2. Introduction
Steven M. Knaub, Jr., RA, AIA, LEED AP
Gannett Fleming / Ganflec Architects, Camp Hill, Pennsylvania
Email: sknaub@gfnet.com
3. Learning Objectives
To understand:
• Definition, history, benefits and relationship of passive solar with other energy types
• Common uses and strategies for passive solar design
• Heating opportunities
• Cooling, and heat avoidance, opportunities
• Lighting opportunities
• The impact of building material choices, and technology changes, on passive solar design
• Regional concerns
5. Active Solar
Mechanical and electrical devices are used to harvest energy from the sun.
Solar ThermalPhotovoltaic
6. Passive Solar
Building and site elements are used to collect, store, and distribute solar energy - or to limit
solar energy input by reflection or shading.
Mechanical and electrical devices are not part of a pure Passive Solar design.
Devices can be used alongside a Passive strategy or to enhance its performance.
9. Why Passive Solar?
Buildings already use passive solar design components, so it can cost little or nothing.
It’s not bleeding-edge technology; it has a long, extensive, working history.
Every building that is exposed to sunlight has a passive solar design, somewhere between
excellent and terrible. Passive solar interaction is generally not avoidable, so choose to
respond responsibly.
11. Solar Orientation & Massing
Optimal designs are typically:
Stretched somewhat East-West
Proportions and shape-irregularities are limited, such
that the exposed perimeter area is not oversized
compared to the building’s volume
Where sites do not permit optimal orientation, solar
energy harvesting will be less efficient, but the
building's skin can still respond to solar orientation
12. Consider Climate
Daily temperature range and humidity influence passive solar
strategy effectiveness
A main strategy of shading-type sun control is more appropriate
for certain climates, while direct solar absorption will perform
better in others; usually both are useful in some combination
The importance, effectiveness, and location within a building, of
thermal mass also varies by climate
Climate Type examples from Continental US:
Humid Continental
Humid Subtropical
Semi-Arid
Arid
14. Thermal Mass
Depending on climate, thermal mass may perform better at a building’s skin or perform better
at its core, with a lightweight insulated envelope
15. Color Selection
Choose roof & wall colors based on climate and building use
Some building-types have cooling as their dominant load, regardless of climate
Note that dark building surfaces not only warm buildings but exacerbate the heat island effect
16. Sun Control, using
Seasonal Sun Angles
Direct-Gain/Loss is the most common passive
system
Sun Control strategies are similar across system-
types, Direct-Gain strategy used as illustration
The humidity and limited daily temperature range of
certain regions limits cooling potential to mainly
heat avoidance
Earth Tubes can extend passive cooling ability in
the above described climates but may require
mechanical dehumidification and may require
mechanical ventilation
17. Sun Control, using Seasonal Sun Angles
Method 1, published tables & charts
Charts may initially inform a design more quickly than modeling
23. Sun Control, using Seasonal Sun Angles
SHADOW SETTINGS, WINTER SOLSTICE, NOON
SHADOW LINE
HEAT INPUT
24. Sun Control, using Seasonal Sun Angles
SHADOW SETTINGS, SUMMER SOLSTICE, NOON
SHADOW LINE
HEAT EXCLUSION
25. Glass & Insulation Selection
Glass technology has advanced significantly, in terms of resisting building overheating, while
maintaining clarity and visible light transmittance
Glass with a relatively low Solar Heat Gain Coefficient (SHGC) is generally good for daylight
harvesting, without penalty; however, it will greatly reduce the efficiency collecting energy
from the sun
For building elevations or windows intended to collect solar heat, modern, insulated, glass can
be used, but a higher SHGC should be selected compared to the rest of the building
26. Glass & Insulation Selection
Insulation requirements have increased, and Passive Solar design generally benefits from
greater insulation
However, insulating mass walls designed to absorb daytime heat and radiate it at night can be
disruptive
The energy code can be satisfied without meeting prescriptive insulation requirements; whole-
building energy modeling is an acceptable compliance path
27. Daylight Harvesting
Consider each building elevation separately
North lighting is generally indirect; it requires little control; in cold climates extensive North-
facing glass can exacerbate heat-loss
South lighting is generally controllable, with little glare during most seasons, and is usable for
heat; if South-facing glass is not designed passively, it will cause overheating
Low-angle, East lighting, if not controlled can cause morning glare; West lighting can cause
afternoon glare and has the most intense overheating potential
Overhangs and horizontal sunshades have limited effectiveness on East and West elevations;
for extensive glass, operable vertical fins or shutters are most effective for these exposures
Another strategy for East and West elevations is to limit glazing
Top-lighting is the most effective method for daylighting, but it can cause overheating and
winter heat loss, and it has limitations in multi-story buildings
28. Vegetation and other Site Features
Deciduous trees provide shelter from the sun in the warmer half of the year and allow the
sun’s heat to warm a building in the colder half
Use evergreen vegetation where overheating is a year-round concern, such as West
elevations
Dense vegetation or tall neighboring buildings may negate certain passive solar strategies
29. Passive Solar Design and Building Systems
Passive design can achieve American or Western interior temperature and humidity
expectations, without mechanical augmentation, but in fairly limited climates
Building-users can adjust expectations
More commonly, passive design will work to decrease mechanical heating and cooling needs,
and to make those systems more efficient
30. Green Building Ratings Systems addressing
Passive Solar
The most notable system is, the German, Passivhaus
Extensive Passive Solar design is used, with super-insulated envelope, allowing minimal
mechanical systems
Common features are direct-gain South Wall, limited glazing on other elevations, Earth Tubes
ventilated with small energy-recovery ventilator(s), Solar PVs, small dehumidifier or air-
conditioner, and often no heating system
31. Green Building Ratings Systems addressing
Passive Solar
Passivhaus goals are not buildings that are pure passive solar designs
The goal is to make buildings that are nearly sufficient as passive solar designs and can then
be easily made passive (net zero), and to use no deficit energy, in terms of total energy use.
