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Net positive energy house
Open kitchen and floating stairs
Second open kitchen
Use existing brick and pine
Built-out basement
Cabinet and railing
Reused stairs with historic details
Bathroom tiles with recycled slate
Hybrid solar panels

Award winning transformation from an energy-guzzler asbestos clad building to a resilient and healthy spacious two-family, designed to use less energy than it produces.

  • High efficiency of the building envelope with high insulation values and optimized exposure of window openings.

  • Added decks and porches for expanding the interior visual space, to connect to nature and as social spaces.

  • Building materials  reused or recycled.

  • Healthy indoor air quality with heat recovery ventilation.

  • Spaciousness through design: Efficient use of small floor areas for spacious feel for the interiors with open floor plan, lots of daylight & transparencies.

  • Hybrid PV and thermal solar panels produce electricity and heat or more energy than needed. 

  • Entirely free of fossil fuels.

  • Recycled furniture  complete the sustainability of the project.

  • Landscape design to store stormwater for detention and reuse.

net zero (two family) 1
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 021
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 022
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 017
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 003
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 005
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 014
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 020
old dining-kitchen
Interior Insulation
Insulated Envelope, Ready for Siding
Large windows
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 019
Hybrid solar panels
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 004
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 013
low-res Maple Street West Roxbury MA 7 27 23 ©Keitaro Yoshioka 010
Almost Done

Leaky house with small dark rooms becomes a highly efficient single family, spacious and full of light connected to Nature

  • High efficiency of the building envelope with high insulation values that uses little energy for great comfort in heat or in cold weather.

  • Triple glazed larger windows for expanding the interior visual space, to connect to nature and optimize exposure.

  • Healthy indoor air quality that provides fresh air to every room with heat recovery ventilation and with no off-gazing  materials.

  • Spaciousness through design:  Removing walls between small rooms for spacious feel of the interiors with open floor plan, lots of daylight & transparencies.

  • Low maintenance  and carbon conscious building materials  

  • Solar panels produce electricity and heat for more energy than needed. 

  • Entirely free of fossil fuels.

Net zero 2
Solar (2) two story apartments

Solar (2) two story apartments

Before Construction

Before Construction

Double height to basement

Double height to basement

Windows for basement living

Windows for basement living

Affordable minimal rails for openne

Affordable minimal rails for openne

  • Transformation from (2) small one-bedroom apartments to (2) spacious two-story 3-bedroom units within the same volume and rearranged roof.

  • Redesigned roof optimized for thermal solar collection for domestic hot water and radiant heat in concrete floors. 

  • A super insulated envelope, as well as heat recovery ventilation reduce heating/cooling needs.

  • For water conservation, a large tank collects rain water for irrigation. 

  • Recycling: Most demolition debris reused materials for the construction of this house. Only two dumpsters were needed for the entire renovation/construction.

Three goals in this design:

1. Change the crowded feel of small, tight spaces. Transparency both with materials and through layout by making one space flow into the adjacent space and thus making overlapping spaces that belong to both spaces and enhance the spaciousness of both areas. Glass as an ambiguous separator enhances this strategy.

2. Enhance the connection to good views while reducing the impact of the proximity of the large volumes of adjacent houses on either side and a warehouse at the rear. Preserving usable yard space and making a more direct connection to the exterior. Our addition reaches out to the distant views of forested hills, previously barely visible, with a triangular addition and an attached deck at the third floor. With its proximity to a large tree, it becomes a tree house . Steel posts supporting the deck tray at the third floor are sloped so they do not interfere much with the usable yard space. Using steel rather than wood made this support system both more dynamic and light.

3. Work within a limited budget. Minimal redesign for cost saving on the lower floors, but the expanded attic with its sculptural additions became the main living space.

This is an addition/renovation to a builder’s house with a limited budget. Much better insulation envelopes the house and reduces energy costs. The siding make the volumes of the additions solid like the body of the house to match the existing siding form. This accentuates the sculpture of the staggered triangulated boxes.


The total renovation and addition of this former workers’ cottage accommodate this couple’s need for both private and entertainment space, as well as for their home offices.

  • The addition was designed to optimize solar exposure.  

  • A light-filled large room accommodates a living room and open kitchen that contrast with the small rooms of the existing cottage.

  • A window between rooms doubles the access to light from a skylight.

  • Exposed existing framing adds interest in the expanded ceiling height and saves on framing.

  • A very efficient envelop and new technology in efficient heating and cooling systems have qualified this house as a DEEP ENERGY RETROFIT, ready to become a Net Zero Building with the addition of solar panels.

  • The roofs are designed for optimal collection from future solar panels.

  • With this additions green roof and a green wall, the addition is less intrusive to the surroundings and provides for storm water detaining. Permeable paving on the driveway increases the storm water absorption.

  • We reinvented this 180-year-old house in downtown Cambridge to an energy-efficient, spacious house with room for entertaining and guests to stay and for a small second apartment.

  • The house had many small rooms and very steep narrow stair cases. These were removed together with many interior partitions. With no details having remained from this once elegant mid-19th century house, we chose to expose interior layers as part of the house's décor and used a rougher materiality for the new elements, such as the floating steel staircase, the exposed cement board, and the copper flashing used in the kitchen/dining room.

  • The house received a highly efficient envelop, that lowered the energy bills to less than half and qualified this house as the DER rating.

  • A new deck (and egress stair) provide outdoor living space. A green screen system allows this space to be secure with vines growing to provide privacy screens and a connection to nature in this tight hardscape urban environment.

Kitchen dining_edited
Bath 2_edited

Green Renovation to Newton Home: 

With our redesign, it was not necessary to build an addition, that the client originally thought was essential.

  • By reconfiguring the layout and connecting rooms that were very isolated, the redesigned house feels spacious and full of day light and works much better for a modern family with a spacious kitchen at the heart of the house. We even found space for a new library room.

  • This renovation has much improved the thermal and environmental comfort without being extravagant or without using untested materials or systems. The green renovation’s result is a house with at least 40% to 50% reduction in energy costs.

  • Healthy and resource efficient materials were used throughout.  . 

  • The project was featured in the TV show “Green Home Renovation.”

  • This house had no connection to the good views down the hill, nor to the backyard patio area. We moved the kitchen to the middle of the house and created a family room in the old kitchen extending it with glass doors to the backyard.

  • The front was reorganized by moving the entrance vestibule from the front to the side of the house, expanding the living room into the porch  and opening up views from it down the hill with a new porch in the old entrance space. 

  • This freed up the basement wall and allowed us to convert the dark basement rooms into  walk-out basement with  a study and guest room with full windows to the yard.

Solar farmhouse
  • Pole construction, exposed wood and stone, and high cathedral ceilings invoke the majesty of the surrounding Maine pines and define the character of this pristine farm house. We designed the original house as a vacation house for a family of four. Ten years later the client asked us to design a home addition. Using sustainable strategies was a high priority in both phases of design.

  • The building is shaped to capture solar heat through the many south facing windows and stored in the large field stone fireplace and brick wood stove.

  • Active solar gain from solar thermal panels on the roof heat domestic water and the radiant floor. Openings were placed strategically to maximize ventilation on hot summer days and minimize heat loss during the winter.

  • In the addition, the living room connects to an octagon that reaches into the landscape providing the client with a protected place to connect to views of their site during colder weather.

  • The guest room is submerged half way into the ground to reduce heating/cooling.

  • Much of the timber for the building and the wood that fuels the stoves comes from the site. Field stones from the site were used for the fireplace. This reduces the energy need for harvesting and transporting these raw materials from other areas and help with the forest management on their land.

Dormer before

Dormer before

Renovation/addition with new dormer


We redesigned and expanded this house with an addition at the back of the house.

  • The addition connects indoors to outdoors to take advantage of views of the ocean, of the client’s gardens and of the local wild life and provides additional space,

  • To match the Greek Revival style we used classicist forms that accentuate the style of this house.

  • The addition includes a family room on the first floor, and a master bedroom suite with decks looking out to the ocean on the second floor. An existing dormer was redesigned to further accentuate the historic style of the house.

  • The new spaces capture solar heat in the winter, while operable openings eliminate the need for summer air conditioning by allowing sea breezes to cross ventilate the space. This works particularly well with windows in the added octagonal shape that houses the family dining area. 

  • The plumbing drains were separated to be able to use the grey water from showers and the washing machine for watering gardens in this sometimes drought stricken area.

  • The project was approved by the Historic Commission.

Before stylistically clashing window


On Boston’s historic Beacon Hill, we combined two small condominiums on the fourth and the fifth floors of this building.

  • Our goal was to make a strong connection between the two levels and to take full advantage of light streaming in from above with a new elegant stairway and a skylight .

  • A 1970’s treatment of the rear facade was replaced by our redesign with historically more appropriate windows and a slate roof and a better connection to the deck.

  • These historically more appropriate details gained approval from the neighbors and the Historic Commission.

  • This very small house has a view of the ocean, but its layout prevented a frequent enjoyment of this view. We moved the kitchen from the rear to the ocean views next to the dining room.

  • The former kitchen became a cosy library.

  • Because all spaces are small, we used translucent materials that allows light to shine through day or night to increase the sense of spaciousness.

  • With the renovation, this house was made much more family friendly: The small and dark kitchen was expanded into the porch and made comfortable for the family to "hang out."

  • Bedrooms were upgraded and bathrooms were made more luxurious with expansions or better access to daylight. 

Anchor 1
  • This split level house sits on a tight spot with limited yard space to the South.

  • the ground floor is transformed  into an in-law apartment  and a new top floor replaces the family room that was absorbed by the apartment.

  • The structure is planned to have a well insulated envelope for minimal energy use to operate the house..

  • under construction

  • The renovation  of this house and an addition resulted in a better spacial flow and connectivity with  new large kitchen at the heart of the house. 

  • The energy efficiency was greatly improved with an improved building envelope, including new windows and added solar panels.

AA010 Photo Keitaro Yoshioka
  • The family in this Arts and Crafts house needed more space and a better connection to the backyard.

  • A complicated rear facade was simplified and the design matches the style of the house to look like it had always been there.

  • The addition houses a new family room well connected to the patio and a new master bedroom over it.

JA Winchester

  • A third-story addition adds to the second floor making a two story apartment.

  • The third floor footprint is reduced to reduce the volume and provide decks with views of the ocean.

  • The first floor living space is expanded  into the walkout ground floor.

  • New decks on the main floors connect well with the spacious backyard.

  • This house is transformed into spacious two-story apartments.

  • This house now works for three generations of this family.

East Boston
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