Non-Toxic Siding – All Cladding Types Reviewed

A Review of Chemical Additives, Toxins, and Off-Gassing in Siding/Cladding

Those avoiding toxins or who have chemical sensitivities will want to consider the initial chemical off-gassing, toxins in the dust, as well as upkeep of the siding.

How often the siding needs to be repainted, and how healthy the paint is could be a critical consideration.

This post contains affiliate links to relevant products that I use and recommend. Upon purchase, I earn a small commission at no extra cost to you.

Mold Preventative Siding

Those who are building mold-preventative builds can use almost any type of siding as long as it’s installed correctly.

Almost all types of siding require a vented rainscreen.

I will note the few types I think will not work for a mold preventative build in my book and course.

Top Choices for the Chemically Sensitive

The most sensitive will want to avoid siding with off-gassing or coatings.

The choices below are divided up into those that are best for the most sensitive, the moderately sensitive, and the minorly sensitive in the book and course.

There are also a couple extra options in the book and course compared to the article, as well as the options I would definitely not go with.

1. Wood Siding – Finishes and Off-Gassing

Types of Wood and Finishes

Wood types used for cladding include redwood, cedar, pine, spruce, fir, cypress, oak, chestnut, and ipé. 

Most wood types that require finishing have to be refinished every couple of years, which is a downside for the chemically sensitive.

Plus the more “eco” stains need to be redone more often. 

But not all wood siding needs to be sealed/finished. 

Durability of Wood Siding

Wood siding can be more vulnerable to decay, rot, and vermin than non-organic types of siding.

Using the proper wood species, care (no sprinklers hitting the building), maintenance (if required), and installation are the keys to keeping the wood from rotting.

Some wood types are more prone to insect attack than others. It also depends on where you live.

If you go with a wood that needs painting, it can still be rot-resistant if the paint finish is re-done on schedule and you take care not to have sprinklers hitting the siding (which they never should anyway).

My post on exterior paints outlines the best brands.

Rot-resistant wood species that don’t need sealers and treated woods are in my book and course.

2. Metal Siding – Finishes and Off-Gassing

Steel and aluminum are the two main types of metal used for siding.

The benefits of metal siding are that it will last a long time, it doesn’t need to be repainted for decades.

There is a 30-year warranty on some products.

The finishes tend not to off-gas, or off-gas very little VOCs. You should get a sample as there are different finishes. 

PFAS paints are the norm, but there are also unfinished options.

Unfinished options and one type that is not recommended for mold prevention can be found in the book and course.

3. Types of Exterior Stucco Siding – Additives and Toxins

Types of Stucco:

Traditional Stucco 

Traditional stucco used today is usually made up of sand, Portland Cement, lime, and water.

Traditional stucco can be mixed by the contractor.

Traditional stucco breathes but it does need a drainage plane.

It is not very flexible, so anywhere there is movement (of the soil, foundation, and house) can result in cracks to the stucco and water can get in there.

Synthetic Stucco 

Synthetic stuccos are made with acrylic or other plastic polymers and are designed to be some level of waterproof (not breathable, or less breathable).

They are more flexible so they are less prone to cracking.

Synthetic stuccos are pre-colored from the factory.

They are also called polymer-modified, acrylic, or elastomeric stuccos. 

For most people, the off-gassing of VOCs from acrylic and other polymers is minor.

Those with extreme chemical sensitivity should proceed with caution.

Mold preventative types are outlined in the book and course.

One Coat Stucco 

One-coat stucco is mixed with fiberglass (applied over metal lath).

A newer method that very sensitive folks will want to test out first.

4. Fiber Cement Siding – Is it Safe For The Chemically Sensitive?

Fiber cement siding is made of wood pulp and Portland Cement.

Possibly with fly ash or silica added.

The most popular brand is James Hardie – the product is Hardie Plank.

It can look like a wood grain or be flat. 

The James Hardie factory-applied paint has a 15-year warranty.

You might need to do touch-ups on-site during installation with their touch up kits.

More details about that brand and the paints in the book and course.

It costs less than wood siding, more than vinyl. It’s very durable and is not going to rot. You don’t need to caulk the butt joints like with engineered wood.

5. Brick or Stone Veneer Cladding

Real Stone Cladding

Real stone cladding is 100% natural stone.

Granite, limestone, and sandstone are normally used.

Marble and slate can be used as well.

Some stones may be sealed, consult with your architect.

This is the most expensive option of them all.

Brick Cladding

If your walls are not made of brick themselves, you can add brick as the cladding.

When brick is used for cladding, it requires a rainscreen.

Brick is often not treated with any sealer.

Sometimes silanes/siloxanes water repellants are used.

Consult with your mold-aware architect on whether the brick requires a coating.

Limewash can also be used to coat exterior brick if you want it to have a white look, and if it’s recommended to stay vapor open.

RomaBio makes a breathable paint for this purpose.

Concrete casts can also be made to look like brick, similar to the stone look concrete casts.

Cement Stone Cladding

There are many cement-based sidings made to look like stone.

These veneer stones are made of Portland cement, aggregates, and iron oxides formed in molds to look like stone.

6. Vinyl/Plastic Siding – Is It a Healthy Choice?

Vinyl Siding

Vinyl siding is a common low-cost option. It comes with the color embedded and does not need to be painted. Though it can fade with time and you may choose to repaint it for that reason.

Some is hollow, and some in insulated with EPS foam (polystyrene).

Vinyl can look like wood and even cedar shake.

I got samples from KP and I did not detect any vinyl off-gassing.

I suspect these samples had already off-gassed because I can detect off-gassing from hard vinyl windows and LVP flooring.

If you are extremely sensitive you may want to track down a piece of this from the hardware store that is as freshly produced as the product you will be using on the house. 

In almost every situation, I would use siding that has a rainscreen. But vinyl without foam backing has a lot of air movement, and many mold-aware contractors and building science experts think there is enough air movement behind it.

An alternative to vinyl siding can be found in the book and course.

Corinne Segura is an InterNACHI-certified Healthy Homes Inspector with certifications in Building Biology, Healthier Materials and Sustainable Buildings, and more. She has 10 years of experience helping others create healthy homes. You can book a consult here.

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Join the top Substack on healing from MCS and mold!

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Sources

Bob Villa https://www.bobvila.com/articles/stucco-homes/

BuildingScience.com https://www.buildingscience.com/documents/digests/bsd-146-eifs-problems-and-solutions?searchterm=eifs

Mike Holmes https://www.theglobeandmail.com/life/home-and-garden/stucco-presents-a-unique-set-of-problems/article571936/

Cheryl Ciecko courses and materials.

Green Building Advisor https://www.greenbuildingadvisor.com/article/can-vinyl-siding-be-applied-over-furring-strips

This Old House

https://energyeducation.ca/encyclopedia/Fly_ash#cite_note-RE1-2

How to Specify: Stone Cladding

An Architect’s Guide To: Panel Brick