There are no circumstances in which a 2x4 wall should be on the table in your location.
Spray foam r value 2x6 wall.
Using two dimensional heat flow analysis with thermal bridging effects and average framing factors it is clear that the thermal bridging through the framing bottom plate and top plate reduces the effectiveness of the spray foam insulation.
Dense spray foam is installed.
Spray foam kits are quicker and easier to use plus you get a seamless air barrier and high r value in just 1 inch.
Choose foam it green spray foam insulation kits and don t settle for less than you deserve.
Open cell spray foam has an r value of about r 3 7 per inch while closed cell spray foam has an r value that may be as high as r 6 5 per inch.
Two staggered 2x4 frame walls with exterior foam sheets and interior fiberglass or cellulose will get you a better thermal break higher r value and a much quieter house than 2x6 construction.
If you want to install spray foam in a stud wall and price is no object then it would seem to make sense to specify closed cell spray foam right.
That means if you used foam it green closed cell which is r 7 per inch it s r value for a 3 5 deep wall cavity would be r 24 5.
A typical 2 4 stud filled with open cell spray foam will have an r value between 10 5 and 14.
This is very important in situations where your code requires an r 21 for the wall but you only have a 2 4 stud because closed cell spray foam is the only way you would achieve the required r value to meet code.
The r value of the high density spray foam wall decreases from an installed r value.