Return to Energy Conservation Home Page

Insulation Project: Convert 2x4 Exterior Walls
To 2x6 Walls For Additional Energy Savings

by Mike Sakowski of

In the climate where we live, wintertime temperatures are often below zero. The 2x4 walls of our 40 year old home are insulated with a rock wool-type insulation that performs poorly. As a result, our home is very cold and uncomfortable.  In one room, we even had mold in the walls due to condensation within the insulation.

In the summer of 2004, I redid our boys' room and the result was a nice looking room that was very comfortable in the cold temperatures due to the new 6 inch walls. For an overview on that project, go to

The project went so well that I decided to redo additional rooms. This article deals with all the details of the next room I reinsulated, with a few more details and pictures included.

The room... before!

In the small room shown on the left, there is one small awning window on the exterior wall. Our goal was to replace the window with a long, double hung window to allow more fresh air, light and space for a bunk bed for our two girls. It took a bit of planning to make sure the window and bed set would both fit in.

You should obtain your window before starting the job. I found a window outlet, Walsh Windows, that manufactures and sells windows locally.  I was very pleased with their staff and service.

Take off the trim...

After planning, your next step is to remove the trim on the exterior walls and the walls adjacent to the exterior wall(s). Use a knife to score the paint line along the edge of the trim to minimize damage to the walls. Then gently pry up the trim. I used a taping knife to start lifting the trim and then used a pry bar. Try to not crack the trim or damage the interior walls and you will save a lot of work when you reapply the trim.

To remove the nails from the trim, don't hammer them out... pull them through the back with pliers.  You will do a lot less damage to the trim!

Take down the drywall and old insulation...

After removing the trim, take the drywall down as shown on the left. You will need a hammer, pry bar, protective glasses, gloves, and a dust mask. I find the best way to handle the debris is to break it into small pieces and place it in large heavy-weight garbage bags. This is a dusty job so don't skip the dust mask! Once the drywall is down remove all insulation between the studs.  Remove all nails and screws from the now bare studs.  (If you notice any condensation or dampness within the walls or on the insulation, allow wall to dry thoroughly before proceeding.)

A good tip: Use a utility knife to score the drywall on the vertical corners where the piece meets an interior wall and/or at the ceiling so you don't tear the paper and give yourself more work!

Heating ducts may need to be moved...

If you have heating ducts located on the floor close to the old wall, they may need to be moved (2" in my case).  To accomplish this, cut out a (2") portion of the floor so the heat duct can be moved. I used a combination of a jig saw, circular saw, and reciprocating saw to cut this piece out. After the piece is cut out, you will need to shorten the duct pipe (if you have forced air) by the same amount.

If you have hot water heat, you may need to call in a plumber to help with this task.

New window installation...

Since you have the room torn apart anyway, it may be a good time to consider upgrading your windows!  The easiest option is a "replacement window". Installation is simple for a do-it-yourselfer, and involves removing only the window sash since replacement windows utilize the old window frame, exterior trim & molding.  The actual window (slightly smaller than the original) is installed within the old frame. You can also choose to install a complete window that has nailing flanges that will (hopefully) fit in the space left by your old exterior molding when you remove it.

Because I wanted a larger and differently-shaped window, I had a larger project which involved cutting studs, replacing exterior sheathing and siding and reframing the window (see diagram below right). This last option can add days to the job, but I feel it was well worth it.

I used an expanding foam made especially for windows to seal the area containing the shims around the window frame. I like this foam product because it not only provides a weather tight seal but also provides structural support. Be sure to get the right foam - expanding foams not made for window/door frames can produce so much pressure they can actually distort the window!



If you don't have enough outlets, now is the time to add them. I had an additional wall outlet installed as shown in the picture below. Drill holes for the new wire with a 5/8" cutting bit - make sure the holes are set at least 2" back so no future screws or nails fastened into the wall can hit the wiring. Make sure the electrical breaker or fuse is removed or flipped off before the outlet is installed.


(Note from NH:  When doing renovations, you may be required to update ALL the wiring in the room to current standards.  This may include replacing wiring, adding additional outlets and more.  It's always wise to check with your local building inspector or an electrician before beginning the work.)

Install 2" Furring Strips

You will need to saw 2x4's down to a 2" width (or whatever is needed) so your finished wall will be 5 1/2 inches, the actual thickness for 2x6 walls. Measure your existing two by fours.  In some older homes they will be 3 3/4" or even 4" instead of the 3 1/2" of modern 2x4's. You will need a table saw to rip the 2x4's down to the needed width and nail the furring strips onto the existing 2x4's to provide a fastening surface for your drywall (or whatever wall finishing product you use). I used 16d coated sinker nails along with a few 20d coated sinkers on each piece.

Rigid foam insulation

If you have areas (like the header area shown to the left and along doubled up 2x4's) where there is a 2" pocket after applying the 2x2 strips, you can maximize the R-Value by filling the pocket with 2" rigid foam rather than fiberglass batts. Also, after applying the foam, I used  silicone caulk to seal up any cracks.

Add Nailers If Needed

For the room on this page, I applied drywall horizontally rather than vertically. This is the "standard" way drywall is installed when the studs are 16" center-to-center.  Since my studs were 24" on center, this left a near 2-foot gap on the edge of two sheets. This would have led to a very unstable wall.

To solve this problem, I fastened a horizontal nailing piece that was centered at the 48" mark to accommodate the edges of both 48" sheets (picture below). You should also check to make sure you have the needed fastening surfaces for all your pieces of drywall or other wall covering.

Insulate With Fiberglass Batts

Install the fiberglass insulation. I used unfaced insulation batts which I then covered with a plastic moisture barrier - the unfaced is a lot easier to custom fit to odd spaces and the plastic is probably a lot better barrier than what is offered with faced insulation. Also, tape all edges of the moisture barrier with a good quality duct tape or red insulation tape.

Install the drywall...

I placed the sheet on horizontally so there would not be a joint at the bottom or top corners of the window. For windows in cold weather homes, the drywall will often crack at the bottom and top corners of the window if there is a joint. I attached the bottom sheet first. I laid a bunch of shims on the floor near the wall to keep the sheet off the floor a little, leaned the sheet against the wall and marked the window opening.

I also used a handy trick to get the outlets cut out near perfectly.  I dabbed some ketchup on a paper towel and then blotted the outlets (below center graphic). When I leaned the drywall against the outlets they left perfect imprints on the back of the sheet! (shown right) I cut out the openings of the bottom sheet and attached it. I then attached the top sheet and cut out the window opening with it on the wall. Note that some will argue that you always place the top sheet up first to support the ceiling piece - in this case the 2x2 supported the ceiling piece.


Tape and Finish Drywall

I taped and finished the drywall with one step for imbedding tape (shown above right), and 3 additional coats over the top. Taping and finishing drywall can be challenging but you can get some nice results if you know a few basics. You want to apply light coats and level out your surface in between coats with your taping knife. Avoid any sanding until the very end and then only sand lightly. For a complete beginner's tutorial on taping and finishing drywall, check out

Prime and Paint

You need to prime the drywall surface (below left) and then place one or more coats of the desired color of paint. This is a good opportunity to repaint the entire room. After painting, this would be a good time to refinish wood floors if you have them.


Reinstall the base trim...

If you are using your same trim, you will have to shorten the base trim on the adjacent walls by about 2 inches. You should measure to get the exact length. Be careful not to cut off too much! You will also have to replace any heat duct covers. (Above right.)

Finishing touches...

You will have to reinstall the window trim or cut new trim if you installed a new window like I did. I like the natural pine look so I made my own window trim and sill out of 1x4's, 1x6's, and 1x8's. This is a very economical way to go. You can also obtain wood products to finish the window from the window dealer, lumber yard, or home store.

Return to Energy Conservation Home Page