Habitat for Humanity House – Proof of Concept
Building Net-Zero* homes for pennies more per square foot!
*A "net-zero" house produces as much energy as it uses through solar and wind power production.
A net-zero building has been an obtainable goal for decades, but always at an exorbitant price point.
This story shows how the energy efficiency of a new home gets amazingly close to net-zero, with scarce few solar panels, at virtually the same square-foot cost as a size-consistent tract home in California.
Building Net-Zero* homes for pennies more per square foot!
*A “net-zero” house produces as much energy as it uses through solar and wind power production.
The Holy Grail of energy efficiency in home building is a “net-zero” house that produces as much energy as it uses. This has been an obtainable goal for decades, but always at an exorbitant price point.
This webpage outlines the story of a builder whose innovations allow the energy efficiency of a new home to get amazingly close to net-zero, with scarce few solar panels, at virtually the same square-foot cost as a size-consistent tract home in California.
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 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 Habitat for Humanity 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’s company, Danielsen Construction & Energy Management, had been building new homes and upgrading energy efficiency in existing units for years. The efficiency numbers he was seeing, and the cost at which he could implement those numbers, were impressive. He wanted a test case and a truly unbiased third party to verify his numbers.
Enter Torsten Glidden. Torsten is a contractor for the U.S. Department of Energy’s Building Technologies Office and is the Technical Lead on their Home Energy Score. His reputation as a fair and impartial inspector provided the perfect finish to the team.
Danielsen Construction & Energy Management spearheaded the energy reduction in the project. Danielsen worked with general contractor Jason Jarmin, who was asked to make only minor adjustments to the way he framed his houses; the cutouts for plumbing and wiring remained the same. Danielsen took over the middle of the project for sealing, insulation and HVAC; then handed it back to Jarmin for finishing.
The building team was set and the experimental home had one additional aspect of high importance: They wanted real numbers! They needed a test that could be replicated at scale.
An important part of this test was to encourage the occupant’s to make their home comfortably warm in the winter and happily 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. The point was to see how people really use energy in their homes.
For this experiment, the occupants would have no restrictions on energy use and the Habitat for Humanity team succeeded beyond their wildest expectations. At the writing of this article, this experimental home has a full year of data behind it. PG&E’s yearly True-Up bill confirmed what Danielsen and Glidden had been tracking all year: amazingly low energy use with absolutely no restrictions on any household energy activity.
They also achieved their goal of building an ultra-low energy home for no more square-foot cost than what people see everyday on the open market.
The Results
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. This is mitigated by the fact that this 1,250 square-foot home is on the small side. Another factor to consider is that this home is 100% powered by electricity, which for heating water is not as efficient.
In this home, a utility bill of $250 – $300 per month would be about right; the higher number would be for people with no energy inhibitions like our occupants.
The total yearly True-Up* bill for this house was $310. This is a incredibly low number for a full year of energy use in any home; and it is especially significant when that house has a solar array with just 8-panels.
This is in line with the type of numbers Danielsen has been seeing for over a decade in his home building and retrofit work. Keep in mind, these numbers are verified by Torsten Glidden and PG&E.
Please note: because this was a Habitat for Humanity project, a solar company called Technical Specialty Solutions donated a small 8-panel, 2.76-kW solar installation to the home. The value of this contract was $8,950, and it came close to zeroing out the energy bill for the home.
*A PG&E True-Up occurs after one year of energy use in a home with solar panels. 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. This is known as grid-tied solar and is billed annually.
How It Works
In any discussion of how to make a home energy efficient the three main topics are inevitably:
- The quality of the insulation
- The way the house is air sealed
- The star of the show: the HVAC System.
Insulation
QII Quality of Insulation Installation standards are a part of the building code of California. This means that the quality of the way you put in your insulation plays a major part in the energy efficiency of your home.
The Danielsen team installed BIBs (Blown In Blanket) in the walls and ceiling following a rigorous installation methodology developed by Danielsen. This includes burying 70% of the duct work in the BIB; a step that can only be achieved with proper planning.
The insulation and sun reflectivity of the roof are of high concern, as are some subtle differences in the way houses are framed.
Danielsen had this house framed with “open outside corners” to allow for more insulation. This is only a minor change in the way most contractors frame their houses. Each small improvement builds to add up to a large percentage of savings over a time.
Air Sealing
When most people think about air sealing their mind goes to the weather stripping around their front door. While this is an important spot, you can easily see if there are gaps in the weather stripping on doors. Let’s take a deeper look.
One of Danielsen’s favorite air-seal spots is the plumbing cutout under the bathtub. This is critical in a standard raised foundation home. The bath cutout is typically a 4 x 6 inch open-air cavity. If this is not filled in it becomes a gaping hole for air leakage.
Danielsen’s some other favorite areas for air sealing are the framing cavities, the bottom frame-plate to the subfloor, all drill holes for plumbing, wiring inlets, plugs and light switches and of course register exchanges.
HVAC Efficiency
The star of the show in a Danielsen-built energy efficient home is the HVAC system. Most HVAC contractors’ size their HVAC systems by guessing. It goes like this:
A 600 to 1,200 SF home gets a two or three ton 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 an entire house, requires expertise and the right tools. Danielsen uses a software to calculate the load for each individual room. This adds up to determine the proper HVAC system size for an entire home.
The residential software package he uses is called Right-Suite. This is a robust program that takes time to master. When building a profile for the load of a whole house, Right-Suite calculates the load of each individual room, which includes the size of each register and the air duct requirements based on run lengths. This eliminates all guesswork in sizing an HVAC system for a home.
Danielsen wants the smallest HVAC unit possible for each home. A $4,000 HVAC system saves you from buying a $8,000 or $12,000 one (equipment costs only). Not only that but it raises efficiency ratings and long-term money savings.
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 and becomes dreadfully inefficient and is a significant drag on the cost of utility bills.
Danielsen then “commissions the system,” meaning he checks to make sure everything is working right. In the end, people have a custom tuned HVAC system for their home.
An Easy Decision
Superior comfort, energy savings for the life of the home; spending no more to buy a better home and the feel-good of being environmentally friendly are the hallmarks of a Danielsen-built home.
or give me a call at (209) 728-4921