How Ductless Heat Pump Technology Works

Today, we are going to outline manifolded, ductless heat pumps. We first learned about these systems a few years ago, while working on a LEED hotel in Colorado. We want to give readers some background and thoughts on this technology.

Used in Europe and Asia for the last 2 decades, ductless heat pumps are still relatively new here in the US. How are these different from our more familiar heat pump systems? Heat pumps that we may be familiar with are known as Split Systems – compressor outside connected to the heat sink, and inside the energy is moved to a coil in the air handler. The air in the air handler blows air over the coil, changing the temperature. The heat exchange goes on in the air handler. The heat sink maybe their ambient air, a ground loop, a cooling tower, or a pond. Refrigerant is pumped through loops to transfer heat to the sink. In the winter heat can be draw in from the ground that is at 55°F year round below frost depth.

Ductless systems are also Split Systems, but are more complex than the normal arrangement. These systems have the outside compressor, heat sink, like the other system. However, inside the building, it gets much different. The refrigerant from the compressor is piped to a Manifold, and then from the Manifold it is exchanged to pipes leading to Terminal Units spread throughout the building.

How does this operate differently from the normal HVAC ducts? First in the duct, the system moves heated or cooled air to the zone(s) based on the thermostat setting for that zone. The familiar “click” we know and then the sound of the fan blowing air to the room. In these ductless systems, controls rely on a more complex system of moving existing heat around the building. Each Terminal Unit has a thermostat that is tied to the computer that runs the Manifold. The Terminal Unit senses it is above or below the set point and then tells the Manifold to send the correct temperature refrigerant. The Manifold checks the available heat or cold difference in other terminal units and adjusts the flows until the set points are met. If it needs to it will activate the heat pump outside to reach the set points. Terminal Units typically have a coil and a fan unit. They use very little power as compared to baseboard electric heat.

Here is an example of how it works; you have a building, the west side and south side rooms are gaining solar heat and will require more cooling. Now factor then also on the opposite sides of the building, those rooms are losing heat through walls and windows. What the Ductless system does is first try to move heat to the cooler parts of the building. It first absorbs the heat from the warm rooms, and moves it to the cool ones. Then based on the set point will activate the outside compressor system to toss out more heat from those other rooms.

Other advantages are on remodels, only the holes for the piping need to penetrate walls. Systems come with a variety of Terminal Units, from wall mounted, to ones that fit in suspended ceiling grids, even ones that look like picture frames. For the architect this opens up many possibilities.

On that LEED hotel project, our initial plans were to replace the typical PTAC (Packaged Through-wall A/C) with terminal units in each guest room. In effect, we would use the entire hotel as the heat sink, solar gain rooms would have heat dumped into shade side rooms, and the occupied rooms would dump heat into the unoccupied rooms. Most of this would go on without any compressors kicking in. That has huge implications for energy savings.  In addition, these units have SEER ratings of 19 to 26, very efficient, compared to PTACs, with a SEER of 13 to 15. Combined with the other systems and considerations we are incorporating into the LEED plans it looked good to get that LEED Gold. Or does it?



Hotels are difficult typologies when it comes to LEED applications. Hotels are like large houses, with everyone getting up at the same time and wanting a hot shower, TV on and the AC blasting. The customers are purchasing the right to have it their way, LEED or nor LEED plaque on the front of the building. As such, the demands are greater at peak usage than for other types of buildings.

What is an energy and money saver in a house, bank, or office has the opposite effect sometimes in a hotel. We found that out the hard way with the electric instant-hot water taps. Likewise, for the ductless system all though it’s efficiency was in every way superior to the best PTACs, the install cost was the killer.

Here is what we found: Installation was several times more expensive, the overall system was more expensive to supply. Second, durability – commercial PTACs last about 5 years in the hotel environment, the ductless system can last at least 20 years. So installed in a house, office building, even condominium it would make sense because these are long-term investments for the owners. Hotels have to be profitable very quickly, typically in 3 to 5 years. Even though our client was intending to keep the project long term, part of the business plan is to be at a profit in 5 years. Part of achieving that was the choice to go back to high efficiency PTACs with advanced controls and vacancy sensors – even though PTAC replacement four times in the next 20 years will cost more than the ductless system installed.

Additionally Hotels have a higher level of fire compartmentalization, and we would need to run fresh air supply ducts in order to balance the typical bathroom exhaust from each room. A PTAC typically brings in enough fresh air to meet those requirements. In other building types, this is not as strict so undercutting doors, and other means of natural ventilation are used.

We did have the system used in the offices and public areas of the hotel, and that improved our overall building efficiency. Because as architects we had an open mind when the engineer suggested the system we explored its possible applications and implications to ventilation and energy design. We were fortunate that we had very good energy modeling services. They helped the client choose the best system that met LEED goals and the business plan.



We looked at Mitsubishi Electric and Sanyo (through Trane). Both systems function in the same way, but carefully consider how they communicate with the rest of the temperature controls in the building. We feel that these kinds of systems will find their way into more housing and office projects. We feel that this will be another useful tool in many applications. Architects should ask their engineers if it is a possible fit, but have sober ideas about the cost in larger applications.

Colorado Zero Energy Home Building

These homes go by a handful of different names including zero-energy home building, zero-net (or net-zero) energy building, or zero-carbon home building, but they all mean exactly the same thing. Which is this: The building is designed to generate enough renewable energy onsite to completely offset its energy consumption needs. There are a couple wrinkles to this concept, which we’ll get to in a minute, but there’s no need to get confused by the carousel of names. They all mean a home or building that generates as much renewable energy as it consumes.



The single biggest wrinkle about what constitutes a zero-energy home build is whether or not the property is connected to an electrical grid and in such a way that allows surplus renewable energy production to be fed back into the electrical grid. Homes that aren’t connected to a modern grid or ones that are built entirely off-the-grid—and we have more than a few of these in the more mountainous regions of the state—these homes don’t have this advantage. Thus, the energy generation and storage must accommodate periods of peak use and higher energy needs. The good news is that between portable and compatible home energy storage batteries and by commonsense rationing of major home energy appliances, this type of off-the-grid zero energy home build is more plausible and affordable than ever.



From Accent to Zola, there are 34 home building and residential construction companies in Colorado that have completed qualified projects, according to the Zero Energy Project. This organization also provides business directory information for designers, realtors, auditors and consultants in the state. This performance usually isn’t the only factor that goes into choosing a builder or major residential contractor, so it’s good to know that there is more than one option for most projects.


Features of an Energy Star New Home

Energy Star qualified homes can include a variety of ‘tried-and-true’ energy-efficient features that contribute to improved home quality and homeowner comfort, and to lower energy demand and reduced air pollution. Energy Star homes include:


Effective Insulation

Properly installed and inspected insulation in floors, walls, and attics ensures even temperatures throughout the house, reduced energy use, and increased comfort.


High-Performance Windows

Energy-efficient windows employ advanced technologies, such as protective coatings and improved frames, to help keep heat in during winter and out during summer. These windows also block damaging ultraviolet sunlight that can discolor carpets and furnishings.


Tight Construction and Ducts

Sealing holes and cracks in the home’s “envelope” and in heating and cooling duct systems helps reduce drafts, moisture, dust, pollen, and noise. A tightly sealed home improves comfort and indoor air quality while reducing utility and maintenance.


Efficient Heating and Cooling Equipment

In addition to using less energy to operate, energy-efficient heating and cooling systems can be quieter, reduce indoor humidity, and improve the overall comfort of the home. When properly installed into a tightly sealed home, this equipment won’t have to work so hard to heat and cool the home.


Efficient Products

Energy Star qualified homes may also be equipped with Energy Star qualified products — lighting fixtures, compact fluorescent bulbs, ventilation fans, and appliances, such as refrigerators, dishwashers, and washing machines.


Third-Party Verification

With the help of independent Home Energy Raters, Energy Star builder partners choose the most appropriate energy-saving features for their homes. Additionally, raters conduct onsite testing and inspections to verify the energy efficiency measures, as well as insulation, air tightness, and duct sealing details.



Homebuilder Energy Star Program and Incentives

For years, the Governor’s Energy Office (GEO) and Energy Star New Homes Program Partners have worked with homebuilders’ associations and homebuilder companies to support the construction and testing of new homes built to Energy Star standards. Any home three stories or less can earn the Energy Star label if it has been verified to meet the guidelines set forth by the EPA. This includes single family, attached, and low-rise multi-family homes; manufactured homes; systems-built homes (SIP, ICF or modular construction); log homes; concrete homes; and existing homes that are retrofitted.

All certified new homes receive the Energy Star label to allow for simple identification by area homebuyers. It’s also part of the marketing and active support that participating homebuilders may receive as part of the program. To earn the Energy Star label, a home must meet guidelines for energy efficiency set by the U.S. Environmental Protection Agency. These homes are at least 15% more energy efficient than homes built to the International Residential Code (IRC) and include additional energy-saving features that typically make them 20–30% more efficient than standard homes.


Information for Homebuilders

  • Review the Energy Star New Homes Program requirements, and visit the Energy Star New Homes website to familiarize and educate yourself about the Energy Star label. Your local GEO Program Partner will be able to give you more information about how your area is participating and how you can take part. Attend trainings and events facilitated by the local Program Partner. These trainings may be focused towards different areas including building science, marketing & sales, realtors, home energy raters, architects, trade contractors, appraisers, lenders, and consumers at no cost to you.
  • Register as an Energy Star Partner at the Energy Star website, and integrate the construction techniques and systems from the trainings provided to build an Energy Star New Home. Now, you can start building Energy Star New Homes. Engage a local HERS Rater to certify & label your new homes. Homebuilders need to proactively engage a local HERS rater during the design/building process to maximize efficiency and to achieve an Energy Star label. Find lists of HERS raters at the Energy Star website and at the Residential Energy Services Network (RESNET) website.
  • Market and sell your new homes. US Environmental Protection Agency provides free marketing & sales materials (logos, brochures, document templates, etc) to all participating Energy Star homebuilders. Contact your local utility company to determine if you qualify for additional rebates.

Benefits of Buying an ENERGY STAR New Home

Buying a home with an Energy Star label can result in the following benefits:


Added Confidence

Home buying is complex enough without having to know all the details of energy-efficient construction. Instead, look for the Energy Star label to easily identify homes that are truly energy efficient. Find the house of your dreams and enjoy peace of mind knowing that it also meets strict energy efficiency guidelines.


Lower Ownership Cost

Compared with standard homes, Energy Star qualified homes use substantially less energy for heating, cooling, and water heating-delivering $200 to $400 in annual savings. Over the average 7 to 8 years you may live in your home, this adds up to thousands of dollars saved on utility bills. Additional savings on maintenance can also be substantial. Financing your home purchase using an energy efficient mortgage can also lead to savings.


Better Performance

Properly installed energy-efficient improvements deliver better protection against cold, heat, drafts, moisture, pollution, and noise. An energy-efficient home helps ensure consistent temperatures between and across rooms, improved indoor air quality, and greater durability.


Smart Investment

To date, more than 5,000 home builders have partnered with the Environmental Protection Agency to construct more than 840,000 Energy Star qualified homes. By the end of the decade, more than 2 million homes are expected to earn the Energy Star label. The trend is clear. By choosing an Energy Star home, you can be confident that it will have an increasingly valued feature when the time comes to sell.


Environmental Protection

Did you know that your home can be a greater source of pollution than your car? In fact, 16 percent of U.S. greenhouse gas emissions are generated from the energy used in houses nationwide. Energy used in our homes often comes from the burning of fossil fuels at power plants, which contributes to smog, acid rain, and global warming. Simply put, the less energy we use in our homes, the less air pollution we generate.


What Homebuyers Should Look For

Energy efficiency is the place to start. That’s because the energy used in homes often comes from the burning of fossil fuels at power plants, which contributes to smog, acid rain, and risks of global climate change. So, the less energy used, the less air pollution generated. And the easy way to make sure a new home is energy efficient is to look for the blue Energy Star mark, the government-backed symbol for energy efficiency.


Typical Features in Colorado Energy Star Homes

  • An Efficient Home Envelope with effective levels of wall, floor, and attic insulation that is properly installed and comprehensive air barriers.
  • Efficient Air Distribution where ducts are installed with minimum air leakage and are effectively insulated.
  • Efficient Equipment for heating, cooling, and water heating.
  • Efficient Lighting including fixtures that earn the Energy Star label.
  • Efficient Appliances including Energy Star qualified dishwashers, refrigerators, and clothes washers.


These energy efficiency improvements save homeowners money—about $200 to $400 per year on utility bills. More importantly, monthly energy savings can easily exceed any additional mortgage cost for the energy efficiency improvements, resulting in a positive cash-flow from the first day of home ownership. As a result, the cost-effectiveness of Energy Star improvements can help offset additional costs associated with other green home features.


What comes after energy efficiency?

Homebuyers can also look for the Energy Star Indoor Air Package label—a new specification developed by EPA to address the indoor environment component of green building. Homes that achieve this level of excellence are first qualified as Energy Star, and then also incorporate more than 60 additional home design and construction features to control moisture, chemical exposure, radon, pests, ventilation, and filtration. Together, these features help protect qualified homes and their residents from mold, chemicals, combustion gases, and other airborne pollutants.


Completing the green home picture

Through Energy Star qualified homes and the Energy Star Indoor Air Plus Package, homebuyers can address two critical green home elements. Then, look to the wide variety of available green home programs to complete the picture with water-efficient products, renewable energy technologies, waste reduction, recycling, and sustainable land development practices.