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Off-Grid Home Design Deliverable Requirements
These minimum elements must be addressed as part of your design and should be represented in your final design report. There will probably be more to consider. The client will provide you with preferences of occupant profile and locations, so be clear on those early to define your group’s broad objectives.
Occupant Profile
The constraints on a tiny home mean designs must be well tailored to the user group and some of those constraints carry over to design of a somewhat larger off-grid home. Comparisons require a baseline to determine changes in dollar cost, social, and environmental impact. Your report must include a typical user profile like this one:
Sue owns and lives in a 900 square foot downtown Kingston condo with her teenage daughter and their dog. Sue’s MS sometimes requires mobility aids like canes or a walker and stairs can be difficult. They travel by gasoline car to multiple destinations within urban Kingston with total distance of about 15000 km/year. Purchase price for the condo was \$400K. Condo fees are \$500/month, which includes water and sewer. The condo has electric resistance baseboard heating, electric hot water, and no air conditioning. Electricity costs average \$120/month. (All in 2018 dollars.)
Your occupant profile for your client K will be different, and her objectives will drive many design details, particularly budget limitations.
Location
Determine a potential location on the property in consultation with K. This will affect sky view for solar and requirements for water and septic services. The distance from available grid connection at the road will impact your economic analysis through the cost of a potential grid tie.
Floor-plan and Building Envelope
Provide a layout for your home design that includes 1000 – 1200 square feet internal floor area. Meet building code and other standards for dimensions of passages, etc. to meet your accessibility goals. Test your plans for real traffic situations with mockups by moving furniture in a classroom or other space to match your dimensions and then moving through it and documenting the results. Be sure to consider two people passing each other, and the challenges of changing sheets on the beds. This will be less of a concern than in a tiny home.
Thermal design of the building envelope is complex. You could simply specify an overall R Value for your home’s walls and windows and make a reasonable estimate of construction costs on a $/square foot basis, taking into account the small size and energy efficiency level you are looking for. Do not attempt detailed design and costing of the building envelope beyond selecting your windows.
Energy Systems
Off-grid or Net-zero almost certainly means solar and batteries for electricity. Specify details of your solar system, selecting from available products. Specify all significant electric loads such as appliances, lighting, HVAC, car charging, etc. and select from available products.
Be clear about your required performance criteria, particularly for heating, both when the home is occupied and when it is empty. (At a minimum, it should be safe from freezing when nobody is home.)
Water / Sewer
Detail your design / costs for providing adequate clean water supply and sewage / grey water disposal at your chosen site.
Backup Systems
Your tiny home will probably need backup systems for heat and electricity that will seldom be used. Size and select appropriate systems from existing products.
Operating Simulations
Simulate the energy production, storage and consumption over a sequence of multiple days. Evaluate operating decision making required, e.g. need to run propane backup heating or gasoline generator to meet operations.
The ideal simulation will follow historical data through some segment of a Typical Meteorological Year on a suitable time step like 15 minutes or an hour. At a minimum you should look at the performance differences between
- A clear, cold, winter day
- An average winter day
- A cold, gloomy winter day with 90% of the solar energy lost to the clouds
Cost Estimates and Comparisons
Prepare dollar cost estimates comparing the off-grid home solution to the baseline solution from the occupant profile, and to a similar design with a grid connection. Your solution will have to be attractive to the potential occupant in comparison to their other options.
Compare environmental impact, particularly carbon emissions.
Regulatory Compliance
All engineered systems must comply with applicable regulations. Even when regulations have not kept pace with technology and good engineering practice, your projects must still comply. For this project we are assuming that property standards bylaws and building code requirements have been relaxed to permit more compact construction, however all other systems must be in compliance.
A “normal” dwelling will include a grid connection for electricity, city water and sewage connections to plumbing, or a well and traditional septic system where city services are not available. You must either incorporate all of these utility connections, or demonstrate that local regulations do not require them. If you are including non-traditional systems, you must demonstrate compliance with locally applicable regulations. In particular be sure to consider:
- Interior installation details for toilets other than traditional water flush units.
- Drainage of liquid waste, including either grey water or urine to the property through systems other than traditional septic beds.
- Storage and disposal of solid waste, either on or off the property.