Insulation on Outside of Wall?

[AldeanFan]

Whenever it gets cold I start thinking about insulation, and it's sure cold this week!

I have a 20x20 concrete block garage attached to my house with a breezeway separating the house and garage. The garage was built sometime in the 70's after the house was built. I heat with a Mr Heater Big Maxx. The ceiling is drywall and insulated with R12. I also have an insulated door. I don't have any insulation on the concrete block walls! I live in Southern Ontario Canada, today it's -14C and I'd like to work in the garage tonight after work.

The furnace keeps the garage warm but I know I'm loosing lots of heat and it's not economical heating so much uninsulated concrete.

Since space is at a premium I want to maximize R value while minimizing how much interior space I loose to insulation.

I've been considering strapping the interior walls and insulating with foam board covered in either drywall or plywood (i'll leave the drywall/plywood/chipboard debate for another thread!) since it is a better Rvalue per inch, but that involves pulling out all the existing electrical, shelving cabinets etc, and I'd loos a little interior space.

Has anyone insulated the outside walls? I've seen foam board added to the outside of old houses over the sheathing, then siding over top. The outside of my garage walls is just white paint (house is white brick) and needs painting anyway so white vinyl siding would actually improve the looks. The only limits to how much insulation I could add on the exterior would be cost and the depth of the roof overhang!

I guess the question is would insulating the outside make a significant difference in my heating costs without insulating the inside. I really only have the budget for one or the other this year so should I insulate inside first or outside first?

Thanks!

 

[burleyfarm]

I would do the outside first. JMO You gain insulation and an upgrade to the appearance of your garage (wife and neighbors will like that). No shelving, cabinets or electrical to mess with.

I would consider at least 1.5 inch if not more. I've seen it done with 1.5 inch furring strips with 1.5" rigid in-between the furring and another layer of 1/2" to 1" layered over that to provide a thermal bridge over the furring strip. You just need longer siding nails.

If you are only using the garage occasionally this might be enough for the walls. I would also add more to the ceiling trying to get closer to R-30+++ as I am told that is your biggest heat loss. It goes without saying to seal up any and all penetrations in the walls and ceiling. My only concern with going to the outside would be to make sure you have an adequate layer of insulation over the wall top plate.

Update. I just reread your post. I would first add insulation to the ceiling as I think this would provide your biggest return on investment. Then I'd do the outside wall. The ceiling work can be done in the dead of winter and is much easier than working out in the below Celsius weather. Blown in fiberglass or cellulose is pretty easy to do.

 

[Wood'nMetal]

Is the outside of your house block? I'd think it would look odd to insulate the outside of the shop and not do something matching on the house.

I think I would opt for 2x2 framing & plywood inside the shop and spray foam insulation. Minimal loss of shop footprint and it will make it easier to attach items to the walls.

 

[AldeanFan]

Thanks for the quick reply's!

I've been thinking about the attic, the snow doesn't melt off the roof of the garage so I know that's not a major source of heat loss, but I'm sure the insulation could be improved.

I think the real problem is that the concrete holds the cold, instead of holding heat, and acts like a heat sink pulling heat out of the garage.

My long term goals will be to insulate both the outside (say R12 foam) and inside (say R 10) which will hopefully make the block walls a big air warm air space, and to add insulation in the attic and build a floor for easy storage. Since I only have the budget do do one thing at a time I'm trying to prioritize as i go. Last year was the furnace, this year will be one of the 3 insulation projects, outside of wall, inside of wall or attic.

The house is white brick, the garage is concrete block except for the front of the garage which is white brick to match the house.

Since the garage is in need of paint this summer anyway I'm leaning toward gluing 2" foam to the outside garage walls, then attaching furring strips with tapcons through foam into the block, and covering with vinyl siding.

 

[buddyboy]

good advice so far

i would try to do all the wall insulation on one side, either outside or inside.

in your case outside

putting foam on both sides of the block might trap moisture.

you can either keep the heat away from the block by insulting in the inside or trap the heat in the block by doing it on the outside.

again, i would go outside to trap heat in the block, that thermal mass will help even out the temperature fluctuations on both super cold days in the winter and super hot days in the summer.

 

[buddyboy]

also if you can I would run that 2" foam on the outside at least 2 feet into the ground to help keep your slab warm too

 

[brianh]

With the insulation on the outside you get the benefit of that concrete being a nice big chunk of thermal mass once it warms up it will stay that way for a while, should be cooler in the summer too.

 

[rburke65]

Don't know about the moisture but it would have to easier.... in my opinion, to attack the outside area of the garage than the inside. Good luck.

 

[ddawg16]

Block?

Look into insulated vinyl siding. It's basically your typical vinyl siding with about an inch or so of foam behind it. Not only would it improve the look of your garage, but help with temp control.

 

[Disney]

Concrete does not act as a heat sink. If you sufficiently heat it, it will stay warm.

Is the inside sealed? If it's block walls you'll gain a lot by just sealing the walls.

I would also go with a decent infrared heater, but that's just me. I like to heat objects, not the air.

 

[JACDes]

concrete is a terrible insulator, but an excellent conductor.

it does not "hold the cold or hold the heat" Concrete can be used for passive solar design using it's thermal mass to absorb heat during the day to release it over night to but we won't get into that.. let's keep it simple and say; Concrete conducts heat thru itself.

when this occurs at walls to the cold outside air we call this "heat loss"

in the summer it does the reverse.. it conducts the heat of the hot outside air thru the walls to the cooler inside. we call this "heat gain"


in-sulation or out-sulation. Makes no difference the purpose is to slow down the conduction of heat (heat loss or heat gain) thru the wall, roof, or floor

Do whatever is easier, if you don't want to move anything off your inside walls put it on the outside. 2 inches of rigid insulation like you see at the box stores is R10.. if you want to spend more for polyisocyanurate ( polyiso fo short) 2" polyiso is R14.

we can ignore the thermal bridging created by the fasteners.. that is negligible.

You can secure the 2" boards to the block with wood furring strips; 16" or 19.2 o.c. you will need 3- 1/2" or 4" tapcon screws. the furring allows you the hang the vinyl siding or other finish to match the house. try to used treated lumber or cedar. if you can't get treated furring you can easily rip treated 2x4s in half if you have a table saw.

A nice job for a DIYer. I would do the exterior, later on if want more insulation you can do the interior. same way skip the siding and finish the wall with plywood/osb/gyp. bd. or any combination, knock yourself out.

good luck and send me your address so I can mail you an invoice for the remedial course in heat loss.

 

[buddyboy]

i need some help understanding why a thermal mass that is also good thermal conductor is considered more efficient than a thermal mass that is a poor thermal conductor.

 

[K'ledgeBldr]

You could just have the walls injected with foam.
No loss of floor space- as minimal as it would be otherwise.
And the outside can just get a fresh coat of paint.

Done!

The problem with putting XPS on the exterior, you shouldn't leave it exposed to the elements for an extended period of time- damage, UV, etc.

 

[elronin]

You could just have the walls injected with foam.
No loss of floor space- as minimal as it would be otherwise.
And the outside can just get a fresh coat of paint.

Done!



I was just gonna say the same thing but there will be lots of holes in the concrete.
Here is a link http://www.sprayfoamfacts.com/core-fill-foam-insulation/

 

[David C]

What you might be missing, and should consider, is the effect of the thermal mass when insulating the outside of your concrete walled structure.

If you have a steady state situation, (constant temperature on the inside and outside of the building) it doesn't matter whether you insulated the inside of the walls or the outside. No more or less heat is used with either construction detail.

However if you heat infrequently exterior wall insulation will result in using more energy than if you insulated the interior side of the walls. You are also going to be disadvantaged by the thermal inertia of the massive wall elements.

If you go out to your garage in the morning and turn on your furnace it is going to take a long time to heat your walls. Even though the inside air temperature is warm your body will be radiating heat to the colder concrete walls and you will feel cold.

If once your garage is heated you turn off the heat all of the heat energy stored in the massive walls will dissipate and be wasted. If you cycle interior temperature frequently you will be using more energy with the exterior insulation construction.

Massive interior construction, whether it is walls or floor slabs, are disadvanged in places where there are large temperature swings during the day.

Regarding the conductivity question: If you have walls of equal mass (and thickness) but different conductivity the cycle time will be shorter with the wall with greater conductivity. The wall with higher conductivity will heat up faster and release stored heat faster.

 

[JACDes]

last I checked CMUs are hollow, the shell is about 1.5 thick.

nothing massive about the CMU walls unless the whole wall is grouted solid.

even then exterior insulation on CMU has been used for decades in all types of climate zones.

 

[41ratrod]

I agree with all above. PUT if it was me doing it I'd do the outside not only
would it help controlling the temp put make the house look better.
And do the inside later.
Just my 2c worth.

 

[tms0425]

I used these on the inside of my concrete block garage and like them a lot. Very easy to handle, cut, and apply in one step. They have a rain screen built in for use on the outside and siding can be directly attached to the plastic studs.

http://www.insofast.com/ex-panels/

 

[David C]

I have never seen a hollow CMU wall in my state including buildings that were built 60 years ago. Not all CMU walls remain ungrouted.

JACdes, I disagree, concrete does "hold" heat. You said it yourself, when it is used in passive solar design it stores heat. Q=MxCpx(delta T)

 

[DC73]

Has anyone insulated the outside walls?

Recommend you spend some time reading on this website: http://www.buildingscience.com/

Click on the information tab. It's been awhile but I know I've read an article there about insulating the outside of various types of building. Their Builders Guide book for your climate would be worth owning.

DC

 

[JWVan]

You are in a cold climate, probably do not desire to cool the space in the summer. Unless you spend the money to put dry-vit or siding on the exterior you are limited to insulating on the interior of the building. There are Z purlins made that make the installation quick and not to pricey(use a rigid insulation). If this is more than you want to spend, then fur the wall as discussed above.

 

[MoparTrucks]

I used these on the inside of my concrete block garage and like them a lot. Very easy to handle, cut, and apply in one step. They have a rain screen built in for use on the outside and siding can be directly attached to the plastic studs.

http://www.insofast.com/ex-panels/

Any pics? Looks interesting, I have a concrete block garage attached to the house I wouldnt mind doing something with like that.

 

[404]

Do the outside. The block wall will then help keep your inside temp steady.

Foam in the block is bypassed by the cement webs between the two block faces so not so efficient.

In the summer, blow cool air into the garage at night it it will stay cooler during the day.

 

[JACDes]

I have never seen a hollow CMU wall in my state including buildings that were built 60 years ago. Not all CMU walls remain ungrouted.

JACdes, I disagree, concrete does "hold" heat. You said it yourself, when it is used in passive solar design it stores heat. Q=MxCpx(delta T)

Concrete yes, CMU not so much. No offense but discussing passive solar design is beyond the grasp of most lay people.

I am not going to go into all that on a "garage forum".
Like I said: Keep it simple, for this instance.

I am not sure what CMU units or walls you have worked with let alone detailed for an wall assembly but they are not solid block. The hollow cells are only grouted as req'd per the wall design. is most cases #5 vert. rebar @ 4'-0 o.c requires solid grouting, or bond beams.

In the old days cells used to be filled with vermiculite to help insulate the CMU.

OP will be just fine with outsulation or insulation.

 

[JACDes]

http://masonrysystems.org/wall-systems/single-wythe-reinforced-concrete-block/


Solid blocks do exist but are not economical or practical for most wall construction since
rebar cannot easily be added to increase shear and anchor the wall to the foundation.

Size & shapes sold »

CEMEX manufactures standard and specialty concrete block, ranging in size from 4 to 16 inches.

Styles include:
Standard concrete block (double-cell)
Single cell block
Solid block
Single scored block
Double scored block
Three-score block
Return corner block
Half-high block
Angled block
Sill block
Sash block
Header block
Bondbeam Lintels / Recess lintels
Single bull nosed block
Double bull nosed block
Cap block
Sound block
Pilaster block
Round block
Water Repellent Block

- See more at: http://www.cemexusa.com/ProductsServices/Block.aspx#sthash.d7t3lhuN.dpuf

 

[rburke65]

Most CMUs are hollow.....and I will add.....in my opinion.

 

[NUTTSGT]

When I sided the outside of my garage, part of it is CMU and I insulated it. I tap-conned firring strips on the outside, used some 3/4" white styrofoam between them. I then sheathed over that with foil-faced OSB and put my vinyl siding over that.



Before that I did the inside using the same method but with 2x4s flat on the wall.

I then used 1.5 styrofoam between the studs and covered it with OSB.



Does it help, when I did the interior, I also covered the old wood O/H doors with some 3/4" foil faced polyiso. I struggled to keep the garage 70 degrees in the Winter and afterwards, it was alot easier to heat and retain heat. Even when I did get it warm in there, the baclk block wall was still cold before insulating it.

 

[tms0425]

Any pics? Looks interesting, I have a concrete block garage attached to the house I wouldnt mind doing something with like that.

I posted a couple pictures on another thread HERE

 

[tjpavlov]

Check out insofast.com. they have products for inside and outside.

 

[burleyfarm]

also if you can I would run that 2" foam on the outside at least 2 feet into the ground to help keep your slab warm too

I agree. This will help with heat loss through the floor and whatever type of foundation you have. I did this after the garage was done and it has helped.

Based on my experience with vermiculite filled cores I wouldn't waste my time or money on filling the block cavity. One, there is too much settling and two you will still loose heat through the blocks webs. We had a block wall garage at work that was insulated in this fashion. Those outside vermiculite insulated walls were always freezing cold.


Sent from my tractor seat.

 

[AldeanFan]

Thanks for all the responses! 2 pages in a couple of days!

Since no one has said this is a bad idea I'll proceed as follows:

Phase 1 was installing the MrHeater furnace - its working great but i figure the payback of insulation will be worth while. I was toasty warm working on my '54 wagon last night but my warmth is definitely reflected on my gas bill.

Phase 2 will be insulating the outside of the garage with 2 inches of ridged foam and covered in vinyl siding (no more painting). I'll dig down along the walls where I can to extend below grade. Next winter I'll monitor my gas bills and see what kind of a difference it makes.

Phase 3 will be interior insulation. I may never make it to phase 3 if Phase 2 makes enough of a difference, or I may run out of projects an have to insulate just for something to do (unlikely!)

 

[NUTTSGT]

You have a good game plan but as Winter is upon us, you might want to switch #2 and #3 around as you can do the inside right now while the weather is crappy outside.

 

[David C]

JACdes et al

It appears I did not make myself very clear; I have not seen a hollow CMU wall in CA. I did not say I have never seen hollow individual CMU. In typical CMU construction all cells are grouted.

I realize that in some areas of the country CMU construction does not include any grouting, or does not include grouting in all of the cells. That is not the case here.

There is no procedure for calculating the structural capacity of completely hollow walls. There is a procedure for calculating partially grouted walls though this is typicaly not done and is precluded by code for schools, hospitals etc.

 

[4xdog]

Exterior insulation from companies like Dryvit, et al, is well known and widely applied technology.

 

[bazzateer]

I would also go with a decent infrared heater, but that's just me. I like to heat objects, not the air.

I couldn't get on with an IR heater. It only warms the bits it 'sees' so if you want a warm back your front gets cold. Much prefer to warm the air so everything is warm.

 

[reader2580]

How are you going to attach vinyl siding to a concrete block wall?

Part of my house uses foil sided foam insulation as sheathing. It adds insulation and also stops the thermal bridging from the 2x4s. My house is stick built, so much different from block walls. I have no idea how they nailed on the siding unless they just hit the studs.

 

[DC73]

Phase 3 will be interior insulation. I may never make it to phase 3 if Phase 2 makes enough of a difference, or I may run out of projects an have to insulate just for something to do (unlikely!)

Be careful with your proposed phase 3. You don't want to create a wall sandwich that contains and holds moisture. A wall has to be able to breathe to at least one side. Do yourself a favor and spend some time reading and educating yourself using the website I gave you in my previous post. There are right ways and wrong ways to insulate buildings and those ways can change depending on the climate. I live in a dry climate so I can get away with construction mistakes that those in a humid climate cannot afford to make.

Good luck.

DC

 

[AldeanFan]

How are you going to attach vinyl siding to a concrete block wall?

Part of my house uses foil sided foam insulation as sheathing. It adds insulation and also stops the thermal bridging from the 2x4s. My house is stick built, so much different from block walls. I have no idea how they nailed on the siding unless they just hit the studs.

I'm planning to glue the foam to the walls, then attach strapping over the foam with concrete screws through the foam in to the block, this will help hold the foam to the wall and will give me something to attach the siding to.

 

[AldeanFan]

Be careful with your proposed phase 3. You don't want to create a wall sandwich that contains and holds moisture. A wall has to be able to breathe to at least one side. Do yourself a favor and spend some time reading and educating yourself using the website I gave you in my previous post. There are right ways and wrong ways to insulate buildings and those ways can change depending on the climate. I live in a dry climate so I can get away with construction mistakes that those in a humid climate cannot afford to make.

Good luck.

DC

I'll effeminately do my homework before we proceed to phase 3 but I don't actually expect to make it that far, I think the outside insulation should be sufficient.

 

[kuhner]

My garage is block. I insulated it with 4" rigid foam baord and then we applied Dryvit over it.
I kept the 4" foam and Dryvit off the ground a couple inches, then placed a 2" pink foam from there to 36" below grade. I covered the 2" pink with Hardy board screwed through the the foam.
Pretty much the whole back wall of my garage is only out of the ground by two feet. I wish now I would have ran the pink foam all the way to the footer. I keep the garage at 60 and I now I am fighting the ground temps below the frost line.