Turning Up the Heat: Fires Test Performance of Tall Wood Buildings

Wood buildings provide an array of economic and environmental benefits. Interest in capitalizing on those benefits by constructing mid- to high-rise buildings using cross-laminated timber (CLT) is growing. CLT is made from layers of dried lumber boards stacked in alternating direction at 90-degree angles, glued and pressed to form solid panels. These panels have exceptional strength and stability and can be used as walls, roofs, and floors. Additionally, calculations have shown that a seven-inch floor made of CLT has a fire resistance of two hours.

In order for wood structures to rise above six stories without special building official permission, changes to the International Building Code are needed. It’s a tall order, but researchers from the Forest Service’s Forest Products Laboratory (FPL) recently completed a series of fire tests that will address concerns about fire performance of wood buildings and help take them to new heights. Continue reading

High-Rise Wood Buildings: Interactive Map Shows Construction Around the World

It’s safe to say we have a thing for tall wood buildings here at the Forest Products Laboratory.

Dalston Lane is a 121-home development set to open in London this summer.

Dalston Lane is a 121-home development set to open in London this summer.

Case in point: We study what happens to their moisture content during construction, look at how they perform in earthquakes, test fire retardant treatments for their components, host workshops about them and post the presentations for all the world to see, and even sponsor large events, like the Mass Timber Conference happening in Portland, Oregon, this week!

With all that in mind, you can imagine our excitement when curbed.com published an interactive map (swoon!) of all the wooden high-rises in the world, some completed, others under construction or in concept. Scroll through the list or click a number on the map to read about the buildings’ features, see photos and drawings, and find out more via website links.

Even if you’re not quite as obsessed with wood as we are, we guarantee you won’t be disappointed with this cyber-trip around the world to see some truly stunning architecture.

New Technology, Old Problems: Heat Release Research an FPL Mainstay

The following post is adapted from the book Forest Products Laboratory 1910-2010, Celebrating A Century of Accomplishments.

As an early promoter of the use of heat release rate as a measure of relative flammability, John Brenden developed the original Forest Products Laboratory (FPL) apparatus to measure the heat released by a burning material in the 1960s. Heat release research was reliable and effective, and FPL continued to obtain new equipment as better technologies were developed to measure heat release rates.

The cone calorimeter replaced the apparatus from Ohio State University that was employed by FPL researchers in the 1980s.

In the 1980s, the original apparatus was replaced by one from Ohio State University, and 10 years later, was replaced by a cone calorimeter developed by the National Bureau of Standards. Today this organization is known as the National Institute for Standards and Technology. The cone calorimeter is used in investigations into fire-retardant treatments (FRT) for composite materials and fundamental research on the fire behavior of wood.

A cone calorimeter is a laboratory instrument that gathers data ranging from ignition time, to combustion products and, of course, heat release rate. It is used with small samples of flammable material. Its name reflects the conical shape of the radiant heater used in the device.

In addition to their use in evaluating the effectiveness of fire-retardant treatments, test methods for the rate of heat release were critical in the development of models to predict flame spread behavior of wood and times for flashover in the standard room-corner test.

Heat release graphs are still used by FPL researchers to determine the effectiveness of flame-retardant wood treatments.

Today, FPL researchers still use heat release rates to determine a material’s flammability. FPL Research General Engineer Mark Dietenberger, and Laura Hasburgh, a Fire Protection Engineer at FPL, feature an FRT heat release rate graph in their recently published document, Wood Products Thermal Degradation and Fire in the Materials Science and Materials Engineering Reference Module for Elsevier. More information can be viewed here.

 

The Heat is On: Fire Fuels Research at FPL

Where there’s smoke, there’s fire — but where there’s wood, there’s always the chance of fire. Luckily, where wood and fire meet, there’s the Building and Fire Science work unit at the Forest Products Laboratory (FPL).

This CLT specimen survived almost 100 minutes of exposure in a standardized test reaching nearly 1000°C. The unexposed side of the specimen remained at less than 50°C for the entire test.

Throughout its existence, FPL has long been on the cutting edge of fire science. Fire prevention will continue to be a major area of study as wood expands into commercial and high-rise construction.

This unit is charged with researching how wood and fire interact, and help make wood products more fire resistant and in compliance with international fire safety standards. One way to accomplish this daunting task is through the use of flame-retardant treatments (FRTs) — but what exactly do these treatments do?

FPL Research General Engineer Mark Dietenberger, and Laura Hasburgh, a Fire Protection Engineer at FPL, know exactly how FRTs work. Their recently published document Wood Products Thermal Degradation and Fire in the Materials Science and Materials Engineering Reference Module for Elsevier takes an in-depth look at these treatments and explains how they work to keep wood from going up in flames.

Most FRTs delay ignition, reduce heat release, and reduce flame spread. Other possible mechanisms for fire retardancy include conducting heat away from the heat source, endothermic chemical reactions to absorb heat, or the releasing radicals that inhibit combustion. Some flame-retardant coatings can even swell to form an expanded low-density protective film for the material upon exposure to fire. These FRTs are known as intumescent formulations.

For interior applications, Dietenberger and Hasburgh note that water-soluble inorganic salts are the most common flame retardants. These chemicals are combined by researchers in specific ways to optimize a material’s fire performance and reduce individual aspects of a fire. Boric acid, for example, can be added to an FRT formulation to reduce smoldering or glowing.

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FRTs can reduce the heat release characteristics of wood. Above are heat release curves for untreated and FRT Douglas-fir plywood.

Although the FRTs decrease the flammability of a material, they can increase other dangers associated with fire, like the production of smoke or weaken a material’s structural integrity. Fire retardant-treated wood is often more brittle than untreated wood, and some FRTs can cause further losses in strength with continued exposure to elevated temperatures, for example, the roof of a burning building.

FRT research thus is a delicate balancing act, and researchers strive to create FRTs that allow wood to remain both strong and fire-free. Though the heat is on for the men and women from FPL’s Building and Fire Science unit, they have proven they are up to the challenge — continually pushing the limits of FRT with every experiment, and helping to make our wood, and us, safer.

For more information, please see the full article, Wood Products Thermal Degradation and Fire.

Holiday Trees: Go Real, but Water them Well!

Being the tree lovers that we are here at the Forest Products Laboratory (FPL), of course we’re going to recommend real trees for the holiday season.

TREEThe benefits are numerous. While they’re growing, real trees clean the air and provide us with fresh oxygen to breathe. Most Christmas trees are grown on farms (often on soil that doesn’t support other crops), so buying a real tree supports local farm families who plant new seedlings for every tree harvested. And when the new year rolls around, your real tree can be recycled for a new purpose — perhaps as mulch, or something more exciting, like being submerged in a lake to create a fish habitat!

Yet even as we encourage the use of real trees this holiday season, we must remind you to be safe! Christmas tree fires are rare, and well-watered trees pose very little risk. But when real trees are neglected and dry out, they can be consumed by fire in a matter of seconds if a flame or electrical spark gets too close!

Watch this video from the National Instituted of Science and Technology for Christmas tree safety tips and a sobering look at how quickly your holiday could go up in flames.