Up until the 80’s there really was no regulation on the amount of insulation required when a home was built and they really didn’t care what the R factor was. From the 30’s to the 70’s the answer to the question of if the home was insulated was either “yes” or “no”. Attic insulation on older homes is one of the most rewarding and cost effective home improvements you can make.
I approach home improvement projects the way I approach anything. I was raised to always make things better, mechanically, physically and even emotionally. Taking the time to do it right when it comes to attic insulation on older homes (or any home) is one of those tasks that is very easy to make improvements on especially if you do the preparation yourself.
The first part of preparation is to know what you are insulating against. If you are living in the desert southwest you are insulating against heat and radiant energy while at the same time trying to optimize airflow through your attic and if you are in Twin Falls, Idaho or upstate New York you are insulating against heat loss while trying to create an air-tight pocket in your attic.
Committing to the level of quality outlined here is normally something only a homeowner will do for themselves, but it is a very good idea to document this with video or at least pictures. This level of quality is not overkill and this will improve the value of your home more than just saying it has new insulation (especially to buyers that appreciate quality).
Cold weather and hot weather are different when insulating, but they are the same when it comes to removing the old insulation. Everyone will tell you removing old insulation is a waste of time and money, but do not listen to them because they are wrong. Nasty old cotton or ground up jeans is just a stinky waste of space even if there is a nominal R value related to them. One day I will tell you the true story of a 1940’s home I bought that was insulated with magazines (magazines; that is not a typo).
Use common sense and observe all safety precations. If you are changing the attic insulation on an older home then use a respirator (not just a mask) even if the insulation is not fiberglass. Mice love biodegradable fluffy insulation and if you live in an area with Deer Mice the threat of exposure to Hantavirus is a real possibility. This virus is potentially deadly so do not mess around.
The best way to remove any type of loose insulation is with fiber sacks (gunny sacks, grain bags) because they breath you can compress the old insulation.
As an option, when the majority of the insulation is out you can go back up to the attic with a shop vac to get the corners and crevices really good. The cleaner the better.
For hot weather insulation, if your home does not already have roof vents (whirly birds) and gable vents, now is the time to install them. If you have the ambition and the desire, a very cost effective improvement that people pay a lot of money for is to install a thermal barrier on your truces. Don’t use some space age polymer that is priced out by the square foot, just get some roles of ¼ or 5/16 fire resistant Styrofoam and some wood strips and shoot it into the roof truces with a brad or staple gun.
This is also an optional step depending on your application, but if one of your gables faces the sun when it is very heavy you may consider putting insulation on the wall.
If you are doing the video or picture documentation this is certainly the right time to take pictures. There is no loose insulation and everything else is insulated nicely.
Now it is time to bring in the loose insulation. You can do this yourself or hire someone to do it for you. Either way, don’t be shy; I personally load it up to almost double the regulated minimum.
The first step is to go into the attic when it is very light outside and look for any obvious rays of light shining in from the outside. If you find any, block them.
Second is to install rolled 4 or 6 inch insulation at the roof between the truces and to make removable panels of plywood that will cover the vents in your gables (if installed). These can be removed during the summer to promote ventilation.
Take some pictures and install the loose insulation. Once again, I personally like to go double on the required minimum.
Many people like to use their attic for storage, but to do so you need to put some planks down to span the truces so the boxes don’t fall through the ceiling. This is a major insulation killer. The right way to do this is to locate a “load bearing” internal wall and install a platform in your attic that is about 18 inches tall. This will allow for sufficient insulation under the platform and a very nice “shelf” to safely store boxes.