Using less concrete and more insulation to reduce energy use, the “next generation” of lighter-weight thin precast insulated and architectural wall panels deliver superior thermal performance and are good for the environment, attendees at the recent Canadian Concrete Expo were told.
That was the message delivered by Malcolm Hachborn, one of the seminar speakers at the two-day event in Mississauga, Ont.
A structural and building envelope scientist with more than 40 years of structural design experience in precast concrete structures, he used the term next generation to provide an overview of the evolutions in wall panel systems.
There are four types of precast panels: single wythe precast panels (uninsulated) referred to as conventional precast; double wythe precast panels (insulated) referred to as insulated sandwich panels; metal framed precast panels; and double thin walled precast panels (insulated), DreamWall.
The speaker focused on the last two as examples of the next generation.
Metal framed precast panels have been used for a number of years, while DreamWall is new, having come on to the market in 2022.
DreamWall was invented by Hachborn.
“These are newest technology,” said Hachborn, noting they have higher thermal performance properties and can meet both new energy codes and Passive House requirements.
Weighing about 30 to 35 pounds per square foot, both systems are considerably lighter than single or double wythe precast panel systems, he said.
Among other features, metal framed precast insulated panels have simple connections and continuous insulation.
“They’re ready for drywall, have the same benefits as conventional precast, accept most finishes and have minimal thermal bridging.”
Separate metal and concrete fabrication equipment is required and there has to be separate areas for that fabrication. To allow for correct installation, the metal frame must be fabricated to the exact same dimensions as the precast concrete portion of the panel and the metal frame cannot be twisted or skewed so that the entire precast panels can be installed true to the lines and levels of the building, he said.
Many of the same advantages are inherent with the DreamWall thin wythe insulated panels, which are comprised of two thin layers of concrete with insulation in between them.
Ranging from 250-to-400 millimetres thick, the panels provide “exceptional thermal performance.”
However, “the concrete mix is more complex (than conventional concrete), and requires a particular sequence of material additions, plus high performance batching equipment, and higher technology foam cutting equipment,” he added.
Despite those operational hurdles, the metal framed precast insulated and the DreamWall panels should be considered, said Hachborn, pointing to their sustainability features.
Included in that list are the lower levels of consumption of concrete and materials required in the fabrication.
“Less concrete means less cement. Less cement means less GHGs. Less concrete means less aggregate. Less aggregate means less aggregate extraction.”
Less concrete means less weight, fewer loads and fewer delivery trucks on the road, plus smaller cranes on the jobsite, he said.
With no hoarding required and the windows preinstalled in the panels, erection and installation is also faster than conventional construction.
The environmental benefits are carried forward once buildings are constructed and occupied. As the two wall panel systems provide better R-values, the end result is superior comfort for the owners and/or occupants, lower energy use and less greenhouse gas emissions.
“Lower energy costs mean better return on investment,” he states.
Noting architects “will push colour and texture” and those esthetic options for buildings are ever changing, the speaker also touched on the range of finishes which can also be used. These include formliners, stains and pigments and facing materials such as thin brick, granite and limestone.
“Anything is possible,” said Hachborn, citing ongoing fabricating enhancements that enable architectural precast to be produced in almost any colour, form or texture.
In summing up his presentation, Hachborn left the audience with a number of takeaways. Precast buildings are durable and resilent, have a long lifespan and are considered “premium buildings,” he said.
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