I agree the end product is only as good and sustainable as the design, in combination with it's technologies applied correctly. I believe that's what we are all commited to. There will always be different paths and priorities. I was sure that you were going to advocate the tent option and probably do prefer tents over living in a foamed house. Clearly my priority is the easiest path to high R-Value, sacrificing some petro chemical to save more petro chemical. I admit I also use I products like Grace Vicor, etc. in valleys, around openings, etc. to protect from water intrusion (with considerable attention to the drip path). I think these are good technologies (yes, not great - great Would be fool-proof), but they can be misapplied and as you stated - over applied, which could trap moisture, especially in combination, over large, adjacent surfaces. We use insulation baffles within rafter bays, which addresses this 'trapping' conflict, although a membrane breach will most likely go unnoticed. Nothing beats construction moving at a measured pace, with time to observe performance deficiences and make modifcations.
Here's my regional argument. I believe that you live in Vermont. I live on Long Island. Fuel costs are much higher here. You can spec the less expensive, more environmental cellulose with half the R-Value, burn wood, save money and go skiing, while we struggle to pay off our excessively high real estate-valued lives.
Looks like you took the right path based on the correct priorities.
I am interested to know what you think the ideal thermal envelope consists of?
Appreciate your postscripts.
SDR & Associates
131 Cedar Street
East Hampton, NY. 11937
(631) 324-0900 ~ fax
--- On Thu, 3/11/10, Samuel Robins <[log in to unmask]>
You site only extremes. Life has compromises. The perfect is the enemy of the good. You could debate every position and forever be confined to a tent.
The examples I give are legion, hardly extreme. In fact a central element of the CNRC MEWS study, as well as the Florida Solar Energy Center study (two very mainstream groups) was to introduce the inevitable minor leak into wall or roof assemblies. In both cases, foam-insulated or foam-sheathed envelopes got failing grades.
Yes, the perfect is the enemy of the good. Which is exactly why
I draw attention to the absurdity of the "perfect wall" such as Joe Lstiburek and many others advocate. An impermeable foam plastic box performs only as long as the building starts out perfect and remains perfect for its useful life. Neither case is either likely or reasonable to consider.
The most foolish approach to any technology is to try to make it "fool-proof". What is required for durability and the health of its occupants is to design and build a house to be "fail-safe". All human artifacts fail, and most begin their lives with inherent flaws. A resilient structure can tolerate minor failures. A non-resilient structure cannot.
In a house assembly, resilience requires materials and methods which allow a structure to dry when it - inevitably - gets wet, and to buffer (absorb and release) excessive humidity when the mechanical systems meant to control it either are overwhelmed, under-perform
for lack of maintenance, or go down when the power grid crashes.
Building hermetically-sealed boxes and calling them homes fit for human habitation contradicts basic physics, undermines biological integrity and defies common sense.
- Robert Riversong
master housewright, building scientist, philosopher and prophet for our times