Heating and Cooling Mass Timber Buildings

There’s a reason why people often refer to urban centers as the “concrete jungle.” Standing in the middle of any city, you only need to look up to see large towers of concrete looming above. Not surprisingly, all that concrete comes with a cost. For example, in the case of New York City, the cost impacts both the atmosphere above the city and the ground below it. 

Researchers at the United States Geological Survey (USGS) estimate that on the 300 square miles (777 sq km) on which New York City sits, there rests an estimated 762 million tonnes (1.68 trillion pounds) of concrete, glass and steel. Ultimately, all of this weight is causing the land beneath it to sink, but as much as 1-2mm a year. 

In addition to its shear mass weight, concrete also has a high carbon footprint. The process of manufacturing cement requires heating limestone and clay to extremely high temperatures, which releases excess amounts of carbon dioxide. A Princeton study notes that concrete is the “highest consumed product on earth besides water” and contributes more than 4 billion tons of CO2 annually. 

In the push to create more eco-friendly and sustainable building materials with the goal of slowing global warming, mass timber buildings have risen in popularity. Popular in Europe, we’re starting to see broader adoption throughout North America, with cities like Vancouver, Portland and San Francisco. 

What is a Mass Timber Building?

“Mass timber buildings are constructed with large pre-manufactured, multilayered solid wood panels resulting in solid timber floors and walls typically ranging from 5-12 inches in thickness.” —American Wood Council

When the primary load-bearing structure is created from solid or engineered wood, it is considered mass-timber. According to the WoodWorks Innovation Network (WIN) there were more than 2,000 multi-family, commercial or institutional mass timber structures in progress or built as of December 2023. 

It’s a construction material that’s growing quickly in popularity, largely because of its ecological benefits, structural integrity, speed of construction and overall thermal performance. Wood is a natural resource, compared to limestone, sand and other materials used to produce concrete. 

“Say the typical steel and concrete building has an emissions profile of 2,000 metric tons of CO2,” said Andrew Ruff, of Connecticut-based Gray Organschi Architecture in an article for YaleEnvironment 360. “With mass timber you can easily invert so you are sequestering 2,000 tons of CO2. Instead of adding to climate change you are mitigating climate change. That’s the goal.”

But the environmental benefits go beyond the design. Because wood is a natural insulator, mass timber buildings also excel in energy efficiency. Where concrete absorbs heat, mass timber buildings allow only the air inside the building to be heated or cooled. This makes it increasingly important to use heating and cooling systems that react quickly to maintain optimal temperatures, such as low-temperature hydronic systems. Otherwise, this efficiency (and cost-savings) is wasted. 

Our Briza fan coil line is one of several hydronic options that offer ideal heating and cooling for mass timber construction. With three options based on the desired output, the Briza 12, 22 and 26 provide superior heating and cooling that reacts quickly, uses minimal energy and has become a go-to choice for maintaining optimal temperatures in a mass timber building. 

A huge advantage of using terminal hydronic fan coils is they can be “sill mounted” underneath windows, leaving the ceiling clean and uncluttered. When the building has a beautiful mass timber ceiling, you don’t want to clutter it up with sheet metal ductwork. Sill mounted fan coils are ideal for this, and the Briza 22 specifically has found itself in a sweet spot in terms of cooling capacity and size, as it’s able to provide up to 4 tons of cooling while being no more than 9” deep.

On projects where mounting a fan coil in the ceiling or underneath windows is not possible, the Jaga Clima Canal range is the ideal solution. Again, keeping those beautiful ceilings clean, now all the terminal heating and cooling equipment is placed within or on top of the floor. With the Clima Canal 19 (7.5” tall) we can get 1 ton of cooling in 6ft length. Plenty of capacity for a hydronic fan coil in the floor. A popular solution for mass timber.

Hydronic solutions also offer a safe solution for mass timber buildings. Where VRF systems have the potential of leaking noxious gasses which can be harmful to occupants (and have a very high GWP when leaked), hydronic systems pose no potential safety risks to building occupants as it’s just water.  Further, because hydronic components are not proprietary, they can be integrated with other building system software and technology and easily replaced when needed.

Energy Efficiency at the New San Mateo County Office 3 (COB3) Mass Timber Project

Approximately 600 San Mateo County employees recently took occupancy of a new 208,000-square-foot mass-timber building in the heart of historic Redwood City. It’s the first civic building in the country with Cross-Laminated Timber (CLT) construction and a Net-Zero energy design. 

As a Net Zero building, it will produce all of the energy required to operate the building. Photovoltaic (PV) panels on the building’s roof and that of the adjacent parking garage will generate the energy. Our Briza 22 units ensure optimal efficiency as they’re located beneath windows to provide heating and cooling. 

It was key for the architect to find a unit small and quiet enough to be mounted within the window sill structure. The Briza 22 proved to be up to the task in open offices and all the smaller offices/meeting rooms. For spaces where there is no window sill (floor-to-ceiling glass), the Clima Canal 19 was mounted on top of the floor to provide adequate heating and cooling load while being quiet enough for all occupants.