#INSULATING OLD PLASTER AND LATH EXTERIOR WALL INSTALL#

#INSULATING OLD PLASTER AND LATH EXTERIOR WALL INSTALL#

In no time-sooner in a stucco wall, which depends entirely on the integrity of the drainage layer through which the holes for the insulation were drilled-you will find moisture levels exponentially rising in the wall cavities.Īnd if you really want to maximize the damage, install a set-back thermostat that drops the temperature to 65✯ at night. Then fill the cavity with an absorbent material like cellulose, which holds moisture, so that any leaks will go undetected and the wall will stay wet for longer. Adding batt insulation is bad enough, but if you really want to kill a house fast, drill some holes through the cladding, the drainage plane, and the sheathing to completely destroy the wall’s first line of defense and pave a path for bulk water to enter the wall cavity. Uninsulated, unsealed walls dry out because they “breathe.” But adding insulation-and doing nothing else to manage bulk water, vapor, or ventilation-destroys this cycle. This may not be what the energy-efficiency community wants to hear, but physics is physics. Insulation placed between the studs of pre-World War II homes is the single most dangerous element in the wall assembly. As it turns out, this is the worst thing you can do to an old house. Not only did we add insulation, we often did it in the worst possible way: by drilling holes from the outside, blowing in cellulose, plugging the holes, and painting over it all. Since the 1950s or thereabouts, this simple wood wall has gained another enemy: the quest for energy efficiency. Though this was inefficient in terms of energy use, it wasn’t lethal to wood walls. That allowed the sheathing and wall cavities to get wet fairly often, but heating the homes would dry out the wood. The walls were wrapped with overlapping layers of paper with little or no flashing at openings or horizontal exterior trim elements. Homes built before the 1950s worked in much the same way. There were no building scientists or ventilation standards, and yet the buildings performed incredibly well and lasted for hundreds of years. The assembly could hold moisture without causing it to condense, and the plaster could dry very quickly.

German post-and-beam homes used straw infill as insulation and a lime-based plaster parging as the cladding and air seal.

There’s just one catch: It must be given the chance to get dry. But when it comes to a fourth enemy, water, wood is amazingly resilient. An encounter with termites, fire, or a weekend warrior is almost always fatal.

Insulating old plaster and lath exterior wall