Building Systems

There are many ways to build a building, and which way you choose will depend on your climate, availability of materials and personal preferences.  Most houses in the US are build from a single wall wood frame, and most of them are inadequately insulated as well as sometimes having other problems.  Wood frame construction has a large infrastructure of suppliers and labor who knows how to build frame walls, but that doesn't mean its necessarily the best choice for all climates.

Each of these building techniques has its own user groups and cheerleaders, and each group will claim their building technique is better than everyone else's.  Needless to say, they're all wrong, because each has its own unique set of tradeoffs. In considering each of the techniques, you need to not only evaluate their relative merit, but to figure out whether you can find the materials and expertise to build in that style.  If you live in an areas with building codes, you may also find the building department not especially open to alternative construction techniques they are not familiar with.  Although not insurmountable (patience and charm help), it can add a significant burden to the construction process.

The following discussion, a building is broken down into three components: floor, walls and roof because they are each fundamentally different.  There are many more options for walls than there are for floors and roofs, and this is probably due to the fact that floors and roofs must be constructed out of material that is strong in bending, while walls must be strong in compression, and there are many more materials that have strong compressive strength than there are materials that have strong bending strength.1

Note: construction diagrams are examples only, not intended for actual construction.

Envelope

Although we think of foundations, walls and roofs as separate things and in fact build them separately, the work together to form a building system, and so each piece must be matched with the requirements of the other pieces.  These three components form an envelope around the interior, and so each piece must be insulated and control moisture and air infiltration in coordination with the other pieces.  The term envelope generally refers to the layers of insulation, weather barriers, air barriers and vapor barriers that surround the interior.

Foundation Systems

There are only three common foundation systems: slab on grade, crawl space, and full basement.  There are two other possibilities, but of which are not very common: a house on posts, and an adobe floor.  The common foundations are all on concrete, while post houses use little to no concrete.  The common varieties can also be done without concrete in some places, but convincing an inspector to let you can be difficult.

Wall Systems

Since walls are where most of the variation in envelope design is, this document will continue the grand tradition of spending an inordinate amount of space on walls.  To a large degree the emphasis here is because walls have traditionally had less insulation in them than roofs, but also because there are just more ways to handle a compressive load, which is what walls do.

Traditional 2x4 framing uses more wood than structurally necessary, resulting in both increased framing costs and a lower insulating value.  Advanced framing, which has been around at least since 1980 addresses these issues, but still does not make a truly superinsulated house.  In the meantime, many alternative building systems have emerged, most geared at much higher levels of insulation, each with its own set of advantages and disadvantages.

The following discussions compare some of the common (and some not so common) wall systems, both in environmental terms, level of insulation, condensation potential and construction ease.  Most of these methods are only suitable for new construction.  If you're remodeling, start with the remodeling guide, and ignore all wall methods except Rigid skin, Larsen truss, and SIP.

Roof Systems

As with foundations, there are only three kinds of roofing systems, and of these the majority of roofs built in the last 30 years are all truss roofs.  There is also a fourth kind of roof system, which is the arch and with arches you can build a roof out of heavy material with little to no bending strength because the shape of the arch transmits any bending load into a compressive load. You also need to decide the roof pitch (ie how steep it is),  and what roofing material you will use (see roof design for more info).

Resources

Building with Vision: optimizing and finding alternative to wood, Watershed Media (2001).

Buildings of Earth and Straw,  Bruce King; covers all the structural issues of these alternative buildings.

Wikipedia article on strawbale at: http://en.wikibooks.org/wiki/Straw_Bale_Construction 

SIP manufactures association at www.sips.org

Insulating Concrete forms association at www.forms.org

Wikipedia article on rammed earth http://en.wikipedia.org/wiki/Rammed_earth 


Note

1:  The one caveat to this is using arches to build stone roofs, but there are so many difficulties in doing this, that the method has been largely abandoned.  The same arch concept can be used with cob, papercrete or any other material with reasonable compressive strength that can be formed into blocks.