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Insulate unheated garage wall. Good or bad idea?

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Oct 11, 2012, 11:00 PM
Insulate unheated garage wall. Good or bad idea?
One half of the Northern wall of my garage is adjacent to the house. The back half of the wall is adjacent to the outdoors.
I must re-insulate the half of the wall that is shared with the house, but is it worth continuing the insulation to the back half?
The exterior of the back half can get moss and black spots on it. Would insulating that wall make things better or worse?

Oct 12, 2012, 07:53 AM
It would not hurt anything but it'a also not going to most likly have any effect on the mold and moss.
Keep in mind your not suppost to leave Kraft faced or foam insulation exposed.
Most areas call for 5/8 fire code drywall and you have to seal any holes where wires or plmbing were run with fire block caulking.
Make 100% sure any wires for outlets, sound or cable get ran before coving the wall.
You can never have enough outlets in a garage.
That mold is likly an issue of lack of air flow, to much shade.
If it's forming just at the bottom of the wall we need to see a picture of it.
Quite often the siding was run to close to grade, and can cause major issues.

This message has been edited. Last edited by: joecaption,

Oct 12, 2012, 12:25 PM
Thanks for your reply Joe.
The green "stuff" and black spots usually form higher up the wall (around 6 to 8 feet).
No doubt the grade is too close to the siding. The original owner/builder didn't leave me much to work with. The foundation itself is pretty close to grade. As it is, I've moved dirt so it doesn't touch the siding anymore, but now I have flat (at best) and negative slope around much of the perimeter of my house.
I'd like to re-grade the whole lot, but that's more expensive than I can afford right now. I can't just push the dirt around either. The public works guy said I'd have to get the dirt hauled away.
As a stop-gap, I'm hoping to put an AZEC (PVC) banding board around the entire perimeter of the house. I'm not quite ready to do that yet either, but that should be more affordable than a major re-grading job.

Good points about the outlets and cables.

Any other ideas about the grading challenge?

Thanks again.
Oct 12, 2012, 05:02 PM
Post some pictures for some ideas.
I've done a ton of this type work and have found some simple (to me) ways to get around the issues.

Oct 12, 2012, 11:01 PM
I found some pictures. They're not terribly recent (that will be obvious by the snow in some of them), but the house hasn't moved since then ;-)

This first picture shows how close the grade is to the siding in some areas.
Window Bump out faces East
Actually, since that picture was taken, I dug out the dirt under that window box, put down hardware cloth and about three-four inches of stone. Chipmunks had been burrowing under there and actually pushed dirt right up to the underside of that bump out. You had given me some advice back then when I was debating about applying sealer to the block exposed when I dug out the dirt.

This next picture shows the part of the garage I described in my original post. It is the section furthest away and to your left in the picture.
Garage and House facing North-East

This next picture shows the entrance on that North side of the garage:
Entrance to garage from back yard.

In the following picture, the grade is still pretty close to the siding, but, believe it or not, I actually removed a lot of dirt to get that much space.
North face of house
At the time the picture was taken, I still had mirrors up covering the holes the woodpeckers had made clear through the walls. Since that picture, I've patched in shingles to repair the holes.

This last picture shows the West face of the garage.
Garage entrance faces West
The house siding (your left in the picture) actually touches the asphalt.

I hope these pictures give you a better idea of what I'm talking about. As with so many things with the house, I start thinking about one issue and it seems to expose ten more.

Thanks again!
Oct 15, 2012, 05:40 AM
Just my opinion...
If the garage is not being heated/AC and the house is insulated, there is no reason to insulate any portion of the garage.

This message has been edited. Last edited by: ron45,
Oct 18, 2012, 04:24 PM
JB Builder
Insulating it will not matter for exterior green "nature mold".
Your northern side of house is always dewy.
House wash was invented but i don't use it.
I use pressure washer once a yr with scrub brush and baking soda as the soap. An elder told me to use it and ever since i have. Seems to stay gone for long while after pressure washing in downward fashion without flooding out the bildrite sheathing behind it. next yr = new siding and housewrap<--

I noticed difference in insulating my unheated garage. It keeps the house much warmer.
I simply insulated with junk insulation but in a nice manor. Then fire rocked the firewall side of house 100% then i used normal 1\2 inch sheetrock for exterior walls. Tape, mud, scraped it and it sits.
I also closed up 4 out of 6 soffit entrances and installed 1 roof vent in exposed ceiling.
I made the remaining 2 soffit entrances a bit smaller with a removable 2x6 block with rectangle jigged out of inside center and then metal-galv screen attached.
Whats nice is the fact i can remove these 2 blocks, 1 being on each side of garage in summer time to push air into different directions.

This message has been edited. Last edited by: JB Builder,
Oct 18, 2012, 10:03 PM
JB Builder,

Thanks for your reply. I usually wash/scrub the green "stuff" off every year too. Haven't tried baking soda though. I've used bleach. I've used Stain Solver (Oxygen Bleach). The green stuff stays away for a while, then manages to come back.

I don't understand why you would go to 1/2 inch sheetrock after a fire. It seems you'd want the 5/8 fire rated.

Also, don't understand what closing off the soffit entrances did for you.

Thanks again.
Oct 19, 2012, 08:27 AM
I also question the reasoning of making the soffits smaller or closing them off.
Sure sounds like a great way to defeat the whole reason there there in the first place.

Oct 19, 2012, 10:22 AM
JB Builder
You're welcome.
I used bleach many times in the past and find it hassle to breath, get on ground etc. .
So i dump a full box of baking soda into the hopper with about 2 good squirts of anti bacterial liquid dishsoap. Maybe 7 tablespoons worth at least.
I thought about it and i keep thinking bleach is better though but just more dangerous. I'll give bleach a whirl one time before the snow gets me and let this thread know.
There is other mold killers on market which work better, perhaps safe; unsure.

The 1\2 inch sheetrock is just on outer most walls not attached to house.
The house connects with 60 percent of garage north wall and 40% of this north wall wasn't insulated or rocked. Its backside is outside.
So i insulated this 40% North house wall and rocked it with the 5\8 Fire rock.
The 2 walls, West and East also the garage door entry wall "south" was done in 1\2 inch because doesn't need fire rating and saved me few hundred dollars at least. The money saved was able to be used for afi and gfi breakers, some gfi tamper resistant outlets, sub panel, romex coils. You get the idea. Also i had some 1\2 inch rock laying around which also saved some cost and gave me back a corner of garage in process. I wish i used vapor barrier though but we did spray foam around the stud cavities so the drafts are gone. ( I plan to finish the ceiling and heat it eventually. ) But as most hesitant people will say " It's just a garage. ( I like the garage more than the house. )

The soffit entries; was 6 of them, 24 inches wide each. (outside soffit pans are aluminum with hundreds of breathers.
3 on west, 3 on east. 3 car attached garage.
I filled 2 on west and 2 on east. Keeping only the middle one on each side. Not gable or not far back.
Just the middle one on each side is open.
This was still too drafty so i put in the required roof vent after finding a way to get into the rafters with no ladder at the time and monkey my way to the ceiling osb with a drill to mark the spot.
I tossed in a roof vent and i noticed improvement with air uplift right away before i got down from roof.
I added the screen hole blocks because we were attacked by bees in summer and east soffit entrance was their cave but it still vents very nice.
A lot of draft. Very cold still. Good circulation just not too much as before. Maybe a few degrees difference for duration when cold front moves in.
Example: i am working in garage until 8pm.
It would get too cold at 6pm.
After insulating, rocking and adding vent, blocking 4 of six 24 inch openings i can go until 8pm easily and find myself out there much later without knowing it.

p.s. In the Entrance to your garage.
I notice a gap between the sidewalk and blockwall.
You should fill the gap with some kind of patch so in winter it won't expand once water gets in.
Maybe a 5 dollar tube of cement caulking. "unsure ponder"
I don't know what to use off hand. Ask paint dept?

This message has been edited. Last edited by: JB Builder,
Oct 19, 2012, 11:22 AM
JB Builder
Any other ideas about the grading challenge?

Sorry i didn't see the grading question previously.
I attached an image to explain this.
Yellow box is the 2 foot deep rock pit pre wrapped with 3 layers of cheap fabric.
Red lines is slope away from edges down into the pit.
Both solid drain tube tiles you see are for the back and front gutter downspouts we integrated into the ground and have nothing to do with this rock drain idea but pass nearby.
The main goal of this was to slope the drainage away from the house by 1 foot and then into the big non exposed rock pit. The top plastic overlaps into the rock pit by about 1 to 1.5 feet and the rock pit is about 2 to 2.5 ft deep and in this case about 3.5 to 4 ft wide circle. All edges slope toward the rock pit as i explained above.
If you can't slope your yard 12 feet from house or city giving you grief somehow, this is probably your best method to pull water away from house and still have ornamentals or garden perimeter etc.
Let me know what you guys think. I sort of invented this on my own for this jobsite below because they had a lot of water coming down this hill ending up in this flat spot which was impacted rock like you see further uphill. Now no problems.
I have a front yard example of this house which has a 1.5 foot wide rock trench about 10 feet long.
If want an image let me know.

This message has been edited. Last edited by: JB Builder,

diy rock drain

Oct 21, 2012, 12:19 AM
Thanks for your explanation JB. With the decreased number of vents in your garage and increase of insulation, are you at all concerned about moisture between the rafters?

You're right about the crack that should be filled. I'll try to find the time to do something about that before the snow flys.

I wasn't able to view your image. Tried on two different computers.

Oh. And about bleach. It is seriously caustic. Last time I cleaned the exterior with it (Fall of 2010), I wore heavy rubber gloves, but the bleach/water kept dripping to the edge of the gloves when I worked above my head. It rubbed a few layers of skin off. I still have a scar from it. That's why I switched to the Stain Solver (Oxygen Bleach).
Oct 22, 2012, 12:53 PM
JB Builder
I think you may need to click refresh button in browser or delete temporary internet files if browser is getting clogged up.
I use Google Chrome browser for board hopping and contains spell checker too.
I notice no matter which browser i use, i still have to click refresh on most forums including this one to see updates. Let me know. I can post on HTTP also.

I thought of moisture but with the added roof vent and garage doors leak air bigtime it is still very drafty and probably cycles the entire volume of garage about 20 times an hour. The air is very crisp outside and exact same inside but very less breeze.
My friends chain smoke in garage and it vents very well.
Although i am planning to open up 1 more 24 inch opening to bring slight more cross draft in from the windy side. The air pours out the roof vent above as it should i guess.
Oct 23, 2012, 10:23 PM
Hi JB.
Still can't see your photo. I've refreshed, cleared history, and cache.
I use Firefox. It's usually pretty cooperative.
Oct 27, 2012, 07:30 AM
If you insulate one part of the wall you really should insulate it all. Without insulation on the "exposed" wall, you will be letting the cold air in which will make the insulated part pretty non-effective.
Oct 28, 2012, 12:03 AM
JB Builder. I didn't do anything differently, but now I can see your picture. I'm wondering if my anti-virus was blocking it before. Anyway, interesting approach. The house you pictured is pretty different than mine. Your house appears to be built into sloped grade. Mine is on fairly level ground.

Ordered, I don't see how a non-insulated "exposed" portion would cause the insulation in another section to be "non-effective". I understand how allowing the garage, as a whole, to get cold would make the insulated section less effective then if I had a fully insulated garage. To make sure we're talking about the same thing, I'll describe the situation another way. Imagine a 22 foot garage wall. 12 feet of the wall is adjacent to the house (i.e., that section of the garage wall is the exterior to a section of the house). The other 10 feet is adjacent to the outdoors.
The section adjacent to (shared with) the house is insulated. Even if the 10 foot section that is adjacent to the outdoors were, let's say, a large screen, I don't see how it would make the 12 foot, insulated section, non-effective.

This message has been edited. Last edited by: SturdyNail,
Nov 18, 2013, 02:06 AM
For me this sound bad idea but if you think that it is perfect for you on doing it well you should do it.In Finland where my friend live every year he is doing some replacement and this year he replace all their inner doors or sisäovi which i never thought can be perfect in his home.
Nov 18, 2013, 04:23 PM
Just for fun I did a quick check. By following the shortest possible straight line, the Philippines and Finland are 6,000 miles apart.

Hard to imagine anyone getting them confused.

Nov 19, 2013, 05:35 PM
Jaybee, you're assuming this spammer can follow a straight line. He/she hasn't yet figured out yet that we don't speak Scandinavian on this forum. Perhaps even determining what a straight line is is too advanced for him/her.

This message has been edited. Last edited by: GardenSprite,