I am close to the framing portion of my home build and I am curious if dense packing or damp spray cellulose is better for filling a double studded wall? I have only seen damp spray on TV and Youtube etc. I have used dense packing before in existing homes, but never in new construction. Again on TV I have seen installers staple up a see-through fabric and dense pack behind that... is that better than doing it after the wall is sheathed?

For double studwalls dense packing cellulose is important, and there's a real learning curve to dense packing walls that thick with a sufficiently consistent density. It might be easier to dense pack fiberglass in double studwalls- the jury is out on that.

In some dense packed double-wall or truss projects people have used insultion web at each truss, dividing the wall up in to 16" or 14" long sections to make it easier to achieve consistent & high density.

Using blowing mesh on the interior side prior to installing the wallboard is fine, but it has to be rolled flat to the stud edges after blowing to get a reasonably flat wall. Mesh pillows out quite a bit at 3.5-4lbs density.

I'm at the foundation portion of mine right now and I'm also going to be doing double wall framing (staggered stud 24"oc, 2x8 top plate). I'll be going the route of spraying on closed cell foam (R-5.5) for the first 2" (should be great air sealing and keep moisture out) and then using dense packed cellulose (R-4) for the remaining 5.25". This will give me a total R-value of R-32, without factoring in drywall, sheathing, moisture barrier and siding.

A 2x8 top plate is a significant thermal bridge through R33 of insulation. Is it too late to change the framing specs on your house? How wide/thick is the foundation?

Dense packed cellulose never quite hits R4/inch. Figure on R3.7/inch at 3.5lbs per cubic foot density.

Note, 2" of closed cell foam is thermally bridged by the exterior set of studs, it's high R/inch performance isn't buying you much (less than R1 in "whole-wall-R" at typical framing fractions compared to an all open cell or all cellulose cavity fill.) Closed cell foam also has a huge global warming footprint due to the HFC blowing agents used, and it uses about twice the polymer per R of half-pound open cell foam (R3.7 /inch) which is blown with low enviromental impact H2O (water).

At 2" of thickness 2lb density closed cell even uses more polymer than if you did the whole 7.25" with half-pound open cell foam. At 7.25", half-pound foam would also air seal better than 2" of closed cell foam. It would probably cheaper than just the dense packed cellulose part of your proposed solution too, let alone the 2" closed cell + 5.25" dense pack.

Here’s what the PHIUS/PHPP Certification guide has to say about double stud walls based on field test, creditable CFD modeling, ISO 13790, Footnotes 9/10 to BSC design guides.

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Things to Avoid

Exterior load-bearing double-stud walls are discouraged in climate zones 3 and higher. These

will generally incur additional certification cost for hygrothermal analysis (WUFI), need a spray

foam global warming potential (GWP) impact calculation, or both. They tend to be too vapor closed on the outside for those climates and also put the air barrier on the exterior where it will

be less durable than a mid-wall air barrier.

 In heating dominated climates, double stud walls should be of the interior load-bearing type, either Larsen truss (standoff truss) or the kind described in [9], [10].

Now you just have to figure out what is meant by “vapor closed”.

Here is an instrumented field study giving hints,

http://www.smtresearch.ca/case-studies/passive-house-performance-monitoring

https://fpinnovations.ca/Extranet/Pages/AssetDetails.aspx?item=/Extranet/Assets/ResearchReportsWP/3100.pdf#.WRbraGjyuUn

Note that component level transient effects based on thermal inertia's and interstitial vapor partial pressures drives are the failure modes. Highly insulated walls pose more risk of the outer layers exceeding “MAX Moisture Content” MMC, as in the case of the north wall during winter. That depends on a lot of factors like directional loads (solar radiations(s), wind driven rain, snow, freeze-thaw, dew, fog salt).....and not just r-values taken from code or blind guessing.  For wood, MDF, MC above 15% depending on time based boundary conditions possess risk of rot/mold if heat and food is present. 100% RH coupled to 15% MMC is risky and many far exceed this... far too high.

“On the other hand, the partial vapor pressures were largely consistent across the north-facing wall in the winter, not showing a strong vapor drive from interior to exterior in this mild climate. “

So, there is the “vapor closed” answer in part, and risk associated with dbl studs.

To avoid this, one has to conduct a vapor partial pressure analysis (not by perm rating alone) to determine gradients at each component layer, based on whole building design-build, and again calibrated sensors producing artifacts to these models/builds. THERM 6.3 did a decent job here, to get PHIUS certified WUFI 3.1, a much more accurate CFD, is required to pass PHIUS pro design-build inspections.

Too bad the heat flux density sensors did not work. Instrumentation Engineering can be a challenge. I’m conducting HVAC hot box testing now. That would have verified effective hygrothermal u/r-values, wet being the highest risk.

Quasi-steady state r-value/perm rating done by internet green site designers is never going to be able to do this type of risk and validation analysis period! 

·        The protocol for thermal bridges is in ISO 13788, THERM or WUFI algorithms calculated prior to construction. A PHIUS “hard requirement” is ONE impact on space condition loads but, as importantly on mold growth at the interior temp RH point. The loss is calculated by the hydrothermal heat/gain ratio, time constant, depending on the internal heat capacity and total heat loss coefficient of the building.  For the time constant equation, a continuously heated building (more than 12 hours per day) is considered. The total heating demand, including the transmission heat losses for all components and thermal bridges and the ventilation heat loss is decreased by the total heat gain comprised of the solar and internal heat gains, multiplied by a utilization factor. Monthly heating degree hours are determined multiplying the hour count of the month with a temperature difference.

rrrr Another metric is per ISO 13790 is Predicted Mean Vote PMV/PPD Predicted Percentage of Dissatisfied, indoor comfort calculations to determine zonal overheating/RH.

 Of course there’s a whole more to it,

The last thing I suggest anyone does is re-design just because some joker wanna-be-green designer on the internet says so. There is also a certification protocol for embodied energy. Find a real  pro that knows what they are talking about before you waste A LOT of time and/or money.

 As Internet of Things (IOT) BIMS protocols, as the use of life cycle management validation instrumentation's like this passive home matures, there will be less guessing & higher quality lower cost homes, as can be seen is well underway outside of the US migrating here. Component and systems level properties, requirements, will be validated prior to & during construction, and for the life of the building. Further, the visual AHJ/Rater/certification inspection process will be done in the IOT cloud, based on data, not hersay!

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Dana,
How is the top and plates a significant thermal bridge? Take a standard 16" oc studwall, no openings and the total framing fraction is 15% wall area, eliminate the studs and the plate framing fraction with 3 plates is 5%. I'd call that pretty good especially given the speed of assembly. Double stud wall will lose some square footage and almost double your framing time. Better yes, but hes not proposing a ridiculous plan.

And Para, I see your trying to score some consulting work, good luck with that. Work of advice from someone who has worked with hundreds of homeowners, you need to dumb down the posts, we all know you're the expert, you dont need to fluff your tail feathers on every god d*** post.

greentree: Typical 16" o.c. framing fractions in the real world (you know, the world houses that have windows & doors... :-) ) are in the 25% range, not 15%. (Multiple surveys of real world construction designs prove the 25% number. It's even higher where fire blocking & seismic resilience are required by local codes.) It takes a pretty careful design to get it down to 15% even with 24" o.c. spacing.

A square foot of 2 x 8 edge conducts about as much heat as 3.5-4 square feet of R33. If the plates add up to 5% of the total face area, it's well into a double digit percentage of the total heat transferred.

Ummm, dana, sure took my post out of context and made a deal out of nothing for this guys plan. I should have calculated a typical wall which can run low 20's to 30 or more, depends on too much to mention, so my bad for giving the house nerd some bait. He's miles ahead of standard, so the plates are a nonissue, the design is cost effective, the fancier you get the more youll never get your money back. The guys not going to move into his house and have cold feet cause he used full width plates.

Just remember, there are alot of comfortable code built houses, comfort is king so its about reducing operating cost, how much the particular method of reduction costs and what it saves.

Ive noticed as someone who learns and practices building science priciples as well as builds actual buildings with real world carpenters, a lot of the building science discussions and consumer concerns are picking the fly sh*t out of the pepper in the big picture.

Posted By greentree on 17 May 2017 12:24 AM
Ummm, dana, sure took my post out of context and made a deal out of nothing for this guys plan. I should have calculated a typical wall which can run low 20's to 30 or more, depends on too much to mention, so my bad for giving the house nerd some bait. He's miles ahead of standard, so the plates are a nonissue, the design is cost effective, the fancier you get the more youll never get your money back. The guys not going to move into his house and have cold feet cause he used full width plates.

Just remember, there are alot of comfortable code built houses, comfort is king so its about reducing operating cost, how much the particular method of reduction costs and what it saves.

Ive noticed as someone who learns and practices building science priciples as well as builds actual buildings with real world carpenters, a lot of the building science discussions and consumer concerns are picking the fly sh*t out of the pepper in the big picture.

Well put. Dana Dorsett is FOS most of the time. It's hard for me to grasp he has a degree other than HS. Anamag777 nor Loghomebuilder didn't even specify what climate zone they are in, nor internal set points for starters before he's dishing out the BS trying to get people confused enough to think he knows what he's talking about, no references to his builds, test, specs. He comes out here recommends someone redesigns w/o knowing alot of factors that determine thermal bridges that could cost lots of money and degrade structure (something he knows little about too).

He's not even close to the most probably locations. He has no real numbers to speak of, only a bunch of BS that does not matter. Thermal transmissions do not boil down to a simple framing factor. He did bite your bate and I knew he would, good job. Comparing the dynamic flux of wood & insulation is even dumber!

What we have here is a bunch of "advisors", some can't even live up to college degrees, PHDs, moreless basic HS physiscs, etc, that have ruined the "Green" name by sitting behind a computer all day with massive internet visibility trying to make a name for themselves, dishing out BS to get sponsored, sell insulation, especially foam, without disclosing the risk with high levels and air tight construction, protected by site legal disclaimers unlike "real" design-build pros. Dana is well protected on GBA by Martin Holaday, another clown! If you were to check into their credentials you'll find most have only built their own homes and much of their advice has not been applied to them, have no design or build companies with REAL skin in the game, like dealing with clients, AHJs, subs/employees, nor have experienced all the headaches in designing-building-selling-inspecting customs or specs that profit, have nothing in the field proven to qualify them as "International Advisors". If you were to check the cost that they also rarely discuss or know, it would make no sense to the HO's pay back.

It's high time people that know better bring these rats out to public eye so people know the truth.

Even if your not fancy with words or Building Science but learned something and applied w/risk to your business & reputation, or home, lost some clients and money in the process, learning from your costly mistakes, your way ahead as a local advisor than these jokers! Good job!

Posted By greentree on 17 May 2017 12:24 AM
Ummm, dana, sure took my post out of context and made a deal out of nothing for this guys plan. I should have calculated a typical wall which can run low 20's to 30 or more, depends on too much to mention, so my bad for giving the house nerd some bait. He's miles ahead of standard, so the plates are a nonissue, the design is cost effective, the fancier you get the more youll never get your money back. The guys not going to move into his house and have cold feet cause he used full width plates.

Just remember, there are alot of comfortable code built houses, comfort is king so its about reducing operating cost, how much the particular method of reduction costs and what it saves.

Ive noticed as someone who learns and practices building science priciples as well as builds actual buildings with real world carpenters, a lot of the building science discussions and consumer concerns are picking the fly sh*t out of the pepper in the big picture.

The context here is Animag771's staggered stud 2x8 wall with 2" of closed cell foam, etc, not loghousebuilder's double studwall.

Fair enough, the thermal bridging of the plates is a nit in the overall picture of the proposed wall. We don't really know what his local code-minimums are, or his location. But the closed cell foam & extra depth isn't buying Animag771 very much in any climate, and undercutting the performance with more thermal bridging at the plates buys even less. His proposed wall reads like a case of "... the fancier you get the more youll never get your money back...", more expense & complexity for little to no gain.

It's not all all clear that "...the design is cost effective...". The staggered stud wall with the 2" of closed cell foam is barely higher performance than a cheaper & easier to build 2x6/R20 + R5c.i. wall, IRC code-minimum for zone 6 & higher. In a milder climate even the 2x6 + R5 wall might not be cost effective. Staggered studs add complexity, and the 2" spray foam adds considerable cost for minimal or no benefit. But even the staggered stud wall would be cost reduced by insulating it all with open cell foam or all cellulose, rather than a 2 step approach with 2"foam then dense pack, without taking a significant performance hit. Whether he needs to add anything to lower vapor retardency toward the interior with those options depends on other factors, but just about anything would be cheaper than 2" of closed cell foam.

My cost effective comment was geared towards the frame, I missed the part about the spray foam and agree that part of the assembly rarely if ever would be a cost effective candidate other than very specific circumstances in certain areas of a building.

I think a staggered stud would be easy, fast and cheap to platform frame, be worth looking at and would reduce thermal bridging over a standard frame by a large degree, however Im not going to model or do load calcs so take it as my opinion.

Dana, or anyone, have you seen or heard of Steve Romme's modeling results as it pertains to payback? He's a consultant, I believe from WI, he kind of takes all the high performance menu items and dumps them on the floor and makes you think before you start filling up your basket again as it relates to your wallet, anyways try to find his p. Point slides with his results, very interesting stuff but again financial based, not necessarily comfort based.

Payback or a better term is "annualized cash flow" is meaningless to local markets unless it is realized by banks & their appraisers, valued by clients, understood by agents, which 9 xs out of 10 they don't & won't. Anyone that has tried to negotiate green design-build firm specs knows this. I have net zero designs with positive cash flow from year one. I have perm cash flow or portfolio financing for from one of the few regional lenders, local construction is much more difficult. Dumb DIY or rich cash buyers that don't care don't count nor start/grow a comparabes market, banks do. Can't separate peoples wallet from comfort. BEOPT is free and does tech financial modeling well. Don't listen to any advisor until the financial model is optimized and they are just as complex if not more than the tech. The best designers know financing well and show the numbers, just like tech. If you don't see pertinent numbers it's BS!

With all thats going on with US and CAN and the inflated price of lumber, and with incomes that can't support most new construction in most locations begging for affordable homes with decent SF (1200-1500+) conditioned space below $250K close to metroplexes, dbl framed footprints make no sense at all. Spray foam is not going to make or break this designs bank, another moot point, it don't matter there are much bigger fish to fry. The only stick construction that does make sense in conventional 2x4 with cheap FG insulation, non insulated foundations, or some non-wood design, unless a high performance envelope portion of total cost can reduce multi-zoned HVAC and levelize total cost. I most cases in cannot and the HP home will cost 5-10% more initial cost, again most market won't support or appraise or has anything to compare.

Most locations are not producing massive highly insulated homes for these reasons. 9 xs out of 10 people choose aesthetics over comfort and comfort is very subjective...cant take it to the bank or put value on it, nor can healthy, low embodied energy, homes be sold to the massives unless they are competitively priced which is impossible in most medium income based markets the bulk of the market. Anyone trying to sell these homes knows this. GBA and some of these people selling them from their computers don't tell people all this, nor practice what they preach, nor the many other risk technically and financially.

Dana & Greentree, heres a screen shot of one of smallest net zero stick frame specs and I have many others. Lets share and compare. Post yours? I also have my cost we do in exactimate exactimate bids we give our clients. Lets share that next too. Love to see your designs and cost.

Greentree: " however Im not going to model or do load calcs so take it as my opinion. " I'd like to see your FEM/FEA approach here on any framing? And how it factored into your cost? Not needed when you follow code.

I design all my homes in WUFI including the energy and moisture management first. Then do the interior and rendering in Chief Architect Premier X9, however, I have a license w/ current SSA for sale since I am switching to CATIA 3D Experience so I can model MEP better and simulate the build using Delmia, process using BIMS. Love to hear about your design processes too. BTW: That is dbl stud construction above, high performance cost optimized with financing in place. Love to hear about your green lending too?

Take a close look at the frame render you posted. It sucks, go into plan view, right click on a wall and go to wall elevation detail. There you can add remove framing members and import framing plans into your layout file. This also updates the built in materials estimate for quantity allowing you to make OVE framing plans, but you knew all of this already Im sure.

Models and modeling simulations doesnt transalate to success when its built, you need good plans, which your obviously lacking with your ametuerish plans. Double stud wall but 2x4 fire wall to garage, nice work smalls.

First off I agree with your first reply regarding consumers, banks, the industry, where we differ is you are trying to operate outside those constraints and I am operating within. I dont go balls out with this stuff because it doesnt offer me a return and I would go broke. Im a fan of the "pretty good house", that's scaleable and realistic.

I'll help you out with your example plan, to make your abomination a bit more saleable I would suggest:

1. a 4/12 shed porch roof between the master and garage with a standing seam roof to help out your curb appeal and break up your mass of shingle.
2. Change the front gables cladding to shake or board and batten, people eat that up.
3. Flip your main bath fixtures to share a common plumbing wall, especially since your on a slab, that will certainly bring down your rough in costs Im sure you have in exactimate (which is an insurance restoration estimating platform, there are better options for building)
4. Flip the master closet so the bath door comes into the vanity, no one wants to open a door in front of a toilet, ever. Also buys you room for a shower across the bath, your current mod shower isnt desireable.
5. I cant help you with you choking the kitchen off from the living area or the huge amount of wasted space behind the couch, you lost the wife on that one, and no laundry or tiny laundry, again wife hates it. I would move the back mid bedroom behind the garage, label it as an optional study/bedroom and now you have an open concept that 99% of people want.

You can draw trusses in chief, it looks like you tried to make energy heel by raising the exterior wall height, you need to spec energy heel in your roof dialog. After you draw your exteriors and before you draw interior set your heights. You can vault certain rooms later, you dont need to vault the whole building right away then the gables show up like they do, your layers can get messy, unless your using Chief strictly for rendering which is a colossal waste, sketchup would be more "cost effective" for that. Which begs the questions, where do your prints come from?

My design/bim process is also in chief (with accurate build ready models, not just renders like you do) and includes full framing plans, cabinets/cubbies/built ins, full electrical/structured and full lighting plan allowing us to design mechanical layouts including all exterior penetrations ahead of time, correct or solve conflicts and verified in a preconstruction meeting with a full size set. I draw the prints, the extra time is worth less headaches during the build process and any contract specification issues, and I can draw anywhere, including on the boat or in the ice shack or on my sweet matress with the adjustable base. The goal is no questions from subs once we start, and the as built looks just like the renders, down to color. If Im not framing it I have done full labeled wall framing sectionals to remove as much extra framing members as possible, however its faster and less time intensive if the framers plate the building and Ill come and mark the layout versus having a ton of D size sheets to manage.

I see what you are trying to do, but if you moved to my area and tried that here the deck would be stacked against you big time, I see you as ahead of your time (compliment) but snarky (diss) and I dont know about you but Im in this business to make money, Id much rather be burning gas on my boat than on a construction site (I like both, but one better) any day of the week so its a means to an end.

Post some more of your plans, I like to criticize them.

Exactly the response I would expect from someone like Greentree & Dana1 that obviously does not do design-build nor sell high performance specs, nothing to show but a bunch of BS post and dart throwing anyone can easily do, that takes LITTLE talent. An attempt to make people look better than they are.

What happen to this statement you threw @ Dana 1 Greentree?

“All you got is the same fly sh*t on framing",

which is one of the least of the total cost in my & s/b in the better designs.

It appears your standards don’t apply to yourself,

Let’s look at the his BS in detail,

“go into plan view, right click on a wall and go to wall elevation detail. There you can add remove framing members and import framing plans into your layout file.”

Not at all how CA Premier or pro advanced CAD works…. TOTAL WASTE OF TIME calling the separate linked 2d layout model up to do simple 3D mods easily performed in 3D, which btw turns auto-framing off manual framing on. Any pro software that modifies 2D-to-3D is not pro, other way around, 3D mods 2D (WUS in (3D) IWUG in (2D) = advanced 3D Model Based Definition (MBD). Since as you should know the lot size, set-backs, best orientation, and easements can change this design, we don’t want to do manual frame yet. Most pro’s do that at the final drawing phase, many CA users just use it for drafting since that and interior rendering are its strengths, not 3D or BIMS. I do 3D CA models for client displays show and tell, will move to CATIA for the reasons stated above. I will be one of the residential industry’s first to do paperless BIMS managed 3D MBD I’ve been doing & helped pioneer for OEM manufactures for over two decades. Obviously way above your head you never figure out. Sounds like you can use some basic drafting lessons before moving to basic 3D modeling techniques.

“Double stud wall but 2x4 fire wall to garage, nice work smalls.”

There is no 2x4 framing at all in that model, more ignorance!

“This also updates the built in materials estimate for quantity allowing you to make OVE framing plans, but you knew all of this already Im sure.”

Take-offs are highly inaccurate CA X9 did correct in part but no where close to pro-level, since once again you have no idea what you are talking about despite the fact I clearly said we use Xactimate, or my estimator and I have linked softwares when we can afford him on a job.

And this one is the best of them all,

“however Im not going to model or do load calcs so take it as my opinion.”

We stress engineers don’t do “loads calc” they are developed by load cells, or by proven simulation models, been that way for centuries. In AEC conveniently located in CODE, dah! We do “Stress Analysis” huge difference! Any Stress Engineer PE knows that, I’m positive you have NO knowledge about loads, stresses, nor the differences more less how to calculate or develop, hence why you ignored my request to post your calcs on “ANY” house you did.

“Models and modeling simulations doesnt transalate to success when its built, you need good plans, which your obviously lacking with your ametuerish plans. Double stud wall but 2x4 fire wall to garage, nice work smalls.”

Once again your ignorance is vibrant here. We been proving simulations now for centuries in MANY industries. They are developed by instrument lab & field test articles and are the basis for all ICC CODE, dah!

You may want to call CADMAKERS, WUFI, THERM, the guys over there get a good laugh like I do & so enjoy out here.

Others check out what CADMAKERS has done by proven design-build simulations, Zehner is another now for about twenty years. This is AEC’s future, proven successful by others industries as well like Aero/Auto/Powersports. Everything will be done in 3D & BIMS. Inspection, instrumentation, and validation.

Virtual Construction: https://www.youtube.com/watch?v=VI6P-6dZ9pQ
Delmia: https://www.3ds.com/products-services/delmia/disciplines/

Of course one has to know how to collaborate with disciplines, stakeholders, and reduce the need for them in the design-build-inspection processed, I and others above have been doing successfully for over 20 years.

MEP : https://www.youtube.com/watch?v=VI6P-6dZ9pQ

Zehner: https://www.youtube.com/watch?v=p8q4Hfl-Wmo

They have all the necessary roles reducing the need for BIMS, unlike others like CA BIMS incompatable, or massive plug-ins like Sketch-up, etc….. that won't be in business in the long haul @ cost competitive pricing.
https://www.3ds.com/industries/architecture-engineering-construction/

Hitting commercial hard on its way to residential…..

Ok I’m done playing with BS, it’s been real, lol, biggest laugh being when greentree said we need dumber than dumb dumbs than his and dana’s post. Got real work to do. As you can see Greentree I'm light years ahead of you, won't be needing your advice anytime soon until the twelve day of never. BTW: X9 lost my some of materials properties, I did not ask your stupid advice just as the OPs did not, nor Danas, thats 99% inaccurate.

But seriously, you should post some more of your designs.

Well I just have to say WOW, I am sincerely sorry to the original poster of this thread. I had no idea that me posting what I had planned for my own (450sqft) house, would derail this thread so far. As somebody mentioned, neither of us provided context to which climate zones we were in. Idk about the Loghomebuilder, but I'm in zone 3 (near Ft. Worth, TX) and as for the comments on the costs associated with a lot of my plans, I suppose I should have mentioned that I am building the house by hand and the only labor I will be paying for is to install the standing seam roof. So any additional time or labor involved in my (apparently complicated) plan will be free. The main reasoning for wanting to do 2" of closed cell foam was the mostly for air sealing to create a very tightly built house. There may be other (cheaper/easier) ways of doing this and I probably just don't know of them. Again... Sorry for the derail.

Double post.