2x4's vs 2x6's?
The originators of 2x6 style framing sold us on the idea of changing to 24" OC instead of 16" OC to keep total lumber cost similar but other drawbacks exist with such wide spacing of studs, such as wavy walls.
In fact, using 2x4s can be cheaper AND more efficient as far as insulation goes.
First, if one uses 2x6s one not only increases the cost to insulate, one also increases the cost in windows and doors sicne jambs must be ordered or constructed to fit a 2x6 rather than a 2x4 wall.
Second, 2x6s may add an increase in depth for and to include a 'thicker' insulation but this insulation alone will not insulate a home 'better' than a 2x4 wall with proper treatment...
Here is how most 'pros' do it:
-Construct 2x4 walls. (There is no less structural difference between that and 2x6) construction...
-Add 1 " of foam insulation on the outside of the house. This creates a thermal barrier that increases the insulating factor much mor greatly than simply increases the wall dimensions to 2x6. This also decreases the chance for condensation to form in walls. Eliminates the need for housewrap, builder paper, or other secondary weather barrier beneath siding.
- Eliminates the need for another and more costly 'backer' beneath vinyl siding...
Only 2x4 construction for me...with 1" foam insulation over sheathing on the outside. Compressed R-13 on the inside.
Not only does that create a warmer house than using batt insulation alone, it greatly lessens condensation problems is walls.
The reason is that by insulating the sheathing over studs, you can usually keep the stud spaces above the dew point so that condensation will not occur.
Foam exterior sheathing also eliminates convection currents within stud spaces for more uniform insulating tempertaures. This also reduces the potential for condensation.
Condensation in fiberglass reduces the ability of fiberglass to insulate.
Therefore foam over studs is much more effective than just fiberglass between studs alone.
But in all fairness, you could get a greater insulating factor using 2x6s with exterior foam compared to 2x4s with exterior foam, but the cost to benefit ratio may still not be there.
My wife likes 2x6 walls, it gives the window area more room for her cat to sit and look out the window
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Also, if you use foam instead of a house wrap, do you install the foam 1st and the windows second? Would this not cause the windows to be nailed into foam causing an unstable nailing surface since the foam may get futher compressed with time?
If you are using brickmold on the windowsfor acasing, the load is spread out enough to not compress the foam. Brickmold is for bricks though. a Casing is better for Hardi, IMO.
In warm climates it is best to add this faom on the exterior, but in cold climates, it is best to use it on the interior side of the wall
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The cross sectional area of 2x4 @ 16 and 2x6 @ 24 is almost identical. So for direct compression not considering buckling they have the same capacity. 2x6 walls have a higher capacity for bending, but that isn't actually the function of most walls. So when people say they are structurally the same they are referring to the final product in direct compression and it is a mostly correct statement.
Unfortunately, history has shown us that old structures made from 2x4’s are just as strong as homes built today with 2x6’s. One of the reasons, is the difference in nailing. In the old days, when we framed with a hammer, we used spiral nails that we drove in at an angle. Today, we use pneumatic nail guns. The nails are straight, not giving them much grip. They are also driven straight in. Rarely are they “toed” in.
As for insulation. We now know that when fibreglass insulation is installed, we get air pockets. The effective R rating of fibreglass insulation at 32 degrees is zero.
I remember a study in the mid 70’s in Minnesota. They tried something called “super insulating” using different techniques. Their most efficient wall style was a double wall with 2x4 construction. Essentially, they framed their exterior walls. They insulated them with fibreglass. They then covered the inside with foam board insulation. It was the cheap white foam, not the rigid boards we use today. Then they built another 2x4 wall against the foam insulation, being careful to have the studs offset. Their intention with this was to reduce as much convection of cold through the studs as possible. It worked. They were able to heat the house with electric light bulbs. There as no draft or air infiltration. Unfortunately, it meant an airxchanger needed to be installed. Today’s furnaces do that for us.
Hope that helps