LBC Energy Petal - Resiliency Strategy

Marisa - Not that exact flavor of ILFI program, but we've had other projects that have had to meet resiliency requirements, so a couple thoughts for you: 1. The LEED pilot credit Passive Survivability and Back-up Power During Disruptions is probably a good standard for defining habitability - in most cases, 50F is OK during winter conditions 2. We have a very large multi-family project, the scale of which made batteries technically infeasible and talked thru with ILFI the options to consider fossil fuel options as a last resort. I also think it would be eye-opening to compare the embodied carbon and other LCA impacts of batteries against other options, to at least inform the least bad path forward. -C

(I saw y'all posted in the ILFI forum, too...I'll respond here for now.) We went through a whole ordeal around this requirement on our project, as ours is a large industrial/office project, and is paid for with taxpayer dollars, so there are a LOT of rules about what the client can pay for - they're not allowed to pay for coffee for employees, for example, so having water/food stored (that is provided by the client) is even an issue. We similarly determined that batteries were not financially or logistically feasible for our project.  We had several conversations with the client team, and had them put together a description of what they considered to be minimal habitability requirements for themselves first. They had to keep in mind that the habitability aspect was really meant to represent an extended emergency situtation - not a temporary outage needing life safety elements, like emergency lighting. Then we had our energy modeler run scenarios:
The model assumed the worst case possible for two scenarios: the hottest week of the summer and the coldest week of the winter, based on historic meteorological weather data. Additional worst case assumptions used:

• All powered equipment, including HVAC, is shut down.
• Occupied rooms modeled assumed no movement of occupants between spaces (i.e., no air movement between spaces).
• No use of windows or doors for ventilation.
• Occupants were only modeled for the hottest week; this allowed for potential body heat generated by the occupants to be eliminated from the coldest week model to stay true to the envelope performance.

We got the modeling results and reviewed everything with the client team/stakeholders. We made recommendations for them to adjust their definition of habitability based on the outcomes; we stressed that any movement of people between spaces, use of open doors and windows (they have operable windows), and congregating people only in certain ideal areas of the project, etc. would only improve the modeling of the scenarios. They had no issues with the tweaks we made, so their definition and our confirmation that it could be met is what we settled on.  

Here's some case study information that may be helpful:  In 2019/2020, we did a solar + battery system for a 50-unit affordable housing project in New Orleans (where prolonged power outages are common after a late summer hurricane or tropical storm) that kept the homes habitable through a 9-day power outage after Hurricane Ida. It's typically very hot but sunny after a major storm, so we had that going for us.  The systems ran and the batteries topped up during the day and the battery allowed us to coast through at night.   The whole building is on a single battery, without benefit of load-shedding technologies other than just asking residents to moderate their use during prolonged power outages.
This project (3 stories, a mix of 1 & 2BR units, and totaled 45,000 gsf) had a 178kWp solar array and a 371 kWh battery, or 4kWp solar and 7 kWh battery per apartment.  Because the project was wood stick-framed, the embodied carbon of the structure+envelope+interiors was relatively low; the Tally model showed 23 lb/sf (112 kg/m2), or a total of 471 t (see p. 19 of our Paths to Carbon Zero Research Fellowship monograph; this number is about half of the benchmark and beat the ZeroCode target). 

To Chris Chatto's query about looking at the embodied carbon of solar and batteries in context.

• The structure+envelope+interiors totaled 471 t CO2e, or about 10t per apartment. (Typical values for this building type might be 2-3x).
• The solar, assuming published values of 615 kg CO2e/kWp, totaled 109 t CO2e, or about 2t per apartment.
• The battery, assuming 100kg CO2e/kWh (comparable to 1.35t for a 13.5kWh Tesla PowerWall), totaled 37 t CO2e, or 0.7 t per apartment.

Karina Hershberg of PAE has made the point that the embodied carbon of batteries makes the most sense if you are using them for other things.  In the case of this project, they use the battery every day to clip utility demand at 35 kW (an average of 750 W per apartment), helping them minimize demand charges. This project didn't pursue any certifications other than Enterprise Green Communities.  The measured EUI (23 kBtu/sf/yr) was somewhat higher than the model (18 kBtu/sf/yr), but not too bad.  This was an extremely low-budget project: The package of efficiency enhancements + solar + batteries added $1M ($20k per apartment) to the base construction cost of $6.4M ($128k per apartment), for a final cost of $7.4M ($164/sf); the project opened in March 2020.  What I'd do differently if I had the chance to do it again: 

• The HVAC system is one split DX system (with its own motorized-damper air intake) per apartment.  If I had to do it again I would have pushed harder for a DOAS-based system to ensure that dehumidified air was pumped through all apartments at all times, for better humidity control.  It also would have allowed a resilience strategy where we provided cool dry air but perhaps limited cooling setpoints.
• Doing load management on the honor system is a pain. The cost of load management panels like SPAN was too high back in 2019, and we couldn't moderate the setpoints on the thermostats in each unit to help moderate demand.

Finally, this whole approach is plausible here, where prolonged power outages coincide with sunny days.  Using solar + batteries to get through power outages on cold cloudy winter days would be much more of a challenge. Hope this helps.

Not under LBC 4.0, but under LBC 3.0, the Net Positive Energy imperative required "on-site energy storage for resiliency" which ILFI futher defined as "sufficient back-up battery power for emergency lighting and refrigeration use for up to one week." In our project we took that to mean the emergency lighting and not the food refrigerator that was in our project's breakroom, but the one experimental storage refrigerator that was in a lab space - spoiled food in a non-residential building was one thing, but loss of lab samples in a lab building was another. ILFI accepted this as our strategy for sizing the on-site storage in the project and didn't push on it.