The Good Air Standard v1.0

What the Standard Covers

The Good Air Standard addresses the building envelope and material selections that determine long-term indoor air quality. It is not a comprehensive building code — it works alongside applicable building codes (IRC, IBC, local amendments) and does not replace structural, electrical, plumbing, or fire safety requirements. It adds a layer of requirements specifically targeting the conditions that produce poor indoor air quality: trapped moisture, organic materials in wet assemblies, volatile organic compound emissions from building materials, and inadequate ventilation.

The Standard applies to new construction and major remodels where the building envelope is being opened or replaced. Many individual requirements (material substitutions, ventilation upgrades, finish selections) can also be applied to minor remodels and targeted improvements.

Core Requirements

These requirements are assembly-agnostic — they apply to every build option in the Good Air Standard, from the Forgiving Wood Assembly to LECA. The specific strategies for meeting each requirement vary by option, but the requirement itself does not change.

1. Moisture Management

Every assembly must address all four layers of moisture control: bulk water management (roof drainage, site grading, foundation waterproofing, flashing at all penetrations), a drainage plane (water-resistive barrier plus ventilated rainscreen gap — minimum ¾ inch), vapor control appropriate to climate (no interior polyethylene vapor barriers in mixed or warm climates), and drying pathways (the assembly must be able to dry in at least one direction, preferably both). See Moisture Control Protocol for detailed guidance.

2. Drying Ability

The assembly must be capable of drying itself if moisture enters the wall cavity, roof assembly, or foundation assembly from any source. Assemblies that depend on perfect moisture exclusion — with no drying path if that exclusion fails — do not meet this requirement. This is the primary reason sealed-cavity systems (closed-cell spray foam, ICF with foam on both sides, SIPs with OSB skins) fail the Standard.

3. Inspectability

The assembly must allow visual inspection of the structural cavity and sheathing without requiring destruction of permanent building components. Insulation that can be pulled back or removed (mineral wool batts, loose-fill) meets this requirement. Insulation that permanently adheres to framing and sheathing (spray foam) does not. This requirement ensures that moisture problems, leaks, and mold growth can be detected before they become extensive.

4. Mold-Resistant Materials

Materials in contact with or adjacent to the wall cavity, roof cavity, or any location where moisture accumulation is possible must minimize organic content that serves as mold food. Specific requirements include: paperless (fiberglass-faced) gypsum board instead of paper-faced drywall, mineral wool insulation instead of fiberglass or cellulose, avoidance of OSB sheathing (use plywood, fiberglass-faced gypsum sheathing, or MgO board), and selection of exterior cladding and underlayment materials that do not trap moisture against organic substrates.

Options that use organic structural materials (wood framing in Options 1 and 5, hemp hurd in Option 6) must demonstrate that the assembly's drying ability and moisture management compensate for the organic content. Options that eliminate organic content from the envelope entirely (Options 2, 3, 4, 7) meet this requirement by material selection.

5. VOC Control — Three-Tier Disclosure

Every build option must document VOC emissions using the three-tier disclosure framework. For each option, the Standard identifies:

Tier 1 — Truly zero-VOC components: Materials that contain no volatile organic compounds by composition (mineral wool, LECA, lime plaster, metal roofing, inorganic fasteners). These are not "zero-VOC by certification threshold" — they are zero by chemistry.

Tier 2 — Near-zero after defined cure: Materials that emit VOCs during application but reach background levels within a defined cure period (typically 2–4 weeks for paints and coatings, 24–48 hours for shellac-based sealers). The cure period, ventilation requirements during cure, and expected post-cure emission levels must be documented.

Tier 3 — Requires manufacturer documentation: Materials where VOC emissions depend on specific formulation and cannot be determined from the product category alone (adhesives, sealants, tapes, joint compounds). The Standard requires that SDS (Safety Data Sheets) and emissions test data be obtained and reviewed for every Tier 3 product before purchase. GREENGUARD Gold certification is accepted as a minimum floor but is not sufficient as the sole criterion for sensitive-audience builds.

The phrase "near-zero VOC emissions after cure" refers to a home where Tier 1 components dominate the assembly, Tier 2 components have completed their cure period, and Tier 3 components have been individually verified. It does not mean "VOC-free." No home is VOC-free. The Standard's position is that with correct material selections and adequate cure time, indoor VOC levels can be reduced to near-zero — well below thresholds that affect most people, including many with chemical sensitivities.

6. Ventilation and Filtration

Mechanical ventilation is required. The Standard does not accept "open your windows" as a ventilation strategy. A balanced mechanical ventilation system — an energy recovery ventilator (ERV) or heat recovery ventilator (HRV), sized for the conditioned space — provides continuous fresh air exchange while recovering energy from exhausted air. This is the reinforcement layer. It works because the envelope is doing its job.

Filtration requirements: MERV 13 minimum at the air handler. HEPA filtration in the ERV/HRV supply if available for the selected unit. Duct materials: rigid metal preferred. Flex duct is acceptable if properly supported and sealed. Duct board (fiberglass-faced rigid insulation) is excluded — it traps dust, is difficult to clean, and degrades over time.

Humidity control: The HVAC system must be capable of maintaining indoor relative humidity between 30% and 50% year-round. In hot-humid climates, this may require a dedicated dehumidifier sized for the moisture load. Sustained indoor humidity above 60% creates conditions for mold growth on any organic surface, regardless of how well the envelope is detailed.

7. Construction-Phase Protocols

The Standard includes requirements for construction-phase moisture management — not just the finished assembly. Framing moisture content must be verified below 19% before enclosing. Mold found on framing during construction must be addressed per the Mold During Construction Protocol (dry, HEPA vacuum, dewaxed shellac seal, cure and ventilate). Biocide sprays and fungicidal primers are not accepted as mold treatment methods — they mask the problem without addressing the moisture source. Materials must be stored protected from weather during construction.

How Build Options Are Classified

The Good Air Standard classifies building systems into four tiers based on how well they meet the core requirements for our primary audience — people building for lower-risk indoor air quality, including those with chemical sensitivities and mold concerns.

Tier A — Recommended: Systems that meet all core requirements with the best combination of mold resilience, VOC control, contractor availability, and proven field performance. These are the paths we actively guide homeowners toward. Currently: Forgiving Wood Assembly, AAC Blocks, CMU + Mineral Wool, Steel Frame.

Tier B — Conditional: Systems that can meet the core requirements but carry caveats — organic content, specialist labor requirements, climate limitations, or less-established field performance data — that make them unsuitable as primary recommendations for our core audience. Currently: Faswall Blocks, Hempcrete.

Tier C — Premium / Custom: Systems that achieve the highest level of core requirement compliance but require premium materials, custom engineering, and specialty contractors not widely available. Currently: LECA.

Tier D — Systems We Evaluate But Don't Recommend: Common building systems that fail one or more core requirements. Each receives an honest evaluation explaining specifically what fails, why, and when the system might still be acceptable for people outside our core audience. Currently: ICF, SIPs, Standard Stick-Frame, Spray Foam.

See the Build Options comparison table for a side-by-side view of all systems.

The Diamond Standard

The Diamond Standard is a performance specification representing the highest level of protection the Good Air Standard defines. It is not a product, not a build option, and not a service offered by Good Air Homes. It is a target: every layer of the building envelope simultaneously inorganic, designed to be vapor-open throughout the assembly, and ultra-low VOC at every wet-applied layer, documented and disclosed.

No certified builds exist yet. First certified builds are targeting 2027. The Diamond Standard is referenced here as an aspirational benchmark — the theoretical ceiling against which all other options can be compared.

Tradeoffs and Limitations

The Good Air Standard optimizes for indoor air quality. It does not optimize for cost, energy efficiency, sound transmission, fire resistance, or structural performance as primary objectives — though many of the recommended assemblies perform well on these dimensions as a secondary benefit. Where the Standard's requirements conflict with other priorities, we disclose the tradeoff rather than pretending it doesn't exist.

The Standard is evidence-informed, not evidence-proven. Building science is an applied field where controlled experiments are difficult and long-term outcome data is limited. Many of our recommendations are based on established principles (moisture physics, material properties, field observation) rather than randomized controlled trials. Where the evidence base is strong, we say so. Where it is limited or evolving, we say that too. The Evidence Policy describes how we evaluate and weight different types of evidence.

The Standard does not guarantee outcomes. A home built to the Good Air Standard, using recommended materials and properly detailed by a competent builder, significantly reduces the risk of indoor air quality problems compared to standard construction. It does not eliminate that risk. Construction quality varies. Climate conditions vary. Occupant behavior affects indoor air quality. The Standard reduces the variables you can control — it cannot control the ones you cannot.

The Standard in Full

The Good Air Standard is published as nine documents. The rubric defines how systems are scored; the assembly standards define what a passing assembly looks like; the glossary, evidence policy, corrections log, and changelog govern how the Standard is written and revised.

Systems are scored against this Standard on the Build Options comparison, and the materials that go inside them are covered in the Materials guides. To check a specific claim a builder has made, use the verification tool.

Version History

Good Air Standard v1.0 — Published February 2026. Initial release covering 7 build options across 4 tiers, 7 core requirements, three-tier VOC disclosure framework, and construction-phase protocols. All changes to the Standard are logged in the Changelog with date, rationale, and affected options.

To report an error in the Standard, use the Report an Error mechanism. All corrections are published in the public corrections log.