Why Traditional Installation Methods Cause Windows to Leak
Often enough, installers fit windows into the rough, untreated openings and simply spray-foam the perimeter. And while the spray foam does provide some thermal resistance, it does not provide:
- Leaves the sill particularly vulnerable to water ingress
- Can’t direct water out and away at the head of the window
- Doesn’t adequately air seal the window to the air control layer of the wall assembly
- Offers no drainage path for water to escape
These shortcomings mean that water can get in and stay in, leading to the formation of mold or deterioration of the wall assembly materials.
How and Where Does a Window Leak?
RDH Building Science consulting firm answered this question in their research report, “Water Penetration Resistance of Window,” created for the Canada Mortgage and Housing Corporation.
While testing various windows and window-to-wall interfaces, RDH Building Science considered 6 possible leakage paths to determine which of them caused the highest frequency of water penetration and the most deterioration to wall components. These were the 6 paths the company assessed:
Possible Window Leakage Paths 1
Of these, RDH Building Science determined that paths 4 and 5 represented the highest frequency water entry and resulted in the most amount of water damage.
Leakage Paths – Risk of Consequential Damage 1
RDH Building Science also pin-pointed 6 risk factors surrounding window design and installation that allowed water leakage paths to occur in the first place. These are:
- Gaskets and tapes
- Window design and selection
- Quality assurance/quality control
Below, let’s take a look at the control layers of a window-to-wall interface, as these are crucial in preventing and controlling leaks.