Bulgarian Equinox Passive House Bows Before The Sun

When real estate agent talk about their mantra for success – “location, location, location” – they usually are talking more about the income of the neighborhood and the proximity to amenities than about the movements of the cosmos. In Bulgaria, though, one architecture firm based not only the location but the design of the house on the precise angle of the sun.

Ignatov Architects, based in Varna, Bulgaria, built its south-facing Equinox House to such exacting passive-house standards that the main windows overlooking a wooden deck and a spectacular view of the Black Sea are angled outward by several degrees. This tilt ensures that the noontime sun on the summer solstice is exactly parallel to the glazing so as to prevent solar gain on the hottest days.

This passive house in Bulgaria is built with its windows on a tilt to parallel the noon-time sun on the summer solstice. Image via Ignatov Architects.

This passive house in Bulgaria is built with its windows on a tilt to parallel the noon-time sun on the summer solstice. Image via Ignatov Architects.

To help residents follow the sun’s movements, the designers added an oculus, or small circular opening, on the roof facing directly south. The oculus isolates a beam of sunlight on the main floor, which is marked as a solar calendar so residents can track the months and seasons as the sun arcs through the sky.

Located on a dramatic cliff near the town of Kavarna in northeast Bulgaria, the Equinox House also contains several other passive features, such as triple-paned windows that minimize the summer heat while maximizing warmth in the winter, when the sun’s angle is lower. The house is also topped by an insulating green roof that merges seamlessly into the hillside landscaping.

A green roof helps regulate temperatures at the Equinox House. Image via Ignatov Architects.

A green roof helps regulate temperatures at the Equinox House. Image via Ignatov Architects.

The main entrance to the house, surrounded by a sloping wood and stone structure, is also located at the roofline, with the rest of the house partially embedded in the hillside. The thermal mass of the hill also provides insulation and helps regulate temperatures during all seasons.

Rooftop entrance also provides sunset view of the Black Sea. Image via Ignatov Architects.

Rooftop entrance also provides sunset view of the Black Sea. Image via Ignatov Architects.

Seals around all doors and windows are airtight, which Ignatov Architects says are tested at 50 percent above passive-house standards. The added insulation installed throughout the house, the designers add, provides a 90 percent reduction in energy used for heating, compared to a conventional building.

By following the contours of the surrounding hill, the Equinox House helps deflect the harsh northerly winds in the region. Other energy-efficient elements include a rainwater harvesting system, an onsite composting operation, energy recovery ventilation, a ground-source heat pump and a solar thermal system for producing hot water and heating the small swimming pool built into the deck.

Randy Woods is a Seattle-based writer and editor with 20+ years of experience in the business publishing world. A former managing editor of Seattle Business, iSixSigma, Claims and Waste Age magazines, he has covered topics that include newspaper publishing, entrepreneurism, green businesses, insurance, environmental protection and garbage hauling (yes, really). He also contributes to the Career Center Blog for The Seattle Times and edits a photography magazine called PhotoMedia. When not working, he likes to hide out in Seattle movie theaters and attend film festivals—even on sunny days.