Talking ventilation, moisture & mold (without scaring clients)
How to talk to clients about ventilation, moisture and mold without scaring them – a 2‑minute script
Talking about moisture and mold with clients is a bit like talking about diets. Everyone has a story, everyone has an opinion, and half the advice contradicts the other half.
Some authorities say “open your windows more.” Others say “don’t open windows because energy.” Products promise “healthy air” with a sticker and a fan icon. And somewhere in there your client is just wondering why their last bathroom ceiling turned black.
Here’s the thing I wish more people would say out loud:
Ventilation is key above everything else.
Not sure what to spend your money on? A balanced low air‑flow ventilation system for the whole house will do more for comfort, moisture control and health than most shiny upgrades.
After testing hundreds of homes that look perfect in the marketing photos but fog the windows and hit 80–90% humidity the minute winter lands, I’ve stopped sugar‑coating it. Air has to move. Intentionally.
Let’s break this down into:
A 2‑minute script you can use with clients
What “balanced low air‑flow ventilation” actually looks like
Where the money should (and shouldn’t) go
The 2‑minute script (so you don’t need a PhD mid‑meeting)
Try something like this, in your own words:
“Everyday life makes moisture – showers, cooking, drying clothes, even just breathing. That’s normal.
If that moisture hangs around, you get steamed‑up windows, musty smells, and eventually mold.”
“Our job is not to lecture you about how many showers you have. Our job is to give that moisture a safe escape route and bring in fresh air automatically, not just when someone remembers to crack a window.”
“So in this house, we’re designing two things:
– Extraction in bathrooms, kitchen and laundry, so steam and smells don’t wander through the whole house
– Background fresh air to bedrooms and living spaces, so everything feels drier, fresher and more comfortable.”
“Done right, that means clearer windows, fewer smells, and a much lower chance we’re talking about mold in three years’ time.”
Notice what that script doesn’t do:
It doesn’t blame the occupants.
It doesn’t dive into ACH, Pa, or any other three‑letter acronyms.
It connects physics to experience – what life feels like in the house.
Then, if they’re interested, you can peel back one more layer: explain that moisture condenses on cold surfaces (often windows and uninsulated corners), and that good ventilation + good insulation dramatically reduces those cold, damp zones.
What “balanced low air‑flow ventilation” actually looks like
Let’s strip the jargon.
Balanced ventilation = what goes out is roughly matched by what comes in, through a designed system, not random cracks.
Low air‑flow = gentle but continuous, not a gale. Think “slow breathing,” not “hair dryer.”
In a typical three‑bedroom home, that might look like:
Small supply vents in each bedroom and main living space
Extract vents in bathrooms and possibly laundry
A central unit quietly moving air, possibly recovering heat along the way
Filters that can be swapped by a normal human, not a contortionist
The result?
No room is starved of fresh air.
Moist air is removed from the places that generate it.
You don’t rely on everyone remembering which windows to open and when.
Will it fix everything? No. If the house is wildly under‑insulated or full of thermal bridges, you can still get cold corners. But ventilation is the part people underestimate most – until their first winter.
Where should clients spend money first?
Here’s the awkward, honest order of operations I’ve seen work on real projects:
Basic weathertightness and reasonable insulation – don’t try to ventilate your way out of a leaking shell.
Reliable extraction in wet areas and kitchen – fans that actually move air, ducted outside, not just into the roof space.
Balanced low‑flow whole‑house ventilation – especially in airtight or reasonably tight homes.
Then start arguing about fancy taps, extra skylights and the stone that’s “healthier for the kids” (spoiler: it’s mostly marketing).
If the budget is tight and they ask, “We can only splurge on one big performance thing – what should it be?” I will happily throw other upgrades under the bus:
“If you want the biggest comfort and health gain for your money, go for a small, balanced, whole‑house ventilation system. We can keep the rest of the spec sensible and upgrade finishes later; you can’t retrofit lungs into the house easily.”
When not to push it? If the build is extremely leaky (old villa, minimal retrofit) and the budget is genuinely tiny, a full balanced system might be overkill for now. In that case, do extraction properly, improve airtightness where practical, and plan for a future system instead of pretending you already have one.
What this looks like on a job that “looked fine”
We worked on a project that ticked every brochure box: nice orientation, good insulation, stunning interior photos. The architect had sketched token bathroom fans, nothing in bedrooms, and relied on “operable windows” for the rest.
First winter in, the client’s experience:
Fogged‑up glass most mornings
Musty smell in the walk‑in wardrobe
Towels never quite dry in the ensuite
We logged humidity and CO₂ for a few weeks. Surprise: humidity was consistently high overnight in the bedrooms, CO₂ spikes whenever doors were closed, and bathroom moisture was wandering around like it paid rent.
Retrofitting a small balanced system (plus fixing the fans) radically calmed things down. No new marble, no new mood lighting. Just… air moving where it should.
That’s what “showing what others won’t” looks like: not a sexy render, but a simple line graph that explains why a kid’s asthma got better after the system went in.
Awkward questions you should answer upfront
Your clients are already thinking:
“Is this noisy?” – You can say: “If it’s designed and installed properly, it should be a soft background hum, not a bathroom fan in your bedroom.”
“What about maintenance?” – “You’ll need to change filters. Think of it like changing car oil – annoying, but cheaper than a new engine.”
“Will it dry my house out too much?” – “In our climate, the risk is usually too much moisture, not too little. If we ever get to desert‑dry, we’ll have different problems – and better beaches.”
And yes, talk approximate cost range. Not down to the last dollar, but enough that they don’t assume this is either free or a $50k add‑on.
When not to hire me
If a client just wants the cheapest tick‑box to get consent, and could not care less how the house feels in winter, I’m not going to add much value.
If their brief is: “We just want it to pass, we’re renting it out anyway,” then honestly, let the minimum spec do its minimum job and save the consultancy fee.
But if they’re already talking “healthy kids,” “we work from home a lot,” or “we never want another damp house,” then ventilation is the conversation that matters most.
We’ve tested hundreds of homes that look perfect until the fan goes on and the numbers start climbing. The ones that age well, feel good, and generate repeat work for the architect? They all have one thing in common: fresh air is baked into the concept, not added at the end.
A builder told me last week, “Clients will pay for stone benchtops without blinking, but try explaining a fan that doesn’t even have a light on it.” Your job is to help them see that the invisible stuff is what makes the visible stuff worth living with.
And no, it’s still not because the house needs to “breathe.” The people do.
