Siga and Rockwool . . . worth the $?

[newbie_garage_brutha]

Greetings Garage Journal Warriors!,

I have been a lurker for several years and finally bit the bullet on a smaller post frame structure at 30' x 44' x 14' - the maximum size that zoning would allow.

I know the insulation topic has been covered 300x's over, but I am asking the community for feedback regarding Siga products.

I want to go ahead and put Rockwool ComfortBoard 80 behind each post, Rockwool Comfort Batt R-23 in the walls, and blown-in R-38 in the ceiling.

My question is am I wasting money on Siga products (Majrex 200 and associated tapes), or just go with standard sheeting staples/tape?

Wall sheathing will be a mix of 3/4 ply and tin.

I am in Zone 5A.

The structure will be for year-round mixed use (storage, hang-out, garage, workshop) and plan on ceiling fans and a mini-split in the future.

I have been following RR Buildings specifically these videos:

As the structure currently sits:
WALL DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screwed down vertically) >>Dupont Tyvek >>horizontal 2x4 girts >>2X6 pressure treated syp ground contact skirt board (against concrete floor) >>2 x 6 x 20' laminated 3-ply columns (Green Post)

ROOF DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screw down) >>double-bubble vapor barrier >>scissor truss (8/12 pitch top; 4/12 pitch bottom.

VENTING:
12" roof overhang on all sides w/vented soffit.
44' of continuous low profile ridge vent.

FLOOR:
>>2X6 pressure treated syp ground contact skirt board >>5" 4K PSI fiber mesh reinforced. >>6 mil vapor barrier >> 4" crushed stone base . . . yes I regret not insulating the slab.

Thank you all in advance for your time/feedback!

 

[u2slow]

I used rockwool instead of fiberglass because it won't mold, and it's taking a long time before I can heat the shop.... I'm in a damp climate.

 

[mike93lx]

Kyle does good work, but all that stuff is sponsored. I can't imagine what that build would cost to hire out.

Rockwool is great, but damn, it's gotten expensive

 

[Rusty Wrench]

Rodents love to nest in fiberglass and as I'm told, rockwool also.
I had enough damage and odor that I had some batts replaced with blown in.
If I had to do it over again it would all be blown in cellulose.

Sounds like it's going to be a fantastic project

edit: something in the treatment is repellent to rodents.

 

[NUTTSGT]

Like mentioned, that was sponsored and to showcase what could be done with a post frame building to highlight his channel. If he didn't have 1.75M subscribers and a Youtube channel, he wouldn't have built his shop that way.

No doubt those guys do awesome work.


I've said it before, "Insulation is an investment." However, what is your return going to be for what you use it for ?

Have you done any pricing yet ?

 

[pembol]

In your house - absolutely! In a garage I am not so sure. I am all about building science and high performance construction, but I doubt a second order improvement like Siga will make much difference in what is likely to be a fairly leaky structure to begin with. Definitely price it our relative to something like spray foam that would move the air sealing to the outside of the wall.

Also, to pile on about all these sponsored 'influencer' shows on youtube. It used to be that we watched content interspersed with ads, now the content is the ad. It is kind of like instead of watching the football, with a Bud lite commercial every 10 minutes, in 'influencer world' the players would all be chugging bud lite on the field.

Rockwool and Siga both make great products, but I would take some dude paid by Rockwool and Sigas opinion about using Rockwool and Siga with a large grain of salt.

 

[Tundra1]

Funny, I saw your title and figured you likely were following rr building guidance. I guess those products have aligned with a great marketing method. Those guys are entertaining to watch and give good info. But the overwhelming sponsor push gets annoying.
Siga is hard to find in my area but I assume it's crazy expensive. Same with rockwool actually.

 

[NUTTSGT]

In your house - absolutely! In a garage I am not so sure. I am all about building science and high performance construction, but I doubt a second order improvement like Siga will make much difference in what is likely to be a fairly leaky structure to begin with. Definitely price it our relative to something like spray foam that would move the air sealing to the outside of the wall.

Also, to pile on about all these sponsored 'influencer' shows on youtube. It used to be that we watched content interspersed with ads, now the content is the ad. It is kind of like instead of watching the football, with a Bud lite commercial every 10 minutes, in 'influencer world' the players would all be chugging bud lite on the field.

Rockwool and Siga both make great products, but I would take some dude paid by Rockwool and Sigas opinion about using Rockwool and Siga with a large grain of salt.

Also keep in mind, Kyle used LP Smart Side for his outside wall sheathing. A way better product when it comes to air sealing an outside wall than screwed on metal panels.

 

[acer66]

Rodents love to nest in fiberglass and as I'm told, rockwool also.
I had enough damage and odor that I had some batts replaced with blown in.
If I had to do it over again it would all be blown in cellulose.

Sounds like it's going to be a fantastic project

edit: something in the treatment is repellent to rodents.

My personal experience with rockwool/mineral wool and rodents is that they do not like it.
Your results might differ though.

I had them stacked still wrapped in plastic for over a year in a shed.

The mice went between plastic wrapping but never inside the bales.

It also does not fall into pieces like fiber glass when water gets introduced which was also an involuntary experience of mine.

In a pinch you can also use it as fire protection when soldering in tight corners.

I take mineral wool over fiberglass any day.

 

[Stuart in MN]

The Siga product looks great, but I'd like to see an actual cost comparison to a regular old plastic vapor barrier. Having said that, you also have to look at the price over the lifetime of the building...maybe on a per year basis it's not that big a deal.
Something else Kyle stresses in his videos is sealing around the edges of doors and windows, around penetrations for wiring and plumbing, etc. to minimize air infiltration. That's probably the most important thing.

 

[acer66]

Something else Kyle stresses in his videos is sealing around the edges of doors and windows, around penetrations for wiring and plumbing, etc. to minimize air infiltration. That's probably the most important thing.

I think that cannot be stressed enough.

 

[loganb]

Interesting question....I'm in the residential building industry so familiar with the products.....

As mentioned....the materials are spendy. I've used Rockwool in my house though on interior walls for sound reduction and love the product, I've never priced it against conventional blown in or batt though to see if I thought the cost was worth the benefit. In Zone 5a....the thermal improvement is pretty marginal for as expensive of an upgrade as I think using their R23 comfort batt in place of conventional fiberglass. Unless some of the other benefits were of significant value to you, I might consider going for a cheaper batt product and use that savings towards getting HVAC in sooner. If you've got a dedicated area where you expect to do hotwork(welding etc) even with metal over the top that extra protection behind the wall there would personally give me some piece of mind on any sparks etc

Your typical post frame building is an air leakage mess, so the Majrex interior barrier does make sense to helping to manage the air. As it's pointed out above though, RR's sheathed the entire structure(walls and roof) with LP's sheathing with integrated weather barrier so his building shell is significantly improved from an air tightness(and more rigid) then just doing Tyvek over framing. The blower door test results were better than the vast majority of new construction single family builds at approx .5 ACH50 and after they get interior finishes done it'll get even better

The sheathing adds significant stiffness to the structure but also just gives a better substrate to then attach siding to and from what I see on most residential construction projects, the weather barrier on the sheathing (be it ZIP or LP) is generally done "more right" then most Tyvek/Typar or similar sheet type barriers. If you're building this yourself, hanging Tyvek even as a 2 man crew on a structure like your proposing, then going back and hanging metal siding....very slow and if you get wind....good luck. They talk about it in the RR episode on sheathing but the tyvek noise in the wind...yuck.

Getting at least 7/16" OSB sheathing under that Tyvek so it can be cap stapled properly will give a far better chance of success. You might consider pricing out the ZIP or LP integrated sheathing product and seeing what that increase would be though. Yes it'll be more money in material, but it is fewer trips around the structure. Be aware they do have as I recall a 6 or 12 month UV exposure warranty limit on that weather barrier coating on at least the ZIP material so you can't let there be years between sheathing and hanging metal on the outside.

I personally wouldn't bother with the Majrex on the interior unless I was doing "more" on the exterior as feels like the kid putting his finger in the hole on the dike...more holes just keep popping up. A case of flashing tape and couple cases of caulk and time to properly seal penetrations, sill plate joints etc I think will be cheaper and better payoff than the Siga tape

 

[ToolsRCool]

I'm doing my own home-brew hybrid of both. Because Rockwool is supposed to fend off rodents, yet is expensive, I am doing the upper and lower 1 foot of each wall cavity with Rockwool, and the rest in between with fiberglass batt. Will have paneling tight on the inside and out as a new build, as well as a poly vapor barrier on the inside (MI). I presume mice and such not to be able to easily get into the center point of a wall cavity, as long as I have outlets, switches and stuff sealed up tight. I would think they would try to get in at the top or bottom of any wall cavity. I plan to do the same with my rafter cavities.

 

[bluedog225]

From the first video. “I need, like, one of those push sticks.”

At those temps, he‘s not going to feel the saw taking his fingers.

 

[reader2580]

Also keep in mind, Kyle used LP Smart Side for his outside wall sheathing. A way better product when it comes to air sealing an outside wall than screwed on metal panels.

The sheathing underneath the LP Smartside is what really helps with air sealing. My memory is he used a Zip style sheathing which seals pretty well without any siding.

 

[NUTTSGT]

The sheathing underneath the LP Smartside is what really helps with air sealing. My memory is he used a Zip style sheathing which seals pretty well without any siding.

Yes, I believe it was LP's version of Zip.

Zip impressed me.

 

[mike93lx]

Yes, I believe it was LP's version of Zip.

Zip impressed me.

Yes, it's called LP Weatherlogic.

I like zip as well. The GP Forcefield board is ok, but their tape is hot garbage. Zip tape is excellent

 

[SSDVC]

Rockwool is pretty rodent proof. Even city rats stay away from it. They can't chew it or eat it, as it messes up their mouths and intestinal tract.

 

[newbie_garage_brutha]

I used rockwool instead of fiberglass because it won't mold, and it's taking a long time before I can heat the shop.... I'm in a damp climate.

I am sold on Rockwool as well. I bought 2x bundles and put up a test section. Easy install and super dense - like me

 

[newbie_garage_brutha]

Like mentioned, that was sponsored and to showcase what could be done with a post frame building to highlight his channel. If he didn't have 1.75M subscribers and a Youtube channel, he wouldn't have built his shop that way.

No doubt those guys do awesome work.


I've said it before, "Insulation is an investment." However, what is your return going to be for what you use it for ?

Have you done any pricing yet ?

Thank you NUTTSGT! Cost comparison just for the walls pretax:
Rockwool R23: $4,300
Fiberglass Batt Insulation R19: $2,900

 

[newbie_garage_brutha]

Rodents love to nest in fiberglass and as I'm told, rockwool also.
I had enough damage and odor that I had some batts replaced with blown in.
If I had to do it over again it would all be blown in cellulose.

Sounds like it's going to be a fantastic project

edit: something in the treatment is repellent to rodents.

Rusty Wrench thanks for the reply! I did not think of blow in cellulose . . . I will have to check out costs.

 

[newbie_garage_brutha]

In your house - absolutely! In a garage I am not so sure. I am all about building science and high performance construction, but I doubt a second order improvement like Siga will make much difference in what is likely to be a fairly leaky structure to begin with. Definitely price it our relative to something like spray foam that would move the air sealing to the outside of the wall.

Also, to pile on about all these sponsored 'influencer' shows on youtube. It used to be that we watched content interspersed with ads, now the content is the ad. It is kind of like instead of watching the football, with a Bud lite commercial every 10 minutes, in 'influencer world' the players would all be chugging bud lite on the field.

Rockwool and Siga both make great products, but I would take some dude paid by Rockwool and Sigas opinion about using Rockwool and Siga with a large grain of salt.

prembol I totally agree with you "the content is the ad" - well put! I am doubting Siga is the route I should take. I may stick with the Rockwool R23 and with a standard 6mil vapor barrier.

 

[loganb]

Thank you NUTTSGT! Cost comparison just for the walls pretax:
Rockwool R23: $4,300
Fiberglass Batt Insulation R19: $2,900

That's actually a smaller upcharge then I was expecting

 

[russ455]

how about rockwool along the bottom for rodent and moisture resistance, and normal insulation above ?

 

[newbie_garage_brutha]

Interesting question....I'm in the residential building industry so familiar with the products.....

As mentioned....the materials are spendy. I've used Rockwool in my house though on interior walls for sound reduction and love the product, I've never priced it against conventional blown in or batt though to see if I thought the cost was worth the benefit. In Zone 5a....the thermal improvement is pretty marginal for as expensive of an upgrade as I think using their R23 comfort batt in place of conventional fiberglass. Unless some of the other benefits were of significant value to you, I might consider going for a cheaper batt product and use that savings towards getting HVAC in sooner. If you've got a dedicated area where you expect to do hotwork(welding etc) even with metal over the top that extra protection behind the wall there would personally give me some piece of mind on any sparks etc

Your typical post frame building is an air leakage mess, so the Majrex interior barrier does make sense to helping to manage the air. As it's pointed out above though, RR's sheathed the entire structure(walls and roof) with LP's sheathing with integrated weather barrier so his building shell is significantly improved from an air tightness(and more rigid) then just doing Tyvek over framing. The blower door test results were better than the vast majority of new construction single family builds at approx .5 ACH50 and after they get interior finishes done it'll get even better

The sheathing adds significant stiffness to the structure but also just gives a better substrate to then attach siding to and from what I see on most residential construction projects, the weather barrier on the sheathing (be it ZIP or LP) is generally done "more right" then most Tyvek/Typar or similar sheet type barriers. If you're building this yourself, hanging Tyvek even as a 2 man crew on a structure like your proposing, then going back and hanging metal siding....very slow and if you get wind....good luck. They talk about it in the RR episode on sheathing but the tyvek noise in the wind...yuck.

Getting at least 7/16" OSB sheathing under that Tyvek so it can be cap stapled properly will give a far better chance of success. You might consider pricing out the ZIP or LP integrated sheathing product and seeing what that increase would be though. Yes it'll be more money in material, but it is fewer trips around the structure. Be aware they do have as I recall a 6 or 12 month UV exposure warranty limit on that weather barrier coating on at least the ZIP material so you can't let there be years between sheathing and hanging metal on the outside.

I personally wouldn't bother with the Majrex on the interior unless I was doing "more" on the exterior as feels like the kid putting his finger in the hole on the dike...more holes just keep popping up. A case of flashing tape and couple cases of caulk and time to properly seal penetrations, sill plate joints etc I think will be cheaper and better payoff than the Siga tape

loganb . . . I thank you for such a detailed response! Most of what you stated is above my pay grade many times over! I have done basic framing and insulation in my basement, but not an entire structure. My structure (post-build) has now morphed into a hang-out/workshop area and less of a storage facility so keeping the space "comfortable" year round along w/the best possible soundproofing is now the goal. I unfortunately did not go the extra step of adding OSB/ZIP sheathing under the exterior metal. Would the below be the best insulation detail in achieving my goal?

PROPOSED WALL DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screwed down vertically)
>>Dupont Tyvek
>>horizontal 2x4 girts
>>Rockwool Comfortboard 80 (between the 2x4 girts and 2X6 laminated 3-ply columns
>>Rockwool Comfortbatt R23
>>6mil vapor barrier (in lieu of the Siga Majrex 200 and associated tapes)
>>horizontal 2x4 girts
>>3/4" BCX sanded plywood 10'tall
>>29 gauge paint steel 4'tall above the plywood

I would also take your solid advise of applying caulking and flashing tape to seal all penetrations.

Any yes, that Tyvec sounds like I am in a sloop crossing the Atlantic!

 

[tworley]

Just an FYI...

 

[acer66]

Just an FYI...

Does the random unscientific field test in my shed not count?

 

[u2slow]

Thank you NUTTSGT! Cost comparison just for the walls pretax:
Rockwool R23: $4,300
Fiberglass Batt Insulation R19: $2,900

I never bought it all at once, so never really felt the price difference. I would get up to 6 bales in a shot... a range between what fit in my truck easy, 5% volume discount, finishing a wall section, and/or felt like installing that weekend.

 

[NUTTSGT]

I never bought it all at once, so never really felt the price difference. I would get up to 6 bales in a shot... a range between what fit in my truck easy, 5% volume discount, finishing a wall section, and/or felt like installing that weekend.

Sometimes, if you have a garage already in use, that makes the most sense or in a cash limited budget.


No shame in doing only what you can.

 

[hefnerconstructionlc]

I always say don't get hung up on the insulation product itself. Even more important than what insulation product to select is making sure the air is still inside of the wall cavity. If you get the building sealed up tight. The insulation can do its job. If the insulation is installed properly and neatly any insulation product should meet its r value. The real trick is to get the air stopped and not moving through the cavity. That's why fiberglass gets such a bad rap. Because it doesn't do well in that situation. And also the reason that spray foam gets such a good rap is that it does a good job of air sealing. In either case you can save yourself a ton of money, by paying attention to the details on the exterior and getting it tight and saving money on the insulation product itself.

 

[newbie_garage_brutha]

I always say don't get hung up on the insulation product itself. Even more important than what insulation product to select is making sure the air is still inside of the wall cavity. If you get the building sealed up tight. The insulation can do its job. If the insulation is installed properly and neatly any insulation product should meet its r value. The real trick is to get the air stopped and not moving through the cavity. That's why fiberglass gets such a bad rap. Because it doesn't do well in that situation. And also the reason that spray foam gets such a good rap is that it does a good job of air sealing. In either case you can save yourself a ton of money, by paying attention to the details on the exterior and getting it tight and saving money on the insulation product itself.

hefnerconstructionlc I also thank you for such a detailed response! Most of what you stated is above my pay grade many times over! I have done basic framing and insulation in my basement, but not an entire structure. My structure (post-build) has now morphed into a hang-out/workshop area and less of a storage facility so keeping the space "comfortable" year round along w/the best possible soundproofing is now the goal. I unfortunately did not go the extra step of adding OSB/ZIP sheathing under the exterior metal. Would the below be the best insulation detail in achieving my goal?

PROPOSED WALL DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screwed down vertically)
>>Dupont Tyvek
>>horizontal 2x4 girts
>>Rockwool Comfortboard 80 (between the 2x4 girts and 2X6 laminated 3-ply columns
>>Rockwool Comfortbatt R23
>>6mil vapor barrier (in lieu of the Siga Majrex 200 and associated tapes)
>>horizontal 2x4 girts
>>3/4" BCX sanded plywood 10'tall
>>29 gauge paint steel 4'tall above the plywood

 

[kettch]

details

This is the key that gets lost when we watch these systems being demonstrated. There's not always anything special about the materials themselves, but they come with specifications for installation that cover all the details that usually get missed. I'm doing a major renovation on my house right now, and after a lot of research and watching these videos, I've concluded that I can get 80% of the way there at a fraction of the cost, just by paying attention to some simple things like filling gaps, proper installation of standard materials, etc. 80% may not be acceptable for some, but it's a lot better than what most people are doing. That extra 20% would double the cost.

 

[billconner]

VENTING:
12" roof overhang on all sides w/vented soffit.
44' of continuous low profile ridge vent.

More is not better. Calculate the net free vent area and keep the combined area under 150th of the plan area, better around 1/300th, with 60% low and 40% high. Attic venting is working against the ceiling insulation in sucking interior air through it.

I've not heard of a rodent problem in cellulose and I know dense packed it's about the best for sound transmission. I think overlooked often, even though it's least expensive.

 

[hefnerconstructionlc]

hefnerconstructionlc I also thank you for such a detailed response! Most of what you stated is above my pay grade many times over! I have done basic framing and insulation in my basement, but not an entire structure. My structure (post-build) has now morphed into a hang-out/workshop area and less of a storage facility so keeping the space "comfortable" year round along w/the best possible soundproofing is now the goal. I unfortunately did not go the extra step of adding OSB/ZIP sheathing under the exterior metal. Would the below be the best insulation detail in achieving my goal?

PROPOSED WALL DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screwed down vertically)
>>Dupont Tyvek
>>horizontal 2x4 girts
>>Rockwool Comfortboard 80 (between the 2x4 girts and 2X6 laminated 3-ply columns
>>Rockwool Comfortbatt R23
>>6mil vapor barrier (in lieu of the Siga Majrex 200 and associated tapes)
>>horizontal 2x4 girts
>>3/4" BCX sanded plywood 10'tall
>>29 gauge paint steel 4'tall above the plywood

This sounds like a nice build.

hefnerconstructionlc I also thank you for such a detailed response! Most of what you stated is above my pay grade many times over! I have done basic framing and insulation in my basement, but not an entire structure. My structure (post-build) has now morphed into a hang-out/workshop area and less of a storage facility so keeping the space "comfortable" year round along w/the best possible soundproofing is now the goal. I unfortunately did not go the extra step of adding OSB/ZIP sheathing under the exterior metal. Would the below be the best insulation detail in achieving my goal?

PROPOSED WALL DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screwed down vertically)
>>Dupont Tyvek
>>horizontal 2x4 girts
>>Rockwool Comfortboard 80 (between the 2x4 girts and 2X6 laminated 3-ply columns
>>Rockwool Comfortbatt R23
>>6mil vapor barrier (in lieu of the Siga Majrex 200 and associated tapes)
>>horizontal 2x4 girts
>>3/4" BCX sanded plywood 10'tall
>>29 gauge paint steel 4'tall above the plywood

As described that looks like a good system. The Tyvek will serve as the moisture and air barrier. Which should keep the bulk water out and minimize air movement. Assuming they tape the seems nicely on the tyvek itself. Then that should get the interior space air still. Then you would have a nice insulation to go on the inside walls. Cellulose is terrific for the ceiling above if that's what you're thinking. Keeping in mind that you'll want to keep an airspace at the soffits by using baffles. Final wrapped fiberglass bats are also nice because they are sealed. And they look pretty good on the inside. The rockwool is a premium product compared to fiberglass for sure. And it does have some fire resistive properties that fiberglass does not. Overall it sounds like a nice setup.

 

[loganb]

loganb . . . I thank you for such a detailed response! Most of what you stated is above my pay grade many times over! I have done basic framing and insulation in my basement, but not an entire structure. My structure (post-build) has now morphed into a hang-out/workshop area and less of a storage facility so keeping the space "comfortable" year round along w/the best possible soundproofing is now the goal. I unfortunately did not go the extra step of adding OSB/ZIP sheathing under the exterior metal. Would the below be the best insulation detail in achieving my goal?

PROPOSED WALL DETAIL (OUTSIDE:INSIDE):
>>26 gauge 40-year painted steel panels (screwed down vertically)
>>Dupont Tyvek
>>horizontal 2x4 girts
>>Rockwool Comfortboard 80 (between the 2x4 girts and 2X6 laminated 3-ply columns
>>Rockwool Comfortbatt R23
>>6mil vapor barrier (in lieu of the Siga Majrex 200 and associated tapes)
>>horizontal 2x4 girts
>>3/4" BCX sanded plywood 10'tall
>>29 gauge paint steel 4'tall above the plywood

I would also take your solid advise of applying caulking and flashing tape to seal all penetrations.

Any yes, that Tyvec sounds like I am in a sloop crossing the Atlantic!

I have no information on the potential pros and cons of standard plastic vapor barrier vs one of the fancy products like Siga, but the makeup in general looks good. As you mentioned, proper execution of the details is key but you look to be starting out solid!

 

[newbie_garage_brutha]

More is not better. Calculate the net free vent area and keep the combined area under 150th of the plan area, better around 1/300th, with 60% low and 40% high. Attic venting is working against the ceiling insulation in sucking interior air through it.

I've not heard of a rodent problem in cellulose and I know dense packed it's about the best for sound transmission. I think overlooked often, even though it's least expensive.

Thanks billconner . . . I am broadly aware of the "more is not better". The builder put 12" vented soffit on the eave and gable ends. He was aware that I would be insulating in the future. I do have scissor trusses 4' OC (4:12 pitch bottom cord) on 32' of the structure. The remaining 12' of the structure is a raised roof/clear span/cathedral ceiling with doubled-up 2x6 rafters (created for a future loft). I am unsure if the additional venting was required for my build. The builder was aware of doing blown-in R38 for the scissor truss area and Rockwool R23 for the clear span 12' area. Main roof is 8:12. What are your thoughts?

 

[newbie_garage_brutha]

This is the key that gets lost when we watch these systems being demonstrated. There's not always anything special about the materials themselves, but they come with specifications for installation that cover all the details that usually get missed. I'm doing a major renovation on my house right now, and after a lot of research and watching these videos, I've concluded that I can get 80% of the way there at a fraction of the cost, just by paying attention to some simple things like filling gaps, proper installation of standard materials, etc. 80% may not be acceptable for some, but it's a lot better than what most people are doing. That extra 20% would double the cost.

Solid advice!

 

[newbie_garage_brutha]

I have no information on the potential pros and cons of standard plastic vapor barrier vs one of the fancy products like Siga, but the makeup in general looks good. As you mentioned, proper execution of the details is key but you look to be starting out solid!

Thank you loganb!

 

[NUTTSGT]

I always say don't get hung up on the insulation product itself. Even more important than what insulation product to select is making sure the air is still inside of the wall cavity. If you get the building sealed up tight. The insulation can do its job. If the insulation is installed properly and neatly any insulation product should meet its r value. The real trick is to get the air stopped and not moving through the cavity. That's why fiberglass gets such a bad rap. Because it doesn't do well in that situation. And also the reason that spray foam gets such a good rap is that it does a good job of air sealing. In either case you can save yourself a ton of money, by paying attention to the details on the exterior and getting it tight and saving money on the insulation product itself.

This is why I spray foamed (Great Stuff) the bottom 3 inches of my wall cavity. Fiberglass in after that.

 

[billconner]

Thanks billconner . . . I am broadly aware of the "more is not better". The builder put 12" vented soffit on the eave and gable ends. He was aware that I would be insulating in the future. I do have scissor trusses 4' OC (4:12 pitch bottom cord) on 32' of the structure. The remaining 12' of the structure is a raised roof/clear span/cathedral ceiling with doubled-up 2x6 rafters (created for a future loft). I am unsure if the additional venting was required for my build. The builder was aware of doing blown-in R38 for the scissor truss area and Rockwool R23 for the clear span 12' area. Main roof is 8:12. What are your thoughts?

It's finding the product data for the soffit and ridge vents and doing the math.

I found one Certainteed 12" vented vinyl soffit and it said 5.9 SQ IN per foot. Ridge vents I find are 18 SQ IN per foot You building is 30' wide. 1/150 is .2 SF, 1/300 is .1 Soffit both sides - 11.8 SQ IN is .082 SF Ridge vent is .125. Together over .2 or a touch more than 1/150. I wish the ridge vent was half the NFA, which would be near that 60% soffit and 40% ridge and 1/200.

My instinct is you definitely don't want more ridge than soffit and would be better off with less than 1/150.