Page 51 - Zero Net Energy Case Study Homes-Volume 2

PERLITA PASSIVE HOUSE
CASE STUDY NO. 7
Post-Occupancy: Observations and Conclusions
The house consumes more energy than calculated by the PHPP, similar to the Passive House of Case Study No. 6, but as noted above it is still net positive by some amount. More cooking activity than originally calculated appears to be the principal difference in the measured data.
The solar PV system is relatively small (<6 kW) and is capable of providing the energy to make house plus electric vehicle (EV) together ZNE.
In 2019, the Perlita Passive House was certified as a “Petal Certified Renovation” by the Inter- national Living Future Institute (ILFI), which is one of the few certifications for ZNE buildings. To obtain such a certification from ILFI, the building is required to be all-electric as well (no carbon based energy sources such as natural gas).
The Perlita Passive House is expected to receive certification as Passive House Plus6, which requires a greater energy-efficiency and generation of a minimum amount of renewable energy.
Since there are always “lessons learned” in any building project, there are issues to note for consideration in future projects. This is particularly true in these case study homes, which are on the leading edge of design and construction innovation and therefore unfamiliar to most in the the building trades and to many designers.
As an example of such experiences, one of the owners observed that the choice of a custom- designed HVAC system as described above was effective for himself, as a trained mechanical engineer, but a standard approach using an HRV with a mini-split heating/cooling system would be a preferred choice for another type of client.
As with Case Study No. 6, the owners of Perlita Passive House now think that a kitchen exhaust fan that exhausts air directly outside via a simple wall penetration is preferable to a recirculating kitchen hood. The indoor air quality is noticeably different to the owner-occupants.
The airtightness membrane, selected as a method to air-seal the framing gaps and openings, proved to be difficult to work with and too fragile. The result was that the builders experienced many tears and material breakdowns that had to be sealed by various means, including the use of tapes and caulking. The Blower Door test as a result proved difficult to do, with leak patching of the membrane requiring much time and effort. The owner’s conclusion is to rely on proven techniques and an airtightness system listed by Passive House7.
6 A building built to Passive House Plus is more efficient — it may not consume more than 45 kWh/m2 per year of renewable primary energy. It must also generate at least 60 kWh/m2 per year of energy in relation to the area covered by the building (building footprint). (Note: for Per- lita Passive House, this renewable energy generation total was 97.6 kWh/m2 for the measured year, more than 50% above the required amount.)
7 https://database.passivehouse.com/en/components/list/airtightness_system Zero Net Energy Case Study Homes: Volume 2
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