Why Your Next Door Should Be Fiberglass: Convincing Advantages Over Steel

1. Introduction

Steel is an iron-carbon alloy that is widely used in construction because of its incredibly high tensile strength, low cost, and availability. Steel is the most commonly used door material because of its low cost and fairly high durability, but at a cost. The strength of steel is a double-edged sword. Although incredibly strong, the door skin is easily dented and repairs to steel doors require body filler, sanding, and repainting, which can be costly. Steel conducts heat and cold, so any entry door is Energy Star no matter how well it is insulated. During cold temperatures, frosting or condensation may occur on the inside lock face of a steel door, so it is susceptible to rusting when exposed to water. Steel has a high thermal conductivity, which is about 200 times higher than wood and about 1000 times higher than insulated concrete. High conductivity increases the rate of energy transfer across the material, so during cold weather, steel doors will feel very cold to the touch. Steel doors can also get too hot to touch during extremely warm temperatures. This affects indoor climate control, raising heating and cooling costs.

Fiberglass has been around for many years as well, and was first introduced to the door industry in the late 1980s. It was a durable, low maintenance, cost-effective alternative to steel, and its popularity began to increase. Today, energy concerns along with the availability of a larger number of decorative options has expanded interest in remodeling/repairing with fiberglass-prefinished entry doors. With these options and market demands, fiberglass doors have gained higher preference over steel.

Fiberglass and steel are two materials commonly used in the manufacture of doors. Steel, the most popular door material, has been the first choice of many homeowners and home builders for many years. This material has been commonly called the “builder’s grade” door, mainly because it was the cheapest door available. Although to date you can still purchase these doors for this same reason, the steel door has some severe drawbacks.

1.1 What is Fiberglass?

Fiberglass, created through the process of combining thin fibers of glass with a polymer, is an effective composite building material. For the homeowner, seeing the difference between fiberglass and steel doors really depends on personal taste. While both are durable, fiberglass may be more appealing visually. It is lighter than steel and easier to install, yet is very strong. Manufacturers offer a wide range of styles and finishes ranging from realistic wood simulation to a high tech look. While appearance is important, a door’s chief function is security. Steel doors feature a rigid foam core that adds to their strength making them the most secure option for entry doors. This same design also helps to make steel doors energy efficient, as they are able to keep heat in during the winter and out during the summer. Steel doors also maintain their value. They will not warp and are easily repaired with an auto body repair kit. However, while durable, over time they may develop signs of rust or corrosion unless they are well-maintained. Fiberglass doors are this maintenance free alternative to steel. They require no special maintenance aside from an occasional coat of paint or stain. They are energy efficient, resisting denting, warping and cracking and are impervious to rust. Step-by-step you may have decided which door is greater in its significance. Don’t worry, for over time your opinion may change. This article provides an in-depth analysis of the advantages of fiberglass over steel, perhaps giving you reason to go back on your decision.

1.2 What is Steel?

Let’s look at steel; while it has been around for quite some time and has undergone many advances and changes, it is still the same old material and many simple changes have been made to the methods of using and fabricating steel that have been more as a “quick-fix” than a solution to the real underlying problems associated with steel garage doors. Traditionally, steel doors have been made from a series of panels, designed to allow for easy manufacture and assembly, simply by screwing the panels together and to the front of the door. Steel panels are quite flexible than can be dented, or pushed in, with only a moderate amount of force. This can be both good and bad as it is a simple way of getting design flexibility, but is very difficult to repair, as usually, one can find no single part of the panel that is firmly damaged. While there are a variety of steel types and gauges, the most common material is a very thin 28-gauge that is then coated in a baked-on polyester paint and often embossed with a wood grain or stucco texture. Usually a front or backside of a steel panel is coated, and the other side is left only with a primer-coat, an uneven paint thickness can lead to rusting and deteriorating in outdoor weather conditions. If a steel door has been dented, causing the paint to crack or chip off, due to the panel being very flexible, it is near impossible to pop out the dent, and it is far easier to simply replace the panel, eliminating and bending back out, areas where the paint has been cracked or chipped. Steel doors come with a variety of insulation types varying from expanded polystyrene to polyurethane, with no real increases in R-value to costs ratios. Being the most inexpensive insulation type, steel doors provide for a thicker door, with little sturdiness against dents and damage and low thermal efficiency. Any part of a steel door, including hinges, lifting fixtures, panels, screws, handles, etc. are subject to rust and corrosion over time and in exposed weather conditions. Usually steel doors are very heavy and can require a high amount of maintenance to keep them functioning or looking half-decent over time. Commonly replacing damaged steel panels, or repainting and sanding rusted or deteriorated areas can simply become a hassle and an unwanted expense.

2. Advantages of Fiberglass over Steel

The good strength-to-weight ratio of fiberglass gives it the advantage to be a good replacement for steel. Not only is fiberglass easier to install, but over a long period of time, it is more cost-effective to have a structure made from fiberglass as it is likely to incur lower maintenance costs, and in some cases, may have a longer life. This is a very important advantage that fiberglass has over steel in the present time where the maintenance and replacement costs of structures have become a major concern.

One of the most important advantages that fiberglass has over steel is its lightweight. This is because the density of fiberglass is around 1700 kg/m³ and that of steel is around 7850 kg/m³. That means steel is approximately 4.6 times heavier than fiberglass. Therefore, considering equal volumes of the two materials, the part made from fiberglass will weigh approximately 1/4th that of the same part made from steel. This provides many advantages. The fiberglass part will be easier to transport, it will be easier to install, and in many cases, it will be more cost-effective to have a part made from fiberglass as it may not require any special supporting structures, as compared to the same part made from steel.

Fiberglass is proving to be a very versatile material and is being used in a number of applications. Besides its lightweight and durable features, it has also proved to be a very good insulator and chemically resistant too. Therefore, it is being accepted today as an alternative to other materials (like timber, mild steel, stainless steel) in many applications like ladders and platforms, walkways, handrails and gratings, and cable tray. The most common material that is being replaced by fiberglass is steel. And there are many advantages that fiberglass provides over steel.

2.1 Lightweight and Easy to Install

Fiberglass bodies are often installed using the same methods as the original equipment (OE) body – bolting the body to the chassis. The relatively simple installation process consists of positioning the body, drilling holes in the floor, bolting the body to the floor, and installing the wiring harness. Steel bodies require a more complex installation process, as they are welded to the chassis to prevent body movement and rattles due to the “oil can effect”. Oil canning occurs when a flat surface is bent in and out to produce a rippling effect. This causes dents in steel bodies due to impact and is likely to occur when stepping on unsupported areas of the floor. The only way to prevent oil canning is to weld additional bracing to the underside of the floor, adding to the complexity and cost of installation. Any hole drilled in a vehicle body is a potential source of water and salt entry, and thus corrosion of the floor. Another advantage of fiberglass is the complete elimination of floor drilling.

Fiberglass is much lighter than steel, allowing for easy transportation to the work site and also installation. A crew of two can easily install a fiberglass truck body. Steel bodies are very heavy and usually require special equipment to load and install, as they often weigh several hundred pounds more than a comparable fiberglass body. This extra weight also greatly affects fuel economy. Every 100 pounds increased vehicle weight results in a 1-2% reduction in fuel economy. At today’s fuel prices, the extra weight of a steel body can cost hundreds of dollars more per year in fuel costs to operate the vehicle.

2.2 Durability and Longevity

Steel doors are known for their strong, durable nature, but they are not invincible. The durability of steel is compromised over time when faced with constant wear and tear from the elements, as well as everyday usage. Corrosion and rust often eventually overcome steel doors, making them unattractive, dysfunctional, and insecure. Unlike steel, fiberglass is resistant to wear and tear from weather and other exposure. Fiberglass doors can often outlast the homeowner. Fiberglass is 8 times as insulating as steel. Fiberglass doors can be produced to look like wood and last a lot longer than wood doors. Fiberglass doors resist dents and pressure far better than steel doors. This means the privacy and appearance of your fiberglass door will remain untouched in spite of harsh or frequent use. A fiberglass door is the best choice for long-lasting performance.

2.3 Low Maintenance Requirements

Fiberglass building products are very low maintenance and moderately priced. When compared to wood and steel, its strongest competitor, fiberglass clearly wins out as the least expensive over time. In relation to wood products, the additional cost of fiberglass is soon negated by the long-term savings in reduced maintenance, repainting, and replacement costs. It is often thought to be approximately equal in value to PVCu products, but here again fiberglass wins the day on long-term cost effectiveness. Unlike steel products, fiberglass will never corrode. It is impervious to rot, mildew, mold, and insect attack. The long-term effects from the environment, pollution, and ultraviolet radiation also have little effect on the physical properties of fiberglass. In comparison, the protective coatings on steel products can be arduous to maintain and the occurrence of scratches and exposure of raw steel can incite substantial rusting and steel decay. For those who have pools or live near the coast, the detrimental effects of salt air on steel provide an additional reason to choose fiberglass.

3. Comparing Performance

Fibreglass doors are made using polyurethane foam cored with fibreglass. When it comes to stability and energy efficiency, fibreglass doors are more durable and resist wear and tear much better than steel. There are additional benefits compared to steel doors, such as its wide temperature tolerance range. Steel doors can dent and show imperfections, and if the paint finish on a steel door is abused, the door could begin to rust. Fibreglass doors can withstand extreme heat or cold more effectively than steel and are not susceptible to rusting. There is a test that simulates the effect of a 25-year aging process by artificially aging doors in a hot and humid test chamber. The fibreglass doors tested were the only ones able to pass this test. This effectively proves that fibreglass doors, on the whole, have a better aging process and temperature tolerance than steel doors. The polyurethane foam in fibreglass doors also provides major benefits when it comes to sound insulation. This provides fibreglass doors with superiority in tasks like reduction of noise pollution where steel doors tend to be good conductors and transmitters of sound. Both steel and fibreglass doors are good in the category of security, but fibreglass doors have a resistance to denting, which means that fibreglass doors can maintain a like-new look longer than steel doors. This also effectively means that with its durable properties and better wear and tear resistance, fibreglass doors can have a longer life than steel doors.

3.1 Energy Efficiency

When it comes to conserving energy, fiberglass is a sound investment. Fiberglass and steel each have a different rate of thermal conductivity; fiberglass has such a low rate that it is not a measurable value. Steel on the other hand, transfers heat and cold rapidly. This occurs because steel is a conductor and fiberglass is an insulator. According to the University of Saskatchewan, “Fiberglass will maintain a temperature of 2 degrees Fahrenheit higher than the outside temperature without any heat source.” Although a number was not given, it was mentioned that fiberglass could actually create a temperature without a heat source. This is definitely energy efficient considering the same would be true for warm temperatures in that fiberglass would keep the heat out. Steel on the other hand has a high rate of heat transfer. According to the Fiberglass Ducts Design and Construction manual, “Heat gain of 20 BTU/hr will occur for each square foot of R-1 insulated metal duct surface when carrying air at 7 degrees C (45 degrees F) when compared to 7 degrees C air surrounding the duct.” Having an insulator like fiberglass can save on air conditioning costs because the furnace or air conditioner will not have to operate due to heat loss or gain from steel ducts. Fiberglass will maintain temperature with less than half the energy input/loss as compared to steel. This is a result of reduced BTU loss from insulation reduction. Much the same is true for a steel door versus a fiberglass door. With the implication of energy conservation laws such as California’s Title 24, a door that meets these standards may be required for new construction. Steel doors will lose and gain heat far too rapidly to meet these standards without costly insulation modifications. A fiberglass door is an efficient solution to this problem as it meets the requirements without the need for additional insulation. Evidently, steel doors will cost more to operate if the home’s heating or cooling system is used frequently.

3.2 Sound Insulation

Due to the incompatibility of STC upgrades with steel doors, the door will cost more to the consumer and still fall short of the naturally high sound insulation capabilities of a fibreglass door.

Steel doors must be filled with a high quality gasket and a polyurethane foam to increase sound insulation and meet STC requirements. Unfortunately, polyurethane foam has little effect on improving sound insulation. Gasketing is effective if it is of good quality and not damaged, but it will not compensate for the lack of mass and density in steel. Therefore, even with added sound insulation components, steel doors will still not match the sound insulation capabilities of a fibreglass door with no added materials.

Fibreglass doors have a natural advantage over steel doors in sound insulation. The nature of the materials themselves gives fibreglass more mass than steel. Because sound transmission is best reduced by heavy, dense materials, a heavier fibreglass door will provide better sound insulation. High density will also provide better sound insulation by impeding the vibrational energy of airborne sound on its journey from one side of the door to the other. This is accomplished by the loss of sound energy due to internal damping within the material.

Today’s tighter homes, in fact, have increased the necessity of good sound insulation for both exterior and interior doors. Although it is not possible to stop all noise at the door, an increase in the door’s Sound Transmission Class (STC) will provide a noticeable reduction in the noise level. STC is an integer rating of how well a building partition attenuates airborne sound. High STC values represent effective sound insulation.

Noise abatement is a critical factor to consider when selecting a new door. As the reuse of urban land intensifies and the number of vehicles and airplane flights increases, our environment becomes noisier. The intrusion of noise into a dwelling can be extremely disruptive to a busy home life and adverse to the home’s value. On the other hand, the absence of appropriate sound insulation on an interior door can be equally disruptive to a home’s environment. In either case, the door is an important element.

3.3 Resistance to Corrosion

Corrosion of metal is a huge test, being that carriage house doors are installed in some pretty harsh environments, from the coast to heated indoor swimming pool areas, to climates where road salt is used, to our mountain community where the doors are subjected to acid rain. Rust on steel doors is a tough repair and unsightly on wood doors. Hardware will stain the door below, reflecting the placement of the fasteners. Rust around fasteners will cause steel or wooden doors to delaminate from the force of the rusting oxidized fastener. Fiberglass doors are impervious to rot and, concerningly, do quite well in harsh corrosive environments. However, when drilling through the fiberglass, care must be taken to seal the bore hole with an epoxy plug to prevent rusting of the door.

Frp doors and windows have long had a “better than” and not an “as good as” reputation when compared with their fiber reinforced plastic alternative, steel. Imagine the dismay felt by many when studies proved that fiberglass windows left over from the last decade that had not been maintained had become discolored, and the fix was usually some sort of sanding or abrasion followed by a paint job. During the past ten years, the finish (paint) has really evolved, improving the product’s resistance to UV rays and nearly eliminating the chalking and discoloration problems.

3.4 Design Flexibility

An extension to this process is injection molding using SMC. This is a similar process to above but using a machine to inject the compound into the mold with higher volume and lower in-mold finishing costs. Development in this area is rapid with new material compounds and more efficient machines making better processes. An example of this can be seen with the automotive industry. Many cars which were originally produced with metal parts are now being produced with composite parts. Often the initial reason is cost, but the volume required pushes manufacturers to develop new processes to make it more cost-effective.

One of the key strengths of composites is the ability to mold complex shapes that would either be impossible or cost prohibitive to produce in metal. There are three key processes that allow flexibility in design. The first and most common is matched die molding. This process can be compared to injection molding plastic. The method uses male and female dies to form the shape of the final product. Fiber reinforcements are placed into the bottom die and resin is applied. The top die is then lowered and pressure is applied to force resin through and around the fibers, creating a new part. This process can be automated and is capable of high-volume complex shapes and detailed parts.

Design flexibility in composites can be defined as the ability to mold and manufacture a product in a variety of shapes and still maintain its unique properties and performance advantages. This is one of the traditional benefits of fiberglass, which has a number of processes to achieve this goal. This section will define those processes and go on to discuss the developments in this field and potential future applications.

As we at Today’s Entry Doors pride ourselves on delivering exceptional service and quality craftsmanship, we invite you to experience the difference firsthand. Say goodbye to the frustrations of navigating big-box stores or settling for subpar contractors. Our dedicated team is here to transform your entryway into a stunning focal point that enhances your home’s beauty and security. Take the first step towards a seamless door installation process by reaching out to us for a free consultation today. Your dream door is just a click away: Contact Us

References:

Akkerman, R., Bouwman, M., and Wijskamp, S. “Analysis of the thermoplastic composite overmolding process: Interface strength.” Frontiers in Materials, 2020. frontiersin.org

Bhong, Mahesh, et al. “Review of composite materials and applications.” Materials Today: Proceedings (2023). [HTML]

Fu, Y. and Yao, X. “A review on manufacturing defects and their detection of fiber reinforced resin matrix composites.” Composites Part C: Open Access, 2022. sciencedirect.com

Yang, Chunxia, et al. “Lightweight and strong glass fiber reinforced polypropylene composite foams achieved by mold-opening microcellular injection molding.” Journal of Materials Research and Technology 14 (2021): 2920-2931. sciencedirect.com

Mokarizadehhaghighishirazi, Majid, et al. “Investigation of microstructural and mechanical properties of weld lines in injection‐molded short glass fiber‐reinforced polyamide 6.” Polymer Composites (2024). [HTML]

Gao, Ruoxiang, et al. “An integrated simulation method for analyzing mechanical properties of injection molded fiber‐reinforced polymers.” Polymer Composites 43.7 (2022): 4530-4543. [HTML]

Hunt, C. J., Morabito, F., Grace, C., Zhao, Y., and Woods, B. K. S. “A review of composite lattice structures.” Composite Structures, 2022. researchgate.net

Um, H. J., Lee, J. S., Shin, J. H., and Kim, H. S. “3D printed continuous carbon fiber reinforced thermoplastic composite sandwich structure with corrugated core for high stiffness/load capability.” Composite Structures, 2022. [HTML]

Wazeer, Adil, et al. “Composites for electric vehicles and automotive sector: A review.” Green Energy and Intelligent Transportation 2.1 (2023): 100043. sciencedirect.com

Lalegani Dezaki, Mohammadreza, and Mahdi Bodaghi. “Soft magneto‐responsive shape memory foam composite actuators.” Macromolecular Materials and Engineering 307.11 (2022): 2200490. wiley.com

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