For one thing, the house is larger than the typical single-family Passive House, and has a higher glazing-to-opaque wall ratio. It also has three separate zones: the main downstairs living area, the upstairs bedrooms, and a private guest wing. Each of these zones has different exposure to the sun, so we needed a way to accommodate the diverse loads throughout the year. To further complicate the picture, the designer made use of every interior space, so there was nowhere to hide ductwork.

These complexities pretty much ruled out the more common ways of heating a Passive House — like adding a resistance element to the ventilation system or using a mini-split heat pump. Instead, a low-temperature hydronic radiant floor system was installed, with hot water provided by a Daiken Altherma air-to-water heat pump. The same unit also provides all the domestic hot water for the house. The all-electric Altherma has very high efficiency — over 300% when it’s heating low-temperature radiant water — which means it produces three times the energy required for its operation. It’s also variable speed, so it modulates with the load, which further reduces its electric consumption. Watch as mechanical contractor Jonathan Cohen of Imagine Energy explains how the Altherma system is configured, and describes the zone-control strategies that maximize its efficiency.

In a Passive House — or any high-performance home, for that matter — domestic hot water is typically a larger energy load than heating. To meet the Passive House standard, this means not only generating the hot water efficiently with the heat pump, but also reducing losses through the distribution system. We used a three-pronged approach in the Karuna project: First, the hot water supply pipes were carefully sized to reduce the amount of hot water left in the lines after each use. Second, every hot water line was fully insulated from the mechanical room all the way to the fixture. Finally, an on-demand hot water recirculation system was installed (rather than a conventional system that runs 24/7).

In the next video, Hammer & Hand’s Skylar Swinford describes the domestic hot water strategy, starting in the mechanical room and moving upstairs to the master bath, where he explains how motion-controlled hot water recirculation saves both water and energy.

A key feature of any Passive House is a flawless air barrier between inside and out. This prevents energy loss from air infiltration and exfiltration and allows the thermal insulation to perform at its rated R-value. But airtightness also means that the house requires mechanical ventilation. Unfortunately, many traditionalist builders still believe that tight houses have stuffy air, or that vent fans waste heat. In fact, with a properly designed Passive House, the exact opposite is true.

Here, Jonathan Cohen explains how the Karuna House’s heat recovery ventilator captures 90% of the heat from the exhaust air. The Zehnder unit delivers comfortably warm, fresh air throughout the house while using very little energy and making almost no sound. Jonathan also gives us a look at the Daiken heat pump’s outdoor unit, and explains the advantages of the air-source heat pump over a ground-source installation.

Beside being quiet, the Zehnder HRV is visually discreet. In this video, Skylar takes a walk through the house and shows us the small supply and exhaust ports. He also explains why controlled, balanced ventilation makes sense in any house: Besides saving energy, increasing comfort, and guaranteeing good indoor air quality all year round, it’s really the only way to know where the house’s makeup air is coming from:

One of the homeowner’s goals was to reach net-zero — that is, energy produced on site would equal the energy consumed annually. In an all-electric Passive House like the Karuna house, photovoltaic panels make great sense. Here, Jonathan gives us a look at the 9.9 Kw PV array, which in this case was locally sourced, right down to the cells manufactured by SolarWorld’s Oregon facility. We also get a stunning view of Karuna’s exterior.

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To do this, the team designed a wall assembly that carefully manages heat, air and moisture:

Starting from the interior edge of the assembly and working our way out…

Interior walls of the green building are finished with lime plaster, 100% natural and VOC-free, applied on 5/8” drywall. Next comes the stud wall, built entirely from Forest Stewardship Council® (FSC) certified wood, with high-density cellulose insulation (R-21) blown into the cavities between studs. (Though we built this stud wall from dimensional lumber, much of the green home building project is built with engineered wood to take advantage of the design flexibility and precision it affords – see “Cutting-edge framing is key to Karuna Passive House success.”) The cellulose insulation consists of recycled newspaper and naturally buffers moisture, contributing to the wall assembly’s durability. We used over 12 tons of the stuff at Karuna, easily dwarfing any other insulation used on the project, by weight.

See Project Supervisor Scott Gunter discuss installation of the cellulose insulation in this video:

Immediately outside the cellulose insulation layer comes the air barrier, one of the most critical elements of any high performance wall assembly. A ½” layer of plywood sheathing covered with a continuous, vapor permeable liquid applied membrane does the trick. Scott describes this structural air barrier here:

The air barrier prevents air from flowing through the wall and ensures that the cellulose cavity insulation performs at its highest level, much like a Gore-Tex jacket enables a sweater underneath to warm your body, shielded from air penetration and the moisture it carries.

The air barrier also keeps out wind-driven rain, protects sheathing and framing from moisture, and, because it’s vapor permeable, allows the wall assembly to dry out from the inside in the unlikely event that moisture intrudes to the interior portion of the wall assembly.

This air barrier is wrapped by the home’s winter overcoat, a 6”-thick exterior layer of foil faced polyiso foam (R-36) that brings the insulative value of the overall wall assembly to nearly R-60. The three layers of 2-inch foam nest into a superstructure of Z-joists that staggers each layer’s seams. Vapor permeable tape seals exterior seams. This continuous overcoat is key to the wall assembly’s performance and durability. In addition to allowing very little heat loss, it also protects the structural air barrier by keeping it warm and dry. The warm band of yellow that encompasses the air barrier layer in the diagram below comes thanks to these three layers of polyiso foam (coinciding roughly with the quite-cold purple, the cold blues, and the merely-cool green below).

Finally, the green building is wrapped with a rain screen system built of FSC-certified cedar siding held one inch off the polyiso foam by FSC 1×4 battens. The airflow that this rain screen cavity facilitates across the face of the wall assembly provides constant drying and drainage, ensuring longterm performance and durability. Scott describes the system here:

So we’ve built this great wall assembly, but every window opening on the house represents a big hole poked through. We know that the hull of our ship can’t have leaks, so window preparation and installation are mission critical to creating a high performance wall assembly. Our simple approach connects the home’s high performance wall with its high performance windows while avoiding thermal bridges, water intrusion and air leaks. See Scott discuss window preparation here:

And watch Scott’s demonstration of window installation here:

Moisture management is the watchword when creating a high performance building envelope like the one at Karuna. By controlling heat and air you control moisture (hence, the Heat Air Moisture, or HAM, focus of building performance experts), so we designed every layer in the wall assembly at Karuna to manage these three variables. But we also created an assembly with excellent drying potential so that if something unforeseen happens and moisture somehow enters the system, the wall assembly will be able to handle it. This ensures building envelope durability, the most fundamental definition of building sustainability.

See an annotated photo tour of the assembly’s layers:

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Why? To achieve Passive House-levels of energy performance (like those at the Karuna House) you need an advanced building envelope – airtight, vapor permeable, super-insulated. And while many of us think of a building’s four walls and roof when we picture its “envelope” or skin, all six sides of the cube are important. In high performance green home building the foundation’s thermal performance is mission critical.

Just as water in a bucket will find any hole present, thermal energy follows the path of least resistance out of a structure, the easiest leak.  An uninsulated foundation represents a gaping hole at the bottom of that bucket, allowing heat to leak away into the earth.  In fact, as the structure’s walls and roof become more insulated and more airtight, the pressure on the foundation and its performance just gets that much more intense.

So we built Karuna on a super-insulated layer of foam, a time-tested practice. Major infrastructure projects (read, bridges and highways) are routinely built on top of foam. And thousands of sturdy, long-lived high performance buildings have been built on the stuff.

Read on to learn more about how it all worked at Karuna and to access videos and Field Notes posts about the process…

Excavation

Excavation at Karuna carefully balanced “cut” and “fill” onsite to eliminate the need to truck dirt to and fro, and the carbon and financial costs that come with such transport.  Read more and view early project photos in our Field Notes post, “Karuna House excavation: the Passive House, Minergie, LEED Platinum project is underway.”

LEED-compliant straw erosion control (l), basement excavation (c), and EPS foam delivered (r)

Geofoam Foundation Installation

Once excavation was complete, our first step was to lay the EPS (expanded polystyrene) geofoam foundation layer to insulate the concrete footings and slab from the ground.  In this video Scott talks through the steps our team took to prepare the foam layer.

These photos (below) show the pre-cut pieces of EPS being unloaded from the truck, and then placed.

Foundation Footings

The team then poured the foundation footings directly on top of the layer of geofoam.  The Field Notes post, “Karuna House’s concrete on foam: Passive House innovation and simplicity” describes the process and features site photos.  In the video below Scott points out the black capillary break material that coats the top of the footings to block moisture transfer up into the foundation stem walls.  He also shows how the team will precisely align the wall forms.

These photos (below) show the various footing treatments across the site, all prepped with the capillary break material across the top.

Basement Foundation Walls

In this next video, Scott walks us through the layers of the foundation wall, from ¾-minus compacted gravel, to 8″ EPS foam, to concrete footing, to capillary break, to 15 mil poly vapor barrier, and finally the concrete stem wall.  The blue vapor barrier material is centered on top of the footing and embedded into the wall as the stem wall is poured atop it.

These shots below show the standard concrete form construction on the left, and then the finished product on the right.  This LEED and Minergie-ECO-friendly concrete contains 30% fly ash and locally-sourced aggregate.  See the post “Karuna House concrete detailing and pour shown in site photos” for more about the concrete work.

Basement Thermal Breaks

Thermal bridges – bad.  Thermal breaks – good.  Thermal bridges are elements in a structure that allow heat to transfer between conditioned and unconditioned space, between inside and outside (roughly speaking).  Wood studs in standard wall assembly are a ubiquitous example of thermal bridging – they conduct heat at a much faster rate than the adjacent insulation layers, speeding up heat loss through the wall assembly.  The goal in Passive House design and construction is to eliminate thermal bridges and create continuous thermal breaks (ie. insulation, like our EPS).  In an ultra-low energy building, no potential thermal bridge can be ignored, especially when dealing with concrete or steel.  Neglecting to account for thermal bridges will lead to much more energy use than planned and can lead to comfort and condensation issues.

In this video, Scott describes two special thermal break details designed into the basement at Karuna: 1. around the ejector pit, and 2. through the stem wall and basement slab to separate the wine cellar from conditioned space in the basement.

This photo below shows the notched EPS thermal break in detail, before the surrounding concrete stem wall had been poured.

Foundation Wall and Drainage

Scott describes the basement wall assembly: concrete stem wall, liquid water proof barrier (black), 8″ EPS, and a layer of high density drain board tied into a drain at the toe of the footing.

These photos below show the black drain board and white drain pipe awaiting installation (on left), and the basement wall with EPS layer fully applied across the exterior (right).

Underslab Foam and Vapor Barrier

After leveling the 3/8-minus compacted gravel to a tolerance of just ¼”, the team sets the underslab EPS foam.  The vapor barrier is positioned across the top of the 12″ layer of foam.  Avoid the bathtub effect!

These photos below show the blue vapor barrier, taped and sealed.  The center and right shots show the careful treatment of pipe and rebar penetrations through the layer, with meticulous application of tape and mastic.

Based on lessons learned from the Karuna foundation, we made some refinements to approach that we applied to construction of the Pumpkin Ridge Passive House.  See “Passive House foundation design and construction optimized at Pumpkin Ridge” for details.

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In high performance green building like Passive House and Minergie-P, it’s difficult to overstate the importance of fenestration.  Partly that’s because windows and doors represent big holes poked through a meticulously engineered and constructed wall assembly, opening potential weak points in the system for the transfer of heat, air and moisture.  So you’ve got to execute high performance installation of your high performance windows in a project like Karuna (as described in the Karuna Wall Assembly page.)  No leaks allowed in the hull of this ship:

But equally important is the opportunity that high performance windows offer:

Opportunity #1: Energy Performance.

The windows at this green home building project are triple-glazed, high solar heat gain, R-8 windows made by Optiwin in Austria.  (See our own Skylar Swinford’s post about his tour of the Optiwin factory.)  These windows have a very thin frame (the weakest part, thermally-speaking, of a window) so that the whole frame can be over-insulated and fully embedded into the wall assembly.  While it’s true that even at R-8 the windows are several times less insulative than the surrounding super-insulated wall, they are net-positive in energy performance because they capture so much solar gain.  And in a very low energy load building like Karuna, energy performance gains like these can make a big difference – it’s not just a drop in the bucket.

High performance windows are not some newfangled luxury item, either.  Triple-glazed windows have been standard in Scandinavia since the 1970s, and are now code in Germany.  More and more high performance window options are becoming available in the US, a welcome development among designers and builders of high performance buildings.

The same is true of high performance doors.  The exterior doors at Karuna are also Optiwin, with the exception of the cellar door that Hammer & Hand built.  These doors look a bit like vault doors, thick with insulation, gasketed and airtight, and equipped with multipoint locking mechanisms to ensure a tight seal.  See Hammer & Hand master jointer Dan Palmer describe the construction of the Hammer & Hand Passive House door here:

Opportunity #2: Aesthetic

High quality windows open design options for the architect, allowing high performance projects to break out of the shoebox mold and become a medium for high design as ripe with possibility as anything else out there.  Holst Architecture’s design of Karuna is proof positive.

Because high performance windows can be so good at capturing solar heat gain, shading becomes important, especially in the shoulder seasons when sun angle brings lots of rays into the home but outdoor temperatures are still mild.  On modernist homes, with their clean lines free of traditional, shade-providing overhangs, the potential for overheating is more acute.  Exterior shade systems like the one at Karuna make modernism in Passive House feasible, without sacrificing comfort.

Exterior Shading System Pt 1

Exterior Shading System Pt 2

Incidentally, the same glass attributes that make a window good at capturing solar heat gain also make the windows very clear, so clear that you’d never guess that they’re triple-paned.  So you get better daylighting and better views with high performance windows, two key elements of the architectural experience.

Opportunity #3: Comfort

One of the biggest benefits of a high performance window is its warm inner surface.  A conventional window, by contrast, has a very cold interior surface in the winter, setting up an uncomfortable convection current as inside air cools and falls along the window interior, then warms and rises, only to be cooled again.  The constant draft this creates can render unlivable big areas of the house near conventional windows.

The human body is a tremendously sensitive gauge of heat and cold, so this convection can be very unpleasant.  Thermostat settings creep up – a typical house might be set as high as 74 degrees.  But in a high performance house with high performance windows like Karuna, a thermostat setting of 68 degrees can deliver comparable thermal comfort, and makes the spaces immediately adjacent to windows cozy and draft-free.

Opportunity #4: Simplified Mechanical Systems

In high performance design and construction of projects like Karuna we view windows as part of the HVAC system because they are so connected to the design of the home’s mechanicals.  Above we touched upon how the warm interior temperatures of high performance windows lead to lower thermostat settings by occupants.  This increased comfort combined with the overall increase in energy performance brought by high performance windows means that heating and cooling equipment can be significantly downsized and simplified.  Windows have no moving parts (apart from those used to open and close), so the focus on high performance windows over complex mechanical systems brings simplicity, comfort and energy performance.

Part of the HVAC strategy to reach net-zero energy use at Karuna is to use a low-temperature radiant system throughout the floors of the home, harnessing the heat transfer power of water to balance temperatures between rooms.  This strategy would be impossible with draft-inducing, energy-losing conventional windows.  High performance windows are key.

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Building – both new construction and renovation – can be a form of climate action.

Because climate change is driven primarily by the burning of fossil fuels, then “climate action” means, ultimately, keeping coal, oil, and gas in the ground. Builders, architects, and building owners can do that by reducing demand for those fossil fuels through energy efficiency, energy conservation, and a shift to renewable energy. As Carbon Tracker Initiative says, fossil fuels demand destruction equals climate security.

There are two lenses through which to view and understand “building as climate action.” Both highlight the role that high performance passive building can play as a powerful lever for climate solution making.

The first lens is focused at the scale of the project site. Can my project be “zero carbon” on a net basis? Can the building generate more energy every year through onsite renewable energy (usually solar PV) than it consumes for heating, cooling, lighting, and plug loads? Over the lifespan of the building can this net surplus offset the “embodied energy” of the construction process and materials? And is the building part of an urban fabric that is walkable, transit-oriented, and bike friendly so that occupants aren’t forced to drive everywhere? If not, is there enough surplus onsite renewable energy generation at my site to power an electric vehicle and still stay “net positive energy” for the year?

Madrona Passive House, shown here during last weekend’s NW Green Home Tour, projected to be certified as a Net Zero Energy Building by the International Living Future Institute. The home’s 9.8 kW solar array generated more energy in April than the home consumed, including the charging of the family’s Nissan Leaf.

This site scale understanding of “building as climate action” has a powerful internal “do no harm” logic to it, hence the growth in net zero energy building certifications from the likes of the International Living Future Institute, Built Green, Earth Advantage, and others. By creating a net zero or net positive energy building you are claiming responsibility for the variables on your site that you can control – building energy performance and onsite renewable energy generation – and maximizing them. The formula is straightforward; start with Passive House to minimize building energy demand and then add a reasonably-sized PV array to generate the onsite energy necessary to reach net positive energy. Given current governmental incentives (plus falling solar PV prices), that PV array can also be a really smart investment, paying for itself in a matter of a few years.

The second lens through which to understand “building as climate action” is at a much larger scale: regional, continental, and even global. It starts with the larger view of global greenhouse gas emissions and what factors contribute to their rise or decline.

One or more of the four factors shown on the left of the formula above (called the “Kaya Identity” for the economist Yoichi Kaya who developed it) needs to hit zero if we are to realize zero emissions in the future. We know that population will likely increase to 9 billion in the next few decades. We hope, if we care about economic justice, that GDP per capita will increase around the world as more and more people rise out of poverty. So those first two circles will grow. That puts more pressure on the energy intensity and carbon intensity circles to shrink. By pursuing the revolutionary energy efficiency gains of Passive House, our buildings can play an important role in driving down the energy intensity of the built environment. So our buildings can help shrink that third circle. And if we install onsite renewable energy, regardless of whether it means the building reaches net zero or net positive energy at the site scale, we are helping to make the overall energy mix less carbon intensive, shrinking that fourth circle. Of course, we could decide to use the money that we would otherwise spend on onsite renewables and invest it instead in grid-scale solar or wind power somewhere else in the world that is really sunny or windy. That would shrink that carbon intensity circle even more. The point is that humanity needs to push as hard as possible on reducing both the energy intensity and carbon intensity of the global economy, and both passive building and net positive energy building are powerful tools to do just that.

Furthermore, Passive House and Net Zero Energy buildings lay the foundation for a future green energy grid, because their energy efficiency not only reduces overall demand on the grid but also flattens the peaks and valleys of that demand.

As our colleague Graham Irwin points out, über-efficient buildings function as thermal batteries, storing heat (or cool) energy and metering it out over the course of the day with little need for additional inputs of active heating or cooling. This means that at times of the day when heating or cooling energy use from conventional buildings spikes (like in early evening when people get home from work and turn on the heat or the AC), Passive House building energy use remains flat. The flattening effect that this and other energy efficiency measures has on the peaks and valleys of grid demand makes it easier to fill in the gaps with a mix of renewables, demand response, and storage.

Building as climate action.

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What is High Performance Building?

Airtight construction controls the transfer of heat and moisture into and through the building envelope. Thermal bridge-free assemblies avoid the envelope penetrations that sap buildings of energy, comfort, and durability. Continuous insulation keeps heat where it’s wanted. Excellent windows and doors limit heat loss while capturing daylight and passive solar energy. Shading elements shield the building from passive solar gains when unwanted. And a constant supply of filtered fresh air comes in through a balanced heat recovery (or energy recovery) ventilation system that recaptures the thermal energy of exhaust air and keeps it inside the building.

By investing in an advanced building envelope we can dramatically reduce the energy demand to heat and cool high performance building. In fact, Passive House buildings routinely reduce heating energy by 90%.

Small heat pumps can then meet this small heating and cooling demand super-efficiently. Even after adding in lighting and plug loads, building energy use is so low that a relatively modest solar array can bring high performance passive buildings to net zero energy performance.

From a builder’s perspective, the beauty of high performance building is that it’s not just about making our carbon footprint smaller, it’s just the right way to build. The same suite of strategies and components that delivers über-efficiency also makes for buildings that are more durable, comfortable, and healthy. The diagrams below show US Department of Energy’s assessment of how Passive House buildings perform compared to ENERGY STAR and conventional buildings, based on four key features: comfort, health, durability, and efficiency. The high performance Passive House buildings significantly outperform the others on all four measures.

High performance building requires a holistic approach, with high performance building strategies and components integrated with one another in a web.

This web reflects the fact that buildings behave as systems, much like ecosystems. Changes to one part of the system can have big impacts elsewhere. There’s a critical difference between ecology and building science, however. Ecosystems are wildly complex. Buildings? Not so wildly, so they are knowable and manipulable given the right building science knowledge. High performance buildings, and the multi-layered benefits they bring, are the manifestation of our systems-based understanding of building physics.

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1. Customizable Everything
When you build a home, you have complete creative control over the design and layout through partnering with an architect to create a floor plan that suits your needs and lifestyle perfectly. From the number of bathrooms and bedrooms to the size of the kitchen, everything can be tailored to your preferences. You select the style and color of appliances, door knobs, faucets, and fixtures.
This level of customization isn’t possible when you purchase an older home where you may be limited by the existing layout and features. When you build a new home, you can work with your architect to create a space that is uniquely yours.
Customization also allows you to incorporate features that are important to you and your family. For example, you can select an open floor plan for your home that promotes family togetherness. Or, you can create a space to be used as a private home office or personal home gym. By customizing your new home, it will reflect your style and personality.

2. Energy Efficiency
New homes are typically built with energy-efficient features like better quality insulation, high-efficiency HVAC systems, and energy-saving appliances. This means you’ll save money on energy bills and reduce your carbon footprint.
You also have the opportunity to employ some passive home technique, or explore the possibility of reaching net-zero energy consumption. You can read more about what these are and what Passive House and Net Zero are here.

3. Lower Maintenance Costs
When you build a new home, you won’t have to worry about costly repairs and maintenance issues that often come with older homes. New appliances, plumbing, and electrical systems mean that you’ll have fewer surprise problems to deal with. Low maintenance elements can be built into the design, such as aluminum-clad windows that don’t require repainting, long lasting metal roofing with a lifespan of over 50 years.

4. Technology
New homes often come equipped with the latest technology, such as smart home systems and built-in entertainment systems. You can also easily integrate other technology into your new home, such as solar panels or electric car charging stations.
These technology features can not only make your life easier and more enjoyable but, like energy-efficient appliances and materials, can increase the value of your home because buyers desire the latest technology.

5. Financial Benefits
Building a home can also offer financial benefits. You may be eligible for tax breaks and incentives for building an energy-efficient home. Check out the Energy Trust of Oregon for specific incentives. Building a home can also be a wise long-term investment. As the housing market continues to grow, your new home could appreciate over time, giving you a significant return on your investment.

7. Improved Health and Well-being
New homes are often built with health and well-being in mind. Many new homes have features such as better indoor air quality, non-toxic building materials, and outdoor living spaces that encourage exercise and time spent in nature. These features can improve your overall health and well-being, which bodes well for your quality of life. Spending time in a healthy environment reduces stress levels, increases productivity, and promotes better sleep.
Furthermore, building a new home allows you to incorporate features that support your specific health needs. For example, if you have allergies, you can install an air filtration system to remove allergens from the air. Or, if you have mobility issues, you can design your home with wider doorways and accessible bathrooms to accommodate your needs. You can learn more about green home building techniques and the impact of them here.

Hammer and Hand understands that building a new home can be a long and daunting process, which is why our team works closely with every client and their architect every step of the way. You can read more about our Partnering with Architects process here.  From the initial home-building consultation to the final walkthrough, Hammer and Hand will answer your questions and ensure your vision is brought to life.

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Blending contemporary elements with the natural beauty of the region, Northwest Modern homes exude a sense of timeless charm and harmonious integration with the environment. Clean lines, ample use of natural materials, and large windows are signature elements that define this style. The simplicity and functionality of the design are aimed at creating a seamless connection between indoor and outdoor spaces. Expansive windows allow abundant natural light to flood the interiors while providing breathtaking views of the surrounding greenery, mountains, or water bodies. From cozy retreats nestled in the forest to striking waterfront properties, Northwest Modern homes effortlessly blend with their surroundings, celebrating the beauty of nature.

The interior spaces of Northwest Modern homes are characterized by open floor plans, minimalist aesthetics, and a focus on sustainable and eco-friendly materials. Warm wood tones, exposed beams, and natural stone accents add organic textures, creating a welcoming and cozy atmosphere. Thoughtful integration of energy-efficient technologies and sustainable design principles ensures that Northwest Modern homes not only offer visual appeal but also prioritize environmental responsibility. With their timeless charm and seamless integration with the Pacific Northwest’s natural splendor, Northwest Modern homes continue to captivate homeowners seeking a harmonious balance between contemporary living and the surrounding environment.

As traditional builders, we do not have designers in-house. Instead, we work with clients and some of the best architects in Portland and Seattle to achieve our clients’ goals. If you are considering building a home in the Northwest Modern style (or any style), Hammer & Hand can help pair you with the perfect design team to suit your needs! Contact us today and tell us a little about your project to get started!

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PUMPKIN RIDGE

“Let’s do all cellulose,” is the story of the Pumpkin Ridge Passive House wall assembly. The design of the house became an expression of the home’s performance imperatives, so the display of thick walls, filled with several tons of high density cellulose insulation (and sequestered carbon), was seen by the team as a desirable design feature. The home’s energy performance is climate friendly, but so is its construction and low embodied energy.

The air barrier for Pumpkin Ridge Passive House is a layer of OSB with fluid applied at seams. While the OSB is vapor permeable (and gets more so when wet), it does retard vapor transfer.

The wall’s R-60 insulative value (center of cavity, including impact of sheet goods and air films) is provided by two thick layers of high density cellulose insulation, 9.5” in a Larsen truss system to the exterior and 5.5” in the interior 2×6 stud wall.

The home’s vertical cedar siding provides the first line of defense for bulk water management with a rain screen cavity facilitating drainage. The second (and final) barrier is the layer of tongue and groove Agepan (wax impregnated wood fiber) panels, tightly fit so that wind cannot blow bulk water through.

As mentioned earlier, the OSB is vapor permeable but it does retard vapor transfer. This throttles down the flow of vapor from the home’s interior into the assembly. The rest of the assembly, from cellulose insulation to Agepan layer, is very vapor open, so the airflow created across the assembly’s face by the ventilated rain screen cavity promotes the drying of both the assembly and the cladding.

See an annotated photo tour of the assembly’s layers:

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