Insulating our way to Net-Zero: Icynene

Another integral part of creating a well sealed and insulated space involved the use of Icynene spray foam insulation. Icynene is a 100% water-blown insulation that sprays on as a liquid and immediately expands to 100 times its volume in soft foam that fills every crack and crevice while providing a flexible seal and a R-3.7 insulation value. It does not out-gas or emit any harmful fumes and it retains a stable R-value across time. It is an open cell foam, so it does not block the movement of water vapor. Icynene is a petroleum-based product (Icynene-R is a new product based on castor oil)that is a flame retarding material that will be consumed by flame, but contributes no fuel and will not sustain fire upon removal of the flame source. It must be covered by an approved thermal barrier, which our builder will accomplish by seperating it from living space with drywall.

More expensive than wet-spray cellulose, but less expensive than closed cell spray foam, our builder chose to selectively use it in hard to access or otherwise challenging areas, like the vaulted ceiling, where it clings tightly in place, helping form a continuous, insulating air barrier. Seven inches were sprayed along the roofline, for an R-25 insulation rating. EarthCraft specs say R-20 Icynene is equal to R-30 of fiberglass or cellulose on vaulted surfaces.

Note in the pictures that all ducting is being kept in conditioned space, increasing energy efficiency.

Richmond Virginia Zero Energy Home Progress & Appearance

It seems time to show how far the house has progressed and at the same time illustrate that a ZEH does not have to look unconventional. Placing the Schuco PV panels on the back of the south slanted garage roof aided in this outcome, as they are nearly unnoticeable from the street. I would add that the unusual ceiling planes of the pictured great room have caused Mark, our builder, a lot of thought in terms of where to set the boundary for the conditioned space, how to keep the HVAC ducting in those confines, and where to use loose cellulose versus spray foam insulation. It is becoming increasingly apparent how challenging it is to take the basic principles of a ZEH and translate them into a workable application.

ZEH design blueprint

Where did the design of this ZEH house come from? Good question. A lot of tiresome searchs on the internet uncovered a few rare nuggets. The first and in many ways the most fruitful was the Zero Energy Home section of Toolbase Services: the Home Building Industry's Technical Information Resource. This site has a wonderful article titled Seven Steps to a ZEH that is the closest thing to a ZEH "blueprint" out there. Links to scientifically monitored zero energy homes, like the Tuscon's Zero Energy Home were invaluable not just for the data they included, but the encouragement they provided that this is indeed a practical, achievable goal. Given we became interested in the combination of solar PV and geothermal HVAC after tossing around ideas with our builder, Mark Waring, finding the series of articles titled Energy efficiency, SIPS, geothermal, and solar PV used in near zero-energy house was like striking gold, as it documented and evaluated a series of homes using this exact combination. In looking for books on the topic, the pickings were slim. Ed Begley's Guide to Sustainable Living served as good primer for general energy-efficiency ideas, while Got Sun? Go Solar by Ewing and Pratt was a practical, content-rich guide to utilizing solar PV as part of a ZEH effort. The Renewable Energy Handbook, Revised Edition by Kemp offered a broader exploration of alternative energy alternatives. Toward a Zero Energy Home by Johnston & Gibson is a very recent release whose greatest value may be its descriptive "Case Studies" of 13 near ZEHs. Two magazines that offered some help were Solar Today Magazine and HomePower Magazine, the former focused on solar power, but from a wide ranging perspective, while the latter is more focused on real world applications of renewable energy, including solar, and yielded needed product information. In the end, working with our builder who was already experienced in building energy efficient homes, pulling ideas from a variety of sources, and considering and ruling out some promising but impractical combinations, we embarked on an informed leap of faith. Time will tell how much of a leap, and we work with our builder on a weekly basis to continue to hone and fine tune the design, in search of that elusive "zero."

ZEH: it's a system

In 1990 we built what was for its time, an energy efficient, all brick home. It included some 6 inch walls, extra insulation, a Lennox pulse gas furnace, low-flow toilets (they are forever clogging), low-E windows, and south facing glass. The rumor around our Richmond neighborhood was that we were from Vermont, and did not know how to build for the more temperate climate. Fast forward 20 or so years. My wife found a lot with river access closer to her office, so it's time for an encore, to build our single level (out of deference to aging knees) "retirement" home. Out of concern for the generations to come, for minimizing monthly bills and for an outlet for our creative expression, the notion of building a zero energy home (ZEH) emerged. After a bit of study, it becomes clear that a ZEH is not a single feature or advantage, but rather a set of complementary features which form an efficient system. That sytem consists of creating a home with a tight, well insulated envelope, minimizing the energy loads in that envelope, and adding a renewable energy source. Sounds simple, but as you move forwards it gets complicated quickly. In an email to a interested relative, I described the basics of our proposed ZEH as:

...it is basically designed as a single story home, with some bonus rooms upstairs...it will be all brick with a semi-detached garage (the why of that comes later)...the walls will be R16 and the attic R38...the walls will use wet spray cellulose and the attic loose cellulose...a conditioned crawl space...we are also using a new product on the outside of the stud walls, Dow Styrofoam SIS, (structural insulated sheathing) which will be taped, forming an air/vapor barrier, an extra layer of insulation, a shield against thermal bridging of the studs, and a structural element...pretty cool...with respect to the R levels, they are more than sufficient for our climate, as the wet spray cellulose significantly increases the thermal mass of the house... along with the tightness of the house (we aim for less than a .20 Natural Air Exchanges per Hour blower door result and a less than 4% of floor area served leakage to outside duct test result; an ERV will be installed for ventilation), the increased thermal mass may even eliminate the need for a setback thermostat, as the temperature of the house should remain incredibly stable...we are going to look into cool roofs/radiant heat barriers, but setting up the heating/coolng "firewall" at the attic floor may be more cost effective....

...we are looking at double pane, vinyl clad, low E, argon windows, with U value of .33 and SHGC of.30...we are looking into a new model with a U below .30, getting a price difference on that...

...Caroma (the reviews say they never clog) 1.28/0.8 dual flush toilets to save water...

...the HVAC system is proposed to be a Comfortaire GeoMax2 geothermal heat pump of 4 ton capacity with desuperheater rated @ 23.7/16.6 EER & 4.0 COP...hot water will be pre-heated by the desuperheater and then go to a 98% efficient Navien tankless condensing water heater with a built in recirculation pump & mini buffer tank for a digital timer controlled recirculation loop to prevent the dreaded "cold water sandwich" you can get with tankless water heaters...the solar grid-connected PVC array will consist of 20 Schuco Monocrystalline 210 panels (4.2kW) and a SunnyBoy inverter mounted on a true south oriented garage roof...

We will begin to look at each of these features as the build progresses, analyzing their benefits and potential assets and seeing how they may complement (and hopefully not compromise) the "system". Stay tuned.