As the first official Certified Passive House in New York City, the Tighthouse embodies the opportunity for old masonry buildings to achieve exceptional energy performance.

Initial Existing Conditions.  The 120 year old brownstone building was comprised of brick and beam construction with a fieldstone foundation, typical for the area. The townhome included 2200SF on 2 levels and a full basement. Over the years the seasonal freeze thaw cycle had taken its toll, damaging the masonry extensively.

Goals.  The project balanced multiple goals, including exceptional energy performance targeting the Passive House Standard, durability/longevity, and maintenance of historical architectural elements.

Solution.  An exterior EIFS insulation system was installed with recreated decorative molding and paired with additional interior insulation.

Enclosure.  The new building enclosure went from no insulation to super-insulated. The basement includes a new R10 slab of 2"XPS with mineral wool  plus spray foam R20 and R30 foundation walls. Above ground walls of R33 are EIFS with 3" of EPS foam plus a stucco finish on the exterior and 4" waterblown closed cell sprayfoam on the interior. The roof includes polyisocyanurate and medium density spray foam to yield R60.

Systems.  A ducted air source heat pump system provides space conditioning, offering heating, cooling, and dehumidification. A Zehnder HRV completes the package with highly efficient ventilation and heat recovery. A solar hot water system provides the majority of the home's annual hot water demand. Auxiliary heat for domestic hot water is provided by an electric backup tank. Energy use is partially offset by a roof mounted 2.5kW photovoltaic system.

Result.  Passive House Certification for the building has been finalized, with an infiltration rate of only 0.38ACH@50. The projected heating cost is $260/year and projected cooling cost is $52/year. If there was room on the roof, an estimated additional 2.4kW photovoltaic system (2.5kW already installed) would offset all remaining consumption, yielding net zero energy.




- PaSsive House Consulting

- Mechanical Design



Certified Passive House


EUI: 8.2kBtu/sf/yr
Air Leakage: 0.38ACH50
Better Than Code: 84%
Heat Demand  4.42 kBTU/(ft2yr)
Air Tightness  0.38 ACH50 (first test)
Primary Energy  35.00 kBTU/(ft2yr)
Cooling Demand  1.42 kBTU/(ft2yr)
Heat Load  6.08 kBTU/(ft2yr)
Cooling Load  7.74 kBTU/(ft2yr)


EIFS stucco
Steel beam
Steel studs
U Value 0.16
EIFS with EPS foam, closed cell spray foam and mineral wool
R10 Slab
R20/R30 Foundation
R30 Above Grade Walls
R60 Roof


Ducted air source heat pump (9HSPF, 15 SEER)
HRV (95% sensible, 0.42 W/cfm)
Hot Water
Solar hot water


Fete Nature Architecture
ZeroEnergy Design
Passive House Consultant
Mechanical Designer