Roofing for the chemically sensitive poses certain challenges. First you will want to avoid composite building materials that are held together with toxic glues. But you may also react to the terpenes in softwoods present in what is called SPF (which stands for spruce, pine, fir) framing lumber. Terpenes are VOCs. We tend to think of VOCs in connection with human made chemicals like paint, but certain trees, especially softwoods, are a source of VOCs—something to be aware of in a healthy building project.
“The Smoky Mountains are called smoky because of chemical emissions from trees,” said Jonathan Abbatt, a professor at the University of Toronto.
Since framing your roof with hardwood lumber is likely cost prohibitive for most people, the solution we used was to attach an aluminum building foil called Denny foil to the ceiling joists before the ceiling was installed.
“Some of the softwood framing in a house can be separated from the living space by the use of an air tight, aluminum-foil barrier, thus protecting a sensitive occupant from bothersome odors.”
Double sided Denny foil is the aluminum foil barrier often recommended to the chemically sensitive because it is usually well tolerated. It is Kraft paper sandwiched between two pieces of heavy aluminum foil and adhered together with a non-toxic glue. The Denny foil seams are sealed with an aluminum tape (Polyken 337 and Shurtape are two brands). If you need to quarantine your living space from a challenging part of the house like the roofing materials or, god forbid, a moldy room, Denny foil and aluminum tape can be an efficient barrier for this.
We were told fir and spruce wood have less terpenes than pine, so ask your roof framer if it is possible to source either of these woods instead of pine. Since spruce, pine, and fir framing lumber are sold bundled together, they will likely tell you “No, that is impossible,” and possibly look cranky like they now suspect that you are going to be a problem client. (You probably will be, but it is not your fault! Building a healthy house is not easy!) But it is worth asking and even calling some local lumberyards. We were able to order all fir from a lumberyard a couple hours away after making a few calls.
You will, of course, tell all your contractors and subcontractors about your sensitivities and the need to use only those building materials you have approved. Unfortunately, many people will nod and agree, but they do not really understand this illness and how serious our adverse reactions are. Because of this, they may attempt to use materials that they have decided are fine for you and use them in your building without asking, especially if they think you will never find out. So before we continue, I would like to mention some products roof framers use that you do not want in your safe house. After the roof framing materials arrive on your job site, take a look at what was delivered. If anything looks weird to you, ask what it is and how it will be used.
Structural Composite Lumber:
Structural composite lumber includes “laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL) and oriented strand lumber (OSL), and is a family of engineered wood products created by layering wood veneers, strands or flakes with moisture resistant adhesive into blocks of material known as billets, which are subsequently re-sawn into specified sizes. Typical uses for SCL include rafters, headers, beams, joists, studs, columns, and I-joist flange material.”
Laminated Veneer Lumber
“Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rim board, and edge-forming material.”
You may have noticed all of the engineered wood mentioned above is held together with adhesives. Not only are adhesives to be avoided as much as possible in a healthy house, the amount of material required to build your whole roof means quite a lot of adhesives would be up there off-gassing away. Some people may tell you they can seal the engineered wood. Those people are proposing you use a questionable material that you have to trust will not be off gassing into the air you breathe and then add another product to it that will also have to off gas and may or may not completely seal the questionable material. Our philosophy was to use the safest possible materials we could in every situation. That sounds obvious but you would be surprised at the building methods pitched to us despite our clearly stated objective to build the safest house possible.
Once your roof is framed, the next step is the roof deck. Typically, exterior grade plywood is used here.
“Virtually all construction-grade plywood, both interior and exterior grade, is made with phenol-formaldehyde (PF) glue.” Healthy House Institute, Plywood Article
Since my reactions to formaldehyde are horrible (headaches, brain fog, and an alarming downward spiral of other awful symptoms), the thought of attaching the roofer’s estimate of 50 plywood boards to our roof seemed very risky. A healthy house consultant we were working with insisted it would be fine. The above Healthy House Institute article said that it would be separated from the living space and “generally won’t bother a sensitive person.” I did not believe them. Assuming your aluminum foil ceiling barrier is very effective, you will still need to vent your roof to protect it from mold which means those formaldehyde fumes can waft out of those vents and pollute the air all around your house, particularly on windy days when air is blowing through. What happens when you sit outside or open your windows?
Allow me to digress for a moment and explain a common method of venting the roof:
New Mexico building codes require 3” diameter vents every 3 feet under the eaves around the entire periphery of the roof. An additional ridge vent runs the entire length of the roof ridge. It is covered in metal screening to keep insects out and capped with a ridge cap. Even during the worst of our monsoon season rains when we have high humidity, the rafters and roof decking have remained dry and mold free.
Now back to the topic of roof decking materials… You may have heard of formaldehyde-free plywood such as Columbia Forest Products PureBond. I tested it and had a bad reaction, but you may not so test it if you want to pursue this solution. (Unfortunately, building a healthy house requires putting yourself in harms way to determine if a product or material is safe for you.) The other board often recommended to the chemically sensitive is MgO (magnesia oxide) board. I reacted to it as well and have since read that my reaction is not uncommon:
“MgO board is a cementitious wallboard that claims it is non-toxic and VOC-free, and very impervious to mold. I have some doubts about the VOC claims because a person I know sent in a sample for testing and it showed formaldehyde off gassing. And, many people react to it.”
After weighing all the options, we decided to use tongue and groove aspen as the roof decking. I do not have a picture of the aspen covering the whole roof—the above photo is of the aspen just starting to go up.
Once the whole roof was covered with aspen, the waterproof roofing underlayment was attached. We chose Titanium UDL because the MSDS (material safety data sheet) gave it a health rating of zero on a scale of 1 to 5 with 5 being the worst possible health rating:
And I am very allergic to mold and was encouraged by the claim that it would be safe if we developed a leak and it got wet:
“UDL25 is 100% synthetic and unlike oil saturated felt is unaffected by water. It is also inert to mold and mildew.”
The final step was the corrugated metal roofing. Metal roofing is a well-tolerated material, especially if the paint finish is baked on—look for the words “thermoset” in the paint description.
Roofing: Part 2 will cover insulation, sealing vent pipes and the ceiling material.