Northwest Timber Frames
Enclosure Systems

Once the frame is raised, there are a variety of enclosure systems that can be used to complete the construction of the walls. Our designers at Northwest Timber Frames can be of great assistance in helping you decide which system works best for your particular situation.

The most popular method in the industry are Structural Insulated Panels (SIPs), which can be installed to provide not only the exerior walls but sometimes the roof/ceiling systems too. SIPs are made of Expanded Polystyrene (ESP) sandwiched by two sheets of plywood-like material called oriented strand board (OSB). Invented in 1935 at the Forest Products Laboratory in Wisconsin, SIPs originally were composed of regular plywood and standard framing members and filled with standard insulation. Over a 30 year period the design changed as new materials were brought to the market place, including rigid insulation in the 1960s.

Eventually computer aided production became possible and today's SIPs are mass produced with amazing accuracy and come in wall thicknesses from four to six inches and up to 14 inches for ceilings. They can even be cut in curves for specific applications. SIPs are widely used because of their speed of assembly and their energy efficiency. Once the panels or other wall enclosure systems are complete and in place, the roof and siding can be added to make the house weather tight and the interior work can begin.

It should be noted that SIPs also come with a straw mixture replacing the rigid insulation. The disadvantage of these types of SIPs is they weigh considerably more than rigid insulation panels, which considerably raises the cost of shipping.

Other enclosure options include conventional framing methods using standard batts or blown in cellulose insulation as well as natural insulating materials such as straw bales, clay, wood chips or clay and wood chips combined with straw. The advantage of straw/light clay is that you can increase the insulating factor by simply increasing the width of the wall, according to the demands of your climate.

Wood chips mixed with clay can also create a fire resistant and insulation efficient wall similar to straw and clay. The labor to produce the mixture and to infill the walls, however, is about half that of straw and clay. In wood producing regions, wood chips could become an attractive option. Other infill options include: straw/clay blocks, reed matting, wood chips and cellulose fibers.

Alternative roof systems to consider are thatching, where reeds or other materials are woven into bundles and attached to the roof; and the use of natural slate shingles.

Whichever methods you decide to use in your construction project Northwest Timber Frames will be able to help facilitate it.