Builder: Certified Living, Inc.Sponsor: Captain Planet Foundation

1,700 sq. ft. home with 2 bedrooms, 2 bathand a loft

Key Features• Photovoltaic system• Solar hot water heating• Passive solar design• Ducts in conditioned space• Controlled ventilation• High performance envelope, windows and an

integrated HVAC system• Advanced framing with structural insulated panels (SIPs)

Y ou may have heard of Zero

Energy Homes—energy self-sufficient, solar-powered homes; homeswithout utility bills, or nearly so. But you look at the utility bills foryour own home and the cost of solar energy systems, and youwonder just how this can work. There are four essential ingredientsto making a Zero Energy Home work:

• The Zero Energy Home is primarily powered by photovoltaicand solar hot water systems, both likely mounted on the roof.

• The Zero Energy Home is so efficient—as much as 90% moreefficient than the average home—that demand for power canbe met, or nearly met, with readily available and reasonably sizedsolar power systems.

• The Zero Energy Home always needs a back-up—some energyfrom the grid in the case of the Cottage—to deal with times whenthe weather and the big energy demands (space heating or cool-ing, water heating, and refrigeration) combine and conspire.

• The fourth ingredient is you. To tread this lightly on the landrequires that you are a part of the system, tuning your energy useto complement rather than stress the Zero Energy Home. Thisdoes not mean thermal privation or hand-cranking your radio—it means learning a lot about how your home works, occasion-ally outwitting the big energy demands, and maybe expandingyour comfort zone just a bit.

So, the trick is to stock your roof with panels; your home with themost efficient and integrated exterior envelope, HVAC system, waterheater, appliances, and lighting available; and your family with zeroenergy savvy. You will have to do all three. Here is what it takes todo each.

The Ultra-Efficient Home Performance Although most peopleassociate the term zero energy with solar panels, the starting pointmust always be the efficiency of the structure and its heating/ven-tilation/air conditioning (HVAC) system. The way to really fine-tunethe energy performance of a home is to treat the structure and theHVAC system as integrated systems, matching their features andindividual contributions to the whole.

1.The exterior walls, floors, roof, and windows – These are all ofthe components of the exterior envelope. How much they resistheat conduction (their R-value), how airtight they are, and howthey are oriented with respect to the sun and prevailing winds(particularly windows) all are major determinants of energy per-formance. The home design, the materials selected, and the qual-ity of installation must work together to achieve maximum effi-ciency. A key component of the Captain Planet Cottage is theStructural Insulated Panels—or SIPs—used for the roof, floor,and walls. SIPs are typically made using expanded polystyrene(EPS), or polyisocyanurate rigid foam insulation sandwiched be-tween two structural skins of oriented strand board (OSB). Theresult is a building system that is very strong, predictable, en-ergy- efficient and cost-effective. Their superior R-value and airtightness are essential to the high performance of the Cottage.

The Captain Planet Cottage is designed for passivesolar heating and cool-ing. Key elements include:• home layout and orien-tation;

South Elevation

North Elevation

East Elevation

West Elevation

U.S. Depar tment of Energy

P r o g r a m P a r t n e r

Captain PlanetZero EnergySIPS Cottage

Atlanta, Georgia

www.buildingscience.com

Captain Planet Zero Energy SIPS Cottage

Zero Energy Homes Powered by Solar & Efficiency

SIP homes use ZERO energy when combined with solar

Lower heating bills translates to lower energy (fossil fuel)consumption and greenhouse gas emissions

ORNL study shows air leakage for SIPs is almost 15 timesless than for typical wood frame construction

www.captainplanetfdn.org

Section throughEast-West Elevation

• location, placement, number, and operability of windows;

• strategic employment of retractable porch awnings and thermalwindow shades;

• high ceilings and deep wrap-around porches

• highly reflective white standing seam metal roof cladding.

These all work to capture the most sun in the winter, and providethe most shading and natural ventilation in the summer.

2.The HVAC system – Building a high-performance structure al-lows you to really fine tune or “right-size” your space heating andcooling unit, your fresh-air ventilation, and the ducts that deliverall three. Essential elements to the Cottage include a variable-speed ECM air handler, a two-stage 12 – 13 SEER AC unit, and ascheduled intermittent fresh air ventilation system that also pro-vides mixing of all interior air. Mechanical ventilation, you say?You can’t build a home this tight and not purposefully introducethe fresh air you and your family need. And for the Cottage, oc-casional space heating needs that cannot be met by passive solargain are supplied by the high-efficiency, direct-vent gas fireplaceand distributed throughout the cottage by the mechanical venti-lation system.

3.Water heating – After your HVAC system, water heating makesup the largest single energy demand in the home. Solar waterheating (described below) is an essential part of any zeroenergy strategy, but you always need a back-up. While thereare several options to consider—combo systems (combining wa-ter and space heating), heat pump water heaters, instantaneoussystems—the Captain Planet Cottage simply has the top-of-the-line electric tank water heater. It does the best job of storing ther-mal capacity from the panels while relying primarily on the sub-stantial PV capacity of the Cottage.

4.Lighting and appliances – Once the energy performance of thestructure, the HVAC, and water heating have been optimized,“plug loads” become the next target for significant energy im-provements. It begins with the big boys—the refrigerator and light-ing—and reaches down to the dishwasher, dryer, and householditems such as the television and microwave. The higher perfor-mance of many of these items also reduces air conditioning needsin climates with any cooling period.

The Photovoltaic System To turn sunlight into household electric-ity requires:• panels - to collect the solar energy and convert it into direct cur-

rent (DC) electricity.

• an inverter - to convert the DC into alternating current (AC),matching your home’s conventional electrical system.

• a controller – to manage where the solar and grid-supplied powergo, to or from your house and the grid.

Over the past few years, each of these components has been rap-idly evolving and improving so that today they are compatible, code-compliant, and cost-effective. Lots of work has been done to bringthe efficiency of the panels up and their cost down, and to link thepanels into system packages so that you don’t have to build thesystem. And in many states (and maybe the whole country withresidential energy efficiency legislation pending in Congress),rebates and tax incentives exist to subsidize solar equipment in-vestment.

Section throughKitchen at Mechanical Closet

For the Captain Planet demonstration cottage of 1,700 square feetwith a family of four, a 4-kilowatt system with eight 7-foot by 6-foot panels will supply nearly all of the home’s electrical needs.Like most PV systems, the Captain Planet PV system costs about$6 per watt. But the system will continue generating power withlittle to no replacement for many years.

The Solar Hot Water System To turn sunlight into hot water requires:

1.roof panel(s) – essentially box “greenhouses” containing highlyabsorbent piping and faced withdouble-glazing that lets light in yettraps significant heat energy forthe piping to capture.

2.transfer piping – this carries theliquid heated in the panels (eitherpure water in direct systems or acoolant/water mix in indirect sys-tems) down to either a storagetank or the water heater tank (di-rect system) or to a heat exchanger(indirect system).

3.tank – since the sun does not al-ways shine, solar heated watermust be stored and the volumeand insulation of this tank must bematched to the capacity of theroof panel(s).

In the Captain Planet Cottage, one4’ x 8’ collector at peak efficiency(when the sun in a cloudless sky isshining directly over the panels) sup-plies most of the hot water for a fam-ily of four’s daily needs (bathing,clothes and dish washing).

The Zero Energy Home OwnerYou can’t fine-tune the energy per-formance of a home like this with-out being a smart home operatorand maintainer. You will determine whether the term “grid back-up” is spelled with a lower or upper case “g.” You will determinehow often your meter runs forward (you pay them) or backward(they pay you) as part of net metering. Here are some of the“little” things that will help determine just how close to Zero En-ergy your home can be:

• Use your windows, insulated window shades, and retractableporch awnings for best cooling and heating effect.

• Manage your hot water needs—showering, clothes anddishwashing—to coincide with peak solar performance.

• Treat all electrical use—ceiling fans, lighting, TV, computers—astask-oriented: on when used, off when not.

• Manage daily household activities for maximum heating andcooling benefit during extreme outdoor conditions—microwaveuse instead of stovetop cooking and baking in the summer, orexercise routines in the winter.

Follow home component maintenance schedules religiously.

This home is designed for the maximum

reduction in energy and resource

consumption, yet still provide for

safe, affordable, comfortable,

aesthetically pleasing shelter.

A Word on Durability

We have a nickname for the Captain Planet ZeroEnergy Cottage—the “double-naught” Cottage.The second zero stands for its tiny footprint interms of materials use. This home is engineeredfor optimal use of materials and durability. Fromthe wrap-around porches to the standing-seamaluminum roof, this Cottage has been designedand commissioned with components and systemsfor outstanding service life. The motto for the“double-naught” Cottage is “zero is more, longis less.”

U.S. Depar tment of Energy

P r o g r a m P a r t n e r

Captain Planet Zero Energy SIPS Cottage (ZE)Home Owner: Mastering Light and Air

Most people find the open and airydesign of the ZE Cottage really ap-pealing. Well, the Cottage is actuallymore than just a “pretty face”—it’sdesign is a perfect example of formmeets function. Here’s how:

• The “L” design With theright mix of windows, the“L” design is the mosteffective way to getdaylight in andnatural ventila-tion throughevery roomin the home.The ZE Cot-tage will be a realmiser on lights andcooling as a result. Forwindows not sheltered by aporch, the ZE homeowner willhave to find the right combinationof window treatments to balancedirect and indirect lighting, air flow,and summer shading.

• The cathedral ceiling, loftdormers, and porchesEveryone knows that hot air rises(hot air is less dense than coolerair). The ZE Cottage’s high ceilingstake advantage of this “stack ef-fect,” and the loft window dormersact as “chimneys” for exhausting

the hot air. The result is cooler airbeing pulled in off the large shel-tered porches. How do we knowthat all these features will worktogether like this? The answercomes from homes built 100 yearsago, before artificial lighting andmechanical heating and cooling.

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ZE home owner only notices…comfort.

• “Form meets function”ceiling fans If you look closelyat the ceiling fans in the ZE Cot-tage, you will notice a graceful

twist to their blades—aren’tceiling fan blades usually

just flat paddles? You’reright, but not in the

ZE Cottage. Theblades are bent

like a pro-pellerblade,

moving airnearly 50% more

efficiently thanconventional flat fan

blades (they are muchquieter and less prone to

wobble than conventional bladesas well). These ceiling fans are theonly ones currently on the marketthat deliver air flow efficiently, witha dimmable fluorescent light, with aprogram-mableremotecontrol.You canprogramthe fanon a timer or to a temperature, sothat the fan only spins for occupantcomfort. Most ceiling fans runlonger than necessary for occupantcomfort or run when no one is inthe room, when the only result iswasted energy and the ceiling fanmotor heating, not cooling the air!

Isn’t it great to have ahome that works as well

as it looks?

• The mechanical ventila-tion system Our fresh air needsdon’t go away during the height ofsummer and winter, when ourhomes are closed up. Many homestoday count on random air infiltra-tion through a leaky building enve-lope under summer and winterconditions—a big mistake. Thisaccidental air could hardly be calledfresh; it can be laden with humidity,dust, building material fibers, etc.The ZE Cottage pulls in just theright amount of outdoor air througha dedicated duct from a consciouslylocated external port. This fresh airis then filtered and mixed withcirculating indoor air, tempering it’stemperature difference so that the

OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSOFFICE OF ENERGY EFFICIENCY AND RENEWABLE ENERGYU.S. DEPARTMENT OF ENERGY

Captain Planet Zero Energy SIPS Cottage (ZE)Home Owner: Mastering Power Demands

1A British thermal unit (Btu) is the amount of heat energy it

takes to raise the temperature of one pound of water by one

degree Fahrenheit (at sea level). As an example, it takes

about 2,000 Btus to make a pot of coffee.

3A note of caution: thermal window curtains can NOTbe used to keep summer sun out during the day because verywarm even hot air is trapped between the shade and glazing,possibly creating temperatures high enough to damage thesealed multi-paned glazing units.

2A watt is the basic unit of electrical power. As an example, ifyou took two 2-liter plastic bottle of soda, one in each arm,and lifted it up three feet in one second over and over again,you would spending the same amount of power as a 40-watt

light bulb—tough way to read a book, huh?

We are so accustomed to ready, virtu-ally unlimited power that most of usdon’t know just how much it takes topower our homes and all their conve-niences. ZE home owners must be stu-dents of the Btu1 and the watt2 .

Managing the Btu We use Btusto talk about heating (welcoming oradding Btus) and cooling (keeping ortaking out Btus) the building. A ZE homeowner negotiates Btus with the sun first,the gas or oil man second. During theheating season, the ZE home and ownertake advantage of the way the home isdesigned, positioned, and operated tobring as much sun (a free source of Btus)into the building as possible:

• Overhangs and windows– both with dimen-sions and locationsto admit low-anglewinter sun.

• Awnings andthermal shades –opened or pulledup to admit low-angle winter sunduring the day with ther-mal window shades closed to retainBtus at night.

During the cooling season, the ZE homeand owner take the opposite approach,keeping out as much direct sun (btus) aspossible:

• Overhangs and windows – dimensionsand locations keep out high-angledirect sun.

• Awnings and solar screens – Retract-able awnings fully extended to shadewalls and windows; solar screens onwindow to shade without undulyrestricting viewing.3

• Operable windows and ceiling fans –Relative humidity permitting, free orreally cheap cooling can be had bymoving air through the building andaround occupants.

Lastly, a high-efficiency gas furnace/fireplace provides Btus or supplementalheating during the heating season, withthe mechanical ventilation system distrib-uting this heat throughout the house. TheZE home high-efficiency air conditioningsystem provides supplemental cooling

and dehumidification for comfort when abreeze from windows and ceiling fansjust can’t cut it. Both the two-stage com-pressor and variable-speed, electrically-commutated (ECM) air handler motor aredesigned for peak efficiency and maxi-mum removal of vapor (latent load) frominterior air. Both the furnace and the A/Care controlled by a smart, programmablethermostat, further boosting the HVACsystem’s efficiency.

Managing the watt We use thewatt to talk about electrical power. Beingwatt-wise is how the ZE home and home-owner can really shine, or fade, primarilyfor two reasons:

1The ZE home’s solar systems—thePV and solar water panels—

ONLY negotiate with the shin-ing sun. Without any batterystorage and only limited hotwater tank storage, the ZEhomeowner must matchtimely supply with timelydemand for watts.

2Moving Btus with watts—heating or cooling with electric-

ity—takes a LOT of power. Anyelectrical appliance or home conve-nience that heats—a toaster, ahair dryer—or cools—pri-marily the refrigerator—will require the most“watt” diligence.

So, the ZE home ownerneeds to use the followinginformation about types andsources of demand for wattsto maximize business withthe ZE home’s solar systemsand minimize (at least incom-ing) business with the utility.Remember that there are threeaspects of any electrical fixture thatare important in managing watts—how much power it draws, how long itoperates each day, and when it operateseach day.

Use these guidelines with thetable to the right to manage householdenergy use:

• Make hay—or coffee or cleanclothes or toast—while the sunshines. As much as possible, pace use

of significant watt gobblers with yourPV system’s production.

• Capitalize on your investment in yourZE home with high-efficiency appli-ances. Use the table below to decideon which items you will get the best

return. Use the EPA En-ergy Star label as a guide.

• Consider every electrical use as atask—on when in use, off when not.This goes for just about everything—lighting, fans, entertainment equip-ment. As the table shows, they all candraw lots of watts.

• Use fluorescent fixtures and bulbs—the quality and availability has andcontinues to improve—use the EPAEnergy Star label as a guide.

• Watch your “vampire” loads—devicesthat use energy while plugged in butnot functioning. These loads canreally add up, particularly for thosedevices with step-down transformers(adapters) and devices with built-inclocks.

• During the cooling season, managewatts for Btu production, those appli-ances or fixtures that create heat.

U.S. Depar tment of Energy

P r o g r a m P a r t n e r

For a copy of this document,please go to our website:

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ap

pli

ance watts usedcoffee maker .............. 900—1,200

clothes washer ..................... 350—500clothes dryer ........................ 1,800—5,000

dishwasher............................... 1,200—2,400(using the drying feature greatly increases energy consumption)

ceiling fan ............................................... 65-175hair dryer .................................... 1,200—1,875clothes iron ................................ 1,000—1,800

microwave oven ......................... 750—1,100Personal computer:

CPU (awake) ...................................... 120monitor (awake) .............................. 150radio (stereo) .................................. 400 refrigerator (16 ft3 frostfree) ............................ 725 27” television .............................113 toaster ........................... 800—1,400 vacuum cleaner......... 1,000—1,400 water pump (deep well) ........250—1,100

OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSOFFICE OF ENERGY EFFICIENCY AND RENEWABLE ENERGYU.S. DEPARTMENT OF ENERGY

entire year, depending on the patterns andnature of energy use by its occupants. And hereis the really neat part—managing their energyuses is pretty much all that ZE owners need todo—the PV system is virtually maintenance-free during its 20+ years of expected operation.

Solar water panel Solar water panel Solar water panel Solar water panel Solar water panel All solar waterheaters have the following components:

• an open-faced roof-mounted box with adark, highly absorptive inside surface;

• a glass top face that permits sunlight to passinto the box but is relatively reflective tothe heat energy into which the sunlight isconverted inside the box (like a

greenhouse);

• highly conductive piping inside the box,filled with a fluid that can pick up a signifi-cant portion of the heat energy trapped inthe box;

• insulated piping that carries the heated fluiddown into the building, for hot water use orheat exchange to water for use.

There are two ways of classifying the majordifferences among solar water systems—activeversus passive and closed-loop versus open-loop. Active systems all have pumps controlledby a thermostat that move fluid through thesystem. Passive systems have no pumps; theyrely upon either thermo-siphoning or densitydifferences brought on by temperature to movefluid through the system. Closed-loop systemshave two loops—one loop goes to the solarcollector and contains a fluid (generally awater-antifreeze mix) that transfers heat wellbut has a very low freezing point. This fluidexchanges its heat content with potable waterin a separate loop. Open-loop systems haveonly one loop of potable water.

Generally, active and closed-loop systems havesignificantly higher efficiencies and can beused in climates with freezing conditions.Many passive and/or open-loop systems areonly appropriate for areas with no or onlyoccasional mild freeze conditions. Passive andopen-loop systems are less complicated andhence less expensive. But open-loop systemsare very dependent on high-quality water forefficient operation and reasonable service life.Closed-loop systems must have either a drain-back or warm water trickle feature to deal withfreeze conditions, but much depends on the

South elevation in winter with awnings retracted

Chargecontroller

DC Loads

Inverter AC Loads

To UtilityCompany

Captain Planet Zero Energy SIPS CottageSchematic Diagram of the

Solar Energy Systems

Insulated pipe

Coldin

Hot outHot out

Domestichot watertank

Just about the entire roof area on the southside of the ZE Cottage is stocked with solarpanels, 40 photo-voltaic and one solar water tobe exact. The renewable energy system in-stalled by Big Frog Mountain Corporationconsists of photo-voltaic panels from Ever-green Solar. The panels are mounted usingUnirac’s mounting system and metal roofclamps by S-5!. The DC current generated bythe panels is converted to utility-grade 120volts (household current by the multimodeinverter built by Advanced Energy Inc.). Thesystem is designed to turn the utility meterbackwards during the day. The system is on thesouth side because this gets the most direct solarexposure year round. Here is how it works:

Photo-voltaic (PV) panelsPhoto-voltaic (PV) panelsPhoto-voltaic (PV) panelsPhoto-voltaic (PV) panelsPhoto-voltaic (PV) panelsPV panels turn a portion of the sunlight (photo)they receive into electricity (voltaic). PV orsolar cells are made up of silicon wafers, onelayer “doped” with a substance that tends togive up electrons when excited by incomingphotons (solar energy units) and another layerdoped with a substance that tends to take onexcited electrons (the silicon crystal base is agreat background for this exchange of electronsbecause silicon atoms tend to loosely share lotsof electrons in this crystal structure). Andwhenever you create a flow of electrons, youget electricity.

The tricks to making solar cells for everydayuse have been developing the technology tomass produce cells (even before “mass” de-mand exists), developing the technology toboost how much sunlight they can convert intoelectrical current, and developing the technol-ogy to support safe and efficient integrationinto existing electrical systems.

The ZE PV system has two other importantmajor components besides the array of fortypanels—an inverter and a controller. A longtime ago, for a variety of reasons related tomaterials, safety, and transmission issues, wedecided to run buildings, including homes, onalternating current (AC). But the PV panelsproduce direct current (DC). The inverterchanges the DC into AC current compatiblewith household electrical systems. The lastcomponent, the controller, controls the flow ofenergy from the panels, to the house, and toand from the utility power lines. An importantpart of the controller’s job is to prevent currentfrom entering the line when utility linemanhave interrupted the utility supply for linemaintenance or repair.

The size or capacity of PV systems is generallyexpressed in terms of watts or kilowatts gener-ated under peak or ideal conditions. The ZE PVsystem is capable of generating about 10 wattsper square foot of panel, for a total of 4,000watts or 4 kilowatts. Given the efficiency of theCottage’s building envelope, its HVAC system,and appliances, 4kW will more than meet thetotal annual demand over the course of an

U.S. Depar tment of Energy

P r o g r a m P a r t n e r

Captain Planet Zero Energy (ZE) Home Owner:Mastering Solar Energy Systems

specific installation and length of exposedtransfer piping.

The ZE Cottage CopperSun system is a passiveopen-loop system—no pumps, no movingparts, no valves, no controller. This is a verysimple yet sophisticated solar water systemwith a good track record in the field. This 4 by8 panel has been custom-made to be orientedup and down the shed roof of the dormerwindow on the south elevation of the ZE roof.The hot water from the roof panel circulates tothe standard 50-gallon storage tank of theelectric waterheater,

basically keep-ing the electricelements of thewater heater off or working less. The ZEhomeowner will only know the panel is work-ing by looking at the paltry electric bill.

This solar panel will supply most of the hotwater needs for a family of four, depending onweather and the hot water use of the occupants.Anyone can save money with this unit, but theZE home owner that times major hot water useto the late afternoon/early evening peak pro-duction period of the system will be the realwinner.

The CopperSun is designed for temperateclimates with limited freeze potential. It is ratedfor 20˚ F for an 18 hour period. The two freezeprotection systems required by the Solar RatingCertification Corporation are the high mass 4-inch tubes and the drain down system for raretimes in the Atlanta climate when conditionscould exceed the rated conditions.

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Many PV systemshave batteries for

storing electricity when PVsupply is greater than house-

hold demand. PV battery sys-tems are currently still very

expensive and not particularlylong-lived. While batteries arenearly essential for off-the-gridsystems, they are not a part of theZE Cottage grid-tied system. Manyoff-the-grid PV systems also have aback-up generator, which runs tosupply household demand for

extensive periods of badweather and/or to periodi-

cally top off the batterycharge.

OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSOFFICE OF ENERGY EFFICIENCY AND RENEWABLE ENERGYU.S. DEPARTMENT OF ENERGY