusses before insulating but you'll still have gaps. As I said, in a garage(and at an attic surface with plenty of ventilation) I may skip it because the moisture won't condense and collect it will escape and evaporate. Much different than getting trapped in your walls. I think the whole completely sealed vapor barrior thing is going away because of mold issues...I'm of the "a little bit of breathing is always good" mentality.

 

[wifehatescar]

Yeah, I guess I'm wondering in my case where the attic space has a ton of ventilation, and the drywall celing in the garage is painted (with exterior paint), is a vapor barrier even needed?

 

[Dave Carney]

You don't need a vapor barrier with blown cellulose. I used it on the attached garage and will do the new detached soon. It's definitely the way to go in my opinion.

 

[Itzkwik]

Quick question when using blown in. I have seen the styrofoam trays that you staple up between the trusses/rafters to keep ventilation between the soffit vents and ridge vents. But what do you use to keep the blown in from clogging up the soffits?

 

[comquat1]

Quick question when using blown in. I have seen the styrofoam trays that you staple up between the trusses/rafters to keep ventilation between the soffit vents and ridge vents. But what do you use to keep the blown in from clogging up the soffits?

You just make sure that you don't blow it into them. they should extend higher than the depth of your insulation.

 

[DIGGER_DAVE]

My father-in-law operated an insulation company.
He specialized in "blown insulation."
He indicated that blown insulation is usually used with EXISTING enclosed spaces.

But to reach the same consistancy as "Batt Insulation" (and reach the same R value) it would usually take twice the amount. Depending on the accessability of the spaces to be insulated it could sometimes take THREE times the amount.

Depending on the operator of the "gun"; the blown insulation could settle over time and lose some of it's R value. (it DOES settle slightly after being put in place)

Shady insulation contractors some times will "shower" the insulation. (too much air and "lofting" the insulation in the air rather than spraying it into place)

If the gun opperator uses TOO much air and "lofts" when blowing the insulation in place, what looks like 6" deep immediatly after the job is done; can settle to less than 3".

It also requires some specialized equipment. (NOT readily available for rental) Did the blown insulation cost INCLUDE installation? There is usually a charge.

 

[NHCharger]

Quick question when using blown in. I have seen the styrofoam trays that you staple up between the trusses/rafters to keep ventilation between the soffit vents and ridge vents. But what do you use to keep the blown in from clogging up the soffits?

When we build houses that have the blown-in the insulators will take a piece of fiberglass insulation and stuff it between the top plate and the proper vents (styrofoam trays) so no blown-in gets down into the soffit area.

 

[wifehatescar]

But to reach the same consistancy as "Batt Insulation" (and reach the same R value) it would usually take twice the amount. Depending on the accessability of the spaces to be insulated it could sometimes take THREE times the amount.

It also requires some specialized equipment. (NOT readily available for rental) Did the blown insulation cost INCLUDE installation? There is usually a charge.

Thanks for the info!
HD let's you rent a blower for free for a day if you buy 20 bags, pretty good deal.
Also, according to the blow in insulation package, it is close to fiberglass once settled, inch vs inch.

I was mainly just wondering about the vapor barrier thing. If the R value is not quite right big deal. I just don't want mold or anything.

 

[Dave Carney]

r for r blown cellulose always costs a lot less. It's also a very simple diy project with the free blower from the big box stores. You don't get scammed that way.

 

[74-77Camaro]

Quick question when using blown in. I have seen the styrofoam trays that you staple up between the trusses/rafters to keep ventilation between the soffit vents and ridge vents. But what do you use to keep the blown in from clogging up the soffits?

One problem that most people don't think of with the styrofoam trays - They greatly reduce the Net Free Area (NFA) of your soffit vents. You are supposed to have the same amount of NFA at your soffits as you do at the peak vents. A 16x8 soffit vent averages 65 square inches of NFA. If you read the styrofoam trays fine print, it's NFA is 18 square inches, usually. So you cut the vents capacity by two thirds using them. Granted, that is better than being totally blocked, but the 'balance' of top and bottom NFA is screwed up using them.

In Texas, the AC bills are sky high, and I'm doing everything I can this winter to fix my attic venting and insulation this winter.

 

[jerry j]

If there is enough VENTILATION above the insulation - No vapor barrier is needed - . Make sure there are enough 'roof vents' (the cans you see up near the ridge) they release heat through convection. How many homes do not have a soffit area for ventilation ? Yup soffit (low) and roof (high) is an ideal set-up..

I don't like the styrofoam pieces between the roof joists because of what was mentioned earlier. -They restrict air flow too much. We use sheets of cardboard stapled to the roof joists at each soffit vent. This gives maximum air flow from that vent.

What causes moisture to condense is that warm air carries the humidity and when it hits a cold surface it turns to water...- example-- A cold glass of soda, Iced tea, etc. in the summer outside. When the warm moist air hits the glass it is wet. Leaves water on table when ya set it down.

Don't worry about humidity unless the inside of the area is generating A LOT of it.....
Good luck. Jerry (Insulation contractor - 30 yrs.)

 

[Donzi4me]

I got R30 batts at Lowes for .46 a sq. ft. It was easy put it in the ceiling. I do have blown in insulation in the attic of my house. I recently added to it, but it was a two man job. Me in the attic and the wife loading the hopper.

 

[jhchoppers]

What happens to the R factor when you put plywood or OSB down for storage in the attic? Is it better to use 3 1/2 batts on the places where you plan to put OSB or plywood down?

I was planning on using 3 1/2 under to the attic floor and 6 everywhere else. Any thoughts on this?

 

[PAToyota]

Compressing the insulation does lower the R-value. How deep are your ceiling joists?

 

[jhchoppers]

Compressing the insulation does lower the R-value. How deep are your ceiling joists?

2 x 4 Joist, so 3 1/5 in. Are you better off to go with 3 1/5 in batts than smashing down the blown in stuff, at least under the OSB ?

 

[jerry j]

2 x 4 Joist, so 3 1/5 in. Are you better off to go with 3 1/5 in batts than smashing down the blown in stuff, at least under the OSB ?

Just put the flooring down, secured w nails, and blow under it...FILL ER UP..

R U talking abt. your garage or home..??
If it's over any living space, I would try and store -somewhere else- and blow enough in the attic for a GOOD R-Value... When there is a floor in the home attic that you may use for storage, it will actually cost $$ to store stuff because you are limited to the amount of insulation you can put up there.. Even if the floored storage area is not that large...
If it's in the garage, not to worry too much.. Yup, try not to compress insulation, it does lose R-Value...

Jerry

 

[Pops]

I have chosen blown in, but it will have to be done in stages as I put in the ceiling. Just not enough head room to crawl arount up there! So we are going to put about 1/3rd of the ceiling in, blow in insulation, do the next, etc.

J.

 

[trainer]

I just got done doing the blown stuff in my new garage tonight.
My 28x28 garage took a bit over an hour to complete. I had a friend filling the hopper on the blower and I went up and worked the hose. We put in 12" of fiberglass equalling r-32. I've done batts in an attic before
and this was certainly easier and faster. The ceiling is drywall and I put in vapour barrier when i drywalled.

 

[jwith68]

jhchoppers, I did the same thing you're talking about when I insulated my 30' x 60' garage/shop. The trusses are built for storage, with an 8' wide open area down the middle. They are on 4' centers (metal roof and ceiling) so I needed to block in between them with 2x4's for support of the storage floor. The truss bottom chords are 2x6, but I used 2x4 blocking so there would be some clearance for wiring, etc. This blocking was at each edge and in the middle of the floor, creating 4' x 4' squares that would have been very difficult to be sure of filling with blown-in insulation.

To fill these, I used unfaced R-19 batts. I just cut each one in half, and one batt perfectly filled one 4' x 4' square. Then 3/4" OSB went down for a floor. I did take one extra (probably unnecessary) step by using 1/4" OSB to make a 6" high "fence" at the sides of the storage floor, between the trusses. This kept the ~10 - 11" inches of blown-in fiberglass (~R-30) that went into the rest of the attic space from spilling over onto the storage floor.

It took about 1.5 hours to lay in the batts, and about 3 hours to blow in the rest of the 22' x 60' area, with me in the attic, and my wife's 16yo cousin feeding the hopper. It was easy with the storage floor already in place, and he didn't have to work too hard either. The building is super easy to heat and cool with attic insulated this way, and R-19 kraft-faced in the walls.

 

[Kevin54]

HD let's you rent a blower for free for a day if you buy 20 bags, pretty good deal.

Once you get done messing with the blower because it doesn't work right, messing with the blow in insulation dust, the mess in the garage, etc.you'll wish you used the batts instead. The wife and I did my 28' x 36' garage with R32 batts in less than 2 hours. Doing the house with blow in took around 5 hours not counting the few hours it took to clean the dust off of everything. Besides that, if you ever have to add any light boxes or such, it is way easier to remove a batt than to scoop away blow in. Also, check the blow in insulation in a few years. It will need to be done again after it all settles.