But seriously, our foundation design looks like Eastern European public art:
That top section is a grade beam, and the long/wide sections are pinned to ledge. In fact, nearly every one of the footings will be pinned to ledge. (For you flatlanders out there, ledge is the rocky substrate frequently lurking below the topsoil in hilly regions like New England.)
So far they've formed most of the footings, and the plan is to pour the footings early next week and then pressure-wash the whole area to clear away the organic material (AKA dirt). The piers will get formed and poured after that.
Ted will surely post more about the hows and whys of our foundation, and we'll put up pictures as well.
The joists in question are 24-inch roof joists from Nordic Engineered Wood in Quebec. These bad boys will allow us to have a clear span roof (no internal bearing walls) that's stuffed with 24 inches of insulation (mostly if not entirely cellulose).
The reason Marc wins this round is that Eli (the builder/architect) and Ben (the structural engineer) were agitating for flat trusses. Trusses have some structural and workflow advantages, but joists have the virtue of being extremely easy to insulate.
For those of you not in the know, trusses are made of dimensional lumber (usually 2x4s or 2x6s) joined together with metal plates. They are exceedingly strong and relatively inexpensive. The problem is that it's hard to properly insulate all the gaps, and the wood and metal turns into a thermal bridge when it traverses the building envelope.
As an alternative, Marc has long wanted us to build the roof with I-joists. I-joists are an engineered product, which means they aren't made from old-fashioned wood like the Pilgrims used. Instead, they're an unholy adhesive-bound combination of solid wood flanges (the top and bottom bits) and OSB (particle board's stronger cousin). They're called I-joists because the cross-section resembles a capital I.
Unlike trusses, I-joists are very easy to insulate, and the relative lack of material means less thermal bridging. Our I-joists will be a flabbergastingly-deep 24 inches, which is practically unheard of for residential construction. We want this depth for insulation and also for strength.
It was initially hard to find joists this deep. In residential construction they usually max out at 16 inches, and although Weyerhaueser's commercial line includes 24" joists, they aren't available in New England. Fortunately I discovered that our French-speaking neighbors to the north make deeper joists that are relatively easy to obtain.
Ted promises to write a post explaining the technical challenges with using I-joists and why Eli and Ben weren't initially on board.
After months (years?) of theoretical house planning, suddenly everything is progressing at top speed. Eli (the local builder/architect) is trying to hurry our job along so it will fit into his crew's schedule, which means we're suddenly moving very very fast.
In the last few weeks we:
Completely revised the floor plan, obliterating roughly 500 square feet
Reversed the roofline
Revamped the windows
Committed to a pier foundation
Cut down several more trees (*sigh*)
Just today Ted had very long conversations with both Eli and to Marc, working out the roof assembly (24" I-joists) and many other issues. More talking needs to occur, but much progress was made.
I'm completely wired/exhausted from all of this, and I still have heaps to do. The good news is that we seem to be heading in a good direction. After only a day of excavation the site looks downright buildable, albeit in a Vermonty ledge-riddled way. And I prefer the smaller floorplan, even though we bid adieu to our walk-in closet. (Resale value? Bah!)
Photos, floorplans, renderings -- all coming soon!
Today I added a tag cloud to the website. That's the list of tags in different font sizes in the right sidebar -- the font size reflects the relative frequency of posts with that label. I added the tag cloud in honor of today's post with the unhappy label "Expensive mistakes."
I would love not to share this story, but it's been a big part of our pre-construction process, and it would be disingenuous not to talk about our mistakes as well as our accomplishments.
I'm going to describe our unsuccessful and expensive collaboration with a structural engineer who wasn't a good match for us. It's not Ted's or my goal to criticize anyone here other than ourselves -- I certainly don't want to malign an honest and qualified professional simply because we weren't on the same wavelength. My hope is merely to share our experience so that other owner-builders might learn from our mistakes.
Things might have gone better if I'd had a clearer understanding of what a structural engineer does. I thought structural engineering was simply about doing load calculations and making sure that we're not building something that's going to fall down. Our design has a few tricky bits, including an interior cantilever around the main staircase, and I thought that was the main sort of task a structural engineer performs.
I failed to realize that we needed a structural engineer who is every bit as obsessed with energy-efficient construction as we are. The engineer we hired is very experienced and highly competent, but he is firmly planted in the world of conventional building. This was an unfortunate oversight because structural engineering is heavily concerned with the building envelope and the foundation, which are probably the two most critical aspects of Passivhaus design.
It didn't help that our foundation is turning out to be very tricky indeed. Our building site slopes downhill from west to east and our house design is oblong, but for optimal passive solar performance we want the long side to face south. The engineer warned us multiple times that it would be more difficult/expensive to orient the house that way, and we assured him repeatedly that rotating the house was not an option. He therefore suggested we pay a landscape engineer to do a grading plan, which would detail all the earthwork required to build a frost-wall foundation.
In hindsight, someone should have proposed we build the foundation on piers, since this would minimize the amount of earth-moving and keep the overall cost down. (Also, a foundation on piers would look really cool!) But this never happened, and we instead paid for a grading plan and then a foundation plan that will require heaps of concrete, overzealous bulldozing, and masses of expensive compacted fill.
Was our engineer wrong to propose this? He had suggested numerous times that we reorient the house along the milder grade, and we repeatedly told him that solar orientation was more important to us. It was not ridiculous for him to think that we were prepared to foot the bill for our obstinate tree-hugging ways.
We knew when we hired him that he wasn't experienced with super-insulated construction, but Ted and I thought we might be able to educate him along the way. We were willing to pay for a few extra hours of his time if it would leave him with energy-saving strategies he could use on other projects. Unfortunately, "a few extra hours" ballooned into a lot of revisions when he didn't see the logic of our requests. And to be fair, a lot of our questions and proposals were pretty loopy, so I don't entirely blame him for ignoring our occasional valid points.
Our energy guru Marc met with him last August to discuss the project, and Marc immediately told us that he didn't think we'd hired the right structural engineer for the job. But by then we felt it would be expensive to change course and hire someone new. I suppose this was the "good money after bad" threshold. Sigh... lessons learned.
Other than the grading plan, not much engineering work happened over the winter, and by spring we decided to bite the bullet and find someone else. Marc hooked us up with someone who seems to be a much better match, and we may have a viable and affordable foundation plan before too much longer (blog post forthcoming).
We are wrapping up work with our old engineer, and hopefully there won't be hard feelings on either side. It's been a blow to my pride to discover I'm not immune from making mistakes, and of course it's been a blow to our budget and schedule as well. But we will recover, and if this is our biggest expensive mistake we will be lucky indeed.
Here's hoping that font size in our tag cloud stays very very small!
Geeky details I won't bother explaining, such as 4/16/4/16/4mm triple-glazing and a plastic warm edge spacer of Psi=0,038
In Europe, dozens of manufacturers make windows like that, but in North America hardly anyone does. The best North American window vendors are making a reasonable attempt, but they all fail on at least one of Ted's and my requirements:
Serious Windows' highest-performing windows are casement, not in-swing, which means they open outwards with a little crank at the base. This is mechanically inefficient, and it also limits the size of windows they can sell. We have some gloriously big south-facing windows in our dining area, and we don't want to make them smaller. Also, their best SHGC is 0.42, which is not as good as the standard Passivhaus windows from Europe.
Canadian companies Accurate-Dorwin and Thermotech Fiberglass didn't sell in-swing windows last time I checked. My main complaint about out-swing windows is that the screen is inside the window, which I simply don't like. And yes, I know about retractable window screens, but I'm still not jazzed about opening a heavy triple-paned window with a crank.
Inline Fiberglass makes a tilt-turn frame, but they still aren't big enough for our front windows. They offered to sell us a modified doorframe full of glass, but c'mon! Also, their best windows use Serious glass, which has slightly lower SHGC and VT than the European glass.
I could list a few more North American vendors, but they are mostly using Inline frames and Serious glass, whose shortcomings I listed above. And you'll notice I didn't mention the big-name American manufacturers -- as far as I know, Marvin, Pella, and Andersen aren't even trying to build Passivhaus-worthy windows.
Ted and I are therefore likely to order windows from Europe. If money were no object we'd want something like Optiwin's Passivhaus-certified three-wood window, but sadly we are on a budget, and ever-plummeting dollar doesn't help. But the high-end American windows I listed above aren't cheap either, and there's enough variety and competition in Europe, particularly from the former Eastern bloc, that we can get something good for an acceptable price.
We haven't made our final decision yet, but we're likely either to get German windows manufactured in Slovakia or Polish-made windows. We rejected some Lithuanian windows, not because we have anything against Baltic states but simply because the importer is based in DC and we want to work with someone more local. If we're handing someone a five-figure check just to place the order, we want to be able to drive over and hassle them from time to time.
We're still waiting on a couple more estimates, but once we make our decision I'll post all sorts of titillating window specs and diagrams for your perusal.
[Added on 2011-10-03: It's possible I've been a little too hard on North American glass manufacturers, since there's apparently some difference in how they test glass performance in Europe, but I stand by what I said about tilt-turn vs. casement operation.]
I was recently asked a simple but excellent question: What makes it passive?
The word "passive" turns up a lot in green building, and it can refer to several different things. When I say we're building an almost passive house, I'm referring to the Passivhaus building approach that was standardized in Europe and inspired by energy-efficient building methods pioneered in North America. The Passive House Institute US site summarizes:
A "passive" house achieves overall energy savings of 60-70% and 90% of space heating without applying expensive "active" technologies like photovoltaics or solar thermal hot water systems. Energy losses are minimized, and gains are maximized. Superinsulation and air-tight construction minimize losses.
Passivhaus certification is somewhat easier to attain in Europe than in North America, mostly because of their relatively moderate climate, but also because you can buy much whizzier building products over there (see my post on European windows).
After a considerable amount of waffling, Ted and I decided not to go for full Passivhaus certification, but we're still planning to use as many passive house techniques as we can (superinsulation, avoiding thermal bridges, sealing the house extremely tightly, using mechanical fresh-air systems, etc.).
In passive solar building design, windows, walls, and floors are made to collect, store, and distribute solar energy in the form of heat in the winter (Passive Solar Heating) and reject solar heat in the summer (Passive Solar Cooling). This is called "passive" solar design (or climatic design) because, unlike "active" ( solar heating, photovoltaic, etc.) solar systems, passive solar systems do not involve the use of mechanical or electrical devices, fans, pumps, etc.
Passive solar home design was undoubtedly discovered by cave dwellers who noticed that south-facing caves were more comfortable year-round than caves facing other directions (cave dwellers in the southern hemisphere would have chosen north-facing caves). This is because the sun is angled low in winter and high in summer, meaning that winter light and heat will penetrate deeply into a south-facing cave, and summer sunlight will be blocked by the cave overhang. Furthermore, a cave with a solid earth floor retains winter heat gains even after sunset, because earth floors have a high thermal mass which absorbs heat during the day and then slowly releases it at night.
The cliff-dwellings at Mesa Verde in southwest Colorado are the textbook example of passive solar building. The dwellings face south and are protected from the hot summer sun by a gigantic overhang, but during the winter they are bathed in light.
The advent of mechanical heating and cooling systems made it easier for builders to ignore passive solar techniques. The problem got worse when people started building houses with ginormous windows, often facing a nice view in a direction other than south. Ted's parents' house has a great room with floor-to-ceiling windows facing a lovely view toward the west. Every afternoon the room is flooded with light, which brings welcome solar gains in winter (they can turn off their heater for much of the day) but way too much heat during the summer.
It is much easier to achieve Passivhaus certification if you maximize solar gains with clever window placement, thereby reducing the need for mechanical heating. Our building site isn't perfect for passive solar since we have quite a few trees blocking the sun toward the south, but it's not too bad, particularly since most of those trees will lose their leaves every autumn.
To get the maximum bang for our passive solar buck, I used SketchUp to simulate the solar shading at different times of year. I entered our latitude and longitude, and then I told SketchUp to show me what shadows will form on different dates (including the date of this blog post). Our house has big windows facing south, so they'll be our primary source for solar gain, and I tweaked the length of the roof overhang so it will admit plenty of sun in winter without allowing too much unwanted summer heat:
We're being careful to order windows with a high solar heat gain coefficient (SHCG), which means that the glass won't filter out too much of the warm sunlight. Again, refer to my future post on windows for more about SHGC.
Ordinary houses breathe through leaky joints and poor seals, losing heat and wasting energy. But our house won't leak, so we'll use a heat recovery ventilator (HRV) to admit fresh air and expel stale air, transferring heat from one stream to the other.