Net-Zero, Primary Residence Homes, Part 4

How do we achieve a Prudent Living, Net-Zero home? Here’s our approach:

1. Keep it simple – There are only two questions worth asking. 
2. What are the facts?
3. What’s in it for me?
4. Avoid complicating conversations about Net-Zero with useless discussions about micro-mathematics, Scientific R-values vs Builder R-values, charts and graphs that show every cause and effect for every kind of intrusion of cold and heat, philosophies or personal preferences on windows and insulation types and political bias toward Renewable Energy in general.  So let’s cut through all that and simply give you the answer’s you are looking for:
5. At Prudent Living, we know that a 2000 square foot Net-Zero home will cost approximately $40K +- more than a house that is built to minimum energy code standards.  Emphasize “plus or minus”.
6. At Energy Costs of $5,000/year for a minimum code house,  all 40K will have been returned to you in 8 years.  It’s very simple math.   And guess what, you get it back again in another 8 years.  You get it back again…and again.  See what’s happening?  Now just suppose energy costs increase on the minimum energy code built home by 5 % each year.  How does that affect you?  It doesn’t in a negative way. But there are many positives. For starters, you can be at peace knowing that you make all your own energy.  You also benefit by not even having to earn extra money to pay for your energy bills. You can live on much less per year.  Chances are if you write a check for $5,000.00, you would likely have to earn close to $7,000.00 to do it because of everything that gets taken out of your paycheck.  This is great news for people on fixed incomes. 

A Prudent Living Net-Zero Home can be achieved with almost any architectural theme.  That’s a great thing to know. There’s no law that forces your house design to look a certain way or strictly adhere to one architectural theme. That’s because Net-Zero is more about performance than architecture. As a custom builder, however, I can say that something beautiful happens when the two get friendly, shake hands and work together.  Some Net-Zero techniques can squeeze those sacred spaces a little more than you think.

Our Net-Zero homes are primarily heated and cooled using either Geothermal or Mini-Split Heat Pump technology. Domestic hot water is provided by Electric Hybrid Water Heaters and often have a manually controlled backup electric water heater for those rare times when demand exceeds what a hybrid can produce. This is done with a lighted switch that alerts the owner that the backup electric water heater is running.  After hot water demands are satisfied and life returns to normal, the lighted switch is turned off and the Hybrid assumes command. 

Lighting is mostly LED but we still break a few rules in special situations. All Appliances are  Energy Star Rated.

R-Values for thermal performances vary slightly according to preference of types of foundations and wall and roof systems, but we try to hover around R23-30 for the insulated concrete wall, R20 slab edges at Walk-outs and R20-30 underslab with 10mil taped and sealed vapor barrier, R40-45 for exterior walls and R60-90 for the roof. 

Windows can be either double or triple glaze.  I won’t split hairs over this preferential issue because I know that the difference in performance of window openings is minimal in comparison to the R45 wall right next to it.  How ironic is it to argue over an R-value (Converted from U-values) of one or two when the hole you just cut into your R45 wall pretty much neutralized the performance of the wall?  This kind of reasoning reminds me of a beautiful equestrian center and carriage house that we built a long time ago. Everything inside that building had the most expensive of products. There was brass and ironwork, vintage beadboard walls and ceilings and handmade doors throughout. Outside, we installed a beautiful bronze colored metal roof that blended perfectly with the antique red color of the exterior siding.  But I guess things were just going too well to leave things alone.  One day, the architect decided that the barn needed a cupola. He wasn’t thinking of just any standard cupola either. He wanted this cupola to be unique. It needed to stand very tall and have a steep pointed roof with multiple giant hand-crafted louvered vents on all four sides.  The trouble is that this barn was on a ridgeline and when the Summer storms arrived, the rains came down so hard it went up the roof and the wind blew so hard the rain went sideways straight though the cupola ruining all the ceilings below.  Our beautiful and perfect roof had a 10 foot square hole chopped right into the center of it nobody could understand why the builder (me), couldn’t keep it from leaking. 

Windows can be a lot like cupolas when we compare the performance of R-values of thin glass that separates us from the 100 degree differentials in temperatures that can occur between inside and outside panes and that incredible R45 wall that surrounds it.  My advice when discussing windows and their performance is “Just make sure they are well built, ask if broken replacements are easy to get, and then just buy the windows you want!”   Some will insist on Triple-Glaze only. Others, like myself, are just fine using Double Glaze High Performance Windows. Once they’re installed, I doubt you’d ever think about them again.

Air barriers matter.  They must be continuous and un-interrupted and we have our favorite ways of doing it.  People often ask me if a house needs to breathe.  I’ve never really known how to answer except “Breath what?”.

So now we know the size and performance of our foundation, walls, roofs and windows.  It’s time to calculate heating and cooling loads.  They won’t be much.  After that, it’s time to size your Solar PV System. 

Once the heat and cooling loads are added  to all the other electrical loads and we can tally up, you might be surprised that we will not recommend sizing your Solar PV system to match the total.  We to stay slightly under our calculations and design it with the option of adding more Solar PV panels after a year or two of getting used to living in the home and understanding how to operate within it as efficiently as possible. 

There’s no financial justification for over-sizing a Solar PV system.  Remember that I told you that there is no offer of financial compensation from the Utility Companies if you make more electricity than you consume. So, finding that perfect sweet spot is a challenge and it may take a couple tweeks to do it.  The logic behind the effort, however, is to creep up the size of the Solar PV System rather than over size it.