Insulating un-vented garage attic

[rjacobs]

Building a new house. Optioned spray foam in the attic spaces, batt in the walls. I did not realize/wasnt told by the **** sales people, the attic space above the garage is not sprayed. They built "hot walls" between the house and the attic which are sprayed. So the garage is its own entity. I was told the separation is code... ok I can buy that, but why not spray the damn garage ceiling...

But I digress. I paid extra and had the garage walls insulated with batt. So I need to deal with the attic area. Since the rest of the house was spray foamed, the attic is un-vented everywhere. There is no way to do it cleanly due to how the roof lines run and I dont want to tear out soffit either.

Is my only option to have a spray foam contractor out and spray foam the attic above the garage?

Any way I can use rigid foam insulation either in between the ceiling joists or in between the roof joists? I dont think this will save me any money though over having the spray foam contractor come out and spray the attic roof.

I dont think, with no venting, having blown in or batt insulation laid in between the ceiling joists is a good idea. Same with putting batt insulation in between the roof joists.

Do I have any options besides more spray foam here?

 

[yeldogt]

Are you using the attic ... is it a bonus room?

Nothing stopes the heat like foam ... it's what I always use everywhere

 

[rjacobs]

Are you using the attic ... is it a bonus room?

Nothing stopes the heat like foam ... it's what I always use everywhere

no use of the attic although I may sheet some of the "floor" to use as storage.

I paid $500 to have the walls insulated because this builder finish dry walls and paints the garage interior. The only walls they insulate are the garage to house, so I had them do the rest.

Im thinking foam is my only real choice since the house was built with no venting due to the foam in the rest of it. I just didnt realize they werent going to foam the garage attic. It was a question that I never thought to ask when getting the price quote from the builder on "spray foam the attic". Figured that meant "spray foam the attic" not "spray foam the attic minus the garage". They wanted another 2500 to get the guy back out to spray the garage attic. I passed. I believe the sprayable area in the garage attic ceiling is between 800 and 1000 sq. ft... I am seeing prices of ~$1.50 sq. ft. for open cell so my guess is somewhere between 1200 and 1500 bucks to have it sprayed.

 

[yeldogt]

no use of the attic although I may sheet some of the "floor" to use as storage.

I paid $500 to have the walls insulated because this builder finish dry walls and paints the garage interior. The only walls they insulate are the garage to house, so I had them do the rest.

Im thinking foam is my only real choice since the house was built with no venting due to the foam in the rest of it. I just didnt realize they werent going to foam the garage attic. It was a question that I never thought to ask when getting the price quote from the builder on "spray foam the attic". Figured that meant "spray foam the attic" not "spray foam the attic minus the garage". They wanted another 2500 to get the guy back out to spray the garage attic. I passed. I believe the sprayable area in the garage attic ceiling is between 800 and 1000 sq. ft... I am seeing prices of ~$1.50 sq. ft. for open cell so my guess is somewhere between 1200 and 1500 bucks to have it sprayed.

You are up against the truck cost -- The whole setup cost is there regardless of if they work for 1hr or all day. Frankly ... 2500 sounds like a fair price if he did a good job on the other parts ... keep it all one guy. Even better if your contractor is getting him out for that price .. not your responsibility.

 

[jetnow1]

If it is a gable roof just put vents at each side, then insulate the ceiling joists. Foam is the best insulator but blown in between the joists seals pretty well also and is a lot cheaper. If you are heating or cooling the garage insulating the roof rafters will result in a lot of extra space to condition, I would think the smaller space from insulating the joists, plus the cost savings on installation would more than make up for the difference in insulation values.

 

[rjacobs]

Well they wanted me to pay in cash because it was past the time to make change orders by like 2 months. It was kind of bull **** since it wasnt explained to me that the garage ceiling wasnt being sprayed. Im basically out of cash to spend on this house since I am saving every penny for closing costs plus **** after closing(garage floor, ceiling fans, etc...) so its not at the top of my priority list. Might not do it for a year or two. My current garage isnt insulated at all except the garage door(I did that with rigid foam panels) and its not unbearable, BUT the attic is at least vented in this house. The new house comes with insulated doors already.

 

[rjacobs]

If it is a gable roof just put vents at each side, then insulate the ceiling joists.

Its not really. The 3 windows on the right side is what makes up the garage. Side entry, 3 car. It will be all bricked.

So the front above the double window would be the only place to vent the front, but its going to get bricked over and I am not tearing out bricks to vent the attic. The other side of the garage is a "hot wall" with the house, so again, nowhere to vent.

 

[strutaeng]

Its not really. The 3 windows on the right side is what makes up the garage. Side entry, 3 car. It will be all bricked.

So the front above the double window would be the only place to vent the front, but its going to get bricked over and I am not tearing out bricks to vent the attic. The other side of the garage is a "hot wall" with the house, so again, nowhere to vent.

Wait, are you conditioning the garage? The whole vented thing only becomes a requirement if space is going to get AC.

And yes, you can do non-vented attic as permitted by the Code. Greenbuilderadvisor website has good articles on this.

 

[rjacobs]

Wait, are you conditioning the garage? The whole vented thing only becomes a requirement if space is going to get AC.

And yes, you can do non-vented attic as permitted by the Code. Greenbuilderadvisor website has good articles on this.

Eventually yes, will be conditioned via a Mr. Cool DIY mini split.

And obviously a non-vented attic is permitted, the whole house is non-vented...

My question was pertaining to what insulation I needed to do as batt(or blown) insulation is obviously way cheaper vs. having the pro's back out to spray foam. But with no air flow through the attic, I dont think batt(or blown) insulation is ok since it will hold moisture.

 

[jonshonda]

Remember contractors are not going to go above and beyond to make your house as good as possible, they are going to go above and beyond to make money. From my very limited experience in researching home builders, if you want the good stuff and want it done the right way, good custom home builders are the way to go. Their initial bid might be high, but usually for good reason. They cover all the bases.

 

[rjacobs]

Remember contractors are not going to go above and beyond to make your house as good as possible, they are going to go above and beyond to make money. From my very limited experience in researching home builders, if you want the good stuff and want it done the right way, good custom home builders are the way to go. Their initial bid might be high, but usually for good reason. They cover all the bases.

Ive got no issue with the builder or how they are building... They do good work and the super for the neighborhood, from everything I can tell, runs a tight ship and has corrected every single issue I have found. Their sales people...dumb as that piece of warped OSB in my picture I posted... They dont know what they are selling when it comes to more custom stuff and everything took 2 weeks to get an answer, then it was a half answer, and another week to get the final answer. I passed on a few items because I never could get a detailed description of WHAT I was paying for... It bothered me that they could give me a price, but couldnt tell me what that bought me. And of course you dont get access to the people who can tell you so you rely on the sales people...who by the way ****. One of the 2 wont talk to me anymore LOL.

So basically AFTER they spray foamed was when I learned the garage roof was not included in that. Had I known that in October when I spec'd the spray foam roof in the house, I would have added the garage on because it all would have gotten rolled into the mortgage, but at this point, ill do it myself later on. It wasnt like they didnt know I wanted the whole garage insulted, so it might have been nice for them to mention it to me. but again, sales people who **** and all that. Im over it just trying to figure out my next move is all I am doing at this point.

 

[strutaeng]

Eventually yes, will be conditioned via a Mr. Cool DIY mini split.

And obviously a non-vented attic is permitted, the whole house is non-vented...

My question was pertaining to what insulation I needed to do as batt(or blown) insulation is obviously way cheaper vs. having the pro's back out to spray foam. But with no air flow through the attic, I dont think batt(or blown) insulation is ok since it will hold moisture.

You need to use air impermeable insulation such as XPS. It needs to be continuous (i.e., not cut and fitted between framing members.) Ideally, installed in 2 layers with joints staggered. Any penetration through the ceiling needs to sealed. Moisture from condensation is a result of air leakge.

 

[rjacobs]

You need to use air impermeable insulation such as XPS. It needs to be continuous (i.e., not cut and fitted between framing members.) Ideally, installed in 2 layers with joints staggered. Any penetration through the ceiling needs to sealed. Moisture from condensation is a result of air leakge.

The garage ceiling is probably roughly what the garage itself is so ~712 sq. ft. minus the joists.

4x8x4" sheets of XPS are 78 bucks. So I need at least 23 sheets, probably more due to waste. Thats $1800, at least. Thats R20.

I can get a 1400 board feet(1" thick) of closed cell DIY kit for $1400 and spray 2" and get R14.

I think once I close on the house I will have a spray foam company or 3 come out and bid the job and see where I end up.

I may also wait until I build my shop in 2 years or so and have them do it all at once. I dont know.

 

[HotrodHR]

Better go back and check you plans... I don't think your builder will be bricking up those "gable" ends, probably trimmed out with siding or shakes.

A vent on that end would help, but I think your over thinking this.

 

[rjacobs]

Better go back and check you plans... I don't think your builder will be bricking up those "gable" ends, probably trimmed out with siding or shakes.

its either bricked or stone work. There is no "siding" on this house at all.

The soffits are spaced for brick to go up into them, but it could be stone work.