Heavy Timber’s 5 Thermal Benefits

Heavy timber’s inherent sustainability, strength, and biophilic properties are well-known and have been discussed in other Mid-Atlantic Timberframes blog posts. An advantage that is perhaps less well-known is heavy timber’s thermal properties and how indoor temperature and humidity can be positively affected when wood is incorporated into a build. Here, we’ll explore the unique thermal aspects of timber and how they can contribute to creating comfortable spaces.

1. Thermal Mass – Timber’s ability to absorb, store, and release heat comes from its porous nature and the way its cellular structure holds small pockets of air. The denser the wood, the higher its thermal conductivity, meaning it’s a good insulator that will hold on to heat. Timber’s moisture content also contributes to its insulating capabilities. Of the more commonly used heavy timber wood types, oak and Douglas fir have tightly packed, denser fibers. These fibers act as a heat sink, so when ambient temps rise, that warmth is pulled from the air, and the wood’s cellular structure warms. It is then slowly released as the surrounding air temperature drops. It’s a natural effect that can help keep a night’s chill at bay inside a timber build.
2. Insulation – While heavy timber doesn’t provide the same level of insulation as dedicated insulating materials like fiberglass or foam, its thickness can contribute to thermal resistance. A larger mass of timber will better insulate an interior. As noted above, the type of wood — due to its density and moisture content — will also determine the amount of insulative quality the timber exhibits.
3. Air Tightness – In our timber frame builds, we use structural insulated panels (SIPs) to create a tight building envelope. These panels consist of polyurethane foam insulation sandwiched between two pieces of oriented strand board (OSB). Combined with proper sealing,  drafts and heat loss are reduced, which makes it easier for air comfort systems to maintain a comfortable interior temperature. This has the added benefit of increasing a structure’s energy efficiency.
4. Moisture Regulation – Timber is hygroscopic, meaning it can absorb moisture from the air, and also release it. In doing so, it regulates the humidity within a building by moving moisture into its cells, then releasing vapor to reach equilibrium with drier air. This process reduces the risk of mold growth and helps to prevent resultant damage to the structure.
5. Thermal Expansion & Contraction – Wood naturally expands and contracts with temperature and moisture changes. However, heavy timber, with its larger dimensions, resists these effects, minimizing the likelihood of cracks and warping in the material.

The sturdiness and strength of heavy timber truly comes from its cellular level. Its ability to hold warm temperatures and expand and contract very slightly make it a resilient material with energy-efficient qualities. To explore all the benefits of heavy timber, contact our team of experts online or by calling 717.288.2460.

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Native to the Pacific Northwest, Douglas fir can grow up to 300 feet tall with a 6-foot diameter, with one tree often yielding thousands of board feet. Here are six reasons why this conifer is the first choice of architects, engineers, and craftsmen in timber construction:

1. Strength & Durability: Douglas fir is a high-density wood with an exceptional strength-to-weight ratio, making it ideal for structural applications such as beams, joists, and columns. Because of its high density, it is resistant to damage and scratches, plus will resist rot and decay for decades. It is also averse to damage by insects, making it a perfect choice for outdoor, weather-exposed applications.
2. Dimensional Stability: Renowned for its ability to withstand large ranges in temperature and humidity, Douglas fir’s resistance to warping and shrinking/expansion is crucial for maintaining the integrity and structural performance of heavy timber construction over time.
3. Workability: Douglas fir is relatively easy to work with, allowing for precise cutting, shaping, drilling, and joining during construction. This workability enhances the efficiency of building processes, especially in crafting large, intricate timber components.
4. Aesthetic Appeal: With its reddish-brown heartwood and a lighter-colored sapwood, Douglas fir is naturally striking, both for interiors and exteriors. The wood has attractive, uniform graining for visual interest — many designers choose to apply only a clear natural oil finish to showcase its inherent beauty, particularly in contemporary design applications. If desired, Douglas fir also holds paint and stain well.
5. Availability & Sustainability: Douglas fir is widely available in North America. It is sustainably harvested from carefully managed forests, making it a preferred choice for environmentally conscious construction projects.
6. Fire Resistance: While not entirely fireproof, Douglas fir has a natural resistance to fire due to its density and minimal resin content. This can provide additional safety benefits in construction applications where fire resistance is a concern.

The Naturally Superior Choice

Over the years, many types of wood have been used for heavy timber beams, most notably the American chestnut until the early 1900s, when an invasive blight reduced their numbers nearly to extinction. And while oak and white pine are now often cited as desirable wood types for timber frame use, Douglas fir is the superior choice thanks to its strength, stability, and availability.

To learn more about the advantages that Douglas fir provides, and to inquire about its use on your next project, contact the experts at Mid-Atlantic Timberframes.

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To keep projects on schedule and running efficiently, utilizing a single subcontractor to handle the entire structural installation is a wise move. Even wiser is to use an experienced timber framing expert who uses only timber instead of wrapping steel with wood for a timber look. If a rustic look is the aesthetic end goal, using timber to cover steel is an expensive and unnecessary extra step. And, with all the advantages of using timber framing, heavy steel can be replaced without compromising the integrity, strength, or resilience of the building.

Additionally, using only timber has advantages in form and function. Curves and other shapes that are difficult for steel can be readily created with timber. Moreover, timber is significantly lighter than steel, reducing the need for heavy machinery and allowing more material to arrive on-site in fewer truckloads. Lower labor costs, reduced fuel usage, and faster construction times typically follow as a result.

Steel is traditionally favored when a wide span needs to be traversed. But while steel does have the strength to cross large voids, a predesigned timber frame can also perform these tasks, able to support a heavy load when crafted by an experienced timber framer who is engaged and involved early on in the design process.

Timber also offers simpler connections for stud framing and engineered floor joists, further exemplifying its efficiencies. Likewise, on-site adjustments and joining up to stud framing are facilitated more easily with timber.

Though steel may be the “usual” material in many builds, those projects that seek to express a natural timber ambience could – and should – use actual timber framing instead of wood-clad steel beams. The warm, inviting atmosphere exuded by natural timber, the exquisite characteristics of the grain and its earth tones, and its sustainable-use qualities all make timber a better choice in many projects. For more information about timber building and to speak to an expert on all aspects of timber frame construction, contact Mid-Atlantic Timberframes before starting your next project.

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Charring Process

Heavy timber’s distinct fire-resistant attribute is its capability to char in a controlled manner when faced with flames, rather than burning through and combusting. As observed and documented over years of research and testing, heavy timber’s behavior in a fire is predictable. When heavy timber is exposed to fire, its outer layer undergoes a charring process, creating a protective barrier. Understanding this charring process is crucial in designing and assessing the fire performance of heavy timber structures.

Insulating Properties

As the outer layer of heavy timber chars, it insulates the inner, unburned wood from the flames. This insulation significantly slows down the progression of the fire, prevents the fire from penetrating deeply into the timber, and provides a crucial advantage in terms of safety and structural integrity.

Predictable Behavior

Unlike some materials that may behave unpredictably under intense heat, heavy timber’s response to fire is well understood. This predictability allows for effective design and engineering, facilitating the incorporation of safety measures that meet stringent building codes and regulations. The National Fire Protection Association (NFPA) and the International Building Code (IBC) provide prescriptive information for heavy timber fire safety within their standards. Recently, the IBC released many revisions and updates to mass timber building height allowances and associated fire safety requirements. Learn more about timber building codes and fire safety regulations in our previous blog post.

Comparative Advantage

The reliability of heavy timber in fire scenarios enhances its appeal as a construction material in various applications. Traditional construction materials like concrete and steel do not possess inherent fire-resistant properties. While concrete may offer better fire resistance than steel, both materials conduct heat more rapidly and can undergo significant strength loss and structural compromise when exposed to high temperatures. Thus, while concrete and steel have their merits in construction, heavy timber’s unique characteristics make it a compelling choice in builds where fire resistance is a critical consideration.

Additional Measures

In addition to the inherent fire resistance of heavy timber, a strategic combination of design, technology, and preventative safety measures further fortifies its protection against fire hazards. Applying fire-resistant coatings to slow the speed of charring, installing automatic sprinkler systems for rapid fire suppression, and implementing fire barriers and compartmentation to contain fires are just a few design and technology examples. Regarding preventative and proactive measures, performing environmental assessments, installing early warning systems, doing emergency egress planning, conducting regular inspections, and coordinating with emergency services contribute to an intentional and comprehensive approach to fire safety within heavy timber structures.

Conclusion

When faced with fire, heavy timber’s unique charring process, insulating properties, and predictable behavior positions it as a reliable choice in construction. The comparative advantage it holds, coupled with additional safety measures available, solidifies heavy timber’s place as not just a building material but a safeguard against unforeseen challenges.

At Mid-Atlantic Timberframes, we’re advancing the art of timber construction, and we’re here to offer our knowledge in addressing any fire safety or building code and regulation questions that you might have. Contact us today to speak with our experts and learn more.

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1. Visual Appeal & Biophilia
   Because of their natural beauty and warm aesthetic, heavy timber beams are often left exposed in buildings. This creates a very distinctive look, but also has positive effects on people’s mood, stress levels, and productivity. This is because of biophilia, humans’ affinity for nature.
   
   The industrial look of steel doesn’t promote the same biophilic benefits or warmth. And while dimensional lumber is also made from wood, it doesn’t offer the same aesthetic as heavy timber and is typically covered in the construction process.
2. Fire Resistance
   It may surprise you that heavy timber offers excellent fire resistance. The surface of timber beams char when exposed to fire, which protects the inner wood and maintains their structural integrity.
   
   Lumber, however, is combustible and does not offer the same levels of fire resistance. As you might suspect, steel is fire-resistant. Depending on its alloy, it will begin to soften around 1000 degrees Fahrenheit, and melt around 2500, which can be catastrophic to the structure.
3. Sustainability & Eco-Friendliness
   Because wood is a renewable resource, captures and stores carbon dioxide from the atmosphere, and leaves less of a carbon footprint when compared to steel, heavy timber and dimensional lumber are the most eco-friendly choices of these three building materials.
   
   Heavy timber has a slight edge over dimensional lumber thanks to its lower embodied carbon level. Embodied carbon is the amount of greenhouse gases resulting from the extraction, processing, manufacturing, transport, construction, use, and disposal of a material. Dimensional lumber’s embodied carbon is higher than heavy timber’s due in part to it requiring more processing.
   
   Steel has a much higher level of embodied carbon than either wood product, and it also creates buildings that are less energy efficient. Because it conducts heat more readily than other materials, steel requires more insulation and more energy usage to maintain comfortable temperatures within a building. Emissions from this energy usage, on top of steel’s embodied carbon, gives it the largest carbon footprint of these materials.
4. Thermal Insulation
   Timber’s cellular structure has air pockets that create a natural barrier against heat and cold. Additionally, heavy timber and dimensional lumber don’t conduct heat and cold to the surrounding insulation as much as steel. These attributes help to reduce the amount of energy needed to heat and cool buildings built with timber and lumber.
5. Structural Performance
   Heavy timber is extremely strong and durable, so it provides excellent structural stability. For example, this timber frame pavilion in Florida was able to withstand the intense winds of Category 4 Hurricane Ian in the fall of 2022, while many structures in the area were completely destroyed.
   
   Steel is also a high-strength material that stands up well to high winds and earthquakes. The structural performance of dimensional lumber in hurricanes and earthquakes, however, varies considerably, depending on the quality of construction and adherence to building codes.
6. Construction Efficiency
   A perk that all three materials boast is that project components can be prefabricated in an off-site facility, then assembled on location at just the right time. Fabrication can be done while the job site is still being prepared, which can shorten a project’s overall timeline and bring a faster ROI. (To learn about this and other benefits of off-site timber frame construction, check out our blog post here.)
   
   If off-site construction is your main priority, you might prefer heavy timber for all of the reasons listed above, but also because it can be more manageable to transport and unload than steel or dimensional lumber. Because of its inherent larger dimensions, your project might require fewer individual pieces of heavy timber than if you were using dimensional lumber. Heavy timber components are also likely to be lighter than those made from steel.

Heavy Timber Makes the Grade

Ultimately, the best building material for your project will depend on a variety of factors, including your budget, location, and design aesthetic. But heavy timber’s visual appeal, performance, and sustainability and efficiency benefits make it an ideal choice for just about any type of structure you’re building.

At Mid-Atlantic Timberframes, we’re constantly striving to advance the art of timber construction, and we’re eager to share our expertise. To learn more about why heavy timber might be right for your project, contact us today, or check out our project gallery for inspiration.

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