Myth or Truth? Moisture and Radiant Barrier

Did you know that over 70% of all home issues are moisture related? Moisture problems are not always complicated to solve, but that doesn’t mean they can’t pose big problems.

Myth: Using a radiant barrier causes moisture problems that ultimately lead to mold and mildew.

Mold and Mildew. Probably the two scariest words to associate with your attic. To be proactive toward these potential problems, it’s important to keep your attic both cool and dry and that’s regardless if you use a radiant barrier or not.


Understanding Condensation

Condensation is simply water changing its form. You have a gas (water vapor) changing into liquid form (water). Water vapor is water that is basically suspended in the air. Condensation occurs when relatively warm-moist air comes in contact with a colder surface. An example of this is someone breathing on a cold window. Warm water vapor in your breath comes in contact with the cold glass and condenses (or converts) into the liquid form of water. So, foil does not cause moisture, warm-moist air and cold surfaces meeting together causes moisture. The key to avoiding moisture problems in your home is to eliminate the source of moisture – or warm-moist air.


Most Common Trouble Spots

What are the sources of moisture? Light fixtures, ceiling fans, bathroom fans, attic entry points, chimneys, and duct registers are the best places to start. Can-lights (recessed lights) and attic stairways are usually the worst culprits of air leakage, which carry warm moist air into the attic. If you live in an area that has consistently cold temperatures, it is imperative that you find these sources of air leakage and fix them immediately since prolonged cold temperatures can increase your chances of moisture occurring. You should take care of any of these problems before you think about installing radiant barrier, to make sure you’re setting yourself up for optimum results with minimum problems.


Read: How to Seal Can (Recessed) Lights


Being Proactive

The good news is that many of the moisture culprits can be easily addressed and economically fixed. Air sealing and good attic ventilation all go a long way in helping reduce the probability of moisture causing complications.


The first, and best, method is to SEAL up all the holes in your ceiling. In fact, you should do this even if you’re not installing radiant barrier. Sealing up leaky holes reduces the amount of air leaking out of your home, and ultimately reduces your energy costs. Sealing includes ductwork, HVAC registers, vents and any light fixtures that may not be sealed up completely; an easy way to tell if your lights are sealed is to turn on the lights that share the same drywall as the attic floor, then go up into the attic without turning on the light and look for areas the light is shining through. If you see light – that’s a sure fire way to tell the fixture is not airtight. However, just because there is no light coming through a ceiling penetration does NOT necessarily mean the hole is airtight.


Next, make sure than any vents from the inside of the home are vented upward past the insulation, and ideally out of the attic. Vents from kitchens, bathrooms or laundry rooms should all be routed so that they vent to the outside, not into the attic. If you have any vents that are currently blowing into the attic, they need to be re-routed before you install a radiant barrier.


Finally, proper ventilation in an attic is essential to creating a dry space. The idea behind ventilation is quite simple – don’t over complicate it. You need intake vents and exhaust vents; intake should occur at the bottom of the attic and exhaust vents should occur at the top since this is in line with natural airflow (warm air will naturally rise). Typically your intake vents will be your soffit vents. Make sure these vents are clean and clear of obstructions (insulation, paint on the screens or built up dust or dirt. etc.) so that they are functioning properly. Exhaust vents can range from gable vents and ridge vents to attic fans of all types. Again, ventilation is simple; you need to create an easy way for air to come in the attic and an easy way for it to leave the attic. This natural flow allows for moisture to freely move about and eventually diffuse. Incidentally, this is why radiant barrier is perforated and why you should always use a perforated product in a vented attic. The perforations in the foil are tiny pinholes that allow water vapor molecules to pass through. In an attic situation this is exactly what you want: moisture moving freely to contribute to an overall dry attic space.


Dealing with Moisture Build Up

As a preventative measures, it is recommended that if you are installing a radiant barrier and you are not 100% sure that the obstacles underneath it are airtight, it is best to play it safe and cut holes in the radiant barrier foil insulation above those areas. Ideally you want full coverage, but a little bit of foil cut out over a large install area is not going to dramatically alter your results or the effectiveness of the product.


So what if you are dealing with a moisture problem that already exists? Well the most important thing is to try to locate the source of the problem. Once you have determined where the moisture is occurring, you should be able to establish what is causing the problem. The best thing to do would be to remove any and all materials surrounding the source until you have remedied the situation. In many cases, it’s best to contact a professional when you are dealing with mold, mildew & rot since not every area that is effected will present the same characteristics.


While moisture has the potential to cause severe problems if untreated, do not let it scare you off from doing home improvements. Understand what you are dealing with, eliminate situations that can cause problems and make sure the space you are working in has adequate airflow and ventilation. Taking these precautions will allow your radiant barrier foil installation to go smoothly and it will set you up to receive the best-case results from the product. Remember: radiant barrier alone doesn’t cause moisture, but it can disclose areas where air is leaking from your home.

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