Build Options
Every building system performs differently when evaluated through an indoor air quality lens. Some manage moisture well but use organic materials that mold can feed on. Others eliminate organic content entirely but cost more and require specialty contractors. Most conventional systems do neither.
The Good Air Standard evaluates all common residential construction systems using the same criteria: moisture management and drying ability, inspectability, organic content in the assembly, and VOC potential from wet-applied materials. The result is a classification that helps homeowners make informed decisions based on their priorities, budget, and access to contractors.
Choosing a system is only half the decision. The same four criteria apply to the materials that go inside it — the insulation, sheathing, sealants, and finishes — and a Tier A system detailed with the wrong materials does not produce a Tier A result. Every option below specifies mineral wool insulation, for reasons set out in Mineral Wool vs Sheep Wool. For everything else that goes in the assembly, start with the Materials guides.
How to Read This Table
The comparison table below groups systems into four tiers based on how well they serve people building for lower-risk indoor air quality.
Tier A — Recommended Systems we actively guide homeowners toward. Best combination of mold resilience, VOC control, contractor availability, and proven performance.
Tier B — Conditional Systems that can achieve good outcomes but carry caveats — organic content, specialist labor, or climate limitations — that make them unsuitable as primary recommendations for our core audience.
Tier C — Premium / Custom The highest level of protection. Premium materials, custom engineering, limited contractor availability. For owners willing to invest in the lowest achievable risk.
| Option | Strategy | Mold Resilience | VOC | Cost + | Crews | Best For |
|---|---|---|---|---|---|---|
| Tier A — Recommended | ||||||
| 1. Forgiving Wood | Dry + inspect | High | Low* | +10–20% | High | Most people |
| 2. AAC Blocks | Inorganic core | Mod–High | Minimal | +10–25% | Medium | Custom builds |
| 3. CMU + MW | Inorganic core | High | Low* | +15–30% | High–Med | Inorganic + buildable |
| 4. Steel Frame | No wood; condensation mgmt | High* | Low* | +20–40% | Medium | Engineered shell |
| Tier B — Conditional | ||||||
| 5. Faswall | Alkaline + breathable | High** | None | +20–40% | Low–Med | Foam-free ICF |
| 6. Hempcrete | Hygroscopic + pH | Mod–High** | Low** | +25–45% | Low | Natural build specialists |
| Tier C — Premium / Custom | ||||||
| 7. LECA | Inorganic + vapor-open | Highest | Near-zero | +30–50% | Very Low | Premium custom |
* Requires audit of sealants/tapes/adhesives. Near-zero VOC achievable with correct selections.
** Contains organic content. Performance conditional on detailing + drying. Disclosed on site.
Cost premiums relative to standard wood framing, 2026 U.S. averages. Varies by region/project.
Systems We Evaluate but Don't Recommend
These are common building systems that people search for and ask about. We publish honest, detailed evaluations of each through the same indoor air quality lens — explaining what the specific risks are, why they don't meet the Good Air Standard, and when they might still be acceptable for people outside our core audience. These are not ideological positions. They are evidence-informed assessments.
Systems We Evaluate But Don't Recommend
These are common building systems evaluated honestly through an indoor air quality lens. Each page explains why it doesn't meet the Good Air Standard and when it might still work.
About the Assessments
All evaluations are based on the Good Air Standard v1.0. Cost premiums are relative to standard wood-frame construction, using 2026 U.S. averages, and vary by region and project. Mold resilience and VOC ratings marked with an asterisk (*) require audit of sealants, tapes, and adhesives — near-zero VOC is achievable with correct material selections but is not automatic. Options marked with a double asterisk (**) contain organic content; performance is conditional on detailing and drying.
For implementation tools including spec packs, material selection guides, and contractor interview scripts for all 7 options, see the $79 Build Package.
Last reviewed: August 2026