The doors of your home are more than just a way into and out of your house. They’re a critical line of defense for your home, a way to impress your neighbors and guests, and a critical part of your home’s energy efficiency. When choosing between steel vs fiberglass doors, there are many considerations to make, but we here at Karoly Windows believe that fiberglass doors truly are the best fit for the vast majority of homes in Florida.
Why do we prefer fiberglass in this steel vs fiberglass door comparison? Let’s go over several key performance factors for fiberglass doors vs steel doors for residential applications.
Steel vs Fiberglass Doors: Impact Resistance
Let’s start with a category that will tend to favor the steel door: impact resistance. While the exact performance characteristics of steel can vary greatly depending on the specific grade of steel used (basic carbon steel, grade 301, 304, 316 stainless, etc.), steel tends to have incredible resistance to blows without splintering or shattering.
The strange thing is that fiberglass, on paper, has a higher tensile strength than steel, so you’d expect it to be more durable. The tensile strength of fiberglass, according to Income Pultrusion, is 1,000 MPa (Megapascals), comparing favorably to steel’s 250 MPa.
However, steel has better compressive strength compared to fiberglass… According to the Income Pultrusion source, the E-modulus of steel is 210 GPa (GIGApascals) to fiberglass’ 54 GPa. Note: 1 Gigapascal is equal to 1,000 Megapascals.
This makes steel nearly four times more resistant to pressure and impacts than fiberglass. Also, after repeated impacts, steel will dent, but is not as likely to splinter and delaminate as fiberglass.
Fiberglass, unlike steel, will flex with a blow, making it even better at absorbing low-intensity blows without surface deformation. However, fiberglass may delaminate over time if subjected to multiple impacts that strain the limits of its impact resistance.
When it comes to resisting extreme impacts, steel doors will outperform fiberglass ones… as long as they’re properly secured (hinges and door frames may fail before the door itself does).
Steel vs Fiberglass Doors: Thermal Conductivity
Thermal conductivity has an enormous effect on a door’s energy efficiency. One of the chief problems with steel doors is that they’re highly efficient conductors of heat, which gives them an inherently terrible U factor/R value rating—though not quite as bad as aluminum, on average. However, the thermal conductivity of steel can vary greatly depending on the alloy in question.
According to Thermtest, carbon steel has a thermal conductivity “averaging 45 Watts per Kelvin per meter” or 45 W/mK. The same source notes that one alloy of stainless steel has a thermal conductivity of 15 W/mK. That’s a fairly major difference in the two types of steel.
Compare this to the thermal conductivity of fiberglass. As stated by Ztelec Group, “The thermal conductivity of epoxy fiberglass sheet is generally between 0.25 and 0.35 W/(mK).” So, for every Watt of thermal energy a fiberglass door would let through your doorway when shut, a steel door would let through at least 42.857 Watts of energy (assuming the least insulative fiberglass material vs the most insulative steel type).
This makes fiberglass the clear winner for energy efficiency in your home. Considering how hot & humid the climate is in our state, that’s a huge consideration to make. There’s a reason why fiberglass is such a popular choice for home insulation!
Steel vs Fiberglass Doors: Customizability
It’s not enough to have a strong, energy-efficient door. No, you need a door that will mesh well with your home’s aesthetics and impress your neighbors and guests.
Customizability is a huge part of creating visually appealing doors for your home. This is one area where fiberglass doors blow steel doors out of the water!
Many fiberglass doors come pre-made with panels. These indented surfaces in the door can be left as-is to create a visual draw for your door or they can be removed and replaced with impact-rated glass that lets in the light while continuing to protect your home from hurricanes and other hazards.
While it is an additional cost, the manufacturer is still working with standardized panels, so the upgrade doesn’t typically cost as much in fiberglass doors that have panels compared to steel doors that lack them.
To cut into a steel door to add an impact glass panel takes far more specialized tools and materials than the same task would with a paneled fiberglass door. So, the addition of custom impact windows to a steel door may end up costing far more.
Steel vs Fiberglass Doors: Cost
When comparing any material for an impact door, cost will always be a consideration. While it shouldn’t be the only consideration, it is an important one to consider.
The challenge is that the prices of the raw materials to make doors can fluctuate on a month-to-month basis, which is one reason why the cost of a door may go up seemingly at random. A door that costs $2,000 one month might go up to $2,500 the next simply because the cost of goods to make the door saw a sudden increase.
According to Focus Economics, the price of steel in the U.S.A. was about $944 per metric ton on average. Meanwhile, Composite-Tech puts the cost of structural fiberglass at about $1,800-$2,200 per ton (though prices may vary well below that from some markets).
At first glance, the steel seems to be much cheaper… but these prices are specifically by weight and not volume.
As noted by Pelsue: “on average, fiberglass is about 75% lighter than steel and 50% lighter than aluminum.” In other words, a doorway that would require $200 worth of steel to fill would only require about $100 worth of fiberglass to fill, if fiberglass costs twice as much but is a quarter the weight.
That’s just considering the raw materials needed. It doesn’t account for the extra labor or specialized tools that heavier steel doors would require to install compared to their fiberglass equivalents. It also doesn’t account for cost of ownership, as the thermally-ductile steel carries the sun’s heat directly into your home while the fiberglass doors resist the heat.
Speaking of weight…
Steel vs Fiberglass Doors: Weight
Steel doors are massively heavier than fiberglass ones at the same size and thickness. This has several implications for your home’s entry doors.
First, and foremost, it impacts their ease of operation. The heavier a door is, the harder it is for a person to open and shut, and the more likely it is to cause injury when it is accidentally shut on someone.
Second, it affects the wear and tear on the door’s hinges and other opening mechanisms when the door is held in the open position for any length of time. The heavier a door is, the more strain it puts on the hinges, the more likely it is for a hinge to bend out of shape or fail outright (especially if your installer didn’t account for the heavy weight and used cheap, low-quality hardware for your door).
Because of how much heavier they are than fiberglass doors, steel doors are an exceptionally poor choice for homes where occupants or guests might be mobility-impaired, as the added weight makes it difficult for them to open and close, increases the risk of injury, and the likely severity of injuries if there’s an accident.
Get Fiberglass Impact Doors for Your Home!
In the steel vs fiberglass door comparison, we heavily favor fiberglass for most residential homeowners in Florida. As the Sunshine State where so many elderly people live, fiberglass doors just make more sense than steel.
While steel doors may have a higher overall impact resistance than fiberglass ones, fiberglass doors still more than meet the impact resistance requirements of the Florida Building Code (FBC), are safer to use for mobility-impaired residents and guests, have much better energy efficiency, and are easier & more affordable to customize than heavy steel slabs.
Get impact-rated fiberglass doors to complement your vinyl replacement windows by reaching out to Karoly Windows & Doors today!
