Sorry this is so wordy and long, but I want to explain our situation.
We live near Ames, Iowa and we are building our house as we go whenever money is available. We have ICF in the walkout basement, and 2x6 stud, with .5 in wood sheathing, and 1 in r-board foam sheathing + tyvek on the main floor. The roof is shingled and we are currently installing soffit/fascia and siding. The house is 3800 sq ft (1900 sq ft per level). The roof is 6/12 pitch with 2 ft overhangs and hip roof. We plan on finishing the basement first, move in, then finish the upstairs as we go.

When we first designed the house, we had chosen to go with a conditioned attic and to spray 3" of closed cell spray foam underside of the roof deck. This was mainly due to the fact that we would be finishing the basement first and since we wouldn't have any of the main floor wiringn/plumbing etc. done, we thought it would be better to put a little bit of insulation in the roof. We assume it would be a pain to insulate the attic floor and then try to do wiring and plumbing and all of that through the insulation. We would try to heat only the basement. As temporary, we would close up the stairwell and put 2" blue foam over the first floor and pile tons of free bubble wrap that I can get at work to help keep heat in the basement during winter months. We assume that we would not be very efficient in heating our home this way for the two to three winters it would take to get the main floor finished. But we've been living in a 100 yr old house with no insulation in the walls, no furnace (just a gas stove in the living room), and you can see the curtains billow in the wintertime, so we figure being cold won't be any different in the new basement than the old house. We can live with that.

Now, my DH is balking at the cost of the spray foam in the roof compared to putting regular fiberglass insulation in the ceiling, and he is also very concerned about any leaks in the roof being undetected with the closed spray foam. So since the roofer put ridge vents, we decided to install continuous vented soffit around the house. I figured if we change our minds, those can be sealed up for unvented attic scenario, which I still would prefer.

We had planned on putting 2" closed cell spray foam in the stud cavity to give us some insulation, yet still leave the stud bays open for our future work. This would also seal up the main floor, and we know we will need some sort of ventilation system.

If I convince the DH to accept the cost to go with spray foam in the roof, should we go that route for our location and climate? Would that end up adding a significant amount of space to make a difference in heating and cooling? I have my basement load calcs done, but haven't crunched numbers for the main floor.

Or would it be better to go with a sprayed ceiling in the attic (plus additional insulation over it to get the necessary R for our climate if spray foam alone doesn't do it) and a vented roof? I'm not sure it would be cheaper than spraying the roof, since we don't have a quote for that. Closed cell or open cell for this route?

One of our goals was to build a very well sealed and insulated home, when it was all set and done. We spent what we could to get the best windows we could afford. We had decided to spend the money up front in what we could to maximize insulation and minimize air infiltration, and we've been painstakingly planning and sealing up things as they are built. Hopefully that would pay off in savings in our heating and cooling bills and comfort over the long run. But I feel that going with just plain fiberglass or blow-in insulation in the attic as my DH now thinks we should because of cost, that would defeat the purpose of what we were trying to achieve. So I really don't see know if this should be the third option.

Any comments, suggestions, or information will be greatly appreciated.

CC foam between the rafters may/may not create a vapor & water trap between the roofing materials leading to potential soaked wood/rot situation. (And yes, roof leaks would be harder to locate.) Unless you're planning to turn the attic into living space (or conditioned storage space) it will be cheaper to foam-seal/insulate the ceiling and heap blown cellulose over that to obtain the desired R-value. 2" of closed cell foam would be a class-2 vapor retarder, and give you the first R13 while sealing all penetrations. Fiberglass (batt or blown) has performance issues in horizontal applications due to higher infiltration/convection rates- cellulose performs measurably better. But if you're going for super-insulation levels (R70+) cellulose is much heavier, and you need to design the ceiling on which it rests to be able to accomodate the load or it may sag over time. Some have gone blown-fiberglass with a 4-6" cellulose top layer (which dramatically restores the "lost" R-value in the fiberglass that occurs at high delta-Ts.)

If you initially foam the floor, then run the electrical etc later you can foam seal all of THOSE penetrations, then blow the additional R value in after the fact. Even 1-2" of closed cell foam is a HUGE improvement over just the sheet rock or sheathing, for both infiltration and insulation reasons. (It takes 2" to form a class-2 vapor retarder, but even a skim-coat can make a perfect air seal.)

Framing in an "energy heel" to allow a deeper insulation fill below your soffit vents keeps the insulation from clogging the vent or blowing around with the wind is a very low cost adder, and should be designed-in from the get-go.

Closed cell foam adds substantial structural strength, not just sealing & R-value, but it's a premium product at a premium price. There are plenty of other ways of getting the performance designed in. If you're going for super-insulation, read this before finalizing your wall design & layup.

http://www.buildingscience.com/documents/reports/RR-0903_High-R_Value_Walls.pdf/view

Fiberglass batts are also problematic for walls- they're impossible to install perfectly, and end up under-performing their rated values by double-digit percentages. If not spray foam, spray cellulose (with water-activated adhesives that prevent sagging over time) performs closer to theoretical, and can fill in micro-cavities that are impossible to insulate with batts. It's only half the R-value per inch of closed cell foam, and it doesn't add structure, but it does add significant amounts of thermal mass- it's a better "plan-B" than batts, for similar money. If you go with a double-wall configuration (or Larsen Truss), blown fiberglass will give you slightly more R-value for the same cavity than cellulose, and it'll weigh less (less structure required to support it.)

If you can, blower-door-test the framed & sheathed structure with windows & doors installed BEFORE you install any fiber insulations, and go around hitting all the air leaks with foam as you find them- it'll make the air sealing that much easier & better. Then, if all your fiber insulations are blown (not batts) they will generally perform better, with fewer gaps/voids/compression issues. DO take care that they're blown to the specified densities & depths (installation "fluffing" errors are common- somewhat more so with fiberglass than with denser materials.)

Dana1,

Thank you so much for your insight. You've given me some hope that something can be figured out.
I guess if it wouldn't be too much of a pain to work through a layer of spray foam in the ceiling to run our wires and such, then that option really appeals to me.

About the energy heel, I think that would be too late for us to frame in? Our roof trusses have already been framed in and the roof is shingled. I do remember that the guy at the lumber yard said he liked to order trusses with an energy heel on them, and I think he said 8"? 
In your post you say the energy heel is to fill with more insulation below the soffit vents, and pardon my slowness, but I don't know what you mean. We have 2 ft overhangs on our trusses, so our soffits are way lower on the outside than the inside ceiling height. But I have no idea that it should be that way. I thought the framer should have considered that somehow since the soffit barely misses the top of our windows by 2".

Anyway, you can see in the picture what our trusses look like installed. I hadn't really worried about it much since the plan was to spray foam the roof, so all of that was going to be sealed anyway. But now as we have been installing the soffit, I have been wondering how we're going to seal that gap there at the top of the wall to keep insulation from falling out onto the soffit, and keep a gap for air to get to the attic for ventilation. How is that typically done?

If we did want to pile up as much cellulose as we could in the attic, where can I find information on how to frame the ceiling to take the weight? I'm assuming I'll have to contact the truss mfg. to get a rating on the bottom cord of the trusses to double check how much weight those can take (2 ft o.c installed). But what about the sheetrock? Anything special for that to take the weight of cellulose. I'm trying very hard to keep our house fiberglass free if I can help it. I don't like the idea of working with that itchy stuff or even if someone else did it, to have that itchy stuff there at all.

And thanks for the article. I'll read through it. Though I really want to have some spray foam for the structural aspect of it too. After the Parkersburg, IA tornado of last year, anything to beef up our walls has been on my mind. That tornado was the reason we added the extra 4 ft. of basement wall under our porch to make it a safe room, and I remember some university did some study that a wall with sheathing plus spray foam did really good in their test against their stud cannon.

Boontucky-girl,

Although it is too late for your project, the heel goes right over the top of the exterior wall between the bottom and top chord of the trusses.  The heel separates the top and bottom chord thus providing more space for insulation.  In the South I usually specify a 12" heel to keep the soffit above the windows and to provide space for 12" of cellulose near the exterior wall.

Since you did not use an energy heel, then you might want to consider using spray foam to seal the attic and just forget about ventilation.

By looking at the picture you submitted I did not see any tie-downs for the roof trusses.  Did the framer use any metal clips or straps to tie the roof trusses to the wall?  Relying upon toe-nailing the trusses to the top plate is very risky in high wind areas.

I am in the same situation... in Eastern Iowa. I have been amazed at the lack of flexibility from local builders to use newer techniques that rely on science rather than "that is the way we have been doing it all along... and we haven't had any problems". Alton, how would you recommend sealing the attic? Is this practical in Iowa? Is there anyone with experience, willing to provide a quote for insulating a home in Iowa, if provided an email with the home plans on PDF?

Dolphin,

I have very limited experience with cold weather areas.  Wes or Dana1 can give you a better answer.

Here is my take on this problem.
1.  With HVAC equipment and ducts in the basement and no planned use for the attic:
Spray closed cell polyurethane foam on the attic floor unless the roof is not very steep.

2.  With HVAC equipment or ducts in the attic:
Spray closed cell foam on the ducts or seal the attic by spraying the bottom of the roof deck between the trusses and down to the attic floor.

3.  With HVAC equipment or ducts in the attic and the attic floor has already been insulated with fiberglass or cellulose:
Spray open cell foam on the bottom of the roof deck between the trusses and down to the attic floor.

Reminder:  The ducts should be wrapped in vinyl before being sprayed.  This saves a lot of time and effort if the ducts ever have to be opened.

You do have an 8" energy heel right now. In most regular trusses with no extra heel the top chord will meet the bottom chord on the exterior side of the top plate. In your case your bottom chord goes across the top plate and the top chord goes on top of that creating the 8" heel (3- 1/2" bottom chord plus a 6/12 plumb line of the top chord). Your truss documents will also tell you the dead load weight limits for your bottom chord or they may be stamped on the truss.

Unrelated but relevant to others: that is a good picture to look at the amount of wood we are framing with, I added almost 18' of unnecessary lumber, more if the double stud on the far right is unecessary equating to just over 2.2 square feet of uninsulated wall ignoring the 1" foam on the exterior. Thats just one window and 4 pieces of lumber; multiple that by the amount of windows and doors.

Alton - that's what I suspected a true energy heel might be. I also suspected that the walls should have been higher so that our soffits wouldn't end up so low. But I knew nothing about framing, only what I've read online, and it was too late by the time the trusses were up.

Tie-downs? Are you kidding me? We're not in Florida here, we don't need them. That's what I was told! They are on my to-do list, but I will have to buy them direct from Simpson stong-tie or someone like that. They want some sort of rating for the tie, and I don't have the time to figure that out right now since I'm not sure what all would be involved, and it is unfortunate that no one around here could help me with such a thing. (So sometime in the future you will see a post from me asking for help on how to find the info I need. I'm hoping it's something easy like I want to withstand so much mph wind, and I get a rating for tie downs.

Dolphin, I am with you at how frustrating it is to get contractors to do things the new way and not the "this is how it's been done here since the age of dinosaurs" way. As greentree has pointed out, my framer is of the school that if one stud will work, ten will be better. You have no idea the lengthy discussions I had with my framer to get him to try out some OVE techniques. I printed how-to manuals, research papers, and all sorts of stuff for him before he even got started. His reply was to try and charge me more because it was new to him, it would take him longer to figure it out, and didn't trust that framing at 24" o.c. with single top plates would end up in a strong wall. I tried to get him to use clips to hold the headers instead of putting 20 studs on each side, but he had never even heard of those things, and I could not find a local store that carried them.
I did convince him to do corners so that I can at least stuff insulation in them, and to ladder the interior walls to the exterior ones so insulation can be added there. This is the only reason why I added that extra inch of polyiso insulation on the exterior because I knew I had to do what I can for those thermal bridges.

The ironic thing is that two months after being done with our house, the lumber yard people went to a special seminar on guess what? OVE framing! So now they are all excited about this and trying to train their regular framing customers on this, and they were so excited to talk to me about it because I knew all about it before they even heard of it. It was almost enough to make me cry. :s And this isn't the only thing in which new or better techniques have been unheard of in my area. Radiant heating? I called ten different contractors and they all had no idea what heat loads were, didn't use any software that would do that for them, and they installed 1/2" pex pipe 12" o.c. regardless of what floor covering it was and other things like that. It is very frustrating. Specially when you come to sites like this and you get an idea that there are proper or better ways to do things, but can't find anyone local to do it that way. Unvented attics? At the 2008 home show here, none of the spray foam or roofing contractors I talked to had any experience with it, and they were mold death traps waiting to happen. 2009 home show? Finally, oh yeah, it's all the rage now. ICF houses? Not worth the expense, only a handfull of contractors in the whole state did ICF's. SIPs? What are those things? Couldn't find a framer that would frame some SIPs for us. Now there are stories on the papers of new innovative contractors using ICF and SIP. I'll get off my soapbox now.

Greentree, I tried my best to find a picture that would show the trusses at the wall that was not this picture! I am embarrassed to show this here because I *know* it should have been done better. But I could not afford to pay what the framer asked to do OVE framing, and we really wanted to work with him. (Not to mention that all of the framers I quoted I asked about OVE framing had no idea what I was talking about either). This window is the worst. Most of them have just the king stud, the jack stud, and a cripple stud together. This one and the living room windows have double jack studs. I believe the framer thinks he needs the extra support for the big headers, on the right side that's where the next panel of wall joined the previous one, thus the gizillion studs. He at least did do different size headers for different size windows, and didn't put headers in the gable walls like I asked.

Any help or pictures on how that gap between my trusses and top plate gets sealed and still allow for ventilation into the roof, yet keep insulation out of the soffits? I'm not sure that we will be able to go with unvented attic. My DH is against it now, and the price is steep, specially since it will not be living space, and ductwork (if any) will be in the basement.
I did get DH to agree that we will try for spray foam on the sheetrock. Should I use a few inches of closed cell and add blown-in insulation? Or do x amount of inches of open cell foam? Would it need additional blown-in on top of that?
Also, what sort of special things would I need to do to the ceiling to take the weight of cellulose if we used a lot of it? thick sheetrock enough? Have to add some sort of bracing between trusses?

Also, which type of foam is better? Local companies use icynene, InsulGreen, BioBased, EarthFoam, and some other brands. So how do you pick which foam is better besides choosing .5 lb or 2 lb. Strictly by price?

Thanks for the great input!

Pick the foam by workmanship & reputation of the contractor, then price. The best stuff in the world, improperly applied is of dubious value at any price. Performance differences at the same densities between foam manufacturers is negligible. Performance differences between a good vs. lousy job can be large.

If you're going to do the entire attic floor in foam with a heavy blow-over of cellulose, bear in mind that half-pound foam is compressible. An inch or two of 2lb foam may stand up better over time. If you're just air-sealing with the foam, either is fine. On a tight budget, go the foam-seal-only + cellulose route, but blower-door test the sealing job before the cellulose.

With heavy cellulose in the attic the loading issue isn't the framing as it is the load carrying capacity of the sheet rock and the dead-load rating of the bottom chord of the truss. (A layer of 3/8" OSB might be necessary to avoid sag in 20 years if you're going for R70+ in cellulose). Due to framing & truss issues you'll be limited to ~R30 at the soffits, but it's still worth going deeper in the middle as long as you don't exceed the dead load rating of the truss.

Also, with the budget in mind, air sealing the sheathing from the inside with caulk & foam then using wet-spray cellulose will give you roughly the performance of an all half-pound foam application, but attention to detail is key. Again, finding & sealing up as you go while under blower-door pressurization should be pretty effective. (Rough in the electrical etc. before the cellulose, just as you'd have to do with foam.) The length of time required for letting the cellulose dry before finishing the interior depends on the temperature & humidity- it can range from days to weeks. (It's best done in summer or early fall, but winter can still work if you have the time to wait.)

Dana1,

Air sealing the ceiling with foam plus cellulose on top is I think something that would work for us. As we can do the foam now and save up to add the cellulose when we're done finishing the interior.
So for air sealing purposes, since either would be fine, would there be a minimum I'd want of either? For example 2" of 2 lb foam or say what? 5" of open cell? Would I need to have the class II minimum rating up there?

So how would I find out how to choose what to do at the ceiling? Buy 3/4" drywall for unknown depth of cellulose fill? I guess I'm trying to avoid putting 5/8" sheetrock up in the ceiling to find out later that is not going to be good enough.

That third paragraph is talking about walls, right? We were thinking of doing 2" of 2lb. foam in the walls, do pluming and electrical as we go, then when we're done either finish with more foam or blown in cellulose.
I can't see the cost of all that caulking being cheaper than going with foam. Not to mention you have to have the time to do it, when the spray foam guy is in and out and done.
More dumb questions: When you say R30 at the soffits, you mean at the edge of the wall, right? You don't actually pile insulation in the soffit?

Thanks for the great insight.

Boontucky-girl,

Look at this website for hurricane ties for the trusses:  http://www.strongtie.com/products/highwind/new-products.asp?source=topnav

Click on the pictures for the H2A, H10A and TSP to see how they are used.

If you want to increase the R-value near the exterior walls and there is not enough headroom, then spray foam thicker in that area. 

The insulation stops on top of the wall.  If you plan to ventilate the attic, then try to insulate on top of the double-top plate but still leave an air space.  Foam baffles are available if you need them to keep the air space open.

Thanks Alton for the link.

I went and looked at insulation baffles for the ventilation, and the ones I saw look like they attach to the underside of the roof sheathing, and they aren't very thick. That still leaves me with a gap. I've drawn a picture to show what I have and I'm wondered what I should to to seal that?

Thanks.

Either cut some high R/inch foam (Like R-max) to go beside and on top of the top plate, or use a board between the baffle and the wall to be able to fill the area with foam. See pictures. This will be one of the hardest areas to get insualted properly, but if you don't get it good, it will reduce the overall R value significantly, because of the thermal bridging of the double top plate.

Excellent! Thanks aardvarcus! I was hoping it wouldn't have to be something special or complicated. That should be doable. I think the spray foam might guarantee a better seal, so we'll try that one.

A product like this http://www.adoproducts.com/wind.html may end up being cheaper time wise than making yur own. Another company makes a combo vent and plate block in one piece but I dont remember the brand offhand