Zondits recently connected with Maria Murphy, Senior Program Manager at the Northwest Energy Efficiency Alliance (NEEA), who is working to bring high-performance HVAC solutions to the market.
NEEA is a collaboration of over 140 utilities and efficiency organizations working together to advance energy efficiency in the Northwest on behalf of more than 13 million consumers. BetterBricks is a commercial resource of NEEA, offering resources and tools for building professionals who seek to incorporate high-performing technologies and practices into their buildings.
Alex Cimino-Hurt, PSE, and Bryan Kilgore, ERS, August 27, 218
How are very high efficiency (VHE) dedicated outside air systems (DOAS) different from other DOAS with heat recovery ventilation such as those now required by Washington State Energy Code?
To explain, I like to start by talking about DOAS, since it means different things to different people. Conceptually, it’s separating the heating and cooling from the ventilation system. This allows for each of these critical building functions to be optimized to their specific needs rather than compromising to accommodate the other system. The separation also enables lower airflow through the heating/cooling system, allowing for downsizing of that equipment and for better air delivered to the space. However, without a high efficiency heat recovery ventilator (HRV) or energy recovery ventilator (ERV) there is a need to condition the incoming ventilation air.
VHE DOAS improves upon the DOAS concept by focusing on efficiency. The system is designed and built around pairing a high efficiency heating and cooling system with a very high efficiency HRV or ERV. The “secret sauce” that enables the overall system performance and high energy savings are 1) the minimum 85% sensible heat recovery efficiency of the HRV/ERV and 2) the two pieces of equipment being installed together as a system. Some other key attributes include a requirement around economizing with the HRV/ERV, a minimum fan efficacy, and a maximum cross-flow leakage that can only be achieved through plate-type HRVs/ERVs. The VHE DOAS configuration is illustrated below. For more information or to see the system specification, visit BetterBricks.
Note: The VRF/Heat Pump pictured above meets the efficiency and performance requirements in the system specification, but other heating and cooling systems may also be eligible.
In relation to Washington state code, there are a few key differences: 1) the minimum code efficiency is 50% for energy recovery ventilation (wheel or plate-type) while there is no stated requirement for sensible heat recovery efficiency; 2) economizing with the HRV/ERV is not required but, where used, a bypass is required; and 3) the Washington code requirement for DOAS relates to office, education, retail, libraries, and fire stations (WAC 51-11C-40360, sections C403.5 and C403.6), whereas we’re presently focusing only on the first three of these building types.
What are the driving factors responsible for the energy savings that this technology offers?
There are several factors that contribute to the 40%–60% whole building savings that we’re seeing so far in several of the eight pilot project sites BetterBricks has been monitoring and analyzing in partnership with the Northwest utilities for the last few years:
- The heating and cooling system (including the fans), can be downsized substantially due to lower heating and cooling loads and having less air overall to condition because the HRV/ERV is handling the ventilation portion. In some of the pilot project sites, we’ve seen downsizing of the heating/cooling system of up to 50%.
- The 85% HRV/ERV efficiency virtually eliminates the need for supplemental heating and cooling of the ventilation air. The incoming air is being pre-heated or pre-cooled to within 3–5 degrees of the conditioned space temperature by the outgoing exhaust air; hence, there is little to no need for terminal reheat. This also allows for less run time of the heating/cooling system.
One thing worth noting is the importance of integrated design and operation. The substantial energy savings that we’re seeing are due to the interaction between the heating/cooling side and the ventilation side, as well as the air and temperature distribution within the zones. So, for instance, if a standard efficiency HRV (50%–70%) was coupled with a high efficiency heating/cooling system, there would be a need for supplemental heating and cooling, which would limit the downsizing opportunity, increase run time to handle the load from the ventilation air, and result in lower savings (in both energy and dollars) from the system.
What PNW climate features make this technology particularly attractive, and will this technology perform efficiently in a wide range of climate zones?
The PNW climate is not uniform, although it is mostly limited to three primary zones. The area west of the Cascades generally has milder temperatures with relatively low humidity, so there is very little need for frost protection. Areas east of the Cascades, however, are colder and even drier, which means there is little need for latent heat removal, so an HRV is sufficient to address sensible heat. As mentioned above, BetterBricks has partnered with the Northwest utilities and monitored and analyzed several pilot project sites in the coldest to mildest zones, and the system is working well in all of them. In the coldest climates, a little more defrost protection energy use is needed for the HRV. (The system manages this by itself, adding just enough electric resistance energy to the incoming outside air to prevent the core from frosting.) But the actual amount of defrost energy used is trivial on an annual basis. The typical VRF heat pump system also does some defrosting, but these systems are specified for cold climates and adjust their capacity in a way that won’t lose more than around 10% of their capacity at 5°F. However, VRF heating/cooling systems are not the only type of system that can be used. Hydronic systems such as ceiling radiant heating/cooling, floor radiant heating/cooling, or other water/glycol-based systems can be used. The key to the concept, however, is the efficiency and functionality of the very high efficiency HRV/ERV technology handling the ventilation.
Are there applications/sectors where this technology has more success than others?
This system design is still very new to the US, and the enabling advanced HRV/ERV technology that makes it possible only became available here in 2016; hence, there are limited installations thus far. There are few limitations on building type, but it makes less sense for restaurants, warehouses, hospitals, and hotels. It’s not that this type of conversion can’t be done, or shouldn’t be done in these occupancies, but rather they are more difficult to do properly and well; so at the early stages of familiarizing the market with how to do this in the easiest of occupancies (office, retail, schools), we wouldn’t recommend starting with the most difficult occupancies. This type of system is also a great fit in new construction applications for small- and medium-size buildings.
There are some ongoing pilot project sites in office buildings in Western Oregon and Washington that are demonstrating strong energy savings results (over 60% whole building energy reduction, averaging around 40%). We have just begun our first pilot with a middle school facility in the Portland, OR, area. Improved indoor air quality (IAQ) is one of the key benefits of this 100% outside air system and, as a result, schools are a great application. We’ve also worked with two smaller take-out/limited seating restaurants, and those have seen lower energy savings due to the increased ventilation loads from their exhaust hoods/make-up air systems and refrigeration loads. Managing relative pressures in the kitchen and dining zones in a restaurant is also important, which adds a degree of complexity that needs special attention.
There are also several VHE DOAS installations in other parts of the US, in multi-family, assembly, office, and retail buildings.
Cost is often a key barrier to new technology adoption; however, VHE DOAS is a mature technology in Europe. What cost barriers prevent further adoption in the US?
Energy costs are generally much higher in Europe than in the Western US, particularly the Northwest. As a result, the return on investment of these systems is lower here. Over time – and with more design and installation experience and additional product lines becoming available – we anticipate somewhat lower installed costs than we have seen in the pilot projects.
High cost is a key barrier that we’ve encountered in the pilot work. In many cases, the first bid submitted for these projects was high – much higher than the $14-$18/sq ft that the pilots ended up costing. We believe that this is due to 1) emerging technology pricing; 2) supply chain lack of experience in designing and installing this system; and 3) higher cost for a premium product.
How difficult is it for HVAC contractors to learn to implement VHE DOAS in the typical packaged RTU setting? Are you planning any industry trainings to address this potential issue?
As mentioned previously, there are barriers related to sales and installation of these systems. Although this system itself is radically simplified in comparison to many current HVAC solutions in small and medium commercial buildings (e.g., simple but appropriate distribution of ventilation leading to reduced duct system size, simple thermal transfer into the spaces using VRFs or heat pumps, fewer indoor units [AHUs or cassettes], enables simple controls, etc.), it does not conform to the current design rules of thumb and installation practices within the industry. For example, more precise sizing is important – at least 600 sq ft/ton versus the more conventional 400 sq ft/ton. This system requires more than just a “remove and replace” mindset, where a new model of the same RTU (or RTUs) is attached to existing ducts. Design of this integrated system can benefit from energy modeling, or specially designed calculation tools. Conventional guidelines don’t apply. As a result, we are developing guidelines for design and installation. These include HRV sizing, heating/cooling system sizing, ensuring complete separation of conditioned air from ventilation air, duct layout (with positions of supply and return), duct sealing and insulation, and commissioning.
Training is a key element of NEEA’s plan as we design and develop a program encouraging adoption of this system. Due to the fundamental changes in approach to design and installation, we’ll be focusing our efforts first on those early innovators in the supply chain willing to embrace this shift in paradigm. Trainings will be available to supply chain actors to increase their comfort level with the technology and gather market intelligence to address training for the broader market.
What are some of the non-energy benefits that might come from this technology?
There are numerous non-energy benefits that add a lot of value to the building occupants. Key among them are the following:
- Improved indoor air quality (IAQ) – VHE DOAS allows for 100%, fresh outside air with no recirculation
- Increased occupant comfort from near-room temperature delivery of ventilation
- Lower tenant turnover due to improved health and comfort and lower energy costs
- Reduced maintenance requirements and costs
- Improved building management through simplified zone controls, self-commissioning, and performance monitoring
- Ability to provide vital historical performance data to government regulators, building purchasers, or prospective tenants
- More available roof space for other amenities (e.g., PV arrays, green roofs, skylights, etc.)
What are the next steps for BetterBricks development of this technology, and what role do you think utilities and HVAC vendors have in it?
Following the success of the pilot project sites thus far, we will focus initially on targeted awareness-building, training and support to the supply chain by:
- Monitoring/analyzing a few additional pilot sites in specific building types;
- Performing market research through work with key supply chain actors (contractors, distributors, specifiers, and manufacturers);
- Exploring adaptation of software tools to better address design and increase sales of the system;
- Encouraging additional high efficiency HRV/ERV product lines in the North American market.
Our partner utilities and energy efficiency organizations play a key role in this effort by 1) raising awareness through their existing relationships with HVAC market actors who participate in their incentive programs and attend their trainings, and 2) providing incentives (if possible) to help motivate business owners by offsetting the cost of the project installation.
HVAC vendors play the most crucial role in the development and market adoption of this system as they are the firms who would promote, specify, and install these systems. HVAC is a big-ticket equipment category, and building a cadre of early-adopter HVAC market actors is key to the success of this technology. These individuals and firms would ultimately raise awareness and help foster a growing HVAC community that understands the benefits and costs of including this system in their proposed projects.
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