In cold weather conditions, attic insulation is the best choice dollar for dollar. It is just like wearing a hat in the winter, you lose most of your heat out the top. There is a time and place for insulating walls in older homes when it is very cost effective and can significantly increase the value of the home.
With the exception of windows, the application of insulation on exterior wall for older homes is identical. The purpose is to create the best barrier between the inside and the outside.
Many older homes did not use sheet rock, they used slats, wire mesh and plaster for the interior of the home. If you are removing the slats to do an interior remodel then this is the right time to upgrade your older home to a modern level of insulation technology.
From the 30’s to the 60’s insurance was optional and even a nuisance, so if your home has any insulation you are lucky. If you are really lucky (as I once was) the builder would put some material in the walls as insulation. My luck came when I was shocked to see my 1938 home was insulated with magazines and news papers. Not only were they interesting, I let my wife loose on the inventory and we actually made money on the remodel.
The primary problem with the exterior wall insulation on older homes is the thickness of the walls themselves. Most of these homes were built with 2 X 4’s for the exterior walls, so the only solution is to make the walls thicker or contact NASA and let them know you are interested in buying up the discarded space shuttle heat tiles.
Insulating your home is a give and take situation. If the insulation upgrade will save you $500 per year on heating / cooling and costs $4,000 then you are looking at about 8 years to get to zero (adjusted for inflation and minus the value of the improvement). But, if you do the insulation upgrade in unison with a remodel then it is a no brainer.
There are two ways to improve the exterior wall insulation on your home; internally and externally.
If you are doing an external remodel (new siding) then strip the siding, install house wrap and then cover your house in 1 inch sheets of Styrofoam. This is very inexpensive and easy to work with. In both hot and cold weather this is a certainly not a negative.
One of the best times to upgrade your homes’ insulation is during a home improvement.
On an interior remodel you have the opportunity to get as serious as you want with the exterior wall thickness, and this is how.
Check with your local licensing agency, but there are very few restrictions on making your home stronger and more insulated.
First decide how radical you want to go with the increased wall thickness, for this example I will take exterior walls on an older home from 4 to 10 inches thick. This is assuming we are doing a strip down interior remodel, and we are ONLY doing this with the exterior walls for insulation purposes.
For this task we will need a supply of 2 X 4 studs equal to the number of 2 X 4 studs in the exposed exterior walls. If your home is old enough, it may have been built with rough cut lumber. To save money and for “character” I usually use recycled rough cut if the home was built with it and I can find it.
We are going from 4 inches to 10 inches, so rip your ¼ inch plywood in 10 in strips the short way. It is 8 feet long (96 inches) so this will give you 9 strip that are 10 inches wide and 48 inches long with one piece about 4.5 inches wide and 48 inches long (6 inches minus the saw cut on the other pieces).
I want to take a second to instill three pieces of advice that are learned from experience. If you are doing an interior remodel and when you pull down the slats and see wiring that has braided cloth or metal boxes, replace it. You do not need to replace it all the way to the breaker box (probably fuse box), but replace everything exposed modern plastic boxes, wire, and grounding ability. Second, if you want to get fancy, spend the extra $200 and buy a few spools of wire (if you want to do this yourself) and run both rj-11 (telephone line) and rj-45 (internet LAN) to every room. You do not need to connect the plugs, just rough wire it in. Third invest in a few (two dozen) Philips head bits for an electric drill.
Take all your 10 inch rips of plywood and cut them in half and half again to give you 4 pieces each that are 10 inches by about 24 inches.
Take all your 4.5 inch rips and cut them in 10 inch sections.
Our goal is to have two 10 inch by 20 inch pieces per exterior stud and 6 pieces of 6 inch by 10 inch pieces per exterior stud. The amount of plywood you need will be determined by the size of the project.
Using your drill and equipped with a generous supply of ¾ sheet rock screws, shoot two pieces of the 6 inch by 10 inch plywood into the existing stud at the top; one on each side. This is the “spacer” that will receive your new stud so the 10 inch side is the thickness of the wall. Do this to all the studs.
Now do the same thing at the bottom of each stud. When you are finished every existing stud will have 2 extenders at the top and the bottom.
Now walk the house and measure 18 inches from the top and make a mark on every stud and then do the same and make a mark 18 inches from the floor.
This next step will depend on if you are right or left handed. If you are right handed shoot the 24 inch by 10 inch spacers on the Left side of the existing studs; one at the bottom mark and one at the top mark.
When this is done, now you can add your new studs flush with the new 10 inch spacers and then add more additional reinforcements to the right hand side.
A lot of work, but a better insulation project than a home that will be built in the future.