We have been agonizing over what insulation to use for a while now and it has come down to crunch time. We live in a snowy heat dominant area of Ithaca NY.  In our area the Prescriptive Insulation Requirments are Wood Frame Walls: R-21, Floors over unconditioned space: R-30, and Ceilings: R-49 (R-30 permitted in catherdral ceilings up to 500 s.f. maximum area) per our architects specs.  Other info is radiant floor heat with geothermal.
Our contractor got a quote from a spray foam company that includes: 

-Spray exterior walls with HeatLok Soy winter blend to an average of R21
-Spray vaulted roof deck to average of eight inches with Agibalance
-Spray on top of sheetrock ceiling with Agribalance to an average of eight inches.
-Spray basement rim joist to an average of R14 with HeatLok Soy

We are fine with the closed cell R21 value for the exterior 2 x 6 walls which also has Alside Prodigy Insulated siding on the exterior along with Tyvek.   '

Our builder said the additional cost of 3K for the closed cell in the flat sheetrock ceiling seemed high so he recommnded we put up a vapor barrier (installed already) and spray 8" of Open cell up there.  My wife and I have been reading a lot (too much) information and seem to be on the fence about forgoing the Open Cell foam on the ceiling floor and are leaning toward possibly use 16" of blown in Cellulose up there instead.  Our contractor said we may want to seal it first with a layer of Closed cell foam to help insulate it better.  I am also concerned about the weather here and spraying foam.  It is in the single digits today and he wants to schedule this for next week.

We also have a dilema with the "vaulted area" which is really just the vaulted area above our side of the house.  That side of the house is 1 1/2 story where the rest of the house is 2 stories.  This area comprises an "attic space(future room)" which we have decided to just finish off now since it would be cheaper.  The room is accessable from our loft and it already has radiant floor tubing installed below the subfloor and will get R13 insulation under it.  The room is centered over our bedroom&bath and was built up a little to match the flooring on the second floor.   This vaulted area has baffles running from the bottom of the soffits to the ridge vent at the peak.  Our builder has also stuffed fiberglass batting at the bottom area of the soffits so the Open cell foam will stick to it and make a seal it from the outside.  Does this sound like the best approach?  We are pondering if we should just spray foam over the entire baffle area on the roof deck with open cell spray foam to the peak OR just put 16" cellulose on the ceiling floor, and spray foam up the framed out side walls of the proposed room enclosure up to where the the upper baffles meet the roof deck and then spray the small peak area with spray foam too. This way we wouldn't need to spray the entire baffled roof deck.  I hope I'm not confusing anyone and have a picture if needed.
 
We noticed the lack of R in the quote concerning the vaulted roof deck and our builder said it doesn't meet code but the inspectors are fine with it since it really has a higher R value than stated (I did read Dana1 attached article concerning this issue).  Our builder did ask if we wanted to put another 2 inches of the open cell there.  The roof has water and ice shield too.

Thanks

I think I need the picture.

I'd concerned if there's Ice & Snow Shield over the entire roof in any unvented situation unless there was both the proper amount of exterior rigid foam above the roof deck and at least semi-permeable insulation on the interior, with no poly. Since you've installed a vapor barrier at the ceiling, you're committed to a ventilated design, whether it be an open attic with cellulose on the floor, or foamed below baffles at the roof deck. With poly on the interior and Ice & Water Shield on the roof deck, unventilated you'd have a classic double-vapor-barrier moisture trap. I'm not visualizing how the vaulted area is air-sealed/insulated/isolated from the open attic portion, but if the open attic needs to be ventilated and the roof deck needs to be ventilated, you must leave the rafter baffles open to provide the path.

With a poly vapor barrier installed at the ceiling, unless it was ripped when installed it's already a pretty-good air-barrier, and adding spray foam there has little additional value beyond it's rated R, which comes at a premium. If needed to make the poly air-tight, spot sealing with spray foam makes sense, but not 2" unless the joists are 24" on center or something and you need the additional rigidity. An initial depth 16" of cellulose would give you a true R50+ (aged/settled R) compared to ~R36 for 8" of Agribalance. Even at 10" Agribalance is still 10% shy of a code-minimum R49. Where you can, insulate with the R/$ value-goods, and apply the difference elsewhere: Are the basement walls ICF or otherwise insulated? How about the slab (or is it too late?)

Foam backed vinyl siding provides additional R value and a bit of thermal break on the studs, but it's also an exterior vapor retarder. With ~3" of Heatlok Soy closed cell foam on the interior side of the structural sheathing the sheathing doesn't have much drying capacity toward the interior either (~0.4 perms). If you're going all closed cell in the stud cavites it's safer to go with 1-2" of exterior XPS or unfaced EPS under a standard vinyl sidin, which is inherently back-ventilated and can't trap moisture NEARLY as tightly as unvented foam-filled vinyl, or some other siding (preferably built backventilated with a "rainscreen" gap.)

If the siding is already a foregone conclusion, limit the Heatlok Soy to ~2" (~R14 and ~0.8 perms) and fill the rest with wet-spray cellulose, which would deliver ~R26 (center cavity, not including the R-value of the siding), and use nothing more vapor-retardent than standard latex as an interior finish. An alternative would be to go with 4" of 2lb Icynene (MD-R-200) which would give you about the same R value as 3" of Heatlok Soy, but with ~1.0-perms of vapor diffusion by which the sheathing can dry (low enough that the sheathing can take on 100% of the winter diffusion load without hitting rot risk levels, yet high enough to pass through exterior moisture drives from whatever seeps in behind the siding.)

Spec on the winter version of HeatLok has 25F as a lower bound for installation temp (I'd measure the temp of the sheathing, which may be lower than that of the air first thing in the morning after a cooler than 25F night.) Above freezing would probably be better. You may be able to get the stuff to stick at lower temps, but intermediate & long term dimensional changes as the stuff cures over weeks/months you may end up with separations, making it a less than perfect air-barrier. Use wunderground.com or similar to get projected time-of-day temps about 3 days in advance, and reschedule if it looks like there's only going to be a few hour window. You only get one chance to get closed cell foam right- hacking it out for a do-over is prohibitive.

Hi Dana1,

Just to clarify some things. The roof is vented through the whole attic with a ridge vent. And yes there are inspectors up here but I'm not sure why our insulating contractor (or builder) is offering this to us. To me basic math says his estimate falls far short of the required R-value in the ceiling (which is why we started to look into cellulose in the first place).

I think we are going to go with spot open cell Agribalance in the attic with 16 inches of blown in cellulose which should take us over the R-49 minimum requirement. This will take care of 2/3 of the roof.

For the vaulted roof with an attic room we have decided to install baffles from soffit to soffit (to allow the roof to breathe) and will spray 10-11 inches of open cell Agribalance which should take us to R-49+ for that area. That should take care of the last 1/3 of the roof.

The basement floor slab has 2 inches of foam board underneath it and 2/3 of it is heated via pex radiant tubes. The basement walls will be covered with a system to cover it to R-13.

The siding is already a foregone conclusion so we need to address the walls. It's Alside Prodigy (http://www.alside.com/index.aspx?page=51#) I did notice that the siding has weep holes. We also have Tyvek on the house. Will the Tyvek help? I have to call my insulation contractor about Icynene, I'm not sure if he offers it or not.

Thanks for answering so quickly. I think I'm comfortable with the roof now it's the walls that have me scared.

Gary:

Re; "I'm not sure why our insulating contractor (or builder) is offering this to us. To me basic math says his estimate falls far short of the required R-value in the ceiling (which is why we started to look into cellulose in the first place). "

Some spray foam vendors say that their products will give the required R performance without the actual thickness and municipal inspectors here will buy off on it as long as you have a document from the mfg stating it.

Re the question of making the attic a conditioned space or not, is there HVAC equipment of similar up there that would benefit from conditioning that area, or perhaps you may want to make it living space later, or would you just be adding more volume to the overall conditioned space which would require your manual-j calc for HVAC sizing to need to be redone?

If you really wanted to condition the attic the plastic could easily be cut off the attic floor - assuming there isn't too much stuff in the way.

Thanks all for the input.  Here's an update:

We called the manufacturer of Agribalance today and they informed us NOT to spray directly to baffles in the ceiling and to either spray directly to the undersiding of the roof (thus making it non-vented) or just use another form of insulation on the attic throughout the whole house.

The more we read the more we get confused because a lot of insulators seem to have differing opinions.

We have decided on the following:

1. The ceiling's in all the attic space will get sprayed with open cell around all potential "leaky" areas and then 16" of blown in cellulose will be applied which should give us R-50+ in the ceiling. Since we have no HVAC equipment or HVAC vents in our attic there is no reason to insulate the entire envelope.  We will never finish the attic space anyhow since it is a 12/1 pitched roof and just too high up to use.  We have a ridge vent on the entire roof so the area will just naturally ventilate itself.  Our HVAC contractor has made it possible to add an air exchanger at a later date if we find we need one.  We plan on living in the house for a year and monitoring everything before deciding on this.

2. All the exterior walls will get 3.5 inches of closed cell giving us roughly R23.  The foam should seal off any "leaky" areas and the exterior siding with backing will take care of the thermal leaks via the studs.  My only concern is what Dana1 mentioned about the exterior siding acting as a vapor retarder.  As I mentioned the siding does have weep holes and J channel plus we might possibly add an air exchanger at a later date.

This has been a really tough choice and further opinions are welcomed since we're still a few weeks out from insulating.

Since you'll have ~2" of space in the 2x6 framing, it's well-worth adding unface R7 econobatts or wet-spray cellulose to fill it out to ~R30. If you thinned out the closed cell foam to 2" and used unfaced R13 batts or spray cellulose for better drying capacity on the sheathing you'd have essentially zero condensing hours at the fiber/foam interface in your location, and would neither need nor want an interior vapor retarder, and would have ~ R27 center-cavity, not counting the foam-backed siding.

I've yet to see third party testing of the hygro-thermal performance of EPS backed vinyl, with or without weep hole drainage, but it can't violate the laws of physics. A full 1/4" rainscreen gap isn't even considered sufficiently drying for Canadian climates (10mm is prescribed by code), and I can't imagine that weep holes and narrow embossed drains in the EPS would have even a tiny fraction of the drying capacity of a 1/4" (6mm) rainscreen. I personally get concerned with less than 1 perm of inward drying capacity at the sheathing, and absolutely wouldn't with less than 0.5 perms between the sheathing & interior. (2" of HeatLok is hitting around 0.6 perms despite the "0.8" typo in my prior post.) With a rainscreen gap on the exterior to dry the sheathing it simply wouldn't matter, but that would considerably defeat the thermal performance the foam backing on this type of siding, with the rainscreen forming a thermal-bypass loop.

Dana1,

You have not mentioned the Tyvek. That is behind the siding and should keep moisture from getting to the plywood should it not?

Gary,
Dana can give you chapter and verse on vapor drive and diffusion. I want to talk a bit about the other side of the coin, Bulk Water intrusion. No matter how carefully walls are detailed, eventually they all leak a bit. Common areas of leakage are at windows, doors, corners, penetrations for plumbing, etc. If a house is going to last a long time, there needs to be some method for getting rid of this. A rain screen is designed to allow any water that penetrates the siding to drain. Sill pans get the water that leaked into the window opening back to the outside.
Basically first line of defense is proper overhangs and siding, second line of defense is airgap and vertical surface that water can drain down with proper flashings and silpans. The third line of defense is using materials that can dry via evaporation if they do occasionally get wet, or using materials that are not impacted by being wet(think ICF). Walls need to be able to dry somehow if they will survive. The slower they drive the riskier the assembly and the more careful you must be with flashings, etc. You can’t make both sides of a wooden wall vapor impermeable and expect it to survive long term.
cheers
Eric

Gary:

A few thoughts...

1) Tyvek is one of the better house wraps (WRB - weather resistant barrier) that is available. Really though where these types of WRBs shine is their ability to allow outward drying - which may be at least somewhat defeated by the foam backed siding. Did you say what the perm rating was of that - or maybe a link to the product? Tyvek is designed to not allow liquid water to pass, but to allow water vapor through - that is what makes it a good product. The thing you have to ask yourself is how water resistant is Tyvek once it gets 10,000 siding nails driven through it? So, you need some drying ability in the "outer skin".

2) Vinyl siding is designed to leak. For example it has expansion gaps at the end of the "boards" and other components. On one hand that is good because it allows some drying, but OTOH at penetrations like electrical outlets, hose bibs, and light fixtures it absolutely confounds me why designers feel it is OK that water is going to drain behind the siding. Windows often have integral J-channel, which is good and if they are flashed properly most of the water will be directed outward. J channel around most doors will rely on caulk (a temporary material) to keep the water out. So vinyl siding ends being somewhat weather proof during an average rain, but when you have wind driven rain - yea - water is going to get behind it and possibly a lot of water.

3) unrelated to the above, one of the principals of building science is that you don't want gaps, voids, ie unfilled space in walls. Here is why: let's say there is a 1/2" diameter hole in your insulation that is letting cold air in. So you think well OK - so 1/1,000,000 of the insulation blanket is missing, and you have a 1/2" diameter spot of cold drywall in your room - not a really big deal. Now introduce a 1" air cavity between the drywall and the insulation. Now that 1/2" hole is supplying cold air to the entire stud bay - so you now have an area of 14.5" x ~8' (or whatever the ceiling height is) of cold drywall - or a minimum of around 9 sq ft. Very bad. OK so you are going to have closed cell foam - one of the best insulations available - and there will be almost no voids - almost being the operative word.... What about a crack between a king and jack stud by a window or door? Enter cold air leak. OH - and BTW - the drywall doesn't really fit real tight to the studs so now you may have several stud bays with cold air being supplied to them. So, what I'm saying is 3.5" of insulation in a 5.5" wall is a bad thing. You need to fill voids with insulation to prevent air circulation.

4) it is a mistake to build a tight, very well insulated house and not install a ERV or at least an HRV - simply from an indoor air quality standpoint. People need some fresh air to come in and there needs to be a way for indoor pollutants such as VOCs, bad breath, :-) or whatever to get out.  If you need to wait, fine, but when complete, have your new home blower door tested and calculate the ACH (air changes per hour) and do some research and then the ERV thing will be crystal clear to  you - assuming the house is as tight as I'm guessing it will be.

Matt,

#1. We are using Alside Prodigy siding (Link: http://www.alside.com/index.aspx?page=51#).  It looks like a PERM rating of 5.0.
#2. Our siding guy is going out of his way to make sure all doors/windows and the siding are flashed and J'd to let water out.
#3. From what I read you're saying that no matter what insulation you use if the whole cavity isn't filled that is BAD.
#4. Our house will be very tight. We will most likely get an air exchanger within the first year.

#1: It's curious that they don't spec a perm rating on the product info page,( http://www.prodigysiding.com/product.php ) but state 5.0 perms on the Alside page (http://www.alside.com/index.aspx?page=51). If 5.0 perms is correct (and I'd be very curious to see the test report), you're good to go. 5 perms is more permeance than you'd get out of 1" of Type-II EPS WITHOUT a vinyl facing, so I'm a little skeptical. Even if the stuff is only 3/4" on average, (a thickness where Type-II EPS would be ~ 5 perms) and somewhat more permeable Type-I EPS, the very low-perm vinyl cladding on one side would tend to trump the perm rating of the filler. Third party test data and a description of the test setup would be useful.

#3: A partially empty cavity isn't totally bad per se, but beyond providing a potential thermal-bypass air channel, it increases the heat loss through the stud: With 3.5" of stud penetrating the HeatLok the stud represents a thermal short of ~R4. If you fill the remaining void of cavity with a standard insulation material such as cellulose or low-density batts the R of the thermal short rises to ~R6, a 33% reduction in heat loss from that element. That's the equivalent of adding 1/2" of EPS on the exterior from a thermal short point of view, but it's also adding a low cost R7 to the center-cavity R. The net boost in clear-wall value is greater than R6, even with the modest thermal break already being provided by the foam-backed vinyl siding (which is probably ~R2, maybe R3, depending on the average EPS thickness and the as-installed air leakage factors). And it's a CHEAP ~R6 compared to the rest of what you have going on. (And you could go with less foam, more fiber to achieve the same R, with better drying capacity.)

Overall, the enhanced thermal performance/$ you get by filling it out with low-cost wet-spray cellulose is going to be cost effective, where adding identical amounts of R with more expensive closed cell foam might not be. Then, from a fire spread point of view, filling the vertical channel with cellulose is more beneficial than adding firestop blocking (!). Closed cell foam is great for adjusting the vapor permeability or stuffing a lot of R in to a minimal depth cavity, but it's an expensive way to go high-R. Since you have the space in the cavity to meet your R-factor design goals for less money with a foam/fiber combi while providing more optimal drying capacity for the sheathing by thinning out the foam and adding the cellulose, that remains my recommendation. (Take it or leave it- I'm just "some guy on an internet forum", not your paid consultant, architect, or builder who you can hold responsible for the final performance. But where & when I'm wrong on the facts or $/cents I usually get called on it pretty fast on this forum. :-) )

#4 With a foam-sealed house designed & built with a defined air barrier for the whole envelope you should be building in the ventilation system NOW, not a year from now. You should be able to seal & test the un-insulated shell to under 2ACH/50Pa , if you're planning on reaching Canadian R-2000 type tightness levels (<1.5ACH/50) or better. By itself foam isn't a guarantee of tightness at that level, but it can sure help. Mere EnergyStar infiltration standards are only "kind of tight", and only in comparison to standards of building that paid little attention to air-sealing. An Energy Star home can still have nearly an order of magnitude higher air leakage than the 0.6ACH/50 that PassiveHouse standard allows, yet air sealing to those levels is by far the cheapest performance enhancement that can be built in. If you're at 3ACH/50 (considered tight, by some, and probably meets EnergyStar spec in Ithaca NY) active ventilation beyond spot exhaust venting could be considered something of a luxury not a necessity. Better to build & test it to <1ACH/50, and build in heat-recovery ventilation from the get-go in your climate.

On other comments, Tyvek, etc can only protect the plywood from exterior moisture drives or bulk water if the Tyvek has a good drainage path, as well as a vapor drying path to the exterior. Without both it's high permeance will let signficant amounts of moisture to cross between the siding and sheathing. It's designed to shed liquid water while preserving an exit path for moisture in the sheathing, but it's a 2-way street- if you trap moisture behind a vapor-retardent siding sans back-ventilation it WILL find it's way into the sheathing.

Posted By Gary C on 11 Feb 2011 09:55 AM
Matt,

#1. We are using Alside Prodigy siding (Link: http://www.alside.com/index.aspx?page=51#).  It looks like a PERM rating of 5.0.
#2. Our siding guy is going out of his way to make sure all doors/windows and the siding are flashed and I'd to let water out.
#3. From what I read you're saying that no matter what insulation you use if the whole cavity isn't filled that is BAD.
#4. Our house will be very tight. We will most likely get an air exchanger within the first year.

1. perm 5 is good.
2. if you understand the way vinyl siding works, you will see that water will get in.  A good start would be to actually watch it being installed.
3. right, for wall insulation. 
4. I'd recommend doing some more research on that.  When you move into a new home there are a lot of expenses.  Curtains, "our couch just doesn't fit in this new living room", "we really need a patio for the grill". etc, etc, etc...  That relatively expensive ERV will fall off the list in a hurry.

Further fresh air ventilation in a new home is even more important maybe even essential in a new tight home.  There are all kinds of VOCs (volatile organic compounds) in all kinds of different building material.  Many are probably already in your new home from sources like engineered lumber products and the VOC thing I don't think even came up in any of this insulation discussion.  If you really think you want to put off the ERV I'd look into low VOC paint, carpet, cabinets, floor finish, etc, or at least plan on having a window or 2 open until you get the ERV.  Seriously or at least install the ERV ducting without the ERV and the ducts shut down almost all the way and take the energy hit.  And, BTW, don't think I'm some kind of health nut, tree huger, wimp.   I'm a construction worker who intermittently breaths in stuff like dust from brick cutting and concrete grinding and cutting PT lumber, etc although I do worry a little about some of my workers who do stuff like work in enclosed areas (houses) with kerosene heaters, sand drywall for a living, spray paint and cut cement board siding day in and day out -  it is not at all unusual for me to hand these guys a dust mask.

ERVs I believe are required by some Canadian building codes and definitely required by US commercial codes for some situations - you know - those huge glass office buildings with not one single window that opens....  It is only a matter of time before they will be required by US residential codes - what with the time tabled energy efficiency mandates.   They are already SOP in some US locations - I think Minnesota, for example.

Lastly, none of this stuff is worth getting excited about - except #4.

Never under insulate. Double the insulation required by code pays back in reduced utilities. Less is irresponsible! The house should also be tight, below 1 (ACH/50) anything above that is again irresponsible! This is done by attention to details. A home that has no bills for heating and cooling easily pays for itself in utility savings. I have been building zero energy homes for 30 years. Do not let a contractor cut corners. You can save more than $50,000 in utilities over the life of a standard home by building right.

Brian

On the slopes I'd recommend insulating the cavity with cellulose and adding 1"-2" of Polyiso, taped. The sheets will add insulation and slow the thermal bridging, keeping your roof cooler.

I agree with you mars. In fact, Fiberglass one of the most common insulation used in home construction because of a few reasons. It is a very inexpensive and fairly effective product for resisting heat transfer. Keep in mind that fiberglass batts are "mass" insulation meaning that it uses its thickness and density to slow down heat transfer, but eventually the heat will transfer completely through to the colder side. The effectiveness of fiberglass insulation is measured in R-Value which simply describes the Thermal Resistance of the material. The higher the R-Value number is, the longer it takes heat to transfer through it.