OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY

Buildings forthe 21st CenturyBuildings that are moreenergy efficient, comfortable,and affordable...that’s thegoal of DOE’s Office of BuildingTechnology, State andCommunity Programs (BTS).To accelerate the developmentand wide application of energyefficiency measures, BTS:• Conducts R&D on technologies

and concepts for energy efficiency, working closely withthe building industry and withmanufacturers of materials,equipment, and appliances

• Promotes energy/money

saving opportunities to bothbuilders and buyers of homesand commercial buildings

• Works with state and local

regulatory groups to improvebuilding codes, appliancestandards, and guidelines forefficient energy use

• Provides support and grants

to states and communitiesfor deployment of energyefficient technologies andpractices

DESIGN WITH THE SUN IN MINDSunlight can provide ample heat, light, andshade and induce summertime ventilation intothe well-designed home. Passive solar designcan reduce heating and cooling energy bills,increase spatial vitality, and improve comfort.Inherently flexible passive solar design principlestypically accrue energy benefits with low maintenance risks over the life of the building.DESIGN TECHNIQUESPassive solar design integrates a combinationof building features to reduce or even eliminatethe need for mechanical cooling and heatingand daytime artificial lighting. Designers andbuilders pay particular attention to the sun tominimize heating and cooling needs. Thedesign does not need to be complex, but itdoes involve knowledge of solar geometry,window technology, and local climate. Giventhe proper building site, virtually any type ofarchitecture can integrate passive solar design.Passive solar heating techniques generally fallinto one of three categories: direct gain,indirect gain, and isolated gain. Direct gain issolar radiation that directly penetrates and isstored in the living space. Indirect gain collects,stores, and distributes solar radiation usingsome thermal storage material (e.g., Trombéwall). Conduction, radiation, or convection thentransfers the energy indoors. Isolated gainsystems (e.g., sunspace) collect solar radiationin an area that can be selectively closed off oropened to the rest of the house.Passive solar design is not new. In fact, ancientcivilizations used passive solar design. What isnew are building materials, methods, and

SOLAR POSITIONING CONSIDERATIONSThe south side of the home must beoriented to within 30 degrees of duesouth.

SUMMER

WINTER

software that can improve the design andintegration of passive solar principles intomodern residential structures.COSTIt takes more thought to design with the sun;however, passive solar features such asadditional glazing, added thermal mass, largerroof overhangs, or other shading features canpay for themselves. Since passive solar designsrequire substantially less mechanical heatingand cooling capacity, savings can accrue fromreduced unit size, installation, operation, andmaintenance costs. Passive solar designtechniques may therefore have a higher firstcost but are often less expensive when thelower annual energy and maintenance costs arefactored in over the life of the building.

00 pm

ters south-facing windows and

hermal mass inside the home. The

converted to heat energy, which heats

 and thermal mass materials. On

 days, solar heat maintains comfort

mid-morning to late afternoon periods.

00 pm

sets, it stops supplying heat to the

wever, a substantial amount of heat

ored in the thermal mass. These

lease the heat slowly into the passive

s, keeping them comfortable on most

ings. If temperatures fall below the

el, supplemental heat is needed.

30 am

owner sets the thermostat back at

nly minimal back-up heating is

ergy-efficient features in the home

eat losses to the outside.

00 am

rly morning hours are the toughest

solar heating systems to provide

he thermal mass has usually given up

heat, and the sun has not risen

begin heating the home. During this

ome owner may have to rely on supple

 Energy-efficient features in the home

e need for supplemental heating.
an increase building energy loss.

, including selective coatings, have

y increasing window insulation

at where it is needed.

e the window area on north-, east-,

le still allowing for adequate day

g windows require a high Solar Heat

usually 0.60 or higher—to maximize

0.35 or less) to reduce conductive

sible transmittance (VT) for good

C refers to the portion of incident

 a window, and U-factor indicates

window assembly.

ularly effective strategies include

acing windows along with

facing windows. Shading from

hutters, and solar window screens

windows that receive full sun.

a National Fenestration Rating

 U-factors, SHGC, and VT.

SIZE SOUTH FACING OVERHANGS TO PROPERLYSHADE WINDOWS

“suntempering” orients most of the home’s glazing toward thesouth—a glazing area of up to 7 percent of the building floorarea. Additional south-facing glazing may be included if morethermal mass is built in. Such a shift in window location is agreat strategy for cold climates and costs nothing beyondgood planning. Many passive solar homes are merelysuntempered.

helps shade south-, east-, or west-facing windows fromsummer heat gain. Mature deciduous trees permit most wintersunlight (60 percent or more) to pass through while providingdappled shade throughout summer.Heat Storage. Thermal mass, or materials used to store heat,

is an integral part of most passive solar design. Materials suchas concrete, masonry, wallboard, and even water absorb heatduring sunlit days and slowly release it as temperatures drop.This dampens the effects of outside air temperature changesand moderates indoor temperatures. Although even overcastskies provide solar heating, long periods of little sunshineoften require a back-up heat source. Optimum mass-to-glassratios, depending on climate, may be used to prevent overheating and minimize energy consumption (The Sun’s Joules,

http://solstice.crest.org/renewables/SJ/passive-solar/136.html). Avoid coverings such as carpet that inhibit thermalmass absorption and transfer.Natural Cooling. Apt use of outdoor air often can cool a homewithout need for mechanical cooling, especially when effectiveshading, insulation, window selection, and other means alreadyreduce the cooling load. In many climates, opening windows atnight to flush the house with cooler outdoor air and then closingwindows and shades by day can greatly reduce the need forsupplemental cooling. Cross-ventilation techniques capture cooling, flow-through breezes. Exhausting naturally rising warmer airthrough upper-level openings (stack effect; e.g., clerestorywindows) or fans (e.g., whole-house fan) encourages lower-levelopenings to admit cooler, refreshing, replacement air.Natural Lighting. Sometimes called daylighting, natural lighting refers to reliance on sunlight for daytime interior lighting.Glazing characteristics include high-VT glazing on the east,west, and north facades combined with large, south-facingwindow areas. A daylit room requires, as a general rule, at least5 percent of the room floor area in glazing. Low-emissivity(low-E) coatings can help minimize glare while offering appropriate improved climatic heat gain or loss characteristics.Sloped or horizontal glass (e.g., skylights) admit light but areoften problematic because of unwanted seasonal overheating,radiant heat loss, and assorted other problems.

2

4

5

1

3

40 degrees

80 degrees

8 feet

aaaaa aaaaaaaaaaaaaaaaaaaaaaa

OVERHANG SIZING RULES:1. Draw the wall to be shaded to scale.2. Draw the summer sun angle upward from the

bottom of the glazing.

3. Draw the overhang until it intersects the

summer sun angle line.

4. Draw the line at the winter sun angle from the

bottom edge of the overhang to the wall.

5. Use a solid wall above the line where the winter

sun hits. The portion of the wall below thatline should be glazed.

aaa
an increase building energy loss.

, including selective coatings, have

y increasing window insulation

at where it is needed.

e the window area on north-, east-,

le still allowing for adequate day

g windows require a high Solar Heat

usually 0.60 or higher—to maximize

0.35 or less) to reduce conductive

sible transmittance (VT) for good

C refers to the portion of incident

 a window, and U-factor indicates

window assembly.

ularly effective strategies include

acing windows along with

facing windows. Shading from

hutters, and solar window screens

windows that receive full sun.

a National Fenestration Rating

 U-factors, SHGC, and VT.

SIZE SOUTH FACING OVERHANGS TO PROPERLYSHADE WINDOWS

“suntempering” orients most of the home’s glazing toward thesouth—a glazing area of up to 7 percent of the building floorarea. Additional south-facing glazing may be included if morethermal mass is built in. Such a shift in window location is agreat strategy for cold climates and costs nothing beyondgood planning. Many passive solar homes are merelysuntempered.

helps shade south-, east-, or west-facing windows fromsummer heat gain. Mature deciduous trees permit most wintersunlight (60 percent or more) to pass through while providingdappled shade throughout summer.Heat Storage. Thermal mass, or materials used to store heat,

is an integral part of most passive solar design. Materials suchas concrete, masonry, wallboard, and even water absorb heatduring sunlit days and slowly release it as temperatures drop.This dampens the effects of outside air temperature changesand moderates indoor temperatures. Although even overcastskies provide solar heating, long periods of little sunshineoften require a back-up heat source. Optimum mass-to-glassratios, depending on climate, may be used to prevent overheating and minimize energy consumption (The Sun’s Joules,

http://solstice.crest.org/renewables/SJ/passive-solar/136.html). Avoid coverings such as carpet that inhibit thermalmass absorption and transfer.Natural Cooling. Apt use of outdoor air often can cool a homewithout need for mechanical cooling, especially when effectiveshading, insulation, window selection, and other means alreadyreduce the cooling load. In many climates, opening windows atnight to flush the house with cooler outdoor air and then closingwindows and shades by day can greatly reduce the need forsupplemental cooling. Cross-ventilation techniques capture cooling, flow-through breezes. Exhausting naturally rising warmer airthrough upper-level openings (stack effect; e.g., clerestorywindows) or fans (e.g., whole-house fan) encourages lower-levelopenings to admit cooler, refreshing, replacement air.Natural Lighting. Sometimes called daylighting, natural lighting refers to reliance on sunlight for daytime interior lighting.Glazing characteristics include high-VT glazing on the east,west, and north facades combined with large, south-facingwindow areas. A daylit room requires, as a general rule, at least5 percent of the room floor area in glazing. Low-emissivity(low-E) coatings can help minimize glare while offering appropriate improved climatic heat gain or loss characteristics.Sloped or horizontal glass (e.g., skylights) admit light but areoften problematic because of unwanted seasonal overheating,radiant heat loss, and assorted other problems.

2

4

5

1

3

40 degrees

80 degrees

8 feet

aaaaa aaaaaaaaaaaaaaaaaaaaaaa

OVERHANG SIZING RULES:1. Draw the wall to be shaded to scale.2. Draw the summer sun angle upward from the

bottom of the glazing.

3. Draw the overhang until it intersects the

summer sun angle line.

4. Draw the line at the winter sun angle from the

bottom edge of the overhang to the wall.

5. Use a solid wall above the line where the winter

sun hits. The portion of the wall below thatline should be glazed.

aaa
OFFICE OF BUILDING TECHNOLOGY, STATE AND COMMUNITY PROGRAMSENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY

Buildings forthe 21st CenturyBuildings that are moreenergy efficient, comfortable,and affordable...that’s thegoal of DOE’s Office of BuildingTechnology, State andCommunity Programs (BTS).To accelerate the developmentand wide application of energyefficiency measures, BTS:• Conducts R&D on technologies

and concepts for energy efficiency, working closely withthe building industry and withmanufacturers of materials,equipment, and appliances

• Promotes energy/money

saving opportunities to bothbuilders and buyers of homesand commercial buildings

• Works with state and local

regulatory groups to improvebuilding codes, appliancestandards, and guidelines forefficient energy use

• Provides support and grants

to states and communitiesfor deployment of energyefficient technologies andpractices

DESIGN WITH THE SUN IN MINDSunlight can provide ample heat, light, andshade and induce summertime ventilation intothe well-designed home. Passive solar designcan reduce heating and cooling energy bills,increase spatial vitality, and improve comfort.Inherently flexible passive solar design principlestypically accrue energy benefits with low maintenance risks over the life of the building.DESIGN TECHNIQUESPassive solar design integrates a combinationof building features to reduce or even eliminatethe need for mechanical cooling and heatingand daytime artificial lighting. Designers andbuilders pay particular attention to the sun tominimize heating and cooling needs. Thedesign does not need to be complex, but itdoes involve knowledge of solar geometry,window technology, and local climate. Giventhe proper building site, virtually any type ofarchitecture can integrate passive solar design.Passive solar heating techniques generally fallinto one of three categories: direct gain,indirect gain, and isolated gain. Direct gain issolar radiation that directly penetrates and isstored in the living space. Indirect gain collects,stores, and distributes solar radiation usingsome thermal storage material (e.g., Trombéwall). Conduction, radiation, or convection thentransfers the energy indoors. Isolated gainsystems (e.g., sunspace) collect solar radiationin an area that can be selectively closed off oropened to the rest of the house.Passive solar design is not new. In fact, ancientcivilizations used passive solar design. What isnew are building materials, methods, and

SOLAR POSITIONING CONSIDERATIONSThe south side of the home must beoriented to within 30 degrees of duesouth.

SUMMER

WINTER

software that can improve the design andintegration of passive solar principles intomodern residential structures.COSTIt takes more thought to design with the sun;however, passive solar features such asadditional glazing, added thermal mass, largerroof overhangs, or other shading features canpay for themselves. Since passive solar designsrequire substantially less mechanical heatingand cooling capacity, savings can accrue fromreduced unit size, installation, operation, andmaintenance costs. Passive solar designtechniques may therefore have a higher firstcost but are often less expensive when thelower annual energy and maintenance costs arefactored in over the life of the building.

00 pm

ters south-facing windows and

hermal mass inside the home. The

converted to heat energy, which heats

 and thermal mass materials. On

 days, solar heat maintains comfort

mid-morning to late afternoon periods.

00 pm

sets, it stops supplying heat to the

wever, a substantial amount of heat

ored in the thermal mass. These

lease the heat slowly into the passive

s, keeping them comfortable on most

ings. If temperatures fall below the

el, supplemental heat is needed.

30 am

owner sets the thermostat back at

nly minimal back-up heating is

ergy-efficient features in the home

eat losses to the outside.

00 am

rly morning hours are the toughest

solar heating systems to provide

he thermal mass has usually given up

heat, and the sun has not risen

begin heating the home. During this

ome owner may have to rely on supple

 Energy-efficient features in the home

e need for supplemental heating.