Threshold maps medical conditions to the environmental and design factors that affect them. This page is the practitioner's tour of how the work is built: how to read an entry, what the evidence labels mean, and how Threshold organizes the environment a human body lives in.
Threshold is organized around three core entities. Together they form a triangulation: a medical condition, an environmental phenomenon, and the specific connection between the two.
What is happening in the human body. Each Condition is a medical diagnosis or recognized condition, organized so practitioners can find it the way they would expect to.
What is happening in the environment. Each Driver names an environmental phenomenon the body responds to: flicker, mold and mycotoxins, thermal stress, dirty electricity, and others.
The intersection. Each Junction is one Condition paired with one Health Driver, holding the specific information a practitioner needs: why this Driver matters for this Condition biologically, the strength of evidence behind that connection, and the design recommendation tailored to this pair.
Most reference works on healthy building organize either by environmental hazard or by best practice. Threshold organizes by the third axis: the occupant.
Threshold uses ICD-11, the World Health Organization's diagnostic taxonomy, as the spine for clinical classification. Chapter labels are laymanized so practitioners can navigate without medical training. Where ICD-11's chapter assignment diverges from a practitioner's intuition, Threshold defaults to the lay designation. Each Condition also carries lightweight metadata for filtering by trajectory, pathological mechanism, and environmental phenotype.
| Chapter | Example Conditions |
|---|---|
| Infections & Contagions | Lyme disease, Long COVID, chronic EBV |
| Tumors & Cancers | Breast cancer, lymphoma, glioblastoma |
| Blood Disorders | Sickle cell disease, hemophilia, thalassemia |
| Immune & Autoimmune Conditions | Multiple Sclerosis, Lupus, MCAS, CIRS |
| Hormonal & Metabolic Disorders | Type 1 & 2 diabetes, Hashimoto's, PCOS |
| Mental & Behavioral Conditions | Autism, ADHD, depression, bipolar disorder |
| Sleep Disorders | Insomnia, sleep apnea, narcolepsy |
| Neurological Disorders | Parkinson's, Alzheimer's, epilepsy, migraine, TBI |
| Vision & Eye Conditions | Macular degeneration, glaucoma, photophobia |
| Hearing & Ear Conditions | Tinnitus, Meniere's disease, hyperacusis |
| Heart & Vascular Conditions | POTS, hypertension, atrial fibrillation, tachycardia |
| Respiratory Conditions | Asthma, COPD, cystic fibrosis |
| Digestive & Gut Conditions | IBS, Crohn's disease, celiac, ulcerative colitis |
| Skin Conditions | Eczema, psoriasis, vitiligo |
| Mobility, Bone & Joint Conditions | Rheumatoid arthritis, osteoporosis, EDS, fibromyalgia |
| Urinary & Kidney Conditions | Interstitial cystitis, chronic kidney disease |
| Sexual & Reproductive Conditions | Endometriosis, infertility |
| Pregnancy & Postpartum | Preeclampsia, hyperemesis, postpartum depression |
| Newborn & Infant Conditions | Failure to thrive, neonatal abstinence syndrome |
A Health Driver is what the body is actually responding to. The naming discipline is patient-effect: Drivers are defined at the level of the biological response, not at the level of what builds the exposure or what mitigates it.
Drivers are organized by WHOLESOME, a nine-domain framework developed by Courtney Lebedzinski and drawn from her work at Wholesome Houses. Threshold uses it as the spine that places every Driver in its native home.
What the body takes in by breath, sip, and skin, thousands of times a day, without asking permission. Source-water composition, whole-house and point-of-use filtration, mechanical fresh-air strategy, particulate and gas control, real-time monitoring.
In ThresholdParticulate Matter, Volatile Organic Compounds, Ozone, Disinfection Byproducts.
Site, orientation, climate, and the body's spatial relationship to the building. The decisions made before walls go up. Universal Design lives here, alongside thermal regulation and the spatial design of the home for the actual occupants.
In ThresholdThermal Stress, Fall Hazards, Non-Adaptive Built Environment, Insufficient Exercise Infrastructure.
The materials side of healthy design. Anything the body touches, breathes around, or inherits from the slow off-gassing of finishes and furnishings. Solid wood instead of particleboard, mineral paints instead of synthetic, the chemistry the household will live with for the next thirty years.
In ThresholdPersistent Organic Pollutants, Bisphenols & Phthalates, Pesticides, Heavy Metals, Flame Retardants.
The sensory environment the nervous system is reading constantly, faster than the conscious mind can name. Light spectrum and timing, acoustic absorption and reflection, the proportions of the space, the materials' visual and tactile honesty.
In ThresholdFlicker, Glare, Light Intensity, Insufficient Daylight, Acoustic Overload, Circadian Disruption.
The electrical environment shared between the building's wiring and the human nervous system. Wiring methods, bedroom kill-switches, hardwired internet, lighting selected for clean electrical signatures, the home's electrical system treated as a health system because that is what it has quietly become.
In ThresholdDirty Electricity, Magnetic Fields, RF Radiation.
The home's capacity to keep functioning when the systems it depends on do not. Energy, water, food, and medical-equipment continuity through outages, boil notices, and supply-chain interruptions.
In ThresholdEngaged where resilience is a design-relevant concern in the condition itself: insulin-dependent conditions and grid reliability, oxygen-dependent conditions and emergency power, severely immunocompromised occupants and water-event preparedness.
How the home is operated and maintained over decades. Filters do not change themselves, dehumidifiers do not service themselves, and cleaning products can undo the work the materials were supposed to do.
In ThresholdEngaged primarily through Junction recommendations rather than standalone Drivers; operational behavior is a design output more than a design input.
Moisture is the master variable in maintaining a bio-compatible microecology. Get this one wrong and nothing else matters, because the house becomes a slow biological event. Vapor-open assemblies, dedicated dehumidification, drainage planes, capillary breaks, and envelope details decide whether the cascade gets started.
In ThresholdMolds & mycotoxins, bacteria & endotoxins, microbial VOCs.
The home's relationship to its context. Where the materials came from, what energy ran them, where the water leaves to, what the land was before and will be after. The layer where Building Biology meets ecological design.
In ThresholdEngaged primarily through source-side specifications inside Drivers rather than as discrete Health Drivers.
Health Drivers in Threshold are limited to environmental phenomena that can be addressed at the parcel scale: the lot, the building, and what is installed in or on it. Off-parcel influences are out of scope, even when they are real and meaningful to occupant health. The reason is sphere-of-influence. Practitioners make parcel-scale decisions.
Where an off-parcel influence does have a parcel-scale response, the response itself is in scope and lives inside the relevant Driver's Interventions.
A Junction is one record per Condition x Health Driver pair, and it answers three questions.
The mechanism field describes the biological pathway connecting the two. It is not a re-narration of the Driver's generic mechanism; it is a condition-specific explanation.
Every Junction carries an evidence tier rating the connection itself: not the Driver and not the Condition, but whether this Driver actually affects this Condition.
The recommendation selects and prioritizes from the Driver's Interventions list for this specific Condition. Recommendations are applied Driver knowledge, not repeated Driver knowledge.
Each Junction is tagged with one or more relationship types, describing how the Driver relates to the Condition across time.
Every Junction in Threshold carries an evidence tier. The tier rates the connection: how strong is the evidence that links this Health Driver to this Condition?
| Tier | What It Means |
|---|---|
| Tier 1 | Strong research consensus. Multiple high-quality studies establishing the connection. |
| Tier 2 | Moderate evidence. Smaller body of published literature, generally aligned in direction. |
| Tier 3 | Clinical observation across multiple practitioners. Repeated, named, and consistent, even where formal study is thin. |
| Mechanism established and reasoning sound; specific published evidence for the connection is limited. |
Tiers live on Junctions, not on Drivers, because the same Driver connects to different Conditions with different evidence strengths. Tier is a property of the connection. For example, the flicker/epilepsy connection has stronger evidence than the flicker/multiple sclerosis connection.
Healthy building does not have the research budget of pharma. Many of the connections practitioners encounter daily have thin published literature behind them and strong mechanistic reasoning in front of them. Building Biology operates on the precautionary principle, and Tier 4 is how that principle expresses itself inside the database.
Tier 4 entries are flagged so practitioners can weigh them deliberately. They are never camouflaged as established research, and Threshold does not publish speculation.
Are you a researcher or medical professional interested in refining these junctions?
Contact Research LeadLast reviewed: May 2026
