Doors: More than Meets the Eye
/Many people view doors as nothing more than a slab of wood with some metal hinges. However, the type of door you have can greatly impact things like home security, frequency of repair, and heating and air conditioning costs. There are three options for wood doors: hollow core, solid core, and solid wood.
Hollow core
A hollow-core door has an interior made of cardboard laid out in a honeycomb pattern. This core is surrounded by a wood veneer, which is essentially a shell or a "skin." These doors are not very good at blocking out noise, and they are highly susceptible to damage. However, they are inexpensive and, because they are light and easy to carry, the easiest to install.
Solid core
The solid-core door has an interior made of sturdy material. There are many types of cores, but the three most common are:
Particle cores made from a coarse sawdust that is more dense on the outside than on the inside
Staved lumber cores made from small blocks of wood glued together
Structural composite lumber cores (SCLC) made of flakes of wood randomly oriented and pressed together to add strength
More and more companies are making SCLC doors, because, according to BBR Window and Door Specialist Greg Caplan, they are less susceptible to warping, don’t use any added urea formaldehyde, and are cheaper to make. Like the hollow cores, solid cores are surrounded with a wooden veneer. They are soundproof and sturdy, best used as interior doors, Greg says.
Solid wood
The solid wood door is an assembly of multiple pieces of solid wood. Vertical boards called stiles run along the full height of the door along each side. At the bottom and top, horizontal boards called rails run along the width between the stiles. Some doors may have a third rail in the middle as well. Doors may also have mullions (boards that run vertically between two rails) and muntins (also vertical, complementing mullions). Panels fill in the rest, completing the door. Although they are more expensive, solid wood doors are durable and the most aesthetically pleasing. For this reason, they are commonly used as exterior doors.
Fiberglass
Another option for an exterior door is fiberglass, which has key advantages over wood—the first being durability. Greg points out that fiberglass won’t rot, warp, twist, or catch on fire, so it could last for decades or even centuries. A fiberglass door is also more energy efficient, holding in heat more effectively than wood. Because of the strong, thin fiberglass skin, most of the door's thickness consists of foam insulation. However, some people find wood doors more aesthetically pleasing.
Torrefied wood
One recent innovation is doors made from torrefied wood—wood that has been heated between 400 and 600 degrees Fahrenheit. (Because it is heated in an oxygen-free environment, the wood doesn’t burn.) Superheating the wood removes all sugars, drastically reducing the risk of rotting, warping, or catching on fire. Torrefied wood doors make great exterior doors, and because of their resistance to the elements, they have a 20-year warranty without an overhang requirement. This is far greater than that of a regular wood door, which has a warranty of one to five years depending on the thickness of the veneer and also requires that it be under an overhang. All that durability comes with a price: Greg reports that torrefied wood doors can cost 50% to 100% more than regular wood doors, and there is a limited selection of them. Most customers choose fiberglass doors, which are far cheaper than torrefied wood. However, says Greg, “Some people just prefer wood.”
—Daniel Carr