How are the exterior walls of older homes insulated?
If you are planning to insulate the walls of an existing home be sure to choose the proper method. Fiberglass is most common in new construction homes where batts can be easily rolled into an open stud cavity. But getting insulation into an existing wall cavity that is closed on all sides is a much different task. Short of ripping all the drywall or plaster down, almost all insulating of existing sidewalls (retrofit insulation) requires drilling holes into the wall and blowing loose fill cellulose or fiberglass insulation material inside. How the insulation is blown into the wall will make a huge difference in the final R value.
Dense Pack Tube Method – The Proper Way to Retrofit Sidewalls
The Dense Pack Tube Method is the only acceptable method for insulating side walls. In this method only one hole is drilled per stud cavity and a tube is inserted all the way up and/or all the way down. Only after the tube hits the bottom or top plate of the wall cavity is the flow of the insulation material started. Only if an obstruction is encountered when the tube is traveling up or down the wall does a second hole need to be drilled. The tube method allows the material to be blown in under high pressure at all heights within the wall cavity. This provides uniform density of insulation material within the wall cavity AND enough pressure to compress the insulation material into the numerous small passages found in older walls. As a result, the wall is not only properly insulated, but it will also be functionally air sealed.
Directional Nozzle – Don’t pay For This!!!
The older method is called the directional nozzle method and results in a poorly insulated wall. This method should never be used – but some contractors have been doing it for decades and are unwilling to switch to more modern methods. In the directional method a nozzle is inserted into the stud cavity hole a few inches and the material flow is started. The nozzle tip has a slight angle to it and the insulation technician slowly rotates the tip as the material flows in. Unfortunately, the material can only flow 12-18″ away from the hole before it stops. Unless at least 4 evenly spaced holes are drill per stud cavity the result will be a poorly insulated wall. Over time the insulation will settle and in some areas there may even be voids. Racine Home Insulators have “re-insulated” a lot of these homes years later after an energy audit revealed the cold spots in the wall where insulation was missing or at very low density.