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insulation question
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Dana1
Senior Member
Posts:6991
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01 Apr 2011 06:14 PM |
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kermit- FWIW, you're overstating the whole-wall R values- it looks like you're delivering center-cavity or clear-wall, values, whereas I've been using whole-wall numbers, with all thermal bridging included in the framing factors. It's not apples to apples. A 16" o.c. 2x4 studded Mooney wall w 2x2 or 2x3 16" o.c. laterals may run about R19 as a clear-wall value, but doesn't thermally break the band joist or plates, subfloor, etc. It's maybe R16-17 for whole wall (which isn't bad- it's a huge improvement over the R10 you'd get with just the 2x4s and cellulose), but not more than that without going to 24" spacing on both studs & laterals, and it could be much less depending on the size/depth of the joists. By comparison a 2x6 24" o.c. studwall without sheathing foam is a bit over R14, without the complexity of a Mooney wall. With an inch of iso it's a real R20, and puts a vapor barrier on the right side of the stackup for FL. If a 1-1.5" rainscreen cavity between it an the siding is included it buys another average R2 or so of cooling season benefit for a total of R22-23, and a proportionally bigger reduction in the peak cooling loads due to the radiant-barrier effect of the exterior foil peaking when siding temps are hottest. 1" of EPS and a 2x4 16" o.c. cellulose basement treatment comes in at around R14 for whole-wall value. In a CMU wall in a place as humid as FL it's better to have something more vapor-retardent than 1" of EPS on exterior of the studs & cellulose too, especially if there's no exterior cladding with a rainscreen/masonry cavity to keep bulk water off the CMU. Chris- As I was driving home last night it occurred to me that part of the roof-decking prescriptive nailer spec may have more to do with the high uplift issues associated with overhangs and particularly with soffit venting, which is a different type of loading (and much more severe) than what wall sheathing typically sees. But tighter nailing of the sheathing does add something for face-on loads as well as racking. |
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diamonddave1967
New Member
Posts:25
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01 Apr 2011 07:09 PM |
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OK, to drive you guys crazy one more time! I have decided to go with SIP framing for the entire house: 6 1/2 wall panels with an "R" value of R-25
8 1/4 roof panels with an "R" value of R-33
Superior Walls in the basement
Geothermal for heat/air (I realize I should post this in the geothermal thread, but);
1. Main Floor: Qty 1, 3-ton Water Furnace Envision 2-stage heat pump system with variable airflow, M/N NDV038B rated 20.1 EER on hi cooling/ 30 EER on low cooling and 4.2 COP on Hi heat / 5.0 COP on low heat. The 3-ton unit would be mounted in the basement mechanical room. We would be supplying the air through floor vents. The mild day stage operates at 2.2 tons and the heavy day stage operates at 3.1 tons. The unit will come with a de-super heater to assist in heating the hot water tank. The basement will be zoned off of this unit. Basement venting through the ceiling.
2. Second Floor: Qty 1, 2-ton rated Water Furnace Envision split 2-stage heat pump system with variable airflow, M/N NDZ026A rated 18.6 EER on hi cooling/ 26.8 EER on low cooling and 4.2 COP on hi heat /4.7 COP on low heat. The mild day stage operates at 1.4 tons and the heavy day stage operates at 2.0 tons. The system heat exchanger will be located in the basement and the air handler located in the attic. Venting through the ceiling. The above come with the following: A. New programmable thermostat for each system and a digital thermostat for the basement zone. B. All supply trunk lines will be metal, sealed and insulated externally with flex duct run to the individual vents. The returns will be flex duct to minimize noise. Standard grills are being supplied. Duct work has Limited Life Time Warranty. C. Standard bathroom and dryer vents are provided. Bath fans will be by others. D. Venting of the kitchen hood. Hood by others. E. Return vents or cross-overs in each bedroom in addition to main returns. F. All power wiring and circuit breakers are provided by others. G. Horizontal closed loop for the Geothermal, Note: No rock removal is included. If rock is encountered that we cannot go around, work will stop and options presented to the owner. We normally do not have an issue. H. Performance Inspection Report after installation by our senior service technician approximately two weeks after the systems are up and running. I. Two Preventive maintenance calls [6 months apart] to be sure you will be ready for the next season during the first year of operation. J. Includes all geothermal piping. K. We will provide a manual J calculation as well as a drawing showing the vent location and the calculated airflow CFM for each vented room. L. Sleeves for the ground loop will be placed in the basement walls by others. The placement size will be agreed upon by the builder and Carolina Heating. M. 10 years parts and labor is included on the geothermal systems including the field. Other items are per manufacture warranty with 1 year labor included
Air Quality Options: 1. Air King air purifier for each system. The Air King technology has been proven to destroy up to 97% of all surface bacteria, viruses and germs. Installed investment is $580 ea, or $406 each after tax credit. 2. Qty 1, Trane Clean Effects 99.98% efficient whole floor air cleaner [great for pollen & air born dust reduction] I have this in my home and it is very effective. We recommend this for main and lower levels. The investment is $ 1500.00, or $1050 each after tax credit. 3. April Aire 1750 dehumidifier for the main level living area and and conditioned basement that will be connected into the duct work to help dehumidify during the in between seasons. Installed value is $1850 or $1295 after tax credit. Electrical feed and disconnect by others. 4. April Aire stand alone 1750 dehumidifier for the basement area with duct connection to each end of basement to control humidity. $1850 or $1295.00 after tax credit. Electrical feed and disconnect by others. 5. Qty One Energy Recovery Ventilator to bring in conditioned fresh air into the home for the main level. The Installed investment is $2650.00 or $1855.00 after tax credit. 6. Qty one Honeywell HM512 steam humidifier for the main floor living area. The humidification would be controlled by the programmable thermostat. Wiring by others. The installed investment would be $1650.00 or $1155 after tax credit.
Any comments/advice/suggestion? Mainly about the geothermal options.
Yes, I finally decided that SIP was what I wanted although my contractor is not comfortable with it. I am going above my budget but I thought it would be best in the long run. Thanks for all you have contributed & any more that you will! |
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cmkavala
Veteran Member
Posts:4324
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01 Apr 2011 07:55 PM |
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Posted By diamonddave1967 on 01 Apr 2011 07:09 PM OK, to drive you guys crazy one more time! I have decided to go with SIP framing for the entire house:
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Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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kermit
New Member
Posts:30
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02 Apr 2011 06:22 AM |
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no... those are not clear wall numbers , they're whole wall... i use all the framing.... all the mooney.... exterior surface, interior surface i've run it 6 ways from sunday... always comes up 18 +
but no matter.... don't trust the numbers ?... just thicken the mooney
i have to do something anyway i think current code is r-20 |
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diamonddave1967
New Member
Posts:25
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02 Apr 2011 06:38 PM |
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Now I have to ask; is doing SIP & geothermal overkill? By that I mean would the efficiency I get from geothermal be good enough to forgo SIP? Or if I do SIP would I do ok with regular air? While I am above my budget now I would like to know if if is even worth combining the two. Thoughts & comments are appreciated. |
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kermit
New Member
Posts:30
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02 Apr 2011 07:38 PM |
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i'd skip the sips & the geothermal...
bump the insulation values up with thicker walls and more cellulose
5400 sf in three levels ? 1800 sf per level ? 3-zones , minimum
do you have NG, or propane ? how are the electric rates ?
spend your efforts and money on insulation...... skip the geothermal
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Bruce
Basic Member
Posts:142
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02 Apr 2011 07:39 PM |
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The "Air Quality Options:" show a cost and then the cost after tax deduction. What tax deduction works on those "Air Quality Options:"? |
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diamonddave1967
New Member
Posts:25
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03 Apr 2011 02:21 AM |
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I have electric for utility. My goal is still low energy bills throught my years in the house (25+ years). Mainly what I want to ask is if I have SIP, could regular heat & air option be sufficient for my goal. Or if I had geothermal would geothermal in stick framing be? Or would the combination of the two make my house energy efficient to validate both costs? I know that is asking a question that only I can truly answer (cost). But would the combined two virtually garuntee me energy savings over 25 years to be worth it or would just one option be enough?
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kermit
New Member
Posts:30
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03 Apr 2011 06:44 AM |
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25 years goes by pretty fast.... at the end of that period you don't want to be replacing components..... like windows, roofing, siding, or geo thermal ( GSHP ) if you think those components are expensive today.... think what inflation will do to them in 25 years every decision should be made on life-cycle costing lifetime roofs, lifetime siding, 50year windows if you have a window selected... ask them to show you a 25 year old one by the same mfr. i don't think GSHP meets the test of life-cycle costing ask for a 25 year history on similar systems all-in-all... for you... i'd be doing conventional heat pump ... the new ones can easily take care of a SC winter guess what always meets the life-cycle costing ? super insulation |
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cmkavala
Veteran Member
Posts:4324
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03 Apr 2011 12:38 PM |
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Dave;
I might forgo the ERV in lieu of a 4" freshair (dampered) supply tied into the freshair supply side. this costs about $20. and is recognized by FSEC as an effective method. I will not use an ERV in my next SIP home, my current ERV is never used. |
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Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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diamonddave1967
New Member
Posts:25
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03 Apr 2011 12:51 PM |
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Thanks, Chris. Now I have something else I need help with. In fact, forget everything I asked about insulation & consider this (I think Dana sent me this): http://www.buildingscience.com/docu...assembliesSIP actually scores lower than a few other options. I know cost drags its overall score down, but it even scored lower on "Thermal Control" than spray foam, among others. This seems to be a very in-depth study done. What are your thoughts on this? Not trying to drag this on but since this is my dream home I need to be as thorough as I can. |
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cmkavala
Veteran Member
Posts:4324
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03 Apr 2011 01:37 PM |
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Dave; who knows? the grading was only 1 thru 5, if the SIPs were a 4.4 and the spray foam was a 4.6 it could be rounded up or down for a 1 point differential. Having built with SIPs for 17 years I feel that SIPs are the superior product, they are 3 times stonger than frame as well , that is propbably not important to you, but it is to some. Building Science Corp. is a great resource , but they too can have some eroneous findings. Not sure about the warning? |
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Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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kermit
New Member
Posts:30
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03 Apr 2011 07:25 PM |
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dana.... spent the afternoon at RI Builders Home Show with the Green Building Committee
rechecked my numbers for the Mooney Wall... here's my math.. would welcome any corrections: a friend and I developed a nice cross-hatch wall as an improvement of the wall I've been using for about 10 years... uses 2x6 and 2x2 cross and some strategic 3/4 EPS thermal breaks should come in about R-26 for total wall.. anyways ..... here's my calcs for our typical energy wall for the last 10 years:
MOONEY WALL r-value Insulation R-values
assume Mooney Wall 8' high x 12.5' long = 100sf
cellulose R value 3.7 /inch at 2.7 lb. settled density 2x4 KD studs R-4.38 for 92.5" studs @ 16" oc average of 12 ( 1 per foot ) 1.5 x 12 = 18" 92.5" / 12 = 7.71' 7.71' x 1.5' = 11.56 sf shoe & dbl top plate 4.5" x 12.5' .375' x 12.5' = 4.69sf so the framing totals ( 4.69 sf + 11.56 sf ) = 16.25 sf ( r- 4.38 )
the mooney cross -hatch is 1.75 X 1.5" thick @ 16" oc ( 8 pcs typical ) 8 pcs x 1.75 = 14" = 1.17 sf ( r 1.88) 5 " cellulose @ 3.7 = r- 18.5 r -value of outside surface components r-1.2 r-value of inside surface components r-1.13 2x2 = R-1.88 100 sf - ( 1.17 sf ) = 98.83 sf 2x4 = R-4.38 100 sf - (16.25 ) = 83.75 sf (2x6 = R-6.88 ) theoretical max is r- 18.5 x 100 sf = 1850
1.5" x 3.7 = 5.5 cells x 98.83sf = 544 3.5 x 3.7 = 12.95 cells x 83.75 = 1085 1.5 "wood r-1.88 x 1.17 = 2.2 3.5 wood r-4.38 x 16.25 = 71.2
totals 1702.4 actual 1702 / 1850 = .92 % stud portion of wall is 83.75 % @ R 12.95 & 16.25% @ R 4.38 mooney portion is 98.83 % @ R 18.5 & 1.17% @ R 1.88 r-18.5 x .92 % = 17.02 R-value (outside air 0.17 + FC siding 0.4 + «" sheathing 0.63 = R-1.2 ) ( 1/2" gypsum wall board 0.45 + inside air surface 0.68 = R- 1.13 ) so, ADD + R-1.2 outside air, siding & sheathing & R-1.13 for interior air & «" gyp. wall = 19.35 R-VALUE total wall
YMMV |
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jonr
Senior Member
Posts:5341
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03 Apr 2011 08:10 PM |
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Makes sense to me although I'd be tempted to use foam on the exterior - better for insulation and moisture reasons (things that absorb water next to wood has a mixed history). |
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Dana1
Senior Member
Posts:6991
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04 Apr 2011 12:06 PM |
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Kermit: Your estimates for the R-value of the siding & sheathing and the interior gypsum are too generous, as is your K value for framing timber (unless you're very selective about the species and density. Do you build only with KD Sitka spruce or something? :-) ). A more realistic K-value for any wood framing,siding, or sheathing would be between R0.8-1.1/inch. KD hemlock or fir runs a K value of ~0.9, which makes the 2D model of the edge-on 2x4s R3.15 rather than the R4.35+ you're using. Using an R value of anything more than R3.5 would be a stretch unless you're very specific about the species and density. Counting air films for ANY real R value is similarly a complete stretch on 1-2 story structures (and are still pretty small even in large commercial buildings.) A K-value of 3.7/inch for the cellulose may also be a bit optimistic in a real-world installation as opposed to a vendor's sample in a ASTM C 518 at it's perfect loft & density. 3.5/inch might be reasonable though. You also haven't addressed the lack of thermal break on the band & floor joists for this 2nd-story only timber-frame app. and you haven't adequately detailed the framing at the corners- no house is built with one flat wall (most have at least 4 :-) ) You're numbers seem optimisitic in nearly every case. The Oak Ridge National Lab numbers are derived from real assemblies tested in their large scale climate simulation chamber/tool. Whole wall R for a wood sheathed & sided 2x416" o.c. with cellulose fill is ~R10, with a clear-wall of ~ R12. Adding exterior foam is a near-perfect thermal break, and simply adds linearly. Add an inch of R4 EPS, you end up with ~ R14 whole wall. See: http://www.ornl.gov/sci/roofs+walls/AWT/InteractiveCalculators/NS/Calc.htm It's not a stretch to just assume adding the K-value x depth of any exterior foam would grow the whole-wall number fairly linearly. (Coming from an engineering background I tend to trust the numbers of folks who are in the business of actually measuring things than simple models, and more sophistcated 3-D thermal modeling far more than 2-D simple-arithmetic type modeling. YMMV.) Using ORNL data as a starting point for estimating the clear & whole-wall Rs of different studwall systems is probably going to get you closer to reality on those than any simple-arithmetic U-value x area analysis, since the test chamber doesn't CARE what the theoreical K-values of sub-components are- it MEASURES the whole-wall rather than calculating it. It's probably closer when analyzing Mooney wall assemblies for comparative purposes to start the the ORNL studwall numbers and estimate the additional R of the lateral extra depth using a 2-D model and less optimistic K values for the stringers (or spec out a low density species.) The interior & exterior claddings would be the same, the only difference would be the thermal breaking of the additional cellulose less thermal bridging. The most you'd get out of 2x2 Mooney stringers even using a full R3.7 for the additional cellulose in such an analysis is a whole-wall R of ~R15.25, (which is only R1 better than a 2x6 24" o.c. approach- no foam, according to Oak Ridge.) The type of foam used may be relevant to the climate though. An inch of EPS would underperform it's ASTM tested R by a whopping 20% or more when the siding is baking away at 120F (reducing a nominal R4 to something closer to R3 when you needed it most) whereas the additional cellulose in a Mooney assembly would perform pretty similarly to it's 75F test numbers. Iso would be a the better choice in cooling dominated climates. In the Mooney wall approach the plates band joists & subfloor are still not thermally broken and there remains a ~0.9% clear wall thermal bridging of the timber at the cross points. The U value of even that sub-1% adds up in a thicker assembly even using fantasy K-values for wood.
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Dana1
Senior Member
Posts:6991
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04 Apr 2011 01:58 PM |
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I forgot to ask: Where's the framing-factor allowance for doors & windows in the Mooney Wall analysis? (It's included in the ORNL whole wall numbers.) |
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kermit
New Member
Posts:30
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04 Apr 2011 02:57 PM |
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dana... thanks for the analysis.... as you know, the numbers vary depending on whose tables you use...
i've always used R-1 per inch of framing and i've always used R-1 for outside assembly/ air layer & R-1 for inside assembly
if you go on line you will find the more generous tables and values I quoted previously... i like real world numbers, but if other systems are being touted based on the more generous values, then it makes some systems less viable in comparison so.. i looked thru the assemblies they tested, but i found no true comparison to Mooney
trouble is I know that Mooney is superior to 2x6 @ 24" oc, both thermally, and construction -wise. over the years, we've done value -framing, 2x6 framing, double wall framing, interior foam sheets with furring , the Mooney has certainly been the most satisfying in those categories... window trim, kitchen cabinet install, straight walls, built-in blocking for ceiling molding and baseboard, thermal break.... and it facilitates dens-pack installation
it also lends itself to DIY for framing and insulating
we use insulated foam box. headers so my headers and window / door assemblies don't derate the wall, they enhance it the One stud / foot is a real world experience factor for a normal wall so... whole wall... R-18... R-19.. who knows? you have to define the wall using the standards generally accepted by the certifying / code enforcing authorities
do you think ORNL truely models a Mooney wall ? i was playing with their calculator and I couldn't enter items as they actually are in the field..... probably a lack of familiarity on my part
and the shoe/ plate thermal break is a new twist we brainstormed yesterday.... using a 3/4" EPS Performguard 5" strip at the shoe & the plate... the mooney there becomes a 1x3 furring strip, while remaining 2x2 in the field.
if i change one element.. the 2x4 to 2x6..... we think this wall will be a true R-24 i made up my mind about 10 years ago that the only foam we'll use in or houses is Performguard ie: if the foam mfr. won't treat his product and protect it against insect and reodent infestation, then it isn't going in our homes
so far the only mfr. i've found are the ones franchised under "R-Control" and "PerformGuard" so , that means my self-limiting choices are Cellulose and EPS
many times we did exterior foam sheathing in the past... but the complications were enormous in trying to conform to racking and shear wall code requirements.. a lot of the "T-straps" and let in brace systems were not really in compliance so that meant putting the plywood sheathing back on the studs and adding the foam to the exterior of the plywood then blocking for windows & trim going back to the scene of the crime after 3 - 10 years ( or a lot of the homes built in the '80's ) we have always found the foam fully infested with ants, termites, mice, and various bugs I don't even know the name of.
The new codes , current , and right over the horizon, will probably have us at some place around R-24... R-25
Eventually I hope to build a Passiv-house.. or an net-zero... i'll be looking for an R-40 wall, and will probably go double wall ( 12" ) with cells only.
Have you seen Robert Riversong's modified Larson Truss wall ?
I was talking to an Energy Star Certifier yesterday.. he informed me that my furred ceiling was unacceptable because of the theoretical 3/4 void it creates if you put up insul-mesh supported by furring.. then blow.. then put up the gypsum board
says the usual fix is to install a 3/4 filler between the furring... what do you know about that ?
next question.... so i get a feel for where you're comming from ..... what is your favorite production/energy wall ? at the home show yesterday... we saw mostly foam installers
most had little blower demonstration machines designed to make foam look great and cellulose look dumb. I wonder if the industry isn't being driven by foam mfr's and fiberglass producers. Hard to compete with Dow & Owen's-Corning |
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Dana1
Senior Member
Posts:6991
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08 Apr 2011 12:13 PM |
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The ORNL calculator only uses standard construction & OVE framing options, with a consistent framing factor for door & window framing (which you seem to omit, making yours a clear-wall, not whole-wall analysis.) But a Mooney Wall is simply a standard-construction with enhancements. If you run your 2-D model analysis on only the enhancements and add it to the no-foam option on the ORNL numbers you'll be closer to real-world performance. I haven't seen any of Riversong's buildings close up, but I've looked carefully at both his and other Larsen Truss designs. Since he seems to skip exterior sheathing in favor of ship-lap siding, I'd be a concerned about long term issues from a moisture control point of view. It's a flow-through hygric buffering design, but IMHO it would work better with a sheathing layer to contain the cellulose, but using lighter siding with a rainscreen gap. BSC has also done extensive thermo-hygric modeling of a number of high-R and moderate-R wall systems, including Larsen Trusses and a 24" o.c. 2x6 + 2x3 Mooney Wall (see Case 3) : http://www.buildingscience.com/documents/reports/rr-0903-building-america-special-research-project-high-r-walls Take a peek at Table 3: The whole wall value (of a wall fully an inch thicker than your analyis) comes in at R21.5. But note the comparative values at the rim joists and top plates compared to just adding the inch of XPS to 24" o.c. 2x6 framing. (Case 2a) for an R20.2 whole and the relative complexity it take to achieve what is essentially the same whole-wall R value. Adding the ~ R3 of EPS as a thermal break in critical places is good! I'm not convinced that PerformGuard is the only solution to the bug problems, although I agree it's a good product. I've yet to see anything tunneling through foil-faced iso (or fiber-faced, for that matter), and I've only seen rodent damage to XPS, not ants. EPS seems to have the larger issue with ants & termites. Using copper flashing and copper-clad capillary breaks on foundation sills seems effective at keeping termites from finding their way to the foam/wood. I'm not sure what's to know about the 3/4" furring gap with insulmesh in a ceiling. Was their issue the potential for a thin cavity being a thermal bypass? As for personal favorite systems, it depends on the intended whole wall R value and the comfort level/ flexibility of the builder. Up to an ~R25-R30 whole wall R it's pretty easy & flexible to go with 24" o.c. 2x6 studwalls and exterior foam, and builders are pretty comfortable with it. If the shell design is fairly straightforward there's a lot to be said for SIPs. For R20 insulated basements ICFs are a slam-dunk, but for above grade walls the additional cost at high-R needs to be rationalized on more than thermal performance. For R40+ superinsulation, Larsen Truss has a performance advantage over, and fewer moisture-risk details to deal with than double studwalls (but I've done neither), but at a cost in framing complexity. I'd like to see more analysis of the engineered I-stud thermally broken with exterior foam approach they took with the Urbana PassiveHouse too, since that seems much simpler to build than a Larsen Truss. I suspect it would be a quicker/easier/cheaper way to go in a production-build than either double studwalls or Larsen Trusses. I like the ease of air sealing with spray foam, but it's a ridiculously expensive way to go high-R. It's very useful for adjusting the vapor at a proper layer of the assembly too. For cavity fill on studwalls I'man unabashed cellulose fan in terms of peformance/$. The K-value of the cavity fill hardly matters once it's over R3/inch due to the thermal bridging factors, but the resistance to convection within the fiber counts. To get similar air-retardency with fiberglass you have to go with 1.8lb density Spider or Optima, for quite a bit more money, with only a modest boost to whole-wall R value. The hygric buffering of cellulose is also protective in most situations, but can be a double-edged sword in chronic bulk leaking or flooding situations. |
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BabyBldr
Basic Member
Posts:123
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12 Apr 2011 10:28 AM |
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I understand from the discussion above and other sources that interior cross strapping (Mooney) does not rate as a high performance wall. I understand that it is not anywhere in the same performance ballpark as SIP, ICF or framing + exterior foam. But I still have a follow-up question on this method. I’m trying to understand this as a homeowner (I’m not a builder) who is planning to use a Mooney wall on the new home we’re building because it fits into the overall project constraints (budget, availability of skilled labor, DIY friendly).
I was wondering it if would be possible/advisable to change the typical strapping material from wood to rigid foam cut into long strips. It’s better for thermal bridging, right? But would it be OK for attaching drywall? Or would one need to hang drywall by screwing through the foam strip into the 2x6 underneath? Other issues?
In discussion above, Kermit said: (04 Apr 2011 02:57 PM) and the shoe/ plate thermal break is a new twist we brainstormed yesterday.... using a 3/4" EPS Performguard 5" strip at the shoe & the plate... the mooney there becomes a 1x3 furring strip, while remaining 2x2 in the field.
Is Kermit referring to the idea of 'rigid foam interior strapping'? Or is Kermit talking about using the EPS somewhere else (exterior?) and still keeping the interior strapping as wood.
Thanks for helping me understand this.
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kermit
New Member
Posts:30
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12 Apr 2011 12:09 PM |
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baby bldr:
a cross strapped wall can be designed for any r-value you want. My take on Dana's review is that the weak point was the shoe & plate detail, and this can be helped by the 3/4 foam break with 1x3 strapping, he also says that I didn't derate the wall to take in account for windows, doors, double studs for shear walls, etc. but i contend that I do... but i'll concede the point... typical wall is NOT actual wall, long walls with no openings and a higher ht. ( like 9' walls ) rate better,
window walls with almost solid windows rate a lot worse
the regular field mooney is not a weak point.. the thermal bridge amounts to a 2 square inch patch every 16 " in energy construction, the mooney wall lends itself to good production because you frame normal... 2x4 @ 16oc or 2x6 @ 16" oc.. the Mooney is simple to rip and simple to install ( you can get 4 pcs of 1.5" x 1.75" from a culled 2x8 ) if you combine these with good energy corner framing,and insulated window & door headers, you get excellent walls
Dana contends ( i think anyways ) that our typical 2x4 mooney is about R-18... and a typical 2x6 Mooney is about R-23 give or take an R... those are great walls..
if you want to go to a better wall, once past the 2x6 Mooney, i would go to a double wall and jump to a 12" wall for about an R-40.
so .. my choices are 2x4 Mooney R-18 ( 5" frame , 6" with sheathing & drywall , add for rain screen if you want ) ... or..... 2x6 Mooney R-23 (7" frame, 8" with sheathing & drywall )........ or......
12" double wall R-40 ( 12" frame, 13" with sheating & drywall )... 2x4 exterior frame @ 16" oc, 2x3 interior frame @ 16" oc
my contention is that comparable walls in sips or spray foam are not as cost effective comparing like r-values vs. like r-values.
Dana can elaborate on the above .. one thing he said was that bulk water leaks would destroy a cellulose wall... but of course any bulk or continuous leak will destroy any wall.. and fiberglass doesn't fare any better.. some foams will not absorb moisture, some will.... none will act like the same sponge cellulose or fiberglass will.. but in the end, the leak is not supposed to happen. good flashing details , good roofing details, protecting plumbing runs.. those are all part of the every day world of good construction
I am not here to denigrate sips or foam... just here to say that energy framing is a viable route to go also... and i can do it all with our in-house labor.. and i don't have to worry about vermin and termites and carpenter ants
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