by John Pratten, Fluke Thermography, Plymouth MN
We had quite an interesting winter here in Minnesota this past year and because of the combination of snow and temperature, we had the perfect environment for some pretty good ice dams—if you lacked the proper ventilation and insulation in your attic or roof structure.
I recently visited a home in the Eastern metro area of the Twin Cities that had completed a remodeling job of their second story last fall. However, they were trying to understand why they had the huge ice dams they experienced throughout the winter. The remodeler was invited back, examined his work and claimed that the application of the hard panel polystyrene insulation was adequately installed and gave no explanation to the real problem—not the greatest of help. A week before my visit, the local utility sent someone to the house to do a normal energy audit, including a thermal scan, and other than showing the home owner a few thermal images claiming the lack of insulation here or there (not the case at all), no one discovered the real problem!
When I finally arrived, the first thing we did was conduct a walk-around—both inside and outside of the home—with the owner. We discussed the construction project and the ice dam problem. Because of the ice dam problem, it had been suggested that the owners reduce the temperature of the upper level of their home to help reduce the impact of more ice.
Following the walk-around, we started to view the structure with the infrared camera. We started indoors, and the images from the infrared camera showed a fairly well insulated home. We viewed all walls and ceilings, doors and windows—a few anomalies were found but none that would even come close to causing the ice dams they were experiencing.
We moved outdoors and viewed the complete structure as we walked around. All looked relatively normal until we looked to the roof. We noticed the pattern that you see in Figures 3 and 4—which was a warm pattern that showed up on each of the gable ends of the home. I went back inside to see if I could thermally verify what I was seeing, and similar to my first pass through the house, I tried to detect any corresponding thermal pattern.
Finally, I asked the homeowners if they had any pre-construction images and was handed a few, including the one in Figure 5. I added the arrows to show that the 2×4 framing extended beyond the ceiling supports. The lack of (or poor) insulation in this area could very well show the thermal signature we see on the roof from outside!
The suggestion I offered to the homeowners was this:
- Hire someone to do a visual probe to verify and if confirmed,
- Hire someone to fill each of these voids with foam
Per Roger’s question below, here is my answer:
I have included an exterior image of one of the gables (Figure 6). In this image you can see a well insulated exterior wall and at the same time see the warn line on the roof structure. The problem is that when the fiberglass insulation was installed in the ceiling, no insulation was placed immediately above the 2×4 wall section (very accessible during construction but just missed). In the adjacent wall sections, they installed 1 ½ in hard panel polystyrene panels, caulked at all joints and mounted against the outside wall. Although the panels insulated the wall sections, they created a warm air cavity on the interior portion of the wall. This warm air infiltrated through the wall header in the ceiling area that had no insulation, which caused that section of the roof to heat, causing snow melt and subsequent ice dams.
Since the image was taken, the home owner has had a new contractor back in to verify and fix the issue.