View of the newly installed solar panels.

We worked with the team at Solar Solution for the design and installation of the rooftop solar photovoltaic system through the DC Solar Solution Program. The staff at Solar solution was able to provide an assessment of the available roof area and determine the optimal layout to maximize the configuration to achieve the maximum number of panels and the optimized power output of the system. Even on our very small roof they were able to install (14) 340 Watt panels, resulting in a 4.76 KW system.

They also handle all of the tax credits and the SRECs (Solar Renewable Energy Credits). Under the program we got an upfront SREC credit that covered 70% of the system cost. We had to pay for the remaining 30% of the system cost, BUT that will be refunded to us with our 2019 Federal Income tax returns as a Federal Income Tax credit. Meaning the final cost to us for the system will be zero dollars – that’s right, free.

The installation required no penetrations of the roof membrane since the solar panels are installed onto a racking system that is simply ballasted to the roof and is designed not to damage the roof membrane.

After the installation of the panels Solar Solution’s electrician installed the control box on the exterior wall (directly below the panels) that was then connected to the main electrical panel for the house. The final step will be for Pepco to install the new Net Energy Meter that will allow for tracking of both energy used and energy produced by the house. We will be able to monitor the energy production compared to the energy used in real time via an app on our phones. We are very excited to be able to start monitoring the output of the energy panels to see how much of the energy use of the house can be offset by the on-site solar production.

Current building science research has discovered that the air tightness of the building envelope is very important to a building’s energy performance, thermal and moisture control, and indoor comfort. But most conventionally built buildings are sorely lacking in terms of air tightness, and this is particularly true for old brick buildings. Brick construction is not an inherently air-tight assembly, and in traditional masonry construction the wall assembly consisted of several whythes of bricks joined together with mortar. On this house the front wall was built with a better quality fine brick with tight thin mortar joints, while the side and rear walls were built from common brick with larger looser mortar joints. This was common practice for the side and rear walls of the rowhouse construction where the mortar often has gaps between the bricks.

We hired Mid Atlantic AeroBarrier to perform the air sealing of the building. The process they use involved pressurizing the house and the emitting a vaporized sealant into the space. The sealant product the use is GreenGuard certified for low chemical emissions. The high pressure in the house causes the sealant to collect at the small cracks and seams as the air is escaping. As the sealant collects at the cracks they are gradually sealed and the building becomes tighter. The guys at Mid Atlantic AeroBarrier ran the process for about 2 ½ hours. When they started the pressurized house registered an air leakage rate of 11.41 air changes per hour (ACH). After 2 ½ hours their process had reduced the air leakage rate to 1.68 air changes per hour (ACH) – resulting in an 85.3% reduction in the air leakage of the building envelope! We could see visible areas where joints and cracks had filled with the escaping sealant. This is a simple yet ingenious process that seals the entire envelope including tiny joints that would not otherwise be able to be accessed.

After the air sealing was complete, we were able to turn our attention to insulation. Since we have no attic we needed to achieve the maximum insulation values in the roof framing cavities as possible. We decided to go with closed cell spray foam as the first layer. 3” of foam was installed on the underside of the roof sheathing and 1” of foam was installed along the inside of the exterior walls. The remainder of the roof and wall framing cavities were filled with batt insulation. This gave us an R-51 at the roof and an R-20 in the exterior walls. This strategy of installing spray foam on the interior of the sheathing and then filling the remainder of the framing cavity with batt insulation is commonly referred to as “flash & batt” and draws on the inherent air sealing capacity of the spray foam as it expands and fills voids and cracks. The batt insulation is flexible and installs quickly to fill the balance of the framing cavities. With these air sealing and the insulation measures complete we are looking forward to improved energy efficiency, enhanced indoor noise control and thermal comfort. We think that it will all be well worth it when those bitter cold winter nights arrive.

Studio Upwall Architects

DC Rowhouse Renovation - Energy Saving Measures – Solar Panels: / November 20, 2019 by Gregory Upwall

DC Rowhouse Renovation - Energy Saving Measures - Air Sealing & Insulation: / October 14, 2019 by Gregory Upwall

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