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R value insulation question

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Forum topic by Holbs posted 326 days ago 595 views 0 times favorited 8 replies Add to Favorites Watch
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Holbs

511 posts in 631 days


326 days ago

I have 70% of my 2car garage ceiling rafters fitted with R-19 paper-faced batts with the goal of being 100% installed and fire rated gypsum panels to seal it all up with 2 2’x2’ access for future endeavors. Here in Reno, NV it gets to the 32degree range for a week or two, then stays in the high 40’s rest of season (winter season) . Ill have my Reznor gas heater installed as well for heating. As of yet, no insulation in the walls (will try to do blown-in before winter depending on wallet size). My question is… since I still have access, would it be worth while to throw up an additional layer of R-12 (or even R-19) unfaced batts, for a total of… R-31 / R-38 in the ceiling? Is there a financial difference between energy bills / heat loss from R-19 to R-30’s?
I only have 2×4 studs for walls so I think max R value of walls with blown-in celluse (no, i will not be shelling out the $$$ for spray foam insulation) will be in the R-12 range.


8 replies so far

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firefighterontheside

3319 posts in 459 days


#1 posted 326 days ago

I think the biggest insulation from fiberglass batts for 2*4 is r-13. I think you will hit a point of diminishing returns in the ceiling. I would be surprised if adding to the ceiling to have r38 would be cost effective. I bet the code in your area only calls for r30 or less in your area. I think its all relative. I’ve gone several years with no insulation. This year I put r11 in the walls and r13 in the ceiling. I will perfectly happy with that. I could make it OK in there with no ins. and two space heaters. I’m thinking I can get it even warmer in there this winter and use half the energy. That’s my opinion anyway.

-- Bill M. I love my job as a firefighter, but nothing gives me the satisfaction of running my hand over a project that I have built and just finished sanding.

View Shawn Masterson's profile

Shawn Masterson

1243 posts in 550 days


#2 posted 326 days ago

normal for 2×4 walls in r-11/r-13, they have an r-15 but its not common. in your area I would think you would be more concerned about keeping the heat out in the summer. I would finish the r-19 and at a later time when budget allows blow another foot of cellulose in the ceiling. There is no such thing as too much insulation, as long as you still have proper ventilation. I have 3 1/2 feet of blown fiberglass in my addition and 18 inches in the house. when I finish redoing my upstairs bath (I am raising the ceiling) I will top it off to 3 feet give or take. As I gut each room 1 at a time I am insulating and sealing all the walls.

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fussy

980 posts in 1653 days


#3 posted 326 days ago

In Green Bay, Wisc., yes. In Reno, no. Cost effective it won’t be.

Note to Bill M.: I know you don’t need to be told this, but it’s on my mind. Beware of flashovers. We have a local VETERAN volunteer firefighter with 90% body burns. He charged, unequipped into an unoccupied house a few doors from his house and was caught inside when it flashed. The next responder, also unequipped, pulled him out and received extensive upper body burns, but was released in a couple days. Be careful.

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

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Holbs

511 posts in 631 days


#4 posted 326 days ago

ooo.. i like that answer, shawn. yes..that sounds like a more sound economical plan. i’ll run with the R-19 for ceiling for this winter and finish it off. if i feel it needs upgraded, and since i will plan on minimum of 2 access holes (maybe even 3), i can blow in more during spring.

bill & steve: you both might be right on ‘diminishing’ returns going above R-19 for a 2car garage wood shop setting. i’ll have to see how the R19 holds up by itself this winter.

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Holbs

511 posts in 631 days


#5 posted 326 days ago

shawn… are you doing the LJ sister site with your upstairs bath project? home remodeling site?

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Grandpa

3048 posts in 1277 days


#6 posted 326 days ago

I inspect home and have taken classes on home insulation. I didn’t check on where Shawn lives, but unless it is in an extremely cold climate he is well into the point of diminishing returns. Be sure to cover your joists. Those do transfer hot and cold temps into the living area. In SW Oklahoma we run some days over 100 deg. in the summer and some in the teen temps in the winter. Those temps can swing even further than I mentioned but those pretty well bracket our range. Our max temps are 117-118 in the summer and minimums are in the 5-10 deg. range in the winter. They recommend 16 inches of blown fiberglass in our homes as a max and 9 inches as a minimum. That is for living spaces. Unless you spend a LOT of time in your shop area the diminishing returns are greater. It will save so much then you are to the point of not saving any more. 12 inches of added insulation would save very little more after you reach that point. Your scuttle holes to access the attic should have some of that fire rock as a cover. Plywood will burn and open a hole that drafts like a chimney. I would check and see how much it costs to blow in insulation. It is often cheaper to have it blown in the attic than to install batts. Blown insulations has not seams at the edges of the joists like batts.

With all this said I work in a metal shop that has about 2.5 inches of insulation stretched over the fram. then trapped by the metal sheets. This is compressed tightly where it crosses the purlins. I added a room on the end that is 20×30 with no insulation. It is very noticeable when you go in that room. The heat is awful. The insulated side is much cooler.

View Shawn Masterson's profile

Shawn Masterson

1243 posts in 550 days


#7 posted 326 days ago

Holbs- No I haven’t checked out the other site

As for location, I live in South Bend Indiana I am in the lake effect belt. I get the edge of the laporte band and the edge of the southern michigan band. I have seen as much as 4’ of snow in less than 5 days. We have 90 with 75% humidity in the summer and as low as -25 windchill in the winter, now that’s the extreme but not unheard of. I know people who have had gas bills over $500 a month in the winter. Thats why I see it as you can’t have too much of a good thing.

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firefighterontheside

3319 posts in 459 days


#8 posted 326 days ago

Steve, thanks for your concern. We buy the best turnouts we can get. With the new building materials these days a flash over can reach 1800 degrees at the ceiling. Our gear is designed to protect us one time in that situation. We would still get some burns in weaker areas such as ears, wrists and neck. We are trained extensively on recognizing the conditions leading up to flash over. I’ve been doing this for 21 years and hope to retire from it it in less than 10. My name, firefighterontheside, reflects that I’d rather be doing woodworking fulltime and firefighting on the side. Maybe someday.

-- Bill M. I love my job as a firefighter, but nothing gives me the satisfaction of running my hand over a project that I have built and just finished sanding.

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