Measuring Net-Zero Performance and Success

As we discussed in the previous post in our Net Zero series, pursuing a net-zero standard is an investment. So, how do you know if that investment is paying off? Here, we look at methods and tools for measuring net-zero performance and success.

Consumption vs Generation

Enphase photovoltaic interface shows generation on a daily, monthly and annual basis.

The Enphase App

First and foremost, tallying up the monthly energy bills at the end of the year provides a clear picture of a home’s net-zero performance. The total cost should, obviously, be close to zero. In the case of NetZeroRowhouse, we consumed a total of 10.6 kWh in 2022, and we are on track to match that in 2023. During the summer months, we fed more energy back into the grid, whereas during the winter, we drew from our local utility provider.

Speaking of solar, we generated 9.4 kWh from the rooftop array in 2022, indicating that we only drew approximately 1.2 kWh from our electrical grid. From an energy perspective, we were close but not quite at net zero.  Most photovoltaic systems feature a web-enabled interface, offering a remarkable level of detail and scale. From an energy perspective, we were close but not quite at net zero.  The actual production of the array, as calculated from City Renewables, predicted 10 kWh.  Given the variability of weather, our generation was just 96% of what was anticipated, so very close to the predicted total.

Where did the energy go?

A snapshot of the Leviton app shows consumption on a per circuit basis.

Leviton App reads consumption on a per circuit basis.

Since all of our energy usage is electric, we can track consumption to measure  net-zero performance.  To provide additional detail, we utilize the Leviton Smart Panel, and can delve deeply into understanding where that electricity is being used. For instance, the three-zone Mitsubishi Ducted Heat Pump consumed about 277 kWh in January 2023.

Our next significant load is hot water generation. In some months, we use more energy to both generate electricity and keep the mechanical room warm enough. For example, in March 2023, we spent 234 kWh on the heat pump water heater and 351 kWh on the space heater, totaling 585 kWh—more than twice what we spent on heating (216 kWh). This energy vampire is, in fact, a design issue for the water heater installation. Moving into 2024, we have started venting the heat pump water heater directly to the exterior to reduce the heating load in the mechanical closet.

Examining energy usage associated with food storage and preparation is also key.  In a typical month, the Bosch induction cooktop usage ranges from 9 to 15 kWh, the oven between 37 kWh and 64 kWh, and refrigeration is another 43 kWh to 56 kWh. In retrospect, having the refrigerator, beverage refrigerator, and coffee machine all on one circuit provides insight on life’s essentials!

The zero tool is used to determine the baseline and target EUI goals

Zero tool is one of the tools to measure net-zero performance

We support this claim by examining a couple of metrics. The Home Energy Rating System (HERS) is the industry standard for measuring energy efficiency. A home receives a relative performance score compared to a reference house. The lower the number, the more energy-efficient the home. The projected HERS score for the project is -5; this will be confirmed in 2024.

Another helpful metric is the Energy Use Intensity (EUI), which is the industry’s equivalent to a miles-per-gallon rating. It is calculated by dividing the total energy a home (or any building) consumes in one year by its square footage. A low EUI value signifies good energy performance. Using ZeroTool, we can see that the target EUI for a similar-sized rowhouse in Washington, DC, is about 30. To meet a net-zero standard, that number should be below 10. The EUI for 2022 came in at 1.9 last year!  By all accounts, the home is a net-zero success. In the first year, the solar array offset an impressive 88.6 percent of the energy consumed.

Value of Solar Renewable Energy Tax Credits

There are other ways to offset those initial costs. Maryland, Virginia, and Washington, DC, all offer solar energy incentives. Homes outfitted with panels can generate Solar Renewable Energy Credits (SRECs), which have a monetary value and can be sold or traded to generate revenue for the owner. The Capitol Hill rowhouse generates about 8 to 10 SRECs per year, each valued between $300 to $400. In 2022, the family received $2,877 in revenue from the energy credits and only spent $702 on electricity, netting over $2,100.  From a cost perspective, we are actually Net Positive!

Net Zero is the Way Forward

Sustainably built homes can play an integral part in the climate change solution. Net zero is the way of the future, but it’s never too early to start—or too late to change. The available technology and options have reached the point where net zero is an attainable goal, and one we hope more clients will pursue with the help of Teass Warren Architects. While, measuring net-zero performance and success is critical, we also want to create thoughtful and well-designed homes that are a joy to live in!

Two Case Studies for Office to Residential Conversions

There’s a lot of buzz about Office to Residential (“O2R” if you’re in the know) conversions, particularly in downtown areas where there are high office vacancy rates.  Converting the typical downtown DC concrete office building is problematic for a whole host of reasons we’ll cover depth in a future journal entry.  However, we recently designed two O2R conversions where the stars aligned and the project made both financial and practical sense to undertake.  While both projects had unique challenges, we were able to overcome them and deliver new residential units in areas desperately in need of housing.

The first project located the Tenleytown / Friendship Heights neighborhood was a boutique scaled mixed-use building containing office over ground floor retail.  Close to American University, this project targeted students as rental housing with small apartments.

4709 Wisconsin Office to Residential Conversion

4709 Wisconsin Office to Residential Conversion

The second project, located in Shaw, is a condominium conversion of office and headquarters of a non-profit organization that had adaptively reused a historic schoolhouse.

Why These Worked

Sometimes older is better!  In the case of 4709 Wisconsin, the original building was constructed in 1937.  For the Schoolhouse of The Collection at R, the structure was originally constructed in 1883.  It was converted to office use in 1985. These buildings predated the reliance on artificial ventilation systems, air conditioning, and artificial lighting.  This is important because they both were configured with relatively narrow floor plates and had exterior exposures that provided direct ample access to natural light and ventilation.  This remains critical even today to meet building code requirements regarding the interior environment.  While there are some exceptions in the code which allows for internal bedrooms, we generally encourage natural systems and access to daylight as it promotes the health and well-being of residents.  Exterior perimeter walls also allow for simpler routing of ventilation, outside air intake, and shorter exhaust duct pathways.  This article from the Washington Post covers a lot of the issues with many O2R projects.

Despite having an odd trapezoidal lot shape, the original office layout of 4709 Wisconsin combined with a large courtyard located on the northwest corner, and the narrow footprint worked well for small studio apartments and compact two-bedroom units.  This mix was ideal for the target market of college students either living alone or with a roommate.

murphy bed built-in

murphy bed built-in

4709 Wisconsin Office to Residential Conversion

4709 Wisconsin Office to Residential Conversion

In the case of The Schoolhouse, the original building was originally configured as an eight-classroom building.  This layout worked well for four apartment units per floor that are located off a central circulation spine.

440 R Office to Residential Conversion of a historic school building

440 R Office to Residential Conversion of a historic school building

The units here are generous and are meant to appeal to a clientele looking for family-sized units as an alternative to a traditional rowhouse dwelling which is more typical of this neighborhood.

School building Unit Stacking Diagram

School building Unit Stacking Diagram

These two buildings also predate the dominant use of concrete or steel frame construction and are primarily constructed out of wood with masonry bearing walls.  This allows for easier alterations and reconfiguration.  Even if structural steel components are required to pick up new loads, it’s a lot easier than demolishing rebar, concrete slabs, drop panels or cutting out steel beams and columns.  From a carbon sequestration standpoint, they also have a lighter impact on the environment.  Adaptive reuse of existing structures is a better environmental option when it can be accommodated.

The Hard Part!

While both projects were recently completed, we would be remiss to not expand on some of the challenges we had to overcome along the journey.

On the 4709 Wisconsin Avenue project, the ceiling heights at a little above eight feet, are lower than we would design with a new market-rate building.  But the costs to increase the finished clearance would have been prohibitive.  Additionally, construction over an existing retail space required the demolition of ceilings and extensive rework to install new systems and plumbing hookups.

The change of use also triggered a requirement to fully sprinkler the building, including the existing retail spaces.  This resulted in an upgrade of the fire water service for the building, which was an expensive undertaking that put additional financial pressure on the project.

On the 4709 Wisconsin Avenue project, the ceiling heights at a little above eight feet, are lower than we would design with a new market-rate building.  But the costs to increase the finished clearance would have been prohibitive.  Additionally, construction over an existing retail space required the demolition of ceilings and extensive rework to install new systems and plumbing hookups.

In addition, the DC Zoning Regulations also mandate a bicycle storage room for any building with eight or more units.  On a building of this scale and configuration there is little practical area to provide space for bikes.  Therefore, the bike storage room had to be in the middle of the first residential floor of the building, which was not ideal.

Existing Roof Truss During Construction

Existing Roof Truss During Construction

The Schoolhouse at the Collection at R Street provided numerous challenges as well.  Structurally, the original masonry bearing walls of the building were in a pinwheel configuration.  These bearing walls conflicted with ideal unit layouts and ultimately needed to be removed.  However, these walls supported girder trusses that acted as supports for the roof and attic floors as well as braced the exterior masonry walls.  With the demolition of the bearing walls, these trusses needed to be supported with new posts.  Extensive temporary shoring was required to keep the roof intact and the site safe during construction.  We incorporated remnants of the truss to celebrate and tell the story of the original building.

The attic story was converted to bedroom use but needed egress windows. In addition, we sought exterior spaces for the top units.  Given the historic landmark status of the building new dormers were not an option, so we created outdoor spaces by carving into the roof with a “reverse dormer”.  This arrangement provided exterior access and the carved-out spaces were not visible from the street due to the angle of the line of sight and the parapet.  These unique outdoor spaces permitted emergency egress and rescue openings from the bedrooms as well as needed outdoor spaces for the units.

Outdoor terraces carved into roof - office to residential conversion

Outdoor terraces carved into roof – office to residential conversion

Competition for outdoor area at grade was complicated.  Due to zoning regulations, one parking space is required for two dwelling units was required.  This was quite constraining, particularly given the proximity of public transportation.  The outdoor mechanical units also needed to be located at grade because the historic roof structure was not able to accommodate the units.  Trash storage also compressed opportunities for exterior space at grade, but we did provide occupiable outdoor areaways for three of the four cellar level units.

One additional challenge was the limitation on the number of units.  In the case of the school building there is a zoning constraint that requires 900 square feet of lot area per dwelling unit, meaning that we were limited to a maximum of 12 units.  Given the large amount of buildable area provided within the building, this requirement feels arbitrary.  Likely, the structure could have accommodated another 8-10 units.  Given the proximity to many neighborhood amenities and robust infrastructure, the limit of units is an unnecessary constraint to the production of sorely needed housing units and forced the owner to build larger units that are priced on the higher end of what the market can absorb.

Conclusions

Office to residential (O2R) conversions can be great projects for adaptive reuse and the introduction of missing middle housing, but it depends on many factors.  These particular buildings had good bones, strong financials, and neighborhood amenities to make it work.  But even in the best of circumstances, O2R’s can be tough to navigate.  It takes the expertise of a talented design team, a great general contractor partner, and a courageous owner to make these projects a success.

How Universal Design Supports Sustainability and Inclusiveness

Incorporating the principles of universal design as you build or renovate a home leads to a better quality of life now and also provides insurance against any future mobility issues you or other family members may face. But the benefits of universal design extend beyond your household by supporting sustainability and inclusiveness.  The environment and your larger community reap the rewards too.

Parallel Goals: Sustainability and Universal Design

If you’re seeking a sustainable home, then you’re probably considering solar panels, energy-efficient insulation and eco-friendly materials, maybe even Net Zero Construction among other strategies (find our guide here). Here’s an important one to add to the short list: universal design.

wide circulation pathways are elements of universal design

wide circulation pathway diagram

Read More

Cost of Building a Net-Zero Home

There’s no denying that there is an increased cost of building a Net-Zero home. At Teass Warren Architects, we believe the payback more than justifies the initial investment. This is the third post in our Net-Zero series, addressing the question of costs.  The final post will focus on how to recoup the costs, as well as measuring the performance of the house and systems.

HERS Index of Individual High Performance Elements

HERS Index of Individual High Performance Elements

During the design phase, we worked with a high performance building consultant to determine which strategies would not only be most effective, but also most cost effective.  Options were evaluated by impact on the Home Energy Rating Score (HERS) Index as well as payback costs.  The options were the bundled to assist in the decision making process.  While some of the costs associated with upgrades was accurate (for example the solar panel), other cost estimates were significantly different due to to building during the COVID pandemic and general construction inflation. Read More

Universal Design for Aging-in-Place, Before the Need Arises

It’s an undeniable fact of life: We’re all getting older. So planning ahead for the inevitable is wise during any new construction or renovation. And it won’t break the bank, either. Admittedly, discussing issues of age and accessibility isn’t always comfortable. Yet, frank conversations early in the design process are key. Incorporating Universal Design for aging-in-place and anticipatory components will ensure that your home supports you and your loved ones, whatever the future may bring.

Aging in Place Doesn’t Equate to Geriatric

If the term “aging-in-place” conjures images of unsightly, institutional spaces, think again. Many universal design strategies can be embedded in new-build or renovation plans, without compromising the design (or impacting the budget). In fact, as you’ll see below, some have become hallmarks of modern, high-end design.  Read More

Designing For Net Zero

In Part 1 of our Net Zero series, we defined “net zero” and delineated the advantages of taking the sustainable approach. This second post looks at Designing for Net Zero, using the thoughtful renovation of firm co-founder’s own Capitol Hill rowhouse as a case study. In designing or retrofitting a net-zero home, the goals are to maximize energy production and minimize energy consumption (check out our guide here: Your Very Good Home).  We worked closely with a Jay Hall and Associates to perform an energy model to develop a solution for each side of the equation.  The first steps are to estimate the home’s energy consumption and evaluate sustainable strategies for matching it.  A cost-benefit analysis helps us identify the optimal set of improvements that minimize costs and maximize pay-back, while still getting us to the goal line.  The ideal bundle looks a little different for each project.

Designing for net zero utilizing Energy model analyses

Energy model analysis

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