Flowing Forward: Basics in Graywater Recycling and Water Conservation

With climate patterns changing and becoming more unpredictable, water conservation measures are becoming critical to reduce water consumption in our buildings. One way to reduce water consumption and decrease your water utility bill is to utilize a graywater recycling system. Below, we will explore graywater and graywater recycling systems, where they are best to be implemented, and what the requirements are around these systems.

What is Graywater?

Let’s start with the basics. What is graywater? Graywater is nonpotable wastewater from washing machines, showers, bathtubs, lavatories, and HVAC Condensate. It can be treated and recycled for use in water closets/urinals and irrigation systems to reduce your building’s domestic water consumption and wastewater quantity. Graywater is piped separately from the building’s main wastewater system and is routed from the designated fixtures providing graywater to a graywater treatment (if required) and storage system. The exact components of this system will depend on your manufacturer and authority having jurisdiction (AHJ) but it typically consists of a water treatment system, a storage tank, and a pump. The treated graywater will then be routed to the water closets and irrigation systems designed to be served from the graywater systems. Even though the graywater may go through a treatment system, it is important to note that this water is still not potable.

Is a Graywater System Right for Your Building?

Now that we know what a graywater system is, when is a graywater system right for your project/building? To utilize a graywater system to the fullest extent, the project should have a steady and consistent usage of the fixtures supplying the graywater system. Buildings with consistent shower and/or laundry usage provide the best supply to a graywater system. This could apply to hotels, multi-family, fitness/recreation centers, police departments, etc. Buildings without shower or laundry usage can still be a good candidate, but the graywater system may not be capable of providing the water for all the water closets or irrigation needs since the waste from lavatories will typically not equate to the water closet and irrigation usage. A review of the feasibility of a graywater system for a building can be done during the pre-design or schematic design phases with the plumbing engineer and a graywater system manufacturer to determine if it’s a good application for the project.


In conjunction with evaluating if a graywater system is suitable for your building based on building type and fixture usage, it will need to be determined that the AHJ allows graywater systems and if they have any special requirements for the system. The City of Denver, for example, allows and encourages graywater systems, but a graywater system installed in the City and County of Denver must meet the requirements of Denver’s Graywater Use Program, which can be found on the city’s website and outlines requirements for graywater systems used for irrigation and toilets/urinals. These requirements include treatment, signage, watercolor, testing, and permitting needs.


We have now determined that a graywater system is a good application for our project, and the AHJ allows graywater systems. That great! So, what is next? During the early design phase, the engineer will need to work with the architect and other consultants to ensure the proper location and space are allocated for the system. The graywater system will preferably be located in a room below the fixtures providing graywater so the waste can gravity drain into the treatment/storage system. Ideally, this would be located in a basement. The engineer will also need to determine the required system components based on the application and AHJ to ensure proper space is allocated for the equipment. The system could include treatment equipment, storage tanks, pumps, backflow preventors, valves, etc., so ensuring space is appropriately allocated for this equipment early is critical. If the proper location and space are allocated for the graywater system early, this should set up the design for the remainder of the project.

Overall, a graywater system can be a great way to conserve water usage in your building and decrease water utility costs. Prior to implementing a graywater system in a building’s design, the building’s fixture use should be evaluated for the impact of the graywater system, along with confirming the AHJ requirements for graywater systems to ensure it’s the right approach for the project.


The Do’s and Don’ts of Architectural Design: By a Mechanical Engineer

At 360, we love to be team players and share our ideas and insights with our fellow consultants. And boy, do we have ideas! This month, we wanted to help out our architect friends with some brilliant tips and tricks for working with mechanical engineers and making buildings awesome.

Chase Sizes

Everyone loved throwing things down the laundry chute as a kid, so why not bring that excitement to the workplace by adding chases sprinkled throughout the floorplan? Never concede to smaller chases, as they should occupy no less than 25% of the floor. Oh, and make sure you can fit some ductwork and pipes in there if possible. (Picture shown for reference of a building chase)

Do: Provide chases with a minimum of 100 square feet, a large access panel (preferably 3’ wide and 7’ tall with a handle or knob for entry), and a large glass panel to allow observations from outside.

Don’t: Provide only one chase in the building. It may feel entitled and eventually resent the occupants.

Picture shown for reference of a building chase.

Quadruple Paned Windows

Everyone wants to fight for the window seat in the office, but no one wants the perks of afternoon glares, cold spots, and the potential of pedestrians looking in. There are many architectural advances to mitigate those risks, but none more effective than quadruple-paned windows. The more layers you add, the less heat transfers through the window, and the harder someone will have to squint to see inside. While quadruple-paned windows may be a good option, why stop there? Double stacking quadruple pane windows is an even more effective way to not only introduce unique light reflections in the space but also add architectural personality to buildings with windows that are thicker than the walls.

Do: Install double-stacked (heck, even triple-stacked) quadruple-pane windows.

Don’t: Default to the cost-effective, low solar gain, and easy-to-install windows.

Insulation Thickness

Insulation is best described as the warm blanket in the walls that the framing snuggles to keep warm at night. Traditionally, insulation is installed using rigid boards, spray foam, or stuffed batt insulation. However, to give a modern approach to building insulation, we recommend installing rigid dish sponges, silly string spray, or stuffed goose feather pillows as a much better insulation material. If you don’t have any of those materials handy, just stuff the walls with whatever you can find. It’ll be fine!

Do: Provide a wall stuffed full of Kleenex to reduce the HVAC size needed and use the previous batt insulation as blankets on the couch—just be prepared to be extremely itchy as you binge the newest season of Real Housewives.

Don’t: Provide boring rigid or batt insulation in the walls.

Disclaimer: This blog post was released on April 1st, and while 360 Engineering is not a licensed architecture firm, we do have some really great ideas for the advancement of architecture! Call us about your next project; we’ve got quadruple-paned windows ready for you!

COPs Higher than 3’s: The Efficiency of Heat Pumps!

If you’ve been thinking about your mechanical system lately, you’ve probably come across the magical buzzwords “Heat Pumps.” But why does everyone love them so much, and are they really that much better than gas-fired heating equipment?

At its very core, heat pumps just move heat from one space to another, hence the name! At the technical level, they use refrigerant circuits, similar to what’s found in your air conditioner or refrigerator, to extract heat from one space and move it into another. In the ancient, inefficient past, you needed one piece of equipment to heat the space (furnaces, electric heaters, boilers, etc.) and another to cool the space (air conditioners, chillers, etc.) The beauty of a heat pump is that it comes with a small reversing valve within the outdoor unit that can flip the rotation of refrigerant and provide heating instead of cooling to a targeted space. That’s why they’re effective at heating AND cooling the space as a single system.

If all of that has your head spinning, focus on the key terms:

Heat Source: Where is the heat coming from? It could be inside the building, and you want to remove it, or outside it, and you want to bring heat inside.

Heat Sink: Where are you dumping the heat? You can reject heat outside the building to cool the inside spaces down or reject heat inside the building if you want to heat it up.

Coefficient of Performance (COP): This is a ratio of the amount of energy (heat) that comes out of the mechanical system compared to the amount of energy (electricity or fuel) put into the system. Higher is better!

Heat pumps grab heat from the heat source and move it to the heat sink. That’s it! Nothing more complicated about it.

Gas-fired appliances must burn fuel (heat source) to generate heat into the air/water (heat sink), and high-efficiency units have a COP of only ~0.97. Even electric resistance heaters must produce electrical heat to heat the air/water but have an almost equal input-to-output COP of ~1.0. “You get out what you put in.” However, heat pumps don’t rely on heat generation; most of the heat is just transferring already generated heat from one source to another space. And that requires significantly less energy input than generating that heat-so much less energy that the ratio of heat output from a heat pump when compared to the energy it takes to run a heat pump can be upwards of 300% or a COP OF HIGHER THAN 3!

Whether it’s freezing outside or you’re sweating inside your building, heat pumps are an efficient way to relocate that heat to an appropriate heat sink. Gone are the days of accepting a 97% efficient furnace. Now, heat pumps are pushing the limits of energy efficiency, and who can say no to something 3-5 times more efficient than your current boiler?

Here are a few of our current and recent projects where we’ve used heat pumps in the mechanical system design:

  • Arapahoe Library District Administration Building
  • NREL Flatirons Campus Control Center Facility
  • NPS Fort Vancouver National Historic Site Building 725
  • NPS Rocky Mountain National Park Fall River Entrance Station
  • NPS Zion National Park South Campground
  • NPS Tumacacori National Historical Park Satellite Administrative Office Building
  • Denver Zoo Sea Lions Exhibit
  • DPS Fallis Elementary School – READ MORE ABOUT THIS PROJECT

Lovers of Louvers: Mechanical Engineering Romance this Valentine’s Day!

It’s hard to imagine an inanimate object capable of being loved, but let me share my viewpoint.

They matter!  Louvers are used in both intake and exhaust applications for HVAC systems.  Without louvers, we would have large openings on the side of the building with screens, allowing all the snow and rain to enter.  So, how does a louver keep all the driving rain and snow out of the building?  Louvers have varying blade shapes that provide different performances.  All louvers are tested via a standard test to determine the point at which water will pass through.  The air velocity in which water passes through a louver varies anywhere from 300 feet per minute (fpm) to over 1,000 fpm.  When an engineer sizes a louver, they size one such that the velocity of airflow will remain below the tested penetration threshold.  The louver plays an important role in keeping water out of the building.

Louver sizing is also impacted by the amount of free area they provide.  Louvers are rated with pressure drops, which need to be calculated in the sizing of fans within the mechanical system.  A louver that has a high-pressure drop increases the need for a larger fan and more energy usage.  A louver with a low-pressure drop allows for less fan energy.  Who doesn’t love something that takes less energy?

Louvers come in all shapes, sizes, and colors.  They want to be sized to reduce the water penetration and pressure drop, but you can integrate them into the context of the building.  There are rectangular ones, square ones, round ones, triangular ones, and, in the spirit of love, diamond-shaped ones.

When I was a young engineer, spell check was a new tool.  And on one project, all of the keynotes referencing louvers were autocorrected to “lovers.”  The contractor had some fun with this, and I am now on the lookout for “lovers” on projects. 

Denise M. Dihle, PE, 360 Engineering Founder, President, Principal

Cold Climates and Heat Pumps: How It Started, How It’s Going

Electrification and Sustainability Goals: Unveiling the Role of Heat Pumps

As we’ve all continually heard in recent years, electrification is a major sustainability goal for many municipalities, states, and even countries around the world1. Along with electrification comes a plethora of buzzwords and phrases, one of the most familiar being heat pumps. Air-source heat pumps—the most common application due to the relatively low cost of such systems—can absorb heat from the ambient air and transfer that heat into an occupied building space. But how does that work when the outside ambient air is cold?

Air-Source Heat Pumps Demystified: Operation in Cold Climates

Heat pumps manipulate the chemical properties of refrigerants at different pressures to absorb and release heat energy, moving it from outside to inside to heat a building.

At the right pressure, the boiling point of the refrigerant will actually be lower than the cold outside air temperature—and since heat energy always moves from the higher temperature substance (in this case, the outside air) to the lower temperature substance (the refrigerant), heat is absorbed from the “cold” outside air and then cycled to the occupied space.

The Chilling Challenge: How Cold Can Air-Source Heat Pumps Go?

So, heat pumps can pull heat from relatively cold outside air—but how cold can that outside air be?

The short answer is that it depends on the type of heat pump you are working with. Most one-to-one split heat pump systems (i.e., a single outdoor unit connected to a single indoor unit) and packaged heat pump systems (e.g., packaged rooftop units) begin to significantly reduce their heating capacity around 40-45°F ambient temperature—which is when you really start needing the heat!

However, these systems are typically designed to accommodate this derated capacity as the temperature continues to drop. Regardless, one-to-one and packaged heat pump systems are limited in how much heat they can provide at very cold temperatures. Below the “balance point” of derated heat pump capacity and building heating load, supplemental heat becomes necessary, typically in the form of some electric resistance heaters.

Beyond Limits: Variable Refrigerant Flow (VRF) Systems Revolutionizing Cold Climate Heating

The most advanced heat pump technology available today takes the form of Variable Refrigerant Flow (VRF) systems. VRF systems have been around in East Asia and Europe for decades and have gained a foothold in the U.S. in the last 15-20 years. This technology has seen an explosion of progress in that time. A few decades ago, VRF systems were only rated for heating in the range of -5°F to -10°F, below which the systems were configured to shut down to protect their internal components from the “extreme” cold! However, VRF systems today have heating performance data for operation down to -22°F or less! Granted, at a significantly derated heating capacity, but pause and grasp that this technology can pull heat out of -22°F air and move that heat inside your building! The upshot is that the balance point of VRF systems is much lower than the one-to-one or packaged heat pump systems described above. 360 Engineering has designed systems for large buildings in Denver and other cold climates capable of meeting the full heating load at -5°F without any supplemental heat systems required.

Breaking the Cold Barrier: Technological Advances in VRF Systems

Multiple technological advances have allowed VRF to progress to such a viable heating system, even in cold climates. Physical accessories on the outside casing of the heat pump units, such as wind baffles and snow hoods, mitigate the effects of weather on the operation and efficiency of the VRF heat pumps. Inside the heat pumps, flash-injection technology—where the system introduces a modest quantity of mixed-phase refrigerant (i.e., a mixture of gas and liquid) to cool the compressor—allows the compressor to operate at higher speeds by mitigating friction and accumulation of internal heat2. Higher compressor speed results in greater heating capacity for the system at lower ambient temperatures. On top of these technologies in the outdoor unit, VRF systems take advantage of heat recovery internally as well, moving energy from interior zones that have excess heat available to exterior zones that need that heat energy—bypassing the outdoor unit entirely through the use of an intermediate “mode control unit.”

Future Trends: The Journey of Heat Pump Technology in a World Moving Towards Electrification

Heat pump technologies have come a long way since they were first introduced in the HVAC industry. While limitations still exist for certain systems and applications, air-source heat pumps have become a viable and highly efficient option to provide the heat needed for buildings in cold climates. As the world continues toward electrification and the market demands better, higher-performing heat pumps, this technology will continue to progress toward greater heating capacities at colder ambient temperatures.




Gunnison County Library – The Road to Net Zero

Gunnison County Libraries was looking to replace its existing library in Gunnison, Colorado, with a new sustainable building providing flexible and functional community space. The 15,000-square-foot public facility also needed to stand up to the harsh and variable weather conditions experienced in Gunnison. The high-elevation mountain sun is intense all year round, while winter ambient temperatures in the Gunnison Valley can drop below negative 30 degrees. In addition to cold temps, deep and heavy snow is common, so careful design of the roof systems by the Anderson Hallas Architects team was critical to handling snow and ice. 

Energy Modeling and Assistance in Achieving Sustainability Goals

360 Engineering provided mechanical and plumbing engineering services, including energy modeling and assistance in achieving sustainability goals for the project. The design team was tasked with providing a building with an EUI (Energy Use Intensity) under 30.  As a reference, the median EUI for a library in the US is 71.6 (Energy Star Benchmarking).  The energy-efficient mechanical system combined geothermal ground source heat pumps and a variable air volume dedicated outside air system (VAV DOAS) with new DDC controls. The energy model completed at the end of the design predicted an EUI of 27.

Building EUI (Energy Use Intensity) goals for Net Zero

What does a low EUI have to do with Net Zero?  A chart was developed by Building Green (BuildingGreen.com) to provide EUI goals for buildings that, combined with a solar PV array, provide a pathway to a Net Zero building.  The Gunnison Library, a single-story, 15,000-square-foot building, has a targeted EUI of over 50.  However, the chart developed by Building Green is based on a building using 70% electric and 30% natural gas.  Having a goal of reducing fossil fuels and a fully electrified building shifts this chart, and the design goal of under 30 EUI puts us on the right track to achieve Net Zero.

Utilizing Solar

The Gunnison Library utilizes an 18kW solar array with the intent that solar PV could be expanded as the allowable kW per array increases.  The 18kW array provides 1.2 watts per square foot and is a minimal array, considering the average size of residential arrays are 7.1 kW (NREL).  

So, how is the building doing?  Over the last five months, the building has been operating with an EUI of 15.5! As mechanical engineers, this isn’t just a triumph; it’s a testament to our role in shaping a future where Net Zero isn’t a lofty ideal but a measurable reality. It’s a call to action for mechanical engineers everywhere—to engineer not just systems but sustainable solutions that propel us toward a future where our buildings don’t just weather the storm but become beacons of environmental responsibility.

The Power of Electrification in Preservation: NPS Fort Vancouver Museum Facility


The National Park Service (NPS) stores, maintains, and displays historic collections, artifacts, and culturally significant pieces across various sites. Recognizing the need for efficient infrastructure, NPS seized the opportunity to relocate collections and archives from several sites in the Northwest Region into one larger facility at Fort Vancouver National Historic Site in Washington.

Key Objectives:
  • Reduce deferred maintenance
  • Decrease operation and maintenance (O&M) costs
  • Address museum standard deficiencies
Site Selection:

NPS chose Fort Vancouver Building 405 as the repository for collections from four national parks, totaling over 3 million items.

Inside Building 405 – Before Construction (Photo Credit: Anderson Hallas Architects)

Fort Vancouver Building 405 Rehabilitation Project

Facility Overview:
  • An existing 14,000-square-foot 1980s aircraft maintenance hangar
  • Selected for rehabilitation to serve as a museum collection storage facility
  • Dedicated spaces for object and archival storage, curated labs, and public viewing areas
Public Engagement Spaces:
  • Climate-controlled zones for high storage capacity
  • Visible spaces for public viewing in a preservation-friendly manner
  • Spaces for curatorial labs visible to the public
  • Large gathering spaces for school field trips and general assembly use

Mechanical System Options by 360 Engineering

Discovery and Presentation on Anderson Hallas Architect’s Team:
  • Based on our evaluation of the existing building and project goals, including 100% electrification, 360 Engineering explored various options
  • Presented options in a “Choosing By Advantage” or Value Analysis format, providing three options
  • Brennen Guy and Spencer Rioux presented to NPS staff at Fort Vancouver, addressing the pros and cons of each option
360 Engineering Project Manager, Brennen Guy, PE (CO), Presenting to NPS
Variable Refrigerant Flow (VRF) System Selected:
  • Reasons for Selection:
    • Minimizes ductwork to maximize storage space
    • Accommodates varying occupancies, including critical storage, laboratories, assembly spaces, library, and offices
    • Aligns with NPS’ energy-efficient principles, promoting reduced consumption and fossil fuel reliance
Advantages of VRF System:
  • Efficiently manages heating and cooling loads for diverse occupancies
  • Facilitates refrigerant heat recovery between zones, reducing energy waste
  • Aligns with NPS’ commitment to energy-efficient systems
Fort Vancouver Building 405 Rendering (Photo Credit: Anderson Hallas Architects)


Adopting the Variable Refrigerant Flow (VRF) system for Fort Vancouver marks a significant step in realizing NPS’ Service-Wide Curation Facility Plan. This decision ensures optimal preservation conditions for the extensive collection while promoting energy efficiency in line with NPS’ principles.

Ready to upgrade your building or project with electrification? Let’s discuss your Mechanical Engineering needs today. Contact us to book a 30-minute consultation.

Elevating Aesthetics While Minimizing Cost Impacts

HVAC and plumbing systems are essential to creating a comfortable and productive environment in our buildings; however, nothing can bring down the look of a well-designed space more than a misplaced diffuser or unexpected thermostat. In most instances, concealing HVAC and plumbing designs into high-finish spaces can come with major cost impacts, but there are simple ways to elevate the integration of these systems into a space without major impacts on the budget. Let’s explore a few!

Alignment of Ceiling Devices

Aligning diffusers with other ceiling devices is a small task but can have a big impact on the uniformity of the ceiling to provide a clean and organized look. The goal of this approach would be to align diffusers and other ceiling devices to the centerline of the lights, along with creating uniform spacing between the diffuser and other ceiling devices. To ensure the engineer has time to coordinate the final diffuser and device locations, the final locations of lights and other ceiling components should be provided around 75-80% CDs for final alignment. If the aesthetics of a space is a priority, having an RCP coordination meeting between the architect, electrical engineer, and mechanical engineer can be very beneficial to talk through the priority of devices and ensure all parties are fully coordinated.

Elevate the Diffuser Specifications

Standard cone, louvered, or perforated diffusers can be swapped out to a square plaque diffuser for both the supply and return in the ceiling for a small cost increase ($20-$30/diffuser*). If both the supply and return diffusers are revised to this specification, this can create a clean, uniform look in the ceiling. Square plaque diffusers have a very efficient supply air distribution, providing low-pressure drop and low sound levels with efficient mixing. However, it should be considered when using this specification for return air that this diffuser has less return capacity than other return diffusers with more free area, so additional return grilles may need to be added with this specification.

In addition to revising the specifications for square ceiling diffusers, there are many aesthetically pleasing grilles and slots that can be incorporated into the design for supply and return air. The architect should coordinate with the mechanical engineer early in the design process to discuss linear grilles or slot diffuser options to ensure these are properly coordinated into the ceiling and wall details. Although linear grilles and slot diffusers can add significant cost compared to standard louvered grilles or diffusers, applying slots to strategic spaces like lobbies or conference rooms can elevate these common spaces and set the tone for the rest of the building.

Coordinating Thermostat Locations and Specifications

When placing the thermostats on the plans, the engineer must be strategic with the placement to ensure optimal control of the mechanical system. If this is not properly coordinated during design, this can lead to unexpected locations on the wall come time for the final punch. When we are placing thermostats in the design, we are considering the following: direct sunlight, exterior walls, the path of supply airflow, proximity to major heat-producing equipment, location within the occupied/breathing zone, and many more. In some spaces, these considerations can make thermostat placement challenging.

For proper placement coordination, the architect should review the proposed thermostat locations on the drawings once the engineer has laid them out to ensure the locations do not conflict with their design.  For more complex spaces, deeper coordination may be required to shift around the thermostats or even shift wall finishes around to accommodate the ideal thermostat location. A coordination meeting between the architect and mechanical engineer may be ideal for these more complex applications.

If local control of the temperature setpoint in the space is not required, remote temperature sensors can be considered for minimal added cost. This would locate a thermostat in a concealed or central location for temperature adjustment (If DDC controls are provided, this could be provided via a web-based controller) with a remote temperature sensor placed in the space being measured. There are several types of remote temperature sensors available, including button-style sensors that are about 1” in diameter and can be stainless steel, brass, or paintable and can be easily integrated into the design.

Although these recommendations are simple, they can be effective if proactive coordination is achieved. Having upfront discussions on the design intent of the mechanical and plumbing system integration throughout the project will help the engineer provide solutions early to achieve the aesthetic goals of the space. Additionally, if the aesthetics of these systems are a priority in a space, but the budget is tight, these simple solutions and several others can be applied without busting the budget.

Coming Soon, to a Heat Pump Near You: Refrigerant Changes

Last month, we summarized some of the why and how of electrification related to mechanical and plumbing systems. When it comes to all-electric HVAC, the common denominator is refrigerant. Just about any mechanical system providing heating and/or cooling without using fossil fuels will include refrigerant at some level—heat pumps, chillers, geothermal they all include refrigerant compressor circuits. So, on top of local, state, and federal regulations pushing the industry toward building systems electrification, Congress has kept things interesting by passing the AIM Act in 2020.

The AIM Act and Refrigerant Regulation

The American Innovation and Manufacturing (AIM) Act grants the Environmental Protection Agency (EPA) the authority to regulate and phase out hydrofluorocarbon (HFC) refrigerants in the coming years. HFCs are potent greenhouse gases with a global warming potential (GWP) thousands of times higher than carbon dioxide (GWP = 1). To combat this, the EPA has set GWP limits for refrigerants manufactured or imported in the U.S.

Impact on the HVAC Industry

Current Refrigerant Landscape: Most heat pumps (including water-source heat pumps, variable refrigerant flow systems, etc.) and DX cooling units currently use R-410a refrigerant, boasting a GWP rating of around 3,000.

EPA’s GWP Limits: Starting in 2025-2026, the EPA mandates a GWP limit of 700 for refrigerants in these systems. Other types of equipment (such as supermarket refrigerated displays) have even lower GWP limits.

Industry Response: HVAC equipment manufacturers are investing significant time and effort in redesigning equipment to accommodate alternative refrigerants that comply with EPA requirements.

Choosing the Right Refrigerant

  • Various refrigerant options are available, but only a few are practical replacements for HFCs in HVAC systems.
  • Selection involves economic considerations and evaluation of potential life-safety risks.
  • Codes and standards such as the International Mechanical Code and ASHRAE Standard 15 guide allowable refrigerant volumes based on health hazards, flammability, and reactivity.
  • Our job as engineers is to calculate and confirm that a leak in the piping or equipment we’ve specified would not result in a concentration above this limit inside the smallest enclosed space served by our system.

Understanding Allowable Concentrations

  • For instance, R-410a has an allowable concentration of 26 lbs. per 1,000 cubic feet, with a health hazard rating of 2 (coupled with flammability and reactivity hazard ratings of 0).
  • R-32, a potential R-410a replacement, has a lower health hazard rating of 1 but a higher flammability hazard rating of 4, resulting in an allowable concentration of only 4.8 lbs. per 1,000 cubic feet.

Implications for HVAC Systems

  • The AIM Act’s impact extends to architectural, electrical, and structural designs.
  • Uncertainty remains about manufacturers’ refrigerant choices and their effects on system designs.
  • Potential changes could lead to larger equipment and piping, challenging installation, maintenance, and clearances.
  • Increased electrical loads may strain infrastructure, especially in buildings aiming for full electrification.

In summary, while the HVAC industry faces uncertainty due to the AIM Act, it is actively preparing for the changes. As engineers, we anticipate and embrace these challenges and are excited about the innovations driving our industry toward a more efficient and sustainable future.

For further details, visit the International Code Council website.

Exploring Complete Electrification in Denver

At 360, we are constantly looking for ways to comply with the ever-changing permitting requirements and climate change mitigation efforts that the city of Denver implements. Our world is constantly evolving, and we need to find solutions to new climate challenges each day. In this blog post, we will discuss the opportunities for Complete Electrification in Denver

Our team is critically looking at options to ensure each project we work on not only meets the required regulations but is cost-effective too. Read along to see the importance of electrification and its impact.

What We Look At

In 2019, buildings and homes accounted for 64% of all community-generated greenhouse gas emissions in the city of Denver1. In 2020 Denver had the worst air pollution in 10 years2. Natural ventilation isn’t as effective when the air quality continues to decline, and moving to an all-electric system could mitigate safety issues associated with poor air quality while also reducing greenhouse gas emissions.

What is the Road Map to Electrification?

  • Effective Now
    • Obtaining “Quick Permits” is no longer allowed for replacing air handling units or water heaters utilizing natural gas in commercial buildings. The permitting process for these projects will be the same as applying for a new heat pump.  There are a few exceptions.
  • Starting January 1st, 2025
    • Replacement of outdoor gas-fired equipment used primarily for heating needs to be electric, and secondary gas-fired heating equipment can be installed for supplemental heat only.
    • Replacement of outdoor cooling air conditioning or condensing unit equipment needs to be electric and provide space heating (like a heat pump), and a secondary piece of equipment can be installed for supplemental heat only. 
    • Replacement of a storage water heater or instantaneous water heater needs to be an electric water heater.
  • Starting January 1st, 2027
    • Replacement of gas-fired boilers must utilize electric heating for 50% of space heating needs/water heating needs; the remaining 50% can be met with a replacement of the gas-fired boiler.
    • Replacement of an air conditioner that serves spaces that are also being heated needs to be replaced with electric equipment that does both heating and cooling.

How does this affect the A&E Industry?

  • Denver will require reporting of estimated building Energy Use Intensity (EUIs) with targeted goals in 2024, 2027, and 2030.
  • There will be fines associated with incorrect modeling/inability to meet target EUIs (as established by Denver).
  • High-Efficiency Mechanical equipment will be the standard.
  • Increased coordination between disciplines will be even more important.
  • All disciplines (not just mechanical) have options to assist in Denver’s EUI requirements:
    • LED lighting
    • Green-sourced energy
    • High efficiency, tight envelope construction
    • Energy Star and low-water plumbing fixtures

Limitations of Electrification

  • Upfront costs for heat pumps are typically higher than standard Direct Expansion (DX) cooling and gas-fired air handling units.
  • Currently, gas rates in Denver are still lower per amount of heat energy than electricity.
  • Newer technology for building operators: lack of experience may result in lack of confidence in new heat pump technology.  Additional training may be needed for facility staff.
  • Most existing buildings were not provided with an electrical service intended for full building heating.  An Electrification Feasibility Report is one way to determine the impact of a fully electric mechanical system on the building infrastructure. 

Let’s Wrap it Up

With the new regulations coming, Life Cycle Cost Analysis (LCCA) will become even more important to show the offset of maintenance, utility, and upfront costs between mechanical systems. It is important to know the regulations to ensure the safety and longevity of your product. Energy modeling is already required in some cities like Boulder and will become required in Denver to demonstrate energy compliance.

For any questions or inquiries or to get started on your next project, Contact Us.


1 https://denvergov.org/files/assets/public/climate-action/documents/denver-nze-implementation-plan_final_v1.pdf

2 https://www.colorado.gov/airquality/tech_doc_repository.aspx?action=open&file=2020AnnualDataReport.pdf


Direct Expansion (DX): the most common type of air conditioning in the US where the indoor air is cooled with a refrigerant liquid.

Electrification: the conversion of a machine or system to the use of electrical power.

Energy Use Intensity (EUI): refers to the amount of energy used per square foot annually.

Life Cycle Cost Analysis (LCCA): it is an economic evaluation technique that determines the total cost of owning and operating a facility over a period of time.