With rapid infill happening in the neighborhood, Jingzi and Chris questioned what to do with the small house that remained on the original lot. Though it was easy to find renters for the house, it needed extensive repair and lacked seismic safety features. Jingzi wanted to keep the property and preserve the views and light for their new home’s outdoor spaces. Knowing that change was inevitable, she decided to develop the property her way instead of turning to a developer.
Today, where a tiny 800 SF home once sat, a new duplex nestles under the shade of a massive Norway maple tree. With an ADU below the house, and the two new units, a total of 4 dwelling units now occupy this former single-family 4,370 SF lot.
The following interview is the story of this sustainable infill duplex, bringing Waterleaf one step closer to our 2030 Challenge goal to take care of our health and the health of our planet. While Zero Energy Ready (ZER) certification through Earth Advantage was pursued, it was not ultimately achieved due to the nearby tree canopy limiting solar access. However, zero energy ready design principles were used as a guide, and each of the two units of the duplex is Earth Advantage Platinum Certified. The process to achieve that certification required early steps in the design for significant energy savings, resulting in a balanced, sustainable design that allowed the client to respond to neighborhood concerns and create the right development for the site.
Waterleaf posed questions to the project team, asking about their journey to develop the most sustainable design possible with the owners, the city, and the neighborhood. The architect, Waterleaf’s own Emily Réfi; and contractors, Tim Furlow and Carson Benner from Cellar Ridge Construction, discuss the successes and constraints of their energy goals for the project [comments were edited for clarity/space].
WATERLEAF: Why choose the path to zero energy? What drove design decisions during the schematic design phase?
CARSON: We were in a position to know that solar panels were not in budget – while not achieved, an advantage of pursuing Zero Energy Ready projects is that you can start the process without the panels. This is easier for the client to buy into. Go after low-hanging fruit in the beginning on top of efficient heating systems.
EMILY: With a small lot home, the biggest move that you can make is building a right-sized building – essentially not creating any more square footage than needed. The client wanted something aesthetically pleasing to look at from next door. She wanted to build something high quality and that made financial sense, all while being a good neighbor by building small and saving the existing tree. The majority of impactful work is in the scoping in the beginning of the project and pushing for a double wall system as the standard for how the house is put together. Having a double wall system as part of the structure is important – it cannot be value engineered out.
W: How significant were the savings from the double wall?
C: A double wall system doubles the insulation value of the house which reduces the heat load significantly. It is a fraction of the cost of a solar array. Then, an air seal on top of that with a fresh air mechanical system adds up to better insulation. A double wall also adds sound resistance.
E: It creates a very effective thermal break by separating a structural wall from an interior wall. The home has triple glazed windows which also help to reduce sound too.
W: The double wall system shrinks interior space available. Was there any concern?
Carson: Incorporating the double wall system needs to be integrated early on because it can have a negative effect on the design and it can be tricky to integrate later on.
E: There was concern about losing square footage on the interior. Looking back to Chris and Jingzi’s house that was completed in 2015, we designed it with 2x6 walls and exterior insulation, but the exterior insulation was value-engineered out to cut cost as the project progressed. It’s easy to get rid of that insulation if you have 2x6 walls and still get your building permit, making it likely to get cut out of the scope. Also, once a 2x6 wall is constructed with exterior insulation, it’s only about an inch or two wider than the double stud wall so there is not a significant amount of space saved.
W: Zero Energy Ready certification was not ultimately achieved, but some zero energy design principles were used to strive for some energy savings. Are sustainable design principles expressed aesthetically in the house? If so, is this to bring awareness to the importance of pursuing more sustainable design, or for a different reason?
E: The thickness of the walls shows through and within the design of the upper level. Some walls were architecturally thickened even more with very thick or angled reveals. The existing Norway maple tree was celebrated through the alignment of the windows – clerestory windows were set to provide light where it is high, bringing in more daylight while maintaining privacy in the urban context.
W: Did you find that exterior improvements are better or easier to present to clients than solar arrays?
C: Most clients find that reducing the carbon footprint plays into creating more efficient designs, which reduces the size of solar arrays.
E: It’s always best to prioritize reducing energy loads as much as possible, which the double wall effectively accomplishes.
C: For interior air quality, we worked hard at air sealing and then used mechanical ventilation to bring fresh air into the home. It was relatively straightforward on a small home and has smaller design effects. We used an ERV (energy recovery ventilation) system that includes a robust fan to bring fresh air into the home, runs it through a manifold, and then is heated or cooled before it reaches the occupants.
W: What has the reaction been from the surrounding neighborhood? Deconstruction and infill are controversial in established neighborhoods. What was the community’s reaction?
E: When we applied for demolition of the existing small Victorian house, we had to notify the neighbors. When the notice came out, the neighborhood committee contacted Waterleaf and asked us to explain our plans. There were concerns about other infill development currently going in, such as the four-plex under construction on a nearby lot. We put together graphics to communicate to the neighborhood the plans for the deconstruction process, the neighborhood scale and context of the design, and the preservation of the mature Norway maple tree. This outreach effort was successful and we received two letters of support from a neighbor and the neighborhood committee, which helped with the land use review process. This relates back to getting the right amount of scope and size early on.
Tim: I was involved in the deconstruction – people walking by would ask a question about demolishing the house, and we found some resistance to new construction. We showed people the process of salvaging/deconstructing the house, with two dumpsters – one for salvaged wood – and people were more accepting of history being preserved rather than going to the dump. The deconstruction was all done by hand, not wrecking equipment, so more product was saved than destroyed. People were very impressed with the design and how it fit into the neighborhood and opened up the corner. The neighborhood felt revitalized and the new house was complimentary to the neighborhood. People were asking for our cards, stopping on the corner and thinking it looked amazing.
W: What happened to the salvaged materials?
C: We worked with Lovett Deconstruction and they managed what happened to the salvaged materials. There was a 30-yard dumpster full of reclaimed wood. We did take the old house tile address label, frame it, and give it to the client as a gift though.
W: Tell us about challenges you faced on this project. How did the project team come together to overcome these challenges?
C: Working in the Portland jurisdiction was challenging - a third of management hours were spent on managing the inspection process, with different inspectors every time and delays because of unknown inspections. Inspectors weren’t finding things wrong but the process delayed construction. The erosion control process was recently updated, which also caused problems for us.
E: The biggest challenge was the Norway maple tree. Though we were not required to save it, the owners decided to keep it to maintain the shade canopy – taking that away would change everything around it. Getting through the permitting process as a voluntary save was challenging. Additionally, during construction, we discovered the topographic survey was incorrect – the terrain around the tree was actually 2’ higher than was documented – this changed how the entry path, stair, and porches met the ground and how the building interacted with the tree. We had to change the location of some of the footings to accommodate. The arborist came out and hand excavated for the porch footings so they would miss the roots.
T: The tree posed many challenges – we had to get the arborist to cut branches to allow for building under the tree. It was a tricky challenge for everything we did.
E: The tree created too much shade for a solar PV system to be feasible – which is why we could not pursue Earth Advantage’s Zero Energy Ready certification.
W: Will there be a post-occupancy evaluation to verify if the house is performing as expected?
C: Earth Advantage produced an energy model. The situation is unique because the client does not live in the home. Since it is rented out, there are no plans to conduct a post-occupancy evaluation.
E: It is hard to do a post move-in evaluation with renters. The owner is likely more motivated to take advantage of new systems than a renter might be – behavior makes a big difference in performance.
W: Are there any lessons learned for similar projects in the future?
C: For lessons learned, a fire wall separating the two units because of the lot size and how it was assembled could have been more efficient.
E: The amount of effort and cost associated with keeping the tree should be kept in mind for future projects – that said we wouldn’t have arrived at a different conclusion. It was little unusual to have large west-facing windows – so some features aren’t strictly about energy efficiency, they are about connecting to the neighborhood. The shade from the tree is helping to reduce heat gain of the large west-facing windows. However, one of the biggest lessons learned is that the tree created too much shade to allow for a solar PV system, so we ultimately could not pursue Earth Advantage’s Zero Energy Ready certification.
Also, make friends with the neighborhood. If they invite you to speak about demolishing the house, you have an opportunity to get them on your side and reassure them about what is going to be going up in its place. Listening and letting them know that you understand their concerns and establishes trust with the neighbors.
Metrics to Know
|Annual Energy Use||Actual (kWh): N/A|
|Simulated/Designed (kwh): 6,674|
|Energy Use Intensity (kbtu/sf): 20|
|Annual Energy Generation||Energy Generated (kWh): 0|
|Simulated/Designed (kwh): 0|
|Systems||Passive systems used: Double wall with continuous insulation; air sealing; use of existing site resources by keeping the large Norwegian Maple to provide summer shade; building orientation|
|Active systems used: heat pump, ERV|
|Renewables: None; buildings are solar ready|
|Square Footage||2200 GSF total both units, (1100 each)|