Attic insulation removal causes Ice Dam


A contractor  hired to solve an ice dam problem ends up causing more harm than good.


This house was experiencing leaking in the winter after heavy snow fall due to ice dam buildup in the roof rain gutters and water backing up under the roofing. A roofing contractor installed ice and water shield along the lower edge of the roof eave and in the valley area and informed the owner that in order to reduce or prevent the formation of the ice dam more ventilation and insulation would be required in the attic.


The house had a ridge vent installed previously, along with gable end vents, one of which had a power fan attached for excessive summer time attic area heat exhaust. There were also six existing small soffit vents installed under the eaves, three in the front and three along the rear of the house. These soffit vents were blocked on the attic side by insulation and were not effective.

The roofing contractor suggested that either continuous soffit venting or additional vents be installed between alternating rafters along the eaves on both the front and rear of the house. Along with additional insulation, he suggested that the existing insulation in the attic that was blocking the soffit vents be cut back to the edge of the exterior wall and insulation baffles be installed to prevent any new insulation from falling into the soffit.

The homeowner contacted a remodeling contractor to perform the work. The remodeling contractor informed the homeowner that two new 4"x16" vents cut into the soffit would be sufficient to ventilate the attic. In addition, they would also go into the attic and remove the attic insulation that was blocking the existing vents. 

The work was performed in the fall.

By the end of December there was water leaking into the home and more ice in the gutters than ever before.

Ice dam and icicles on edge of roof.


The remodeling contractor did install  two new vents, which was not nearly enough to properly ventilate the attic. But, what really made matters worse was the work performed in the attic.

There, it was only necessary to remove the insulation between the rafters that was blocking the vents. Simply  pulling back the existing insulation and cutting a short piece off the end with a long insulation knife and then tucking the insulation back over the exterior wall would have sufficed. Not that difficult.

This contractor, as in this picture, removed a three foot section of the insulation from the soffit area and from the ceiling area and tossed it into the center of the attic. At other areas, he pulled back a large piece of insulation, and since it was a longer piece, doubled it back on itself and left it there with the ceiling exposed.


Missing insulation causing ice dam

     Insulation pulled back too far from the exterior wall and roof edge.


     A section of insulation removed and discarded from the attic leaving the ceiling exposed.

Now, not only are there insufficient soffit vents to properly ventilate the attic, the remodeling contractor has introduced even more heat to the attic space that needs to be vented. All the additional heat in the attic is causing more snow on the roof to melt, worsening the ice dam buildup in the gutters and adding more water to the roof area. This additional water backed up higher on the roof and eventually found it's way above the existing ice and water shield and leaked into the house.

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