Building Envelope

Our Building Envelope

We went through many scenarios before deciding to try something that, to our knowledge, has not been done in British Columbia before - to put insulation over existing stucco siding - effectively embedding everything already on the house. This past fall, 475 Building Supply featured the Beaumont house in their newsletter. We got excited about adapting it on our house. Once we settled on this approach, the architects redrew section drawings. The discussion about and revision of the building envelope happened mainly in November 2019 - with back and forth among the architects, the contractor, the energy modeler and the clients - and with help from the 475 supplier and the roofer. Then in March & April we had additional discussions about how to be sure the system would perform. Below is the agreed upon build-up. No question it could mean sending lots less material to the dump. But we would learn there would be lots of additional labor to get the wall ready to receive insulation and new cladding. So, (with a heavy sigh), we are not in a position to recommend this route as a money or time saver. We will analyze more when the project is drawing to a close. This is an area where we expect to be way over budget. The system features five inch nails. That said we are really glad we tried this method and think others can learn from it to drive down the price and simplify the installation. The house is meditatively quiet. We credit Rockwool insulation with helping to make the house not only well insulated but soundproof.

Sidewall

1/2” GWB

6mil poly

3” Rockwool Batt

3/4” shiplap (existing)

cedar shingles (existing)

stucco (existing)

Vapour permeable air barrier

3" ACS Clip (includes 1/2" airspace) with 3" Roxol Comfortboard 

3/4” horizontal strapping (shingle zones) 

Cedar ship lap siding/Cedar shingle

Roof (General)

Salvaged asphalt  (vs metal roof - as solar panels are going on top, so why change when the roof is only 3 years old? Roofer felt that he could recycle a good chunk of the existing shingles. We’ll check back when he is on site.)

Roof Underlayment

Existing sheathing 

2x12” sistered joists w./ batt Rockwool

Ridge line cut w./ ridge vent 

Roof (Dormer Areas )

2x6” exposed douglas.fir joists

3/4” T&G fir

1/2” Sheathing 

peel and stick air/ vapour barrier

5” polyiso w./ roofing screws

roofing underlayment 

metal roof

Eave condition.  

6mil poly roof above and wall below wet set into sprayfoam insulation.  

Warm side attic batt as desired for attic portion of roof calculations

The Importance of Someone Signing Off

Here is the issue: 475, Bernhardt and the contractor refined the building envelope system - but that meant it was not the one that the architects designed or had had been signed off on by the engineers. We keep asking “Who is the responsible party?” We are concerned about getting the dew point in the right place. Friends had a house that turned into a moldy disaster as a result of a miscalculation made in this department. We want assurance that since the wall is so darn thick, anything put on the outside will stay put securely in the event of seismic event. This is after all a brand new approach.

There is going to be an extra big blog post how this all worked out and what it cost in much greater detail once we have the final costs for labor and materials. Thus far the place is covered in Mento waiting for the other products to arrive for assembly. Mento is on the sidewalls. It is guaranteed as a barrier for four months - we don’t want to test the limit. Mento is the black material in the top photo. The dormers are done and the roofs await the roofer.

Two consultants were in the mix - RJC to assure the structural integrity of the ACS clips and RJC and/or Hamid Heiderali to examine the issue of porosity and dew point. The consulting that was offered for the latter was very costly and would not provide “sign-off”. Instead we are embedding a moisture sensor in the north bay wall - which is our “worst case basis” ie where the sun will never shine and the stucco has the least ability to dry out. Here is an example of what we are considering - a device from Hoskin Scientific that costs about $250.

See drawing below for the RJC recommended clip system. It represents a modification of the original plan. Once all the numbers are in we can address the increase in cost it entailed.

The actual materials and the built system for walls and roof

Here are sketches of what Elodie Forest and Bryan Paxton engineers at RJC recommended. For more on the Beaumont house that inspired us: https://foursevenfive.ca/blog/a-woodframe-retrofit-wrapped-in-wood-insulation/

Beaumont is director of the climate change film Paris to Pittsburgh.

What is a building envelope?

How many engineers does it take to build a net zero reno?

When you’re dealing with all the building components that separate the indoors from the outdoors, it takes as many as it takes. Building envelopes include the exterior walls, foundations, roof, windows and doors and its performance is impacted by a number of sub‐systems: heating, cooling and ventilating equipment, plumbing and electrical systems.

When the building envelope is resilient, the long-term durability and thermal performance of the building enclosure is assured. As the team at 475 and ZeroEnergy Design describe in their case study of a net positive building, keeping the building structure warm, dry and protected gives you the following benefits:

1. Thermal comfort for occupants - whether a winter storm power outages or the loss of air conditioning in a heat wave, the thermal comfort can remain for days.

2. Control over indoor air quality - supporting the health of a home’s occupants.

3. Protection from rising energy costs - offering long-term cost savings for building owners.

4. Reduction or elimination of carbon emissions - helping to slow climate change.

Read the full blog post on 475’s blog.

And while thinking about cedar shingles and shake head over to The Cedar Shake and Shingle Bureau www.cedarbureau.org for all kinds of good information about how to use these products in the best way to protect your roof and walls.

Our Pinstriped House

Check out the adjustable clips and the vertical metal bars. To get us an air tight house, our contractor worked with Don White (an expert in such things) to apply his patent pending ACS Composite Systems Thermal Break Wall “A-Clip”. The A-Clip is adjustable meaning installers aka our carpenters can adjust the depth of the clip to accommodate elevation differences in walls or soffits. This solution seems tailor made for our build - with its perfectly imperfect stucco surface. The vertical bars are attached to the clips, then the Rockwool comfort board insulation goes between them - then ultimately the shingles go on top of all this. Voila! the material that would have gone to the dump is embedded on the house, the strength of the screws that attach the clips to the wall makes the whole system very durable in the event of an earthquake, and once clad with shingle the house will once again look like it belongs on a street where most of the houses were built in 1912.

I am realizing I have given short shrift to the insulation we chose - Rockwool - made from basalt and slag it has the highest melting point of any exterior insulation - an important attribute in this fire prone zone. The folks who built a house named Finehome Build House of the Year for 2018 shot a short video sponsored by Rockwool that explains the merits of the product admirable.

A personal note: As of this writing (June 20th) we are about to start putting the insulation on our dear Canadian house. I’m in Victoria to oversee this delicate operation. But, Don is in Chicago at our place in Lakeview, spending time with his mom. We aren’t sure when we can next see one another as the border is closed. We are by no means unique in this predicament.

Update as of September 6 (58 days til the November 3 election). The house passed the blower door test with flying colors. Shingling is nearly complete and looks beautiful. The board & batten cladding on the kitchen will start to go up this week. For photos of the house look at the series under construction. Meanwhile on the interior the sheet rocking is mainly done - mudding to start this week. Yoo hoo. To date, some 17,000 Americans have been turned away at the world’s longest border since March which means that for the time being the family cannot come and visit.