Radiant heating and cooling: The 3.2 million dollar question
I believe a good chunk of the architectural, building and HVAC industry is unaware that a few years ago California’s Center for the Built Environment (CBE, UC Berkeley) got a big cheque to carry out extensive research on radiant cooling and heating systems. How big? Try $3.2M USD. Those dollars came from the California Energy Commission EPIC/PIER program, industry in-kind support and a CBE industry consortium.
The motive to invest in this segment is the California Public Utilities Commission Energy Efficiency Strategic Plan, which states that all new non-residential buildings be zero-net-energy by 2030. That gives it only a few years to prepare the California property management and development industry to achieve significant reductions in energy use. So why consider radiant as one of the solutions?
Over the past decade or so there have been numerous theoretical reports and case studies on radiant conditioned commercial buildings worldwide. The majority have demonstrated radiant-based HVAC systems, along with symbiotic technologies such as dedicated outdoor air systems, offer proven energy reduction strategies. There is also evidence through post occupancy surveys that these systems provide environments perceived to be more comfortable than environments conditioned by air-based HVAC systems.
The CBE has been building an inventory of radiant conditioned buildings from all over the world to demonstrate its growth and acceptance in all climate zones (as shown in Figure 1).
One part of the four-year research project was to interview radiant design experts to determine their approaches; and to gather information from a large inventory of buildings and occupants. This data was then analyzed for energy use and the occupants’ perceptions of the indoor environmental quality (IEQ).
The inventory was comprised of 60 office buildings with 3,892 respondents. Thirty-four of the buildings were air-based HVAC systems and 26 were radiant-based HVAC systems.
It is no surprise that design and control strategies for radiant systems were as different as the number of experts interviewed–demonstrating once again that a fragmented industry is a reflection of its practices.
As much as I want to launch into another rant how the radiant industry promotes unnecessary “customization” I will stick to the plot. The abbreviated version is: the mined data says, despite everything the radiant industry does to shoot itself in the foot, it still comes out on top with lower energy consumption and marginally higher IEQ metrics such as thermal comfort.
Many of us with gray hair have known this just from engineering principles, experience and intuition. The trouble is that the big machine of property development has traditionally worked with a model of lowest development cost for extracting the maximum lease rates economically possible.
Energy and IEQ did not enter the equation because they did not have to. The people holding the leases paid the utilities passing expenses on to their customers; and staff kept their mouths shut about the environment.
Think of the past and present situation this way: when every villager rides a donkey no one knows the difference until someone shows up with a horse. Today, with enough thoroughbred buildings being built, people are starting to see what kind of asses they have really been occupying for so long. In HPAC March 2018 I talked about the Well Building Program and the Living Building Challenges, and even LEED. All of these programs have given birth to high performance buildings that are starting to establish a new benchmark.
The problem we have today is short of massive property destruction from another world war, the inventory of jackass buildings will continue to plague the planet unless they get fixed and repurposed. The good news is we have a new breed to compare them to–we know what the old gray mare now needs to get it up to zero-net-energy.
Adam Muggleton and I have learned that property developers are sitting on a gold mine from our Edifice Complex podcast interviews; that is once they understand that each ‘should be’ refurbished building in their portfolios could be home for renewable energy systems and a cash cow for generating income as a utility. That is why Canadians such as Paul Ghezzi from Kontrol Energy Corporation are setting up the infrastructure to facilitate this shift to community-based energy systems.
This is where radiant systems fit in nicely. Refurbished and new buildings by design will need low loads to meet targets. Those low loads will enhance the efficiency of the boilers and chillers. The pièce de résistance with radiant is how they make those heat engines sing and dance like Broadway stars. You cannot write a better script for an industry known for repeatedly tripping over itself.
That is where the CBE research comes in. One of its outcomes is focused on the, “optimization of radiant systems for energy efficiency and comfort.” It intends to do that by developing “practical design and operation tools and guidelines for radiant systems.” Why? Because its experience from the research in completed installations to date has demonstrated “that controls and operation of radiant systems can be challenging due to a lack of familiarity within the HVAC design and operations professions.”
In other words, when industry insists on experimenting and reinventing the wheel on every project it fulfills its own prophecy with non-optimized, non-standardized systems. Ponder this. If the soufflé of radiant systems in a smorgasbord of buildings can still outperform air systems that are as generic as vanilla ice cream, and if industry got its act together and standardized design processes, control strategies and installation methods, what would happen?
That is the 3.2 million dollar question, isn’t it?
Current conclusions from the research
Buildings are performing far below the design expectations. Approximately 67 per cent of buildings in the research did not meet ASHRAE Standard 55-Thermal Environmental Conditions for Human Occupancy.
Occupants of radiant and all-air buildings have equal IEQ, with a tendency towards improved temperature satisfaction in radiant buildings. That IEQ in radiant buildings is not clearly better than air-based buildings should be a shocking revelation to the radiant industry. Part of this disconnect has to do with non-optimized, non-standardized systems. I would also speculate it is due in part to poorly commissioned or un-commissioned systems.
A randomly selected occupant has a 16 per cent higher chance to have higher comfort in a radiant system versus an all-air system. This is ok but not spectacular. Optimized, standardized and properly commissioned systems should improve this result.
Occupants of radiant and all-air buildings have equal acoustic satisfaction (noise and sound privacy). This is shocking to others and myself but points out the sensitivity people have to sound in buildings, regardless of system type.<>
Robert Bean is a Registered Engineering Technologist in building construction (ASET) and a Professional Licensee (Engineering) in HVAC (APEGA). He is president of Indoor Climate Consultants Inc. and director of www.healthyheating.com; a past ASHRAE Distinguished Lecturer; recipient of ASHRAE’s Lou Flagg Award and ASHRAE Distinguished Service Award; and a member of ASHRAE technical committees 2.1 (Physiology & Human Environment) 6.1 (hydronics), 6.5 (radiant), 7.04 (eXergy) and SSPC 55 (thermal comfort). Bean is also the author of numerous industry courses and seminars covering the building sciences, indoor environmental quality, energy, and radiant-based HVAC systems.
Research on Radiant Systems Technology at the Center for the Built Environment (CBE) University of California, Berkeley <https://tinyurl.com/ydbx9rgb>
Current Practices for Radiant System Design, Center for the Built Environment, May 2017 <https://www.cbe.berkeley.edu/research/pdf_files/Paliaga-CurrentPracticesforRadiantSystemDesign-May2017.pdf >
EPIC, Electric Program Investment Charge. PIER, Public Interest Energy Research
Bean, R. 2012. Très Bien for large scale radiant cooling. HPAC Canada < https://www.hpacmag.com/digital-archives/sept-oct-2012/ >
Karmann, C., Schiavon, S., Graham, L.T., Raftery, P., Bauman, F. 2017. Comparing temperature and acoustic satisfaction in 60 radiant and all-air buildings. Building and Environment 126 (2017) 431–441 < https://www.cbe.berkeley.edu/research/pdf_files/Karmannetall-RadiantAllAir-Oct2017.pdf >
Online map of radiant system buildings shows projects from around the world. < https://tinyurl.com/y8p7yc2w>
Paul Ghezzi – Disrupt or Be Disrupted. Edifice Complex Podcast <https://edificecomplexpodcast.com/episodes/009-paul-ghezzi-disrupt-or-be-disrupted/>
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May 11, 2022