Just lay the radiant barrier foil out directly over the existing attic insulation. It’s really a pretty simple installation. Holes from lights, and other fixtures can leave a direct path for a surplus of warm-moist air to enter the insulation and can condense before being able to dry out. Also, make sure the ceiling is sealed airtight. The tiny pinholes will allow water in the air (water vapor) to pass through the foil to prevent moisture from collecting inside the attic insulation under the foil and turning to water or ice. Internal air movement will be reduced resulting in higher R-Value performance of your existing attic insulation.ĬAUTION: You MUST use a perforated (heavyweight is best) radiant barrier for this type of over-the-insulation application. Installing a perforated radiant barrier over the existing attic insulation acts similar to the outer wind layer on a Winter jacket. Combining cold temperatures AND air movement dramatically decreases the effectiveness of traditional attic insulation. It’s a commonly known fact that the R-Value of insulation decreases as the temperature drops. This is called “convective looping” or the pumping of air through the attic ceiling insulation. Without the top air barrier, the cold dense air literally “falls” through the insulation and displaces the warm air trapped in the insulation close to the ceiling. The problem is that cold air is heavier and denser than warm light air. Minimizing Air Movement – We know that air flows easily through attic insulation. The foil helps keep the stored energy in the potato (or insulation) from easily converting to radiant energy. This is like wrapping a potato to keep it hot. Reducing Radiant Heat Loss – By laying the radiant barrier attic foil OVER the existing attic insulation, it works off the emissivity quality of the pure aluminum foil. 2) Minimizes Air Movement – called convective looping inside the attic insulation. Installing a radiant barrier directly over the attic insulation does two things: 1) Reduces Radiant Heat Loss. Without air barriers and a little wind, insulation can become almost worthless. Ideally there is very little air movement inside a wall, jacket or a down comforter thrown on the bed. The whole concept of insulation and R-Value is based on “Dead” or “Trapped” air. Why? Because fiberglass allows maximum unrestricted airflow. Think about this, most AIR FILTERS are made of fiberglass. Insulation does virtually NOTHING to stop airflow. You still have the inside air barrier (sheetrock), and insulation but NO air barrier on the attic side of the insulation. The problem is that to save money, many homes have skipped the outside air barrier in the ceiling assembly. Here are the layers of a typical wall – Outside air barrier, insulation/structural, inside air barrier. He also said that a ceiling should basically be a wall turned sideways. It would be like wearing a jacket WITHOUT the outer wind protection layer on a cold-windy day.” Aha!!! I was sitting in a building science seminar a couple of years back and the speaker said something like this: “The way we insulate ceilings in the North is just plain stupid. It seemed like that all my happy customers who were telling friends about their improved comfort and lower energy bills must be wrong. You can do the same research and you generally find that adding more insulation is always the recommended way to go. I found information (limited studies and research) on why radiant barrier was NOT a wise investment in the cold climates. I started doing some research on everything I could find on radiant barrier installed in cold climates. I was a little confused on why the word of mouth sales were so strong in cold areas. Today, some of my largest commercial customers are in colder areas. News of the good results would travel fast. After a while, I would see orders from 3 or 4 houses on the same street. “Comfort, Comfort…Comfort …oh, and some good energy savings too”. I asked why they were so pleased with the foil and the response was always the same. Admittedly, I don’t have a ton of first hand experience with extended cold periods.Ī few years ago when I first started selling radiant barrier I was pretty surprised by how many of my customers were from colder climates. Being a Texas guy, cold to me is about fifty degrees and REALLY cold is when it actually reaches freezing. It’s not just for hot climates like here in Texas. Radiant barrier is rapidly gaining popularity in cold climates.
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