Building Net-Zero homes at scale for a few cents more per square foot compared to standard building costs!
A “Net-Zero” home produces as much energy as it uses through solar or wind production. This has been an obtainable goal for decades, but always at an exorbitant price point.
The ability to build Net-Zero homes for virtually the same cost as “regular” houses changes everything. The conventional home will have utility bills of $375 per month and the other will have little to no power costs at all.
This is the story of a builder who put net-zero to the test in a Habitat for Humanity project in Calaveras County, California. His patent-pending procedures are a huge leap forward in the science of building energy-efficient homes. The impact for people and planet is enormous.
The Project
In July of 2019, Tom Danielsen had the idea to build an experimental home to prove beyond any doubt that the energy efficiency numbers he was seeing in his construction work would:
- Be replicable at scale
- Have a similar square-foot cost as traditionally built homes and
- Have his energy efficiency numbers measured and verified by an impeccable third party so that no doubt remained.
Danielsen was serving on the board of Habitat for Humanity in Calaveras County. Part of the mission of this nonprofit is to help people obtain housing that is safe, comfortable and affordable. This includes having an energy profile that yields low utility bills. He brought his idea to the board and they loved it.
Danielsen Construction & Energy Management, has been building energy efficient homes and upgrading existing units for years. The efficiency numbers he was seeing, and the cost at which he could implement them, were impressive. He wanted a test case and a truly unbiased third party to verify his findings.
Enter Torsten Glidden, a contractor for the U.S. Department of Energy’s Building Technologies Office and the Technical Lead on their Home Energy Score.
Danielsen spearheaded the energy reduction on the project. He worked with general contractor Jason Jarmin, who was asked to make only minor adjustments to the way he framed the house; the cutouts for plumbing and wiring remained the same. Danielsen took over the middle of the project for sealing, insulation and HVAC.
An important part of this test was to encourage the occupant’s to make their home comfortably warm in the winter and cool in the summer. They were told to set the thermostat and forget it. This meant the HVAC was on 24 hours a day 365 days a year.
PG&E’s yearly True-Up bill confirmed what Danielsen and Glidden had been tracking all year: amazingly low household power utilization with absolutely no restrictions on energy use.
They achieved their goal of building an ultra-low energy home for virtually the same square-foot cost as what people see every day on the open market.
The Results
The utilities rating of a home with solar panels occurs after one year of energy use by what is known as a “True-Up” statement. This weighs how much solar energy was produced that year versus how much was download from the grid (on a “grid-tied” system).
In such a home the solar panels feed electricity to PG&E when the sun is shining in the daytime and draw power back to the home at night.
In the state of California, an average utility bill runs about $375 per month. In Calaveras County, with its hot summers and cold winters, the average home utility cost is at least that amount.
The total yearly True-Up bill for the Habitat for Humanity test house — with absolutely no power use restrictions — was just $310. This is less than the average utility cost of a home for just one month! It is in line with what Danielsen had been seeing for over a decade.
How it works
When it comes to making a home energy-efficient the three main topics are: the quality of the insulation, the way the house is air-sealed and the star of the show: the HVAC System.
Insulation
QII Quality of Insulation Installation standards are a part of the building code of California. Tongue twisting aside, the quality of the installation of your insulation plays a major part in the energy efficiency of your home. This is why fiberglass bats (insulation rolls) are not allowed in a Danielsen home because they do not perform.
The Danielsen team installed BIBs (Blown In Blanket) in the walls and ceiling. They followed a rigorous installation methodology developed by Danielson. This includes burying 70% of the duct-work in the BIB; a step that can only be achieved with proper planning.
The windows on the project were Amsco Vinyl 366 Low E Argon gas high efficiency dual pane. These affordable windows reflect the sun and insulate with enviable efficiency ratings all year long.
Danielsen had Jarmin frame the house with “open outside corners” to allow for more insulation and called for only minor changes in the way most contractors frame houses. None of the changes above are radical, however each small improvement builds on the next to add up to a huge percentage of energy savings.
Air Sealing
When most people think about air sealing their mind goes to the weather stripping around their front door. While this is a highly important spot, the fact is you can easily see if there are gaps or spaces in this visible area.
One of Danielsen’s favorite air-seal spots is the plumbing cutout under the bathtub. This is a 4 x 6 inch open-air cavity in a standard raised foundation home. A lot of builders miss this.
Danielsen uses single part can-foam or caulk at different points in his air sealing work depending on the size of the opening and the shape and texture of the surrounding area.
Danielsen’s other favorite areas for air sealing are the wall-framing cavities, the bottom frame-plate to the subfloor, the drill holes for plumbing, wiring inlets, plugs and light switches and of course register exchanges.
HVAC Efficiency
By far the most essential aspect of an energy efficient home by Danielsen is the HVAC system. It is important to note that most HVAC contractors size their HVAC systems by guessing. It goes like this:
A 600 to 1,200 square-foot home gets a two or three ton HVAC system. If a home is 900 to 1,600 square feet it gets a three or four ton system. A 2,500 square foot home gets a five-ton system and so on.
All of the above is guesswork. Knowing how much heating and cooling to put in any one room, much less in an entire house, requires a high level of expertise and tools. Danielsen uses a software package to calculate the load for each individual room in a house. It all adds up to determine the proper HVAC system size for the entire home.
Danielsen wants the smallest HVAC unit possible for each home, a $4,000 HVAC system instead of a $8,000 or $12,000 one (equipment costs only). This is one of the big reasons Danielsen can be cost competitive at “Net-Zero.” Also, small HVAC systems raise efficiency ratings and long-term money savings on energy use.
The software Danielsen uses to determine HVAC size requires accurate information: window size, overall insulation capacity, orientation to the sun, geographic location and much more.
This allows for a custom calculation for the load for each room, the size of each register and air duct requirements based on run length inputs. Part of the calculation is register placement — which ideally yields a convection effect. This eliminates the guesswork when sizing an HVAC system and adds comfort and money savings long-term.
HVAC systems don’t get up to full efficiency until they have been running for 10 – 15 minutes. A large HVAC unit in a small home can go on and off every 10 minutes. This produces more noise, is dreadfully inefficient and makes for far higher utility bills.
At the end of a job Danielsen “commissions the system,” meaning he checks to make sure everything is working right. In the end, his clients have a custom tuned HVAC system for their home.
An easy sell
Superior comfort, energy savings for the life of the home; spending very little extra money to buy a better home and the good feeling people get when they act in an environmentally friendly way; these are the hallmarks of a Danielsen-built home.
The “proof of concept” of this Habitat for Humanity home is a big step in allowing Danielsen to offer classes to the building trade on his patent-pending methodologies to make homes more energy-efficient. You can contact him at here.
