Map from our code books

i'm in that blob of purple that runs through colorado.

I'm zone 6 according to the map but I think the 7A/6 line is much closer to me than this map.

I live in zone 7a

Ahip, got any projects in 7b?

Not currently but yes I have done a few projects
up there. All before the energy code thank goodness

I've done a couple in Zone 8, including one that gets close to PH standard (R80 walls, R100 roof up in Churchill). But that one has yet to be built. I'm not holding my breath

I'm down in that tiny pink blob of Zone 1 in Florida, although having worked in Zone 6, I can say it's equally not fun to design for.

Climate Zone 4!? I'd never degrade myself by going so low. ;) 

My entire career has been in zones 6 and 7. It was a shock doing local projects in zone 5. It almost felt like cheating to have R-values so low . . .

People live in florida zone 1? I thought it was just for gators.

Yes, gators and 4th vacation homes.

that's like a winter image of the jet stream....coincidence?

So we recently had the entire roof of our house insulated with spray foam between the rafters. I should remind you that I'm in Zone 7 bordering on 8 I think. Anyway the foam was not cheap. Once it started snowing, I could see each rafter telegraphing through the bit of snow on the roof. I was so embarrassed that I've ordered enough additional EPS to cover the entire roof (on the inside of the house) with 2 more inches. As an architect, I just couldn't live with seeing the thermal bridging, even if the additional foam cost will never be paid back. Ugh.

Donna, the cavity insulation is probably fine, but it sounds like that wall could use a layer of exterior insulation under the cladding to insulate the thermal bridging at the studs. 

Bowling_ball, can you add spray foam to the inside of the rafters? Or are they covered? Not perfect, but might mitigate the bridging cheaper than covering the roof…(your solution is the better idea, even tho it’s more spendy)

Proto, I've got a local manufacturer who makes their own vapour-open faced EPS sheets with integral furring strips. These will go right over the rafters and framing to eliminate those thermal bridges. Probably less labour involved too.

Can you see the line between thicker snow at the eaves and over the garage, compared to over the heated area of the house? [maybe the photo is too dark or small?] The rafters are also subtly indicated in the thinner snow above the conditioned area. They did not plow the snow this way. It’s a diagram of the heat leaving the house.

In our area, the climate has historically been mild, and they put minimal insulation in. Most houses only have heat; A/C is a new enough thing that it’s sort of a unique selling point when looking to buy. When they did put in insulation, they made vented attics. This house caught my eye because the clean line that traced the conditioned area illustrated this so well. I’m guessing that this example has never upgraded that attic insulation from whenever it was built.

So, only in winter do we get a view of how much heat we are losing to the atmosphere. That example above just illustrates the low R-value of attic insulation installed back in the day as conventional wisdom for economy. When you ask the A/C sub why they only put R-8 flex duct in a vented attic here, they say it’s good enough. But the real answer is: it’s a pain in the ass to insulate the ductwork properly. They like just hanging flex off the rafters with straps, not figuring out how to insulate the pathways thru the attic.

So, we’re losing energy in the summer and the winter & no one can see it. At least until it snows or we have a hard frost and you can see the result on the roof.

Excellent explanation, thank you very much. I had clued into the different tones of color on the roof, but assumed this was from using a scraper to take off snow from the roof and just the inherent extents that could be reached at the time. Visions from my childhood of my dad's make-shift extended-snow-shovel-thing reaching up to the roof and pulling down massive piles after a big dumping.

Yeah, the folks in Tahoe right now are all about the snow rake

Snow rakes are popular here too... and I'm always laughing when I see the lazy men outthere only half-ass clearing the snow.... hummmm, yeah, pretty sure you just caused a bigger problem.

6" foam inside and 1.5" foam outside would not pass Canadian code because of the ratio of interior to exterior insulation. Can you explain the rationale?

sorry, my bad, there's also batt insulation over the foam inside to fill the cavity.

That makes it worse, not better. The ratio of outboard to inboard (with the dividing line being exterior sheathing) is very prescribed in our Canadian code to prevent condensation (and rot) on the sheathing. For example, in my neck of the woods we need at least 50% of the wall insulation value to be outboard. Maybe Non Sequitur can explain it better - I've never worked on a project with cavity insulation in my professional career, the economics just don't make sense here, once code is accounted for.

Bb, it’s not like that in Ontario. We do cavity insulation with minimal continuous exterior all the time. There is even a way to only use cavity insulation that meets sb10 too, but you need 2x8 to hit minimums.

But with that in mind, I have many projects with an almost 50/50 split between ext and int insulation. Just hard to convince most clients on the extra external foam.

NS, the 50/50 ratio meets all Canadian zones so no worries there. It's when you add 3/4" or 1" of outboard rigid that causes problems. And yeah, technically you don't have to do outboard here either, but that would leave you with very minimal glazing. That's actually much safer than adding an inch of rigid, because the sheathing can still dry.

BB, can you expand on the glazing comment? Is your permitted fenestration % tied to the Uvalue of your wall assemblies? But yeah, 25mm of rigid on exterior does not really do much other other than rack up costs.

NS, we use the provincial energy code for buildings, which is very slightly modified from the MNECB (2014). The ratio of inboard to outboard is in the NBCC so you should be aware of it's y existence at least. But to answer your question, yes, the area and performance of glazing is tied to the overall wall performance, and can be traded off. For example, prescriptive code is R27 effective walls at 29% fenestration with a minimum u-value of 2.0. The numbers get pretty wild in terms of trade-off - I can't do the calculations right now but on a recent project the walls only had to be R12 effective because there was something like 20% fenestration. It goes the other way, too. If we want 40% fenestration, the wall insulation goes up to something nutty like R45 effective. So we typically use energy modeling even we can as it lets us get away with a little less insulation while still meeting code.

Thanks, and fascinating. We don't rely on the NBCC in Ontario since we have our own energy codes (SB10 & SB12) that supersede it (for better or worse) but I do know that 22% fenestration automatically triggers an energy model in residential designs here (I rarely do residential). We normally use the SB10 prescriptive method (one of 3 options) for small-medium commercial projects but I'm still on holidays, I'll crack it open tomorrow to see what's in the other compliance paths. There are trade-offs available, not nothing as extreme as you list.  

We hire out energy consultants on Large projects.

BB, curiosity got the best of me, so I looked it up. What you describe above is path option B for us but we have a much simpler option A based on ANSI/ASHRAE/IES 90.1 and Chapter 2. I've never had to look beyond option A.

Ah, that makes sense. It is similar then. I made a really simple Excel spreadsheet to do the trade offs automatically. It's saved me many hours of doing math.

^ In that lower photo alone: fixed windows, paper-thin flashing, and unbacked stucco applied like peanut butter with a spatula.

the flush window-stucco alignment makes me angry... as does the cheap wavy bent-metal forms.

Wow, that’s quite the topographical wall…

And how about that wafer-thin white zone at the window heads? Why not just let the soffit run into the window head?

Proto, I'm sure the intent was for a soffit to window head... what we're seeing is a solid 25mm bead of "designer" caulking.

Lol

I see a lot of windows like those from first-year students and takes time to help them to burn it out of their system. There is a flipper culture of design thing prevailed and it is the direct result of everything you have seen in the residential media and the so-called "clean lines style" of the real estate market. Oh yeah!

I went into one of these with its owner-builder, and he was so proud of it. It was a July morning. In the big entry hall, none of the big door-sized fixed-glass sheets (aka windows) was operable, and none was shaded. I asked, "Do you notice that it's really hot it here? And do you know that it's only going to get worse?" His beaming smile started to sag a bit. "You might want to show it only at night," I suggested.

Looks like they originally intended to build out of shipping containers.

*it"

Reminds me of the first time I was in california and saw some detailing that was just so flimsy. I was shocked that some one could get away with details that wouldn't hold out a teaspoon of water. ( having grown up in the Pacific Northwest keeping the rain / water / snow out was all you were taught )