In 2008, I was learning very basic aspects of energy efficient design - concepts like solar gain, thermal mass, insulation and air-sealing were all new to me. Library books were where I started but I came to realize that much of the information that was available was from the 70s and 80s! It wasn't until I picked up a copy of Volume 1 of Fine Home Building's "Energy-Smart Homes" magazine that I realized that there were people out there working on building houses like the one I wanted to build. Soon I was on the internet digging and digging for information, when suddenly I came across a website called "Green Building Advisor", also a branch of FHB.
I learned a lot after stumbling onto the GBA. Their "Q&A" forum offered fast, and high quality information from different experienced perspectives. It was a goldmine of information that allowed me to develop my own perspective. I lost all interest in using rigid foam insulation as an above grade sheathing material and gained a strong interest in air-tightness. It was right about this time that I also started drafting my first profile sketches - which were a more primitive version of what I am currently building.
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| Version 1. More of a double wall with "air-tight" sheathing that isn't very "buildable". At this point I didn't really have a good system for sealing the joints of the sheathing. I hadn't yet heard of some of the nice tapes that I later came across. |
The work of Master Housewright Robert Riversong has been a key influence on my thinking. The truss wall design that I have finally settled on is only a re-working of his original "Riversong Truss" that incorporates "air-tight" sheathing and exterior dimensions suited to using batt insulation (instead of dense packed cellulose).
In the spring of 2010, my wife Jessica and I decided to consult with an architect about our project. There were a couple of reasons for doing so:
- We both wanted something more thoughtful than a "canned" floorplan and I wasn't having much luck coming up with my own.
- I needed an engineer's stamp to satisfy our local building inspector that some of the more unusual things I wanted to do could be done - like framing a truss wall or putting our footings on top of rigid foam.
For a while I had gone away from the idea of using "air-tight" sheathing as an air barrier but it came back around again to gnaw at me in the end. Before I returned to seek amendments to my plans I decided to have a chat with my local building inspector. I was surprised to find that she was in fact quite progressive in her thinking. For example, what I thought would be a long debate about eliminating the "vapour barrier" as drawn on my plans in favour of taped 1/2" plywood as both air barrier and vapour retarder turned out to be a non-event so I didn't bother amending my plans - I just drew up some of my own details.
One of the last things I had done before we built was have some "energy modelling" done. For this I turned again to Robert Riversong who may not use the "most advanced" software but who's math skills I trust... more than many simulation programs I've fooled around with. I would have liked to have tried using the PHPP software to tweak the design as we went but there was nobody locally who was using it and the purchase price/learning curve were a little beyond the budget/timeline. In any case, I was satisfied with the numbers Robert's calculations returned so it was finally time to pull the trigger.
Lucas,
ReplyDeleteDid you have any issues with requiring a `fire stop` in your walls. Just curious how inspectors feel about the doublestud/truss walls.
Also, was it difficult to work the hanging truss/FSPF with your structural engineer.. Or was that an easy sell?
Jobe,
ReplyDeleteTo be honest, the question of "firestops" never came up with my inspector. I will be insulating the walls with Roxul batts, which are possibly the most fire-resistant type of insulation there is, so I'm not too worried about it.
Regarding the truss walls and FPSF foundation...
In the begining I was a bit worried about how I would get approval to do all these things I wanted to do. This was one of the reasons my wife and I decided to consult with an architect.
Both items we're an "easy sell" - Walter had already done a number of projects using FPSF foundations and with the drawings I made it was easy to describe how I wanted to build the envelope. Once Walter knew what I was after he had his "in house" engineer stamp the plans.
There was a point before all that when I had gone to speak with a couple of differnt structural engineers but they didn't seem all that interested... I think they had enough "easy work" that they didn't need to take on what they might have considered a more "risky" project. Frankly, now that I have a rapport with my inspector and know the building code better, I'm sure I could have gotten a permit myself without any stamps. Live and learn.