R38 vs R49 Ceiling Insulation - Southern Michigan

[zc15]

Looking at insulating a detached garage in preparation for a 45k Hot Dawg in Southern Michigan where daily temps in Jan Feb March are 26, 28, 37 degrees F respectively.

The price of blown cellulose material has increased lately, so now it is pretty much the same to do R49 blown cellulose as it is to do R38 fiberglass batts. Batts may actually come out cheaper due to equipment rental and not needing material to block off the eaves for ventilation


Right now I am leaning towards the batts since I don't think I am completely done running wires or making changes to the ceiling that I will be installing.

I think the flexibility of being able to remove and reinstall, plus the added ease of installation make batts the choice for me. I am not concerned about the 0.6% loss in efficiency between the two (but should I be?).


Should I be ok with the R38?

 

[jack stand]

It's a tough call, at those levels the "line" is pretty flat. (Gain or additional insulation value)
Going with the r38 batts that I observe to be tighter and have a hard time believing equal to equal depth of blown in (completely non scientific) , you can always come back in and add whatever you'd like, whenever you like.

 

[zc15]

It's a tough call, at those levels the "line" is pretty flat. (Gain or additional insulation value)
Going with the r38 batts that I observe to be tighter and have a hard time believing equal to equal depth of blown in (completely non scientific) , you can always come back in and add whatever you'd like, whenever you like.

Depth of insulation is not a concern. There is plenty of space for either

 

[jack stand]

I understand, you seemed to be wrestling between the choices favoring the batts advantages but wanting the depth of the blow in. I mostly was speaking of the slightest deference in performance (depth) coupled with your perceived batt preference and recommended that you just go with the f/g r 38 batts and if after a winter, you feel the need for additional insulation, blow 6" on top.

 

[zc15]

I understand, you seemed to be wrestling between the choices favoring the batts advantages but wanting the depth of the blow in. I mostly was speaking of the slightest deference in performance (depth) coupled with your perceived batt preference and recommended that you just go with the f/g r 38 batts and if after a winter, you feel the need for additional insulation, blow 6" on top.

Thanks. I was originally considering blown-in because it was less expensive and I didn't realize how little performance increase the 49 holds over 38.

 

[Showkey]

I just added 55 bags of blown in insulation in 1000sqft garage space and touch up 1000sqft home attic space. Total cost was $661 -11%.

I would recheck the math…….
1000 sqft R49 blown in cellulose $858 plus $50 blower rental
1000 sqft R38 fiberglass batt $803

R a value % change and % difference is significant.
Then add Nat Gas and propane are increasing ?

 

[86turbodsl]

You're not capturing the law of diminishing returns on insulation.

 

[zc15]

You're not capturing the law of diminishing returns on insulation.

Right, that has really justified the switch in my mind

I've decided on R38 batts.

Now I have to think of a way to build up the ceiling joists so I can keep the sheet of plywood in the attic to store the golf clubs. Right now I'm leaning towards using strapping to secure another board on edge to give the insulation enough room

 

[Showkey]

You're not capturing the law of diminishing returns on insulation.

A ton of discussion on the insulation diminishing returns with 100‘s of articles and opinions on every building forum and in magazines.………..depending on location most of the diminishing returns discussions start at R49 to R60.

Many locations R38 is the code minimums for ceilings.

Truss/rafter storage insulation solution is often solved by adding 2 by 6-8“ added to the bottom cord then the insulation then the plywood floor is set 6-8” higher.

 

[86turbodsl]

A ton of discussion on the insulation diminishing returns with 100‘s of articles and opinions on every building forum and in magazines.………..depending on location most of the diminishing returns discussions start at R49 to R60.

Many locations R38 is the code minimums for ceilings.

Truss/rafter storage insulation solution is often solved by adding 2 by 6-8“ added to the bottom cord then the insulation then the plywood floor is set 6-8” higher.

Sure, all i'm saying is that going from R38 to R49 costs a fair bit and returns not that much.