Passive House Design – What Does it Mean

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Passive House – What Does It Mean

Recently, in conversations with mechanical engineering and architectural specifiers about ventilation in commercial buildings, I have noticed persistent confusion over the use of the phrase “Passive House.” Developed originally by the German Passivhaus Institut (PHI), the phrase describes the concept of building airtight, well-insulated buildings that provide occupant comfort while requiring very little energy to heat or cool.  The concept was first applied decades ago in single family residential structures. However house does not mean only single family residential.  The confusion is especially understandable considering that the Passive House concept is relatively new in the multi-family and commercial building sectors of North America. Passive House building principles can be applied to all building typologies from single-family homes to multifamily apartment buildings, dormitories, offices, and skyscrapers.

Today the Passive House movement is promoted and managed by the Passive House Institute US (PHIUS) which has developed building standards and certifies consultants, projects and products for Passive House design.  Passive building comprises a set of design principles used to attain a quantifiable and rigorous level of energy efficiency within a specific quantifiable comfort level. “Maximize your gains, minimize your losses” summarizes the approach. To that end, a passive building is designed and built in accordance with these five building-science principles:

  • Employs continuous insulation throughout its entire envelope without any thermal bridging
  • The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air
  • Employs high-performance windows (typically triple-paned) and doors
  • Uses some form of balanced heat- and moisture-recovery ventilation and a minimal space conditioning system
  • Solar gain is managed to exploit the sun’s energy for heating purposes in the heating season and to minimize overheating during the cooling season

Buildings designed and built to the PHIUS+ 2015 Passive Building Standard consume 86% less energy for heating and 46% less energy for cooling (depending on climate zone and building type) when compared to a code-compliant building.  PHIUS has developed climate specific standards for all of North America .

The number of commercial-scale Passive House construction projects is growing, and growing fast. And this is not just a European phenomenon. In 2016, according to Canadian think-tank Pembina Institute “the growth of Passive House certified buildings in North America during the last year has been particularly dramatic, more than …doubling the square footage.”   Recently, the Massachusetts Building Code now acknowledges Passive House:  PassiveHouse Planning Package (PHPP) is an Approved Alternative Energy Performance Model, for compliance with section C407 (780 CMR Chapter 13 New subsection C407.7).

As the Passive House concept continues spreading around the world, it is exciting to see the application of newer technology to meet the special ventilation requirements of Passive House buildings, providing great energy savings and occupant comfort all at the same time.  Swegon, represented by DAC, manufactures a very compact and efficient Passive House certified energy recovery ventilator, the Swegon Gold unit, that has been used in Europe for many years and can ensure your project meets the PHIUS standards.


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Adiabatic Humidifiers – Now OK for Hospitals

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ASHRAE regulation 170-2013 has been updated with an addendum, which changes the requirements on the technology needed to humidify hospital environments, allowing the use of adiabatic humidifiers.

Historically, humidification in hospitals and particularly in operating rooms has almost always been provided by isothermal humidifiers, which produce steam. Steam is notoriouHigh Pressure Humidification Spraysly a natural disinfectant, as most pathogens are immediately deactivated when exposed to temperatures as high as 100°C; furthermore, steam is safe in terms of spreading contaminants, as it does not carry bacteria nor other microorganisms as droplets of water may.

On the other hand, steam humidification is also the most expensive in terms of running costs, as it requires a high amount of energy to bring water to boiling point and turn it into steam. When this process is performed by immersed electrode humidifiers or heater humidifiers, which consume electricity, it can become extremely costly, especially for large hospitals with high humidification loads. When available, it would be better to use gas-fired humidifiers due to the lower cost of the energy source.

A significant change to this status-quo has been made by the new ASHRAE regulation, allowing the use of adiabatic humidification such as those provided by Carel inside healthcare facilities, with important consequences on energy consumption.

The most advHigh Pressure Humidification Gridanced adiabatic humidifiers have reached a level of hygiene very close to steam, while bringing a huge decrease in operating costs! Isothermal humidifiers by nature consume about 800 W of energy per l/h of humidity produced, while high pressure adiabatic atomisers consume just 4 W of electricity – needed to operate the pump – to deliver the same capacity.


High Pressure Humidification PanelNot all adiabatic humidifiers are suitable for healthcare facilities however: only high pressure atomisers with certain features to safeguard hygiene level are allowed. These features include the use of reverse-osmosis to treat the water, UV-C sterilisation, sub-micrometric filtration and moisture eliminators; water in the piping must be continuously circulated or drained completely if not in use.


For more information on Carel and Adiabatic Humidifiers:





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Indoor Pool Dehumidifier – With NO Outdoor Condenser?

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Can you build a pool dehumidification unit without a remote condenser?  

Today,  the answer is YES!   Seresco  has introduced a new revolutionary design that needs no outdoor condensing unit.  This is really ingenious; complete dehumidification with cooling and no External Condensing Unit.  Yes, correct, Seresco has now developed a unit that is a complete package providing dehumidification and cooling all in one indoor unit.



The Optional R3 Expansion Module can now be added to Seresco NE Series Dehumidifiers in sizes from 4 to 8 tons.  The module allows dehumidification and cooling capacity in one single unit.  That’s right, no outdoor condenser, just one unit.  The waste heat from the unit can be recycled to heat pool air or pool water (like typical units).  Additional heat is transferred to the exhaust air stream through a heat exchanger and exhausted to the outdoor environment.  The exhaust fan and coil are integral to the unit.  It’s simple and it works.

Awesome Features:

  • NO OUTDOOR CONDENSER – Unit provides full A/C capacity with no outdoor condenser (using an evaporative condenser in the exhaust airstream).
  • No site refrigeration work.
  • Refrigerant charge reduction by up to 80%
  • Compact – Mounts underneath NE Series main unit, adds only 18 inches in height. Can be shipped and mounted separately.

This is a real breakthrough for the industry. Call us now for selections and further information.

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Project Snapshot: 60 State Street – Field Erected AHU

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Project Name: 60 State Street – 10th Floor, Boston
 Architect: Dyer Brown Architects
Mechanical Engineer: C3 Commercial Construction Consulting, Inc.
Mechanical Contractor: Northeast Mechanical
Equipment: Custom Field Erected Air Handling Unit
Manufacturer: Custom Air Solutions by Cambridgeport
Size: 25,000 CFM
DAC Sales Engineer: David Goodman

David & Harry – DAC’s Best Site Supervision Team

Project Overview:

The new Arup offices located at 60 State Street, 10th Floor are the first to be certified for a new healthy building certification called WELL which overlaps with a number of requirements for LEED-certified environmentally friendly buildings aimed at reducing a building’s greenhouse gas emissions and water and energy consumption.  There are seven new projects in Massachusetts being designed to be WELL certified.

Natural and indirect lighting, materials, work areas, sound, food and snack choices, and HVAC all get special attention with features necessary for a more healthy work environment.  Studies prove newly remodeled office space such as this greatly increase productivity and decrease absenteeism by placing more attention (and cost) on building considerations. Read Boston Sunday Globe article.

The existing unit was very old and rusted but compact and squeezed into the mechanical space and ducts.  The new unit occupies the same footprint but the Arup Fit-out also called for more air for improved ventilation.

The 25,000 cfm unit was designed to be 100% Knock Down construction.  It was taken up the elevator in pieces and completely built in the mechanical room by the Northeastern Mechanical team with Cambridgeport supervision.  Per the WELL standard, the new unit has Pre and MERV 13 filtration, and UVC lighting was also deployed on the cooling coil to prevent any bacterial growth.   The unit also has 3 ECM fans which do not require any VFD.


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New Look DOAS Units – less space, less noise, less cost

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Swegon GOLD RX: Air handling units with unbeatable advantages

GOLD enables designers to re-think system design. Its extra small footprint and ultra-low sound levels make it possible to place air handling units in non-traditional spaces such as in close proximity to occupied rooms. In addition to maximizing usable space, GOLD’s decentralized design also allows smaller plenums and shafts (smaller ducts), individual tenant metering, flexible tenant time scheduling and reduced sound and energy consumption. Combining both unit and controls optimization, GOLD provides unparalleled energy efficiency levels, reliable operation, and fast commissioning.

RX models include direct-driven supply air and return air fans, supply air and return air filters and rotary heat exchanger; up to 85% total energy recovery; air flows up to 16300 cfm; variable speed regulation of the rotor and cooling energy recovery.

Smallest Footprint 

The GOLD Dedicated Outdoor Air System (DOAS) unit has the smallest footprint in the market. Up to 40 sq.ft. per unit can be saved and converted to leasable area. There will be no problem getting GOLD to fit.

Lowest Operating Cost 

The GOLD has been designed to optimize the EC motors, unit specific fan design, and casing combination for a superb overall efficiency. This, coupled with wheel efficiencies of 85% and serviceability of the fan/motor and filters, delivers the lowest operating cost to the building owner.

ComfortImproved Occupant Comfort 

GOLD has the lowest overall sound power levels of any unit in its class. Units can be placed closer to the occupied space and your risk of a client complaint due to a sound problem is significantly reduced. In office buildings, GOLD helps improve employee effectiveness and attendance by improving IAQ and thermal comfort.


GOLD comes with integrated controls which have been installed in thousands of buildings across the globe. The controls are the brains behind the best-in-class efficiencies, providing unbeatable value of ease of specification, reliability, and total project cost.

Certified Passive House Component

The high energy efficiency and efficient heat recovery has awarded the GOLD RX (sizes 04-35 and 50) with a Passive House Certificate from the Passive House Institute. This makes GOLD globally unique as it is the first ventilation unit capable of high air flows (<5300 cfm) that fulfills the requirements of the passive house certification.

Learn more on the Swegon GOLD RX

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Project Snapshot: Ayer-Shirley High School | Thermal Composite – DOAS Units

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Project Name: Ayer-Shirley High School
 Architect: Symmes Maini & McKee Associates
Mechanical Engineer: Symmes Maini & McKee Associates
Mechanical Contractor: E. Armanti & Sons, Inc.
Equipment: 4 Dedicated Outdoor Air Handling Units
Manufacturer: Annexair
Size: 3,500, 5,500, 10,000 and 12,000 CFM
DAC Sales Engineer: Pat Will

Project Overview:

The towns of Ayer and Shirley, on Massachusetts’ northern border, faced precipitous student enrollment declines as a result of the closure of the Fort Devens military base a decade ago. The towns came together to form a new district and share resources, and also to maintain a critical enrollment mass.  Whereas the original 1960 building once housed over 1,000 students, the new grade 9-12 population was planned for 460 students. The Massachusetts School Building Authority prescribed a combined middle and high school. SMMA convinced the communities to rethink the logic of this assumption by thoroughly analyzing the physical attributes of the building, and then stepping back and master-planning the District’s entire portfolio of schools.

Designing for Educational Success

Small, undersized spaces on eight distinct levels separated by narrow corridors and an underutilized open air courtyard with isolated community use spaces and tiny lobbies divided the student body and after-hours public uses making the building hard to navigate and supervise. The poor condition and environment led to over 100 students choosing alternative, out-of-district school options. SMMA aimed to maximize opportunity for pupil and adult interactions, incorporating corridor learning commons; teacher planning centers; small group rooms and larger flexible classrooms, with four teaching surfaces; and flexible, mobile furniture systems into our design. The building has remained occupied during construction, requiring careful shifting of spaces to allow for seamless, uninterrupted education.


HVAC Highlights:

  • DOAS Units
  • GAS Heat
  • Enthalpy Wheels
  • Thermo-composite panel system

The units on the Ayer Shirley High School project were supplied by Annexair and incorporated their Thermo-composite panel system.  The design looked for replacement units that would weigh the same as original and provide 30% more capacity.  Weight was a key design factor.  The Annexair units are 30% lighter than traditional steel units.  So we were able to satisfy the design criteria with a lighter unit.  Additionally the units come with a lifetime warranty against corrosion.    Best of all they are the same cost as traditional steel units.

Take a look at the specification for key features.

UNIT HOUSING SPECIFICATION (Thermo-composite) The unit housing shall be no-through metal with 2’’ Thermo-Composite and foam panel construction – interior and exterior.  No-through metal construction will be inherent to all the component construction in the assembly.  All panels and access doors shall be double wall construction with R14 foam insulation for every 2” of construction.  All foam insulation must be Greenguard certified®. Unit casing will have no exterior condensation at interior AHU temperatures down to 43F while unit exterior conditions are maintained at 95 F dry bulb / 85 F wet bulb.  The panels shall be tested in accordance with SMACNA and ASHRAE 111 to have a deflection of no more than L/1150 at 10’’ and withstand air pressures up to 8” w.c with less than 1% leakage.  Fire resistance of the panel will be in compliance with UL 94.

Thermo-Composite panels shall be provided for the entire unit construction, including but not limited to, walls, doors, floors, roof, interior partitions, and electrical compartment.  The frame shall consist of anodized extruded aluminum profiles which incorporates a thermally broken construction; welded together for reinforcement and insulated for superior thermal performance.  Base structure shall be fully welded and have integral lifting lugs which can be removed once the unit is installed.  All roof and side wall seams shall be positively sealed to prevent water and air leakage.  Panels will be non-load bearing type.

Access doors shall be provided to all major components to facilitate quick and easy access. Access doors will be made from the same material as the unit casing and shall incorporate thermal break construction.

Annexair - Composite Panel - Picture1Unit shall have the entire exterior finished with a PVDF coating designed for UV resistance. Paint shall pass ASTM B117 3000-hour salt fog resistance test and ASTM D4585 3000-hour moisture condensation resistance test. In addition, paint must meet AAMA 620-02 standard for color, chalking, gloss retention, and abrasion resistance. The air handler unit casing shall be provided with a lifetime warranty against corrosion resistance under normal use.

Related Thermo-composite Panel Blog Post:

For More Information - askRick




Project Snapshot: Tufts University Central Energy Plant – Custom Air Tunnel

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Project Name:  Tufts Power Energy Plant
Owner:  Tufts University
Mechanical Engineer:  vanZelm Engineers
Mechanical Contractor:  J.C. Higgins Corp.
Equipment:  Custom Air Tunnel, Cooney Freeze Block Coil
Manufacturer:  Cambridgeport (CAS) Cooney Coil
DAC Sales Engineer:  David Goodman

Tufts University – Central Energy Plant 
Tufts University has built a new Co-Gen Central Energy Plant.  The new plant is located on Boston Avenue just south of Dowling Hall and will replace the aging, 60 year old existing plant.  The Central Energy Plant will provide electricity, steam, hot water for heating, and chilled water for cooling to the upper campus and the new Science and Engineering Complex.  This project is part of the University’s commitment to sustainability and modernization of their infrastructure.

DAC Sales Assisting with Custom Solution:
The plant was designed with two sets of air funnels both with heating coils with by-pass dampers.  One set is for the plant MUA and the other Combustion air for the Caterpillar Co-Gen.  David Goodman was providing the standard two row HW coils to J.C. Higgins but was also asked to provide the double wall panels and access doors.  These panels could only be designed and built after measuring the tunnel and deciding as a team how to assemble them around the tunnel beams, HW coils, fans, filters, sound attenuators and dampers.  The panel system was provided by CAS in Canton.  Having the panels made near the job site made it very fast to turn around sections as the components were set in place.

Addition of Cooney Freeze Block Coils:
As a part of an owner request, Cooney Freeze Block Coils were added to the project.   Cooney Coils provide the system with the highest level of protection against coil freeze up.  Advantages over standard coils include:

Cooney Freezeblock Coil

  • Expansion relief headers equipped with pressure and temperature sensing valves discharge a small amount of water as a coil begins to freeze
  • Valves are designed to reseat after discharging to prevent flooding after coil thaws
  • All coils and valves are pre-assembled and tested at the factory prior to shipping
  • Designed to dramatically reduce future maintenance, downtime, and premature coil failure
  • In many cases, eliminates the need for glycol which increases efficiency
  • All Cooney Freeze Block Coils come with a 3 year warranty


Some of the new facility’s features include:

  • A cogeneration plant, which will provide 4 MWs of power, reduce energy costs for the Medford campus by approximately 20%. The university is taking a fresh approach to greenhouse emission analysis to be posted in the near future.
  • Three new high-efficiency steam boilers, which will replace the less efficient boilers in the existing plant
  • Efficient chillers and cooling towers, which will provide air conditioning to the new Science and Engineering Complex, Tisch, and can be expanded to serve additional buildings in the future
  • Increased reliability of the electrical power supply to the Medford campus
  • A glass façade, which will allow the Tufts and Medford communities to see what is happening inside this modern facility
  • Landscaping with native plants


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Project Snapshot: Gordon College – Pool Dehumidification Unit

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Project Name: Gordon College – Bennett Center
Owner: Gordon College
Mechanical Engineer: CSI Engineering
Mechanical Contractor: Merrimack Valley Corp.
Equipment: Pool Dehumidification Unit
Manufacturer: Seresco
Size: 24 Ton Modular 2-compressor 200 Series dehumidifier
DAC Sales Engineer: Craig Ashman

Gordon College – Bennett Center  The Gordon College Bennett Center is a 78,000-square-foot athletics and recreational sports facility. The center was completed in October 1996 and in 1997 won Athletic Business magazine’s Top Ten New Facilities Award for its design and usability.  Incorporated in the center is a Competition Swimming Pool.

The Problem:   The original Poolpak pool dehumidification unit was no longer functioning to dehumidify the pool space.  A new unit was required but space to access the mechanical room was very limited.  The replacement equipment would need to fit through existing access doors.

The Solution:   The replacement equipment was recommended by Seresco.  The manufacturer selected a 24 Ton Modular 2-compressor 200 Series dehumidifier.  This is a really clever concept developed by Seresco.  This ingenious innovation provides twice the dehumidification in the same footprint as a regular unit. It’s a compact, 2-stage system that provides scalable capacity and performance of two complete systems in one, controlled by a single, sophisticated brain.  The best part is that this system can be broken into two separate sections that fit through a 32″ doorway.  This was the answer to a very difficult problem.

Gordon college 020

Additional Features:  

  • Glycol Cooled A/C by a Fluid Cooler –  About 40% of the units Seresco provides use fluid coolers in lieu of Refrigerant Based ACCU’s.  This is a standard product offering in their Protocol Line of Pool Dehumidification Units.  In the Pool Dehumidification Unit Seresco provides a heat exchanger and a pumping package. In the heat exchanger the refrigerant loop dumps the rejected heat to a glycol loop. It is then pumped to the Fluid Cooler on the roof. Piping is PVC from the Pool Dehumidification Unit to the Fluid Cooler. The Fluid Cooler distance can be nearly anything (600 feet is not a problem).
  • WebSentry –  This application was also equipped with WebSentry,  Seresco’s online monitoring, reporting and service optimization tool.  The 24-7 WebSentry monitoring then allows Seresco to remotely monitor over 100 performance parameters of the dehumnidifer using sophisticated algorithms to analyze and identify potential issues and maintenance requirements, long before they become potential problems.

Design Advantages: There are many reasons why this type of application makes a lot of sense.

  • 45 to 171 lbs. per hour of moisture removal and 3,000 to 16,000 CFM of air handling in the absolute smallest footprint possible
  • Seresco model 214, which can actually fit through a 32 inch doorway delivers up to 79 lbs. per hour of moisture 6,800 CFM
  • Fully modular system – 2 compressors, 2 supply air fans, 2 cabinets in one package
  • Can be easily split at the job site into two pieces for retrofit in existing buildings – just a wire harness to connect, no refrigeration piping is affected
  • Can have a single phase 12 ton system
  • 2-sided service access for tight installations
  • Horizontal and Vertical configurations
  • Flexible supply air openings – multiple openings also possible
  • WebSentry® Internet monitoring and control
  • Touch screen CommandCenter® control systems
  • Premium compressor protection
  • Premium corrosion resistance

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Project Snapshot: Amalie Arena – Home to the Tampa Bay Lightning

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Amalie Arena - PictureProject Name:   Amalie Arena Tower Air Handling Unit Replacement

Location:   Tampa Bay, Florida

Project type, building type:   Sports Complex

Equipment:  Wrap Around dehumidification heat Pipes

Manufacturer:  Heat Pipe Technology

Engineering challenges

Before Heat Pipe Technology’s involvement, the arena’s ice quality was ranked near the bottom among NHL arenas. This was largely due to the Tampa Bay area climate, where high humidity makes it difficult to create and maintain top-quality ice, which requires dry air. Before HPT arrived, the Amalie Arena was generating around 60% relative humidity (at 65°F) when the NHL recommended 40% relative humidity at 60°F, with a dew point of 36°F.


After rejecting a roof-top gas-heat desiccant system as costly and bulky, Amalie Arena installed HPT’s wrap-around Dehumidification Heat Pipes (DHPs). The DHPs use a proprietary system commonly installed in large-scale HVAC applications that require lower humidity, such as hotels, universities, specialty manufacturing, and hospitals.

HPT’s DHPs, which have no moving parts and require little maintenance, use the “phase change” of the working fluid in Amalie Arena’s HVAC system to precool outside air before it enters the cooling coil and reheat the air exiting the cooling coil using recovered heat. This reduces the load on the cooling coil, while lowering the dew point. HPT’s modeling shows that its DHPs remove close to 350 total tons from the cooling load, and roughly four million Btus per hour of reheat, which is necessary to maintain comfortable conditions for over 20,000 fans. This will save the Amalie Arena an estimated $600,000 per year in energy costs.

“Not only did the heat pipe solution allow us to keep all construction inside the existing mechanical rooms and off the roof, greatly reducing first costs,” said Mike Tappouni, of Tappouni Mechanical Services, “but it allowed us to reduce overall energy consumption as well, despite the need for colder water from the chillers. In addition, the reduction in maintenance cannot be understated. It literally went from a maintenance nightmare to a dream.”

About Heat Pipe Technology

Heat Pipe Technology, a division of MiTek®, a Berkshire Hathaway company, is the innovation leader in passive energy recovery and dehumidification systems for commercial and industrial applications around the globe. Employing the very latest in passive-heat-transfer technology, Heat Pipe Technology designs and supplies the core energy recovery technologies to the world’s leading commercial air-handling equipment manufacturers. More info:

Blog post materials provided by:

Media Contact: John D. Wagner  919-796-9984


For More Information - askRick





Freeze Block Coil – Technology Based Solutions

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A Freeze Block Coil is the Best Way to Prevent Frozen Coil Damage

Freeze damage is the leading cause of premature HVAC coil failure. Frozen fluid coils can result in severe damage to the coil, system downtime, expensive repairs and/or replacement and in some cases flood damage throughout the building. This is a new coil that we are looking at to help in our custom AHU designs.  The Cooney Freeze Block Coil is designed specifically to protect HVAC coils from freeze-related damages.

Learn more on the Freezeblock coil:  Freezeblock Coil Video
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More questions about Freezeblock Coils;