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Green Building News

An Architect’s Take on Sweden’s Factory-Built Houses

In his blog posts about home construction in that country, Gregory La Vardera zeros in on the details, including a look at wall construction of a factory home and the fates of prefab housing there and in the U.S.

This cutaway, from a Swedish company called RejnäsVillan, shows siding boards over 47mm-thick furring strips on hardboard sheathing covered with a Tyvek-like air barrier. The studs, about 7.75 in x 1.85 in., are filled with mineral wool insulation, then covered with a plastic vapor barrier. Over that are horizontal furring strips (providing space to run wires and pipes), mineral wool between the strips, a layer of particleboard, and then a gypsum panel.
Image Credit: RejnäsVillan

Update on Jan. 2, 2011: We’ve corrected the wall stud dimension noted in the caption.

Gregory La Vardera, an architect based in Merchantville, New Jersey, has geared his practice – which he operates in tandem with the interior-design practice of his wife, Karen – toward clients who have an interest in modern design or want to elaborate on a historic style. (He is among the contributors to FreeGreen, the architecture firm known for offering downloadable floor plans, some for free, some for a fee.)

But he’s also interested in how buildings can be economically built to offer a high degree of energy efficiency, which is why green-building advocates might find his “Letters from Sweden” blog series worth checking out. On Friday, for example, La Vardera focused on wall-construction details (a “baseline” assembly, as he puts it) of a typical factory-built home in Sweden, noting that even though these wall systems in most cases include materials widely available the U.S., they are relatively energy efficient and airtight because Sweden’s stringent energy code includes performance standards that haven’t yet been widely embraced by manufacturers here. Building wall panels just to merely meet code requirements in most parts of the U.S., he adds, can make it hard for manufacturers to compete with the costs of simply doing the work onsite.

“With our cheap walls factory building makes little difference,” La Vardera writes. “There is simply not enough value there to save very much. It’s just as profitable to build onsite when your walls are so cheap and simple. The Swedes, however, use the factory to make every house very high in quality, and very energy-efficient. If we ever hope to do the same we will have to turn to a similar factory process.”

A market where prefab is successful

The “Letters from Sweden” series also includes comparative observations on topics such as automated panel building in the U.S. and in Sweden, and, more broadly, why prefab has struggled on this side of the Atlantic but forged on successfully in Sweden, despite its relatively small population, to offer a wide range of design and custom construction options at competitive prices. La Vardera notes that the country’s short building season has been a significant factor in making manufactured housing viable, but also points out that economic issues in the early 1970s, when energy costs increased sharply, created a market for factory building, whose leaders focused intently on introducing efficiencies into their operations.

Like most successful manufacturers in a conducive economic environment, Swedish housing manufacturers approach their operations, La Vardera says, so that “every aspect of the design is rationalized into a known quantity of work, material, and ultimately a known price that is both profitable and viable in their market. During the time their industry was reinventing itself, the various products and fittings that go into a house were all revised, improved, and updated to integrate into this industrialized process. Contrast this with our country where almost every home is built as a unique event on each site.”


  1. lavardera | | #1

    Clarification to caption above
    The studs in that wall diagram above are 195mm or roughly 7 3/4" - deeper than our 2x8s (not the 6.5" noted). The insulation in this primary stud space approaches R30.

  2. GBA Editor
    Richard Defendorf | | #2

    Thank you very much for the correction
    The caption has been altered accordingly.

  3. user-659915 | | #3

    Panelized or modular?
    Refreshing to get a look at a well-established thoroughly systematic factory-built approach that actually works. It's been frustrating the extent to which recent modular housing initiatives in the US have been tied to style first, performance second, with a wide gulf between the low-end quasi-traditional and the high-end neo-moderne. The article mentions easy customization which suggests panelized construction (rather than complete modular prefab) at least as an option if not the standard - if this is the case it would be interesting to see an article exploring how field assembly is handled to ensure proper continuity of the enclosure.

  4. lavardera | | #4

    field assembly
    James, this post discusses the delivery and assembly of wall panel based Swedish houses:

    The focus here is more on the efficiencies of the overall process, and less about continuity of the enclosure. If you look at the photos on this blog entry you can see that the hems of the interior vapor barrier extend past the wall panels allowing them to be sealed together before the wall seams are patched closed. That is side to side. At the base plate of the wall panels a neoprene gasket is used between the wall panels and the slab, and again where second floor wall panels sit on the floor platform.

  5. user-659915 | | #5

    Field assembly
    Thanks Greg, this article and the time-lapse video clarify this issue very well.

    I've never been a fan of modular prefab because of the layout and shipping inefficiencies of the shoe-box format. I had a suspicion that if factory construction was ever going to deliver on the dream of better-made homes at competitive cost it would be through panelized systems, and it seems the Swedes have really made it work. I would actually enjoy designing for a system like this, just so long as the enclosure details were worked out on a regionally climate-appropriate basis.

  6. Scott Hedges | | #6

    I made the you tube


    I made the you tube clip that Greg posted, and I appreciated your comment. Greg's reply is complete, but I wanted to extend what he's said. I take your question about "enclosure" to be about how to seal the seams between the walls. One thing that really jumps out at me comparing our US systems to their Scandinavian system, is how little adhesive cemistry is on a Swedish jobsite. The Swedish houses seal up really as a by product of the method of construction, not as an add on.

    In the US the foam and caulk and this fantastic tape stuff might as well be the heraldic crest of the green builder - the Swedes on the other hand must be the lowest per capita consumers of caulk and foam on the planet. All the sealing is done as greg said by overlaps, EPDM gaskets and foam backer - in otherwords none of this is adhesive chemistry. The embranes aren't taped, the windows aren't foamed, etc ... nothing expands to fill anything, it is all done on tolerance control and design. This is staggeringly smart design.

    The sealing between floors is usually expressed in the external siding by use of an aluminum flashing, Greg haven't posted on this detail but it works in concert with the design of the vertical siding. If you look at the collection of modern designs Greg posted you acn usually see where the seams are. The designers usually make the seam part of the way the building looks - or add details like cornerboards to accomodate them. Mostly though the seams can be handled by a small amount of additional trim or wall board work, the air tightness however was a by product of the construction - not as an additional step.

    That concept seems to be worth highlighting as a maxim.


    Scott Hedges

  7. Scott Hedges | | #7

    James another quick comment
    James another quick comment re modular vs. panelized - the Swedes call modular constrcution, "volume element" construction and wall panel building simply "element" building (I'm translating) our language works against us with terms like modular, and prefab etc ... eventually we know what it all means but the Swedes use the terms "bygg element" which is a more accurate way to think about this.

    The more interesting thing however is that their "volume" elements are built differently than our "modules" - which Greg has outlined nicely.

    In reality a "modular factory" in Sweden is a "wall element factory" which does more of the work onsite the steps in the way the walls are built is identical in both cases because they have rationalized the construction (and I suspect have optimized it).

    In cabinet making the step where the project goes "3D" and becomes a volumetric piece of furniture, is an important moment. When you can no longer work freely on all sides and faces of a piece of furniture the way you work is contrained ... the same is true of houses.

    US builders go 3D long before the Swedes.

  8. user-659915 | | #8

    Thanks for your comments
    Thanks for your comments Scott. Even with just a cursory understanding of this approach I get a sense of a very thoroughly thought-through system that's designed to 'just work' without all the angst we currently have to endure to get a building done even approximately right. I appreciate your comment on our dependence here in the US on caulk to fix poor detailing (though just until it fails). Also the 3D effect. The shipping stresses on a flat panel are easily dealt with by the sheathing, on a volumetric box not so much. I have always found it strange that US modular prefab proponents tout the benefits of factory-controlled conditions of manufacture and ignore the inevitability of seal stress and premature failure as a result of torquing loads when hauling this big empty box down the highway at sixty miles an hour - with one side generally missing, no less, and closed only by a flapping piece of plastic sheeting.

    I'm not sure I'm clear on the distinctions you draw between the different forms of building prefabrication in Sweden. Do I understand correctly that the 'wall element' approach is what is shown in your youtube clip (which I would call panelized fabrication) and 'volume element' means shipping a pre-assembled box (which I'd call prefab modular)?

    I'm aware of some panelized construction here in the US (I'm not counting SIPS) but my limited experience of it suggests a focus on the low end, with cheapness rather than quality of construction being the prime target. If anyone can direct me to quality-oriented panelized fabricators in the Southeast US (I'm in North Carolina) I'd be interested.

  9. GBA Editor
    Martin Holladay | | #9

    Response to James Morgan
    You should get in touch with Michael Chandler, a GBA Advisor who works in North Carolina. He purchases wall panels from Builders First Source, and he talks about it here:

  10. lavardera | | #10

    James - volume vs element building
    James, you have the distinction correct. One of my posts has a video from a Swedish volume/modular builder showing their factory process. What you find is that they nearly complete the walls inside and out before standing them up to make the boxes. This is what Scott means when he says they go 3d much later than we do. So the panel builders and the modular builders in Sweden still build walls the same way. One is placed on site, the other in the factory. Here is the blog post that shows this:

    This post makes a comparison between the Swedish volume factory and the American modular factory via the videos that both post at their web sites.

  11. lavardera | | #11

    Recommend Bensonwood
    James - Bensonwood can service you in North Carolina, and is the only panel based builder I know building anything that approaches these Swedish wall systems.:

  12. user-659915 | | #12

    Thanks for the suggestions folks
    but Bensonwood is too distant for my locavore sensibilities and I already have access to crews who can do as well or better than Builders First Source. Greg has offered us a vision of something far better. What I really want is a Swedish-quality production facility within about fifty miles of Carrboro NC that will take full responsibility for the integrity and performance of the enclosure so I can concentrate on the space, the sunlight, and the setting. Is that too much to ask? ;-)

  13. lavardera | | #13

    If it existed...
    ...then I wouldn't need to be writing about this stuff! Really, you should at the least talk to them. The worst that could happen is they could overcome your admirable local commitment.

  14. user-659915 | | #14

    Local commitment
    Greg, I really appreciate that you've lifted a curtain here onto the potential for a much better way of building, thank you. It's been a revelation for me, and more than anything else I've seen discussed on GBA, I believe these systems have the potential for lifting the whole green building discussion from a boutique preoccupation to where it could really have an impact on the mainstream of homebuilding in this country.

    But for that implementation to be successful, local is going to be key in more ways than one. To take the Bensonwood example, shipping a whole house 700 miles down I-95 on a truck is just not going to happen, not for me, not any time soon, other than in very exceptional circumstances. It's not just the distance and the diesel. As well as from a considerable reluctance to outsource some of the last good skilled manual work left in these parts, the key issue is that the manufacturer's design staff have experience of our climate and really understand it - I want them to know all about a/c issues in warm humid conditions and I don't want to have to worry about them getting the vapor profile right. I want them on hand to fix things properly if (when) they get it wrong and I want them to feed that experience back into their learning curve so that the next project is even better. I want them to do this, locally and iteratively, for our local conditions, many many times a year. So get Bensonwood to open a plant south of the Mason-Dixon and we'll talk!

  15. user-659915 | | #15

    Industry fragmentation
    To Martin:
    Thanks for the tip, as it happens I know Mike Chandler pretty well and was talking to him just yesterday, though on a different topic entirely. This brings up an interesting point. Though we are very much aligned in terms of our vision for the outcome of our work, our approaches and professional profiles differ and the opportunities for us to truly pool our knowledge and experience are limited - we more often share ideas here on GBA than we do in person, though we live less than twenty miles apart. I've long beat the drum for the positive characteristics of the many tiny businesses that make up the green building movement but this fragmentation also has its downside. It's as if the US were composed of isolated villages with no state and local government, and only minimal federal standards (the mass market and the building codes) were available across the entirety of this vast country. It occurs to me that regionally-based manufacturing resources like the ones Greg describes could fill that gap and help bind those tiny businesses together into coherent local building cultures that are consistent, efficient and truly climate-appropriate.

  16. lavardera | | #16

    too soon, but never too soon to hope
    I understand James. But if there is a revolution coming in the way we build houses it has a long way to go. The big lesson from Sweden is that it is possible. A lot of interests have to be aligned to make it happen, but it can be done, and it can work. But you can't have it all right now - you either build it yourself without the assurance of a manufacturer behind it, or you compromise on delivery travel.

  17. lavardera | | #17

    too soon, but never too soon to hope
    I understand James. But if there is a revolution coming in the way we build houses it has a long way to go. The big lesson from Sweden is that it is possible. A lot of interests have to be aligned to make it happen, but it can be done, and it can work. But you can't have it all right now - you either build it yourself without the assurance of a manufacturer behind it, or you compromise on delivery travel.

  18. Greg Boiles | | #18

    To James' Local Commitment
    Hi James. You make some great points in your thread. Those sentiments are echoed by all of us here at Bensonwood as well as MANY, MANY intelligent people like yourself across the country (and obviously around the world).

    But I think where one of your posts falls a little short is in talking about distance and about proper building science application. In many cases (admittedly, not in all) the costs of shipping are completely absorbed by efficiencies and cost reductions that are inherent with pre-fabricated, panelized construction. Obviously, you have to compare like-for-like products. We recently built and delivered floors, insulated and partially finished walls and roof panels to a client in California (3,000 shipping miles with several trucks) for a price the client could not have gotten from local builders. He got a great deal and an outstanding, appropriately engineered and built product.

    While California has different envelope requirements than North Carolina, those requirements are stringent, ever-changing and not necessarily documented. We meet and address those different expectations routinely and in order to be successful, as we are, we provide continuous training to our staff, engineers, architects, project managers, wall/roof panel builders and timber framers. Training is a routine evolution here and it's given by real experts. How is training normally accomplished in the traditional construction model? We all know that answer and it's part of the current problem that you are trying to find a solution for. Because the majority of those who are doing the teaching are NOT craftsmen or experts.

    Additionally, I'd like to address the ongoing support if something goes wrong. The likely hood of having a national company around and willing to correct problems is much higher than the local guy with a pickup. You've been in the industry a while, you know how often the small operations come and go.

    As I read what I just wrote it sounds like I'm coming back at you in a negative way. That is NOT what I'm trying to do. You've got wonderfully articulate and in my view mostly accurate issues. I just have a different perspective on those above.

    I'd love, in fact we'd all love for you to come visit us some time. In the mean time we'll start working on getting a production facility built in your neck of the woods.

  19. user-659915 | | #19

    Of course
    To Greg La Vardera: I absolutely realize that what I'm asking is not coming to a jobsite near me anytime coming soon, in fact I'm resigned to the fact I may be dead before it happens, if it happens at all. In the meantime I'll just keep on keeping on and looking for the best way currently available to do what we do. But unless you know what you want, how do you know where to aim? And if enough enlightened professionals join the effort it may just happen sooner than we'd expect. Thanks for pointing the way.

  20. user-659915 | | #20

    To Greg Boiles:
    Thanks for your response. I stand by my point that it's more than shipping costs and carbon footprint, it's about developing a regionally experienced and knowledgeable building culture that includes manufacturer, designer and contractor in a coherent and closely focused team. I take your point about training and research, yet I also know that there's nothing like living with a climate for a few years to understand what works and what doesn't. So I'm delighted to hear that Bensonwood might consider expanding its reach with more regional facilities. That would be, as they say, awesome, and I'd be happy to work with you. Onward!

  21. Scott Hedges | | #21

    shipping houses
    I think James' comments are really important, as I think that any benefits from the Swedish methods are going to be because guys like the ones reading this figure out how to make all this both profitable and beneficial to their lives - because it is good for customers, profits, and their own sense of enjoyment of work. There are some important cultural and trade practice issues. James mentions "replacing skilled labor" by the idea of ordering his walls ...

    I wanted to comment about how I saw this kind of factory based building impact the lives of the people who build houses in Sweden, as far as I could tell from my time there.

    The Swedes had managed to change the supply chain in light residential construction and consequently they changed the nature of the work involved in building a house.

    The closest way I can describe it is to compare it to the work of cabinet installers in the USA. The builders in Sweden come to the job with the same level of "kit" to build a house that we would take to install a kitchen. It is not that cabinet installers in the USA are unskilled - they just need different skills than framers.

    The builder I worked for would get calls from the factory to bid on the installation of a house, the rates of what was involved were more or less given and the factory was always looking at this as one in a series of jobs (ie everyone involved expects to work together again next week) so I think bidding really just meant agreeing to take the job, meeting the schedule and price on offer -factory was not competitive bidding so much as getting agreement to perform. The factory for its part was selling houses, so they were bringing the customers to the builder.

    This was not unlike the way a kitchen design show room has a PM - who work with the customer order the job and see it into the hands of the installer, who is though not an employee often a trusted sub of the kitchen company.

    In fact the way that a family would buy a house in Sweden, was a lot like the way a person in the USA would buy a kitchen. They would go to a "store" where "salespeople" would talk to them about the features of their products. In Stockholm there the house factories had all built an "expo" so the customers could see all their choices and what the various factories had on offer. The Swedish market is small and ultra competitive. They are very "customer centric" as a result of this.

    The builder I worked for did a base line business in "installing houses", and then he did additions and remodels he had about 10 guys working for him, his remodeling work was exactly like they way we do it and he could and did build stick homes, but he did what I thought of as a "baseline" trade in working for the factory who was selling houses to customers to build "on their lots" - his crew would meet the factory trucks, the factory would send a guy and the truck driver who would work with the builders to get the house up and closed in. All the material that the "installer" would need was supplied by the factory. The effect of this was a massive elimination of PM responsibility on the part of the builder.

    The role of "GC" therefore on a new build in Sweden is radically different. The only people who build houses they way we build houses are doing something for instance very fancy or that is outside of the what the factories think of as "housing".

    The way you buy and build a house in Sweden has been rationalized away from our model (which we should be clear is looked up to world wide, and has given Americans a very high standard of housing because of our pioneering in our building systems think Chicago and the light wood frame in 18??) ... so I'm not in the "we suck at houses camp - I'm more in the how to we get better at houses camp). My view is that the Swedes took all our innovation and innovated it even more.

    The effect of this on a "build" is that there are guys in offices, and there are guys on the tools, and the guys in the office are invested in the build in ways that lumber yards and our modular factories aren't - all because they have different conceptions of their jobs too.

    There was a lot of "waiting" in a one off Swedish build. The work would happen in intense bursts, but there was very little wasted effort. Everyone would leave and do something else.

    So my view is that the Swedish builders are different skilled, and I thought the life of the guys I worked with was good, they didn't grumble about the old days when they used to frame houses, if anything they seemed to like the fact that all the work they had to do was rationalized. There was this sense of efficiency, that is recognizable no matter our language. We all can tell when things are "flowing" or when we are working slow and wastefully or don't have the tool or material we need or have to go find out something or spend our time talking or arguing ... when the walls would arrive they were connecting them, and that took skill, just like when cabinets arrive in boxes to make them all look like a perfect fitted kitchen.

    This whole system is much more "interdependent" than the "GC" model ... I think the biggest obstacle (if this offers some "green building benefit") is how we change our understanding or roles and habits (all of which are hard won and valuable to us and help us survive where we are) but also prevents change and evolution ... so this kind of discussion is really the way we have to go, a factory guy, a field guy an architect, have all got to be open to "new ways" ... the useful thing about the Swedish example is that if you are going to try something new, it helps to have an example so you aren't off in "prototype" land inventing the wheel

    This is fully mature industry, full of normal people and real businesses in real competition working for real customers with the same dislike of paying too much as customers everywhere.

    There aren't many of these "alternate realities" for us to learn from, partly because we Americans are playing at a very high level ... so most of the world looks up to us. There are only a few cultures, like the Nordics, who take our example and improve on it. that is what has happened here.

  22. GBA Editor
    Martin Holladay | | #22

    Response to Scott Hedges
    Thanks very much for taking the time to share your experience and perceptions about home building in Sweden -- very interesting.

  23. user-659915 | | #23

    Great post Scott.
    The cabinetry analogy seems very apt.The history of stick framing is fascinating and yes, this seems like the next logical step in its evolution.

  24. Dimwit | | #24

    Cool but sad :(
    After viewing Greg and Scott's excellent work it's become very obvious that the "Swedish system" has no chance of ever getting a foothold onto these shores without some sort of impetus.

    What needs to happen is some sort of regulatory scheme to force a change in the industry. State, provincial or Federal though my choice would be a Federal standard. Minimum standards that, I think, need to be addressed on the energy efficiency of buildings. Perhaps a building CAFE. Yeah, I know, CAFE is the be all and end all of good regulation.

    Buuuut! A high tide lifts all boats. A single objective, energy efficiency (BTU per sq. ft.?), never specifically addressed in how to meet it would do wonders. It allows things like factories to flourish nationwide as long as they meet an, admittedly high, standard. Let the standard supercede the incredibly balkanized building codes would be a good thing for everyone concerned.

    As it stands right now, there is a huge disconnect between the cost, the price and the value of a residential building. Builders like the Toll Brothers have perpetuated a business model that drives the subs to the lowest possible costs, the cheapest building materials and the fastest building speed to kepp the cost down. Then there's the gloss of expensive surface treatments to raise the value to give the appearance of the price. This model really works. It's been adopted all around to build massive suburban ghettos and has become almost impossible to work around.

    OTOH, working with someone who gives value before cost has had to price themselves out of the marketplace. Where's the middle ground? If the standards changed so the bulk manufacturers had to change their models to meet them it would allow a better mix to the customer. Competition would hopefully keep the pricing sane. Sweden has shown it CAN work, but it has to be unified and pervasive.

    Will it happen. Depends on oil, I think. Another long term shock and there may be some receptive ears on top of the hill. We'll see.

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