The IDI Net Zero / Zero Energy Ready Home Project: Energy Efficient Wall Design Overview
What’s the big deal with net zero energy (NZE) homes or Zero Energy-Ready homes (ZERH)? Are they really worth it?
A net zero energy home is one that generates as much energy as it uses, and a Zero Energy Ready home is one that is built to the same standard, but it may not have a way to generate electricity, such as solar panels or a wind turbine.
The main goal when designing an NZE home is building a structure that uses less energy to begin with. The best way to achieve this starts with a great building envelope. This is much better than designing one that requires a field of solar panels to make up for a poorly designed or leaky building. Much has been said about NZE homes in terms of their efficiency and how little energy they use, but the biggest benefits are about comfort and durability: they include, dust reduction, improved indoor air quality, no drafts, even temperature rooms, proper humidity levels, sound attenuation and more.
Starting in the summer of 2017, and finishing in the spring of 2018, the IDI team was given the opportunity to be involved in a ZERH home from start to finish. We did our best to capture the most important stages on video so we could share them here.
The home was designed by David Charlez Designs and was built in the greater Minneapolis area. The structure is a two-story, features a walkout basement, and has 6230 sq. ft. of space.
At the base of the home, the slab was poured over two inches of Foamular foam board to help prevent the cold northern ground temperature from coming through the slab. The plywood on the exterior of the home was also covered with a 1.5” continuous layer of Owens Corning foam board. This continuous insulation prevents thermal bridging, or energy transfer, through the framing and other above ground building materials. On the inside of the walls, 1.5” of closed cell spray foam insulation sealed up and bonded together the field of the walls and then fiberglass was blown in behind netting to finish the super insulated walls and in keeping with the future goal of a Net Zero Ready building.
Sealing the Home
A major key to this home and its performance was the air sealing done on the home. You will see in the videos that while the continuous insulation was being installed on the outside, several days of air sealing were happening on the inside. When you hear terms like passive house, or anything relating to a structure with less than one air change per hour, every detail matters. The base of each wall had sill sealer or gasketing used. Every window, gap, or known penetration was accounted for.
As for the fiberglass, that was installed throughout the inside walls, this house was designed to be a place of rest, a place of joy, and a home that performs. Many contractors forget to talk with the homeowners about sound attenuation. The truth is, most homeowners don’t want sound reverberating or traveling all through the place and the time to take care of that is before the drywall goes up.
So how did it work out? Was it worth the effort? If we go by the numbers, it absolutely was. The home barely uses any energy, and it finished with a blower door number of 0.74 air changes per hour. That is a quarter of what the newest, most airtight codes require a builder to achieve. The truth is, energy bills and code numbers are rarely the most important factor. The real question is answered by the people who dreamed about owning this home. What did they think?
Q. Does it exceed your expectation?
They actually answered the question in all capital letters! This home was a win for the builder, the subcontractors, and the homeowners.
Q. How long before the mechanical system turned on?
A. 30 days.
Wow! During those thirty days, it snowed twice and both family and friends were going in and out of the home.
Q. How are the noise levels?
A. Excellent, the home is very quiet.
This home was built with high performance across the board. All of the thoughtful design considerations added up to a better home experience overall.
Find NZE Insulation Solutions
This was an outstanding project to be a part of. Our team gained experience with ZERH/NZE homes, and were fortunate to have the opportunity. The family that moved in absolutely love their home. We hope you enjoy the videos and that they inspire you to raise the bar with your projects.
IDI would love to help you take your insulation contracting the next level. As we state in the videos, if you have questions about NZE homes, or any of the products or resources IDI offers, reach out to us. Our goal is to earn your business every day.