For many a Net-Zero-Ready (NZR) home summons the mental image of a high-tech, half-dugout bunker with solar arrays merging into a green-roof garden.
But NZR homes don’t have to be architectural wonders. In this post, we’ll see how a regular airtight, thermally resistant design can achieve net-zero readiness when built with a quality building system like Element ICF.
But first:
What is a Net-Zero-Ready (NZR) Home?
It’s a home that is designed to create as much energy as it consumes once you fit it with a renewable energy source, such as solar panels. What makes it “ready” is its high-performance envelope that curbs heat flow and creates an airtight seal. With energy efficiency not seen in modern homes built to code, NZR homes reward their owners with ultra-low or non-existent energy bills.
What Is a Suitable Building Envelope for NZR Homes?
Plenty of factors can affect an NZR envelope design, such as shading, orientation, and HVAC system efficiency. But it’s the climate zone that dictates the NZR envelope’s makeup. In cold climates, an typical NZR envelope would have:
- Roof: R-60
- Above grade walls: R-35
- Basement walls: R-28
- Under-slab: R-10
- Airtightness <1.0 ACH/Hour@50
- Triple-pane windows
As you can see, net-zero readiness hinges on R-values and airtightness. So, what’s the optimal envelope system for achieving NZR?
How Element ICF Fits into an NZR Design
Element ICF scores high enough in both thermal resistance and airtightness. Let’s see how the R-Values stack up:
Element ICF wall assemblies’ typical effective R-Values
- Element ICF: R-25
- with 2-inch foam inserts: R-35
Regarding thermal resistance, Element fares quite nicely – all you need to add is the 2-inch foam insert to achieve the optimal R-values typically required for NZR above-grade walls.
But that’s not all. Element walls have a high ability to absorb heat. Known as the thermal mass, this property helps Element walls slow down heat transfer. This thermal lag preserves the indoor climate as the outside temperature plummets and delays the start of heating systems.
The benefits of ICF thermal mass are dramatically proven in this recent hot box test, when a wood-framed wall with R20 batt insulation consumed 149% more heating energy than a R23 ICF wall assembly.
So with this exceptional thermal lag effect, many builders feel comfortable they can achieve a NZR envelope using Element ICF blocks without any foam inserts.
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Airtightness
Airtightness is another variable in the NZR equation. By letting air seep in and out, a leaky envelope enables heat movement through convection and adds strain to the heating and cooling systems. On the other hand, airtight structures help reduce heat movement through their walls and keep the indoor temperature steady.
Unlike wood-framed walls, which need extensive taping and sealing to reach adequate airtightness levels, ICF walls are inherently airtight because they are monolithic. In place of membranes and tape, ICF walls’ air barrier comprises a continuous concrete plane and 2 layers of insulation. A study of 49 ICF homes showed an average airtightness of 1.26ACH@50, and a durable, long-lasting air barrier.
For a number of practical ways to further boost your Element home’s energy efficiency and achieve NZR, check out this handy infographic: 30 Ways to Add Performance to you Element ICF Home
Case Studies
Now, let’s see Logix in action in these 4 high-performance homes:
These projects were built using Logix ICF, predecessor of Element ICF.
Passive Home – Minnesota
Passive homes offer +90% in energy savings compared to their traditional peers. These homes also create superb value for their owners by adding comfort.
Passive homes demand the highest wall assembly R-values and the lowest air change per hour ratings to attain passive home status. Our case study – a ICF home in Minnesota – did just that, achieving 91% more energy efficiency and 12 times more airtightness than local codes require.
Net Zero Ready Home – New York
Self-built by a certified Passive Home consultant, this simple New York house has notably low heating and cooling loads and can sell energy back to the grid when its Photovoltaic (PV) system is on. Here are a few features of its envelope:
- Logix Platinum walls with Logix D-Rv insert panels: R-36
- Ceiling insulation: R-70
- Under-slab insulation: R-20
- HERS rating without PV array: 30
- HERS rating with PV array: 3
The key takeaway? An owner-builder made passive home construction look easy with Logix ICF , and it cost him only $126/sq. ft. to build!
Net-Zero Home – Illinois
This standard-looking single-family home
earns its net-zero status with a mix of millennia-old technologies and modern building materials. Let’s start with the latter and take a peek at its envelope composition:
- Spray foam roof insulation: R-50
- Above-grade walls: R-28 Logix Platinum
- Below-grade walls: R-25 Logix Pro
- Under-slab insulation: R-20
And here are a few more architectural features that help this home meet its cooling and heating needs without relying on conventional, fossil-fuel burning systems:
- South-facing exposure with a strategic overhang at each story
- passive ventilation with a cupola
- passive heating and cooling with earth tubes, aka ground-coupled heat exchangers, or earth-air heat exchangers
- skylights for daytime interior lighting
- 3 kWh PV array for electricity generation
This truly “green” house boasts a few cool, simple features that aid its energy efficiency. That said, its above-grade walls – the largest envelope component – are only R-28.
Net-Zero Ready Home – Northwest Territories, Canada
This one’s a genuine test of any net-zero method and technology. It’s one thing to build NZR in a warm region where the climate is on your side, and a whole other with average annual temps of 21.8°F and winters temps of -30°F.
Yet, even in this harsh environment, our example Logix home attained an impressive Energuide 85 rating and hasn’t even needed heating at times with outdoor temps as low as 14F. The owner self-built the entire home with his own hands (literally laying each Logix block by himself). Here’s what he used:
- Above-grade walls: R-28 Logix Platinum, 8-inch core, slide-in Logix D-RV panels
- Door and window openings: fully insulated Logix Pro Buck, triple-pane windows
- Under-slab insulation: 6-inch EPS foam board
Wrapping it up
Net-zero readiness isn’t rocket science: all you need are the right R-values and airtightness!
To this end, Element ICF is an optimal choice that easily meets and the exceeds the thermal performance required in NZR homes and structures – even in the most extreme climate zones.
