New home builder looking for some advice
Last Post 07 Nov 2017 09:20 AM by Dilettante. 67 Replies.
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whirnotUser is Offline
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25 Oct 2016 10:28 PM
A couple of comments. Your new friend may not like minisplits but there are millions, including me that do. I am just finishing a new home with two Hyperheats and would not do anything else.

A 900 square foot shop I built last year In Central Oregon, had a maximum heat bill of $23 last winter. Framing,; You noted that 2x6 is not that much more expensive than 2x4. If you use Advanced framing/OVE, you will eliminate 20 percent of the studs, and cost of studs, make a stronger structure and add more insulation. Also, you mentioned looking for Budget friendly windows. You appear to want to build a well insulated high performance building with approx. R35 walls. If you then put in "budget friendly" Energy star windows, they amount to about R3.5 Makes no sense to me. Spend extra money on windows and get good ones. With Alpen windows and a quality Shade we will attain R13.5.

We also considered Solar PV (thank goodness there is not enough wind here to consider a turbine.) With a high performance home and electric rates of .06 they just wont pencil out. unless you have some huge load not discussed the savings over Grid electricity just isn't there. We have similar, slightly higher rate and it doesn't work.
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25 Oct 2016 10:44 PM
I didn't say I agreed with him on any of it. Just repeated his opinions.

Advance framing is not going to work for me. As I said in the first post I need to stick to normal building practices. Plus I'm doing the building myself. If I need to relearn framing, it's going to extend the build time.

As far as the windows go, everything has a budget. I'm trying to find the best balance. In not talking about running to the big box store and get something of the shelf but I also can't spend $800 each for windows.
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26 Oct 2016 04:42 PM
Posted By Bob I on 24 Oct 2016 06:54 PM
OK, so the real question, when you finish fact checking analysis (I admit I was shooting from the hip): does the "inflation-adjusted" long term price of fossil fuels in economic terms as well as ecological terms makes solar panels illogical?


Of course the EIA data only includes the inflation adjusted retail price of the fuels, not the externalities.

But site-solar is going to be cheaper than ANY of it on a lifecycle basis (soon!), which is why for new construction where the the loads & roof real estate for solar can be controlled BY DESIGN, setting it up for heat pumps & rooftop PV (to be installed now, or in a few years time) makes perfect sense. If you don't pay attention to it now it makes it more difficult, more expensive or even impossible later.

I just object to all of the assumptions that get thrown around about the future price of energy. It's a competitive market, and in the future energy writ-large is always going to be bounded by the lifecycle cost of the energy technologies, not the extracted fossil fuel commodities, which have traditionally been volatile, and hard to predict even in the shorter term let alone the long term.

The oft heard energy price inflation that probably galls me the most is the, "electricity price are rising 4% per year, year on year" (I've also heard 6% quite often.) Usually in a sales-pitch by a solar leasing company with $0 down very discounted initial pricing, but with a or 2.5% or 3% annual price escalator clause. This level of mis-statement of fact gets into the realm of fraud. Electricity pricing has some volatility, but it is generally decreasing over time in real terms, and in the current environment has significant downward price pressures being applied by the rising tide of zero-marginal cost power from PV & wind, which are also competitive on a lifecycle cost basis with highest-efficiency natural gas (and cheaper than keeping legacy coal going.)

The zero marginal cost cuts into both peak and average wholesale electricity pricing, and the levelized cost being lower than incumbent generators means the rising tide of renewables on the grid will be rising faster, since it's now the go-to first choice for capacity replacement as legacy thermal plants retire. In Texas the ERCOT grid operator anticipates that nearly ALL of the coal plant retirements between now and 2030 will be replaced by utility-scale solar, at a net savings to the ratepayers. The trends are similar everywhere.

Electricity in the future will be cheaper than it is today, not more expensive, and telling people that it will be increasing at ANY year-on-year percentage over the long term is coming pretty close to an outright lie (at least for those in the solar or power biz, who know damned well it just isn't true.)

Commodity fossil fuels see downward pressure from electricity price deflation too, and even though commodity energy pricing is more volatile than electricity pricing, it can't continue going up in price on average and still compete against electric technology alternatives. Even gasoline & diesel are primed to lose market share to electric vehicles, even at today's lower-than-peak pricing. Some large potential growth markets such as India have set firm dates after which internal combustion engine light trucks & cars won't be legal to sell any more. (In India that date is 2030.) Oil pricing will continue to be volatile, but high oil pricing is unsustainable- the lifecycle cost of owning an electric vehicle in the US today is less than it's fossil-burner alternative, even without subsidies. The up-front cost is a hurdle that must be cleared, but that's do-able with creative financing (which is what policy makers in India are hard at work crafting for their market right now.)

In short, try to avoid using the energy price inflation bogey/straw- man in any discussions about building efficiency
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26 Oct 2016 04:49 PM
My gears are still grinding :-)

I had a thought today. I still am trying to understand all this building science and walls drying ect.



I have two brand new rolls of house wrap given to me by a friend. since my plans don't seem to require this for the walls, Could this be used to "seal" the ceiling? I'm thinking I could run it between the double top cords and tape it to the exterior rigid insulation and then under the drywall for the whole interior ceiling for an inside to outside seal across the whole building. I'm thinking this will allow the wall to dry to the interior and still hold the heat from escaping the ceiling.

Or am I still not getting it?
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26 Oct 2016 05:15 PM
Every wall assembly needs a defined drain plane and weather resistant barrier, which could be housewrap, or something else. What is the "else" in you latest-greatest stackup?

Air sealing housewrap is always a good idea, but it's pretty lousy to use as your PRIMARY air barrier, and it's an expensive way to try to air seal a gypsum board ceiling, which is easily caulked at a fraction of the cost. The air leakage of caulked painted wall board was behind the very definition of "air barrier" that became enshrined in building codes. Caulking the structural sheathing to the framing (anywhere it touches, and caulking the bottom plates of studwalls to the subfloors, etc, makes the sheathing & framing part of the primary air barrier, which is FAR more robust than using housewrap or taped exterior foam as the primary air barrier. That doesn't mean you skip taping the housewrap or exterior foam- you do, and it's still "worth it", but it's a lot harder to accidentally compromise the air tightness of the sheathing that with air-tight housewrap (which is something of a joke). Housewrap's primary function is as a weather resistant barrier against bulk water incursions, not an air barrier.

BTW: If you're installing more than R7.5 on the exterior of a 2x6 wall in climate zone 5, there's no point to installing 2-mil nylon (MemBrain) on the interior. Wallboard with standard latex paint would already be an adequate vapor retarder. The more exterior foam-R beyond R7.5, the even greater dew point margin you have at the sheathing, and the greater moisture resilience. MemBrain is sort of a band-aid when you're right at the margins, and is a real lifesaver when you need it. But if you have more than 2" of exterior foam (any type), you simply don't need it.

See this now-classic bit o' bloggery:

http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing

and this

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-install-rigid-foam-sheathing

and this (you may have to take a trial membership to read them, since they've been moved behind their pay wall):

http://www.greenbuildingadvisor.com/articles/dept/musings/installing-windows-foam-sheathed-wall

Where the housewrap ends up in the stackup iof a foam-clad wall depends on how you mount the windows. If the glass is roughly co-planar with the exterior of the foam & siding, the housewrap & window flashing go on the exterior side of the foam. If roughly co-planar with the structural sheathing, use a crinkle type housewrap, and put it between the foam & structural sheathing, properly lapping the window flashing to the housewrap.

In a zone 5 location with attention to details and a reasonable footprint you can hit Net Zero Energy performance levels with a 2x6/R20 + 3" polyiso sheathing type wall, U0.25 windows and an R60-ish attic. Using reclaimed roofing polyiso it can even be reasonably inexpensive compared to other means of hitting that performance level.
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26 Oct 2016 09:55 PM
You might want to reconsider advanced framing. It isn't that difficult, basically just 2x6 on 24" centers, and plan your windows and doors so at least one edge lands on an existing stud. Ladder wall connections and two stud corners are easily learned. My framers had never done them before and found them pretty easy to adjust. Since you are building yourself, it also make the walls lighter and easier to erect. Headers are all called out just google advanced framing. A lot of people, myself included do not opt for the single top plate because of sheetrock additional labor and walls are easier to erect. every stud lands under a truss so makes a stronger wall, with less studs. FWIW you talked about picture framing your windows with furring, my window company would not warranty unless they were solid to framing, so the only option was to mount them to the sheathing and cover the nailing fins with the rigid insulation. If using furr strips to mount siding I found 3/4 inch plywood and a hours table saw time to be a better, cheaper solution to 1x3, or 1x4's
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27 Oct 2016 11:38 AM
My latest and greatest stack up keeps changing in my head LOL. I'll need to do some more thinking. My thought is I have the two rolls of house wrap, so why not use them somewhere? Sounds like window choice will play a role. I'd like to use a new construction style window with a integral J channel to save on exterior window trimming. That's something I've never done and getting it wrong can mean major water issues.

I want to genuinely thank everyone for their help! I've already learned so much. I hope I'm not coming off as a Idiot. This is just a lot of information to process for someone who hasn't ever heard of it before. When I built houses for a living, no one around here seamed to really think much about the science behind what we did. We just kept churning out the same walls because they "worked".

Advance framing just isn't an option for me. The building inspector is working with me somewhat but if I mention any non-standard building practices, he says right away I need an engineer. Not only would that add some cost, we have an engineering shortage in this area. I can't find anyone that can even start to look at the project for 6+ months. I really need to start building in the spring.

I'm also not sold on advance framing. If I'm very generous with my estimating, AF would save me around $300 in the cost of the framing lumber. Now my studs are 24" on center so I need to step up to 5/8" drywall at a minimum. There goes a third of my savings. I've now also made it harder to install the Rockwool insulation and most fun of all, I have to reconfigure all my doors and windows to account for the new framing. I may make for a stronger wall (I think there is some debate on that) but so would footer to truss ICF. I just don't think it's the best way to go for me.

That's good to know on the windows. Although I don't know if it's much of a concern or not. I don't think I have never seen a window warranty honored. they seem to always find a way to deny the claim. Anyway, probably a good idea to at least try and stay within the warranty.

Thanks for the tip on the furring strips. I have done the same thing many times but I usually use 1/2" PT plywood for under siding.
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27 Oct 2016 01:51 PM
The difference in whole-wall performance between 16" o.c. 2x6 framing and Optimum Value Engineered/Advanced Framing is about R1.5, R2 at the absolute most. Thatzit. OVE/AF can make sense for tract home builders seeking the lowest cost performance when building 3 standardized designs in a 150 home development, but it's really not worth chasing for custom house design- the additional design & engineering costs are never recovered in either material & construction costs, or additional energy savings.

Going to 24" o.c. with 2x6 without taking it to the OVE/AF limit doesn't require any analysis, and is about the same structural capacity and same amount of board-feet of lumber as 2x4 16" o.c. construction. The whole-wall thermal benefit there is about R1, but worth it, since it's at a lower cost (or should be), and at the very least not a cost-adder.

With furred out siding, on top of foam, if using milled lumber NEVER use 1x3s- they tend to have a lot more bow & warp, but worse, they split much more readily than 1x4s.

Plywood or OSB furring isn't as rigid as millled 1x4s, and often needs a tighter fastener spacing in order to achieve reasonable wall flatness. That isn't a big deal if you're installing 1.5" or less of foam, but at 2" + the fastener costs go up. You have to use pancake head (not pan-head) timber screws long enough to penetrate the stud by a minimum of 1.5". With 3" foam, 1x furring, 1/2" sheathing the minimum screw length would be 5.75", so you'd be buying 6" screws. A bucket of 250 FastenMaster HeadLok at 6" runs about $150, or 60 cents per screw. With 1x4 furring it's still pretty flat at 24" o.c. spacing, so for a typical framed wall you'd be looking at 5 screws per furring per story. If you have to drop that to 16" o.c. to get reasonable wall flatness it bumps up to 8 per, a $1.80 cost adder per furring/stud.

There is no need to use pressure treated furring in rainscreen type construction. The wetting quantities are low, the frequency of bulk water wetting is limited, and the drying capacity is HUGE.
Bob IUser is Offline
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27 Oct 2016 02:11 PM
RE: strapping - If you have a sawmill in your area, rough pine or or planed one side works great for strapping over foam -it's a little thicker and usually much cheaper.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
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27 Oct 2016 03:04 PM
We have a few Amish saw mills close by. I'll have a chat with them.

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27 Oct 2016 08:26 PM
I disagree OVE 24" o.c. framing is a stronger structure, 16" oc has more bite into your structural panels, and a truss midspan on a double top plate is no concern. Header hangers have given cold climate builders major problems with frost behind the drywall, and the drywall walls will get pretty spongy with 1/2 high strength.

My framing approach uses a 16" frame but doesnt follow 16" exactly depending on window, door and end of wall layout. For example, if a window needs to be centered in a room and the 16" layout results in a 3-6" cavity next to the window king stud, Ill remove that stud from layout and have a 19-24" cavity in that particular spot. Only catch is sheathing panels, so when I sheathe the walls I plan my sheathing layout as I'm scratching out my wall layout with the intent on minimizing lumber so all panel edges have a stud.

Also, around windows most framers use way too much lumber, you do not need a stud underneath the ends of the sills, ever unless its cut into the shoulder stud, no double sills, alot of times you only need a cripple stud above a header at a truss location, think of above headers as a horizontal stud cavity, those blocks can go in after truss layout is complete as the sheathing will already be adequately fastened. Bearing points from girder trusses I use 2x4 inside a 2x6 wall, SIZE headers, you'll be shocked what you can use with lvl.

2 stud corners and drywall clips, never frame 2 studs on either side of a partition wall, ignore partition walls and install 1 horizontal block centered on the drywall taper seam, drywall clip the rest. My point is OVE doesnt necessarily mean stacked 24" oc framing, you can take a standard layout, look at it prior to building and visually see what you can eliminate.

Using these concepts and you will be under 20% framing. Also, why are you hung up on 2 rolls of housewrap? thats like 7 hundreths of 1% of a typical house, even less if its woven junk.
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31 Oct 2016 04:15 PM
Ok, I've been running the numbers. it would seem the cost penalty outweighs the benefits of a 2x6 wall. Even budgeting heavily in favor of the 2x6 wall, I still come to the same conclusion, a 2x4 wall will cost less. On top of that 2x4 walls are easier to build + raise with my makeshift crew. I'm certainly open for someone to tell me I'm wrong about this.

So my stack up in to out now looks like this;

Drywall, caulked to the studs
2x4 studs with Rockwool R15
OSB sheeting, caulked to the studs and seems taped
3" of foil backed Poly Iso, taped at all seams
Furring strips
Siding

greentree;

The method you describe sounds somewhat like how I was taught to frame. We always built RO sections first, run plates and then decide layout. It pretty easy to cut your stud usage down without sacrificing sheathing support. Partition walls were blocked as you described and tied at the second top plate.

I'm not hung up on the house wrap. I just figure if I have it, why not use it. I want to do this mortgage free so I'm trying to budget this out down to all the little details. I know I'll miss or forget about a lot of costs that add up. So any savings I can find, I plan to take advantage of.
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31 Oct 2016 04:45 PM
I would use house wrap even if I had to buy it. In your case (existing non Drainwrap), under the furring.

I'd use non foil faced foam (preferably EPS) if you can get it for the same $/R cost (a little drying to the exterior is better than none). Damp sprayed cellulose if you can get it. Airfoil electrical boxes on the external walls.
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31 Oct 2016 05:12 PM
At 3", faced or unfaced the polyiso would be an order of magnitude more vapor tight than the interior latex on wallboard, so it doesn't really impact the drying capacity of the wall significantly.

The wall still needs a weather resistant barrier (WRB) such as housewrap or #15 felt in the stackup. Which side of the foam it goes on depends on the window installation & flashing details. If it's an "outie" with the glass roughly co-planar with the siding it goes between the furring & foam. If it's an "innie" with the glass roughly co-planar with the structural sheathing it goes between the foam & OSB (and use a crinkly type such as Tyvek DrainWrap to provide enough drain space and a bit of capillary break.)

Damp sprayed cellulose is definitely easier to get a perfect fit with than any batt solution, if you can find an installer. Dry blown at 3-3.2 lbs density would be fine too, it doesn't have to be super dense-packed if you're installing 3" of exterior foam.

The "whole wall R" of the fiber insulated wall with 3" of polyiso will run about R25-R27, which would beat IRC 2015 code minimum even in climate zones 7 & 8, and with similarly optimized design on areas you could even make Net Zero Energy with a solar array that still fits on the house.

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01 Nov 2016 08:00 AM
T-sox,
Cant you do 2" foam to utilize 6 9/16 jambs?
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01 Nov 2016 09:44 AM
Wow, those R values are lower than I would have thought. Maybe high enough, maybe not. this is going to require some more thought. Maybe the 2x6 wall is worth the extra cost? I only plan on building this house once after all.

I do plan to use the house wrap as a WRB but I haven't decided where the windows will mount so I left that out for the time being.

As far as damp sprayed cellulose goes, I really like that idea but I haven't been able to find anyone that does it, rents the equipment or even knows what the heck I'm talking about (I'm guessing they know but are playing dumb). Everyone points me to blown in FG behind fabric.

I could probably do blown in cellulose behind fabric if that would be better. That would almost certainly cost less than the rockwool too.

greentree; I'm sure I could do 2" foam to utilize 6 9/16 jambs but if I do that I've gone from walls in the R35 range down to what I'm guessing would only be R20 at that point. That's a huge difference. The jamb depth is the least of my concerns. I want a warm house :-)
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01 Nov 2016 04:32 PM
An R25 wall is WAY above code-min, and as noted, when combined with other upgrades is good enough to get to Net Zero Energy. Bear in mind that a code-min 2x6/R20 wall typically comes in around R15 whole-wall, after thermal bridging, with the R-value of all the layers & air films added in. Taking it to R25+ yields a 40%+ reduction in heat losses from the walls compared to code-minimum.

Solar is getting cheaper fairly quickly, as well as incrementally more efficient (= more watts per square foot of roof area) and taking it to the full R30 may not ultimately be "worth it" by 2020. PV costs ~$3.50/watt (installed, before subsidies) in the US right now, but in Australia where the market is more mature it's about AUD$1.65/watt (= USD$1.25/watt). At US prices (even after the 30% income tax credit) it MIGHT still be financially rational to go to fully R30 whole-wall in a zone 5 climate, but at Australian pricing probably not. We will very likely see pricing that low by 2020 in the US. Spending the money that would have gone into another inch of exterior foam to hit R30 on a slightly bigger PV array may very well be the better investment, depending on how your state & utility remunerate exports to the grid.

Dry blown fiberglass or cellulose in netting is usually more expensive than damp sprayed, due to the labor costs of installing the netting. Damp sprayed cellulose is usually more expensive than R13 batts, but it can be competitive with R15 rock wool. JM Spider is a fiberglass than can be damp sprayed at 1.8lbs density (IIRC, without netting, but I've never used it.)
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17 Nov 2016 02:40 PM
I'm back again.

Selling of our current home is moving along very quickly so I've been very busy the last couple weeks. I have found some time to do more digging and come up with some more questions.

I have decided that the Windows will be best secured & sealed being installed directly to the sheathing. This means the house wrap will go directly over the sheathing. This will also afford me some flexibility since I'm going to be under a time and budget crunch. If I don't get the exterior Poly Iso or siding on right away I can still get the Occupancy permit and get my family moved in.

My stack up should look like this;

Drywall (hopefully caulked to the studs)
2x6 studs (insulation TBD)
OSB sheathing (caulked)
House wrap
2" of foil backed Poly Iso, taped at all seams
Furring strips
Siding (My wife is leaning toward Hardie plank siding now)

I have some new things to sort out now.

First question is about insulation. I am leaning towards Cellulose sprayed behind netting. I've sprayed Cellulose behind walls before so I'm comfortable with that. The netting install is something I could have my family help with since they have been asking to help with something. This would also bring the overall out of pocket for the whole house insulation down some from the rock wool. The issue is this makes it impossible to caulk the drywall directly to the studs. The netting becomes a barrier. The netting can be glued rather than stapled which would mitigate the problem somewhat. Is this a major issue or no?

The second question regards the sheathing. I had someone tell me recently that a better way to seal the sheathing is to come back after the wall is raised and spray foam the perimeter of every stud bay. This means no extra time for me while nailing on the sheathing which I like but it does seem like a little extra work on the back end. The great thing would be this is something else I can have my Mom or Dad do to help so that's a plus. Is this an acceptable way to seal the sheathing to the studs?
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17 Nov 2016 04:36 PM
A bead of caulk on the framing just before you apply the drywall works fine with stapled mesh. Many insulation pros staple the mesh first, then apply wood glue with a brayer after it's already up, then blow the insulation the next day after the adhesive is set. Others just use a tight staple spacing and forget the glue, but a bead of caulk will reliably seal, filling the air spaced in the mesh as the drywall is pressed into place.

In a zone 5A climate in order to prevent the cellulose from settling over time in a 2x6 framing cavity, a simple studwall needs to have a minimum density of 3.4lbs per cubic foot. With the 2" of exterior polyiso you might get away with 3.2lbs, due to less seasonal moisture cycling, but this is dense-packing, not old-school 2-hole method. It's hard to hit 3.4lbs with a single stage rental blower, though not impossible wit practice. It may be cheaper/better to hire a contractor with damp-spray equipment and use an adhesive-loaded "stabilized formula" cellulose, at which point the density isn't as critical. With damp sprayed cellulose you can skip the mesh.

A bead of polyurethane caulk (don't cheap out with painters caulk- a polyurethane sealant is the right stuff) needs to go under the bottom plate of the studwall, and between any doubled up top plates. You can caulk the sheathing to the framing inside each stud bay after the sheathing is up, which is quicker & easier than caulking the studs as you go. It doesn't need to be an expanding foam caulk.

With a powered caulking gun the caulking effort doesn't take much time at all- it's worth the investment, even as a one-off DIY project. The ones for smaller 10oz tubes of caulk can be had for under $200 at box stores, but for the larger diameter 20 oz tubes it's usually pushing $300.
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17 Nov 2016 11:14 PM
I would consider damp sprayed Cellulose if I could find anyone that did it around here. I have called pretty much every insulation contractor around here and no one does it. I found one a little over an hour away but they weren't interested in making the trip.

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