Passive Solar Design

Passive Solar Design:
Make that
beautiful home

feel Beautiful

CCSE Presentation, Copyright 2011 1

Where we want to go
Provide you with the concepts, background, resources and motivation
to integrate passive solar design into your homes—both existing and
future.

2

Roadmap
• What is passive solar?
– Recalling what we forgot

• Why we should do this?
– It’s not just about saving $

• Passive solar fundamentals
– Eating low on the food chain
– 14 principles of passive solar design

• Understanding thermal mass

• Some simulations
– SketchUp visualization
– Overhang design

• Real world examples and applications
– How to “solar-passivate” existing buildings
– How to build the ideal passive solar house


What is Passive Solar?
Natural Conditioning

“The art and science of heating, cooling, lighting and
ventilating a building without outside fuels.”

• Passive solar heating
• Passive cooling
• Daylighting
• Cooling by natural ventilation


Recalling what we knew
• Anasazi understood these
principles
– The Anasazi Indians built stone
and mud dwellings in the deeply
carved canyons of the desert
Southwest dating back to 12th
century BCE.

– Nestled into south-facing canyon
walls under natural overhangs,
their homes were sheltered from
the intense summer sun.

– Yet as winter approached, the low-
angled sunlight dropped below the
overhang to provide warmth.


Recalling what we knew
The Greek city Olynthus – The ancient Greeks utilized
solar energy to heat their
homes. They understood the
value of sunlight so well they
treated solar access as a legal
right.

– The Greek city of Olynthus was
laid out so that homes would
have unfettered access to the
sun—5th century BCE


Where is this “technology” today?
“All streets trend east-west and all
lots are oriented north-south.

This orientation (which has become
standard practice in Davis and
elsewhere) helps the houses with
passive solar designs make full
use of the sun's energy.”

Village Homes, Davis CA

http://www.villagehomesdavis.org/home 7

From the sun to us…free
• The sun delivers to us, free of charge, 300 BTU/sf (88W/sf) of clean, green
energy every hour.

8

Making a friend of the sun
This is about 176 kWh to the average house, every hour, every day it’s
sunny.

– The key question is:

Friend?

9

Making a friend of the sun

Or foe?

10

So why do we continue building these?

North

11

So why are we not building solar-integrated
passive homes today?

• It’s too expensive.
• It’s too complicated.
• Energy is too cheap so why bother.
• Inconvenient.
• We will lose jobs, hurt the economy.
• Fear—loss of control.
• What else?
?

Benefits
• Americans spend about $54 billion each year heating and cooling
their homes (ignoring the externalized cost of energy—extraction,
distribution, pollution, climate disruption, etc.)

– Passive design can cut this cost significantly, and that’s just the
beginning.
13

Benefits…
• Natural conditioning (as opposed to air conditioning) is

– Simple (no moving parts)


Benefits…
Elegant (based on physics and natural laws—
biomimickry)

• Designs that follow natural laws tend to be more successful
over the long term.

15

Benefits…
– More efficient:

• Using energy with minimal conversions is fundamentally
more efficient (compare electric heater vs. solar heating)
– By the time we use it, electricity from coal is 15% efficient

16

Benefits…
Natural conditioning (as opposed to air conditioning) is

– More comfortable (radiant heating rather than forced air, etc.)
• Quiet, solid construction, warm in winter, cool in summer,
gradual temperature variations

17

Benefits…
– Attractive:
• Large windows, sunny, daylit interiors, open floor plans

– Results in a healthier house (indoor air quality is higher since
we’re not circulating pollutants)

18

Benefits…
– Lower life cycle cost
• increased economic security with rising energy costs

• In our “moderate” climate zone, utility bills of $300-$500 per month
in the summer and $150-$250 in winter are common and will go up.

19

Benefits…
– High level of owner satisfaction with increased
resale value

– Green (environmentally sound)

• A quality home need not be
green

• But a green home must be
high quality.

20

Patterns
All acts of building, no matter how large or small, are based on rules of
thumb developed through years human experience. We call these
rules of thumb “patterns.” *

21
*Ed Mazria, Christopher Alexander

Patterns
For example, a pattern that helps us decide how much load a horizontal
building member can bear:

20 feet

2 x 10 joist

22

Patterns
“Each pattern is connected to other patterns which relate to it. Every
pattern is independent, yet it needs other patterns to help make it
more complete.”*

We call this approach by other names, such as integrated or systems-
based building.

23
*Ed Mazria

Patterns
The fourteen patterns of passive solar design can be summarized thus:

1. Harvest solar heat by proper building orientation with respect
to the site and annual solar path.

2. Keep that heat in the building by proper air sealing and
insulation (quality envelope).

3. Store the heat (and level temperature variations in both
seasons) with properly designed interior thermal mass.

4. Use efficient backup heat for long overcast spells and
imperfect designs.

24

Pattern 1
Choose a site with good solar exposure


Pattern 1
On our site, we had to take down some eucalyptus trees and plant
lower canopy trees.

• This provided both sun and food.

26

Pattern 1
• The sun reaches higher in the sky in summer than in
winter.
– This is the altitude angle.

June 22
March 21
December 22

27

Pattern 1
The sun rises further northward in the summer than in the winter.
– This is the bearing angle, summer:


Pattern 1
The sun rises further northward in the summer than in the winter.
– This is the bearing angle, winter:

29

Pattern 1
A Solar Pathfinder knows all this and will determine where
the shadows fall throughout the year.


Pattern 2
Orient the long--east-west axis of a house--within 10 degrees of true
south

– Solar gain vs. degrees deviation from true south,
by rotation angle A:

• 0° 100%
• 22° 92%
• 45° 70%
• 67° 36%

A

South 31

Pattern 2…
• In warm climates, more than 10-degree deviation may cause
summer overheating, especially late in the day.

• “Choosing a good building shape and orientation are two of the most
critical elements of an integrated design.”
– Sustainable Buildings Industry Council

32

Pattern 3
Locate most windows on the south side of a house

– “The right amount” of south facing glass is the solar collection
system.

• Use the Goldilocks Principle

33

Pattern 3…
• Locate most windows on the south side of a house

– At the lowest solar altitude (winter solstice) the sun
can penetrate 20 ft into a house.

– With “proper” overhangs, solar collection diminishes
in summer (higher solar altitude).
• Courtesy of the solar control system.


Pattern 3…
• Locate most windows on the south side of a house

35

Pattern 4
Minimize windows on the north, west, and east sides and
“tune” them to the orientation

– Too much glazing on east and west walls causes summer
overheating.

– Too much glazing on north walls results in excessive heat loss.

36

Pattern 4…
– In general, we want to tune our windows thus:
• South:
– High solar heat gain coefficient (SHGC), >0.5
• East, west:
– Low solar heat gain coefficient (SHGC), <0.4
• All exposures:
– Low U-factor (<0.4) to minimize heat loss (best
insulation)
– Low-e glass for best overall performance both
seasons

37

Pattern 5
Provide overhangs and shading to regulate solar gain

– For additional shading on east and west walls, use exterior
window shading.

– Vertical trellis or long horizontal trellis can reduce western, late
afternoon sun.

38
http://www.susdesign.com/overhang/

Pattern 5…
• Provide overhangs and shading to regulate solar gain

Overhang calculated
for 32 degrees north
latitude

Energy10 model


Pattern 5
For San Diego, January 22, noon.

40

Pattern 5
For San Diego, June 22, noon.

41

Pattern 5…

– Use interior color selection that brings solar heat and daylight
deep into the interior

– Choose roof and wall colors and reflective indices that reduce
heat gain.

See http://www.coolroofs.org/

42

Pattern 5…
– Solar-integrated landscaping

• West and east side evergreen trees
– Summer cooling and winter heating (cut wind)

• South side deciduous trees

• Minimize heat-generating hardscapes and heat island


Pattern 5…
• Landscaping: nature provides smart shading

Shades in summer

Mulberry in winter


Pattern 5…
• Un-shaded south facing glazing needs awnings or
overhangs.


Pattern 5…
Jacaranda now cools the home in summer when west
facing rooms would overheat.


Pattern 6
Provide sufficient, properly situated thermal mass

– This is the critical element that deserves special attention

– “The basic strategy is to design the house so that its own
masses—mainly walls and floors—are so placed, proportioned,
and surfaced that they will receive and store a large measure of
incoming solar energy during the daylight hours and will gently
release this stored heat to the house interior during the night
hours or cloudy days.”

--Peter Van Dresser, Passive Solar House Basics


Pattern 6…
• Provide sufficient, properly situated thermal mass

Free or Incidental mass
• The parts of the home’s
structure or décor that absorb
thermal energy—act as thermal
mass.

Examples are:
• drywall
• framing lumber
• doors
• furniture
48

Pattern 6…

Sunlit mass or direct
mass
• Mass placed directly in the path
of incoming solar radiation.

Examples are:
• tile or masonry in the path of
sunlight
• fireplace surround in the path of
sunlight
• exposed slab floor in the path of
sunlight
49

Pattern 6…
Indirect mass
• Mass not accessible by incoming solar
radiation.

Examples are:

• tile or masonry not in the path of sunlight
• fireplace surround not in the path of
sunlight
• exposed slab floor not in the path of
sunlight
• walls not in the path of sunlight


Pattern 6

– The higher the density, the higher the heat storing capacity up to
about 4” thick.

Material Density (lbs/ft3)
Sheetrock 145
Concrete 140
Concrete block 130
Clay brick 120
Lightweight concrete block 110
Adobe 100

CCSE Presentation, Copyright 51
2011

Pattern 6…
Putting this all together…

Using the pattern that

7% of solar glazing balances with the
incidental thermal mass,

We use the following spreadsheet to
determine the solar glazing-to-thermal mass
balance…


Pattern 6…
South- Direct Indirect
facing Solar glazing Solar glazing sunlit Indirect floor
Total floor glass, Gs area Gs needed area Gs mass wall mass mass
area (sf) (sf) (sf) available (sf) Remainder (+/-) (1: 5.5) (1: 8.3) (1:40)
Amount Gs
Need needed
7% more? (sf)
+ thermal
2000 240 140 240 mass 100 550 830 4,000
2500 175 175 175 --- 0 0 0 0
+ thermal
3000 345 210 345 mass 135 743 1121 5400

53

Pattern 6…
Summary of solar glazing-to-mass balance:

– Take 7% of total floor area.
– If your south facing glazing is more than this, take the difference
and add correct ratios of thermal mass to store the additional
solar gain.
1:40
1:8.3

1:5.5


Pattern 6

– “Light-colored walls nearest solar glazing reflect light onto dark-
colored thermal mass located deeper within the structure to
ensure greater and more even distribution of heat.”
– Daniel Chiras


Pattern 7
Insulate walls, ceilings, floors foundations and
windows

– In other words, build a quality envelope with minimal
• uncontrolled conduction
• infiltration
• radiant gain.

56

Pattern 7…
windows

57

Pattern 7…
windows


Pattern 7…
windows

59

Pattern 8
Quality water barrier to protect insulation from moisture

60

Pattern 8
Quality water barrier to protect insulation from moisture

61

Pattern 9
Air barrier: seal the envelope, especially attic penetrations:

62

Pattern 9
Air barrier: much harder to control indoor temperatures with
a leaky building.

63

Pattern 10
Design thin: each room should be heated--directly or
indirectly--by solar heat

64

Pattern 11
Avoid sun drenching: create sun-free spaces

65

Pattern 12
Back up heating: provide efficient, properly sized,
environmentally responsible back-up heating.
– Tight ducts, etc.

66

Pattern 13
Protect homes from winds by landscaping or earth
sheltering


Pattern 14
Synchronize daily living with daily and
annual cycles.

68

Let’s apply what we’ve learned…

Which of these is a
passive solar design?

69

Let’s apply what we’ve learned…

South elevation

70

South elevation…

71

Concrete block building, west elevation…

72

Crawl space…bottom of the “thermal
envelope”

73

This home has a new, 84% efficiency furnace

74

This attic and subfloor space

75

Waterproofing high performance windows

76

Summary
1. Harvest solar heat by proper building orientation with respect
to the site and annual solar path.

2. Keep that heat in the building by proper air sealing and
insulation (quality envelope).

3. Store the heat (and level temperature variations in both
seasons) with properly designed interior thermal mass.

4. Use efficient backup heat for long overcast spells and
imperfect designs.

5. At the very least, build quality.


Top it off with renewable energy

78

Questions?


References and Acknowledgements
The Solar House: Passive Heating and Cooling, Daniel Chiras.
The Passive Solar Energy Book, Edward Mazria, Rodale Press, 1979.
The Passive Solar House, James Kachadorian
Green From the Ground Up, David Johnston
Natural Remodeling for the Not-So-Green House, Carol Venolia & Kelly Lerner
The Not So Big House, Sarah Susanka
Your Green Home, Alex Wilson
The Timeless Way of Building, Christopher Alexander
The Ecology of Commerce, Paul Hawken

Overhang calculator: http://www.susdesign.com/overhang/
Energy-10: Sustainable Building Industries Council (not currently supported)
http://www.villagehomesdavis.org/home
http://www.coolroofs.org/

80

Today’s Engineers
• Estimates of energy savings resulting from the
application of passive solar design concepts are
provided by:
– ASHRAE (1984)
– DOE (1980/1982)
– LBL (1981)
– Ed Mazria, architect and sustainability authority
(1979)

• “Passive solar heating, cooling and lighting design must
consider the building envelope and its orientation, the
thermal storage mass, and window configuration and
design.”

– From ASHRAE Handbook –HVAC Applications
2007, Ch. 33.


Notes:
Photos of fruit and nuts.
Simi’s house
Cool roof rating council link


Patterns

83
*Ed Mazria, Christopher Alexander

Passive Solar Design

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