Love | Schack’s architect Andrea Michael turned her professional energies to a personal project: 3-year phased retrofit of her family’s home to be Net Zero. She chose local renewable energy to run her home and sourced nearby and natural renovation materials to reset the energy demands.
This mid-century ranch style home was not a top performer. In fact, it sat down near the bottom of poor performance—2 x 4 exterior walls, R-11 fiberglass batts, minimal insulation in the attic, single pane windows with interior storms (that were painted in place!). Now, over two years and three major phases, the house is ready to be Net Zero (or near that). Andrea, an expert in renovations, interiors, and high-performance, was able to use most of the tools and metrics she specifies when she designs homes for Love | Schack clients. Air sealing, ventilation, insulation and mechanical systems were all upgraded.
Phase 1 - The attic
Starting at the top, the first phase included improvements to the attic. A new roof and ridge vent, baffles in the rafter bays and blown in insulation tightened the thermal retention. But after a winter with significant ice dams, they realized the cold roof design was still not functioning. The culprit was that once air came in through the soffits it had no way to escape. The fix was pulling off the vent cap, cutting through the sheathing and replacing the cap. No more ice dams.
Phase 2 -The house overhaul
The thermal envelope of the walls came next. Two layers of siding, all of the windows and the exterior doors came off, baring the home to a clean surface. After repairing some rotten sheathing, the house was wrapped in Solitex Mento 1000. With all of the seams fully taped and the bottom edge brought below the rim joist and adhered to the concrete foundation with sealant, this WRB (weather resistant barrier) product doubled as an air barrier. New flange style windows were set into the existing rough openings and new egress windows were added to the basement bedrooms. 3” mineral wool was tacked to the sheathing and run below the rim joist (this junction in older houses is notorious for lots of thermal loss) and furring strips above that formed a rain screen and a surface to attach the new siding. Pre-finished wood siding completed the exterior renovation, creating a much tighter overall envelope which required new mechanical ventilation. Andrea chose a Lunos through wall HRV. These units are great for renovations because they don’t require ductwork. A bonus of completing all of the insulating upgrades from the exterior meant minimal disruption to the interior, allowing the family to live at home throughout the renovation.
Phase 2.1 - A similar treatment for the garage
Two notable additions for improving the garage’s performance were finding the best garage door to fit the budget and the opening, which was a 3” thick insulated steel door; and air sealing the common wall between the garage and house. Andrea noticed an immediate improvement in the indoor air quality of the house after this step was taken.
Phase 3 -The mechanical overhaul
With a higher performance envelope in place, Andrea pushed pause to gather energy modeling information over the course of a year. Overall they found the exterior improvements gained them a 40% reduction in heating load. Andrea wanted to continue to use the existing hot water baseboards as the main heating source, but they are typically designed to work with 160-180° water. Heat pumps produce water temps more in the range of 120°. Out came the measuring tape and calculator because it really comes down to the math. If your heat load is x and your water temp is y then the linear feet of baseboard needed = z. If you reduce x (the heat load) but keep z (the linear feet of baseboard) the same, then you can also reduce y (the temperature of the water circulating through the baseboards). Andrea found she probably had twice the linear feet of baseboard she needed and so felt confident moving forward with a system designed to produce lower water temperatures. Her suppliers, Liquid Solar Systems and Warm Floor Systems, Inc., were also happy to verify her system findings prior to purchase and install. Finally, Andrea used the new load numbers to calculate the sizes of the solar PV array needed for electricity generation and the solar thermal panels needed for a cold climate air to water heat pump with storage tank for their water and space heating needs.
The complete package of exterior upgrades and new mechanicals was put to a good test this January - Andrea’s family stayed comfortably snug and cozy during the -20° cold snap.
For the 2400 square foot home supporting a family of four, the final system includes:
A 5.4kWp Solar PV array
An air to water heat pump with storage tank and electric coil backup, for space heating and domestic hot water
An on demand electric water heater to boost the domestic hot water temps if needed
And a new fan coil heating unit in the garage (her husband’s favorite part of the whole system!)
Transforming an existing home into a better home is good for the planet.
https://www.proudgreenhome.com/articles/5-net-zero-energy-homes-designed-to-inspire/
https://coloradosun.com/2021/04/22/energy-solar-colorado-cu-housing-environment/
http://www.liquidsolarsystems.com/
https://warmfloorsystems.weebly.com/
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