For better homes, is it Net Zero or Passive House?

May 7, 2020 by Kiara Fullham

You may have heard of Barry Schwartz’s famous “Paradox of Choice.” The premise of Dr. Schwartz’s paradox is simple: while our instinct is to believe that more choice is better, too many choices can overwhelm us and make our lives more difficult.

As it turns out, there are limitations to this paradox. When you’re particularly well-informed, having a lot of choices can still be advantageous. The world of Eco Trends seems to follow this rule - while it seems overwhelming at first, living a green lifestyle becomes easier when you have a deep understanding of your options. Today, we’re going to look at what seems like a choice: Passive House vs. Net Zero. As you’ll see, these two housing options aren’t as different as they might seem at first glance.

Understanding Net Zero

Net zero homes are the easiest to explain. You’re probably well-acquainted with the term carbon footprint. Your home is one of the biggest contributors to your carbon footprint, especially if the utility that supplies you with power uses coal or other fossil fuels as its main source of electricity. The goal of a net zero home is to reduce your net carbon footprint to zero.

This means net zero isn’t a house building standard, as such. Net zero homes don’t care how you reduce your home’s carbon footprint to zero, they just care that you do it. You should also take note of the term “net.” Net zero homes can use fossil fuels, but their use of those fuels must be offset by some other means of energy generation. So, for all the fossil fuels your net zero home uses, it must create enough renewable energy to replace the non-renewable energy it used. 

Net zero homes almost always require some form of renewable energy source, typically solar panels. Without renewables, it becomes impossible to offset greenhouse gas use from furnaces. The building materials used in the home are also considered for net zero.

There are advantages and disadvantages to the net zero lens. The biggest advantage it grants is flexibility. The focus on achieving a net zero target means that buildings can be customized for particular climates and lifestyles. You might, for example, work to reduce your electricity consumption at home in order to meet the standard. The way you construct your home can also help you reach your net zero standard - we’ll talk more about that soon.

The disadvantage to net zero also comes from its flexibility. The lack of a rigid standard means a lot of homes could be considered net zero. Do you live in a lean-to made entirely out of branches and stones? Technically net zero, assuming you don’t light wood fires to cook. Do you have a home that’s heated entirely via hyper-inefficient coal furnaces? As long as you have a solar array that’s big enough to offset the carbon being released, it’s technically net zero. Net zero, then, is a goal, not a guide.

Understanding Passive House

In contrast to the relative customizability of a net zero home, Passive House has a fairly rigid set of standards. Created by the Passive House Institute (PHI), the focus of the standard is the reduction of emissions through the use of insulation.

The premise behind Passive House is simple: climate control is the average household’s biggest contributor to carbon emissions. Most furnaces still burn natural gas, and when it’s cold outside they have to burn a lot of it. Proper insulation keeps your home warmer in the wintertime and cooler in the summer. That’s because insulation stops heat transfer in both directions, as heat is always trying to dissipate towards cold. 

The technical requirements of Passive House are fairly straightforward: Heating energy can’t exceed 15 kWh per m². Cooling costs are similar, but there’s a bit of leeway for dehumidification. Total household energy consumption can’t exceed 60 kWh per m². Finally, there must be no more than 0.6 air changes per hour (ACH) at 50 Pascals of pressure. That’s a metric that evaluates how airtight your home is. Passive House also requires that the home maintains a level of thermal comfort all year round. It should be noted that in the U.S. a similar but distinct standard has gained traction in the market, offered by Passive House Institute U.S. (PHIUS). While the goals are very similar to PHI, PHIUS instead uses a climate-specific approach to setting requirements in order to capture the nuances of a wide array of U.S. climates

There are a lot of techniques and technologies that can be applied to make a home meet the Passive House standards. The principle technology is insulation. Everything needs to be well insulated, so heat transfer resistant doors and windows must be installed. All the floors, walls, and the attic must be very heavily insulated. To do so without using an excessive amount of insulating material, home builders are turning to technologies like rigid insulation and aerogels.

When your house is hyper-insulated, another problem arises: stale air. With so little air circulation, you’ll need a ventilator for your home. Traditional ventilators would simply transfer the air from the inside out, so you’d see temperature changes. Today, there are heat recovery ventilators (HRV) that heat incoming air using energy from the outgoing stale air. Energy recovery ventilators (ERV) work in a similar way, but they also exchange humidity, keeping your home’s humidity levels constant. 

Passive House or Net Zero: Why Not Both?

There’s really no competition between Passive House and net zero. If you build your home to Passive House standards, you can probably transition it to a net zero home with relatively few changes. You’re already limiting your energy consumption by adhering to the Passive House standard, so the only thing you’re missing is some way of offsetting your home’s (now drastically reduced) carbon footprint. 

Solar panels are typically the most efficient way of going about this. You might also opt to use pico or micro hydro if you have running water on your property. Owners of particularly large properties might even choose to create a small wind farm. In other words, if you build a Passive House, you can probably choose your favorite method of generating renewable energy and use that. Passive House and Net Zero: better together! 

About the author
Kiara is a writer based in Canada. She writes articles with a focus on marketing and home improvement for a variety of businesses. Some of her best work has been featured on the Provincial Heating website.