Here are the US Department of Energy's recommendations for economically efficient insulation levels.

In my area, your ceiling is below Code, walls are over.

R-28 in walls is probably overkill. Not that overkill is a problem but around here r-19 is really good and so is R-40 in the attic. So at least around here - you are roughly looking at twice the R-value in the attic as the walls.

To give you a comparison - your windows are probably r-4. Your door is likely R-12 or less.

You also have to take into consideration that foam is close to a true r-value than most othher insulation types. You also have to consider the envelope as a whole concerning doors, windows, skylights, etc.

first, the R-value of closed cell is R-6.7
6.7 x 3.5"=R-23.4 Not R-28.
R-values are less with open cell foam.

R-values are recognized by state and federal programs
and are the standard that all insulations are tested to perform to. These values should be true to the recognized
R-value per inch used by all insulation mfgs.
not just numbers used by foam insulation mfgs.

Windows have a standard rating numbers common to all brands also to make it easier for the consumer
to comapre brand to brand. Solar Heat Gain Coefficients
(shgc) and U-Factors. SHGC should be .35 or less.

Doors are R-value..metal insulated doors are R-4.40
a solid wood door is R-1.70

R-values in walls and ceilings are different because
of the depth of the framing members.
3.5" is a 2x4 5.5 is a 2x6 etc...
this is why you can't get R-38 in walls.

Are you foaming the attic floor or roofline?

best of luck.

Yes, we are foaming the attic and roofline. I keep reading that an r-value is not the be-all end-all. If we look at heat loss in terms of convection and radiation, it seems that with a vapor barrier we are ok on the convection front, but will continue to lose heat through radiation (esp windows).

Don't try to make the insulation values the same in the roof and walls. Splitting the insulation value 60:40 as the contractor has recommended is a better approach If want to increase the wall insulation you should also increase the roof insulation.

Importance of r-values concerning ceilings,walls, floors is in that order. They are all a concern, but the ceiling/roof is the most important factor, followed by walls, floor.

If you have an attic, you can always increase R values later - by hanging cellulose batts under the foam roof insulation. (these are NOT placed on the attic floor)

The number one goal of the foam is air sealing - if you want more "R", you can spray the foam first, then have batts or dense packed cellulose placed in the walls - assuming you have the room for it.

A cathedral ceiling is the #1 place to maximize insulation - as retrofit will be almost impossible.

Make sure they do a blower door test, as you house will probably be "tight" enough to require an HRV. (heat recovery ventilation)

We are adding an air exchange system since the builder thinks we need it. DH and I look at each other and laugh frequently about all this. It feels like The Stupids Build A House.

Major construction fatigue is setting in. I have a date in the builder's office (armed with coffee and muffins) for every day this project goes past May 1st. 8:00am sharp on his doorstep w/ the biggest smile I can muster.

Better make it biscuits and gravy
and 6:30 am.

LOL!

best of luck with your project.

Good idea! I've given them advance warning regarding the upcoming coffee and donuts routine- to encourage all to hustle- so it won't be a surprise to them.

You dont say how little, your little house is.

If it gets to -22, R38 in the attic would not be adequate for me.

If you are insulating now, you could be looking at several weeks of biscuits and gravy after May 1st.

Without telling us precisely where you live (city and state) so we can determine the degree heating days and your state energy code, any advice given here about insulation levels is completely meaningless.

You don't necessarily need the degree days. Just go to the REScheck site linked below and enter the project information to see if the design complies with the energy code for its location.

All residential projects I have designed in the last 10 years have been required to have a passing REScheck score. All but 6 states currently allow it's use as evidence of energy code compliance. It's major advantage is that it considers overall energy use (insulation thickness and mech. equip. effeciency) and allows you to shift insulation and equip. values to see what combination is most effective.

You can also download the software at:
http://www.energycodes.gov/rescheck/download.stm

Here is a link that might be useful: REScheck online calculator

It's about 1750 sq ft. I just wonder if we should ask them to spray more in the attic, which is more like a crawl space anyway. Even though contract says 5/1, we are expecting somewhere in the 6/1 timeframe. Here is the floorplan-yes, we have a drive-through garage:

it is helpful to know the area..what is your climate?

has hvac contractor sized the hvac system for your home
including upgrades that effect the sizing?
your unit should be sized using manual J not rule of
thumb sizing. load calculation should include specific
R-values, SHGC of windows, shade vs sun. size of overhang
orientation etc. tight efficient homes require less tons
of hvac. this is one of the paybacks of efficiency.
then use the $$ from less tons of hvac to upgrade efficiency of system. you may qualify for tax credits
depending on how that whole thing shakes out!

and Manhatten42..I've got some foam questions of my own if you would have time to answer in another thread.
\precciate it!

We're in the upper NE- VT/NH line. No HVAC. We're doing in-floor hydronic radiant so, of course, we have a boiler. I am really glad to be skipping the duct work...less dust. Actually, there are a few ducts for the air exchanger.

You would have been well advised to incorporate the "Radiant Barrier" roof sheathing (ie: Thermastrand) which works better than you would ever imagine. You could still put up the "staple up" insulative roll either across the bottom of your rafter framing members (perpendicular) or in the individual rafter bays (parallel). Try using this product one and you will never go back....

In this project's location a radiant barrier would not be cost effective and if the foam is sprayed directly against the bottom of the roof sheathing, there would be no air space to allow a radiant barrier to function anyway.

Radiant barriers are best used in very hot climates with conventionally insulated attic floors.

There seems to be several common basic misunderstanding about the purpose of attic ventilation in different climates. There are no simple rules of thumb for all circumstances contrary to popular lore. If you want to really understand how to do it properly get Lstiburek's book, "Moisture Control Handbook: Principles and Practices for Residential and Small Commercial Buildings".

Here is a link that might be useful: attic ventilation explained

Here is a cheaper way to learn from Joe Lstiburek

Here is a link that might be useful: Lstiburek on attic ventilation