Spring is here and construction season is upon us.  The winter season - and darned cold it was - is slowly being moved out of the way for warmer construction weather.  The garage was re-organized this weekend in preparation for structural work in the cabin and then work on the residence.

The winter was spent designing and studying a residence concept for construction on the site.

So here is where we are.  The concept for the residence has become developed to the point where pricing is being executed for the construction.  We have looked at multiple options for the design and structure.  The photo below illustrates the model I built to study massing and siting options and one roof option we looked at for a single level 1600 SF option.  


The first pricing study that was done was for modular construction under the assumption it would be reasonably cost effective and craning in the modules would save a lot of construction time.  A concept was developed that met modular widths, heights and shipping concepts.  It was sent out and the pricing returned was surprisingly high.  The concept was rather small - approximately 1700 SF with a second level space for a studio and possible guest room.

The second study was for a single level straw bale wall construction.  I did not get into detailed pricing, and did create a design for straw bale walls and construction.  I sent the concept to a Colorado straw bale company that has done really good work and came recommended to me.  That concept, too, came back a little higher in cost than I was looking for.  I did get really good information from the company - Solarwise, Salida, CO - and appreciate their candor and input.  

As an interesting side I was doing technical research on straw bale construction and uncovered several articles that indicated thermal testing on straw bale wall indicating the thermal performance of the walls is lower in actual performance.  The anticipated R-value of straw bales was approximately R-45 and the actual tested performance level in several articles was R-21 to R-25.  This particular fact got me wondering about other options - particularly SIPS (Structurally Insulated Panels) construction.

The equivalent R-value for the 10" SIPS wall panels we are looking at is R-37 to R-39.  

As I write this we are pricing a SIPS panel building - walls and roof.  When constructed, and sealed correctly the envelope will be very tight and efficient.  I have sent the envelope package out for pricing and the panel package has come back favorably.  That pricing element has to be added to the other pricing line items, so the entire cost is not yet known.  I am encouraged.  I realize other pricing elements are still required to develop a complete cost picture...never-the-less we move forward.

On a side note I have installed two data loggers on the site: one interior and one exterior.  These devices are inexpensive tools to help accurately measure temperature and humidity climatic data.  The graph images from the loggers for the interior and exterior are noted below:

The upper graph is the exterior climatic log and the lower graph the interior log.  For a currently uninsulated structure the cabin performed reasonably evenly.  The upper (exterior log) indicates the temperature swings we would anticipate from November to December here in Colorado.

I found a the humidity line at the graph to be the most interesting.  The humidity at the graph was a lot higher than I expected.  The swings in humidity at the exterior were interesting also.  The exterior graph shows the humidity at 60% when the temperature was down to 20 degrees and humidity at  +/- 15% at a 60 degree temperature.  Similar performance is illustrated on the indoor graph.

Colorado is known for its dry climate.  I would not be surprised for increased humidity in the evening (thus frost on our car windows in the morning).  The degree of upswing in the humidity was a surprise. Upon further discussions with various folks it turns out that a lower temperature has a tendency to increase humidity which is reinforced by the performance indicated at the exterior graph.  

In addition to the climatic data I am studying heat gain / loss, solar gain, shading options, window performance, ventilation options, efficient heating and natural ventilation strategies toward a final construction solution.

More to come.