Report from the ASHRAE Buildings Conference.
December 16, 2025
By Patrick Flannery
ASHRAE and Oak Ridge National Laboratories is hosting its Building XVI Conference in Clearwater, Fla. The event happens every three years and is located at the lovely Sheraton Sand Key Resort, just steps from the beach. Not a bad assignment for a Canadian in December. It’s also a fun assignment because the conference is packed with dozens of the top building science experts from all over the world and you can spend all day hearing about the very latest research and ideas that will inform how we build things for years to come. About 100 attendees were at the opening plenary.
Here’s a quick look at just some of the discussions from Day 1.
From left, Sam Rashkin, Andre Desjarlais and Angela Kalagasidis.
Sam Rashkin a senior researcher at ORNL, outlined their efforts to assist the U.S. Department of Energy to create a strategy to encourage Americans to do energy-efficiency retrofits on their homes. It was interesting because authorities at Natural Resources Canada have been tasked with the same mission and have responded with things like the Market Transformation Roadmap. It may say something about the differences in culture between our two countries that NRCan’s plan is heavy on tightening code requirements and asking industry to do the R&D to develop higher-performing products, while the DOE plan seems much more focused on public persuasion and communications.
Next up was Angela Sasic Kalagasidis from the Chalmers University of Technology in Sweden. She looked back at 21 years of discoveries from modelling hygrothermal effects. The first was an investigation into the different effects of heat rising into an attic versus air pressure being balanced between the heated and unheated areas. Researchers found that a pressure differential forcing heated air into the attic didn’t make much difference to the building’s energy use, but did increase the amount of moisture in the unheated space. Another study noted that long, narrow air channels in wall cavities draw warmer moist air from the ground level to the top of the wall where it cools and condenses, leading to mould and water damage. Another model was able to look at masonry and detect signs of degradation and weathering, predicting where and when it would need maintenance or replacement. Advanced modelling is also now able to evaluate the hygrothermal behaviour of materials, predicting how they will absorb water and what their saturation levels will be. They can also predict dimensional changes from humidity due to shrinking, growing or warping.
Phillipe Vincent-lamarre from the University of Ottawa showed research into vertically mounted wood cladding that explored three different furring systems: a grid pattern, straight horizontal supports with no vertical members, and diagonal. The grid allowed the most air exchange throughout the wall cavity, the horizontal strips the least with the greatest temperature gradient from top to bottom. Diagonal furring was similar to the horizontal, even with gaps left in the struts to allow air to pass. The implication here was that horizontal and diagonal furring decreases convection in the wall cavity, preventing trapped moisture from drying and resulting in poorer hygrothermal performance.
Wahid Maref from the University of Quebec spoke about their research into the hygrothermal effects of reflective insulation in attics, comparing black roofs to “cool” roofs that are a lighter colour to keep them from heating up as much. The convection currents in an attic cavity are quite different depending whether heat is entering through the roof or rising up from the space below, Maref found, and convection patterns are dynamic, changing as the space warms and cools. Reflective foil on the inside surface of the roof insulation performs better when heat is penetrating through the roof, and is therefore most effective with black roofs and sunny conditions. The choice of a black roof or cool roof does not appear to importantly affect moisture in the attic, nor does reflective insulation. The choice of a cool roof or black roof has the biggest impact on cooling loads, with cool roofs making loads 2.4 times lower in the Phoenix, Ariz, study and 17.84 times lower in the Vancouver study (though the Vancouver cooling load numbers were comparatively small overall). However, heating loads rose 40 percent with a cool roof, suggesting black roofs are best for cold climates and cool roofs better in hot climates.
Kieren McCord of Pacific Northwest National Laboratory talked about their large market survey of consumer attitudes and behaviour toward building envelope upgrades. The survey of 10,000 Americans found air sealing was the most popular energy efficiency upgrade and adding triple-paned windows the least popular. Higher incomes, higher household energy costs, older owners and older homes all increased the likelihood of doing upgrades. The most consistent drivers of the decision to upgrade included the appearance of the upgrades, broken or obsolete existing features and a desire to improve the home value. Upfront cost was the biggest barrier to upgrading. The biggest factors influencing which products were selected was friends and family recommendations, the availability of the products at local big box stores and the ability to install the product themselves. The complete dataset from the study is available to the public.
John Peavy of Home Innovation Research Labs discussed his group’s project to upgrade a 1970s-era three-storey multi-unit in New York state using experimental pre-fabricated wall panels to replace the existing wood cladding and brick veneer. Any renovation contractor would feel his pain as he described a series of nasty surprises as they removed the facade, revealing moisture-swollen particle board, veneer used to make fake corners on the foundation, un-plated wiring, broken hydronic heating valves and in-wall air conditioning units that couldn’t be replaced in budget. Still, they overcame it all and measured an R44 insulating value in the finished walls.
Andre Desjarlais, residential program manager at ORNL and a founder of this conference, took the podium to describe ORNL’s Building Science Advisor, a free online tool that models and estimates the hygrothermal performance of wall assemblies. Users select their climate zone, new construction or renovation, then fill in the details of their wall such as cladding, air spaces, insulation, vapour barrier, etc. The software produces a graph representing the assembly’s thermal, moisture-resistance and mould-resistance performance. The tool is freely available for public use.
