There are two main roofing materials that are used by chemically sensitive folks or those avoiding toxins – asphalt shingles or standing seam metal roofs. The most extremely sensitive will go with metal.
We also need to consider the underlayment and sealants used. Some of the traditional sealants can be toxic and potent so be sure to carefully select all components in the design stage.
This article was written with the assistance of Andy Pace, a Healthy Home Concierge with over 30 years of experience in the healthy home building materials industry.
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1. Roofing Materials
Asphalt shingles are by far the most popular roofing material in the US and Canada. Even most chemically sensitive people go with this choice in the end (though likely not the most extremely sensitive).
They are made from asphalt reinforced by fiberglass wood or cellulose, and mineral granules. The first line of shingles has extra asphalt on the back.
This is the lowest-cost roofing material and virtually every roofing company is familiar with installing these singles.
The cons are that they are not the most durable or long-lasting option. For sensitive folks, there is some asphalt odor here, but it’s nothing like liquid asphalt that you may have seen used on some roofs or in the redoing of an asphalt road. Be sure to get samples and test them out for yourself.
Composite shingles are made of plastic polymers or rubber. They mimic the look of other materials like slate or wood. Sensitive folks can avoid that asphalt odor with these options.
The cons are that they are expensive and there are far fewer experienced roofers. Also, not all brands have proven themselves over time. Class-action lawsuits have been initiated against “lifetime” roofing products with names like Hardishake, Maxishake, and Permatek which have prematurely failed. Certainteed also got rid of their Symphony polypropylene slate-look shingles.
Current brands include EcoStar’s composites which look like real slate or wood and are made from recycled rubber (EPDM) and plastic (TPO). These are liked by the chemically sensitive. And DaVinci Roofscapes, which offers composite shake and slate-type products. They are polymer-based.
Standing Seam Metal Roofing
The main alternative to asphalt shingles, especially amongst the chemically sensitive, is standing seam metal roofs. The roofing panels meet in raised seams that interlock to keep moisture out.
Metal roofs are also good against heavy snowfall or wildfires.
Metal roofs last a long time, though they are more expensive than asphalt. Installation requires special skills and not every roofing company knows how to install a standing seam metal roof (though this is much more common than composite shingles).
The most extremely sensitive may want to learn about different paints used on the metals to select the best one for them. You can read more about that in Perscriptions for a Healthy Home.
Decking/sheathing options are covered here. The most common option for the chemically sensitive will be plywood, but there are other options to consider.
Under an asphalt shingle roof, an asphalt felt paper underlayment is used. This does not add significantly more offgassing.
Under a metal roof you can use a plastic underlayment, the ones I have checked out have almost no odor. Synthetic roofing underlayments look, feel, and smell similar to house wrap.
These synthetic underlayments come in permeable and non-permeable options. Be sure to consult with your architect or building science expert on which one is suitable for your roof design.
For areas that need sealing, including vulnerable laps, use caulk rather than the traditional black roofing cement.
These first two sections of basic underlayment do not replace peel-and-stick ice dam underlayments. Ice dam underlayments are peel-and-stick, thicker, and impermeable. They help prevent ice dams and water damage to your roof in certain climates. They are used under both metal and asphalt roofs.
Synthetic underlayment is the basic underlayment that is used across the whole roof over the decking.
TYPAR Surround VR Roof Underlayment – synthetic polymer material.
Certainteed Diamond Deck Synthetic Underlayment – a polypropylene and polymer composite.
Ownes Corning Titanium UDL
Slope Shield – Vapor permeable, self-adhering, zero VOC.
RoofShield – Polypropylene membrane, zero VOC.
Self-Adhering Ice Dam Protection
Sharkskin has an acrylic adhesive.
GRACE ICE & WATER SHIELD is a rubberized asphalt peel-and-stick.
Baffles are made out of foam or plastic – SmartBaffle is nontoxic polyethylene.
Butyl tape is used on metal seams. This is actually a putty that comes in a tape roll, it is very benign and will work for almost all chemically sensitive folks.
Asphalt caulking and sealants are super strong in odor and offgassing. They are used to seal nail holes around metal flashing and shingles in new roofs, and as the traditional flashing around chimneys, etc.
Sensitive folks should avoid liquid asphalt sealants and urethane ones as well (most urethane caulks as well as liquid urethane sealants). I would not use a butyl caulking either.
Silicone and polyether caulks are specified for the chemically sensitive. Around penetrations, flashing, around pipe boots (the pipe boots themselves can be EPDM or silicone), and gutters for metal and asphalt roofs there are two main sealants that you can use:
There are other brands of roofing sealants. But I would make sure you stick to silicone, polyether, or some very select ultra-low VOC polyurethanes.
- Sika Flex 715 is a polyether.
- NovaFlex Metal Roof Adhesive Sealant is a silicone.
- Titebond Metal Roof Sealant – this brand doesn’t make it clear which type it is, it’s either butyl or polyether.
Avoiding Liquid Asphalt
Metal roof flashing can be used around skylights, drip edges, roof penetrations, valleys, and more, says Paula Baker-Laporte, and then use the caulking sealant on the edges.
There are some roof designs (like certain passive house roof styles) that will require passive house tapes. Extoseal Encors and Siga Wigluv are two.
There are also peel-and-stick rubberized asphalt roll flashing that can be used on roofing to replace liquid asphalt in certain situations (like at valleys or around chimneys). These may be the same as the Ice and Water Dam peel and sticks.
You can hose off a metal roof with a hose and dish soap
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