Insulation help for my garage with pics

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If your garage is heated, think about using a ceiling fan to pull heat down from the peak. You'd be surprised at the temperature differential with uncirculated air under cathedral ceilings. There is also more heat transfer through a material as the temperature differential increases.

If it is 70 degrees at floor level and 100 degrees at the peak, you would be fighting to maintain 70 degrees for comfort while the roof is bleeding heat. If you mix the air constantly, the peak temperature will be closer to ground-level temperature, say 70 degrees and there would be less energy transfer if it was still 100 degrees up there.
 
Hey Steve, I know we're going to talk later about something else, we can talk about your garage too. I have a lot of background in this area, about 35 years worth of contractor, building inspector, and lumber yard owner.
 
I saw the foam insulation in a house they are building up the road from me and thought man that would be great. When I asked how much to do his house and he told me $13,000 to spray his house it changed my mind quick. It looked like the Great Stuff that you get in a can to spray around windows and doors. Could buy lots of cans for that amount of money. I will keep watching to help me decide what to do in mine,Joe
 
4spdragtop said:
Wouldnt that create condensation between the foam and the roof sheeting though?? Is there not supposed to be an air gap??
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That type of insulation pretty much creates a sealed volume. I've seen some of these "exposed beam" or log homes where the "sheeting" is decorative paneling with the beams below. The insulation is a sandwich made of some sort of board, as in plywood, one on top, one below, and foam in between.

The secret is vapor barrier. The reason you need soffit and attic vents on a building with a ceiling, is that most insulation leaks enough heat that it can allow snow/ ice to melt where the warm corner of the wall/ rafters meets, melts in that area, runs down to the edge of the roof and re-freezes because it's now colder. Makes ice dam, backs up water, gets under the roof and causes water damage.

In your case you have the opposite problem. You need to seal the rafter cavities to keep building moisture out of the insulation

I used to do HVAC service. We had an RV park with a large indoor pool room. An exhaust fan in part of the building was building negative pressure in the building, causing some gas fired heaters to "not vent", IE was sucking the vent gases backwards down the vent and out into the building. I checked around for other units, and found the pool utility room full of vent products from the three pool boilers. Still looking for problems/ solutions, I took a look in the huge attic space above the pool.

1 An incorrect vapor barrier of plastic had been laid on top of the ceiling

2 I could find NO evidence of effective attic ventilation

3 The rafters had been insulated with paper backed fiberglass batting. The 100% relative humidity in the attic had eventually worked it's way through the paper backing, and SATURATED the fiberglass. You could see glass bats had ripped completely off and fallen, others were hanging down and DRIPPING WATER

I told the manager that if he didn't do something with this, he wouldn't have a building to worry about. Soon after that, I left this job to work for Motorola, so I never found out what they did with the problem.
 
Thanks 67dart273....from my limited knowledge this is my take on it.
It needs a gap between the sheeting and the insulation. This gap is for cold air/ventilation to keep condensation from building up on the sheeting and the insulation. In order for the gap to work properly it also has to be vented to allow that air in the gap to breather. In order for it to breathe soffits are usually vented to help allow this. Problem is my soffits arent vented, so I have to look at what I can do to vent the soffits to allow the "gap" to breathe.
 
Actually it does not need a gap between the sheeting and the insulation. It needs a vapor barrier between the sheeting and the insulation.

What happens is that due to heat/cold variation on each side, somewhere in the middle of the insulation the temperature/moisture will be at the dew point. With fibreglass or Roxul insulation, this is where the moisure occurs. The vapor barrier simply protects the moisture from travelling inward and damaging the sheeting. Instead the moisture will wick out the "cold" side as the temperature varies. The venting on the cold side simply allows the excessive moisture buildup to escape from the insulation to outside as opposed to steaming up your rafters (or keeping your insulation wet).

The spray foam is designed to fill in the rafters. It also acts as a vapor barrier, and is designed to not entrap moisture. There is no need for venting in this method, as there is really no moisture build up in the material to evaporate.

You can insulte rafters with roxul or something similar, but you would have more trouble to seal around the vertical boards of the truss, and would have to leave an air gap of a couple of inches between the insulation and the roof sheeting. This small area would have to be vented.

Grant
 
Spray foam works well if you understand the process. It becomes the vapor barrier, because it is closed cell, and bonds to the underside if the decking & supporting structure.

Properly applied, it will prevent ice dams, because the deck stays cold. Much easier to have a little gap develop in other types of insulation & cause a hot spot on a roof.

Two part spray in foam can be a DIY project. It is not anything like spray can foam, and requires some planning. It sets up in seconds once sprayed, and it is easy to spray deeper than you had planned.

It runs about 1 USD per board foot for DIY: http://tigerfoam.com/

That is E84 fire rated material, and is ok in lots of spaces. If your local building codes require it, there is a flameproof coating available to spray over the finished foam.

A 500 square foot garage is a reasonable DIY job. You need to do all of the work like penetrations, wiring etc first. I prefer to not put electrical under the foam unless it is in conduit for later service. Then you need to empty the garage, and mask the place from the underside of the rafters down. Plastic sheet, cardboard & a staple gun. Cover the floor. This stuff sticks to anything, and you are not putting it in with an airbrush...

Properly sealed up, the roof deck stays dry. Don't believe the rumors that it shortens roof life - plenty of homes here in the desert have the sprayed decks with great roof life at high temps. It is amazing to climb into an attic, and see bare sheetrock on the rafters - then you realize the attic is almost as comfortable as the rest of the house, and the HVAC equipment is running in a clean cool space. A 10 year old house with a foamed deck usually looks like they vacuum & dust the attic inside.

I would foam it in that climate. My home in Colorado was foamed, and it would have snow on the roof a week after a storm, while the neighbors roofs were clear. I could just see the heating dollars melting that snow.

B.
 
Stay away from the foam Steve!!

I priced the proper "blue" foam for my shop.....holy cow!! that stuff is exspensive up here. I chose fiberglass bats, as these were the most economical for my, and your application.

bohica2xo is right on the money though with His post. It just wasn't very economical up here
 
4spdragtop said:
I was thinking of insulating the actual angled part of the trusses instead of the flat horizontal 2 by's. I have been told if I put insulation up tight to the plywood sheathing condensation will build up and rot the boards.
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[ame="http://www.youtube.com/watch?v=5DX25Vz2jDc"]insulate roof foam baffles ventilation - YouTube[/ame]

They also make these, simply staple in place and then install your insulation.

http://www.jrproductsinc.com/shop/pc/Cardboard-Attic-Baffles-24-x-33--50-per-bundle-288p201.htm

You can install some vents on the soffit for air flow.
 
Badsport said:
insulate roof foam baffles ventilation - YouTube

They also make these, simply staple in place and then install your insulation.

http://www.jrproductsinc.com/shop/pc/Cardboard-Attic-Baffles-24-x-33--50-per-bundle-288p201.htm

You can install some vents on the soffit for air flow.
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I tried using those in the house, what a pain in the arse on a retrofit!! F'n roofing nails in the back, neck, skull!! On a new build for sure, or in the garage, but I gotta do a test hole on the soffit and see whats underneath the soffit first. Its gonna have to wait till spring as my rafters are like my bowels....LOADED!!
 
4spdragtop said:
I tried using those in the house, what a pain in the arse on a retrofit!! F'n roofing nails in the back, neck, skull!! On a new build for sure, or in the garage, but I gotta do a test hole on the soffit and see whats underneath the soffit first. Its gonna have to wait till spring as my rafters are like my bowels....LOADED!!
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Are you speaking of the cardboard baffles or soffit vent? As far as the baffles go, you could pick up some cardboard sheets and make your own, just score one side of the cardboard with a razor knife and bend it where you need to.

As far as venting the soffit, these would probably do the trick, you would only need three or four on each side.

http://www.homedepot.com/webapp/wcs...ooglebase-_-D26X-_-202907299&locStoreNum=2757
 
If you are putting the insulation against the underside of the rafters you will need a soffit vent for each rafter cavity because the air would not be able to circulate in the rafter spaces with out them.
 
If I use the speedi vents in the soffit, I will use the duravent/moorevent, fglass pink and vapor barrier, but then I have to put a ridge cap on the top to allow the air to flow. No easy/cheap/quick fix for this!
 
Spray foam. No nails in the head, vapor barrier ridge vents etc.

Wait for spring & empty the garage. 500 square feet? Take a couple of hours.

see my previous post.

B.
 
bohica2xo said:
Spray foam. No nails in the head, vapor barrier ridge vents etc.

Wait for spring & empty the garage. 500 square feet? Take a couple of hours.

see my previous post.

B.
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Thanks B, I may consider that! Whatever happens its gonna have to wait till spring.
Thanks
Steve
 
Well, giving this a bump, Im off for 3 days so Im thinking of tackling this project....fall/winter aint far off!!
 
Have you ever considered spray foam? You can buy kits to do it your self or leave it to the pros. Either way you get 100% coverage and do not need a vapour barrier.
 
Giver Steve! Vapour barrier your ceiling, board it,and then call a blow-in company.Shouldn't be more than five bills! well worth it.Don't forget to leave a hatch!
 
CRAIG COX said:
Giver Steve! Vapour barrier your ceiling, board it,and then call a blow-in company.Shouldn't be more than five bills! well worth it.Don't forget to leave a hatch!
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Hey Craig, I wont fit thru a frickin hatch!! LOL. Im insulating the top chord(angled part of truss) Sucks as I have to cut part of the roof cap off to do this properly!
 
Here is the inside of my shop, its close cell spray on. It complete seals out any cracks or crevices, I had my whole shop sprayed. It is not cheap but when all the doors are closed it is as dark as Carlsbad Cavern inside. The shop will be a good 20 degrees cooler in 100+ degree Oklahoma summer day. But, after its sprayed you will have to go outside and grind off the insulation that squeezes thru, you will be amazed at the places it finds...
 

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hey Steve none of these other experts saw is that you don't actually have a soffit , you have covered tails so to speak which means as Nuttyprof pointed out that you need to vent each rafter bay , I would recommend installing a proper box soffit with venting every 4 feet or so and making sure they didn't block the bay spaces on the top plate , then there are a number of products available for creating the air space in the rafter bay but for rigid foil board you can just nail it to the surface of the rafters and tape the seams just don`t butt the 2 sides at the top leave both sides a couple of inches short at the top and then vent your gables ( which you should do in any case ) if you decide you want a little more you can always bridge the 2 sides with a wide enough strip of rigid using good old Tuck tape just do it below the gable vents .
 
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