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Please find below the judging results for your proposal.

Finalist Evaluation

Judges'' comments


The tiny house movement is currently garnering a lot of attention, and while this is a worthwhile initiative that demonstrates what is possible, it is unclear whether the benefits can be scaled at all. Also, it is not substantially different than a number of other prototype housing products that have been done or are being done currently around the world.

Semi-Finalist Evaluation

Judges'' ratings


Novelty:
Feasibility:
Impact:
Presentation:

Judges'' comments


Comments from Judge 1:

Exciting concept that builds on an emerging interest in tiny homes. More detail on actual energy use in summer and winter compared with output of PV system would strengthen case. In many regions, winter PV output may be a third of summer output, when more energy is needed, so off-grid viability can be a challenge. However, if teamed with an electric vehicle (mentioned but not clearly incorporated into project analysis) then the EV could 'import' extra power in cloudy, cold weather and 'export' when excess generation. Your 3-4 year emission payback period is conservative: if the occupants would have built a conventional home, embodied emissions would be higher than your 18 tons, so your savings may be bigger than claimed. Experience shows that independent water and waste systems can face problems when people go away on holiday or have guests - bugs can die or be overloaded, system limits can be exceeded. In many climates, a small, highly insulated home with limited thermal mass can require summer cooling - no mention of this, although this is when there is usually plenty of PV generation!

Comments to Judge 2:

Novelty: There have been a number of Zero Net Energy or similar demonstration house built in recent years; however, the deep engagement with the community already achieved by this demonstration project is less common and highly desirable.

Feasibility: The proposal does an exceptional job of explaining the costs and technical scope of the project. The team appears to have sufficient resources in the form of people, baseline funding, and community support to complete the project. It could be useful to provide an update on the percentage of the $75,000 project cost has been raised to date.

Impact: The impact of this project is almost entirely dependent on the ability to influence more people to choose a Tiny House and to influence those that do to choose a solar, off-grid version. It would be helpful if the authors could provide some reference data for a “typical” Tiny House to more clearly establish how this project will improve emissions over what would otherwise be built. It is potentially misleading to compare the performance of this off-grid Tiny House to only a conventional 2-person household because a significant percentage of the benefits could be attributable to the choice of a Tiny House alone (reduced square footage), regardless of energy sources and water reuse. Thus, the proposal could be strengthened with additional discussion about the status quo for currently constructed Tiny Houses and how this demonstration project would amplify the benefits of going “tiny”.

Presentation: The proposal meets all of the criteria for outstanding presentation.

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Ian Bolliger

Jun 15, 2016
07:46

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Many thanks to both reviewers for their thoughtful comments and suggestions on our proposal. We have grouped the comments/suggestions into categories and have summarized our responses (and associated changes) below:

  • "More detail on actual energy use in summer and winter compared with output of PV system would strengthen case. In many regions, winter PV output may be a third of summer output, when more energy is needed, so off-grid viability can be a challenge. However, if teamed with an EV (mentioned but not clearly incorporated into analysis), then EV could 'import' extra power in cloudy, cold weather and 'export' when excess generation"
  • Summary of changes (Section 2): Details were added about anticipated electrical use (4-5 kWh/day) and generation (6.9 kWh/day in December, 11.9 kWh/day in June). Furthermore, we have included a plot of the state of charge of our battery based on modeled electricity generation and demand, demonstrating that our photovoltaic and battery system is sized well to allow the house to function off-grid throughout the year.

 

  • "Your 3-4 year emission payback period is conservative: if the occupants would have built a conventional home, embodied emissions would be higher than your 18 tons, so your savings may be bigger than claimed."
  • "It would be helpful if the authors could provide some reference data for a 'typical' Tiny House to more clearly establish how this project will improve emissions over what would otherwise be built. It is potentially misleading to compare the performance of this off-grid Tiny House to only a conventional 2-person household because a significant percentage of the benefits could be attributable to the choice of a Tiny House alone (reduced square footage), regardless of energy sources and water reuse. Thus, the proposal could be strengthened with additional discussion about the status quo for currently constructed Tiny Houses and how this demonstration project would amplify the benefits of going 'tiny'."
  • Summary of Changes (Section 5): 
  1. CCC estimate of natural gas + electricity emissions recalculated at city level rather than zipcode level, to be more representative of target users. Result is ~7% higher estimated CO2e for average 2-person household.

  2. CCC does provide estimates of embodied emissions per square foot (using the Economic Input-Output Life Cycle Analysis, EIO-LCA approach on data from the U.S. Census American Housing Survey). These estimates are now included for “on-grid” houses of both standard (1750 sq ft.) and comparable (192 sq ft.) size in order to more clearly isolate the benefits achieved through space efficiency and those achieved through energy efficiency and local PV generation.

  3. Two emissions payback periods are now estimated, such that the reader can understand the payback period of the house relative to new builds of conventional tiny houses and a previously built house (i.e. with 0 additional construction-based emissions). Those two payback periods are:

  • “Relative” emissions payback, whereby the additional embodied energy associated with PV production, storage, and various efficiency technologies is offset due to the lack of grid electricity and natural gas use. This serves to compare the emissions benefits of this home relative to a conventional, “on-grid” tiny house build.

  • “Total” emissions payback, whereby all of the embodied energy is offset due to the lack of grid electricity and natural gas use. This serves to compare the emissions benefits of this home to an existing “on-grid” build.

 

  • "Experience shows that independent water and waste systems can face problems when people go away on holiday or have guests - bugs can die or be overloaded, system limits can be exceeded."

  • Summary of changes (Section 2): We have included a paragraph detailing back up plans for the water system and living wall for when the users have guests or go out of town.

  • "It could be useful to provide an update on the percentage of the $75,000 project cost has been raised to date."

  • Summary of changes (Section 7): Total estimated project cost has been adjusted from $75,000 to $65,000 due to budget reevaluation. Information about funds raised to date has been added; our team has raised close to $42,000 and has received about $10,000 in materials donations, together covering 80% of our total estimated project cost including labor.


Ian Bolliger

Jun 15, 2016
07:25

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My apologies for the formatting of the above response; I was having trouble with the online text editor. To clarify, each set of quoted comments are followed by the appropriate "summary of changes". A blank line separates each group of comments/changes, except for the last 2 groups, for which I could not get the editor to add a blank line. I could not find a way to edit my comment after I had seen how the text was rendered.


Ian Bolliger

Jun 15, 2016
08:06

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An addition to the responses listed above:

  • "In many climates, a small, highly insulated home with limited thermal mass can require summer cooling - no mention of this, although this is when there is usually plenty of PV generation!"
  • Summary of changes (Section 2): Several sentences were added justifying our use of ventilation, ceiling fan, and phase change materials within our roof assembly to adequately cool the house during summer in the East Bay. Additionally, we indicated that the sizing of our electrical system to meet winter heating needs (w/ lower PV production) creates excess electricity in the summer that could be used to power a standard window A/C unit should the house be relocated to a Climate Zone with hotter summers.