Insulation 101 - What all do I need?

[gtivr4]

So half of my garage is insulated (the walls that are connected to the house), but it NEEDS more insulation, and a ceiling. So, I need a little assistance in insulation 101.

The walls are 2x6, 24" OC. What is the max R-value I can cram in there?

How much should I put in the ceiling? I am in Vermont, so its pretty cold, and I would rather do it right now. Should I be looking at blow in (its only 24x24) or batting?

Finally, other than adding a couple of outlets, should I look at doing anything else in the walls while they are easy to access? I'm thinking of adding some 2x between the studs at cabinet height for easy access to studs.

 

[4StarCstms]

You Don't want to Cram in the insulation, it starts to loose its RValue when you compress it. On a 2x6 Wall you can get R19.

As to the ceiling, you want the most you can get. R31 perhaps. So much of the heat loss goes out the roof (heat rises) As to the blow in VS roll...I guess it comes down to Cost VS hassle. I'd rather fight with the Roll insulation to save some $$$ but thats just me. I mowed down my money tree this summer...

 

[kb2tha]

I just purchased 18 bags of Attic cat fiberglass blown in at HD. Total came to about $500. Enough for an r 49 in my 26 x 28 area to be heated. After the energy credit that is available yet through the end of the year it will cost me a net of $350. I do not consider this extreme for r 49 in a ceiling.

As for the walls.......a closed cell spray foam will give an r of about 37 if you fill the entire cavity. This would be pricey though. I priced close cell at .85 per sf per inch. Therefore a 5-1/2" wall cavity would equate to about $4.68 per sf. I went with the open cell at 3" and 1" urethane rigid insulation at r 7.

Ken

 

[ishiboo]

So half of my garage is insulated (the walls that are connected to the house), but it NEEDS more insulation, and a ceiling. So, I need a little assistance in insulation 101.

The walls are 2x6, 24" OC. What is the max R-value I can cram in there?

How much should I put in the ceiling? I am in Vermont, so its pretty cold, and I would rather do it right now. Should I be looking at blow in (its only 24x24) or batting?

Finally, other than adding a couple of outlets, should I look at doing anything else in the walls while they are easy to access? I'm thinking of adding some 2x between the studs at cabinet height for easy access to studs.

2x6 cavity goes to R-21, I use R-19 as I paid $5.39 a roll for 250 rolls Fiberglass insulation should always be used at its rated thickness, if you compress it you loose substantial r-value as the air space is what insulation is.

You can go higher than 21 by going with foam/etc., but its substantially more expensive.

I'd do R-40 minimum in the ceiling, blown in is fine.

 

[Steevo]

I used R21 fiberglass batts to insulate my 2x6 exterior walls. That is the highest r-value I believe you can get in a 6" wall using "conventional" insulation.

 

[RM209]

Lots of differing recommendations for R-values. I'd suggest you begin by looking at what the US government recommends: http://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table
Since you're in region 6, the gov't recommends R49 to 60. Not sure if their recommendations are practical for you, but at least you can see the direction the builders and renovators are moving.

Whenever you insulate, you should also calculate and increase (if necessary) the amount of ventilation in your attic to avoid potential problems with condensation.

As stated, if you make a purchase before 12/31, you can (potentially) receive a healthy tax credit.

Good luck,
RM209

 

[csp]

Government recommendations for R-values are for living space.

Unless you live or work in your garage with the heat on 24/7 there's no need to follow "recommended" R-values, IMO.

 

[gtivr4]

Government recommendations for R-values are for living space.

Unless you live or work in your garage with the heat on 24/7 there's no need to follow "recommended" R-values, IMO.

So what would you recommend for a garage to keep it moderately warm to work in (heatable, not heated), keep the cars warmer, and most important to help keep the inside of the house a bit warmer.

I assume its more important to invest in ceiling than walls...

 

[ishiboo]

So what would you recommend for a garage to keep it moderately warm to work in (heatable, not heated), keep the cars warmer, and most important to help keep the inside of the house a bit warmer.

I assume its more important to invest in ceiling than walls...

I'd do the standard anyway, at least 19 in the walls and 48+ in the ceiling as recommended. Anything you skimp on insulation is going to cost you in heating bills, and the difference between a couple R values when installing insulation is not worth half-assing it to "save".

IMHO.

 

[Jaguar Fan]

I've been told that the R-value of the 2x6 is at best about R3 (although perhaps this refers to a 2x4 stud).

After insulation, with 24" OC studs, if you use a thermal camera to take a picture of the wall, you would see nice insulated areas about 22-23" wide, then a vertical stripe of R3 virtually uninsulated stud (~2"). It would look like stripes every 24". That part hurts.

It is possible, but probably not worth it in a garage, to add a sill plate with studs staggered, rock it, fill the entire cavity with blown cellulose, and it will be toasty because nowhere would you then have the R3 of a single stud connecting house to garage (or outdoors to garage).

 

[jklingel]

Whatever you chose, do not chose fiberglass batts. As noted, you see lots of heat loss at the studs, either because the studs themselves have a minimal R value, and because the batts will never seal tight. Plus, the R value of fiberglass drops with the temp. Either spend the time and dense pack w/ cellulose, or use cotton, mineral wool, or cellulose batts. Worry more about air sealing, though, than what insulation you use. Read on buildingscience.com about air sealing.

 

[snorky18]

It is possible, but probably not worth it in a garage, to add a sill plate with studs staggered, rock it, fill the entire cavity with blown cellulose, and it will be toasty because nowhere would you then have the R3 of a single stud connecting house to garage (or outdoors to garage).

I would think this would also significantly reduce noise and vibration transmissions through the wall as well, which might be worth it in an attached garage where you're doing noisy work on one side of the wall, and living space is on the other.

 

[jklingel]

Double 2x4 walls w/ dense packed cellulose (3.5 lbs/cubic ft) is certainly an option, and is commonly done. Spread the walls as wide as you want to. It is all about the numbers. If you want to get serious, run a heat loss analysis (builditsolar.com has an online calculator that is easy to use) and look at cost vs pay back time, etc. Yes, it will be quite inside, as cellulose is more dense than fiberglass, and you will have a wall that has zero gaps and minimal thermal bridging, ie, studs with lower R value that reduce the over-all wall's R value). Cellulose, treated w/ borates, also repels rodents and bugs and can buffer moisture leakage in the heating season. Etc. Buildingscience.com, greenbuildingadvisor.com have info on all this.