Installing Insulation From The Outside In? Sounds Crazy, But It Works!
This insulation technique is not for the weak of heart. It's a lot of work and takes time but the returns and satisfaction of doing it yourself are well worth the effort. After all, what other home improvement will pay you back 24/7/365?
One of our homes has been completed using this technique and the other is in the midst of it, with two out of six sections completed. There are extremely noticeable results that include significantly lower energy bills and no more drafty rooms.
What I am calling Reverse Insulation is actually a multi-step process that we'll take you through one step at a time. This process works very well on older homes like ours that have nothing their wall cavities but cold air in the winter and hot humid air in the summer.
Step 1: This step is the removal of your existing siding and sheathing of your EXTERIOR walls one section at a time which exposes the studs and the back side of your interior walls. You will either need a dumpster for the construction debris or you will be making several trips to the dump.
NOTE: Be sure to recyle any aluminum siding you remove; I just did and aluminum is at $.69/pound at my local metals recycler. You also need to keep your eye on the weather. Don't tear off more than you can replace before a storm comes or your going to have huge water and mold issues.
Step 2: This step is to air seal all joints where any pieces of construction materials meet, this is where air leakage occurs all year long and is costing you money. The best solution we have found is to use a closed cell foam kit, yeah they're expensive but they totally seal off all of these joints nicely and make them air tight. After sealing all of the joints I then use a fan nozzle and spray 1" of foam on the back side of the interior walls.
NOTE: An alternative to the expensive foam kits is to use a long life caulk sealant to seal all of these joints. Caulking is easy and much less expensive than foam. Caulk is typically rated in the number of years that it will do it's job, look on the label before you buy and don't buy the cheapest you can find, you'll regret it.
Step 3: You will now install standard fiberglass insulation in each wall cavities between the studs. I typically use unfaced R-11 as both of our homes are build with 2 x 4 walls. If you have 2 x 6 walls you can get even more insulation in those cavities, probably R-13.
NOTE: If you use the closed cell foam kits DO NOT use FACED insulation, use UNFACED. The reason is that if you spray the 1" of foam on the back side of the interior walls you have already created a moisture barrier and FACED insulation will add yet another moisture barrier and you will eventually get mold inside your wall cavities, not a good thing.
Step 4: Now you are ready to install new sheathing, either OSB (oriented strand board) or exterior plywood, whichever is the most cost effective at the time. They both move up and down in price based on current supply and demand of the markets.
Step 5: Install your new siding of choice. I always use cedar shakes as they are one of the most sustainable building materials known, they smell great, they resist insects and bugs, and cedar is a soft wood that's easy to work with.
NOTE: If you're using cedar shakes I recommend a 7" overlap and the installation of heavy duty felt paper before starting with your shakes. Always do a double layer at the bottom of your first course to form a nice drip edge for rainwater and other moisture.
If you are using other siding materials you will need to follow the manufacturer's specific recommendations for surface preparation.
After many weekends on the scaffold and ladders, here's the finished product. Two of the six walls sections have received new low-e windows and are now complete. Now on to the other four wall sections. Yes it takes time, but after all it's a labor of love and will last for another hundred years.