Would This Be Stupid? - Insulation - Contractor Talk

Would This Be Stupid?

 
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Old 07-08-2018, 12:51 PM   #1
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Would This Be Stupid?


I live south of Houston where it is oppressively humid. I plan on insulating my garage and putting in a portable air conditioner. I have considered just throwing some batts in the attic, but the better stuff would cost close to the same price as having someone come blow some insulation in. However, I saw this product https://www.homedepot.com/p/UltraTou...6482/202710055 and thought I could save some money. It has no vapor barrier and I really don't know how much that matters, except that is how you do it properly. Even if I did 2 layers to get to R-13, it would still be pretty cheap.

So, what could go wrong?

I also plan on doing the doors and maybe having someone blow in some insulation in the walls. So, if any of you guys in my area do this kind of stuff, shoot me a pm.

I am not against spending money to do it right, just prefer saving money whenever possible. If that stuff would work out, it seems like it would be the cheapest way to go.
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Old 07-08-2018, 12:57 PM   #2
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Re: Would This Be Stupid?


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Originally Posted by BugmanBCE View Post
I live south of Houston where it is oppressively humid. I plan on insulating my garage and putting in a portable air conditioner. I have considered just throwing some batts in the attic, but the better stuff would cost close to the same price as having someone come blow some insulation in. However, I saw this product https://www.homedepot.com/p/UltraTou...6482/202710055 and thought I could save some money. It has no vapor barrier and I really don't know how much that matters, except that is how you do it properly. Even if I did 2 layers to get to R-13, it would still be pretty cheap.



So, what could go wrong?



I also plan on doing the doors and maybe having someone blow in some insulation in the walls. So, if any of you guys in my area do this kind of stuff, shoot me a pm.



I am not against spending money to do it right, just prefer saving money whenever possible. If that stuff would work out, it seems like it would be the cheapest way to go.


R-13 is less about than half of what you need. When you condition that space, you will create too much condensation.

It would be far better to not insulate at all and make sure you have excellent ventilation.

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Old 07-08-2018, 01:14 PM   #3
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Re: Would This Be Stupid?


If there's a vapor barrier on the conditioned side..why would condensation be a problem? That's how I would do it.

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Old 07-08-2018, 01:29 PM   #4
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Re: Would This Be Stupid?


Hot and humid, so the vapor retarder goes on the outside of the envelope.

As usual, air seal before you even think about insulating.

Last edited by hdavis; 07-08-2018 at 01:34 PM.
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Old 07-08-2018, 01:39 PM   #5
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Re: Would This Be Stupid?


Denim insulation has no vapor barrier. R-30 is what is recommended for his area.

A vapor barrier will just collect condensation if there is not enough insulation to stop the penetration of the humid air.

If you have enough insulation, then a vapor barrier is not required.

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Old 07-08-2018, 02:25 PM   #6
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Re: Would This Be Stupid?


You know if you buy blow in insulation at Home Depot they will let you use their blow in machines for FREE! Just reserve the machine in advance, get a buddy or spouse to feed the machine. Very easy job to do. You can bore holes in the walls between the studs and fill them up too. No need to hire someone to do the job for you.



Not used to living in a humid area, but attic fans displace a lot of heat, and help protect the roofs.
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Old 07-08-2018, 05:12 PM   #7
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Re: Would This Be Stupid?


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Originally Posted by hdavis View Post
Hot and humid, so the vapor retarder goes on the outside of the envelope.

As usual, air seal before you even think about insulating.
I live in the swampy summer weather conditions of DC (hot and sticky) and we put the vapor barrier facing the envelope. Houston is kind of the same, only for longer.

How about foam board and cover it, since it's a garage?
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Old 07-08-2018, 06:33 PM   #8
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Re: Would This Be Stupid?


The math is off. If you double that material, you are at $2 a square feet for a mere R13.

Check with https://insulationguru.com
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Old 07-09-2018, 09:31 AM   #9
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Re: Would This Be Stupid?


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The math is off. If you double that material, you are at $2 a square feet for a mere R13.

Check with https://insulationguru.com
OOPS! You're right. I thought it said 48 feet, it's inches. Big difference. So there goes any cost savings with that plan.

I'm not sure I need R-30. I seriously doubt my attic is R-30. Walls are R-13 normally. I know R-30 is recommended, and that's certainly better, I just wouldn't think it is a must.

If I call somebody to do the garage attic I plan on having them do the whole house. Might as well bring it up to specs.

I know this is something I could DIY, but I really don't have the time. Well, I could roll in some batts in the attic above the garage, but that really isn't cheaper than paying someone to blow it. I'm not going to blow insulation myself. Just not going to.
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Old 07-09-2018, 09:33 AM   #10
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Re: Would This Be Stupid?


Then don’t keep that space conditioned all of the time. Just turn on the a/c when you are needing it.
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Old 07-09-2018, 09:59 AM   #11
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Re: Would This Be Stupid?


Thanks. You've been so helpful. Let me take this a different direction real quick.



My intention is not to turn it into a conditioned living space. I would definitely like it to be much cooler in there. Also, all my stuff rusts and molds and deteriorates like crazy in the garage. I want it drier and cooler, and I know to do that I would prefer to go with a portable air conditioner. But doing that without insulating the doors, walls, and attic is fairly pointless. I probably won't run that a/c at 70°, 80 is more likely, 75 or 78 sometimes. I just need to take the edge off.



Anyway, so considering I am not looking for optimal performance, there seems to be a major price difference between R19 and 30. You think R-13 would lead to condensation, so we can leave that out. Would rolling in some R-19 be sufficient for these goals?
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Old 07-09-2018, 10:05 AM   #12
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Re: Would This Be Stupid?


Quote:
Originally Posted by Peter_C View Post
You know if you buy blow in insulation at Home Depot they will let you use their blow in machines for FREE! Just reserve the machine in advance, get a buddy or spouse to feed the machine. Very easy job to do. You can bore holes in the walls between the studs and fill them up too. No need to hire someone to do the job for you.



Not used to living in a humid area, but attic fans displace a lot of heat, and help protect the roofs.
The HD machines will blow loose, but they won't work for drill and fill. Something like a Force 2 that can be rented will do it.
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Old 07-09-2018, 10:06 AM   #13
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Re: Would This Be Stupid?


R19 (unfaced) would be my personal minimum. However, even in colder climates, some use R13.

The problem down here (I am in Gulf Shores), is exactly the mold issue.

Ventilation is key. Keep the air moving at all times. Leave everything “cracked” open.

In our RV, we use Damp Rid. That helps, but must be watched.
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Old 07-09-2018, 12:05 PM   #14
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Re: Would This Be Stupid?


Well, it looks like blown is the only solution anyway. I got up there and measured and the rafters are 17.75" apart. They don't make batts that size.
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Old 07-09-2018, 12:06 PM   #15
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Re: Would This Be Stupid?


Quote:
Originally Posted by BugmanBCE View Post
Well, it looks like blown is the only solution anyway. I got up there and measured and the rafters are 17.75" apart. They don't make batts that size.


Then call insulation gurus.
They are experts in your area.
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Old 07-09-2018, 12:18 PM   #16
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Re: Would This Be Stupid?


A couple of notes

DC and Houston are way different. Houston's heating season is very short, vapor barriers are set up for AC, not heating. You don't want hot humid air moving through the wall system and condensing on the inside wall surface, so the vapor retarder goes on the outside of the wall system.

As a practical matter, you're stuck with however it was built.

The major source of condensation in retrofits is outside air moving through the walls and ceiling. Air seal penetrations before you start insulating.

If you run a window AC unit, you will remove some of the moisture you're concerned about, but it isn't that straight forward to prevent rusting. If you have temperature swings, your equipment can end up being cold when hot humid air is present, and you'll get condensation. IMO, keeping a dehumidifier running is needed to prevent condensation issues. Alternatively, you can keep the AC running all the time to keep the temp stable.

While you're figuring all that out, consider wiping your tools with Ballistol, or putting a chunk of camphor in your tool box, or similar methods of preventing rust.
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Old 07-09-2018, 01:07 PM   #17
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Re: Would This Be Stupid?


^^ solid advice
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Old 07-09-2018, 05:26 PM   #18
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Re: Would This Be Stupid?


Buy yourself lots of new [email protected] that come with silica packs. Re-deploy them in the garage.

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