Denver Roofing and Ventilation - Why Is it Important

Why is ventilation important to my roof and why don’t you see icicles on new homes?

Roof ventilation is the most important part of the roof and the least understood and when done properly it helps eliminate the beautiful icicles that dangled from the eaves of our childhood homes, which is actually a good thing.

I had a roofer call me yesterday saying that he had been in an attic looking for signs of a leak and the entire underside of the roof was covered in frost. He asked if I had ever seen that before and what to do about it.

I have seen it all too often and the culprit is almost always ventilation or the lack of it. After a few questions here is what we came up with: In this case the home has gable end vents and new insulation blown into the attic. I had the roofer check to see if there were soffit vents and if they had been covered by the insulation. That is exactly what happened. In addition to the soffit vents being covered the house had two gable end vents.

Ventilation requires an intake and an exhaust, with the soffit vents covered one gable end vent becomes the intake and the other exhaust, this can draw weather and moisture into the attic area. In addition warm moist air from the home rising into the attic from the home can condense and freeze on the underside of the roof during very cold temperatures and then as things warm up or the sun hits the roof, it melts and drips down and presents itself in the home as a leaking roof. This problem occurred during a severe cold spell where temperatures were well below zero. My solution to this issue is to clear the insulation from the soffit vents, block the gable end vents and install proper roof vents along the ridge line. Vents along the ridge draw from the soffit area better than gable vents do and more completely vent the home.

Lack of insulation and improper ventilation is the cause of icicles and ice damming at the eaves as warm air rises into the attic it melts the snow on the roof which runs to the eaves which are colder and freezes. This can cause ice damming which can allow ice to back up under the shingles and leak into the attic. See my winter roofs blog for more information. Newer homes usually have more insulation in the attic and typically better ventilation, however I have seen soffit vents blocked in brand new homes as well as ones that have recently added additional insulation.

Ultimately the lack of ventilation can cause many issues, including mold, mildew, rotting of the roof deck and many other issues. More insulation isn’t always the answer. Many people wrongly believe they should cover their vents in the winter to keep their homes warmer. Winter is the time when ventilation is the most needed. Never cover your vents they are integral to the integrity and health of your home.