Cheron used to go into her walk-in closet after showering and cringe every time during the winter. The room was always freezing cold even though the rest of the house was comfortable. Turns out that Cheron’s walk-in closet was the room over the garage.
There are several reasons why these rooms are so cold in the winter and then hot in the summer. Most people believe that the cause is from a lack of insulation in between the floor and the garage below. The actual main contributor is the bane of comfort’s existence…..the knee wall.
What’s a knee wall you ask? It is the vertical wall between interior space and attic space and they are often around more rooms than just the room over the garage. Why are they such a problem? Knee walls are subjected to the same extreme temperatures that your attic is, yet they are usually only insulated with poorly installed R-13 fiberglass batts and they are never air sealed. Knee walls can often be spotted by their access doors.
The only good thing about knee walls is that they can be greatly improved for a lot less than most of the suggestions you will get. The most cost effective way is to have a rigid foam board with a foil faced radiant barrier installed over the existing fiberglass batts and then having all the seams sealed. This creates a permanent and consistent thermal and air barrier between you and the attic areas. This is actually current energy code.
So after calling the HVAC guy and the insulation guy that both suggested rather expensive “fixes”, Cheron made the right call to The Energy Guy. Just because someone has been doing something “forever” doesn’t mean they’ve been doing right. Building science trumps salesmanship every time. Now Cheron no longer cringes every time she enters her walk-in closet, and that makes her happy. So don’t throw money at your problems, throw knowledge, it’s a lot cheaper.