PDT U - Exterior Wall System Review

Bob gesturing_group.jpg

Bob Curtis’s Long-Awaited Talk on the Evolution of PDT Wall Systems

Paul looking at Roxul.jpg

Bob Curtis, PDT’s guru of codes and wall systems, started with the typical commercial wall system of twenty years ago, which resembled the “house system” still used in single family construction, and advanced to today’s rainsceen technology.  He paused along the way to discuss the evolution of our choice of wall insulation, from itch-scratchy fiberglass batts installed between steel studs, to supposedly continuous foam plastic insulation boards interrupted by metal zee furring, to our present system of continuous mineral fiber board insulation, penetrated only by fastener or rainscreen support brackets.

Kathy_holding sample aloft.jpg

Describing the constant battle to keep moisture out of walls, Bob described the old walls as ineffective because of their potential to generate condensation within the wall assembly due to thermal bridging across steel studs.  Bob repeated the PDT mantra of favoring simplicity over complexity in wall assemblies by reducing the number of wall assembly components whenever possible.  Multiple layers of building materials, insulation materials, and membranes with a variety of permeabilities and water retention characteristics can trap moisture within a wall, which can damage the walls and lead to indoor air quality problems. 


Bob contrasted this with the current PDT walls, constructed with a single plane combined air/water/vapor barrier, and a single plane of continuous insulation, that are able to self-regulate their moisture content by drying to the interior or to the exterior as required by changing ambient conditions of temperature and humidity.

Bob reviewed the pros and cons of several of the newer rainscreen “clip and rail” systems designed for use with mineral fiber board insulation and discussed the challenges of maintaining the integrity of a single plane air/water/vapor barrier that is subject to numerous penetrations from fasteners, conduits, and structural members. 

PDT is currently designing two major schools to the 2015 edition of the International Energy Conservation Code, above the standards required by the State of Maine.  Our office standard building enclosures for all project types typically exceed the current State standard.  In the evolving world of building enclosure technology, we always try to anticipate, monitor, and adopt improvements in our choice of systems and materials.  This effort makes our buildings tighter, dryer, more comfortable and more energy efficient than ever, with higher R-values and lower utility bills.

–Robert R. Curtis, LEED AP BD+C, Maine Licensed Architect, holds a Maine Code Enforcement Certificate and is an associate of PDT Architects.


Legendary Stevens Avenue

Last night I walked over to our community garden plot with my husband and our dog, greeting neighbors (and their dogs) along the way. Within five blocks I can walk to the library, the Quality Shop, Pat’s Meat Market, Baxter Woods, Siano’s restaurant, Roy’s Shoe Repair, the Sewing Shop, Jet Video, and ten other neighborhood amenities. My neighbors walk their kids to school past my house, and from my kitchen I hear games going on in the Deering High School playfields: soccer camp, band practice, lots of cheering.

I live very close to legendary Stevens Avenue in Portland, Maine, the only street in America, we are fond of saying, where you can be born, go to kindergarten through graduate school, work, get married, die, and be buried, all without leaving the street. I think the “born” part refers to the proximity of the old Brighton Medical Center, which no longer does births and isn’t strictly on Stevens anyway, but otherwise it’s true. Stevens Avenue is home to numerous public and private schools, the University of New England, Maine’s only dental school, churches, Maine’s (probably) only Polish restaurant, Aubuchon hardware, coffee shops, and a tattoo parlor. And we all hope to end up under the elegant turf of Evergreen Cemetery.


Courtesy of Friends of Evergreen, friendsofevergreen.org

Until recently, though, my neighborhood, Deering Center, had an unfortunate gap in independent housing for older adults. The houses are modest and vertical. If you can’t do stairs, and you aren’t ready to move into Deering Pavilion, you can’t live in this walking paradise. As my neighbors and I age and retire, a walkable neighborhood promotes not only healthy exercise but the added pleasure of maintaining social bonds. Moving to find simplified one-floor living, cutting the casual ties of neighborhood life, is not only painful, it’s disorienting and isolating.

Reserve your seat at our Bangor half-day forum ‘The Case for Walkability: Health, Economic Development, and Sustainability’ on September 19th. Click here for more information.

Fortunately, construction has begun on the former Sisters of Mercy Mother House, a conversion of the convent into senior housing with the potential for three new buildings of more senior housing to be built behind it. And a smaller apartment building is under construction right next to Roy’s Shoe Repair. As my friends and I get our joints replaced and have a harder time carrying the laundry up two flights, we can look forward to appropriate, convenient housing that makes the legend of Stevens Avenue closer to true.  We’ll still be able to live our lives—cradle to grave—and walk to everything.

Susan Ransom
Marketing Director, PDT Architects
GrowSmart Maine volunteer, Deering Center resident

This blog post originally appeared on growsmartmaine.org

PDT and Passivehaus_ME Annual Meeting + passivSLAM!

Architects and Passive House affiliates from Connecticut, Massachusetts, and Maine gathered at the Friends School of Portland for the annual meeting in April. PDT Architects has joined Passivehaus Maine to help expand sustainable building practices and work towards net-zero buildings in New England. Architect Keegan Carmichael attended the meeting.


Friends School Tour:

Friends School Tour:

Since the Friends School has moved to their new building, enrollment has drastically increased. The wall assembly is composed of a 2x6 dense-packed cellulose wood stud with 4” of exterior rigid insulation on strapping and a metal siding. Due to the restriction of passive house air sealing needs, the school does not have a commercial kitchen. The school wanted the most energy efficient building possible, and small tweaks in the building systems allowed for significantly reduced energy bills. Heat pumps run almost 24 hours a day to help regulate the interior temperature. With small amounts of energy used to regulate the temperature, the school avoids peak demand charges and has less stress on the units. Solar panels on the roof pour electricity back into the grid and help with the school’s goal of being net-zero energy.

Viridescent House Tour:

Viridescent House Tour:

Due to zoning codes, the Viridescent House currently operates as an office but can be converted back into a house. The office is equipped with a shower and full kitchen, with a south-facing wall that illuminates the open office space and atrium. The building assembly is wood I-joists with dense-packed cellulose fastened onto 2x6 wood studs which sit on a slab on grade on top of 8” of extruded polystyrene. Tidesmart, the client, wanted an extremely efficient building, and with the combination of an airtight super-insulated building and solar panels, the Viridescent House produces twice as much energy as it consumes.




Waldorf School Tour:

Waldorf School Tour:

The new school building currently under construction in Freeport will house educational programs and expand the campus. The building envelope is an 8” wood stud with dense-packed cellulose and 4” of mineral wool. Oriented for a passive solar design, the structure will use ductless mini splits for air conditioning. Every classroom has a sink for program flexibility. The new building, with the aid of passive house strategies, is pursuing Maine advanced building certification.

PDT Architects visits maker spaces in RI with Caribou Middle School

Here is Leland Caron, principal of Caribou Middle School, at AS220 in Providence last week as part of our tour of maker spaces, innovation centers, and project -based learning environments. We spent the better part of two days visiting schools and talking to educators as we begin to design RSU 39's new innovation center.


Jane McCall, assistant superintendent of curriculum and instruction at RSU 39; Leland Caron; Alan Kuniholm and Chelsea Lipham of PDT Architects; and Adam Tilove, head of the Jewish Community Day School of Rhode Island, visited the Rhode Island School of Design, Moses Brown School, Brown University, Wheeler School, AS220, and Berwick Academy, where they visited maker spaces, innovation spaces, and project-based learning environments.


Current designs for the new pre-K-8 school in Caribou call for a maker space in the heart of the school, where students will learn to define problems, collaborate on solutions, choose materials, and gain skills in many different disciplines.


--Alan Kuniholm

PDT at P.A.T.H.S. with ACE mentors

Portland Masonry Company hosted a demonstration at PATHS (Portland Arts and Technical High School) for ACE students GIVE DATE HERE. PDT’s Adam McKinnon, Alyssa Phanitdasack, and Keegan Carmichael attended the bricklaying demonstration by master mason Ed McGarrity. Students learned the fundamentals of masonry as well as a brief history of decorative styles that are prevalent in the Old Port. PATHS offers courses in building trades with a hands-on approach to learning. A list of programs offered at PATHS can be found in the link below.


62 Spring Street Approved for Low Income Tax Credits

62 Spring Street Approved for Low Income Tax Credits

“We’re thrilled that this project is going ahead,” said Ethan Boxer-Macomber of Anew and Brian Curley of PDT Architects, “and we’re delighted to be partnering with Auburn Housing to provide much-needed family housing in the heart of Auburn.”

PDT volunteers with the ACE Mentor program

PDT volunteers with the ACE Mentor program

Alyssa Phanitdasack, Matt Pitzer, Keegan Carmichael, and Adam McKinnon of PDT Architects are volunteering with the ACE Mentor Program, an after-school program for high school students interested in the architecture, construction, and engineering fields.

Complex floor at Freeport High School

Here’s the cast-in-place concrete floor being poured at the lower level of the Freeport High School addition. Workers are leveling the freshly placed concrete and performing various finishing activities.

What might seem like a simple floor system actually has many components that work together. The yellow material being covered in concrete is the under-slab vapor retarder that keeps moisture in the soil from entering the finished slab. A layer of extruded polystyrene insulation is hidden underneath the vapor retarder. Orange radiant heat tubes, attached to a layer of welded wire mesh and embedded in the concrete, will provide a comfortable and efficient source of heat for new rooms on the building’s perimeter. Blog post by Bob Curtis.

Photographing the Capital Judicial Center #1

Beautiful September Saturday morning, early, walking out over the Kennebec on the pedestrian walkway of Augusta’s Memorial Bridge. The bridge isn’t vibrating nearly as scarily as it had during the scouting trips. There’s a barrier between us and the cars and trucks, which is good because they’re whizzing by only a few feet away. I’ve explained to Sandy, the photographer, and Justin, her assistant, that we don’t have to use a ladder to shoot over the chainlink fence, and we don’t have to shoot through the holes. We can just shoot under the fence.

What is a Green School?


PDT recently led green schools presentations for each of our two newest school clients, RSU 39 in Caribou and MSAD 75 in Topsham. The presentations were educational, inspirational, participatory, and the beginning of our green schools goal setting process for each of the projects.

What is a Green School?

A green school is healthy, comfortable, energy efficient, material efficient, and easy to maintain and operate. A green school is located on an environmentally responsible site, is adaptable to changing needs, is safe and secure, and is a building that teaches. The design, construction, and operations of a green school are based on long term, life cycle costs that result in minimized environmental impact, improved occupant health and productivity, and reduced long term operational costs.

Benefits of a green school

Benefits of a green school

How do we design a green school?… With an integrative design process.

An integrative process encourages project teams to identify shared goals early in the design process, analyze synergies between all parts of the project, and explore multiple strategies to meet project performance goals. The process embeds the value and meaning of sustainability into how we work on our projects.

What this means for our work in simple terms is that we frontload the design process. • We holistically understand the existing context. • We set shared goals with the owner prior to design. • We bring all team members to the table early in the design process. • Applying systems thinking, we set up feedback loops and other collaborative procedures to optimize all the decisions we make.

We will take the conversations from each of the green schools presentations and begin to prioritize unique sustainability goals for each project. We will carry those goals throughout each project - weighing our options, considering life cycle costs, looking at synergies between systems, and making sure both clients end up with a cost effective, healthy, and environmentally friendly building that can truly enhance productivity and make education enjoyable and rewarding.

Green Education at the Courthouse

energy savings
energy savings

The Capital Judicial Center in Augusta, Maine, designed by PDT Architects, opened in March. The 4-story 120,000-sf courthouse combines superior and district courts with other court functions on a steeply sloping site adjacent to the historic Kennebec County Courthouse, to which it is linked by a second-floor bridge. The design observes ideal courthouse planning principles, with separate, secure circulation for staff, detainees, and the judiciary.

The project is targeting LEED Silver certification. High efficiency zone heating and cooling is provided by chilled beams and radiant floor heating. One of the most stunning features is the natural daylight that pours into the public lobby and corridors as well as into the courtrooms and workspaces.

Green Education

In addition to the building itself, a comprehensive green education program will be installed in the courthouse later this summer. Green education signage will be installed into the building's spaces to educate the occupants and visitors of the green building features of the courthouse. The signage will be installed in both the public and secure staff areas. Rack cards summarizing the sustainable features of the building will be available in the first floor public lobby and sustainable living facts will be on the digital displays throughout the building. For a preview of the signage, see below.

Green Education1-sml
Green Education2b-sml
Green Education3-sml

Passive House Not Only For Homes

On March 16th, Günter Lang, Austrian passivhaus expert, gave a presentation on the Passive House building standard. The term Passive House refers to a rigorous, voluntary standard for energy efficiency in a building. A project that follows Passive House principles results in an ultra-low energy building that requires little energy for space heating or cooling. Thermal comfort is achieved to a maximum extent through passive measures (insulation, heat recovery, passive use of solar energy and internal heat sources). Günter Lang’s presentation demonstrated the great potential and versatility of the Passive House standard not only for single family residences which are most commonly associated with the standard, but also for apartment buildings, affordable housing, schools, courthouses, healthcare, office buildings, retrofits and entire city districts. Sponsored by passivhausMAINE and AIA Maine, the talk referenced a variety of large scale building types and a variety of construction types to show that there are many ways of building a Passive House building.

Some Firsts and Largests

RHW Tower

First Passive House Skyscraper The corporate headquarters of Austrian Raiffeisen-Holding in Vienna, rising 240 feet, only 60 feet wide, and with a glazed double-skin façade, exceeds our previous perceptions of what a Passive House looks like, and for the first time a skyscraper was designed and built (by Atelier Hayde Architekten and Architekt Maurer) to meet Passive House standards.

Three main factors allow the building to meet the Passive House standard:

  • Thermal efficiency of the well-insulated double facade
  • Use of daylight to reduce electrical lighting requirements
  • Advanced mechanical systems

The World’s Largest Passive House district Heidelberg’s Bahnstadt is the world’s largest Passive House district. Bahnstadt is a model for how Passive House can become the standard for large scale developments, districts and entire cities.

Heidelberg’s newest city district, Bahnstadt is being built completely to the Passive House Standard. The basis for this is an integrated energy concept that was developed and passed by the Heidelberg City Council alongside urban development and other key concepts necessary for such a scheme. The Passive House Standard is legally binding through contracts and was set via a development law mechanism. Additionally, compliance with the Passive House Standard has been integrated into the building permit process.  Special energy consulting and financial aid is available for builders and developers.  Currently, the first segment of residential building is mostly finished, already offering living space for some 1,500 people. The entire residential part of the project is currently two years ahead of schedule due to the high demand. In addition to living space and a kindergarten, the district will also offer Passive House cafes, restaurants, office space, a laboratory, a supermarket, a movie theatre, and a building supply store. (Passive House Institute press release, 30.06.2014 )

LifeCycle Tower

Prefabricated Wood High-Rise Construction (or An 8 Story Building Built In 8 Days)The LifeCycle Tower ONE in Dornbirn, Austria was completed in 2012 and is a PassiveHaus certified high rise constructed with prefabricated wood and reinforced masonry components. Prefabrication allowed for the 8 story building to be assembled on-site in 8 days. LifeCycle Tower TWO, the Illwerke Montafon Center in Montafon, Austria, of the same construction type, was also completed in 2012. The Illwerke Montafon Center is 5 stories tall, with a basement, and has approximately 100,000 sf of floor space. These buildings demonstrate how passive house standards can be applied to both mid- and high-rise wood construction and prefabricated modules.

Simple buildings with simple systems

Wood towers and Passive House skyscrapers will be seen more and more in the future. The double facade will be used more often around the world. A precedent has been set for pre-manufactured Passive House buildings that can be used for temporary housing and then relocated to different sites as necessary. Gunter Lang emphasized that the Passive House standard can successfully be incorporated into any building design (everything emits energy!) and implemented into local policies and codes as well.

  • Design simple buildings with simple systems.
  • Design buildings that passively use the sun, water, earth and air as much as advanced building systems.
  • Design with energy use reduction and a high performance envelope in mind.
  • Be a good advocate. Most buildings built now will need to exist in the future without reliance on fossil fuels so design for that now.

Passive House Case Study Resources

Passive House Database (you can even add your own Passive House project to the database!)

Passive House Regions (PassREg)

Passive House 2014 Awards

International Passive House Association (iPHA)