Why Install Radiant Barriers in Cold Climates? – The Aha Moment.

A Convective Loop
How A Convective Loop Works Against You

Radiant barrier is rapidly gaining popularity in cold climates. It’s not just for hot climates like here in Texas. Being a Texas guy, cold to me is about fifty degrees and REALLY cold is when it actually reaches freezing. Admittedly, I don’t have a ton of first hand experience with extended cold periods.

A few years ago when I first started selling radiant barrier I was pretty surprised by how many of my customers were from colder climates. I asked why they were so pleased with the foil and the response was always the same. “Comfort, Comfort…Comfort …oh, and some good energy savings too”. After a while, I would see orders from 3 or 4 houses on the same street. News of the good results would travel fast. Today, some of my largest commercial customers are in colder areas.

I was a little confused on why the word of mouth sales were so strong in cold areas. I started doing some research on everything I could find on radiant barrier installed in cold climates. I found information (limited studies and research) on why radiant barrier was NOT a wise investment in the cold climates. You can do the same research and you generally find that adding more insulation is always the recommended way to go. It seemed like that all my happy customers who were telling friends about their improved comfort and lower energy bills must be wrong.

The Aha Moment.

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 would be like wearing a jacket WITHOUT the outer wind protection layer on a cold-windy day.”  Aha!!!

He also said that a ceiling should basically be a wall turned sideways. Here are the layers of a typical wall – Outside air barrier, insulation/structural, inside air barrier. The problem is that to save money, many homes have skipped the outside air barrier in the ceiling assembly. You still have the inside air barrier (sheetrock), and insulation but NO air barrier on the attic side of the insulation.
Insulation does virtually NOTHING to stop airflow. Most insulation is made of fiberglass. Think about this, most AIR FILTERS are made of fiberglass. Why? Because fiberglass allows maximum unrestricted airflow. The whole concept of insulation and R-Value is based on “Dead” or “Trapped” air. Ideally there is very little air movement inside a wall, jacket or a down comforter thrown on the bed. Without air barriers and a little wind, insulation can become almost worthless.

Installing a radiant barrier directly over the attic insulation does two things: 1) Reduces Radiant Heat Loss. 2) Minimizes Air Movement – called convective looping inside the attic insulation.

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. This is like wrapping a potato to keep it hot. The foil helps keep the stored energy in the potato (or insulation) from easily converting to radiant energy.

Minimizing Air Movement – We know that air flows easily through attic insulation. The problem is that cold air is heavier and denser than warm light air. 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. This is called “convective looping” or the pumping of air through the attic ceiling insulation. It’s a commonly known fact that the R-Value of insulation decreases as the temperature drops. Combining cold temperatures AND air movement dramatically decreases the effectiveness of traditional attic insulation.

Installing a perforated radiant barrier over the existing attic insulation acts similar to the outer wind layer on a Winter jacket. Internal air movement will be reduced resulting in higher R-Value performance of your existing attic insulation.

CAUTION: You MUST use a perforated (heavyweight is best) radiant barrier for this type of over-the-insulation application. 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. Also, make sure the ceiling is sealed airtight. 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.

It’s really a pretty simple installation. Just lay the radiant barrier foil out directly over the existing attic insulation. Get as much as you can and don’t kill yourself if you can’t get every spot. You can do-it-yourself or hire a professional installer.

Finally, don’t forget that radiant barrier is like shade in the Summer. Even “Cold” areas need some relief from the Summer heat.

I guess my cold weather customers were right after all. Year-round comfort and savings for a minimal investment is definitely an Aha moment.

Please let me know your experiences in cold weather applications.

I've written several other posts on this that you might be interested in. Check these posts below:

  • Everything You Need to Know About AtticFoil Radiant Barrier
  • How Radiant Barrier Saves You Money
  • Should You Install Radiant Barrier on the Rafters AND Over Your Insulation?
  • Radiant Barrier for New Construction
  • Tips to help your radiant barrier install go smoothly
  • 19 thoughts on “Why Install Radiant Barriers in Cold Climates? – The Aha Moment.

    1. I live in the NorthEast and have installed a radiant barrier on the under side of my attic rafters, as instructed. I am extremely pleased with the performance during the summer months.

      My question is, would I also benefit from installing a non-perforated barrier BELOW my attic floor insulation, to deflect radiant heat back towards the living space (if the barrier isn’t coming in direct contact with cold air, would moisture ever develop?)? I believe the top layer has already reduced the cold air looping effect you describe so well, so this seemed a reasonable approach to me.

      Thank you!

      1. Frank,

        Thanks for the comment. I’m a little unclear. You mentioned “under side of my attic rafters” – did you staple it up or lay it out over the insulation? As for putting foil below the insulation, it will work. By using a solid product (non-perforated) you would have both a vapor barrier (stop moisture and air) AND a radiant barrier as long as you can get an air space on one side of the foil. Typically this is done by running radiant barrier across the studs (walls) or bottom of joists (ceilings), THEN running furring strips (usually 1″x2″s) perpendicular to the studs or joists. Then, you would attach sheetrock to the furring strips.

        The end result coming from the inside out would be: Sheetrock => Air Space due to furring strips => Radiant Barrier Foil => Insulation

        Does this help?


    2. Very helpful, Ed, thank you!

      Just for clarification, I stapled the barrier to the underside of the attic/roof joists – works great for the warm weather and still waiting to see what will be yielded for the winter. Since I had a lot of barrier material left over, I thought this might be a good way to amplify the R value of the existing fiberglas insulation.

      Thanks again!

    3. i am in michigan and have been surprised by some of the demonstrations about reflective barrier. i am finishing a bonus room and have included radiant barrier in my plans. i was going to get enough to do my whole house, but most recent though i was on energy.gov and surprised to find they don’t recommend the product in cold climates. this baffled me so i put the question to you why the government wouldn’t recommend radiant barriers in cold climates. thanks in advance,

      1. To be fair, the government doesn’t recommend a lot of things that can be beneficial to the people – so that doesn’t invalidate what science can prove. Radiant barrier foil is proven to stop radiant heat transfer, so why would the foil dictate which direction that heat comes from? In the summer it’s the sun outside beating down on the home and heating it up, in the winter, the primary heat source is coming from inside the house, through forced air (your heater). The foil isn’t prejudice against the source of heat, only that heat can’t pass through the foil layer. So in cold climates this means better heat RETENTION, while warmer and Caribbean climates look for primarily heat REJECTION. There are contractors all over Canada installing radiant barrier by the truckloads – try telling them it’s not worthwhile and they will beg to differ. It’s really about educating people on the science of radiant barriers, not just what’s popular in the eyes of the government.

    4. I am looking into insulating my riding arena but I will not be heating it. Have you had any clients who put radiant heat insulation in their arenas? What were the results?

      1. If you are trying to make the arena cooler in the Summer, you are on the right path. If you are trying to keep it warmer in the Winter, the foil will help some, but the biggest heat loss is due to conductive heat flow – not radiant. Therefore, adding some type of “traditional” insulation will have a bigger impact.

    5. hi Ed,

      please indicate if the radiant barrier thermal break would be enough to insulate an A Frame home that has zero insulation. A roofer is indicating that this would be enough for Pine Az. The climate in the winter dips to 30 degrees.


    6. We currently live in Wyoming where winter temps often get below 0 degrees. Most recommendations for cold climates are to install the radiant barrier directly over the insulation. It makes sense that this would maximize the the potential to keep heat in during the winter and then keep out some of the heat in the living areas during the summer. However, wouldn’t this location of the radiant barrier placement also make the attic even hotter (for instance if I needed to go do some maintenance work, etc in the attic during the summer, it would be even hotter than before as the heat is reflected off the barrier placed on top of the insulation and back into the attic, correct?)

      1. Craig, yes the attic could be a little hotter. But, the key is to have good attic ventilation and move some air through the attic to keep it cooler. All the heat that WOULD have been absorbed by the insulation is now being reflected back towards the roof. This is a small price to pay for the benefits you get 99.9% of the time you are not in the attic.

    7. I’m looking to build my first cabin, about 150 sq ft in upstate NY where it can get below zero. The loft space is very important as is all space in such a small configuration so what would you recommend to insulate a cabin like this?

      1. I’d recommend combining radiant barrier and r-value insulation (foam/fiberglass/etc.) in the walls and ceiling. You can see how to do this correctly so you can fit all layers and get the best results here: How to Install Radiant Barrier in Exterior Walls and How to Install Radiant Barrier in a Cathedral Ceiling. The process and layers are the same for both areas, the pages just focus on a different angle depending which part you are installing in. Your goal is going to get the walls and ceiling air tight and well insulated, you can do both of those with this method.

    8. Hello Ed,

      could you please recommend me how to use the radiant barriers (and some insulation) in my old cold house made of fired bricks?
      My priority is to keep the house warm in winter. I have two masonry stoves in the house so the primary resource of heating is the radiant heat. And I’d like to keep this radiant heat in the house during winter and reflect (keep away) the radiant heat from the sun in summer.
      When I use one foil that will have the airgaps on both sides will it reflect the radiating heat from both sides, from inside (heat from the stoves) and from outside (heat from the sun)?
      And what is the best way to insulate my house this way? Where to put the traditional insulation in the attic, floor and walls?

      Thank you!

      1. For any climate that is installing radiant barrier on the attic floor over insulation, we recommend our SuperPerf™ radiant barrier foil which is designed for maximum breathability and performance. This is probably the easiest method to install Radiant Barrier AtticFoil™ is to lay the foil out OVER the existing insulation on the attic floor. This method can be used in any climate, though it historically has been most popular in colder climates. This install process is usually pretty simple and quick in most attics. It is typical for two people to easily install radiant barrier into an average size home in just a few hours: Laying Foil On Top of Insulation on the Attic Floor

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