Passive House vs Net-Zero homes. What is the difference?

June 2, 2020 2:18 PM

PH needs to meet certain (what) thresholds to get certification. What about NZ? Is there a certification also? Who? In the end, does not a PH come within inches of NZ? So who cares?
posted by ebesan to Home & Garden (4 answers total)

A few significant differences exist between them. Passive House is a prescriptive approach, requiring certain levels of performance of building components which can be determined prior to or during installation and tested for prior to building occupancy. Net Zero can be modeled and intended, but cannot be verified until a property has been occupied for at least a year. As such, Net Zero is dependent on occupant behavior, while Passive House is descriptive of the structure only. Another significant difference in most cases is that Net Zero requires an on-site renewable energy source to offset building energy consumption. Passive House deals with reducing consumption, but not mandating energy production.

There are many other differences that emerge from these divergent approaches of course, but those capture the spirit of why one or the other (or both) might be selected as a target.
posted by meinvt at 3:06 PM on June 2, 2020 [3 favorites]

Making a building to passive house standards could be one way of getting to net zero, but you'd have to do more- even if the building uses mostly or all natural light during the day, you'd still need renewable energy to cover lighting at night, along with other things that use electricity, for example (the main focus of passive house design is reducing the need to heat or cool the building). International Living Future Institute has a zero energy certification.
posted by pinochiette at 3:39 PM on June 2, 2020

Passivhaus information, standards and certification, for clarification. From the same source, Passivhaus and zero carbon.
posted by Martha My Dear Prudence at 4:48 PM on June 2, 2020

for certification in NZ: https://passivehouse.nz/about/about-passive-house/
Standard (in the US) is:
-up to 15 kwh/square meter for heating and cooling
-up to 60 kwh/square meter for total primary energy (thats accounting for electric plant efficiency and transmission loss)
- up to 0.6 Air changes per hour leaking through the envelope at 50 pascals pressurization (1/3 the leak rate of the tightest house I have lived in.)
-a handful of other materials and design requirements

You have to make a number of challanging design choices for envelope and hvac design to meet these thresholds. (Lots of insulation, thermal brakes in the studs, triple pane argon windows, heat recovery ventilation etc.)

Net zero energy(net zero energy is quite different from net zero carbon) just requires you to produce more energy on site (usually with solar) than you consume. Net zero carbon has you trace all the embodied carbon in construction and operation, and requires you to offset consumed bcarbon by producing carbon free energy in excess of what you use.

Who cares: Well I care. But if you meet any of these guidelines, your household impact is lower than that in most developed nations. My observation is that Passive house standard enables net zero (energy or carbon) without needing your solar pv array to be enormous, and can be achieved with great design alone. Net zero is more behavioraly driven.
posted by QualityMayVary at 7:09 PM on June 2, 2020