a humble wood bunkie

2022.013 Algonquin Highlands Office-Bunkie

  • October 1, 2022
  • andyro

After selling my zero-emission steel quonset home in Quebec last year, I had been thinking of getting a live/work space in Barrie. But the lateral move from a lower-priced market into the red hot GTA/Simcoe-Muskoka market would have had me borrow a lot more money than I could comfortably carry. After making offers on a few prospects, the deals fell through (fortunately) because I realized I’d be in well over my head. Then I happened on a charming lakefront listing in Algonquin Highlands. It was half the price of any other waterfront in the region (why has it not sold yet?!!), and it came with two seriously run-down but cute cabins (maybe that’s why? – oh, and there were some unresolved title issues). The log cabin, over 100yrs old, is completely uninsulated and its stone crawlspace is clearly home to ants, voles, chipmunks, squirrels and even a groundhog, which we discovered makes an adorable chirping sound if threatened by our presence.

The problem is, I was looking for a live/work space possibly with a rental component, and this place, although it is close to many fond childhood memories; the town of Dorset with its fire tower, Buttermilk Falls, where we used to have family picnics, and endless cliffs and lakes and trails, this place was just a tiny plot with two shacks completely ill-equipped to work from during the Winter. Offer made and accepted – oh no!! Now what?! As an architect/builder, zero-emission renovations are a hobby of mine and every building problem has a renovation solution right? So – let’s start with the stick-framed building, and make it a demonstrator for the renovation of any part 9 residential construction, using all of our latest detailing – as below.

This wall section at a roof shows our basic approach. 2×4 walls that are sheathed in OSB or plywood get the direct application of a self-adhered SIGA Majvest WRB/Control layer which is also an air-barrier, all seams sealed with Wigluv Tape. 6″ of exterior, porous, mineral fibre (Rockwool Comfortboard 110) is applied outboard of the sheathing and pinned back to structure with 2x battens, which a final layer of metal cladding (yes we expect more wildfires!) is screwed into. Airtight and bug-proof, dries in 2 directions, and passes WUFI analysis for avoiding interstitial condensation.

So I set to work to insulate the floors, walls, roof, etc. Then I discovered just what the former owner considered was an acceptable floor structure: Every floor joist was spaced 4′ apart with a network of 2×4’s forming the tributary load system – so every floor joist was taking about 4x the load the code allows, while making it impossible to insulate as there were no proper voids to install a batt of insulation into. To be honest it was unsurprisingly trampoline-like. So, tearing out the interiors and rebuilding the floor was the first order of business. While starting that, it became apparent that the exterior walls and roof system were supported by little more than the shear strength of a handful of nails, where the sill plate of the walls was resting only on 1″ of the too-few joists and a single 2×8 ledger or rim joist. Then the beams supporting all of that were only 2-ply 2×10’s, where at minimum a 4-ply is code. Good grief – seriously people? Who the f&*k built this thing? Who gave it a permit?! So I ordered a pile of beefy rough sawn beams direct from a local sawmill, designed to slip under the walls and reinforce the built-up beams with the help of 2 little 4-ton bottle jacks.

So now that the floor system has been rebuilt, next up is installing new triple-glazed windows (from EPAL). Next we reinforced the roof by providing Simpson hurricane ties (because, Hurricanes!) at every rafter, fastened from the exterior into the double top plate of the wall with 10 structural screws per tie. Then we added 6x 2×4 collar ties to the rafters all bolted with 1/2″ carriage bolts that until now had no lateral restraints – in other words, we added a bottom chord to the triangle so the walls will not splay outwards due to snow loads.

Justin Hamway then delivered the material for our SIGA AVB and WRB ‘smart’ membranes, which permit bi-directional drying of any water vapour that finds its way into our assemblies, while blocking vapour transmission in cold weather – I’ll explain how these get installed in a subsequent post in the roof, walls, floor and at all window and door openings – but here’s a PDF of the builder manuals we intend to follow religiously:

Majrex (interiors)

Majvest (Exterior WRB)

Sam, our canine construction foreman with Justin from SIGA, holding Majvest for the exterior, with Majrex interior AVB (the white roll with red printing) in the centre. All this gets sealed up with Rissan tapes on the interior and vapour-open Wigluv tapes on the exterior.

As we’re interested to see what our projected heatloss on this bunkie is, we can run analysis using our new Sustainability Facts tool with the new TEDI calculator – let’s see how it does (all walls/floors/roof face air temperature so the TEDI should be pretty accurate).

So based on the areas and RSIeff values proposed for the surfaces, and the occupancy of 1-2 people, measured against our regional heating degree days, we have a peak heating load of ~1kW. That means the tiny woodstoves I have been looking at (under 5kW) will be total overkill. Hmmm. What to do? I guess we will build it and see how easily a standard 15-amp plug in el-cheapo heater does in the space!


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