When ICF and SIP won't work
Last Post 08 Sep 2008 03:29 PM by Boontucky-girl. 24 Replies.
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Boontucky-girlUser is Offline
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25 Aug 2008 12:17 PM

We had decided to build our house using ICF. When we got the few local quotes to come in we reaziled that we could not afford to go ICF all of the way, so we said let's do ICF basement and SIP main floor. Now that we finally have all of our quotes together for everything to get the house dry-in, it seems that this isn't an option either.

We are not financing with a bank, so we have a budget to get the house to the dry-in stage before winter. Right now it looks like a regular built basement with a regular stick build home is the only way we can make this work. And that's even including a quote for doing the sprayform insulation, and insulating the basement. I keep seeing that ICF or SIP should be about 4% higher than regular build, but that must be if you are comparing turn-key ICF/SIP to turn-key regular build price.
Our problem is that we will only hire out the trades to the dry-in, and we only have so much money to get that done. After that, we will work on the inside as we go, since our new house is on the same 10 acres as our current house. So comparing dry-in cost to go the ICF/SIP route is almost 40% more than regular, and we don't have the extra 40% to cover the expense unless we left the windows and roof off!. Things like needing lesser HVAC requirements for ICF to offset costs don't apply to me because it will probably be another year before we get the HVAC installed. And my husband is not convinced that lower utility bills will be enough to recover the investment. And if it was just a little bit higher, we could wait until next year and try to save up the extra that we're missing. But unless we won the lottery, it would be 5 years before we came up with the extra capital to cover ICF/SIP, and I simply can not wait that long to get out of our old house.

So, is there a way to go the stickbuilt route and still achieve a decent level of energy efficiency? I am very discouraged and I am upset because stickbuilding just doesn't make sense to me anymore, and it is a big house, almost 3000 sq ft once the basement is finished, and with Iowa winters, that's a lot of space to heat up, and I don't want to pay a fortune to be comfortable.

So any help will be appreciated. Thanks,

Boontucky

MDiverUser is Offline
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25 Aug 2008 11:28 PM
Have you considered building a smaller house? Trade square footage for efficiency? If building a smaller house is not an option, I still wouldn't be discourage, just plan on building the best possible house you can, pay particular attention to your windows and doors, insulation (please don't settle for batt), and do everything in your power to seal the house up tight. Is exterior insulation an option (the product isn't too expensive, and it sounds like you are doing alot of the construction yourself)? Also, spend money on good (efficient) mechanical systems. I don't think every house has to built with ICF or SIPs to be green or efficient, you just have to pay closer attention if you are using conventional building techniques.

Good luck
GreenGoddessUser is Offline
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25 Aug 2008 11:43 PM
If you go stick frame make sure that you do the advanced framing technique.. it uses less wood.. its 2x6 on 24" studs.. uses less wood and allows for better insulation..if you don't know what that is go to Francisco Ruiz's book on Affordable Building or David Johnson on Build Green from the Ground Up both offers options and details on this building technique... and i agree with the idea that less is more... I try very hard on discouraging people from going beyond the space they truly need and utilizing it more effectively and efficiently...
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26 Aug 2008 05:48 PM
Boontucky,

My BSME is 35 years old, I've never done design work, and I've never built a house, but I've been reading up on what I want to do in several years when I retire -- on how I can make my next home comfortable and affordable.  My non-expert take:

By far the most helpful information that I found on conventional construction was at the Building Sciences Corp site; and there is a lot of free information there.  I recommend that you purchase Joseph Lstiburek's "builder's guide" appropriate to your climate (he's a primary at BSC); the book will be modestly expensive, but the SIPs version that I purchased is *very* good.  He argues that you must treat the building as a system and invest where your next dollar will have the most effect.  Infiltration will drive heating and cooling bills, so he pays a great deal of attention to sealing the structure.  Water damages the building long term, so he works on systems to shed water.  HVAC moves air, and if its leaks are outside the conditioned space, it creates hosts of problems, so he works on where the HVAC is installed (inside the conditioned envelope) and how it runs (with adequate returns and air exchanges).  A well thought out, understandable approach to the details that will make a house work *as intended*. 

I'd also recommend that you read up on optimum/efficient framing techniques.  If you look at many (most) homes today, every problem was solved by adding a stud.  You ended up with lots of thermal bridging, lots of small bays (as in inches wide) that are impossible to seal or stuff, and you pay extra for all the materials and labor that degrade the building's performance.  By arranging the studding in proper, systematic patterns, you minimize materials and minimize these problems by creating bays that are easier to seal and insulate. 

Will all this be as tight or as efficient as a SIPs house?  I would expect not, but I would expect it to be *markedly* better than traditional construction.  Where along that continum from yesterday's poor procedures to a "modern" SIP or ICF structure I don't know -- others on this site might be able to answer that.  My guess is that it would approach SIP's thermal performance (it would not have the structural advantages that SIPs or ICFs might offer in areas with environmental issues such as Florida is experiencing this week).

How large is your family?  How much room do you actually NEED (rather than want)?  If I needed to build now for my current needs, I'd cut as much as I could from the structure -- as noted above, you don't pay for what you don't build.  But I'd also have the design provide for expansions:  Where will the stairs go if we added a second floor?  What hard points will I need access to in order to add on?  Where should I stub out utilities so that they're ready to connect?  Where would a new wing go?  If I do add on, how will I gain access to the structure that's in the initial build?  (Design raceways into the shell for all utilities and HVAC so that you have access to add or alter what's there -- don't let the first sub-contractor on site dictate everyone's routing.)  Etc.  If all that's planned in advance, you can reduce the cost and time to add on in 5 years when you've saved more. 

I wish you luck.

Very respectfully,
Larry


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26 Aug 2008 07:19 PM

Larry,

You missed your calling.  You have a good understanding of planning, design, and technology.  I would have saved a lot of time educating my clients if they had done their homework like you.

Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
Mark FlemingUser is Offline
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27 Aug 2008 02:41 PM
Readytoretire said " How much room do you actually NEED (rather than want)?"

To this end, I would recommend a book called "A Pattern Language".  It deals with questions of what is comfortable as opposed to what is impressive or what do others have? 

Mark

If you don't have a great place to sit and read, the house design is a failure.
Boontucky-girlUser is Offline
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28 Aug 2008 09:45 AM
Thank you for all of the help. I have begun to read the buildingscience website and it's fascinating. I also got a copy of the builder's guide to cold climates from my library and read it cover to cover. Very good insight indeed.

I am very interested in the advanced framing technique but when I asked local trades about it, they had no idea what I was talking about, and one made the comment that the only time he ever heard of 24" framing was with some "very cheap" garages. His impression is that less wood is not as strong, etc. etc.
I'm going to call one more framer that might be interested in this approach. THe fact that I can have more insulation area compared to 16" oc really appeals to me. But I'm concerned that if the framing crew isn't familiar with this approach they'll charge more, even though it should be less work for them (more work for me upfront to plan it all)

And believe it or not, we did shrink the house down! But there are a few things that I will not budge on, like I must have 12'x12' bedrooms. I currently have 10'x10' and there's only room for the double bed and not much more, and I want 48" stairway. My current one is 36" and we can barely get the furniture up the stairs. Also, I want 11" thread and 7" risers (without counting the bullnose on the threads) so those steps take a lot of room. And we are building only two bedrooms on the main floor. We're taking advantage of a walkout basement that we'll be finishing and placing three bedrooms down there. (When my parents visit they can stay as long as a month or two since they live in latin america and can't come to visit as easily as if they lived within the states).

I wanted a large kitchen because when we have family gatherings, there's 14 of us just on my husband's side and the family is still growing. And as you know, the kitchen is where you gather. I also must have a mudroom. We live out in the country and I am tired of all the mud/snow that gets tracked into my kitcken right now. Our house plan took us two years to design, and we thought about traffic patterns, views, orientation, etc. I planed all of my doorways to be large enough for accessibility if we ever need it. The laundry is in the main floor for the same reason. The basement will house children bedrooms and guest bedroom, plus a family room. We do have a kitchenette and dining room down there that will become the bar/lounge area. We will be building only the shell this year, and we'll work through the winter to finish the basement so we can move in. We will finish the upstairs as we go (so we'll be in construction for the next ten years). And I do have a place to sit and read, right in front of my large window and the fireplace that overlooks our wooded area. Now that we have our dream home, we want to build it energy efficient and gain as much sweat equity as we can.

I really like this forum because I can get such expert knowledge. Just because I read a lot about all of these techniques, doesn't mean I necessarily understand all of it, and this forum has made it possible for me to ask lots of questions and gain more understanding. Thank you for all your insight.

Boontucky
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28 Aug 2008 11:38 AM
Boontucky,

Regarding framing:

The nice thing about the optimized framing is that the technology is not new -- it uses the same old 2X material that the framers are used to working.  It's cut and assembled in the same manner.  What differs is how that material is spaced.  Even a traditional stick-framed house is laid out structurally.  Upper level walls are placed over lower level walls; joists in the deck are spaced to account for and join with lower level walls and the walls to be placed on the new level; etc.  So, . . . "all" the framer needs to do is to change the spacing and pattern to which he assembles the walls.

Will it be less strong?  Of course it will; four studs will support more weight than will two studs:  I would expect a door opening framed with a pair of king studs to define the opening, a pair of cripple studs to support a header, and a header to support a lot more weight than just the bounding studs and a horizontal 2x4 to form the upper boundry.  But, if the door opening is in a non-weight bearing wall, what does that extra capacity gain you?  If it's a structural wall but the studs are not needed to support the load, what does it gain you?  As a boy, decades ago, I was told of a local excentric who had a house built out of solid 2X lumber -- each plank was laid horizontally on top of the previous and nailed down.  He created solid wood walls with the wood laid horizontally.  That conceptually simple structure would carry a great deal of load, but it would be a maintenance nightmare because window and door frames would rip apart as the width and thickness of the wall planks (and thus the height of the walls) changed with seasonal humidity while the length of the trim pieces did not (a board's length does not change significantly with humidity).  Any framer would agree that traditional framing would avoid those problems.  An the framers will agree that many of the studs in the traditional wall are not *structurally* necessary, and those unnecessary studs create their own problems.  You're asking the framers to make two adjustments:  First, you want them to eliminate the structurally unnecessary studs.  Second, you want them to align the remaining studs so that the upper level stud is directly over the stud below it and -- thereby -- prevent flexing the floor and the sole, and top plates.

If each stud is now necessary to support the house, I would not use cracked or shattered studs, studs that are all pith,  studs filled with cross knots, etc.  So I would recommend that you then need to make an additional adjustment:   You'll need to provide quality framing material; and you'll need to ensure that it's stored and protected on site.   (The framers will like working with the better material.)   The higher quality framing material will help you in your interior finishing because they won't warp as much -- your dry wall will hang better and your walls will be flatter.  But, if I were building with 2X4 studs, I'd sure not want my electrical or plumbing contractors chopping up those structurally necessary studs, so I'd ensure that plumbing didn't go in outside walls and that electrical was run in races/chases rather than through the studs.  (This is similar to the same issue in SIPs:  don't cut structural members.)

Regarding the design:

Believe me, I understand your desires.  My wife and I have a 2:1 difference on what we want.  I'd like 1,000 sf, maybe as much as 1,500; she'd like 4,000, can easily cut it to 3,000, and -- under pressure -- is willing to discuss 2,000.  But go back to your original posting and your last reply:  Can you live in the house for five years if you build and finish the basement and first floor only?  Use full joists and rafters for the attic; build in the stairs but they'd now serve the attic rather than the 2nd floor; bring all your utilities up to the 2nd floor deck and stud them off below the deck.  You'd be ready to extend up to get your dream house with very little waste cost in delaying the 2nd floor.  In five years, when you've saved enough, you can expand.  If you move before then, or if anything else happens, would you rather be where you are now or in the lower section that you could build now?

Good luck,
Larry


Boontucky-girlUser is Offline
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29 Aug 2008 02:10 PM
Thanks Larry. That's exactly what I think about the framing technique. The framer we have now is a finish framer as well, so he is picky about his walls being straight and is notorious for sending truckloads of wood back to the supplier if it isn't up to par. The supplier we are using is supposed to have very good quality lumber. I really don't see why switching to 24" would be so much more different, but everyone I've talked to balks at the idea and are concerned about the flimsy construction.
If we go this route, I'll be using 1 1/8 subfloor, and 5/8 drywall to beef it up a little bit.
The good news is that we were able to get ICF for the basement. I know it would have made more sense to have ICF above grade, but we have almost 1/2 of the basement exposed, so we believe ICF below grade will not be a bad investment.

For the main floor, I want to use Rboard on the exterior and the supplier said to cover that up with housewrap. I thought rboard was exterior grade, but does that make sense? We are thinking of keeping the OSB and adding the insulation on the exterior, so to me if housewrap is to be used, it should be on the OSB. Would housewrap on top of the OSB and then on top of the rboard be overkill?

You get to a point where you get too much information that it's start to conflict because you can't keep it straight.

THanks
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30 Aug 2008 12:55 PM
Im in the process myself of building a new home. And i used 2x6 on 24 inch centers. On the exterior i used atlas energy shield only which is r 6 You do not need to use typar wrap if you are foaming the walls inside which is what im doing 2 inch closed cell foam followed by a r 13 batt. which gives me r 32  I used 3/4 inch osb glued and screwed to enginered floor joists which will be covered in thermal crete for in floor heating My framer feels you end up with a straighter wall with 24 inch vs 16 inch centers his reason is less crowns because of less studs but we will still use 5/8 drywall for exteior walls As far as structural we added metal wind bracing on 45s to the walls  but with the walls filled with foam it is a much more rigid wall then any 2/4 on 16 inch centers I had planned on going icf and priced the whole project for icf but the cost was 40,000 more compared to the way we did go Is icf the best ? I think it is but i dont feel ill ever recoup enough energy savings to pay the extra 40,000. Im in ontario canada where we have cold winters so energy use is a big concern . But i still dont see icf  being able to pay for itself
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30 Aug 2008 08:02 PM
Posted By jimmy48 on 08/30/2008 12:55 PM
Im in the process myself of building a new home. And i used 2x6 on 24 inch centers. On the exterior i used atlas energy shield only which is r 6 You do not need to use typar wrap if you are foaming the walls inside which is what im doing 2 inch closed cell foam followed by a r 13 batt. which gives me r 32  I used 3/4 inch osb glued and screwed to enginered floor joists which will be covered in thermal crete for in floor heating My framer feels you end up with a straighter wall with 24 inch vs 16 inch centers his reason is less crowns because of less studs but we will still use 5/8 drywall for exteior walls
Good for you! How much was the foam?
Is icf the best ? I think it is but i dont feel ill ever recoup enough energy savings to pay the extra 40,000. Im in ontario canada where we have cold winters so energy use is a big concern . But i still dont see icf  being able to pay for itself

In your climate, R-Value rules. It sounds like you are doing ok, and have made some decent choices.
....jc
If you're not building with OSB SIPS(or ICF's), why are you building?
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31 Aug 2008 08:20 AM
I would not use this type of wall system. You have placed a double vapor on the outside of your wall system with a insulation that allows high amounts of vapor migration. The only way to mitigate a possible problem, is an internal vapor barrier under the sheetrock.
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31 Aug 2008 04:52 PM
The foam cost me $ 2 pr sq/ft that seems about the best price i could find in my area . As far as the double vapour barriar i am putting 6 mil poly inside the house under the sheet rock which is code in my area. This should prevent any air or moisture from entry  to the wall from either side as the closed cell foam acts as as vapour for the exterior
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02 Sep 2008 11:57 AM
Jimmy, Thanks for replying. I sent an e-mail to my framer about the advanced framing technique but he hasn't replied. And my plan was to build the wall this way interior to exterior: 2" closed cell foam - studs - 1/2" OSB - housewrap - Rboard 1" insulation sheathing - furring strips - cement board siding. Or, sub the 2" closed cell with 5" open cell, it all depends on the cost.
I actually wanted to put 2" r board, but supplier is concerned that you would need 5" nails to get the siding on. I was thinking that I can screw the furring strips, then the siding goes on the furring strips so it's a moot point, but he's got the hubby convinced that only 1" so that siding can be installed. So I'm looking for info to see if 2" exterior insulating sheathing is possible.
Our supplier only stocks 1", so I thought of putting 2 layers of 1" with joints staggered, but again, I need to find that this is possible with fibercement siding. Should I be looking at other options besides R-board. That's the only thing our supplier stocks, so I would have to see where to get other types.

Now when talking with my supplier, he said to put the house wrap on the outside of the Rboard for protection, which left me scratching my head. And I know that if I use insulation sheathing, I don't need the OSB, but the OSB does provide for somewhat impact resistance, and I do live in tornado country, so for some small peace of mind, I feel better with the OSB there. That's why I was wondering about the housewrap deal. So should I just use the housewrap on the outside of the OSB? I know the housewrap sort of acts as a drainage plane, and I would be concerned about not having anything protecting the OSB should any water get behind the insulation.
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02 Sep 2008 01:04 PM
Normally, OSB is attached directly to the studs and is used for wind bracing.

In the 1970's I used 2" of DOW Chemical Blueboard under cedar siding without the OSB.  This house is still intact and the cedar siding still looks good.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
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02 Sep 2008 02:21 PM
Thanks Alton. And I guess we finally decided that only 1" insulation since that's the max that hardie plank siding allows.
Yes, the OSB would be attached directly to the studs. I think that I only need sheathing on the corners if I go with insulation as the sheathing. I did read a report somewhere about sheathing insulation with OSB and inside spray foam that will give more protection for impact resistance of flying missiles during a storm. So, we are planning on keeping the OSB, what I am trying to figure out is where does the housewrap go? Between OSB and insulation sheathing? On top of the insulation sheathing?

Did you use furring strips for your siding? I like the idea of furring strips since it gives an air gap for moisture control, my husband doesn't think we need it.

Thanks.

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02 Sep 2008 03:19 PM
I did not use furring strips back then.  But if I built like this again I would use 3/4" furring strips.  I would have the following starting from the outside in:

Hardie Siding,
3/4" furring strip,
either house wrap, felt, or tape the seams on extruded polystyrene,
2" extruded polystyrene such as DOW Chemical Blueboard,
7/16" OSB,
2x4 studs on 24" centers aligned with roof trusses,
2" closed cell spray polyurethane,
paperless sheetrock.

If the budget was too tight to use spray foam, then I would use cellulose between the studs.  I think cellulose works better as an insulation than fiberglass.

Installing furring strips allows the board insulation to be thick as desired.  The void behind the Hardie Siding promotes positive drainage and allows the siding to dry.

Alton C. Keown
Residential Designer and Construction Technology Consultant

PS:  Each year I donate a lot of my time to interesting projects (unusual) in the South East.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
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02 Sep 2008 04:03 PM
I assume you'd use PT furring strips in termite country? Or would the vents at the bottom keep them out? I'm following all this with interest, as I may not be able to afford SIP's or ICF. I'm paranoid about termites, having had them here in FL.
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02 Sep 2008 04:58 PM
Yes, I would use pressure treated furring strips or the new synthetic strips I saw at a trade show.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
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04 Sep 2008 01:11 PM
Thanks Alton. So you are saying that if I tape the seams, I don't need housewrap? If not, then housewrap on top of the foam. Just double checking.

Any special details for the windows? Do they attached to the OSB or the insulation sheathing? How do you trim? Our windows have a 1" depth from the nailing flange to the exterior edge. How do you trim around them?
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