OT: - Insulation - Batts vs blown in | The Boneyard

OT: Insulation - Batts vs blown in

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temery

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I'm insulating my attic and garage. The garage will be finished (drywall).

What are the pros and cons of each method?
 
This summer I removed the batts in my attic and had foam blown in. It was cooler on the 2nd floor and now that’s it’s cold outside, the furnace is not cycling on as often, I recommend the foam.
 
Blown foam is the best but also the most expensive. Fiberglass is the cheapest batt but you are limited in r value based on stud width. I went with the batt but I used roxul , Which is rockwool. It is more fire retardant, better sound dampening and better r value than fiberglass but cheaper than blown foam.
 
Closed cell spray foam really reduces drafts, improves structural integrity and has the best R-Value. However, I think you stated your house is very small. If so, calculate if you will reap the benefits of foam. In building, things tend to get cheaper as the house gets bigger. Meaning, if your house is 800 sq ft, you’ll often pay much more per square foot for insulation and other materials than the guy with 4000 square feet. Be sure to find a good price per square foot and avoid/minimize any sort of “minimum” charge or a charge for showing up with the truck.

Foam is unquestionably better, but make sure it is worth it. Also, be sure all your roofing and plywood decking are in good shape and won’t need replacing any time soon so that the insulation job doesn’t have to be disturbed for years.
 
Also, I am assuming you mean rigid spray foam and not the loose kind that is more like foam packing peanuts?
 
temery said:
I'm insulating my attic and garage. The garage will be finished (drywall).

What are the pros and cons of each method?
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You can put the batts in the bays R-38 or more if space permits. Blown in fiberglass fills all voids and gives more R value. Foam blown in is another option, do your home work on off gases etc.
 
I'm considering having spray foam put in my attick walls and ceiling. Supposedly keeps temp in attic within 10 degrees of the second floor both summer and winter, thereby keeping the heat and a/c bills low. Was big thing on This Old House once.

Anyone have any experience with that? Closed or open cell foam?
 
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You can get additional R value with multiple R19 unfaced bats. You criss cross each layers to fill in voids. Did 3 layers R19 (R57 effectively) on my place way up in northeast kingdom vt. Works very well
 
Hankster said:
LOL, man I just noticed that. Not thinking. Can I delete that? LOLL. then I read the next sentence. Man did I step into that one.
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Are you kidding? that was pure gold. Can't delete that stuff
 
temery said:
I'm insulating my attic and garage. The garage will be finished (drywall).

What are the pros and cons of each method?
Expand ...

Do you care about cost? Batts are cheap and easy. But sprayed is almost always going to be superior.

Is your garage under a part of the house? Do you keep it room temp? If it's aside of your house with no heating, and you want to keep it a bit insulated, just throw batts in the that and spray the attic.
 
Cost v. efficiency

For the garage...are you insulating the walls and ceiling? Is the garage under the house/adjacent/stand alone? Is the garage heated or are you just trying to minimize heat loss in the attached house?

For the attic, you must consider how it is currently vented. You don't want moisture in the attic, so typically you have a ridge vent or gable vent. So the theory is insulate the floor or the attic/ceiling of the house...the attic gets hot or cold, but not the house because of the insulation. If you are using spray foam on your attic they normally spray the roof joists, you are using that as conditioned space and need to be sure there is no other venting in the attic, otherwise you are insulating nothing.

We just did what someone else suggested in the attic, we used 2 layers of batts.....it wasn't worth the extra cost of the foam and closing the vents..
 
temery said:
I'm insulating my attic and garage. The garage will be finished (drywall).

What are the pros and cons of each method?
Expand ...

Sounds as if you're asking about batts versus blown in fiberglass. If that's the case, blown in fiberglass will fill all voids and you can vary its depth according to the size of the floor joists (if they're different sizes in different parts of your attic) and, if you so desire, you can easily overfill so the insulation is deeper than the joists and at even depth across the attic. Just don't overfill so much you block the air flow from your soffit vents.

The walls are another story. To blow in fiberglass into the wall voids you have to have an opening in every bay of the wall studs and after the insulation is blown in those openings will have to be patched. It's also not easy to blow in fiberglass into the walls because there are firestops in every bay and wiring in probably most of them so the distribution may not be even. If you're focused on fiberglass, batts make more sense for the walls because you can cut the batts and fit them around any obstructions before you do the sheetrock.

If you're talking spray foam rather than blown in fiberglass, it's done differently. You don't spray foam between the floor joists of the attic, you spray it into the spaces between the roof rafters. This encapsulates the attic space and keeps the attic temperature within 5 to 10 degrees of the house.

We added garage space to our house in South Carolina and I decided to use foam for the new area as well as the existing garage walls and, after soliciting bids from three companies for that work PLUS the attic of the main house, I checked references and went with the low bidder. A contractor I know used them all the time and gave them high marks. It's a big attic and with the spray foam between the rafters on 90+ degree days in the summer it gets no warmer than the low 80's whereas when we had fiberglass batts in the floor joists it was well over100 degrees. Can't remember (it was 7 years ago) but I seem to recall it was over 110 degrees on very hot days before the foam. In the winter the attic is close to the same temperature as the house because the heat rises through the sheetrock ceiling as well as all the voids for recessed light fixtures, etc.
Great place to use as work space if you have enough ceiling height.
 
Greenback said:
Blown foam is the best but also the most expensive. Fiberglass is the cheapest batt but you are limited in r value based on stud width. I went with the batt but I used roxul , Which is rockwool. It is more fire retardant, better sound dampening and better r value than fiberglass but cheaper than blown foam.
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For the attic, at least, you can overcome the stud width limitation for batts by stacking a second layer on top of the first. From what I gather, when people do this they lay the second layer of batts perpendicular to the first (covering both the first layer of batts and the studs).

And the 2nd layer can't have a vapor layer like the original layer does. Has to have no barriers on either side.

I suppose there are possible complications if you have, for instance, soffit vents in the attic. Might need to install some extra hardware to make sure the airflow of those vents rises clear over the layers of insulation.

edit: Whoops, tomtom80 already said all of this. Oh well, I'll leave my message here to be a monument to my lack of paying attention. :cool:
 
temery said:
I'm insulating my attic and garage. The garage will be finished (drywall).

What are the pros and cons of each method?
Expand ...

My sons have owned a blown-in insulation business for about ten years, just asked them you question via text, here's what they responded.

Batt insulation is cheaper but does not do as good a job as spray. Because spray is better you HVAC mechanics run less often and more efficiently/cheaper and will last longer. Multiple studies on new construction show that spray results in 30-40% savings on heating and cooling.
 
huskiesouth said:
My sons have owned a blown-in insulation business for about ten years, just asked them you question via text, here's what they responded.

Batt insulation is cheaper but does not do as good a job as spray. Because spray is better you HVAC mechanics run less often and more efficiently/cheaper and will last longer. Multiple studies on new construction show that spray results in 30-40% savings on heating and cooling.
Expand ...

One concern I have with blown in insulation is settling over time.
 

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