5 Tips to Building Mold Free Houses

Matt Risinger teams up with envelope consulting expert Peter Yost to discuss the five crucial keys for building a mold-free house. Filmed on-site at a new wood-framed construction project, the video addresses common concerns about moisture, temperature, and building materials that can foster mold growth. Peter Yost, with his extensive experience from Building Science Corporation, shares practical strategies to manage and mitigate mold risks. This episode is packed with valuable tips for both builders and homeowners to ensure a healthier, mold-resistant living environment.
5 Keys to Building a Mold-Free House
1. **Manage moisture, not mold** - Mold has been around a LOT longer than we have. We have learned to live with mold, not the other way around. Mold needs food, the right temperature, and water. The easiest and least expensive way to manage mold is to manage moisture.
2. **Design your home for your climate and site** - Ocean-side in Miami Florida is a different set of environmental conditions than cliff-side in Boulder Colorado. Favor rather than fight your site and climate.
3. **Flash and seal** - Focus on the most intense and most prevalent ways that building assemblies get wet-bulk water and air leakage. We flash to manage bulk water and we seal to manage air leaks (because air ALWAYS carries water as vapor wherever it goes...).
4. **Manage moisture INSIDE as well as OUTSIDE** - There are typically 4 spaces inside your home that get wet-bathrooms, kitchens, laundry rooms, and garages. These rooms need dedicated ventilation and/or dehumidification AND different kinds of building materials than other rooms in your home.
5. **Maintain your mold-free home** - Your builder set you up for successful mold management. Honor that investment by servicing your moisture management systems: gutters downspouts, and splash-blocks; HVAC filters and exhaust fan grilles; battery replacement in hygrometers.
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[@larryseibold4287]

FYI: Mold does not die when it is dried out, it goes dormant (for years), reactivating immediately when moisture is present again. It is often most dangerous when it is dry (airborne dust). Dry conditions keep it from growing, so start early with de-humidification and proper air flow and ventilation.

[@kylelaw7210]

Access panels so you can look under the tubs for leaks is on my wishlist for my next house. Also access panels on the back side of the shower so you can change/inspect the shower valve. Ideally they will be in a closet.

[@Recovering_Californian]

Mold resistant paint helps. Dehumidifiers. Metal siding.

[@ss-fc2fh]

Whole house dehumidifier is a have changer. After seeing Matt's video i had one installed. The humidity is always perfect so now the AC is only for temperature control. In Houston, the fall and spring are not too hot but still humid. The dehumidifier means our ac runs less.

[@SnowBob302]

Who did you use to put it in and how much did it cost? I’m in Montrose

[@vapeurdepisse]

But are the running costs similar to an AC

[@ss-fc2fh]

I'll check who installed it. It was just a regular HVAC shop. The cost was around $2,500. I bought the dehumidifier myself and paid the AC guy $1,000 to install.

[@DeeElle2]

Can you also share your source for the dehumidifier- what were your parameters?

[@ss-fc2fh]

@@DeeElle2 I bought the brand AprilAire after seeing it in Matt's channel and it is Nest compatible. You need to buy one that is the right size for your house.

[@ryansoo4000]

An interesting video! I would like you to do another on the process of drying out a house that gets soaked during construction. Too many times builders get the frame up (but no WRB, shingles or doors and windows installed) and then it pours rain. As soon as the rain stops they start sealing everything up - sometimes even installing the insulation and drywall before the wood dries out. Other people will put in a propane heater to help dry out the framing but they pump out a lot of moisture into the interior during the burn process. If your project does get soaked, depending on what stage you're at, how long should you wait before continuing on, what equipment should you use to dry out the interior and how do you test to see if things are indeed dry enough that mold won't start inside the walls after you close them up?

[@sammydog4417]

Buy a moisture meter. Wall and floor framing shall not be enclosed if the moisture content of framing exceeds 19%.

[@petrawagner4946]

Excellent point, right here!

[@KJSvitko]

Large roof over hangs are beautiful and protect the doors, windows and siding from rain and moisture damage. Water is the enemy of buildings. Architects and home builders need to bring back large roof over hangs

[@2000drg]

While true, large overhangs are not the best option for every situation, especially in areas where there is threat from phenomena like hurricanes and other high wind storms. Large overhangs in these areas can lead to excess damage. As they said in the video, "from climate to climate" is the best way to manage the water resistant needs of the home.

[@trickstothetrades1801]

I always tell my customers about the squeegee trick. It also keeps the glass shower doors looking streak and spot free.

[@koenraadprincen7212]

Mold needs 4 elements to grow, the fourth being the right level of acidity (pH) of the "food" surface.

[@raymondpeters9186]

Most mold I've encountered is on the back of drywall inside the wall like Matt said holes in the wall poorly sealed penetratiom drywall Bad

[@raymondpeters9186]

It's real simple use a building material that resist mold Pumicecrete with Lime plaster inside and metal siding outside Take care Ray I would love to build one of these buildings for Community First in Austin

[@maurozammarano6651]

“wipe it off with a bit of water and you got rid of spores“... yeah right ! Next time find someone who knows what is talking about

[@jasonwells131]

Thanks

[@SapBellySoul]

More Peter!!

[@ronm6585]

Thanks gents.

[@KennethFox]

5:50 Peter just flushed his credibility. You can't just wipe wood down with soapy water to remove mold. If it is growing, then it has roots into the wood. You need to sand it down and treat it with moldicides like Decon 30 or hydrogen peroxide.

[@DavisShopworx]

You can also skip the sanding and use a product like Anabac, but other mold remediation chemicals will kill the root as well without issue.

[@dgrayman6637]

I’ve heard you can use a 10% bleach in water solution. Any truth to that in your experience?

[@anthonykaiser974]

Yep. Mold is literally a systemic problem. They teach this in microbiology in college. Once it's there you either kill it, or dessicate it. If you can control the humidity, it goes dormant. Germans understand this, and they have masonry and stucco.

[@sammydog4417]

Absolutely.

[@CriticalThinker27]

He said to get rid of the spores. Not to kill the mold. Remove the water to kill the mold. It's not rocket science here.

[@DBTomO]

New house construction, supposedly air tight confirmed by a blower door test. Although one bedroom has a serious draft along one wall, down below the baseboards. Actually has a temperature difference of 20 degrees colder than the center of the room in the winter. The builder stuffed foam strips under the baseboard as a resolution. My fear is that this is a temporary solution and will eventually be a problem with condensation and mold. Thoughts?

[@trampfossil]

Hate the FORCED comercials!!! Loved the Video!!!

[@trickstothetrades1801]

I agree. I hated to do it but paid for KZbin Premium so I don’t get commercials. I watch a lot of KZbin so was worth for me anyway.

[@spenceralridge4958]

KZbin is not a charity. Although you can pay for Premium and eliminate the commercials.

[@alanmcrae8594]

QUESTION: if renovating a 50 year old stick built cabin in the woods (climate zone 4a: mixed humid) made from KD lumber, T1-11 siding, mix of paper & foil faced fiberglass insulation and thin wood paneling, what cost-effective contemporary cladding, moisture barrier, insulation and paneling would you use given that global climate change is going to increase both heat & humidity in climate zone 4a? Also, what would you use to paint the 2x4 & 2x6 studs & joists that would both kill any mold spores & seal them from any future humidity intrusions?

[@honkbeforeitstoolate587]

+1 topic to add to the list: Damp slabs. In Florida, lots of houses built in the 90s or older had little to no moisture barrier underneath, my at-grade slab only has a visqueen barrier, and the slab becomes so damp that if you put vinyl plank on it, mold forms underneath over time. Even with carpet which breathes, if a piece of furniture had a flat bottom, it would get mold under it. As of recently, vinyl plank manufacturers are requiring a moisture barrier underneath as a warranty stipulation. However, that doesn't necessarily solve the problem, because even if you keep the flooring dry, underneath the wall bottom plates is still untreated, and you'll still get mold under plastic moisture barrier. I'm wondering about some sort of paint-on product + plastic sheeting on top of that. Any input from experts on this topic? People need remedies and prevention for new constructions. A friend just had to remove buckling LVP out of his 2 year old ~375k new house and they found mold underneath it. Not sure if the builder didn't use vapor barrier or what, his house is a raised slab.

[@ForestToFarm]

Stego is an awesome vapor barrier. Very tough. I would put it under the slab and the footings.

[@davidcloyd1296]

Do you think a post and beam foundation is less prone to mold than a slab foundation?

[@mr3n10]

Hey Matt, I noticed 2x6 bottom plate with 2x4 walls... is that a pocket for the sheathing to sit on something treated. We typical pop exterior wall line 1/2" wider. As always great content. Thanks🙏

[@buildshow]

That is correct. It’s capturing the Zip-R6 sheathing bottom

[@mr3n10]

@buildshow Thanks for the response. We're hoping to see you in November. You're one of our heroes!!!

[@michaelbohanon8137]

Peter is so lucky to be on the internet with you....oh...gotta check my phone...you were saying?

[@suspicionofdeceit]

So bizarre the way people can’t put it away for even 10 minutes.

[@r.j.bedore9884]

He mentioned it in a previous video, but since he manages several projects at once he has to at least see who the call is from so he can decide if it can wait or not. If the inspector calls because someone forgot to unlock a house for him and he can't get someone there ASAP it could, be weeks before the inspector can get back there, which means that project is on hold for that time and he has to reschedule any subcontractors he had scheduled to come in after that inspection. That's why he checks it even when filming, because a missed call from the wrong person could lead to cascading delays that set a project back weeks or months. It may look unprofessional or inconsiderate to you, but him taking a couple seconds to potentially avoid delays is the kind of project manager you want.

[@paulcornell487]

I think he was just checking his notes for talking points. Relax dude. It didn’t bother Peter, so don’t let it bother you.

[@MakeMeThinkAgain]

I've been using a squeegee in my shower for over 25 years and besides reducing moisture it means you never have t o scrub your walls. I just wish I could do the tub the same way.

[@iamtyleraustin]

if its a block exterior home, would doing something like painting the block with SEMCO be a good precautionary measure? Also, is it overkill painting your studs from the beginning with a mold resistant paint? We are starting our build, and mold is a big one for us because I am missing the genes to detox it. I am leaving a home that was high levels for me, we rented aa place with much much lower ERMI levels, and I want to build with mold in mind. I have noticed block homes are way less prone to mold (from all the homes I've tested now) the place we moving to happens to be a block home area..

[@CMCraftsman]

If you listen to the unbuild it podcast you’d expect Peter to look much older than he does based on what his co hosts say… 🤣

[@TimGGleason]

“So Peter, how did Noah manage mold on the ark? I know you were there.” -Steve probably

[@vapeurdepisse]

Get a room 😂

[@homes24]

I think the reason you're showers drying so quick is not because of kerdi but heated floors lol. Mud pan would dry just as quick with heated floors.

[@MarkRose1337]

If someone has a severe mold allergy, **you need to yank that stud out**.

[@GenZyannd]

lol, Peter. so Matt watched that episode?

[@markbrown2296]

First?!

[@maurozammarano6651]

“wipe it off with a bit of water and you got rid of spores“... yeah right ! Next time find someone who knows what is talking about

[@TheHarkonnen1]

It was soap and water and let it dry.

[@petrawagner4946]

Sadly, the guy saying to just wash off the "visible mold" (there is always much more that isn't) with soapy water, is grossly uneducated about the dangers of mold and its spores.

[@rsmith02]

Outdoors on a job site in the sunlight?

[@CaptainGSR]

Modern wood and drywall houses = cheap moldy garbage

[@tealkerberus748]

Doesn't have to be. Put a good hat on it to keep the rain off and dehumidify everything inside the outermost skin. Mould can't grow without moisture.