We will be building a new house for ourselves this year. We want to build and market it as being energy effecient, earth friendly, and having excellent indoor air quality. We have in our family (and know of others) individuals with sensitivities to v.o.c.’s, and the outgassing of chemicals. We will have no carpeting,low v.o.c. paint and finishes, no particle board or vinyl, etc. One question I haven’t found an answer for is o.s.b. vs plywood for sheathing.
I’m not talking about delamination issues, strength, ability to hold nails, etc. I use o.s.b.in most of my projects now and have no problem with it from a structural standpoint. What I’m interested in is the chemical makeup of the two products. Is one healthier than the other. I’ve heard conflicting reports. Some say that o.s.b. has more glues and resins and that it will outgas forever. Others say that that the glues are the same but plywood contains more glue than o.s.b. This is not a trivial matter to some people (more I think than we realize) and I need to feel comfortable with what we build . Any thoughts?
Replies
healthier as far as indoor air quality?
I'd say either ... since you'll have insulation, some sort of vapor barrier and most likely latex paint ... which is a VB in it's own.
That said ... no scientific info here ... but osb is scraps of wood with lotsa glue.
I'd bet Ply is more "sensitive" friendly.
there's gotta be some real info on this out there somewhere.
Jeff
Buck Construction
Artistry in Carpentry
Pgh, PA
Spray on foam might help with the walls but a vapor barrier doesn't necessarily stop the passage of air with all the penetrations. And what about the floors?
sheathing made me thing walls ...
depending how committed to this you are ...
diagonal 1x6 still makes for a good floor.
actually ... plank lumber still makes for a nice solid wall too.
just costs money, is all.
U want less modern interference ... think old style construction.
depending on the situation ... the up charge might be well worth it in the end.
have you researched this subject?
I'm now curious if there is indeed a stand out non-alergin/non-toxic substitute sheeting product out there. If not ... I see a small but lucrative market.
is concrete out of the question?
Jeff Buck Construction
Artistry in Carpentry
Pgh, PA
Yes I've thought of 1x stock laid up diagonaly as a subfloor and also as wall and roof sheathing. Actually have friends who did just that instead of ply. This was in the pre o.s.b. days. I think this would be too labor intensive especially if we will market homes that are built to a certain standard of indoor air quality.
I can see doing it for myself as a last resort, but the market might be too small to justify the expense for all but a few. That's why I'm trying to find a reliable source who can speak to the different chemicals associated with o.s.b. and ply. MSDS are a starting point but they typically only address installation and handling exposures and don't address long term exposures such as living in a sealed home.
Concrete, or icf's may be a choice for some buyers,but don't fit the budget for my personal home. From what I understand, poly foam is fairly inert and doesn't outgas, but I can build a well insulated wall and roof for myself much cheaper with sheet goods.
I haven't looked, but would the manufatures have a MSDS on ply and OSB?
I have worked (as a construction lackey, not a designer) on a few LEED homes, and have seen OSB and ply used in both. I really liked the one with passive solar and SIPS that was built on a clear cut hilltop and a 50 minute commute to anything like work or groceries. But thats a different thread.
Since they both use more or less the same glue, I doubt you'll have any big differences there.
My only thought is that OSB is made from smaller trees, where plywood has to come from bigger/older ones.
Scamp,
I agree with what Jeff said - old fashioned construction is still possible and will introduce fewer VOC's into your air. The wall sheathing isn't much of an issue because it's outside the insulation envelope. You can build without wall sheathing anyway if there's enough bracing in the faming. I don't think the cost of board subfloors is a whole lot more than panels. It takes longer to install but costs less in the first place. You night have to watch the joist spans in the design stage to keep within the limits of what you can do with lumber if I-joists or floor trusses are out of the question.
Alternatively, you could look at ICF wall construction with a Hambro joist concrete floor system. No wood or adhesives at all in the structure below the roof. The foam used in the ICF systems I'm familiar with doesn't seem to bother anybody and concrete is as inert as you can get. You simply shoot the first person who approaches your house with a can of form release oil and that'll keep the rest away.
And install a heat recovery ventilator.
ron
Throw a piece of osb in a woodstove and throw a piece of plywood in a woodstove; watch which one burns hotter. I think you will find that the osb burns a lot hotter, due to the amount of glue used in the manufacture of it.
Having worked in an osb and plywood plant, the osb uses more glue. Just think of the surface area needed for the osb versus the plywood.
As far as the trees used, yes, osb uses smaller trees, but here in Northern Ontario, if a tall straight tree is cut down to make a plywood peeler, the residual is used in a pulp mill.
Greg
Interesting test. I'll have to try that. Do you know the makeup of the glues? Same stuff for ply as for o.s.b.?
Honestly, I can't remember the glue make up, but I know the OSB uses a dry resin that is mixed with the flakes before they are oriented. The press, and heat in the press sets the resin. The plywood glue, on the other hand, is a liquid that is spread on the sheets of ply. The glues may have the same make up, or they may be different. Google may enlighten us!Greg
Scamper,
Following is are quotes from a book called "Building materials for the Environmentally Hypersensitive"
Under the heading of "Construction grade plywood"
"The heat of curing the adhesive under pressure willl release terpenes, extractives and other volatile gasses during manufacture, some residuals of which are slowly emitted subsequently. Lower rates of release of formeldehyde are expected from construction plywood than from manufactured wood products using urea-formedahyde adhesives.Most sensitive individuals find softwood plywood acceptable for interior use if all surfaces are sealed with a laminate or a low toxicity sealant"
"OSB"
"Phenol- formaldehyde, or MDI (Diphenylmethane di-isocyanate) is used to bind the pieces of wood together. Wax is also added during manufacture to inhibit water absorbtion. PF adhesive is more stable to moisture than urea-formaldehyde, producing little formaldehyde emissions when properly cured. MDI does not contain formaldehyde."
from the book "The Healthy House"
"Solid wood can often be substituted, but people bothered by formaldehyde often react to softwood lumber, which contains a tiny amount of formaldehyde naturally."
Regarding plywood
"When used for a roof deck, or for sheathing under siding, the lower outgassing construction grade plywood will be seperated from the living space and it generally won't bother a sensitive person-- especially if the house is very tightly constructed."
"When plywood is used for a sub-floor, it is much closer to the occupants and could bother someone sensitive to formaldehyde. An aluminum-foil diffusion retarder placed between a plywood subfloor and a hardwood finish floor will tend to block the formaldehyde outgassing from diffusing into the living space."
Regarding OSB
"It is slightly more offensive than plywood because it requires more glue to hold the individual flakes together................As with construction grade plywood, it can often be used in ahealthy house if it is well seperated from the living space."
The Healthy House Institute's website is http://www.hhinst.com They have a number of books available, and I would highly recomend "The Healthy House", and "Healthy House Building For THe New Millenium"
"The Healthy House" has a phenomenal amount of information and resources listed in the appendix.
Another book that I found inspirational was "The Healing House" by Barbara Bannon Harwood, from http://www.hayhouse.com
Bowz
Bowz, I think you have found what I was looking for.Thank You
while we're on this subject ...
research the cabinets too.
I have a buddy that's hyper sensitive ... and conspiracy theory minded ... he's looking to be poisoned on a daily basis ...
I don't pay real close attention to his aches and pains ... but he said he was installing alot of a particular brand of cabinet .. William Oh ... and was getting headaches on a regular basis. He finally told the guy he was subing for that he couldn't work with them anymore ... and the dealer said his last guy quit because of the fumes too ...
They called the company ... who said they had problems in the past .. but assured them they already changed the finish formulas so it can't be the cab's causing the problems!
I recently found for the first time myself getting light headed when unpacking a kitchen from Neff Cab's ... had to unwrap them and take off all the doors and drawers off/out ... and let them air out for about 5 minutes till I could work close to them ...
Couldn't stick my head inside one for a good 15 min or so after the initial unwrap.
And I don't consider myself environmentally sensitive at all.
But that stuff really got to me ... first time with any cabinets.
Jeff
Buck Construction
Artistry in Carpentry
Pgh, PA
Jeff,
research the cabinets too.
Most cabinets are going to be made with interior grade plys and particle board. They are made with urea-formaldehyde that is apparently much more potent.
But here is some more of a quote from "The Healthy House"
"The majority of wood cabinet manufacturers also use a urea-formaldehyde clear finish that is significantly more potent than the glue used in manufactured wood products.In fact, these finishes actually generate formaldehyde as they cure, so much so that there is 2-8 times more formaldehyde emitted than existed in the original finish. It is usually referred to as an acid-catalyzed finish, and it outgasses at such a high rate that it tends to decrease in potency by 82-96% after 4-6 months. So it is very potent for several months, then the finish is less volatile."
Bowz
Plywood uses larger, higher value trees that may often be old growth. OSB is made from species that were previously discarded from cut blocks because there was no market for them as dimension lumber. These species include aspen and poplar, both of which can be successfully plantation grown, reducing the dependence on old growth forests. Ditto for engineered wood products like LSL and PSL.
If you're concerned about formaldehyde and other monomers, plasticizers etc., don't EVER set foot inside a new car...if the amount released by curing of OSB in your house is of concern, you'd be in serious trouble if you spent any appreciable time inside the enclosed environment of a new car...concentrations there can be hundreds to thousands of times higher.
There will be far less mass of phenol/urea-formaldehyde in a piece of plywood than in a piece of OSB. And less in a piece of OSB than in a piece of MDF. And none in solid wood. But the environmental impact of the required forestry is pretty much the inverse of that order.
The one post indicated that people are now using MDI (an isocyanate material used in water-resistant urethane adhesives) in some OSB products. I don't know which, but I suspect Advantech, considering its amazing water-resistance. MDI is a sensitizer like all isocyanates- some people can have anaphyactic allergic reactions to isocyanates at mind-bogglingly low concentrations. That said, isocyanates react with moisture and should be short-lived.
If you're concerned about volatiles like terpenes, terpenols etc., then most softwoods are out. These are naturally-occuring volatile organic compounds, and just because something is natural doesn't mean that it's good for you. The converse is also true...
If you're concerned about VOCs in composite, you'd be far better off if you put your effort and money into a good heat recovery ventilation system and making sure you had an adequate number of air changes per hour in every room. There are too many potential sources to control- building materials are just one of them. Better still, supplement the HRV with HEPA air filtration to remove dustborne allergens, smog particulates etc.
I belive that at least some of the "wheat boards" are using non gasing ahesives.
Hrv will definetely be used. We just want to start as "clean" as reasonably possible and work from there. Your'e correct about the new car thing. Terrible smells.
Ask the mfgrs what glues they use. Most of the glues used for ply are probably fairly innocuous, but the stuff used in OSB may be a little more noxious. And the stuff used in "advanced" OSB is likely to be more noxious still.
Exterior glue is likely to be worse than interior glue.
I would think that more glue is used in OSB than in the equivalent thickness of ply, but that's just a guess.
However, most mfgrs have become more sensitive to this issue over the past 15 years or so and likely are making at least a modest effort to minimize VOCs, et al.