I read a review recently from a gutter guard customer who purchased a metal screen from a big box store. The customer explained the problem he was having with water not entering the gutter. He put up his ladder and viewed what was happening as the exterior winter temperature was dropping below freezing. He explained that the openings of the gutter guard screen were clean and accepting water fine, however the fact that the temperature dropped below freezing, caused a “first to freeze zone” right at the gutter screen. He literally could see the screen openings beginning to shrink as the ice built up on the coldest spots which were of course the screen over the gutter. The home and roof had retained warmth, however the gutter and the gutter screen were completely exterior with lots of surrounding air flow , therefore those items reached the freezing point first. He literally watched as his gutter micro screen froze over creating a solid sheet of ice covering the gutter causing the water to overshoot the gutter. In his negative review, he went on to explain that the roof was not yet iced, the gutter under the screen was wide open, free of debris and free flowing but the water couldn't enter the gutter because the gutter screen openings no longer existed.
Below is a picture I personally took of a helmet type gutter cover, during a very difficult winter in Rhode Island. When a gutter has a small ice problem, if the conditions persist, the ice level grows higher day by day and melting that occurs from the interior building’s heat loss, creates a pool that backs up and leaks into the building. As the picture shows, you really should not install any metal gutter cover or gutter screen device that intersects with the roof and has a lower slope than the roof itself, thereby slowing or stopping water and ice.
It is a known fact that metal is a temperature conductor and that all metal items create a “thermal bridge”. In construction over the last 30 or 40 years, certain specialty construction fasteners have been upgraded from metal to plastic so that they will no longer conduct temperature and also so that they will not lose as much heat from the interior of the building. One particular exterior fastener made of plastic, even adopted the name NTB fastener, which stands for non-thermal bridge fastener, illustrating the improvement by changing from a metal fastener to a plastic fastener. I explain all of this to illustrate the obvious reasons that metal screens and covers cause ice problems in certain climates. A non thermal bridging material such as plastic would not cause such problems because plastic does not conduct in the same manner as metal. Perhaps that’s the reason the below photo depicts a gutter cover customer putting the gutter guard out in the trash. The contractor replying to the problem probably explained that there was nothing he or she could do to rectify the problem as long as the gutter covers were fastened and in the way. You can see in the picture how the shingles remained cleaner where the helmet style gutter cover had been installed and removed. I hope the contractor remembered to seal the roof nail holes resulting where the gutter cover was removed.
Author utilizes his own 25 years of winter "on the roof" experience to explain