The thermal benefits of heavy timber are often an understated advantage in its use as a building material. On a basic level, timber enhances indoor comfort due to its cellular structure and mass. Dense species such as oak and Douglas fir are effective heat sinks, absorbing warm air and slowly releasing it, particularly in comparison to steel, which has nearly zero insulating properties. Considering the additional benefit of timber’s hygroscopic nature, allowing it to regulate indoor humidity and mitigate mold risks, timber becomes a powerful choice in addressing sustainability, energy efficiency, and indoor comfort.

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.