Structured Analysis

I am a structural engineer and my first reaction is why more steel columns and beams were not used, especially given the large open spaces and large windows. Without doing an analysis it is difficult to determine whether this structure is over-engineered. The external insulation you are using should mitigate the thermal bridging that would occur through all of these LVL’s and sistered studs, but I am not sure you’ll be able to acquire a decent amount of insulation value in some of the areas I can see in the pics without using spray foam insulation on the inside.

Got to love over engineering.
Some would call it above code.
I like to refer to it as built right, and built to last.

Small question, Are those I beam joist hangers ?
They do not look like the ones I googled.

The engineer and architects reply to your overbuilding question is correct. Trades guys are always putting in their un-informed (and usually unwanted) opinions about building structures. It’s almost an unwritten rule that the builders have to gripe about the architect and engineer.
This drives me nuts- it’s not the builder’s job to stir up doubt and confusion in the client’s head. It’s bad business and it’s ignorant.
And i’m a builder- not an engineer or architect.
Don’t listen to the trades talk about anything related to architecture or engineering. Lots of fantastic tradespeople think they know everything, and unfortunately never hesitate to offer their opinion to anyone who will listen. Sometimes a building site gets worse than a bunch of gossipy high school students.
Structural engineers spend countless years studying math and physics for very good reasons. This is your house- dont screw around!

Scott, I’m curious - whereabouts do you think we’ll have an issue with the insulation? I was actually wondering if it make sense to spray the roof headers from the outside (above the windows, etc.). Where else where you thinking?

David - I believe they are I-Beam joist hangers… at least I assume they are!

Neal - I couldn’t agree more, but I was definitely curious about it. I really don’t want to overbuild, but I obviously want to build the best we can. We’re clearly well over code, and I’m quite happy about that.

Regarding the areas that will be difficult to insulate, it’s hard to tell exactly from the pics but these areas come to mind:

- that hatched pattern of wood on the roof above the celestory windows (I think you have no choice but to use spray foam to insulate there)
- the roof headers you mentioned (although in order to spary them from the outside you have to plan accordingly to allow whatever cladding you are using on the outside there - rigid and flat insulation might be a better choice)
- anywhere you have a bunch of packed studs or LVLs that are exposed to the outside (like in your main pic on this entry, but it’s hard to tell if they are exposed to the outside) as that is where a lot of thermal bridging will occur.

Also it seems those celestory windows at the top of the house, even though they will provide a lot of light will be a massive source of heat loss in the winter, especially since hot air rises and it will collect there (unless your ordered quadruple glazing). In the summer they are going to result in a lot of heat unless you have awnings (which in don’t think are in your design, nor would they likely look good there)

Yeah, we definitely have to spray at the top of the clerestory… I think we’ll be spraying a lot (all of the garage, all of the overhangs, the walls in the living room, the roof, all of the headers, etc.) Although we’re planning on having exterior rigid insulation everywhere except the living room (we couldn’t change it because of the required brick ledge).

I agree that the clerestory will be a large source of heat loss in the winter… but there isn’t much we can do. I’m thinking we might put a fan up there, which will hopefully allow us to circulate the air a little better.

However, we are taking a few steps to reduce the heat gain in the summer:

1. The windows will actually have a “screen cladding” on the exterior. We’ll actually be shading the windows from the outside, which will essentially make it look like a large lantern (at least when it glows at night). We had originally planned for overhangs/awning to help with the shading, but I hated the way it looked… hopefully the exterior screen will help.
2. 2 windows will be electrically operable, which will allow us to open them to vent the hot air. I’m hoping a fan will help the cause as well as well.

I’m actually placing the clerestory order today, so I’ll inquire about the quadruple glazing… I’m not sure if it’s even an option though (they hadn’t mentioned it previously).

Jeremy,

We strung our window guys along for a while - over time (and especially in the current economic conditions) other “options” became available for the same price. We pushed hard on price, and ended up getting triple paned doors and windows for all the large openings. For small openings, a good mid-level double pane window should be fine.

If you do an energy model for your house, you will probably find that if you use high-quality windows, they will NOT require overhangs or shading - on their own they will handle heat gain. The only thing that becomes an issue is glare - more of a visual discomfort vs. energy problem.

As for the structure, I am surprised that there wouldn’t be more steel - when you get three or more LVL’s together, in many situations it’s more efficient to use steel. However, steel requires more coordination and it is harder to attach wood to. It also has a lead time problem, so unless the contractor thinks ahead and is good at lining up his crews, it can stall a framing job.

So, on many jobs, it might be nice to leave it at the discretion of your contractor - have your engineer give equivalents(or better yet, your contractor should be asking for them) - wood or steel in particular spots.

“Over building” can be argued ad nauseum! Just remember, that many codes are bare minimums. Small structures with big openings for glazing need a lot of rigidity and shear built into the minimal areas left over.

Better to overengineer than underengineer. Also, I’m sure plenty of trade guys are used to working on spec projects which are much less demanding than yours. If they are comparing work they’ve done in the past to your work, I can totally see why they might think they can “build your house for less” essentially.

Angelo - I’m curious what you define as “high quality” windows? Is there a particular brand that you recommend? We ended up going with Marvin Integrity throughout the house, mainly because the price vs performance appeared to be best. I recognize there are other options, but they were all significantly more expensive.

I must admit, it’s good to hear that everyone thinks the structure is inline with what it should be. I was a little concerned at first that we overshot it, but it seems like we’re in a good place.

For both performance/price point and aesthetic reasons it came down to Kolbe & Kolbe and Loewen. Kolbe & Kolbe were a little more affordable, but the fit and finish wasn’t quite as good as Loewen. The fact that Loewen uses FSC wood (and had a nice vertical grain fir for the interiors) helped make the decision for us.

See some additional comments here:
http://www.denver-modern.com/windows_doors/

Marvin makes very good windows - in some cases the Integrity series can take temperature swings better than metal clad, in that the material doesn’t expand/contract as much. However, from my brief research at the time they were limited in their sizing and didn’t have quite the same clean lines of Loewen or K&K.

Don’t worry about the beam “over-sizing” issue. The issue at hand isn’t failure (your building collapsing), it’s about building performance and stiffness. Proper engineering means you won’t have to worry about window seals failing, plaster cracking, or roof sheathing distorting under load and leaking because you did your structure right. Stiffness is a building’s best line of defense against weather and age.

We use a lot of Integrity windows. It’s one of the very best performing double glazed windows, and the price works for most of our clients. Loewens are more beautiful, and have a little better thermal performance, but are a significant step up in expense.

For triple glazed, Loewen has the best combination of aesthetics and performance, if the budget does not allow it we go for Canadian fiberglass triple glazed (Thermotech, etc.). Using triple glazed windows can significantly reduce your heating system size and cost, the price can be almost flat in the end if you are careful with heating distribution reduction.

As to thermal bridging, make absolutely sure you have no spots where bare steel touches uninsulated exterior sheathing. If that steel gets winter cold, moisture will condense on it inside your walls, and bad things happen. Spray foam is your friend. A good layer of foam on all exposed steel will keep water vapor from getting close.

The best examples of thermal bridge reduction is found in the Passivhaus (passivehouse) German construction system. It’s how they make their radical heating system reductions work. An exterior rigid foam blanket, even if it’s only 1-2″ thick can do wonders in reducing problems at spots where interior insulation can’t fix (posts, beams, window framing).

Have just finished reading through your entire website. Bravo.

You have taken some flack along with some kudos for your ‘green’ efforts. I believe that by publicizing your decision making process and discussing the alternatives you have done a lot more for the greening of Toronto than if you had quietly put in all of the latest technologies, regardless of cost and NOT publicized your efforts.

Keep up the good work.

Cheers
John

Other than joining the chorus of approval for “over-building”, I wanted to call attention to the I-joist hanger photo. I’m no expert (as I’m sure someone will be quick to point out) but I believe that the section of the I-joist sitting in the hanger should be filled in with blocking to allow fastening of the hanger to the I-joist. Check with the supplier(s).

I look forward to following your project.

Pierre

Hey Pierre - I thought the same thing, but apparently that additional block (or “web stiffener”) is only required in certain situations. According to the iLevel website:

Web stiffeners are required if the sides of the hanger do not laterally support at least 3/8″ of TJI joist top flange.

In our case, each I-Joist is fully supported by each hanger… and glued to ensure a squeak-free floor.