These rank lower-risk materials within each category as Good, Better, or Best. Unlike the wall-assembly scoring rubric — which scores how a whole system dries and inspects — a single material is judged mainly on its chemical load: how much it off-gasses and how fully those emissions are disclosed, with moisture behavior as the secondary factor. "Best" is the lowest-risk, best-disclosed choice; "Good" is an acceptable baseline. Anything that ranks below Good is on the What to Avoid page. For the reasoning behind each substitution, see Safer Alternatives.
Insulation
Tier
Material
Why it ranks here
Best
Mineral wool (stone/slag)
Inorganic, no off-gassing, doesn't feed mold, and unlike fiberglass doesn't hold liquid water against the framing. Low-binder products have the cleanest disclosure.
Better
Formaldehyde-free fiberglass or wood-fiber board
Low, disclosed emissions (no added formaldehyde binder). Wood fiber is organic but vapor-open and well documented.
Good
Standard unfaced fiberglass batts
Acceptable baseline when emissions are disclosed; choose unfaced over kraft-faced, and keep it dry.
Sheathing & Structural Panels
Tier
Material
Why it ranks here
Best
Mineral / MgO board
Inorganic and effectively zero-VOC; no organic material to feed mold at the wet zone.
Better
Fiberglass-faced gypsum sheathing
Inorganic face (no paper), low disclosed emissions; far less mold-susceptible than OSB.
Good
Exterior-grade plywood (CDX)
Organic but dries and recovers better than OSB; choose low-formaldehyde, disclosed adhesives.
Interior Wall & Ceiling Surfaces
Tier
Material
Why it ranks here
Best
Lime or clay plaster
Zero-VOC, vapor-open, no paper facing to become mold food.
Better
Paperless / fiberglass-faced gypsum board
Low disclosed emissions and no paper food source at the surface.
Good
Mold-resistant (treated) gypsum board
Acceptable baseline; better than standard paper-faced board, which is on the avoid list.
Sealants & Adhesives
Tier
Material
Why it ranks here
Best
Solvent-free MS-polymer (hybrid) sealant with a full ingredient disclosure
Effectively zero-VOC and fully disclosed (e.g., a Declare or equivalent label).
Better
Low-VOC water-based construction adhesive
Low, disclosed emissions; cures with little odor.
Good
Products meeting SCAQMD / CARB VOC limits
Acceptable baseline — meets regulatory VOC ceilings, though "compliant" is a floor, not a guarantee.
Primers, Sealers & Paint
Tier
Material
Why it ranks here
Best
Mineral silicate (potassium silicate) paint
Inorganic and effectively zero-VOC with no biocides; bonds chemically to mineral substrates.
Better
Zero-VOC acrylic paint
Low base emissions — but specify zero-VOC colorants too, since tinting can reintroduce VOCs.
Good
Low-VOC paint certified GREENGUARD Gold
Acceptable baseline; a useful floor for sensitive occupants, not a ceiling.
Flooring
Tier
Material
Why it ranks here
Best
Tile, stone, or polished concrete
Inorganic and zero-VOC; mortar-set or mechanically fixed, so no adhesive off-gassing.
Better
Solid hardwood (nailed) with a zero-VOC finish, or natural linoleum
Low, disclosed emissions and no wet adhesive bed; natural linoleum is linseed-based, not vinyl.
Good
Engineered or click-lock wood, FloorScore-certified, floated (no adhesive)
Acceptable baseline with disclosed low emissions and no wet glue.
Roofing
Tier
Material
Why it ranks here
Best
Standing-seam metal
Inert, no off-gassing, very long service life, and sheds water cleanly.
Better
Clay or concrete tile, or slate
Inorganic and durable; effectively zero emissions.
Good
Asphalt shingles with a low-odor underlayment
Acceptable baseline; the most common roof, with modest, transient emissions when new.
How to Read the Rankings
These rankings are Good Air Homes' evaluative judgment, applied through the same lens as the rest of the standard: emissions and disclosure first, moisture and mold behavior second. They name material categories and performance characteristics, not brands — so a "Best" pick is a description to specify, not a product we sell or earn from. When a data sheet doesn't disclose emissions, treat the material as unranked here and see What to Avoid. Terms like vapor-open, off-gassing, and near-zero after cure are defined in the glossary.
