Image Credit: Image #1: Lunenburgfirehouse.blogspot.com
More Musings of an Energy Nerd
For the past 30 years, the majority of new homes in the U.S. have been built with wood-framed walls sheathed with oriented strand board (OSB). Most builders are so comfortable with OSB wall sheathing that they never consider using an alternative material.
In fact, a wide range of materials can be used to sheathe a wood-framed wall. In addition to OSB, builders can choose plywood, fiberboard, rigid foam, diagonal boards, and fiberglass-faced gypsum panels. If you’re a dyed-in-the-wool OSB user, it might be time to consider some of the available alternatives to OSB.
It’s sheathing, not “sheeting”
Before we compare different sheathing materials, we need to clear up a common misconception. Plywood and OSB are examples of sheathing, not “sheeting.” The word comes from the verb “to sheathe,” which means to encase something in a protective covering (as a dagger is protected by a leather sheath).
Builders who talk about “sheeting” apparently assume that the word is derived from the word “sheet” (as in, “a sheet of plywood”). These builders are wrong.
Sheathing serves many functions
No one has yet invented the perfect sheathing material. Ideally, a sheathing material should:
- meet code requirements;
- be affordable;
- be strong enough to brace a wall (provide racking resistance);
- hold nails and screws well without being so dense that nails and screws have a hard time penetrating the material;
- be airtight (or able to be rendered airtight fairly easily);
- be vapor-permeable;
- be easy to install quickly;
- be a “green” material that can be produced locally from recycled or renewable raw materials.
If you know of any material that complies with these properties, send me an e-mail.
OSB. OSB panels are made of large wood chips and glue. OSB is strong enough for wall bracing, and holds fasteners well. The main advantage of…
Weekly Newsletter
Get building science and energy efficiency advice, plus special offers, in your inbox.
This article is only available to GBA Prime Members
Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and construction details.
Start Free TrialAlready a member? Log in
49 Comments
Fiberglass sheathing
Martin,
A typo for you. Under the fiberboard heading you wrote:
"This high permeance allows a fiberglass-sheathed wall assembly to dry to the exterior more quickly than an OSB-sheathed wall or a plywood-sheathed wall."
Which is certainly true, but maybe not what you intended to say.
Bill
Response to Bill Dietze
Bill,
Thanks for catching that. The typo has been corrected.
Fiberboard sheating + D.P. Cellulose DOA?
So is the idea of using fiberboard sheathing with deep dense-packed cellulose walls dead? Anybody doing this who would do it again? Use 3/4" fiberboard? Does 16" o.c. framing help?
...Or just run away and keep running?
Response to Bill Dietze
Bill,
No, the idea is not dead. Both projects that I describe worked -- the builders just had to wrestle the bellies back in place. You need to anticipate the problem and pay attention.
One other approach that some people use is to install two layers of furring to create the rainscreen: first horizontal furring (a layer that addresses the bellying problem) followed by vertical furring. That's more materials and labor, of course, but you end up with an impressively well-ventilated rainscreen gap.
Perfect Sheathing
I suppose we'll find a perfect sheathing in the same country that has unicorns and perfect HVAC systems.
I wonder if Huber is working on a "Mark II" version of their insulated Zip system, but I doubt it would meet an affordability criteria.
A rigid foam product with good shear performance, fastener acceptability, and some degree of vapor permeance would be useful. "Compac" foam as a sheet good might fit the bill.
Felt faced polyiso
This is not precisely a sheathing question but seems related; I think it is hard to overestimate the importance of keeping OSB sheathing warm (at least in a cold climate) which is one reason why I prefer loose fill plus a generous layer of exterior foam to double stud walls of equivalent R value (plus it deals with thermal bridging even better than double stud). Consider a 2 x 6 wall sheathed with OSB with a very carefully installed WRB on the exterior of the OSB (taped Zip, liquid membrane, or peel & stick). The idea being to use permeable loose fill in the stud cavities and a relatively permeable foam board exterior of the WRB (plus a ventilated rain gap of course) so that the wall can dry in either direction. Is there a problem using felt faced polyiso as the foam insulation board? You won't find it in big box stores but is readily available at roofing supply houses and it is much less expensive than the foil faced panels (I recently paid $17 for inch and a half R9 4 X 8 panels). I know that polyiso doesn't like to get wet and shouldn't be used below grade but it seems to me it should be okay with the ventilated rain screen and the lower cost will get you closer to double stud in your quest for max R per dollar. I've been to the manufacturer's website and it appears that it is not recommended for walls but I don't know why. My local roofing supply house didn't know either or why one side is labeled "this side up".
Response to Buzz Burger
Buzz,
You're correct that it's a good idea to keep OSB warm and dry, and that exterior rigid foam insulation is a good way to accomplish this goal. If you haven't seen it yet, you may want to read this article: Calculating the Minimum Thickness of Rigid Foam Sheathing.
If you have designed your foam-sheathed wall properly, there will be no need for the OSB or studs to dry to the exterior -- because the rigid foam will keep everything warm and dry. That's why it's perfectly OK to use foil-faced polyiso on the exterior side of a wall. Here's the idea: everything on the exterior side of the polyiso (the furring strips and siding) will dry to the exterior, while everything on the interior side of the polyiso (the OSB, studs, and fluffy insulation) will dry to the interior.
If you prefer to use polyiso without a foil facing, feel free to do so. (However, if you are installing a reservoir cladding like brick, the foil-faced polyiso is preferred, because it stops inward solar vapor drive.)
Your reference to peel-and-stick is confusing. Unless you are building a PERSIST wall without any insulation between your studs, use peel-and-stick with caution (unless it is one of the new-fangled expensive peel-and-stick products that is vapor-permeable). In general, it's safer to choose a vapor-permeable WRB like Tyvek or Typar than a peel-and-stick product for use on the exterior side of OSB wall sheathing. [P.S. For further discussion of this topic, see Comment #17, below.]
We use "Advantech"
Advantech is another Huber OSB product--but unlike regular OSB it doesn't swell when it gets wet--waterproof glue is used. We have had very bad experiences with OSB as wall sheathing--even when cut edges get painted, which they rarely do. Take a look at FHB's study of sheathing from some years ago when they put Advantech in its own category because it was so good. Sure it costs more, but this is the bones of the building. I like diagonal boards too--but our builders groan.
non-foam options missing
Martin,
Although you have a fiberboard section - you've focused on the N.A. derived asphalt impregnated direction and neglected another great set of wood fiberboard options, coming from Europe - two examples:
GUTEX from 475 here: https://foursevenfive.com/the-gutex-wood-fiber-board-primer-vapor-open-continuous-insulation-wrb/
Agepan from PeakBP here: http://www.peakbp.net/agepan.html
They are not structural either but provide very sustainable and fully integrated moisture and thermal protection. We are seeing growing interested in these products.
RIgid foam is given as the only continuous insulation option - but the fiberboards above as well as rigid mineral wool boards by Roxul or others - should be considered along side foam.
Peel and stick.
I've become obsessed with air tightness and I mentioned peel and stick because I suspect that a vapor impermeable membrane is more air tight than a vapor permeable membrane. I would agree that all things being equal the ideal WRB would be air tight and vapor permeable. I am also aware that products exist that the manufacturers claim have those properties. But there are degrees of air tightness and it seems intuitive to me that the most airtight would also be vapor impermeable. If I'm not mistaken, vapor permeability relies on tiny holes -- too small for water to pass but allowing water vapor to pass. Would that not also suggest that very small amounts of air could also pass? I guess the real question is: would it matter? Would the amount of air be so small to be inconsequential? Or is there something different about vapor drive that allows it to work through microscopic openings more readily?
You correctly surmised that the inspiration for this scheme resulted from my reading about the PERSIST system. But it seemed inefficient to leave the stud cavities open especially since I really don't want to use 2 X 4's for exterior walls. So I reasoned that elements of PERSIST but with loose fill added in the cavities would work well, especially in a more temperate climate: air tight as possible at the WRB sheathing plane with windows mounted at that plane (in betweenies), loose fill to the interior side of the WRB and rigid foam to the exterior in an amount sufficient to achieve a total R value comparable to typical double stud assemblies (which would substantially exceed the minimum rigid foam over sheathing requirement).
Finally, wouldn't there be an inward vapor drive in the summer with the AC running in which case vapor impermeability would be advantageous?
PERSIST
Following up on my previous comment to your reply. In your last paragraph you imply that a PERSIST style vapor barrier on the sheathing is only a good idea if there is no stud cavity insulation. But why? The principle of PERSIST, as I understand it, is that the wall can only dry to the inside therefore it is critically important to keep the sheathing and framing dry and warm (in the winter). This is accomplished by the vapor/water/air control layer and lots of rigid foam insulation on the exterior. So what happens when we add cavity insulation? The wall can still dry to the inside (we have been careful not to add a vapor retarder) and, as you pointed out in a recent article, we have provided some hygric buffering potential. What has changed slightly is that even with the same amount of exterior insulation the sheathing is now not as warm even though the total R value of the wall is greater. The wall can still dry to the inside but the possibility of condensation on the sheathing is theoretically greater. So your point is that a vapor permeable membrane would be safer since now we have exterior drying potential. I get that but would it really matter anywhere other than a very cold climate? Plus, if we are going to focus on keeping the sheathing warm (among other things) than this method is far superior to double stud in that respect.
For years I have been collecting building science energy nerd articles, mostly by you and Joe Lstiburek. Went back into my archives and reread Lstiburek's perfect wall article from 2008 in which he suggests putting all the control layers on the sheathing and rigid foam on the outside and, for a residential wall with wood framing, cavity insulation (except in extreme cold climates). Again, I am not talking about code minimum amounts of exterior foam. I'm thinking in terms of 50/50, at least R40 with 20 interior and 20 exterior.
Buzz
If you aren't using the wall cavities for much of your insulation, why don't you want to use 2"x4"s for the exterior framing?
Martin,
You assert (in
Martin,
You assert (in comment #7) that using peel-and-stick is problematic (unless building a PERSIST wall), but also say that foil-faced insulation is fine as the wall will dry to the inside. Wouldn't the peel&stick work fine, too, as long as the wall has plenty of exterior foam to keep it warm? Is there a problem with a PERSIST-like wall that also includes cavity insulation, as long as the ext foam keeps the sheathing warm?
Reply to Malcolm Taylor
I want to do advance framing which in most cases means 2 X 6's @ 24". Plus 2 x 6's tend to be straighter and nicer to work with. But actually, I do want to use the cavity for some of the insulation. Loose fill fiberglass or cellulose has the lowest cost per R value which is why so many super insulated houses rely on thick, double stud wall construction. For various reasons, I don't care for double stud wall. A 2 X 6 wall @ 24" centers with loose fill insulation and 4" of poly iso will have a higher nominal R value than a 12" thick double stud wall with loose fill. Plus I believe it deals with thermal bridging better and therefore the effective R Value will be closer to the nominal. Plus it lowers the risk of condensation on the sheathing by keeping it warmer. Also, it works well with positioning the windows on the same plane as the sheathing which I think has some advantages. At least this is what I have concluded after much consideration. Haven't actually built one this way yet but intend to soon and welcome any opposing opinions from any double stud advocates.
Buzz
That make sense I was just curious. I think though that with the amount of foam you propose for the exterior, I'm not sure the advantages of Advanced Framing are worth the downsides.
Response to Ken Levenson (Comment #9)
Ken,
Thanks for your suggestions.
Very few American builders are using Agepan or Gutex sheathing from Europe, for two reasons: high cost and limited availability.
GBA first published a report on Agepan sheathing in 2011. (I was a guest at Albert Rooks' house in Washington when he took delivery of his first package of Agepan sheathing. It was shipped from Germany, of course. The photo below marks the occasion.)
If these brands of sheathing, or something like them manufactured in North America, ever become widely available and affordable, GBA will include them in lists like this and may consider recommending them.
As BuildingGreen noted in a review of Agepan Sheathing, "Much of the cost is in shipping from Germany. It currently retails in the U.S. at more than $17 for a 25" x 89-3/4" sheet of 5/8" DWD, or $1.10/ft2, and nearly $32 for a 23-5/8" x 74-1/2" sheet of 2" THD T+G ($2.62/ft2)."
As far as I can tell, Ken, from your web site (where your company, 475 High Performance Building Products, sells Gutex sheathing), Gutex must be ordered by the pallet (bundles of 28 or 54 pieces). This certainly complicates ordering and raises the chance for waste. The cost of the product ranges from $19 to $38 per sheet, before taking U.S. delivery charges into account.
I disagree with your contention that mineral wool boards should have been included in an article on sheathing. Mineral wool boards are used as insulation, but not sheathing.
.
Response to comments by Buzz Burger and Dustin Harris
Buzz and Dustin,
It's true that foil-faced polyiso, like Ice & Water Shield, is a vapor barrier. So if you design a wall with exterior foam properly, following the guidelines in my article on the topic (Calculating the Minimum Thickness of Rigid Foam Sheathing), then you can install Ice & Water Shield on the exterior side of the wall sheathing if you want. I think that step is expensive and unnecessary in most cases, but if you want a very good air barrier and a very good WRB, you can use Ice & Water Shield (or a similar peel-and-stick product) in that location if you want.
I hesitate to recommend that approach, however, because it can be misunderstood. (For an example of an owner-builder who installed Ice & Water Shield on the wrong side of the wall insulation, see my article, Dense-Packed Cellulose and a Wrong-Side Vapor Barrier.)
Most builders choose to install WRBs that are vapor-permeable for a good reasons: vapor-permeable WRBs are less likely to get you into trouble that WRBs that are a vapor barrier. But if you know what you are doing, and you include enough rigid foam on the exterior side of the Ice & Water Shield, then Ice & Water Shield performs very, very well.
Reply to Malcolm Taylor
When you say "worth the downsides" are you referring to advanced framing? I am not aware of any significant downsides to advanced framing.
Response to Buzz Burger
Buzz,
There are pros and cons to advanced framing, as this article explains: The Pros and Cons of Advanced Framing.
let's move the needle, not just just provide common practice
Seems a waste to stick to "conventional approaches" - why not also show emerging alternatives, that if more fully adopted would lower prices. There are more options. Agepan is advertised on the home page of GBA, yet can't be included in a blog post?
Also, you are wrong about mineral wool. It can be used similarly to foam boards you show and have been - has illustrated in image 3 of 12 in this GBA blog post - https://www.greenbuildingadvisor.com/blogs/dept/green-building-blog/tale-two-houses
We don't sell mineral wool - you should show it, imho.
Cheers.
Response to Ken Levenson
Ken,
I think that a fair assessment of GBA's role in promoting green building practices would show that GBA has been helping to "move the needle, not just promote common practice," as you put it, since the first day that our web site went online.
Many of the wall construction methods that you seem to favor, Ken, have been extensively covered here on GBA -- for example, in this article (which is #3 in the links provided in the "Related Articles" box on this page): The Klingenberg Wall. We will continue to report on a variety of methods for building high-R walls, including methods using exterior mineral wool, Agepan sheathing, or even no exterior sheathing at all.
Any GBA readers interested in articles on installing mineral wool insulation on the exterior side of walls may be interested in reading the following GBA articles (in addition to the one that you linked to, Ken):
Installing Mineral Wool Insulation Over Exterior Wall Sheathing
Installing Roxul Mineral Wool on Exterior Walls
Wrapping an Older House with Rock Wool Insulation
Mineral Wool Boardstock Insulation Gains Ground
Mineral Wool Insulation Isn’t Like Fiberglass
When selecting materials to include in my article on sheathing options, I made an editorial decision on which materials belonged in this category. In my judgment -- and I believe that most builders would agree with me -- mineral wool insulation is not a sheathing material. That doesn't mean that mineral wool isn't a high-quality insulation material. Mineral wool insulation is an excellent product that can be used to build durable, well-insulated wall assemblies.
the assessment was of the particular post
not the GBA library.
I very much appreciate the wide variety of coverage the GBA library provides - and hope that such individual posts could also reflect a wider diversity of options.
Response to Ken Levenson
Ken,
Green Building Advisor welcomes guest blog submissions. Such submissions can be sent directly to me at this email address: martin [at] greenbuildingadvisor [dot] com. We seek a wide diversity of opinions in our guest blogs.
As you know, Ken, GBA has republished blogs from your web site (475 High Performance Building), with your permission, including these:
Insulating an Old Brick Dormitory
A Straw-Bale Home in Vermont
We also try to publish guest blogs from other sources, reflecting the European Passivhaus approach that is championed by 475. See, for example:
An Insulated Cathedral Ceiling for a European Passivhaus
Five Different High-R Walls
Creating High-Performance Walls
High-Performance Walls, Part 2
High Performance Walls, Part 3
High Performance Walls, Part 4
The bottom line: we're all on the same page here. Keep those comments (and guest blog submissions) coming.
we appreciate being published on GBA
and look forward to the continued dialogue. cheers.
no wall sheeting
I feel like this is a 'stupid' question, but I do seriously wonder why it is that wall sheathing is common practice (required?) in North America, but never (rarely?) used in Australia. I read the list of things that sheathing accomplishes and it does appear that they can all be accomplished perfectly well without sheathing. Not that I am implying that building is done particularly well in Australia. It is actually abysmally poor in regard to energy performance. The use of sheathing over an entire building (walls and roof) is one of the more striking differences in building styles I notice between the US-centric information online and actual practice here on the ground.
Response to A. Lange
A.,
It's possible to build a house without any exterior sheathing, as you point out, as long as:
(a) An engineer designs or approves a method of bracing the walls. (Note that doing this without any wall sheathing can be a challenge in high wind or seismic regions.)
(b) The wall is insulated with an insulation material that is not air-permeable (for example, spray polyurethane foam) or, failing that, a durable airtight membrane is installed on the exterior side of the insulation. (Ironically, one of the best ways to provide an exterior air barrier is to install OSB or plywood with taped seams -- a method that you question.)
(c) The framers have anticipated the needs of the siding installers and window trim installers by installing adequate blocking. (It's quite frustrating to try to nail siding or window trim to air).
Response to Martin
Martin,
I was in no way suggesting I thought it was better to not use sheathing. It seems like such an easy thing to do that accomplishes so many things that are otherwise more difficult. It does save some material and therefore cost and I am guessing that is why it is done, but working on a roof that is not sheathed is slow and scary. Air sealing is only a consideration in the fringe building world, but maybe when that concept is embraced sheathing will be as well. Thanks for your input.
Response to A. Lange
A.,
Thanks for your further comments. I don't know much about Australian construction methods, but I'm guessing that there are two reasons that Australian builders often omit the wall sheathing: (1) To save money, and (2) They don't care about air sealing or thermal performance (because the climate is mild).
Wall sheathing Direction
Are there advantages or disadvantages to installing OSB or plywood sheathing horizontally or vertically?
Downsides of Densglass
Martin,
Other than not holding siding fasteners, what are the downsides of using Densglass instead of plywood sheathing? A (modest) price difference? Is taped Densglass less of an air barrier than taped plywood?
I'm replacing an unsheathed stucco wall and will probably use plywood sheathing (I want no OSB in my house), but I'm curious about Densglass because I'd like to minimize the use of organic materials that can absorb lots of water or rot. I know densglass means that fasteners for the rainscreen material and sheathing need to be in the studs, which increases hassle and maybe labor costs, but I'm wondering if that's the only downside.
My wall would be (inside to outside) drywall, 2x4 framing with bays filled with Rockwool (sound is an issue and I'm trying to minimize wood/cellulose), sheathing (plywood, or maybe Densglass Gold), a highly permeable non-perforated WRB, possibly rigid insulation (1.25" roxul?) , but probably not unless the inspector requires it because the Northern California climate is mild, a rainscreen material like House Slicker or DC14 drainage mat), felt-backed metal lath, 3-coat stucco, paint.
Do you think DensGlass would be a poor substitute for plywood in that application? Also, what do you think of the DC 14? It has low permeability and the channels seem to be intended to create an air gap on either side of the material. I'm not sure if that's brilliant or scary.
Response to Domenico Perrella
Domenico,
I strongly urge you to post these questions on the Q&A page. That way more GBA readers will see your questions, and you are more likely to get feedback from our community of readers. Here is the link: Green Building Advisor's Q&A page.
-- Martin Holladay
Will do
Thanks, Martin. I'll post it there now.
Sheathing (WRB) vs Sheathing (Structure)
The conversation above between Ken and Martin is illuminating, because I I think it gets to some of the confusion one encounters when thinking about high performance walls.
Martin provides a definition for sheathing in his article: "the word comes from the verb “to sheathe,” which means to encase something in a protective covering (as a dagger is protected by a leather sheath)." Despite this, most of the conversation about sheathing implies that it is providing shear strength...
However, in many high performance walls (Klingenberg, Corson, etc) we see that the "structural sheathing" has moved inside the wall and that what we would think of as the "dagger sheath" sheathing (Mento Proclima) has moved outside to the exterior face of the wall (inside the rainscreen)
The funny thing is that a housewrap actually resembles a "sheath" of some sort. As I have expressed elsewhere, I share the concern voiced by many of these unprotected membranes floating outside the wall as the last line of defense to rats, squirrels, and raccoons.
That being said, it seems that we have a distinct set of boundaries: Air Barrier, Water Resistant Barrier (WRB), and, potentially Shear strength layer (Shear layer?). The distinction as to which of these would be akin to a "leather sheath" perhaps leads me to consider that the very word "sheathing" is too vague to be considered a building product category... or perhaps it just needs to be continually qualified, as in "WRB sheathing," "Structural sheathing," etc.
Martin,
I have some questions about the fiberglass face gypsum panels.
I am building a home with a recording studio in Austin, TX and the acoustical designer has specified two layers of drywall on each side of a 2x6 framed wall. The problem is the studio sits on the exterior of the home so half of the walls will be on the interior and the other half on the exterior. To resolve this issue the acoustical designer has specified we use 2 layers of DensGlass on the exterior sections of the studio. My questions are in regards to drying potential of such a massive wall section:
1)If layering two layers of the DensGlass before a water-resistant barrier on the exterior of a wall, should one be worried about the wall being able to dry? I understand that in a hot humid climate, the walls tend to dry both directions so I am curious if by stacking these extra layers of material the drying potential will be drastically reduced (although the sheathing is vapor permeable ~17 perms per sheet). See option A on attachment.
2)Would it make a difference if the two sheets of DensGlass were installed between the stud framing? The benefit of this option would be that the builder would not need to change the exterior thickness of the wall at the studio versus the rest of the house. See option B on attachment.
Thanks,
Steve G
Steve,
DensGlass is vapor-permeable. Stop worrying.
In general, attention to airtightness is far more important than worries about vapor diffusion. To prevent moisture problems in your wall, (a) strive for airtightness and (b) include a vented rainscreen gap between the WRB and the siding.
What about pressure treated, even f it’s just at the bottom? I don’t think you talked about PT in the article but see some builders do use it. Are there any health risks from the chemicals emitted?
Kevin,
If you are a carpenter who handles pressure-treated lumber, you should probably wear a dust mask when you are making sawdust. You should wash your hands with soap and water before having lunch.
I don't believe there are any health risks to home occupants due to pressure-treated sheathing, since occupants aren't in contact with sheathing.
Builders in hot, humid climates (especially climates with termites) often use pressure-treated lumber for framing and sheathing. That's fairly typical in Hawaii and some parts of the Caribbean. For most U.S. locations, however, there isn't any need to specify pressure-treated wood for framing or sheathing.
The way to avoid sheathing rot near grade is to have good water management details: Keep your grade well below the lowest wooden components of the house, build wide roof overhangs, and consider installing gutters at the eaves of your roof. These measures minimize splashback.
Martin: Outside Philly Zone 4, edge of Zone 5. 100+ year old Balloon framed house with Uninsulated 2x4 bays, clap board siding, no house wrap and stucco over the clap.
We added a garage addition with close celled 2x4 bays, plywood sheathing, house wrap and siding.
We are considering replacing the stucco with siding on the original portion, as we have humid summer, and cold drafty winter, interiors.
It will cost me 10-15k to paint the exterior but approx. 35k strip stucco and replace with board and batten siding. For the extra 20k, it might be best to find a longer term solution. Insulating from the inside is not an option.
What would be my best cost effective option be for such a retrofit. Air tighter and Some insulation over what I have now.
I would prefer not to thicken the exterior walls too much, thus minimizing the window flashing issues for any inexperienced contractor. I am not sure if I will easily find contractors who do exterior insulation all that well.
Thanks,
LP
Leonard,
Q. "What would be my best cost-effective option be for such a retrofit?"
A. That's a complicated question. If painting costs you $12,500, and installing new siding costs you $35,000, the additional $22,000 wouldn't make much sense if you are planning to move in three years. Every cost-effectiveness question includes a lot of variables -- including the question of how long you intend to stay in the house.
The only way to answer a cost-effectiveness question is to do the math. If you pay a contractor an additional sum to improve your home's airtightness -- for example, by performing blower-door directed air sealing, or by taping the seams of new exterior sheathing -- the first piece of information you need is a contractor's bid for the work. Without knowing the cost of a contemplated measure, it's impossible to analyze cost-effectiveness. You haven't told us the cost of any contemplated energy-efficiency improvements.
Presumably, when you are talking about cost-effectiveness, you are referring to anticipated energy savings. In order to analyze cost-effectiveness, we would need (a) to know your current annual heating costs, and (b) to estimate the reduction in energy use that might reasonably be expected from any energy-efficiency improvement. (You would use software to estimate this amount.)
For a fuller explanation of these issues, see this article: "Payback Calculations for Energy-Efficiency Improvements."
All of this said, it's hard to achieve enough annual heating energy use savings from an exterior wall retrofit project to result in a reasonable payback. If you are contemplating a major wall project, you will probably do it not because of cost-effectiveness, but for other reasons -- to improve comfort, for example, or to reduce your carbon footprint.
At a minimum, I suggest that you hire a cellulose contractor to install dense-packed cellulose in your empty stud bays as part of your siding replacement. You might also want to hire a home-performance contractor to do blower-door-directed air sealing work on your entire house. For more information on these options, see these two articles:
"How to Install Cellulose Insulation"
"Blower-Door-Directed Air Sealing"
Martin: Maybe I used the word cost effective incorrectly. My boilers are high efficiency but the AC not so much. 6 months a year I probably spend $350 a month on heating or cooling a 4k sft. house.
The house would need approximately 30-35 squares to replace the stucco. The primary reason for change is for comfort. It's too drafty in the winter and humid & hot in the summer. The only reason my bill isn't high, is because my ecobee is highly programmed. And my rarely used 3rd floor is not heated. Any energy retrofit may not save me more than $100 a month under the current setup. Thus, the payback would be 36 years @ 0% interest.
What I should have said is that I need a solution that's not too expensive.
Leonard,
You need to get some bids. Then you (and only you) can decide if the bids are too expensive. As I suggested in my last comment, you might consider getting bids for blower-door-directed air sealing and the installation of dense-packed cellulose between the studs.
Martin: I’m trying to get a blower door test setup in the next few weeks. In the meantime, I’ve bought a thermal camera. In taking the pics and reading I’ve noticed some temp differentials.
Thermostat in the house was set to 70 F
Interior wall temp approx. 68 F for most center of room walls
Day time temp was 48 F
Pics taken at 11 PM with outside temp at 38 F
Basement floor: 53 F
Foamed Basement Joist Bays: 58 F
Read GBA article. Prior to that the bays were almost as cold as the outside temp. And the cold air ran up the walls all the way to the top of the 2nd floor. Thank you, GBA!
Inside of Exterior Walls
1st floor boards: 60 F
Walls: 65 F
2nd Floor boards and Walls: 63 F
3rd Floor walls and Floor: 63 F
I’m the furthest knowledgeable person when it comes to construction, but it’s clear that the coldest area is where the basement wall top meet 1st floor floor board. I’m not sure what more I can do.
Stripping the stucco, adding house wrap, layering XPS/Alternative for $40K seems tough to swallow. Having said that, the sun facing rooms rooms are unbearable in the summer and the non-sun facing rooms are 63 F in the winter. Is there a safe way to insulate a non-WRB balloon framed house?
Thanks Martin for your prior responses!
Leonard,
You wrote, "I’m not sure what more I can do."
Here's what you can do -- if you can (a) afford it, and (b) want to proceed:
1. Hire a contractor to perform blower-door directed air sealing.
2. Hire a contractor to install dense-packed cellulose in your empty stud bays.
3. Improve the thickness of your attic insulation if necessary.
4. Insulate your basement walls on the interior if your basement walls are uninsulated.
5. Install storm windows if your house has single-glazed windows without storm windows.
6. Tell us more about your space heating equipment to determine whether the system is in need of improvement.
1. Hire a contractor to perform blower-door directed air sealing.
underway
2. Hire a contractor to install dense-packed cellulose in your empty stud bays.
- I read in one of articles here that I shouldn’t pack the bays in a balloon framed house that has no air barrier wrap. The house needs to breathe on both sides. Is this not true?
3. Improve the thickness of your attic insulation if necessary.
- Spray foamed Before I bought the house an is actually the same temp as the 2nd floor walls.
4. Insulate your basement walls on the interior if your basement walls are uninsulated.
- with a stone stacked wall that gets moist during heavy rains. Is this a good idea? I going to regrade one of the sides to minimize water seepage.
5. Install storm windows if your house has single-glazed windows without storm windows.
- done last year
6. Tell us more about your space heating equipment to determine whether the system is in need of improvement.
- Hot water radiators. First floor is uncomfortably cold even when the thermo says 70, and 2nd floor is uncomfortably warm at 72-73.
I would love to learn more about board sheathing using 1x6 or 1x8 softwood boards - are there any resources you could point me to? Am curious of the type of wood species recommended, nailing schedule per board, integration of various types of WRBs, etc. Thanks!
Richard,
Here on Vancouver Island a lot of us still form foundations from 1"x8"s, and after stripping re-use the boards as diagonal sheathing. Depending on how high the forms are, y0u can get enough to do most of the house. The boards are going to be protected by the cladding and WRB, so species isn't that important, as long as it is a code approved one. Three nails per board into the studs.
It's pretty labour intensive compared to sheet goods, and you have to watch areas where it butts up to other materials as there can be quite a bit of shrinkage. Apart from that there isn't much difference.
Richard,
The most important issue is approval from your local code official. Unless that code official agrees with your plan, it doesn't matter what anyone else advises you.
In most cases, you'll be using rough-cut boards from a local mill -- so the species depends on local availability. Here in Vermont, the usual species are spruce and fir. If you're using 1x6s and 1x8s, I agree with Malcolm -- three nails per board over the studs.
Your WRB is installed normally, using cap nails.
Our carpenters were happier with doing straight horizontal board sheathing and then adding diagonal bracing separately. On a double-stud wall, the diagonals can be in the space between the two walls, which is a little simpler than doing "let-in" bracing. I don't think diagonal is actually that much more work, but if your carpenters are nervous about it, straight might be an option--subject to your code official's approval, or course.
Most of the builders I work with who do board sheathing prefer diagonal sheathing and white pine from a local mill.
Log in or become a member to post a comment.
Sign up Log in