Details on the Haven TimberHome building system

The Haven TimberHomes building system has been likened to “adult lego”.  This refers to the simplicity of the design, the ability to interchange timber pieces of the same type, and the speed and ease of assembly.  Haven TimberHomes are an innovative  variant on traditional timberframe structures with “piece-en-piece” timber or log infill between posts.   What distinguishes the HTH system is our use of “panels” -   these are solid timber wall sections between equally spaced vertical posts.  The posts are held in place by interlocking beams on top and bottom.   A wall and an entire structure is comprised of a string of identical panels, each made up of interchangeable pieces.  The Haven TimberHome system conforms to the National Building Code of Canada (Section 9), and the ICC400 Standards on the Design and Construction of Log Structures,  used by building codes across the USA.  The Haven TimberHome system is so innovative that there are patents pending in both Canada and the United States.  A detailed Assembly Manual accompanies every order of a Haven TimberHome.

The repeating panels and interlocking tie beams and sill beams are clearly seen in this photo of the gable end of  a structure.

 

(Left)  A Haven TimberFrame wall can be supported by a variety of foundations – you should always seek the advice of a geotechnical engineer and use a  foundation design approved by local building codes.  The first component of the HTH system is the 8″ x 10″ foundation timber, which is bolted directly to the foundation or foundation pilings, or pony wall that itself is attached to the foundation (photo, left).  The joists for the first floor are hung from these timbers, usually with intermediate support.

When the subfloor is on, sill beams are distributed around the perimeter, access holes for electrical circuits are bored and wires run through, and the sill beams are bolted through to the foundation timbers.  The posts are set in place on dowels inserted into pre-drilled holes, and the wall timbers are filled in.  (photo, below)                                

Plywood splines set into mortise grooves secure the wall timbers to the posts.  Each timber is also glued  and bolted to the one below, but the entire panel of wall timbers can settle vertically, as they are not fixed  to the posts.  (Below.)

When the walls are up, 4×8 tie plates and interlocking tie beams are set over dowels in the top of each post, and the wall is structurally braced in all directions.  (Below)

 

The shell is now ready for roof trusses, or a second story can be built at this stage after floor beams are hung.  Finishing is typically a high-quality clear finish on the interior, and a honey-colored exterior log stain. All joints are caulked and sealed with Sashco “Conceal”, a flexible, textured caulking compound.  The “bluestain” coloring the timbers in these photos are characteristic of Ponderosa Pine salvaged from the devastating kill in central BC of the last several years.  We also build with Lodgepole Pine, a much lighter-colored timber.  Finished exterior, below.

 

A Word About Insulation and Solid Timber Buildings

There is much confusion about this because of the almost universal use of “R value” as a measure of how well a structure will retain heat.  At some point, somebody calculated that 1″ of a typical softwood had an R-value of about 1.4 or so.  If this was the case, an 8″ timber building would have an R-value of 11.2.  An 8″  fiberglass-insulated stud wall would have an R-value of about 29, so you would expect the log house to be a very cold structure indeed.

But this is not the experience of generations of people in North America and Scandinavia who grew up in timber buildings and stayed warm and comfortable.   Dave Loeks, the co-founder of Haven TimberHomes, raised three children in a prototype of the HTH design where Yukon winters could dip to -45 to -50 degrees for weeks at a time.  Everyone agrees that the house was warm and snug all winter, and the heating bills were not high.  Not what you would expect from its purported R-value.

What is going on?   Theoretically calculated R-value ratings are not lining up with actual experience.  What is missing is an appreciation of “thermal mass” – the capacity of some mediums to store and re-radiate heat.  A well-built log or timber home performs much as a soapstone or masonry woodstove does – it stores heat and re-radiates it.  Its not that R-value is invalid – its that it is not the full story.  R-value measures resistance to heat loss through transfer, while thermal mass measures  capacity to store heat.  Both are important to understanding what we are really interested in: Energy Performance, measured in how much energy a house consumes to keep a constant temperature.  There is a third that influenced how warm a building is: air flow, or draftiness.  The tighter a building the better.  Here is the equation to measure engergy performance:

EP = r + tm – ae         {Energy Performance = Resistance (R-value) + Thermal Mass – Air Exchange}.

In a conventional building, thermal mass is negligible, so builders have only R-value to consider.  Because of this, R-value became the sole  stand-in for estimating energy performance until the modern re-discovery of log and timber buildings compelled engineers to re-consider thermal mass.   Whether liters of oil, cords of wood, or kilowatts,  energy use over a winter  = dollars and this can be measured.

In fact, when demonstration projects have measured and compared energy use of conventionally insulated buildings against solid timber buildings, they have come out much the same – over the course of a year, an 8″ stud wall building uses much the same amount of energy as a wood building of the same thickness.  Timber and log buildings can be built amazingly tight so air exchange in a sound building is low.  A wooden boat doesn’t have to leak; neither does a wooden house.

People who have lived in both timber houses and conventional “stick frame”  houses agree that a quality timber home feels much more comfortable.

(See: Energy Performance of Log Homes.)