Air Sealing: Step 03 - Poking Holes

Now that the whole house is nicely wrapped in our Intello air-barrier, we have to deal with all the funny spots where we need to (for one reason or another ) break through that barrier. That would mean things like windows and doors, electrical outlets, plumbing and ventilation lines and all the other things that move around inside of our walls.

This is the part of air-sealing that takes the most attention and care and usually a fair bit of on-site imagineering, no matter how much planning you do.

Windows:

Windows are, of course, one of the biggest trouble spots for air-sealing. After all - it's the spot where you put a big, operable, transarent hole in your nice, thick, tight wall. While we don't have too much control over the window-unit itself (other than staying away from things like double-hung windows) - we can do a lot to make sure that our air-membrane is sealed well to the frame.

Below you can see our original detail for the air-sealing. We were going to run small strips of Intello around the window and tape to the wood frame then cover it in rigid foam insulation and finish it off by adding all the interior trim and wall covering.

Window Sill detail - Interior

In the final detail we decided to install the rigid foam first, then installing the air-barrier. Because of the amount of rigid foam, we were concerned about water (from condensation) getting trapped under it and unable to dry out. So, like everything else, we encase it behind our air and vapor barrier, that way no humid indoor air can worm its way behind it and cause problems. The operation is actually very straightforward, it just requires the right tapes and a fair bit of attention and patience.

As-Built window sill detail: Layers pulled back for clarity

Our first step, shown below, is to install the rigid insulation and then apply the strips of Intello. These are then taped to the window frame with Pro-Clima's Profil tape.

This tape (below) is super cool - its another fabric tape, but has a nice split release back to make doing these inside corners much easier. 

Tescon Profil Fabric Ai-Seal Tape

The first edge is applied to the window, then the second piece of release paper is removed, allowing us to seal to the Intello. 

The 3-way corner where the bottom and side meet is taped with a pre-made corner. 475 has a great little tutorial on making these and they ensure that we have a totally continuous seal all the way around. 

Once the window frame is taped, all the overlapping Intello membrane seams are taped, forming a tight seal. Once the trim goes on the windows, it'll cover all the tape you see here and no one will ever know about all layers going on behind. 

Outlets and Electrical:

For electrical outlets and switches, there are a lot of techniques to air-seal. Some choose to seal the back of regular boxes with mastic or foam and seal around all the wires. Other assemblies apply another layer to the interior of the wall that is thick enough to run all the wires and boxes in, inboard of the air barrier. This technique (the 'service core') is how we built out the Solar Decathlon house last summer. This time around since we had, by design, consolidated all the plumbing away from the exterior walls and limited the amount of outlets in the exterior wall (by placing them in built-in furniture esp) we decided to try a special outlet box made for air-sealing. Above you can see the final sealed box - these boxes have a wide flange around the outside which makes taping really simple. In addition, you can see slots at the top and bottom - these are designed to be filled with spray foam once installation is complete and form a nice seal around the wires themselves without any mess. Really cool product and there are similar versions for all the typical electrical uses (switches, 4x's, etc)

For wires that will run to boxes which aren't mounted in the exterior wall (above) we use a special gasket made by Pro Clima - these have an adhesive patch which seals tightly to the air-barrier, and a tight EPDM rubber gasket that the wire penetrates through. This forms a tight, but flexible air-seal around all the wires.

Plumbing and HVAC:

Plumbing and HVAC penetrations are similar - we bought gaskets sized accurately to the pipe or duct diameter. These large EPDM gaskets are then taped to the air-barrier. Below you can see the HRV in our loft mechanical space with the intake and exhaust lines. These insulated ducts have to go all the way to the exterior of the house and so have tight gaskets to seal them off. 

Loft Mech-room with HRV and Zhender insulated Ducts

Intake Duct penetrating the envelope to the exterior

Same thing with plumbing - below is a waste line in the basement penetrating the crawl-space wall. All this just takes a bit of planning ahead to make sure you have the right gaskets on-site when its time to run the lines. This is important as these can't really be applied after wards and so all the sub's need to understand exactly what the plan is ahead of time. 

Plumbing penetration in the basement

Everything on the first floor is just about sealed up at this point. We still need to do all the big gable-end windows and once that is complete we'll be ready to test our house and see how well we did on all this sealing. 

Air Sealing: Step 02 - Wrap it Up

Intello'd ceiling from ground level

Now that we're membraning, there are so many great 'Wrapping' puns flying around on site its almost hard to keep them all straight. 

Yes, its finally time to start sealing up our cabin. We got signed off on our Rough Framing, Electric and Plumbing inspection on Tuesday (applause, applause - thank you very much) and so now it's time to close the walls up and get to insulating. As I've said before, the air-sealing on this project is critically important, we're super-insulating and we bought good windows and we oriented glass to the winter sun and all that other nice stuff - but the most important thing we're doing is fully controlling the air that moves into and out of the house and salvaging as much heat as we can from the exhausted air with our ERV. 

Intello on the loft cathedral ceiling

To seal the inside of the house envelope completely - we're using Pro-Clima's Air Barrier, Vapor Retarder & Cellulose Netting membrane called Intello. It's a semi translucent white (to help see as we're blowing in insulation) high-performance membrane made of a plastic called Polyofin with Polypropylene reinforcement. The membrane is stapled to the inside face of the studs and then seams are taped with Pro-Clima's tapes. The rolls are light, big (about 5' wide) and cover a lot of ground real fast, just like the Solitex membranes on the exterior.

Zoom of the Intello - the grid you see is the reinforcement polypropylene strands

Once the entire interior surface is covered with membrane and taped up, we'll start filling the walls with dense-pack cellulose insulation - using the Intello to hold the insulation in the stud bays. One great thing about this membrane as opposed to standard cellulose netting is that thanks to the reinforcement we need many fewer staples. Most netting requires staples every 1/8", two rows per stud. This basically coats the studs in metal making installation of finish materials a real pain in the neck. The Intello only requires one row of staples, spaced every two inches. So thats much easier to install and will make our lives a lot easier when we go to install the interior woodwork. 

Intello, 2" OC staple, parallel to the stud

And even better than all that - it glows white. So now it feels like your inside of a giant marshmallow when you go into the house.

Intello ceiling, view from the loft looking south

But why all this attention to air sealing? Well, most houses let fresh air flow in through cracks around windows, under doors and around walls. In addition, if you have things like electric outlets, ducts or especially, recessed light fixtures in your ceiling - its a good bet air is flowing in and out of your house around those pieces of equipment.

All this air movement is a bummer for two big reasons. One is because you're loosing all the air you spent a bunch of energy (and money) on to heat or cool until it feels comfortable. This tempered air is just flowing out into the world and mixing with unconditioned air (either too cold or too hot) that is flowing in, which you then need to use more energy on to condition all over again. Most homes change all the air in and out somewhere between 4 and 12 times an hour (whats called ACH - air changes / hour). On a certified Passive house you need to be below 0.6 ACH at 50 pascals (thats a prescribed pressure to measure ACH at) - although most folks try and do much better than that. So if we can limit the amount of uncontrolled air that leaks into and out of our house, and then use a machine called and ERV to bring fresh air into and out of the house, we can drastically cut the amount of energy needed to heat or cool our space.

The other reason we care so much about air-sealing has to do not with air, but with water. Since our building assembly is so tight and our insulation so complete, we need to be very careful and attentive to how water vapor moves into and then (more importantly) out of our walls, ceilings and floors. In a drafty, poorly insulated (or uninsulated) wall - air moves all over the place, so if water somehow gets inside a wall (through vapor diffusion and condensation, or during the construction phase before everything is water-tight), that water vapor can easily dry out and get carried away by the air moving through the wall.

In a super-tight wall, however, there is the real possibility that if we're not careful, water vapor might get trapped inside, condensing on cold surfaces, causing rot, attracting insects and doing all the other terrible, horrible, very bad things that water does to houses.

Our intello wrap is going to function as a vapor retarder - that is, it'll stop any vapor pressure-diffusion that would drive moisture into the wall assembly from the interior. This is required by code (though air barriers are not) and most builders include some type of membrane (usually polyethylene sheeting or paper-faced batt insulation) that performs this function even in the cheapest types of construction.

But, and this is where the building codes are a bit mixed up - air sealing is, in fact, MUCH more important for preventing vapor movement than installing just a vapor barrier. Now: sure - vapor and air are different and just cus' you have an air barrier doesn't mean it's a vapor barrier (un-painted drywall is a good example of this). But - as the famous diagram from BSC bellow illustrates so well - air transported vapor is a much bigger culprit than vapor pressure-diffusion for moving water into wall assemblies.

For a great article on why air-barriers are more important than vapor barriers, see this one by our favorite master of building science over at GBA.

So- the Intello is a vapor retarder, thats fine - but more importantly it's also an air barrier - and we seal it tightly around each and every penetration and intersection. And since our wall's outer layers are vapor permeable - if any moisture does get in- it can easily dry to the outside and get vented away under our rain-screen facade.

In order to figure out if our assembly will function ok given all the issues listed above - we create whats called a Vapor Profile (for more on this - check out another article at GBA). We assign a value to all the materials in the wall assembly, (called a Perm value) and this way we can see which direction, depending on the season, vapor will be moving. 

In our Vapor Profile above, you can see that we expect exterior drying to occur during summer and winter thanks to the very high perm-rating of our sheathing and House-wrap.

The Intello will act as a vapor retarder and so any vapor hitting it from either side will be unable to pass through. However - Intello is what is know as a smart-wrap, that is, it actually changes its performance characteristics when conditions change. For us, that means when its hot and humid - the Intello actually changes its molecular structure and modifies its vapor permeability from 0.17 (very close to impermeable) to 13.2 perms! This means that in the summer, the assembly can dry to both sides. Very cool technology and even though not strictly necessary given our assemblies ability to dry outwards - it's still very good to allow drying both directions as much as possible.

Jason and Carrie should have the rest of the shell finished up soon, then on to air-sealing our windows and penetrations - so look for a post on those soon.

Things are Rolling Along

North Side with the new roof

It was a busy week up here as we've been getting ready for our rough-framing inspection as well as the rough plumbing / electrical inspection early next week. On the exterior - we've finally topped out for real! the last of the sleepers / roof-framing went in early this week and our roofers made quick work of getting us dried in (though thanks to our backup Solitex roof we've been 'dry' for a while now). 

John installing the last of the roof board sheathing

The finish roof boards are visible from below and so lots of care had to be take with the framing and finishing: lots of sanding, staining and careful handling. You can see the finished detail in the image below with the exposed rafter tails and the board sheathing giving a real 'cabin' feeling to the house. That is the same stain we'll be using for the siding as well. The new roof has changed the profile and proportions of the house quite a lot and we're all real happy with it. 

Inside, the gang have been working hard to get electrics, plumbing and ventilation ready for inspections. One exciting new piece is the kitchen island which Jason started framing yesterday. Below you can see the main kitchen living space under the loft. The 'Core' of framing you see in the center houses kitchen appliances as well as the bathroom inside. By moving all the utility and services to this little core we moved all the plumbing and most of the electrics off the exterior walls. This simplifies our air-sealing and increases the efficiency of our insulation. It also just makes things a bit easier to have it all centralized rather than spread throughout the house. 

Below, you can see the kitchen framing on the left, and the end-result (eventually) on the right

And outside I've been picking away at the decks. The entry deck is finished up and thursday I began framing the big south-deck. There is going to be plenty of space here for outdoor eating as well as storage space for wood (for the wood-stove) and more than enough room for folks to stretch out a bit. The decks also do a lot to embed the house down into the ground as well so it feels less like its towering over the landscape (although - the 20" of soil we'll bring in all the way around will help with that as well!)

South side with all the windows in and the deck framing. No door just yet though cus' of some ordering mix-ups.

View of the lake from the south deck.

South Deck framing.

So - things are coming along. A little less dramatically then during the framing stage (thats always the way though) but by the end of next week we should be moving into the finish woodwork stage and then we'll really begin to see the house come to life.

White Pine and the Woods of Northern Wisconsin

An enormous old-growth White Pine along the Cathedral Pines trail

You can still find many buildlings up here constructed using a 'log-cabin' technique, that is: piling up full logs to form the walls of a structure. While the original log-cabins in this country were mostly built as part of logging camps or the homes of poor farmers - this method of construction spread to wealthy summer homes and lodges by the late 1800s and early 1900s. Today, log cabin style homes are still quite popular and you can even buy log-cabin 'siding' that mimics the look of the traditional materials. While our new high-performance cabin is most certainly not a log-cabin, we are still very interested in the history of the region and have tried to integrate certain aspects of the material culture here into the new house in several ways. 

One way we're trying to do this is through a generous use of traditional white-pine as an interior and exterior cladding material. All the vertical siding on the house will be stained White Pine and the interior will be almost entirely wrapped in Pine as well, with a simple clear oil applied to maintain as much of the original character of the wood as possible and keep the inside very light and open. 

Eastern White Pine, of course, was one of the most important species in the development of this region - and much of the mid-west US as well. White Pine was, at the time of colonization, spread extensively across the eastern and great lakes areas of the US. However, it's now estimated that less than 1% of these original tracts remain, due to extensive logging starting even before the Revolutionary War and continuing until the present day. Most of the largest and highest quality old-growth wood was harvested in the middle and late 1800s however as the railroads and technology allowed loggers to work in areas that would have been too expensive or remote previously. 

Photograph of loggers with large White Pines in virgin forest land

Originally very valuable to the British as material for the masts of sailing ships, White Pine became a primary building material in the mid 1800s and was used for everything from finish flooring to wall studs and structural beams. A very soft wood, White pine is creamy colored for the most part, with yellowish or sometimes blueish rings and grain figure (the blue often means that the wood was infested with a fungus because the un-milled logs sat for too long in the lumber-yard during the summer months). Pine doesn't have any of the natural weatherproof ability of, say, a Cedar, Redwood or Ipe - but with regular staining it can be used as an exterior siding material just fine. Its very easy to work with and good wood will stay much more dimensionally stable than lots of other similar woods (Hemlock or Spruce esp) - one of the many reasons loggers searched it out disregarding many other species along the way. Distinctively, White Pine contains five needles per bundle (Red Pine has only 2) and the bark is a grey-silver which starts smooth but develops into deep crags as the tree ages.

Thick bark of a particularly old White Pine along Cathedral Pines trail

While the simple fact of existence of such huge forests explains much of the particular history of this region - the history of the logging in Wisconsin is also closely linked to the growth of Chicago and the prairie states. Logging operations in Wisconsin have always been centered around exporting their crop: after all - just cus' you cut is down doesn't make it valuable, you still need to be able to get it to where the market is (which was not in wisconsin). In the central and western parts of the state, the Wisconsin River provided the main thoroughfare to mills and markets downriver, esp. in and around St. Louis. On the eastern side of the state - it was all about Lake Michigan and Chicago. Chicago's growth as the center of the lumber trade coincided with two particular trends, the growth of a market for timber in mid-west and prairie states where trees were scarce but farm-land valuable, and the extension of railroad technology. 

Logging operations in Northern Wisconsin before the 1880's were mostly along rivers and streams. These natural highways allowed loggers to harvest and move their timber to Lake Michigan's Green Bay where they would load it onto barges and ships. These loads would then travel to Chicago where they were purchased by national firms and distributed south and west. 

River Drive

Typically, lumber camps would be erected in the late fall, with logging operations beginning during early winter. The frozen ground allowed horse or oxe drawn sleds to move great volumes of timber to the river banks where they would be stored until spring. Once the spring thaw rose river levels, the river drive would move lumber down to small coastal mill towns like Oconto or Marinette. White Pine was especially suited to this technique - Hemlock (another common species in the north woods) was said to float too low in the water to drive successfully, and native hardwoods didn't float at all - making them all but impossible to move from the north woods to the mill-towns. 

Horse-drawn winter sled with Pine lumber

But with the extension of the railroads, lumber companies were free to range further inland and expand their operations year round (since they didn't have to rely on frozen ground for easy movement). Because Chicago was able to turn itself into one of the most important railroad hubs during the late 1800s - the market there naturally became a vital middle-man between the Wisconsin lumber jack and the Prairie farmer. After railroads began to expand, timber harvesting expanded wildly and soon - like in the rest of the country, virgin White Pine stands began to disappear. The end of the river drive technique also meant that species such as Maple and Hemlock could begin to be harvested in addition to Pine. 

See the figures in the bottom of the ravine for scale

A great read on the development of the wisconsin forests and its relationship to chicago is William Cronon's fantastic history: Natures Metropolis. 

Sadly, this has left only a very few small areas of original old-growth White Pine left. Yesterday I was lucky enough to be able to go visit one of the largest stands of such forest left in the US - an area called the Cathedral Pines, located in the Nicolet National Forest. 

You can see in the areal shot below, the stand is a rough circle - approx 30 or 40 acres of original Red and White Pine and Hemlock - which stands out against the younger growth around it. It is very easy to access and the main trail loop only takes 40 mins or so depending on your speed and ability. There were a LOT of fallen trees though - so if your not up to climbing up or under I wouldn't recommend. 

This area around Archibald lake was once a large logging camp for the Holt and Balcom logging company (active here in the late 1800s and early 1900s). Later becoming a summer home of the owner and his wife, Lucy Rumsey Holt, the area of the Cathedral Pines was put aside at Mrs. Holt's request and in the 1960s passed to the state government. Now, the pines represent a tiny snapshot of what the pre-colonial forests covering this country must have felt like. 

Almost all of the pines here stand over 120' tall - with several notable specimens over 150' and massively thick. While they haven't been dated too closely - most are thought to be well over 200 years old, with some possibly as old as 400 years. It's a beautiful park and its amazing to think that this might be one of the last areas of a a forrest type that once covered half a continent but now might disappear entirely. 

Cathedral Pines. The dead tree in the center was killed by acidic Blue Herron droppings (note the nests up in the tip-top)

Today - we're lucky to have even a few of these areas left. While we are following in the tradition of building with White Pine and appreciate its importance to this region - the lumber we purchase these days is all harvested locally to the cabin and entirely grown on large plantations or new (less than 100 years old) stands. Thankfully, we have a great lumber company nearby that understands the importance of protecting and managing Wisconsin's forests well. The work of companies like this and the FSC, along with progressive state and federal policies, allows us to continue to use materials that evoke the history and culture of this region without the same catastrophic environmental effects created by historic logging practices. 

Exterior Detailing is all About Layering

"Un-Battened" house form

You may have noticed that the images of the house so far have been pretty "streamlined". As you can see in the image above - there are very few protrusions or extra elements on the main house. This is mostly to keep our thermal and air boundaries crystal clear and facilitate efficient sealing and weatherproofing. Running a big sheet of membrane over a surface is orders of magnitude easier than trying to seal around things like joists or rafter tails. The 'tight' form is also a by-product of our attempts to eliminate all thermal bridges and keep the overall massing of the house very simple. 

But, there are exterior detail elements that will be present in the final house - things like rafter tails, window trim and siding all need to the added - and to do that, we add lots and lots more layers to our little house. 

As you can see in the detail from an earlier conceptual rendering below - we are going to have exposed rafter tails and exposed board-sheathing on the roof eaves and rakes. This material effect replicates a construction detail seen on many of the other cabins in this region, and is very common on lots of old 'summer' cabins you'll find in other rural areas. The deep rakes help a great deal to shade our south windows in the summer time - and deep eaves will increase the wall durability by keeping water and snow far away from the finished siding. 

Zoom of a early rendering - you can see the exposed rafters and board-sheathing

But having a rafter extend out through the thermal boundary was obviously not going to work with our  energy-efficiency goals. So we decided to build all the roof elements up on top of the thermal boundary. Below you can see John and Jason installing 'sleepers' onto the existing roof. Basically, these are just 2x4s and will have a final layer of sheathing installed on top of them - this creates a nice vented cavity which will eliminate any worry about ice-damns in the future. (though - with all our air-sealing, that really shouldn't be a problem anyway). The finish roofing will then be installed on this upper roof. Once the rafter-tails had been cut (which took a hot-minute or two!) the install process goes really quickly. It also gives us, in effect, two roofs -which means I don't anticipate we'll have any call-backs  cus' of leaks for the first couple hundred years of this house's life. 

John and Jason adding 'Sleepers' above the Solitex Roof Membrane

The walls are a bit different than the roof, but the same principles apply. We basically take our simple house form and add layers to achieve the desired finish - whether that is about aesthetics, waterproofing or any other environmental condition. 

We're installing what is known as a 'rain-screen' facade on this house, and that basically means that the siding is only one layer our of weather defense. We expect some water to make its way behind the siding - that's why we wrapped the house in a high-tech, water-proof membrane. The finish siding is held away from the membrane by battens which allows air to flow freely behind it - this means any moisture vapor back there will be able to dry very easily and increases the durability and lifespan of the siding significantly. 

Lake-Side, first layer of wall battens and most of the roof 'sleepers' installed

The first layer on the walls is to apply vertical 1x battens over the weatherproof membrane, which can be seen in the image above. Even though we are going to have vertical siding - we can't just apply horizontal battens since this would create lots of drainage problems on the back. So a layer of verticals, then a layer of horizontals, then the finish siding. 

Pretty straightforward - but like everything else, it gets complicated around windows and doors. As you can see in the detail below, at the window sills we need to go through a bunch more layers in order to protect the house correctly. After the main water-proof layer has been installed, we'll add a sloped exterior sill which is then taped to the window. Any wind-driven rain or snow that makes its way behind the trim will get directed outwards by this slope. We've then got some rigid foam  insulation and the exterior trim - in this case 2x material. 

Below - you can see a little mockup we made on Friday to test some ideas about how to really put this all together. You can see the window trim and a couple of sample siding boards in lower right corner. 

Zooming in, you can see I've pulled the layers back a little bit so you can actually see how things are put together. The idea is that most rain water and snow will flow off the primary window trim (01) (A) since the sill is sloped outwards. If any melting snow or wind-driven rain (C) does make it uphill and get behind the trim, it will flow out over the tape (2) and rigid foam insulation (3) under the window. Since the siding is held off the waterproof membrane - this water will simply drain out the bottom without causing any trouble. 

The first layer of wood battens are vertical and you can't see them here - but you can see a special product used to seal off the cavity behind the siding. We add Cor-A-Vent SV5 Siding vent (4) at the top and bottom of the walls and around all the windows. This product allows water and air (B) to flow through easily but has a built-in bug screen to keep all the critters from living in the nice warm, dry space behind our siding. I know the bees gotta live somewhere . . . but it isn't gonna be here I'm afraid. 

Then a final layer of horizontal battens (5) and the White-Pine vertical siding (6). The siding and trim will all be stained - but the battens will be left raw. Since they will be protected from UV damage, and are vented enough to let them dry out if they ever do get wet - we really don't need to worry about them very much at all. 

Its a lot of pieces and work, I know. But it will make for an incredibly durable and effective exterior protective coating once its all finished. 

Operation Fenestration

Bay-Side push-out casement window

Friday we received delivery of our windows and, except for a few exceptions, we're almost all installed. Keep in mind this house is used mostly in the winter - and all the heat for the house comes entirely from a wood stove. As such - it's very important  to capture as much passive solar heating as we can during the winter months. So window detailing and layout was something we spent a lot of time and energy on during the house design. After a lot of testing and back-and-forths, we ended up going with Marvin Clad Ultimate Casement windows for the majority of the house. There are a couple awnings for special spots and some fixed triangles for the gable ends - but mostly its big 5'x5' double units punched through our thick walls. 

Since we are trying to gain as much heat as possible, the plan and orientation of the house are driven to a large degree by this solar access. We placed the private bedrooms and entry spaces to the north side of the house, allowing us to open up and add lots of glass to the main living room and kitchen space to the south. The south wall is almost entirely glass and should bring in lots and lots of daylight and heat during the winter months. 

Looking South towards the living room with the lake to the right

The install went very smooth, and I'm very impressed by the Marvin units. They are regular flange-mounted units with Doug-Fir interiors and Aluminum Clad exteriors. The hardware and exterior cladding seem real durable which is a real serious consideration given the harsh climate up here. There is a whole lot to say about why we decided to go with domestic windows instead of importing some true Passive-House certified units. But instead - I'll simply say we've gone the imported fancy-window route in the past, and the combo of schedule, cost and logistics weighed very heavily on purchasing locally this time around. 

John and Jason installing one of the big ones

But - even though these are traditional window units, the install was still complicated by our super-thick walls and our concerns about long-term durability in a tough climate. One thing we really wanted was to be able to mount the windows in the center of the wall assembly. This way we eliminate any super deep window sills on one side or the other. They are still gonna be deep (around 6") - but at least there aren't any 14" deep sills anywhere. 

Additionally - there are real thermal benefits to mounting windows as close to the center of a wall assembly as possible, though I won't go into all that business now. 

Typical window installation details

In addition, by mounting in the center of the wall, we definitely decrease the likelihood that any water will seep its way in - increasing durability (so long as we deal with the deep exterior sills well). We also liked the aesthetics of thick walls with window 'punches' which is created by the set-back glass. 

An inset window from the exterior. The Solitex wraps in under the window flanges as a first level of flashing.  We'll then add insulation and tape to the frame for a second layer.  

So to do this we lined all our window openings with plywood first, then mounted 2x nailers around the center of the window opening. Just compensate for the added thickness when building the rough-openings and thats that. 

Below you can see the finished mounted window on the left, and the prep'd window opening on the right. The plywood also serves to help tie the walls together really well and increase our stability. Its certainly not the simplest detail and not nearly as easy as just mounting the windows to the outside, but I really like how protected and covered the windows now are. 

South-East corner looking toward the bay

regular 2x sill, 3/4" OSB ties the two walls together, then 2x nailers

All this extra wood will get covered by rigid foam insulation and then taped (a topic for another post). We'll then build Doug-Fir extension jambs for everything to finish it off. 

Typical Window Sill detail. Foam insulation over the extra framing. 

The windows on this house are very high-performing units and we selected glazing types to match the specific orientations. The west side units (sort of North-West really) and the north are all 3/4" double-glazed LoE II 272, argon filled. These have a U of 0.3 and and SHGC of 0.29. But on the south, we wanted to allow lots of solar heat to come into the space - so we opted to go with Marvin's triple glazed 1" LoE 180 Argon filled units. These have a better U value (0.25) and a better SHGC (0.39) - but they are a bit more expensive so we only used them where we knew they would have the biggest impact on the overall heating of the space. 

Marvin Double-Glazed unit.

I'll be sure to post more about these window details as we move into the air-sealing phase. But for now, its just nice the be able to keep the rain on the right side of the wall.

South End view - almost done framing the gable-end