The plan of a passive solar house tells you almost nothing about whether it works. The section tells you everything. The relationship between the sun's angle in December and the position of the glazing, the depth of the overhang, and the location of the thermal mass floor — these are vertical and diagonal relationships, invisible in plan, immediately legible in section.
In MÉTODO, we call this la sección como relato: the section as narrative. The section drawing tells the story of the house. For an author-built house with passive solar intent, it is the primary design document.
What a Casa de Autor Requires of Its Section
A casa de autor — an author-built house — is not a product type or a replication of a typology. It is a building where the design decisions are specific and accountable: specific to the site, the climate, the program, and the spatial intent of the architect. The client who commissions a casa de autor is not buying a unit — they are buying a position.
That position must extend to the technical. Passive solar performance is not decorative intent. It is a commitment: the section drawing will show the December sun reaching the thermal mass, and the mass will store that energy, and the house will stay warm through a cold clear night with less mechanical help than a house that did not make that commitment.
The section of a casa de autor with passive solar design is a drawing that integrates:
- The spatial sequence (how you move through the house vertically, how rooms relate across levels)
- The thermal strategy (where the sun enters, where it lands, how it is stored)
- The structural expression (concrete or timber frame as legible element)
- The material assembly (wall thickness, floor depth, the relationship between mass and insulation)
None of these are separable. Change the structural position and you change the thermal mass location. Change the floor section and you change the solar collection area. The section is the drawing where all of these resolve — or fail to.
The Section at Three Moments in Time
A well-drawn section for a passive solar house shows at least three conditions:
December 21 at noon: the winter solstice sun angle at the project latitude, drawn as a ray through the section. Where does it land? On concrete floor? On stone? On furniture that absorbs little and radiates less? If it misses the mass, the solar design needs revision. This drawing takes twenty minutes and reveals whether the spatial design supports the thermal intent.
June 21 at noon: the summer solstice. The high sun angle should be blocked by the overhang. The ray should stop at the overhang face, or at the glass face in the worst case, without penetrating to the floor. If it enters the house, overheating will follow.
A winter evening at 8 PM: not a sun angle — an atmospheric drawing. The sun has set. The thermal mass has been charged. The room is warm from radiant heat emitting from the concrete floor and the stone wall. Mechanical heating has not yet activated. This condition is not calculable from a single angle drawing — it requires the thermal model. But the section is where you can see whether the mass is in the right spatial relationship to the occupied zone: if people sit near it, it warms them. If it is behind a wall, it warms nothing but itself.
The Difference Between Aperture and Design
South-facing windows admit winter solar radiation. This is a fact of geometry. But admitting radiation and designing a passive solar house are not the same thing.
Passive solar design requires:
- Sizing the aperture relative to the heating load and the thermal mass capacity — too much glazing overheats the house on clear winter days unless the mass can absorb it
- Positioning the mass in the solar path and in the occupied thermal zone — a concrete wall at the back of a north-facing corridor stores heat but delivers it nowhere useful
- Calculating the shading so that the summer sun, which arrives at a steeper angle, does not simply cook the house through the same aperture that admits winter sun
- Connecting the ventilation so that summer nights — which in Colorado are often cool — can flush the stored heat from mass before the next day's sun arrives
Each of these is a section decision. The plan tells you nothing about the sun's altitude. The section shows you everything.
The Process Before the Style
The author-built house earns its character through its resolved technical decisions. The spatial quality of late afternoon light moving across a concrete floor on a January day is not styling — it is the consequence of a calculated section. The shadow that forms at the underside of the overhang in July marks the line where the shading geometry was correctly drawn.
The process before the style. The section before the elevations. The thermal model before the finish palette.
Próximos pasos
Designing an author-built house with passive solar intent requires a design team that begins with the section and the sun angles, not with the plan and the square footage. We work this way because the buildings that result perform differently than those that do not.