The matrix of options — a structured comparison of design alternatives evaluated against defined performance criteria before any single direction is committed — is how we make passive solar decisions in MÉTODO. Not instinct, not the last project's answer applied again, but a side-by-side reading of what each strategy offers and what it costs at the specific conditions of the site.
At mountain elevations near Denver, the passive solar design problem has a particular character: more solar radiation than the urban core (thinner atmosphere, higher elevation, frequent clear skies), but more extreme cold at night and faster diurnal temperature swings. The matrix must account for both sides of that equation.
Why a Matrix Before a Decision
Passive solar design has no single correct answer. The right configuration for a 280 square meter house at 2,000 meters on a southwest-facing lot is not the same as for an identical house on a flat east-facing lot at 1,600 meters. The variables compound: latitude, elevation, site orientation, glazing-to-floor-area ratio, thermal mass type and location, overhang geometry.
Without a comparison framework, decisions default to either convention or preference. Convention produces undifferentiated results. Preference without data produces buildings that perform poorly in the real climate.
The matrix of options: decide by comparing, not guessing.
Our comparison axes for passive solar strategies at this typology:
- Solar heat gain in January (kWh/day estimated from glazing area and SHGC)
- Overheating risk in July (shading required, calculated from overhang depth)
- Capital cost relative to envelope baseline
- Thermal mass integration complexity
- Plan flexibility (does the strategy constrain room layout)
The Three Primary Strategies We Compare
Direct gain: south-facing glazing with interior mass — concrete floor, stone wall, or water wall — directly in the solar path. The simplest system. At Denver's latitude (39.7N), winter sun altitude at noon is 27 degrees; summer solstice altitude is 74 degrees. A properly calculated roof overhang admits winter sun and blocks summer sun without moving parts.
Direct gain is our default recommendation because it has no mechanical components, the thermal mass is the finish floor or wall (no separate system), and the visual result — light moving through a room as the sun arc changes by season — is the primary spatial experience of a passive solar house.
Trombe wall: a south-facing masonry wall with glazing held 10 to 15 cm in front of it, vented at top and bottom. Heat is collected in the air gap and convected into the room. The wall itself radiates stored heat at night. The drawback: it blocks the view through the south wall and requires specific construction detailing at the air gap.
We include the Trombe wall in the matrix for projects with limited south-facing floor area or where the direct gain zone is constrained by program. In mountain climates with frequent clear cold nights, the overnight radiant contribution of a Trombe wall can meaningfully reduce mechanical heating demand.
Sunspace/solar greenhouse: a glazed transitional space on the south facade that buffers the primary interior. It pre-heats air before it enters the living space. The sunspace also extends the usable season — it is a livable space at 10 C when the exterior is at -10 C.
The sunspace adds floor area and capital cost. It requires careful venting design to prevent overheating in summer. For family homes where an enclosed garden or year-round planting area is part of the program, the cost-benefit ratio is favorable.
Elevation Effects on the Calculation
Denver at 1,600 meters receives roughly 4 to 5 percent more solar radiation than sea level due to atmospheric thinning. Mountain sites at 2,500 meters see 8 to 10 percent more. This is meaningful: it shifts the direct gain calculation and reduces the glazing area needed for a given heat target.
The other side: at elevation, nighttime temperatures drop faster and further. A passive solar house that is well-charged by 3:00 PM solar time can lose that heat through glazing between sunset and midnight unless the thermal mass is sized correctly and glazing has adequate nighttime U-value.
In mountain Colorado, triple glazing is not a luxury. It is the specification that makes passive solar viable. Double-pane units with low-E coating perform adequately in Denver proper; above 2,000 meters, nighttime heat loss through large south glazing areas can exceed daytime solar gain unless the glass U-value is 0.15 or lower (triple-pane range).
Reading the Matrix Output
After we populate the matrix with site-specific numbers, the decision is usually clear. One strategy will dominate on two or three of the five axes. The outlier cases — where two strategies are nearly tied — are the interesting ones, and they usually reveal a program preference rather than a performance preference.
A client who wants the south wall to be all glazing with a view will choose direct gain and accept the thermal mass coordination complexity. A client building a mountain retreat used primarily in winter and who wants low mechanical heating cost may prefer the Trombe wall's overnight radiation performance despite the view constraint.
The matrix makes that trade explicit. The client decides with full information.
Próximos pasos
If you are planning a residence at elevation on the Front Range or in the Colorado mountains, the passive solar strategy comparison is part of our schematic design phase. We bring the matrix to the design meeting and walk through it together.