Is mould a longevity issue?

Yes. Combined exposure to fungal spores and mycotoxins from damp building components is associated with chronic inflammation, neurological complaint, and immune dysregulation. Driven by humidity (anything above 60% RH for sustained periods), ventilation, and thermal-bridge geometry where condensation forms.

Should my home be sterile?

No. Indoor microbiome diversity correlates with adult immune resilience. Over-sterilised homes (bleach-everything, antibacterial-everywhere) reduce the beneficial bacterial population the immune system needs to train against. The rule is "clean, not sterile": humidity control, ventilation, and surface hygiene without aggressive antimicrobial chemistry.

How do I reduce dust-mite exposure?

Two variables: humidity and the wash cycle. Mites colonise above 50% RH, so envelope humidity control is preventive. Bedding washed at 60 °C weekly, mattress encasements, and minimising fabric-heavy surfaces in the bedroom are the next-order interventions.

Are dehumidifiers a good idea?

In high-humidity climates or for specific damp problem rooms, yes. The right answer is often a heat-recovery ventilation system (HRV/ERV) that brings the whole-house humidity envelope into the 40-50% target band by design, rather than a portable dehumidifier as a workaround.

Microbiology, the immune harmony of the home

The home is a microbial ecosystem, and the architectural decisions made at design (humidity envelope, ventilation, material specification) determine whether that ecosystem trains the immune system or stresses it.

What microbiology actually is, in a residence

Three populations matter:

Pathogenic and inflammatory: mould species, mycotoxins, dust mites, cockroach and rodent dander, biofilms in plumbing. The populations that produce illness when their environment favours them.
Commensal: the bacteria, archaea, fungi, and viruses that populate every indoor surface. The training set the adult immune system needs.
Hygiene-critical surfaces: kitchen counters, bathroom fixtures, bedding, soft furnishings. Where active hygiene matters because the population on the surface contacts food, mucosa, or skin daily.

The MAVI 129™ Microbiology domain scores all three.

The thresholds that matter

Relative humidity: target 40 to 50%. Below 30%, mucosal surfaces dry. Above 60% sustained, mould and mites flourish.
Surface temperature: should not drop more than 3 °C below ambient anywhere in the envelope; condensation produces the moisture that mould needs.
Air exchange rate: 0.35 air changes per hour minimum (ASHRAE residential), higher in kitchens and bathrooms.
Bedding wash temperature: 60 °C weekly for dust-mite control.
Indoor microbiome diversity: the marker that correlates with immune resilience (Kirjavainen et al. 2019).

Where the design decisions actually live

For most residential projects, the microbiology outcome is set by four decisions:

Humidity control. The envelope, the ventilation, the cooking and bathing exhaust, the moisture-bearing materials. A 40 to 50% RH envelope across seasons is the single biggest preventive measure.

Thermal-bridge elimination. Where surface temperature falls below dew point, condensation forms and mould follows. Thermography at design-stage and again at commissioning catches the problem geography before the mould does.

Ventilation rate and topology. Bathrooms and kitchens need extract; sleeping zones need fresh air; the whole house needs balanced exchange. HRV/ERV systems are the design-grade answer; window-only ventilation is the workaround.

Material biology. Natural-fibre soft furnishings shed less microplastic but retain more dust-mite reservoir without the right wash cycle. Hard floors with rugs that can be washed are the cleanest topology in bedrooms. Antimicrobial-treated finishes are usually counterproductive, they kill the commensal population alongside the problem.

What “microbiology” looks like in a MAVI Diagnostic

A residence’s Microbiology score is built from humidity logging by room, thermography of the envelope (cold spots predict condensation), surface dust analysis where the framework requires (mould-spore species, mite-allergen concentration, microbiome diversity profile), and an HVAC and ventilation review (extract rates, balance, filter chain).

The output is a 0 to 100 sub-score and a priority intervention list. For most residences, the highest-leverage interventions are humidity envelope control and thermal-bridge remediation.

The single thing to do today

Look in the corners of every room for mould spotting (especially bathrooms, behind furniture against external walls, around windows). Run a humidity logger for two weeks. Most problems are visible if you know where to look. The MAVI Snapshot flags geographies where mould risk is high; the Diagnostic does the per-room thermography and microbiology work.