Founder | BPI® Energy Auditor Certified Professional
Did you know that black asphalt roof shingles absorb almost all heat radiating from the sun?
This roofing material can reach a whopping 170 degrees on a sweltering day. However, a radiant barrier can block most of that heat before it has the chance to enter your home.
However, some skeptical homeowners doubt whether the barrier can reflect heat at all. Some think it makes roof shingles hotter and decreases the roof’s lifespan as a result. This article will investigate this skepticism regarding the effectiveness of radiant barriers.
What Is A Radiant Barrier?
Simply put, a radiant barrier is a building material designed to deflect thermal radiation from the sun. As a result, it reduces heat transfer into your attic and home.
The low emittance surface is a thin layer of aluminum foil that prevents heat absorption that can turn your home into a furnace. The pre-laminated layer can reduce the temperature in your attic by up to 30°F. This reduction will lead to a cooler home, which can diminish your electricity bill significantly as well.
In most cases, radiant barriers are installed under roof sheathing or rafters. However, many homeowners don’t go for it because they are unsure how the barrier works.
How Do Radiant Barriers Affect Roofs and Shingles?
Roofs with a radiant barrier underneath experience only a slight increase in temperature. The nominal increase is nothing to worry about since roofs are constructed to withstand temperatures well above maximum levels. So the short answer is, they don’t.
Factors that Affect a Roof’s Temperature
Two factors come into play regarding the maximum temperature a roof can withstand—it’s color and ventilation.
The former is a huge factor. For example, dark-colored roofs or shingles can quickly become 20 degrees hotter than their lighter counterparts.
Ventilation levels are affected by wind movement under and over the roof, which affects the roof’s temperature.
A cool roof emits less radiant heat than a hot one. So you don’t need a radiant barrier if your roof doesn’t get hotter than external temperatures. It’s why homes that have tree coverage or are shaded by anything else don’t need barriers as much as those exposed to the sun’s radiation constantly.
As per these variables, every roof reaches a point where the max temperature stabilizes. This happens when the heat loss from radiation, air temperature, and ventilation comes into equilibrium from the heat absorbed from the sun. The phenomenon usually occurs when a roof’s temperature reaches 140 to 150 degrees.
What a Radiant Barrier Does
A radiant barrier will only increase the roof’s temperature by two to 10 degrees maximum. This is because the heat it absorbs typically bounces off the roof deck, causing the roof to emit more heat upwards rather than both upwards and downwards.
At this point, the roof is still getting hotter and losing heat. So the barrier is just redirecting most of it away from the attic and its insulation.
To understand what’s happening, picture a room with a single light bulb hanging in the middle of the ceiling. It emits light and heat in all directions while lighting up the space when it turns on.
However, if you add a reflector to the bulb, most of that energy (both light and heat) will be directed downwards. That is what a radiant barrier does.
It doesn’t reduce the amount of heat a roof gets; it only redirects light and heat. Instead of radiating in all directions, heat is radiated upward and away from the attic because of the barrier.
Your roof doesn’t ‘bake’ under the heat because the temperature increase is minimal, and you will save money on your utility bill.
Who Should Get A Radiant Barrier Installed?
The following are some instances in which a radiant barrier is well worth the investment:
You Have a Poorly Insulated Attic
If your attic is poorly insulated, a radiant barrier will do wonders to maintain the internal temperature at comfortable levels.
Unfortunately, this is a common issue in older homes with little to no insulation. In this case, you will save more money in having a barrier installed than getting insulation.
Your Roof Isn’t Shaded
A radiant barrier’s main job is designed for is to reduce heat gain. A roof exposed to the sun completely will get way hotter than a shaded one.
So if you live in the northern hemisphere and your home faces south, get a radiant barrier installed to offset the heat. Besides a house, you can also install it over a barn or outbuildings with poor or no insulation, including buildings with metal roofs that can bake under the sun.
The Attic Doesn’t Have Ductwork
An attic with ductwork remains cool during the summer. However, if you have an older home, chances are you have an unconditioned space.
A radiant barrier can do the job just as well and prove less expensive in the long run. They can reduce the heat in your home and thus reduce the need for energy-sapping air conditioning at the same time.
If the heat transfer between your home and the exterior is relatively high, your HVAC system struggles to maintain a comfortable temperature. This instance is where the radiation barrier proves invaluable. It stops heat waves from moving through your home, thus reducing heat retention by about 10%.
How Climate Affects Radiant Barrier Efficiency
That is not to say a radiant barrier can prove efficient in every scenario. The climate has a significant impact on its efficiency:
Hot climates – You can choose from three types of radiant barriers if you live in a hot environment. They will block and reflect heat keeping the attic cool for days.
Cool climates – Radiant barriers work well in colder climates as well. Besides keeping heat out, they can also retain the heat generated by your HVAC system, so you won’t have to increase it every time the temperature drops. This will lead to savings that you can invest elsewhere, like a college fund.
Mild climates – Radiant barriers are not as efficient in temperate climates. That’s because homes do not require massive amounts of energy to maintain a comfortable temperature. However, a barrier can maintain comfortable homeostasis within the home.
The fact is that a radiant barrier is a wise investment if your monthly energy bill is bleeding you dry. It also makes existing insulation options more efficient by trapping air within fibers, reducing convection heat transfer. Some also block radiation heat transfer.
Both types of insulation work together to maintain the attic’s temperature at comfortable levels and reduce your overall energy costs. As your existing insulation regulates the temperature of your attic, the radiant barrier reflects heat outward.
In other words, you get the best of both worlds.
Tips and Tricks for Radiant Barriers
Once the radiant barrier is installed, you can sit back and enjoy its benefits as it maintains the temperature in your home. But there are some tips that can help you maximize its potential:
- Keep the barrier clean at all times. Attics are magnets for dust. If enough dirt accumulates on the insulation, it will seriously compromise its reflectivity and its ability to deflect heat.
- Not all radiant barriers are made the same. You can get three types: foil-backed, painted and sheathed.
- Each has its own emittance level, reflectivity, thickness, and strength. Buy one after determining which type will suit your home and the climate you experience. A double-sided barrier can easily give you year-long coverage.
- As mentioned before, radiant barriers are as efficient in cold climates as they are in hot ones. But that doesn’t mean you shouldn’t consider additional insulation to keep the cold at bay. A radiant barrier and insulation can work together to keep your home cozy during harsh winters.
Bottom Line
In the end, the climate you experience and your energy bills should determine the type of radiant barrier you get. Since it won’t heat up or damage your roof, investing in this type of insulating technology makes sense.
Consult with your local or regional planning department to ensure you get a suitable option that can also help you save money in the long run.