Spray foam insulation under roof decking

[yeldogt]

Closed cell is impermeable to water so in situation where it is used for the roof deck (rafters) and the roof sustains a leak, what would happen? The water will not show up on the underside of the roof/ceiling and will keep getting trapped on the surface of the foam (facing out) resulting in moisture/mold and rotting up the wood etc .

What is recommended is to use open for the roof so that you can spot a leak/fix it rather than hiding and not facing the fact that you have a roof leak.

Hope that helps.

Most roofs leak a tiny bit as they age -- the wind whips the water around - they dry out. Same if the foam is under it.

Most leaks are caused by bad installations -- ice dams - ridge vents -- condensation -- freezing heaters in unconditioned space. Spray foam eliminates most issues.

I always use plywood on roof decks.

 

[mpire]

I am building a new home in Florida.
I had icynene foam sprayed above the residential area as well as above the detached garage. My HVAC isn't running yet but I can already feel the difference. On a hot day it is easily 10 to 15 degrees cooler than before they sprayed.

I sure wish someone could break it down for what I would need in Orlando. I find that everyone is so concerned about snow and ice that none of the designs apply to me or my climate.

I was going to blast in a bunch of cellulose this summer. Not sure if that helps or not. Also, I am not sure about venting my attics here over my garage or if I can just blow in cellulose. I did put in bat insulation on the ceiling and then put in wood planks on the crawl space for storage. My attic garage is vented on the soffits but no vent on the peak. That's probably not good, right?

I can feel the cold spots in my attic at the tops of the walls, so I know its not very efficient up there after 15 years.

 

[volleyball]

Best to call a few installers and ask them what you need. The more you seal the envelope, the better the job.

 

[TheBadDog]

It's a bit daunting. Web resources don't all agree, but much of that is due to regional differences, but there is concern about it being due to their investment in a technology.

So I've talked to every local resource I can find, other than a few with some seemingly shady operations. And THEY are all over the map. One says closed cell, most say open cell, some will do closed on request at 2-3 times the cost. But I'm also hearing from one that it MUST have external venting mechanism to prevent "stale" inside air. Everyone else says "seal it up tight", and I'm not too inclined to inject exterior air that can be 115+ ambient in the summer. That's the whole point of this exercise to avoid that. And I've had 2 refuse to quote because I won't pull the ceilings in the entire house. And one that's requiring that I also pay to install one of their approved attic doors claiming safety code, but nobody else has said a word.

For general point of reference, cost is generally in the $5-7k range for open cell (one outlier at almost $10k!) with them removing ~20" of blown fiber. And that's a 2800 sq ft with 260 sq ft vaulted (me dropping sheet rock), and a 100 sq ft "atrium" (aka attic piercing vertical tunnel with sky lights). They also have to finish sealing off gable vents and one power roof vent, this house has no eve venting, and sealing the partial divider wall with the garage. I'm asking for a rider on the quote for an option to also do the 2.5 car garage at the same time (but will not be part of climate controlled space, and so must remain vented), depending on budget/cost.

 

[C2 Turbo]

If the house is foamed, you definitely need some sort of fresh air entry into the house.

Opening up the windows and or whole house fans could either bring in cold or hot and humid air for which your HVAC system would have to work harder to over come thus costing more money.

We are getting Geothermal in our project and I went with ERV system in which the fresh air goes thru an exchanger/filter before getting into the house. The new air is already at the right temp thus it doesn't effect the HVAC performance not to mention it filters out the dust/pollens etc.

http://www.ervsystems.com/

Hope that helps

 

[yeldogt]

It's a bit daunting. Web resources don't all agree, but much of that is due to regional differences, but there is concern about it being due to their investment in a technology.

So I've talked to every local resource I can find, other than a few with some seemingly shady operations. And THEY are all over the map. One says closed cell, most say open cell, some will do closed on request at 2-3 times the cost. But I'm also hearing from one that it MUST have external venting mechanism to prevent "stale" inside air. Everyone else says "seal it up tight", and I'm not too inclined to inject exterior air that can be 115+ ambient in the summer. That's the whole point of this exercise to avoid that. And I've had 2 refuse to quote because I won't pull the ceilings in the entire house. And one that's requiring that I also pay to install one of their approved attic doors claiming safety code, but nobody else has said a word.

For general point of reference, cost is generally in the $5-7k range for open cell (one outlier at almost $10k!) with them removing ~20" of blown fiber. And that's a 2800 sq ft with 260 sq ft vaulted (me dropping sheet rock), and a 100 sq ft "atrium" (aka attic piercing vertical tunnel with sky lights). They also have to finish sealing off gable vents and one power roof vent, this house has no eve venting, and sealing the partial divider wall with the garage. I'm asking for a rider on the quote for an option to also do the 2.5 car garage at the same time (but will not be part of climate controlled space, and so must remain vented), depending on budget/cost.

Don't confuse a ventilated attic and the need to "ventilate" a house IE .. fresh air.

Old houses leak .. they naturally ventilate . Spray foam houses don't leak air -- so one needs to introduce fresh air to the house. By controlling this change you are minimizing the loss. How you go about adding/ changing the air in the house has much to do with your climate and the number of people. I'm in the mid-atlantic ..So have to be concerned about humid air. In my case I use a system that also incorporates a dehumidifier .. and I like a bit of positive pressure in the house (radon area). It sound complicated .. but all the equipment is available.

Personally, If going to the trouble I would always used closed foam.

 

[TractorJeff]

I have a tin roof over shingles and wood shingles. If I ever get the roof stripped down to just having tin, then I want to spray foam the "attic" space. To put bedrooms up there with heat and ac.
Following this info I should be able to close cell after I am to a tin roof only?

 

[DC73]

Don't confuse a ventilated attic and the need to "ventilate" a house IE .. fresh air.

Old houses leak .. they naturally ventilate . Spray foam houses don't leak air -- so one needs to introduce fresh air to the house.

Agreed. You actually want a house so tight that you have no choice but to install a source for fresh air. That way, you get to decide how much fresh air you bring in, where that fresh air comes from, and you can filter the incoming fresh air. A leaky house brings in fresh air through all of the various cracks and crevices that contain dead bugs, mice, dust, mold, etc.

DC

 

[volleyball]

Before you think of reintroducing ventilation, you need to do an energy audit and see how tight your place is.
An ERV can help if you removed most of the leaks but that is hard with a building not built that way.

 

[C2 Turbo]

Some interesting read



Merits of Spray Foam Insulation:

http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/weighing-merits-spray-foam-insulation

Open Cell in an Attic:

http://www.greenbuildingadvisor.com...ce/does-open-cell-spray-foam-really-rot-roofs

Ventilation (HRV vs ERV)

http://www.greenbuildingadvisor.com...ilding-blog/breathe-easy-balanced-ventilation

Spray Foam and the need for Mechanical ventilation:

http://www.greenbuildingadvisor.com...e/spray-foam-insulated-homes-need-ventilation

 

[TheBadDog]

I'm not sure how it may figure in, but I've already had the walls filled with expanding open cell foam. I was amazed where all that stuff came out. Some parts of the walls, and around outlets, it looked like the back side of a cheese grader. And I've upgraded the remaining old single pane windows. Eventually I'll replace the cheap "builder grade" double panes the PO installed in most of the house. Other than that, the only places of significant concern are the doors, particularly the HUGE cheaply made sliding glass door on the N wall (to the pool), and the old hand carved solid hardwood double front door. No idea if that will ever be "too sealed" or not, but I suspect those leaks combined with our comings and goings along with the dog door (with 3 dogs coming and going) will provide enough air exchange. But have no idea how to measure such things. And the nearest ERV rep is in MO, so not much help. Most of my quotes don't seem to think it will be an issue in a 70's retrofit like mine.

 

[volleyball]

You want someone that can do a blower door test. They will tell you how quickly the air exchanges.
One thing to note is what you may have offgassing. Products, pets and humans. You will need to be able to replace air vented out through your exhaust fans.

 

[TheBadDog]

Thanks, I'll check with the local insulation folks and see if they can do it, or know of someone. I assume that is something that would be done after the attic is blown. We have single digit humidity here much of the year, so bathroom exhaust fans don't get much use for humidity dissipation. Sometimes the towel is almost dry by the time you get done shaving etc. But there is the stove lid and other exhaust fan uses.

I've also thought about other angles on this topic. For instance, right now the days are hot (Sun was 98 on the mercury here) but the nights are fantastic. I've been using some otherwise defunct swamp coolers (cleaned and use the AC vents) to move cool outside air through at night and really liked it. It would be really nice to replace that with a filtered system for use when temps support it, or when as suggested, exhausted or stale air needs replacement. Again, I don't really know what I don't know, but with the exception of one contractor nobody out here seems concerned about over sealing on a retro foam installation. But just like the foam project not being JUST about insulation quality (ease of access for reno and repair are a big part of justifying cost), if a fresh air system isn't too be a budget buster, it would certainly be a good thing to investigate. Thanks for focusing my attention on something I had all but ignored.

 

[Signal10]

Spray foaming the roof deck of a home is a great idea if you can make the initial investment. I just finished building my ICF home and we sprayed the roof deck with open cell spray foam. I had my HVAC system designed by EnergyWise Structues and we moved in December 23 last year. The highest utility bill we had was 52.00 for the month of January. The house is a 3800 sq ft build so I'm very pleased. The biggest thing I learned in trying to build an energy efficent home is that your house does not "need to breath". Your house doesn't have lungs so it doesn't need to breath. The home does need to have air exchange and that's for air quality. A conventional quality stick built house to code in my area will loose its total volume of air in approximately 1 hours time. So that air you just paid to heat or cool is all gone in an hour. Ouch! We have a HVAC system that brings in fresh air when the humidity level rises to high and also a co2 sensor that calls for fresh air. What I've noticed is approximately every 4-5 hours the system will come on and bring in fresh air for a few seconds. The cost of my spray foam was 3 times what I could have done cellulose for and really debated the expense. However after seeing my utility bills I feel the cost recovery will be very soon. I have a ton of information on this type of construction. Let me know if I can help. Here's a link to my blog although I still haven't updated the blog in a while.
DIY ICF
diyicf.blogspot.com/

 

[C2 Turbo]

My understanding is, with open foaming the roof deck, the attic space needs to be conditioned and the humidity level (especially of the attic space) needs to be under 50%.

 

[yeldogt]

My understanding is, with open foaming the roof deck, the attic space needs to be conditioned and the humidity level (especially of the attic space) needs to be under 50%.

The open cell industry normally says that at 5 inches the foam is a vapor barrier ... but people still have issues at that thickness. I have read studies about how thick open needs to be for air intrusion --- industry says a bit less then 5 .. but again the blower door tests on the open shown more leaking.

In a hot dry climate open vs batts I think is a fair/ reasonable discussion. I also think that open can make a case for itself when building new with all of the safety systems in place.

Personally, for me it is not an option. For old building with limited insulation space -- even new 2x6 construction walls -- the closed is the way to go. You can do things with closed foam that nothing else can do.

This is a picture of of my rebuild -- that foamed wall was prior rebuild. With closed foam you can insulate an old stone wall (it is coated on three sides) -- nothing else can do that.

Edit: Can you rotate picture after upload?

 

[volleyball]

My understanding is, with open foaming the roof deck, the attic space needs to be conditioned and the humidity level (especially of the attic space) needs to be under 50%.

The attic is automatically conditioned as it is not insulated from the living space. And it doesn't have to be the same temp as the living space. Just not the same as outdoors.
A conditioned attic makes a lot of sense if there is ductwork up there. I see people spend tons of money on tightening up there home and basically run the ductwork outside while it is carrying the expensive heated/cooled air to the living space.

 

[yeldogt]

The attic is automatically conditioned as it is not insulated from the living space. And it doesn't have to be the same temp as the living space. Just not the same as outdoors.
A conditioned attic makes a lot of sense if there is ductwork up there. I see people spend tons of money on tightening up there home and basically run the ductwork outside while it is carrying the expensive heated/cooled air to the living space.

You can get high humidly in a sealed house without proper ventilation -- with closed cell the danger of too little insulation would be condensation on the bottom of the foam -- with open it will form on the roof deck. This can happen if the open foam is thick. With enough closed foam this is not an issue.

 

[volleyball]

Humidity will be the same inside and out.
Now if you lower the temp, you will get condensation which is a problem.

 

[DC73]

The open cell industry normally says that at 5 inches the foam is a vapor barrier ... but people still have issues at that thickness. I have read studies about how thick open needs to be for air intrusion --- industry says a bit less then 5 .. but again the blower door tests on the open shown more leaking.

In a hot dry climate open vs batts I think is a fair/ reasonable discussion. I also think that open can make a case for itself when building new with all of the safety systems in place.

Personally, for me it is not an option. For old building with limited insulation space -- even new 2x6 construction walls -- the closed is the way to go. You can do things with closed foam that nothing else can do.

It's also possible to spray closed cell in a limited amount and then after it cures, finish the job with open cell. Not all climates have this option. Some have no choice but to use closed cell.

DC

 

[justanengineer]

Closed cell is impermeable to water so in situation where it is used for the roof deck (rafters) and the roof sustains a leak, what would happen? The water will not show up on the underside of the roof/ceiling and will keep getting trapped on the surface of the foam (facing out) resulting in moisture/mold and rotting up the wood etc .

What is recommended is to use open for the roof so that you can spot a leak/fix it rather than hiding and not facing the fact that you have a roof leak.

My last rental had open cell on the roof decking and was a good lesson regarding leaks and spray foam that plumbers learned centuries ago, **** flows downhill. Long story hopefully short, neither open nor closed cell foam seals as tightly to roof decking as the spray foam propaganda would have you believe nor do they really help with waterproofing. Over time the foam separates slightly which creates a nifty little channel for water to flow, and once saturated open cell acts much the same as closed cell - it sheds water downhill. Here in Indiana much of the winter, spring, and fall are gray rainy days with extremely high winds and heavy downpours/flooding/etc are fairly common which can saturate open cell like ours over a day or two. During the 5 months we were doing an initial renovation after buying our current home, we continued to rent and noticed an occasional funky smell. The town stinks of corn syrup production (ie. rotten dog ****) so we didnt think much of it until the landlord found mold in one wall floor-ceiling up through two stories after we'd moved which prompted quite a conversation about liability and what I did/didnt do there. JMO but I'd never buy a house that had the decking foamed. Possibly the ceiling, but not the decking.

 

[volleyball]

You cannot get closed cell to separate from the surface it is sprayed against. Now if it was covered with dirt, the foam is still stuck to the dirt and the dirt separated from the deck.
A poor foam could disintegrate early if the mix wasn't at the right temp, poor quality or some exterior force working on it.
You do show how the misguided thought to use open cell on the roof deck is. It sounds good so many believe it.
We run into this when any new product gets widespread use without proper training.

 

[C2 Turbo]

So what happens if there's a roof leak with closed foam decking? What happens to the water leaking thru the exterior sheathing?

Isn't it good to have the roof deck foamed (open) and not dry walled, where you can go up periodically and check for any leaks?

 

[volleyball]

So what happens if there's a roof leak with closed foam decking? What happens to the water leaking thru the exterior sheathing?

Isn't it good to have the roof deck foamed (open) and not dry walled, where you can go up periodically and check for any leaks?

I addressed this when you asked this earlier in this thread. And you cannot have living space with foam showing. So it isn't.

 

[Beemer533]

..neither open nor closed cell foam seals as tightly to roof decking as the spray foam propaganda would have you believe nor do they really help with waterproofing. Over time the foam separates slightly which creates a nifty little channel for water to flow, and once saturated open cell acts much the same as closed cell - it sheds water downhill. .....

If you are/were expecting spray foam, in this application to help with water proofing, you were badly mis-informed. Spraying the roof deck (with open or closed) has absolutely nothing to do with waterproofing anything.

Open cell foam can shrink as it dries, which can be one reason why it separated.

 

[C2 Turbo]

I addressed this when you asked this earlier in this thread. And you cannot have living space with foam showing. So it isn't.

Of-course the selection of open vs close is geographically dependent/chosen but in my application (KY), the weather is really not that extreme. We have few weeks of snowing, so icing also is really not much of an issue.

Also our attic will be conditioned (same temp as the rest of the house) and the duct work will be in there too, so humidity will not be a factor unlike most cases.

I just checked with my Insulator and yes we will not be sheet rocking the roof deck for the fact, we want to spot any trouble as soon as it arises and also with 8-10" of foaming, not much room to attach the dry wall to the studs

Not sure if that makes any sense or not but regardless, we just can't afford 6" of Closed ($$$$) or fiberglass batts (inefficient) so we are only left with open choice.

Also I don't know what the technicality is, but the weakest point of Open is it's ability to let moisture/water go thru and if you can spot the trouble (wet/spongy/separating foam) then what's wrong with that?

 

[Chris705]

C2 - as you describe how you intend to use open cell foam and you will be conditioning the attic so humidity getting thru the open cell foam won't be an issue. "What's wrong with that is this..... From what I have read about foam and being very much into weatherization and how best to air seal using foam spray is that open cell foam allows water vapor to pass thru it and at some point it will reach the dew point temperature within the foam. Now as you say you intend to condition your space but I believe there are always nice times of the year when doors and windows are left wide open. It seems to me you run the risk of allowing that moisture in the air to get in the open foam and condense within it (once the weather cools). That is why I believe the practice of "flash and batt" exists. Spray 2-3" of closed foam to air seal and bring that dew point location inside of the foam layer so it will never conceivably condense. The cheaper batt application allows you to get the equivalent R-value you would have gotten from the full 6" of open foam. We are geographically apart but I have to believe you will have humidity problems in the winter. When notherners heat we tend to have to add humidity into our heated homes for comfort reasons. Showering and cooking also add humidity to our homes, I doubt you will be running a dehumidifier in the winter months, so humid air will work its way thru open foam and condenser either within the foam or on the roof sheathing. Truly concerned that open cell is not the right choice. Now if we where only talking about "If my roof started to leak and wouldn't I want to know where/if it was leaking" then yes open foam might be a choice given I'd like to know and possibly locate said leak. This is a good thread, I like hearing what everyone has to say and I am hoping this rough winter goes away and I can get quotes to spray 3" of closed foam in my garage build roof and 2" on the sidewalls....

 

[justanengineer]

You cannot get closed cell to separate from the surface it is sprayed against. Now if it was covered with dirt, the foam is still stuck to the dirt and the dirt separated from the deck.
A poor foam could disintegrate early if the mix wasn't at the right temp, poor quality or some exterior force working on it.
You do show how the misguided thought to use open cell on the roof deck is. It sounds good so many believe it.
We run into this when any new product gets widespread use without proper training.

My limited experience has been that closed cell separates as well as open cell. When I still lived in Northern NY the local roofers regularly peeled roof decking off of foam fairly easily leaving the foam intact bc it sticks more to the trusses and itself than the actual sheathing. As for choosing open vs closed cell I wouldnt call it a misguided thought, its a matter of the differences in climate. In warmer states the humidity becomes rather high during summer so open cell is often used to allow the house to breathe, otherwise you can get mold and rot from the trapped moisture generated by the house rising up into an attic. In colder states closed cell is used simply bc there are far fewer humidity issues so closed cell is preferred. Not sure what youre referring to as a new product, spray foam's only been in common use for what, 20 years that Ive noticed? Probably goes at least a decade or two prior to that. Heck, when I started watching the various home reno shows back ~Y2k it was already common on them.

 

[justanengineer]

If you are/were expecting spray foam, in this application to help with water proofing, you were badly mis-informed. Spraying the roof deck (with open or closed) has absolutely nothing to do with waterproofing anything.

Thanks, I knew better but thats some of the propaganda Ive read along with similarly comical claims about it greatly strengthening the roof itself. I was never in the attic space of the rental that had the mold issue, I heard about it third hand between a grumpy landlord and the roofing/sheeting/siding crew that did some of the tearout and rework on the house prior/after the mold remediation. I actually liked their work enough that I hired them to replace the roof on the house I bought.

 

[8mpg]

There is some good info here and some bad. Im not an expert but have done a ton of research and live here in Texas where the climate is similar to Arizona. Most of the articles and what not you read online are going to be for houses up north where you worry about not enough insulation causing vapor issues. This is not the case in Texas or Arizona. Houses in the south do fine with open cell.

I just did a gut/remodel on my 1963 2100sqft ranch. After a TON of research, I decided on 7" of open cell spray foam with a completely sealed attic. Gables are spray foamed, spray foam down in the eaves. Only plumbing extrusions in the roof, nothing else. My attic is consistently 5-10* warmer than the inside of my house. The a/c ducting is in a "semi conditioned" space. All the ducting is mastic sealed at the connections. I did not worry about an ERV to pull in air because this house will still leak enough air with the sealed attic.





I highly suggest you check out Matt Risinger (builder in Austin) website and youtube channel. You will learn more than enough through him. He is one of the very few people who is dedicated to building science in the south.
Youtube playlist of his on insulation:

 

[volleyball]

When you spray with closed cell, the max depth is 2" per pass so spraying 2" over 1" isn't double cost wise technically. Maybe an installer will price it that way but they are doing a disservice.
Since you do an envelope meaning everything gets covered, you technically don't need the same depth. I went with 2 passes, 4" in NY and it is working great. You don't need 6".
Hi density spray may have been in existence for awhile but hasn't been readily available which translate into it being new. New to you and me. And cost is the only thing that is keeping it from being more common. Stone counter tops have been around for thousands of years but it has been relatively recent that people had them and more recently they are commonplace. Foam would be common today if people put their money into what helps them over what is bling. Granite counter tops look nice and impress others more than foam but there is little benefit otherwise to have them.

 

[8mpg]

When you spray with closed cell, the max depth is 2" per pass so spraying 2" over 1" isn't double cost wise technically. Maybe an installer will price it that way but they are doing a disservice.
Since you do an envelope meaning everything gets covered, you technically don't need the same depth. I went with 2 passes, 4" in NY and it is working great. You don't need 6".
Hi density spray may have been in existence for awhile but hasn't been readily available which translate into it being new. New to you and me. And cost is the only thing that is keeping it from being more common. Stone counter tops have been around for thousands of years but it has been relatively recent that people had them and more recently they are commonplace. Foam would be common today if people put their money into what helps them over what is bling. Granite counter tops look nice and impress others more than foam but there is little benefit otherwise to have them.

Is that to code? I think you guys need something crazy like r38

 

[DC73]

I highly suggest you check out Matt Risinger (builder in Austin) website and youtube channel. You will learn more than enough through him. He is one of the very few people who is dedicated to building science in the south. https://www.youtube.com/watch?v=NOQJHZJdLxA&list=PL8AF2A9643FBAA21A

Matt knows his stuff but his expertise is primarily Hot/Humid climates like found in east Texas. Out here in West Texas, it can be very dry at times. A couple of days ago we had humidity levels in the single digits while Austin was around 65%.

DC

 

[PT Doc]

Spray foaming the roof deck of a home is a great idea if you can make the initial investment. I just finished building my ICF home and we sprayed the roof deck with open cell spray foam. I had my HVAC system designed by EnergyWise Structues and we moved in December 23 last year. The highest utility bill we had was 52.00 for the month of January. The house is a 3800 sq ft build so I'm very pleased. The biggest thing I learned in trying to build an energy efficent home is that your house does not "need to breath". Your house doesn't have lungs so it doesn't need to breath. The home does need to have air exchange and that's for air quality. A conventional quality stick built house to code in my area will loose its total volume of air in approximately 1 hours time. So that air you just paid to heat or cool is all gone in an hour. Ouch! We have a HVAC system that brings in fresh air when the humidity level rises to high and also a co2 sensor that calls for fresh air. What I've noticed is approximately every 4-5 hours the system will come on and bring in fresh air for a few seconds. The cost of my spray foam was 3 times what I could have done cellulose for and really debated the expense. However after seeing my utility bills I feel the cost recovery will be very soon. I have a ton of information on this type of construction. Let me know if I can help. Here's a link to my blog although I still haven't updated the blog in a while.
DIY ICF
diyicf.blogspot.com/

34,200 cubic ft per air loss from an average home per hour. That sounds almost unbelievable. I do agree with bringing in fresh air but your own terms.

 

[8mpg]

Matt knows his stuff but his expertise is primarily Hot/Humid climates like found in east Texas. Out here in West Texas, it can be very dry at times. A couple of days ago we had humidity levels in the single digits while Austin was around 65%.

DC

Right... the only difference in dehumidifying the air. In AZ, he may need to humidify. Insulation principals are the same.

 

[DC73]

Right... the only difference in dehumidifying the air. In AZ, he may need to humidify. Insulation principals are the same.

There are more differences than just humidity. My area and other parts of the arid southwest is known as a mixed-dry climate which means we get cold as well. Because of the low humidity, we don't have vapor control issues. It's common practice to duct bath exhaust fans directly into the attic instead of out through the roof (not smart if your attic isn't well ventilated but works well otherwise).

Joe Lstiburek of Building Science Corporation writes builders guides for each climate area of the U.S. He thought enough of the differences to write a separate guide for Mixed-Dry climates. His Builders Guide books are well worth the price and I highly recommend everyone pick up the one for your specific climate.

http://www.buildingsciencepress.com/Builders-Guides-C1.aspx

DC

 

[volleyball]

Location, location,location. It makes a world of difference for most projects. That is why when someone makes a new thread and wants details about how to do something and we don't know where they live, we have to ask, or not reply.
What works in one place fails elsewhere. We cannot build the same home anywhere in this country. Well not exactly the same. Some stuff is the same.

 

[TheBadDog]

I'm learning a LOT from this thread, and still processing. Thanks, and looking forward to whatever more may come. I've got most of my quotes, hoping to wrap that up first of the week and make a choice to move forward.

 

[Beemer533]

Well, I had my quote today, 4" of closed cell for the roof and 3" for the gable ends ;that came to $3900. I also had them quote my garage roof (22x22 flat roof) with 2" and he quoted an additional $950 for that.

He did say that there is no reason to have vents with the closed cell.. I will probably bite the bullet and get it done this year.

 

[TheBadDog]

Wow, cheapest quote I've gotten so far is ~$5k for 6"+ open cell. That's ~2700 sq ft (flat, not counting pitch) with some minor plywood sealing of gable vents and such. I got 2 more walk through today, supposed to be quotes by tomorrow, which will give me 6 total quotes plus 2 refuse to quote.