SBN has reached full development (01-02). We have designed a 1,281 sq ft home that addresses affordability and sustainability while also providing the infrastructure for incremental growth over time (03). One way affordability is addressed in SBN is the concept of incremental growth. Though a family may have limited means today, the proposal provides the necessary structure to expand the home and add an income producing unit on the flat roof of the master bedroom suite. The LGW (Living Green Walls) can be transformed to support the roof of a future carport. By creating two wings of the home, the proposal seeks to highlight the importance of the dining room and open kitchen as the heart of the home. The bedrooms private nature contrasts with that of the other more public spaces. The dining space mediates and provides the bridge at the axial shift that occurs in plan (04). The designed site plan provides seating areas on the North and South sides and rainwater harvesting tanks along the East and West facades (05).
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Saving energy over the operating phase of the home requires an airtight envelope, good insulation in the roof and walls, quality windows and exterior shading to reduce solar heat gain. The building envelope is comprised of the exterior shading in the form of the living green wall (LGW), insulated glass units, structural insulated panels (SIPs) R-22, and a white standing seam metal roof with R-30 insulation as required by code (06). On the South side of the home 24 inch overhangs are provided together with the LGWs to shade both the windows and walls. Inside SBN, the choice of flooring materials speaks to the different zones of the project. The public zone is treated with resilient flooring. Carpet was chosen as the flooring option for the private zones (07). The color of the interior walls followed the same concept. The public spaces are represented by three different colors that also make reference to the landscape (08).
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Smaller homes use less material and less energy. As mentioned, the proposal is sized at 1281sf. The total estimated cost construction cost is $129K (10).The savings in size allows more money for exterior improvements and the hybrid HVAC system. Affordability needs to shift away from a simple consideration of upfront costs towards life cycle costs. Regular maintenance homes have a potential life cycle of over 60 years. A family considering an affordable sustainable home should also consider monthly expenses that a well-designed home can reduce compared to a conventional home. Examples in this proposal are:
1) energy use
2) water conservation
Both are elements that contribute significantly to monthly expenses and both are costs that over time will only increase. This proposal reduces the carbon and water footprint of the home (11) but requires additional upfront costs that can be recovered over the life cycle of the home. When the savings, annually, is capitalized, the initial investment is further justified. ATHENA was used to calculate carbon equivalents and Energy Plus to calculate energy performance. Given the humidity in all three regions, natural air ventilation is ineffective. Instead the proposal uses a hybrid system (12):
1) dehumidifier
2) 220 sf of hot water collector coils
3) fan coil unit
4) heat pump.
The system yields a 40% annual energy savings over a conventional split unit system used in isolation. This allows the hybrid system to achieve a higher Coefficient of Performance (COP). Annual kWH for the proposal are 11,000 kWH, with peak cooling at 4000 kWH. SBN has now attempted to redefine affordable and sustainable housing in 21st century Florida.
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-PSB
Sustainable Design in Miami
http://www.bcnumber3.com
