Design guidance
How much south glass is enough?
Balancing solar aperture against thermal mass and envelope losses — the first question every ambient-energy design has to answer.
Article in preparation
Sun · Sky · Earth · Air
Buildings in balance with their environment
Ambient House shares research, design guidance and example buildings for houses heated and cooled by the energy already around them — sunlight, night sky, ground and air. Free design tools are planned.
What is Ambient House
Not a business. A place to share what we learn.
Ambient House collects guidelines for designing buildings conditioned by ambient energy, descriptions of example buildings, and discussions of related topics such as the weather data needed to simulate how these buildings perform.
Most buildings fight their climate. A building conditioned by ambient energy does the opposite: its orientation, glazing, insulation and mass are arranged so that the surrounding environment does most of the heating and cooling.
Passive solar heating and nighttime ventilation cooling are the two most familiar examples, but the underlying idea is broader — four freely available resources, used deliberately.
Sun
Winter sunlight admitted through south-facing glazing and stored in thermal mass, then shaded out in summer.
Sky
Clear night skies act as a cold sink, drawing heat away from roofs and from air moved through the building.
Earth
Ground temperatures stay close to the annual average, moderating what the building has to work against.
Air
Cool night air, moved by wind or buoyancy, removes the heat a building gathers during the day.
Research & Articles
Writing on ambient building design
Articles and discussions on climate-responsive architecture, building energy performance, weather data, and the part buildings play in climate change. The first pieces are being written; topics below indicate the direction.
Cooling
Nighttime ventilation as a cooling strategy
What operable area, stack height and mass are needed for night air to carry a day's heat back out of a building.
Article in preparation
Weather data
Why typical-year data can mislead
Hourly weather records drive every simulation of an ambient building. Which years, and which variables, actually matter.
Article in preparation
Example buildings
Case studies, documented to a common template
Each example is described the same way — climate, envelope, solar aperture, thermal mass, ventilation and measured performance — so that buildings can be compared rather than merely admired.
Case study 01
Pagosa Springs House
Location
Pagosa Springs, Colorado
Type and use
Residential
Designer
Keith Sharp
A 3,658 ft² house conditioned entirely by ambient energy: direct-gain and Trombe-wall solar aperture on the south, very deep insulation, heavy interior mass, and stack-driven night ventilation between basement, main floor and loft.
Envelope
- Conditioned floor area
- 3,658 ft²
- Wall insulation
- Upper floors 16″ cellulose + 4″ fiberglass, R-73; basement 16″ polystyrene, R-65
- Ceiling insulation
- 36″ cellulose, R-139
- Floor insulation
- 12″ polystyrene, R-48
- Infiltration
- 0.6 ACH50
- Envelope heat loss coefficient
- 0.055 Btu/h·°F per ft² of floor area
Solar aperture & mass
- South-facing aperture
- 226 ft² gross, 155 ft² net transparent, 10° west of south
- Direct gain
- 124 ft² gross, SHGC 0.53, U-0.143
- Trombe wall
- 102 ft² gross, SHGC 0.76, U-0.167
- N / E / W windows
- 253 ft² total; no west windows
- Wall thermal mass
- 8″ concrete, 1,178 ft²
- Floor thermal mass
- 4″ concrete, 3,504 ft²
- Total thermal capacitance
- 15.15 Btu/°F per ft² of floor area
Ventilation & systems
- Operable window area
- Loft 30 ft², main floor 110 ft², basement 68 ft²
- Stack height
- 9 ft loft-to-main, 18 ft loft-to-basement
- Mechanical ventilation
- Zehnder Q600 ERV
- Backup heating
- Wood fireplace
- Backup cooling
- None
Measured performance
- Measured indoor range
- 63.5 – 79.5 °F (2022) · 61.9 – 79 °F (2023)
- Daily average indoor swing
- 2.1 °F (2022) · 2.5 °F (2023)
- Annual solar heating, measured
- 99.7% (2022, 27 h of wood fire) · 99.8% (2023, 20 h)
- Annual passive cooling, measured
- 100% (2022 and 2023)
- Heating degree days
- 7,670 °F-days (2022) · 8,460 °F-days (2023)
- Cooling degree days
- 673 °F-days (2022) · 589 °F-days (2023)
Design targets: 100% solar heating and 100% passive cooling (TMY3). Design indoor comfort range 65 – 80 °F.
For more information
- GreenHome Institute webinar
- Video by Christina Ransbury
- 2024 ASES National Solar Tour
- Solar Today (2023): Flouting conventional wisdom
Also: M. K. Sharp, “Measured performance of a house conditioned by ambient energy,” International Journal of Ambient Energy (2025).
Case study 02
Courtyard house, warm climate
Thick masonry walls, shuttered openings and cross-ventilation at night.
Documentation in preparation
Case study 03
Earth-sheltered house
Bermed walls and a glazed south face, working with stable ground temperatures.
Documentation in preparation
How ambient buildings work
Four moves, repeated every day of the year
Passive solar heating and nighttime ventilation cooling are the same system read in two directions: a building that can gather and hold heat can also shed it, if the design allows.
- 01
Collect
South-facing glazing admits low winter sun. Overhangs and orientation exclude it when the season turns.
- 02
Store
Concrete floors, masonry walls and Trombe walls absorb that heat and release it slowly, flattening the indoor swing.
- 03
Keep
Deep insulation and careful air sealing mean the collected heat stays where it was put, for days rather than hours.
- 04
Release
In summer, operable windows at different heights flush the stored heat out with cool night air before the next day begins.
Daily cycle, schematic
Outdoor air Indoor, mass-damped
Weather data & performance
A building's performance is only as good as the weather it is tested against
Predicting how an ambient building behaves means simulating it hour by hour across a full year. Air temperature, solar radiation, sky conditions and wind all enter the calculation — and the choice of dataset changes the answer.
- Hourly resolution
- 8,760 steps per year, not monthly averages
- Solar radiation
- Direct and diffuse components, separated
- Sky conditions
- Cloud cover governs nighttime radiant cooling
- Wind & air
- Drives ventilation cooling potential
Developing and evaluating suitable weather data sets is an active part of the research shared here, and one reason the planned design software may need to move beyond a spreadsheet.
Design tools — in development
A calculator for indoor temperature, planned
The intention is a free tool where you enter a building's parameters and receive predicted hourly indoor temperatures across a year. It does not exist yet: the current program runs in Excel, and details — including how weather data is handled — are still being worked out.
Interface sketch — not functional
Coming eventuallyInputs
Location / weather file
Site latitude and hourly dataset
Conditioned floor area
ft²
South-facing solar aperture
Gross and net transparent area, SHGC
Envelope heat loss coefficient
Btu/h·°F per ft²
Thermal capacitance
Btu/°F per ft²
Operable window area
For ventilation cooling
Output
Hourly indoor temperature for a full year, summarised as an annual profile — so a design can be judged before it is built.
JanJulDec
Illustrative only. No calculation is performed on this page.
Free knowledge, open exploration
Everything here is intended to be freely available — the guidelines, the example buildings, the discussions, and the design tools when they arrive.
This is an information-sharing effort. If the material helps you design, teach, study or simply understand a better building, it has done its job.
About
Keith Sharp
Retired professor · Continuing researcher
Keith Sharp is a retired professor who continues to research buildings heated and cooled by ambient energy. Ambient House is where that work — design guidelines, documented example buildings, and the weather-data questions behind them — is collected and shared.
The emphasis here is on the work rather than the author: measured buildings, stated assumptions, and methods others can check and use.
Get in touchContact
Questions, corrections and buildings worth documenting
Researchers, architects, students, builders and curious readers are all welcome to write. If you have designed or measured a building conditioned by ambient energy, it may belong in the examples.