How are timber frame houses insulated?

The insulation range depends on the thickness of the SIPs or the accumulated insulation. Often wooden frames are insulated with SIPs (structural insulation panels), which can be fixed to the outside of the frame. A SIP wall would offer seamless insulation wrap, and if you tape the joints properly (see our page on how to make an air barrier properly), it can also be airtight. The foam inside the core of a SIP acts as a vapor barrier.

You can also do this with straw bales, and if the time comes, you can even glue the frame between the posts for easy insulation and wiring. What have you come up with to date as a wall mount? There's no reason why a timber-framed house can't be as well insulated and airtight as a stick-framed house. As these builders pointed out, if a stick-framed house is extremely well built, it can withstand the test of time just as well as a timber-framed house, except perhaps, as Hemberger notes, “in certain natural disasters, where timber-framed houses are more resilient, such as a falling tree about the house, since it is certainly more resistant. Once upon a time, timber frame builders relied on pen and paper to make their designs and calculations, but contemporary professionals now consider computer-aided design (CAD) programs to be indispensable tools for their speed, efficiency, and help with customer communication.

Simply put, wood fiber insulation, such as the Unger-Diffutherm range, is one of the simplest and most effective ways to insulate a wood-framed building. However, it is quite common to find widespread active attack by the Deathwatch beetle on woods immediately behind lime renderings, but it is rare to find it in exposed external woods, suggesting that sometimes the moisture content of a frame rendered with lime may be high enough to withstand the attack of fungi and beetles. When insulating between timbers, you need to be able to cut the insulation easily and quickly so that it fits tightly to the wooden frame and also to the inner surface of the frame, whether it is OSB or a membrane. It is for this reason that this type of insulation is now more commonly found on the top of beams or on the outside of wooden frames.

Having built wooden frames before using SIPS, I was aware of many of the drawbacks that SIPS pose. If the wooden structure and infill are in good enough condition and are robust enough to cope with continuous exposure with limited interventions, insulation can be installed on the inside face, either directly on the wall or with an air gap. Wooden frames get wet, insulation materials get wet, and even prefabricated panels get wet on site, so it's important to use a system that can dry quickly and also helps the wood frame dry out. Let's take a look at creating a high-performance timber-framed house to see how it differs from its ancestors, starting with the design.

Designed by BRIBURN Architects and built by Benjamin %26 Company, this net-zero Freeport home features timber framing details, including this three-season porch and a white cedar pergola (not shown), as well as large Douglas fir wood beams in the main space of the home. First I had to decide whether to use an infill system (where the walls are built between the wooden posts) or an external cover that encloses the entire frame.

Serena Uccello
Serena Uccello

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