More Musings of an Energy Nerd
Are some types of siding “greener” than others? Perhaps. But assessing the environmental impact of our siding choices is difficult.
A full environmental assessment should look at:
- The environmental effects of extracting raw materials from the environment
- How much energy is used to extract the raw materials
- How much energy is used to manufacture, transport, and install the siding
- The extent to which the manufacturing process may endanger workers’ health
- The environmental effects associated with the siding installation
- The environmental effects associated with the long-term maintenance of the siding
- The carbon released into the atmosphere associated with each of these steps
(Sharp-eyed readers will note that I have failed to list all the relevant factors in an environmental assessment. But you get the idea.)
Intuition isn’t very helpful here. While it’s true that wood and stone are “natural” choices, that doesn’t necessarily mean that installing red cedar siding or stone veneer has a low environmental impact. For example: do you know whether the loggers who are now cutting red cedar trees are environmentally responsible? Would our forests be healthier if these trees were allowed to keep growing rather than cut down for lumber?
Responsible harvesting or resource extraction is just one element of this type of assessment. Installation methods also matter—in part because installation methods affect siding longevity. Properly installed, stone veneer might last a century—or it might have to be demolished after only six years, if sloppy installation practices lead to water entry that rots the underlying OSB sheathing.
Adopting a wide perspective
For a variety of reasons, I don’t believe it is particularly instructive to base siding decisions on an attempted environmental impact assessment. In my opinion, if you want to be environmentally responsible:
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69 Comments
Is another positive of steel panels that the profile of many common panels can also function as a rain screen, when oriented vertically?
Erik,
Old fashioned corrugated metal roofing would perform as your describe. But most modern profiles of steel roofing have large flat areas that would prevent the movement of air between the cladding and the sheathing unless the panels were mounted on a three-dimensional plastic mesh product like Cedar Breather.
Most companies make a "sine wave" corrugated panel that works great as siding.
What about in a sheathing-less wall?
Like so:
https://pasteboard.co/hYdcM8LEYRAp.png
Erik,
What about them? I've written several articles about sheathing--and even an article about walls without sheathing--but this article is about a different topic. This article is about siding.
With a sheathing-less wall, with modern steel-roofing type panel as siding, will the profile of the panel itself function as a rain screen?
Not intending to derail the discussion of siding. Curious about this exact scenario. In the process of designing an energy-efficient post frame house in climate zone 6. With engineered post frame, the metal exterior panels are a stressed part of the structure. Trying to decide details such as whether or not to use foam closure strips on the exterior wall panels.
Erik,
There are several problems with walls that lack sheathing, including (1) Where is the air barrier? (2) How do you detail a rainscreen that prevents water entry? (3) How do you keep rodents and insects out of the wall assembly?
These problems, and others, are discussed in these two articles:
"Insulating a Pole Barn"
"Insulating a Metal Building"
Thanks Martin. I've read those articles and most of your writings on this site. It has been invaluable and added greatly to my planning process.
Have addressed the points you raise with intentional design features. Will be creating a short presentation in video form. Will post in QA section when complete.
Erik,
As Martin said in post #2, apart from commercial panels similar to Q decking, the only commonly available profile that can function as rain-screens are corrugated panels. These need to be coupled with a ventilated closure strip at the bottom. the easiest way to do this is to use perforated metal stock.
Hi Martin. As promised, I have addressed the points you raise about post frame and walls without sheathing. Could you take a look:
https://www.greenbuildingadvisor.com/question/post-frame-design-details-wall-simulation-rain-screen-pest-barrier-beopt-energy-sim-zone-6b
Erik,
I'm sorry that I don't have time to watch your YouTube video. But a question jumps to mind: if you are planning to build double stud walls, why bother erecting a post-frame building? The post frame is unnecessary. Your wall studs are all you need.
1. Post frame has a pier foundation, which is simpler and uses less concrete than a thickened edge slab or continuous footing. The pier foundation also facilitates a plywood slab.
2. With doubled-up inner trusses, there are only 5 trusses that need to be raised. This can be done without heavy equipment by winching them up the posts.
Would encourage you to watch the video. It's only 10 minutes.
Great, thoughtful piece, Martin.
When using white cedar shingle siding, what is your current opinion on the optimal rainscreen assembly when there is "squishy" insulation (e.g. rockwool or wood fiberboard) between the sheathing and siding?
Thanks!
A. Morley,
I've never tried to fasten cedar shingles onto a wall with a continuous layer of squishy insulation (like mineral wool) on the exterior side of the sheathing.
On my own house, which includes a continuous exterior layer of EPS, I installed horizontal 1x3 furring strips, 5 inches on center, between the EPS and the cedar shingles. That was labor-intensive, but it worked just fine.
Some builders have made site-built SIPs (OSB, continuous insulation, and another layer of OSB). That's not very cost-effective, but it works. One example of this approach is the house owned by Claudia King and Lindsey Tweed in Maine. You can read about that project here: "More Job Site Visits in Maine."
Here's an excerpt from the article:
"The walls were sheathed with new Zip System OSB panels. This sheathing was then covered by a layer of 2-inch-thick polyisocyanurate, followed by a layer of nailbase consisting of 2 inches of polyiso with a facing of OSB. (This second layer of OSB facilitated the installation of the siding.) After the nailbase was up, the crew installed Tyvek, Benjamin Obdyke Home Slicker (to create a drainage layer), and new cedar shingles. The completed wall assembly is rated at R-44."
Thank you, Martin!
I've done both (in fact am the builder the house Martin mentions). Both a pain in the ass, but I'd say just re-sheathing is easier than the strips.
But I also think shingles aren't a great choice in that situation. something that needs wider spaced and regular nailing, like clapboards or vertical, is much easier there.
Thanks for another informative article!
If I do a rainscreen with white cedar shingles on horizontal 1x3 furring only (no vertical behind) over 2" of Rockwool Comfortboard 80, would I still need to vent the top like you would with vertical furring strips? Or even the bottom?
Eliman,
Q. "If I do a rainscreen with white cedar shingles on horizontal 1x3 furring only (no vertical behind) over 2" of Rockwool Comfortboard 80, would I still need to vent the top like you would with vertical furring strips? Or even the bottom?"
A. No and no, in my opinion. The amount of liquid water that will get past your shingles (assuming good installation practices and flashing methods are followed) will be very small, and evaporation through the vapor-permeable shingles will handle any water penetration easily.
Thanks so much for the answer Martin, that makes sense.
Do you recommend against using green WC shingles for siding?
Eliman,
What does "WC" stand for?
I'm sorry, white cedar!
Eliman,
I've never used green white cedar shingles, so I don't have a recommendation on that issue.
A very well-timed post, as I've been struggling to choose siding for my project over the past couple months! I was initially pretty set on wood dutch lap, but keep being told that transparent finishes won't last and it needs solid-color paint -- and it's also more expensive than I anticipated. Just got a quote on Martin's favorite white cedar shingles, which surprised me by being significantly cheaper than wood boards -- but what's the secret to having unpainted shingles look "attractively weathered" rather than "unmaintained and degraded" -- or is this more of a regional thing, where the "look" fits in New England but wouldn't really work on a midwestern suburban ranch?
Jonny,
If you think every shingle on your house will always be the same color, choose another siding. As the shingles weather and age, they change, with colors varying depending on rain exposure and sun exposure. Every 20-year-old house will look different.
My observations lead me to believe that color changes due to weathering are mostly due to rain exposure -- and only to a lesser extent to sun exposure. So anyone interested in slowing cedar shingle color changes from weathering should design a house with wide roof overhangs -- which is always a good idea for half a dozen reasons.
Some of us love the look of weathered shingles; others don't. If some of the photos shown below look bad to you, maybe you want another type of siding.
Yes, you're exactly right on water and color, Martin. And the south side will look dramatically different form the north side after a while.
I'm asking myself why we haven't designed shingles on houses--I love the natural weathered look! Starting to look at sourcing in Chicago--maybe not ideal from a local-source perspective, but we don't have a lot of options since we cut down Michigan couple hundred years ago...
Hi Martin: I agree with most of your post; use unpainted wood; ideally local, over a rain screen, with wide overhangs. My one, admittedly minor points is that wood always rots. Yes it does, but there are houses here with the original feathered end clapboards, used in the 1700s and early 1800’s still intact. Lots of paint layers, but it’s holding up just fine. House is likely uninsulated or poorly insulated, but that’s another disvussion,
Bob,
Fair enough--you're right. If kept dry, wood lasts virtually forever. Tutankhamen's wooden throne is over 3,300 years old and is still solid.
Good design requires wide roof overhangs and protection from splashback problems by keeping the lowest wooden components of the house at least 8 inches (and ideally, at least 12 inches) above grade.
I'll edit my article.
Great article, Martin. As usual!
I agree with your take on EIFS, we've tried a couple of projects with 'drainable' versions and you can still mess them up. In fact we did a multi-hundred-thousand-dollar repair project on one of these. The installers were to use notched trowels to make vertical drainage paths behind the foam, but they did the 1' band at the bottom of the wall horizontally...
I never loved the engineered wood stuff but I talked to the guy who tested SmartSide in Hilo, Hawaii where it stood up to 100" of rain and tropical termites. It doesn't seem to be failing like its predecessor, which grew mushrooms within a couple of years of install in many cases. Whether it will hold up for decades is anyone's guess, mine is no, but who knows. Fiber cement has an imperfect record especially in climates with freeze-thaw (though Hardie, installed reasonably well, has done fine here in the DC area), and today's wood isn't that awesome either, so as you point out, you pay your money, you take your chances.
I didn't believe the hype about rainscreens making paint last longer, but ended up installing one on part of my own house, furring strips over foam board. It's been twenty years and the paint is holding up really well. This on 6" western red cedar clapboards. Anyway I think paint can hold up OK, and airspaces behind siding really help.
I've seen the same issues with brick as with other masonry claddings for what that's worth. We're repairing a bunch of rot on a house right now where the brick work is the culprit. Through-flashings, drainage, and drying are 100% required with reservoir materials.
Douglas,
Thanks for sharing your valuable and extensive experience. Your example of a brick veneer failure reinforces my emphasis on attention to details during installation -- a crucial factor with any type of siding.
Thank you Martin, as always.
Can I ask if you have any general advice for, or cautions towards, open (with 1/8 gaps) horizontal wood boards installed over a rain screen and vertical furring strips , assuming over hangs are large, they are off the ground sufficiently, and they are left unpainted?
Cameron,
I don't have any direct experience with gapped open siding, but instinctively I don't like it. In most cases, siding is your first shield against water entry. If the siding has deliberate open gaps, you're giving up on that function. At that point, you are depending entirely on the WRB to keep water out of your wall assembly (instead of having two layers of protection against water entry -- the siding and the WRB -- as you would typically have with most siding types).
With this type of gapped open siding, you also have to worry about critter entry (insects and rodents).
Thank you. I understand those concerns, plus, after thinking, UV deteriorating said WRB.
I also like the idea of vertical shiplap, have you written about using vertical siding over an air gap and rain screen at any point? Would you point me in the right direction? Considered along side 2x6 walls with 2 inches of added exterior insulation.
Hi Cameron: we’ve used vertical shiplap siding several times with a horizontal rain screen (1x3 or rough 1x4). We typically install some type of drainable fabric on the sheathing first. Works great; the shiplap dries on both sides so it doesn’t cup.
Thanks, I'll also consider this!
We've done vertical board & batten over drain-mesh material (cedar breather in that case) and it's awesome. No cupping, finish has held up, had a missing kickout flashing but the wall dried all the water without issue.
Cameron,
The concerns Martin brought up - in particular moving the hard lifting from the siding to the WRB behind - are why our building code does not allow open cladding here in BC. Gapped siding allows a surprising amount of moisture to get through from the exterior: https://www.rdh.com/wp-content/uploads/2017/10/RDH-BSL-Drainage-Balance-Spray-Rack-Report.pdf
All that said, with its increased popularity manufacturers have come up with more robust WRBs for use behind it. If you decide to go that route, using one of theses specialized versions is good insurance against bulk water infiltration.
Thanks for all comments. Stalking other blogs and questions I have found several declarations from Martin that he, personally, doesn't see a problem attaching the vertical siding directly to horizontal furring strips. I must say that sounds rather ideal to me!
Any opposing thoughts?
Cameron,
It would be precluded by the rain-screen requirements here in BC, which says you need a continuous drainage plane and air gap. Codes aside, you still get most of the important attributes of a rain-screen with horizontal furring. You can also mitigate some of the concerns by either using ventilated furring like Cor-a-Vent, or beveling the top of the wood furring strips to channel any water to the outside.
I too love eastern white cedar shingles, and here in Maine there are two mills (Dow and Longfellow) that make a version with 5/8" butt as opposed to the normal 3/8. It looks fantastic, and presumably will last even longer that the thinner ones.
Dan,
That's beautiful!
Near me on Vancouver Island they used to make shakes with 3/4" butts. After 20 years or so some owners would take them off and reverse them for another couple of decades use.
I was a house painter in the 70's in a coastal area so I saw my share of siding and all have strengths and weaknesses. This is a good article because it addresses a broad array of characteristics, including environmental issues in manufacture, imbedded energy and durability and longevity of the siding.
I saw you did not include "real" wood T-111 plywood siding. With a rough surface it holds paint (or solid color stain) well. My T-111 sided barn hasn't been painted in 25 years and still is bright red.
Also, I think fiber cement siding holds up well if installed correctly. I am curious how much cement is actually used per square foot.
Nick,
Q. " I am curious how much cement is actually used per square foot."
A. I did some Googling. According to one site discussing James Hardie siding, "Fiber-cement siding can weigh as much as 300 lbs per square (100 square feet)."
According to another site, "Fiber cement board siding primarily consists of cement, cellulose fibers and sand, according to the Portland Cement Association. ... Cellulose fibers compromise as little as 10-15 percent of the composition of fiber cement. ... One popular manufacturer’s best-selling, medium-density fiber cement siding consists of approximately equal parts of cement and sand. On the other side of the quality spectrum, low-density fiber cement siding contains more sand than cement. Some low-density products contain as much as 60 percent sand by weight."
So, a high estimate for one square of siding would be:
Weight of siding: 300 lbs
Percentage of siding consisting of cellulose: 10%
Percent of siding consisting cement and sand: 90%
Percent of siding consisting of cement: 45%
Rough guess of weight of cement per square: 0.45 x 300 lbs = 135 lbs.
Martin thanks for this excellent round-up. I'm pretty partial to steel siding due to its strength and longevity but have been wondering if its embodied energy is high (high enough even given its long life span)--I'm curious whether it has much recycled content, and if the Kynar finish is also nasty in manufacture. Any thoughts or sources to turn to for info?
Tom,
Most of the painted metal panels I buy aren't Kynar coated. That's a premium upgrade from my supplier. Depending on the colour it may be worth it as it doesn't fade as quickly, but from a longevity perspective the regular finish protects the metal just fine.
The majority of the metal siding I use are just either galvalum, or if it's going to be in proximity to ACQ treated wood, galvanized.
Thanks Malcolm--I'm going off memory of the Pac-Clad or Berridge samples, and what I recently used on my house came from Menards, through Midwest Manufacturing. They JUST told me their material is "minimum 65% recycled" which sounds good to me. I'm waiting for the BEAM calculator to come out so I can see what this means however it will be calculated, like btu/lb of material...
Tom, most steel has a high recycled content. I'm betting that other steel manufacturers will have similar percentages.
"Almost 69 percent of all steel is recycled in North America each year – more than paper, aluminum, plastic, & glass combined. North America's average steel recycling rate has been in excess of 60 percent since 1970."
Thanks Nate--I thought so but didn't know how much it might vary by locality etc. Can I ask where you got that quote?
Tom, just google searched and that quote was at the top. Apparently it came from here: https://www.nationalmaterial.com/steel-and-recycling-fun-facts/#:~:text=Almost%2069%20percent%20of%20all,in%20North%20America%20is%20recycled.
Given that (I assume) roofing steel isn't anything super special as far as the alloy, I assume there's a few mills that produce the raw rolls, and they get train cars of shredded steel scrap that gets mixed into the melt. So it's probably fairly consistent as far as the percentage.
I spent a little time working in the metal recycling industry....amazing process to take our old cars, appliances, etc, and break them down into small pieces, separate the materials, and ship it to mills for reuse.
Interesting. That is more than I suspected. A decent sized house could contain a ton of cement. Thanks.
Wood siding gets eaten so fast here in SC by carpenter bees. It just becomes a hotel in no time. Any thoughts on preventing that? Paint doesn't seem to help much if at all either. I pulled it off a house I lived in and there was barely anything left. Maybe carpenter bees aren't a problem up north?
Glenn,
You guessed correctly: carpenter bees aren't a problem up north. (Yet.) You should seek local advice.
Carpenter bees are a problem in Michigan. They've been trying to get into some redwood (reclaimed from a job) on my porch for years. This year one went unnoticed too long and a woodpecker found it before I did. I've got some repair to do now.
Photo didn't load last time. It hurt when I found this. I swear it only took the wood pecker one day to do that.
I am in North Jersey and there are plenty of carpenter bees that like to eat my cedar pergola. We are about 150 miles south of Southern Vermont-they seem to be getting worse with mild winters, although I haven't studied the issue carefully.
Thamby Kumaran. [email protected] Has any one considered the environmental impact of Shou sugi ban? Using fossil fuels to char the surface?
twk1234,
Eric Whetzel brought that up in his blog: https://www.greenbuildingadvisor.com/article/urban-rustic-the-cedar-siding-is-here-lets-burn-it
Very informative, thanks Martin. I have a house located in a coastal marine environment and have been looking at engineered polymers. Am I correct in assuming that they have a negative environmental impact during manufacture? From what I've read, the product should last for quite a long time relative to white cedar which is very attractive.
Mark,
I don't know the answer to your question about "engineered polymers" -- in other words, building materials with a high content of plastics. The manufacture of plastic (including PVC) usually starts with fossil fuels and can be a nasty process for manufacturing workers and for the environment.
Constructing a building has an environmental cost, because the manufacture of almost anything requires energy and the release of CO2, and because delivering materials requires trucks, and because construction workers commute to the job site in cars. Almost anything that costs money pollutes the planet. If you swap one building material for another, you might be lessening the environmental impact of your construction project -- but the best thing you could do would be to stop building.
I understand the permanence of using paint on wood siding, but what about the various sealants - natural and otherwise? I'm located in an incredibly dry environment in central Wyoming, and have high drying potential year-round (and lots of sun and wind). Would any form of sealant be necessary for my local options, which would include red cedar, fir, and pine?
Aaron,
Most opaque coating offer little UV protection - and it sounds like you live in an area where that is the primary factor in wood degradation. You can leave wood to age naturally. That's what you see in old westerns, or barns in New England, where the siding is grey, dry and checked. It often still does its job, but neither moisture of sunlight are beneficial to wood.
Malcolm, just a detail here, but I think you mean that transparent coatings don't offer much UV protection. Most transparent coatings do now have UV inhibitors built in, but I've got no idea how long they last. In the wet and humid northeast, most transparent coatings need refreshing even more often than paint, and they still allow some amount of color change and weathering. I've worked with several homeowners who were unhappy when they found out that there was no real way to preserve that nice buff-tan color of new shingles.
My advice has always been similar to Martin's. If you want wood siding to last forever, install it right and paint it on all 6 sides. If you like the weathered look, then don't paint it. Unpainted wood can last 30-50 years in our climate if well detailed, sometimes longer. Painted can last forever, but needs repainting. I have no data to support the following, but IMVHO, the lifecycle cost of painted (with rare replacement) vs. unpainted (with periodic replacement) is probably about the same.
Peter,
Thanks for spotting the mistake. That is indeed what I meant. The PNW is full 0f beautiful wood framed projects that look great for a year or so, but quickly lose their new appearance and as you say darken or discolour, leaving the owner with the unpalatable choice of just living with it, or devoting a couple of their summer weekends each year to trying to battle it. That's one of the main reasons I try not to design deck into projects if I can help it.
Aaron,
Dry beats wet any day. The fact that you live in a very dry environment is good news for the longevity of your siding. If you don't mind the appearance of weathered wood, enjoy your siding without worrying about coatings.
Sounds good to me! Thank you.
Martin, I live in southern VT and have used vertical shiplap on another home, and yes the painting cycle stinks. Would you recommend a stain or other non-paint protectant?
Michael,
No.
Thanks very much for the informative article. I like the idea of softwood boards, but I have three questions that I can't seem to find a good answer for:
1. Why do you specify that softwood boards be installed vertically? Are there specific advantages of vertical vs. horizontal orientation of wood siding? I have read elsewhere that horizontal installation is cheaper, but may be more prone to moisture issues than vertical, because of water seeping up between boards. Any other insight on this?
2. Do you have any experience with live edge siding (aka wavy edge, brainstorm, or flitch siding - see example picture)? This approach seems to typically use pine (though can be oak, cedar, or others), and offers a more natural and rustic look, though I’m not sure whether it comes with any disadvantages in terms of performance.
3. Regarding the “original sin” of paint, is this true for wood stain and/or finish as well? I have read contrasting opinions on promoting the longevity of wood, with some sources suggesting routine maintenance with protective finishes, and others suggesting the boards be left completely natural for their lifetime. Is this mostly an aesthetic issue, or are there clear implications for durability and performance as well?
Thanks for any light you can shed on this topic! Writing from southern Wisconsin, by the way, in case it's relevant...
OMG I love this article for both its content and how it's written!
AUTHENTIC purified linseed based paint, stain, wax and varnishes, as well as authentic organic pine tar, are all excellent alternatives to paint for wood siding - though these finishes can be used on almost any material, which is just amazing to me. Linseed oil is made from organic flax seeds, and is 100% chemical free and safe for the environment.
They are truly amazing products that don't just cover the surfaces, they penetrate and protect them and last FAR longer. The links below provide more info. I'm not connected with this company at all, I've just learned a LOT from them and am planning to use linseed oil paint, wax, stain and the linseed oil pine tar mixture on my next home both inside and out as a paint alternative for literally all of the benefits they offer, but most notably for me, the absence of toxins and longevity / protection / low maintenance aspects are game changing IMO.
http://www.solventfreepaint.com/index.htm
http://www.solventfreepaint.com/faq.htm
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