Letters from Sweden - a window's tale
In our last installment of the Letters from Sweden we looked at the panelization technique used by the Swedes and some of the administrative barriers to its adoption here. Today we'll pick up where we left off and consider some of the products that go into the Swedish panels and how they support the panel building technique. We'll look at windows, how Swedish window units are different than US window units, and how this plays out in the construction.
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In Sweden the windows are installed into the wall panels on the flat (inside up) after they are framed. The windows are designed to fit flush with the panel's outside so when they go in the window face is flat on the table flush with the framing. They install the window units with adjustable fasteners which allow the windows to be squared after the panel is installed and is stable. Think of the adjustable european hinges in your kitchen cabinets. If you've built something bought at Ikea you've handled these. You know how they allow you to adjust the door panel to sit square with the cabinet frame. The Swedish windows are mounted with hardware that allows the same adjustability to the window unit. Lifting the panels into place is likely to cause some sort of movement in the panel, and this adjustment allows them to be made square after installation. When the wall panels are flipped over to install the siding the windows are trimmed and a metal sill extension added.
Here you see the Swedish window after the panel is flipped, before siding is installed, the metal sill in place. In the second image the siding and trim has been installed lapping over the window unit.
In contrast our windows in the US don't included adjustability like this. In the field our windows are fastened into the rough window openings from the outside using something known in the industry as a "nail-flange". The windows project from the wall surface and are self trimming providing a standing edge fore siding or trim to terminate against. The siding and exterior trim are installed over this flange locking the window into the construction. If the house ever settles or moves the wall will take the widow with it racking the frame, likely making the window stick or jamb. Not as likely to happen with on site construction, but a distinct possibility with handling large wall sections.
Here you can see a typical US style window, Andersen. The nail fin clearly seen at the edge of the frame, fits against the sheathing. The rest of the frame extends out creating an edge for the siding to terminate into.
Here a typical US style window installation, Eagle. You can see the siding material is butted directly against the side of the frame.
So can we build using the Swedish panel technique with our US style windows? That is a good question. Perhaps. It would require a change in sequence. Our windows would have to go in as the first step on the outside work on the panel. But the more the panel is handled the more likely the window is to be out of adjustment when the panel is finally installed. If the window was damaged in handling it would require a good deal of the panel to be disassembled in order to replace a window unit because of the siding attached over the nail flange. The Swedish windows could be swapped from the inside leaving the siding and trim in place. So yes, it can be done, but the US windows obviously have a lower tolerance for error so to speak. The Swedish windows anticipate these issues and accommodate them.
Thanks to Scott Hedges for the Swedish factory photos. Next we will look at wiring.
Previously:
Letters from Sweden - panel building in Sweden vs the USA
Letters from Sweden - Europe is different, Sweden is not, sort of..
Letters from Sweden - land of modern, land of prefab
Letters from Sweden - conversations with an expatriate builder
Technorati Tags: modern design, modern house, modular house, prefab house
Continue reading "Letters from Sweden - a window's tale"
There are a few more photos of this stage of the work also posted at the 
click through the link below for more photos.
Remember you can see photos of the entire build on the Flickr 
First off we have issues with construction inspection conventions in the US. Construction must be inspected before it is insulated, closed in, and the underlying work is obscured. Framing, plumbing, and electrical work are all inspected at this point. The modular industry has established a practice of third party certification to work around this, but this method would require a different routine as the proportion of site and factory work is not the same. Modular is more or less done with the set of the modules. Panelization requires the field inspector to pickup more of the inspection work again in the field, and I predict the blurring of lines of responsibility to elicit resistance. This is essentially an administrative obstacle, but real enough. This obstacle does not exist in Sweden.
Second are issues of products and standard construction practices. In Sweden products are designed to facilitate this panelization. In the US they are designed to be installed in the field. This purposeful design of construction products allows the Swedes to optimize their process. They are not fighting with the construction to break it into panels, like we would here. Next we'll look at some of these products in more detail.
Previously:
Across their courtyard you can see the 
Here you can see the interesting pattern of siding they have chosen. It appears to be a smooth faced cement board siding panel, but laid up in varying exposures. This is a treatment you might often see on a traditional cedar shingle siding and its really great to see this reinterpreted in a contemporary material like cement siding and used here.
Check out the Flickr set for this house where you can see 
