Insulating our way to Net-Zero: Loose-Fill Cellulose

The last piece of the insulation puzzle is wet-spray cellulose's "poor relative", loose-fill cellulose. Loose-fill cellulose is made of up to 85% recycled paper and is sprayed dry with air, providing an R-value of 3.8 and blocking air leakage. Less expensive than both Icynene and wet-spray cellulose, our builder used it primarily in accessible, flat areas, sometimes using netting to hold it in place or offer support.

And the last piece of the insulation puzzle, would be fiberglass. To quote our builder, "in the inside walls for inexpensive sound insulation, that is the only place you will find fiberglass in one of my homes." He exaggerated a little, as he also used it (CertainTeed DRYRight) in the outside eaves, to form a barrier to spray the cellulose against. His opinion is that fiberglass is poorly suited to do its primary job, to provide insulation and to prevent air infiltration. To accomplish these tasks, the fiberglass must be installed perfectly, fitted precisely into all the nooks and crannies and sealed consistently around each and every opening and penetration. This is very time-consuming, labor intensive and challenging, as anyone who has attempted to apply fiberglass batt insulation can attest. It also tends to lose R-value across time and offers minimal thermal mass.

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.

Insulating our way to Net-Zero: Wet Spray Cellulose

Our builder put a lot of thought into deciding what insulation to put where, balancing effectiveness against cost. One of his favorite products is wet-spray cellulose insulation, in this case from Applegate Insulation, a product that requires one fifth of the energy needed to produce an equivalent amount of fiberglass. Made from 85% recycled paper content, largely newspaper, and treated for fire and mold resistance with borate and with a dry adhesive, it is sprayed under pressure into the cavity with a small amount of water, completely filling all the nooks and crannies, reducing the flow of heat and virtually eliminating air infiltration. After completely filling the cavity, a rotating stud scrubber brush is run over the area, leveling it even with the tops of the studs. The cellulose will dry over the next 24 hours, becoming firmer to the touch. No dangerous outgassing is involved, as it does not contain any formaldehyde or respirable microscopic fibers.

The finished surface is quite smooth and spongy to the touch, and the 3.5" of cellulose provides an R-value of 13.3, which when added to the R-3 of the SIS (Dow Structural Insulated Sheathing) on the outside, results in an overall stable R-value of 16.3 for the walls. Our builder believes that the superior air sealing power and the added thermal mass provided by the wet spray cellulose make that R-value a conservative estimate. It is notable that contrary to initial impressions, wet spray cellulose is quite fire retardant, a result of both the fire retardants applied to the paper and its heavy oxygen-limiting density, providing up to a 50% increase in fire resistance. It is also a very good product with respect to air quality, as indicated by the American Lung Association of Virginia choosing to use it in it's Breathe Easy headquarters.

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.

Net Zero Energy Virginia Home and best practices...

As you tighten the envelope of the home, control of moisture becomes much more important, and standard practices become too low a target. the last thing you want is to have your tight envelope trapping wayward water. The dark material you see here coming up behind the brick is 30lb felt underlayment. Although the SIS already forms a vapor barrier, our builder, Mark Waring, prefers the redundancy of additionally installing the felt on top of the SIS.

The green material you see is GreenGuard® RainDrop® Housewrap.
RainDrop’s innovative drainage channels keep water out of the wall system. The channels won’t crimp, collapse, or flatten, ensuring water will drain no matter how tightly cladding is nailed to the wall. Because it’s not perforated, RainDrop resists air and water infiltration. Plus it breathes to allow moisture vapor to escape. With its high tear resistance and translucent design, installation is quick and easy with no job site waste. And it stays UV-stable up to 4 months. RainDrop is an ideal secondary weather barrier for fiber cement, vinyl, foam-backed vinyl, and wood sidings and meets the National, Standard, Uniform and International Building Code requirements for air barriers, moisture protection barriers and weather-resistive barriers. It is used on top of the SIS and behind any of the areas to be covered with shingling.

The window to a zero energy home, Richmond, VA style...

When it came to window choices, there was a lot to consider, because as you increase the tightness and the insulation level of your home, the glazing makes a greater impact on energy usage. And our particular home design has a lot of windows! Looking to the Efficient Windows Collaborative (EWC) for guidance, the 2009 Energy Star standards for Virginia suggested windows with a U-factor (the rate of non-solar heat loss or gain
through a whole window assembly) of .40 and a SHGC (the Solar Heat Gain Coefficient is the fraction of incident solar radiation admitted through a window) of <.40. But our EarthCraft builder reminded us that the EnergyStar standards were going to be tightened starting in 2010, so we set out in search of better windows. The new Virginia Energy Star standards are a U-factor of .32 and a SHGC of <.40, but few suppliers had windows available reflecting the new values yet. After some creative searching, Mark found us PlyGem MW Pro Series windows with a U-factor of .29 and SHGC of .25 for only $400 more than 2009 rated windows. These are vinyl clad PVC construction, 20 year, double pane, argon gas-filled, low-E glass windows with a Warm Edge technology ( the Warm Edge glass spacer system reduces thermal transfer around the glass perimeter by utilizing a unique U-shaped channel to separate glass panes and interrupt the natural flow of heat to cold). Hopefully the added insulation they provide will reduce the load on our geothermal HVAC system. We are hoping that the lower SHGC will work well, as we have a lot of southeast facing glazing on the back of our house, which because of solar sighting, has little shade in the summer, making excess heat gain in hot muggy Virginia a potential problem. Oh, and that door you see there, that is the Therma-Tru Classic-Craft® Mahogany(waiting to be stained) fiberglass front door, which is also EnergyStar rated. Have to have all the portals covered...

Solar PV arrives at the Virginia zero energy home!

Every zero energy home needs a renewable power source and ours consists of 20 Schuco SPV 210 panels supplied by Dereck McAvoy of Midsouth Building Supply. These monocrystalline panels are some of the more efficient ones available, rated at PTC/STC 91.5%, indicating that they in effect, under real world conditions, produce very close to their advertised power rating. They are warrantied to produce at least 80% of their initial output for 25 years. They are on the List of Eligible SB1 Guidelines CompliantPhotovoltaic Modules for the Go Solar California program, one of the longest established and most respected state solar programs. They were installed on the back face of the south facing garage by SunFlower Solar and connected to a SMA Inverter SB 5000us attached to the inside wall of the garage, that wirelessly sends production data to my laptop. The inverter, warrantied for 10 years, converts the DC output to AC and feeds it to the house with the excess going back into the Virginia Power grid with the help of a grid-tie connection to their net metering program. This program allows two way metering, so that excess power can flow into the grid, and needed power (ie. at night) can be drawn out. The arithmetic sum is carried over a 12 month period. If you produce excess power it can be carried forward; if you fall short, it can be subtracted from that sum (or you pay a bill). Any excess that is not used in a 12 month period is donated to the grid, and you get warm fuzzy feelings for your kindness to humanity. All of this now sounds very simple, and the panels look neat and clean. Let me tell you, pulling this together was not simple, neat or clean. It took many hours of active research, several false starts, a motivated, thoughtful builder, and several solar resource experts to make this happen. More on this later.