I'm always interested in new technologies or approaches to solving problems, especially in the high performance construction world, so when Panasonic reached out to me a year ago to come see their new way of designing HVAC systems, I jumped all over it. The system, called Oasys, had just been roughed-in at their test house in Houston, so I booked a flight and headed to Texas.
What is Oasys?
The idea is to use existing, efficient technologies to design an HVAC system to solve many of the problems of today's high performance homes. The system would provide constant air flow throughout the house at lower velocity than standard systems, replenishing the air in each room continuously, and be responsive to changing conditions in each room. Compared to a traditional HVAC system, this would reduce noise, provide a more even temperature within a room, and have more precise control over the individual rooms.
I was able to walk the house with the builder, Curtis Lawson of Crafted Custom Homes, who did a great job with it and took the time to walk us through everything. As he put it "Ultimately it's about healthy and comfortable living... but you also get the advantage of a highly energy efficient and effective system."
How does it work?
Oasys is built around three pretty basic pieces of technology: mini-splits, bath fans, and an ERV. Mini splits are placed in a dedicated, centralized room where a bath fan per room is mounted to a wall and ducted to their individual rooms. On the opposite wall from the fans is an open, filtered return (MERV 6 filter). The room outside the return is where the ERV (MERV 13 filter) mixes outside air with the existing indoor air. As the bath fans run, the air is pulled through the filtered return, conditioned by the mini-splits, and distributed throughout the house by the fans. These fans run continuously at low speed to replace the air in each room 3.5 - 4 times per hour. Each room in the house has it's own Swidget sensor that can measure the temperature/humidity, indoor air quality, motion, or other factors. Those sensors report back to the system and can request a boost of air from that room's fan if the measured input is outside of tolerances. That additional air helps bring those levels back to normal.
What else do you need?
It's important to note that this system isn't set up to be used in leaky homes that are under insulated. The home has to be well-insulated and a good bit better than code when it comes to air tightness (although still not difficult to do on a new build). You also need a centralized location for all of the equipment, be it in the middle of the home at a living level or in a conditioned attic or crawl space. During the design phase of the home, Panasonic will work with the project's architect to create the space needed for the equipment and air mixing and do the modeling necessary to properly size the room and equipment.
The PROs
The Oasys system is incredibly energy efficient. The main components are mini-splits and bath fans which are some of the most efficient products in the HVAC world.
Using existing and simple technology means it's easy to install, maintain, and repair. If one of the fans breaks, the average homeowner could swap it out for a new one.
The continuous flow of air, combined with the outside air from the ERV, means you'll have consistently healthier air inside your home.
Changing the air in each room ~3.5 times per hour gives the system more opportunities to dehumidify and filter the air (although I do think humid climates will need a separate dehumidifier).
Because it uses a lower velocity of air flow, it's both quiet and comfortable. You won't hear the air moving through the grilles and you won't feel like you're getting blasted with hot or cold air when you're standing by a vent.
Since you're circulating the air so much more than a standard system, the air coming from the vents won't need to have as large of a temperature differential than the other air around you (again, more comfortable)
The Swidget sensors make the system acutely responsive to each space within the home. Any room can be individually controlled and automatically responded to, instead of relying on a centralized thermostat that might treat an entire floor the same.
The CONs
The main drawback to the design seems easily fixable: a lack of filtration. The MERV 13 filter on the ERV is good, but only having a MERV 6 filter on the main return isn't enough. Using off-the-shelf MERV 13 filters or higher would be a big upgrade.
Not all home layouts will work for the space needed for Oasys and it isn't a good option for a retrofit.
I worry about how well the air will mix with the lower velocity of air flow. You'll have a smaller "throw" on the air (great post this week by Allison Bailes on this), but maybe you make up for that by the consistency of air flow?
This system does require more duct work than traditional ones and will likely need open web trusses to be able to route them where they're needed. That and the design fee from Panasonic can result in a higher initial cost.
I think Panasonic is going to limit how widely they can implement Oasys if they force the design to go through them. Right now the architecture has to get tweaked and approved by their partner architecture firm and Panasonic has to do the energy modeling and calculations. If they could put out guidelines for architects, existing home certification programs, and home consulting companies to handle these aspects, I think they'd get much faster adoption (and more good feedback).
Overall
If you're looking for an incredibly energy efficient HVAC system that can be responsive to changing conditions in each room of your new home, I think the Oasys system is worth looking in to. It won't be the right solution for every house, but it could be a great solution for many. Panasonic is having us back to the house in Houston next month to see the completed project, and I'm looking forward to seeing how it's performing.
I want to give a special thanks to Toner Kersting (Toner Home Performance) for introducing me to the system, Curtis Lawson (Crafted Custom Homes and Your Project Shepherd Podcast) for building a great house and walking us through it, and Ken Nelson (Panasonic) for speaking to our BS* & Beer Atlanta group about Oasys.
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