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Old 10-28-2013, 09:35 PM   #1
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UPDATE WITH PHOTOS garage Insulation

I have read a lot on the subject of insulating garages - but none seem to apply to my situation.

First the walls:
- My garage has T1-11 siding (essentially plywood with vertical grooves). But there is nothing between the siding and the wall studs. Just T1-11 plywood attached to the studs.

How would I insulate this? Normally there would be another layer of something between the siding and the studs. Obviously moisture can get in more easily.

Faced, unfaced? Plastic vapor barrier over the insulation? Seal the backside of the T1-11? Breathe more or less?

I live in MN - a cold climate. I would sheet rock - eventually.

The previous owner put some chip board flooring on the ceiling beams to create your typical storage area in the rafters. See photo below. It covers about 80% of the ceiling area. I could easily fill in the rest. The beams are 2X4s 24 inches apart.

I could insulate between the beams. I would have to fill in the storage area floor in some parts. This would create your typical insulated rectangle box.

As the ceiling isn't robust, air would get trough to the rafters - reducing R value.

Or would I insulate the rafters? And leave the ceiling as is. Currently there is no ventilation - other than the big door the opens daily.

Need to get it insulated soon as it is getting cold. Any help would be appreciated.

I am new to the forums and can handle many electrical and paint questions.


Last edited by DoodDank; 11-10-2013 at 08:17 AM. Reason: Added photos, corrected errors
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Old 10-29-2013, 06:08 AM   #2
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What kind of shape is the siding in and how often will you be heating it?

If you are just looking to keep the cold out, I would not get too involved.

Loose fill in the "attic" after you seal the top plates and make sure the ventilation is preserved. Finish off the attic floor/ceiling and go loose fill. It is near impossible to insulate the ceiling effective and cheaply.

On the wall, rigid foam between the studs and air sealed works well and I would leave a small air gap against the T1-11 so that you have a drying area. T1-11 is pretty notorious for letting in water at one point or another.

What is the wall construction (i.e. 2x4 or 2x6)?

How will you be heating the space?

Make sure your interior walls are air tight and you might want to consider something in the smart vapor retarder class like MemBrain.


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Old 10-29-2013, 06:17 AM   #3
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What he ^^ said.....

But while your at it....plan out your electrical. Now is the time to run all the outlets you might want. Even if you don't have the typically only use one thing at a time. So wire it up now....maybe add a sub-panel later with more power. Much easier to wire in if your already have all the outlets run.

And...put those outlets at about 50" above the lets you lean a 4x8 sheet of plywood up against the wall and not cover the outlet.

Your starting your project a little hard would it be to remove the T11 and put in a wrap? Otherwise, I like the Rigid foam idea....even 1" would help a lot and water does not bother it...then you could fill the back side with standard batt insulation.

Your big concern is that you can trap moisture in the wall cavities if it gets in from the outside....hence, the advantage of using rigid foam or pulling off the siding and doing a vapor wrap.
Even if you are on the right track, you will still get run over if you just sit there.

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Old 11-10-2013, 01:19 AM   #4
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Updated Info

Hey guys, thanks for the advice.

I wasn't able to make myself clear with the written word - so I have some pics.

- I will not be heating the garage. My main goal is to keep it from freezing. Also want snow & ice to melt off Suburban when parked in garage (as does in my other garage).

- Siding is in good shape.

- There is no attic. As per pics the previous owner made a storage space above the beams with chip board. It is mainly open.

- 2X4 construction. Walls 16 on center. Ceiling 24 on center (kind of).


Idea 1:

Seal with Great Stuff.

use 3/4 Expanded Polystyrene Insulation with a 1/4 ferring strip of some sort to give it drying gap from the T1-11.

Use BATT on top.

Add vapor barrier of some sort.

Idea 2:

use 1.5" Expanded Polystyrene Insulation with a 1/4 ferring strip to give it drying gap from the T1-11.

Add another 1.5" Expanded Polystyrene Insulation with a 1/4 ferring strip between the other Polystyrene. This should be flush.

Not sure if need any vapor barrier.

Idea 3:
Stick some cheap unfaced BATT, cover with plastic and call it a day.

Idea 4:

Stick some cheap faced BATT - with face outwards, cover with plastic and call it a day. Save a lot.

Idea 5:
use 2" or 2.5" Expanded Polystyrene Insulation or Rigid Foam. Seal it in with Great Stuff. Call it a day.


Ceiling or rafters?

Can I insulate the rafters? Do I really need ventilation in a non heated garage with a huge door that opens daily?

It would be easier to insulate the rafters and seal off the soffits.

If I insulate the ceiling the I have to deal with the 4 X 4 opening to the storage area.

Vapor Barrier / Retarder

MemBrain is ideal but $110 for more than I will need. Can I just use cheap poly plastic?


Attached Thumbnails
garage Insulation-img_2080.jpg  

Last edited by DoodDank; 11-10-2013 at 01:27 AM.
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Old 11-10-2013, 01:23 AM   #5
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The pics

Take a look.
Attached Thumbnails
garage Insulation-img_2081.jpg   garage Insulation-img_2076.jpg  

Last edited by DoodDank; 11-10-2013 at 01:29 AM.
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