Design Charrette!

I hosted our design and build team at RDH for a design charrette in early December. I waited to hold this meeting until after we’d talked with enough neighbhours that we felt comfortable moving forward, and after we felt confident that we would be able to finance the project. We’d waste a lot of work and money on the detailed design if we didn’t have sufficient support on both fronts.

The goal of this meeting was to discuss big design choices in the context of cost, constructability, zoning, and performance, and then turn the design team loose to bring it to a point that we can present to the Community Association, and ultimately assemble our rezoning application package.

Around the table were Mark A (Architect), Mark B (Builder), Ian Scott (Planning Guru), Rob Lepage (RDH Building Science expert), and Kate Stefiuk (Landscape Designer). I felt awed and grateful that this talented and knowledgeable group of individuals was here to help make our project happen.

We hashed out most of the big design questions in three hours at the office. Mark A, Kate and I then fortified ourselves against the December rain with sushi and miso soup and wandered our property for another hour to discuss the landscape design in context. A productive day!

Here are the key items we discussed and agreed on (see the project page for the basic scope):

• Building Shape
• Suite vs. No Suite
• Building Entries
• Enclosure Design and Materials
• Systems
• Parking
• Landscape and Storm Water Design
• Accessory Buildings
• Energy Modeling
• Existing House Elements to Retain
• Schedule
  

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Building Shape:

The ideal passive house has 4 corners. Why? Well, you are investing more material into the envelope than a typical building to super insulate it. Every time you turn a corner, you have to transition all that material.  The cost of detailing is much higher than a straight wall, and the likelihood that the detailing will end up being less than perfect is high. This leads to increased thermal bridging and increased heat loss. So to build a high performing envelope in a cost effective manner, the less corners the better. The challenge then lies with the architect to dress up a box!

Fortunately we’re already starting with simple shapes. The existing house is a rectangle and we will maintain the existing footprint. The new house is very close to a rectangle, currently showing one wall bump to work around some setback challenges:

and a tricky cut-out detail at the entry, which will add cost and compromise performance due to complicated detailing:

The wall bump is ok because it is simply an extra corner. Mark B suggested redesigning the front entry, though.

Suite vs. No Suite:

The City planner I met with back in October believed that the suite was the thorniest element of our proposal, since it is not supported by existing small lot zoning. However, our neighbours were either neutral or in support of adding the suite. Our design team felt that we could make a late change it would make or break our project, so we’re sticking with the suite for now.

Building Entries:

Ian suggested we consider making the existing house main entry more like a traditional front porch. This suggestion was based on his experience with city design guidelines and the typical feedback these projects receive. I am deferring to Mark A on this one, as I believe that a design can be modern, welcoming from the street, and fit with the neighbhourhood fabric without having to mimic historic styles.

Downstairs bike entry: We need an easy entry into the downstairs for bike storage. This we know from years of hauling bikes in and out every day; up and down skinny stairwells, around tight corners and various other less-than-ideal arrangements. The easier it is, the more likely we will continue riding every day forever. We may also have some limited bike storage space in Matt’s detached workshop, but a storage space in the main house for at least the most used bikes is really the best arrangement for comfort and ease of access.

Enclosure Design & Materials:

1. Foundations: We are assuming that we will rebuild the foundation of the existing house after it is lifted and we are thinking of using a similar approach for both houses – a slab on grade with traditional footings and insulation stuck between, like this (squiggly lines are insulation):This approach will save cost compared to doing something like this, where we’d have to insulate under the footings:
2. Blasting? Yes, hitting bedrock is a real possibility in our location. It actually makes me wonder if that is the reason the existing house is tucked off to the north side of the property. We will do some exploratory digging later on to get a better idea. Mark B suggested including a budget of $5,000-$10,000 just in case.
3. Exterior Walls: We will take the existing house walls down to studs and apply a similar approach to both new and existing: taped plywood sheathing + weather resistive barrier like SIGA Majvest (which Mark B says is cost competitive and easier to work with than Tyvek) or other weather resistive barrier + rockwool + strapping + cladding, similar to this:
   

   Source: Guide for Designing Energy Efficient Building Enclosures

4. Roof: Mark B advised sticking with interior attic insulation given the cost of exterior insulating the roof, even though I like the conceptual simplicity of exterior insulation. The detailing for transitioning the air barrier and insulation from the exterior to interior is straightforward. We need to poke our heads into the attic space of our existing house to better understand our existing condition.
5. Windows: We are assuming triple pane. The material is to be determined, but we will aim to carry budget for high performing wood windows and we can always downgrade from there. Our preference would be for wood or fiberglass windows. We’d like to avoid products containing PVC, and I’ve heard mixed results about the long-term performance of reinforced vinyl products. If we do go for Passive House certification, our window options are more limited, since we have to select certified products. Mark B said that Optiwin windows from Germany have proven to be the most reliable and cost competitive certified products despite shipping from Europe. He suggested a budget of $60-70/sq.ft. for windows.

Systems:

We will install all-electric systems for both houses, using a high-efficiency heat recovery ventilator (HRV) for ventilation + solar PV + some form of electric supplementary heat, to be determined based on our modeled heating loads. I am also curious about the new Tesla house battery, although BC Hydro’s net-metering rate (the price at which they will buy energy from us) for site generated electricity is actually very good ($0.0999/kWh)*, and may make energy storage unnecessary at least in the near term.

*Our current Step 1 rate (for consumption up to 1376 kWh) is $0.0797/kWh and the Step 2 rate is $0.1195/kWh. If we can stay under the Step 1 threshold (entirely feasible in a low energy house), we can actually net a profit if we generate more than we consume.

Lighting will be all LED, both houses. Other systems, like domestic hot water and possibly grey water re-use are to be determined.

Parking:

Parking is always a hot topic that gets way more attention than it deserves. If we didn’t have so many cars, we wouldn’t have so much trouble finding places to put them and it just wouldn’t be such a big deal.

Alas, we’re not there yet – we are here. “Here” is a zoning requirement to provide one off-street parking spot per single family dwelling. The rental suite does not require an additional off-street spot, thankfully.

We started out with parking in the front because the lot width is tight. Then we moved it to the back with a shared driveway because I figured people walking by our house would not want to see cars parked in front.

Turns out that our neighbourhood has an entirely different approach to parking. The R1-G zoning that governs typical single family home developments has evolved to allow parking in the front; the idea being that having a couple of well-placed permeable parking strips in the front of the house means that parking is provided off the street while consuming the least amount of green space. Providing parking in the rear means a long driveway, turnaround space, and cars idling in the back yard.

Here’s a snapshot from the parking guidelines, along with a few photos of front yard parking in the neighbourhood:

 

Our neighbor several doors down on Clare St enlightened me of this approach and it makes a lot of sense. The back yards that share a fence between Clare and Chamberlain Streets are all green space. There is not a single car parked behind a house. The effect is of a large park space as far as birds are concerned. Many of the yards even have gates between them, encouraging outdoor exploration and connection for humans too.

So we’re back to the front yard. The compromise is that we will be proposing two driveways in order to break up the parking for the two houses, whereas with the shared drive aisle to the back yard, we had only one driveway. But I think on balance this is a better approach.

Landscape + Storm Water Design:

Mark A, Kate, Matt and I discussed the landscape design onsite after our charrette. Being onsite allowed us consider the design within the context of neighbouring properties and sight lines.

This is what we want the landscape design to do:

• Encourage/facilitate connection with outdoors
• Enhance privacy between connecting properties at the rear of the houses, particularly with respect to window sight lines
• Include playful natural features for kids (small hills etc)
• Include rain gardens to slow storm water flow
• Create a back yard oasis
• Include a tree retention + tree management plan – this is required for the rezoning package. We will also ask the arborist to advise on the large gary oak tree next door, whose branches and drip line overlap the proposed new house.
• Use permeable driving strip/parking pads

Accessory buildings:

Matt’s workshop behind the existing house will be~12×18, with single phase power and decent insulation, but less than the main house.

For the new house, we will plan for an accessory building for additional storage given compact floor plan. It does not need power, but could provide electrical conduit for future. Insulation will be the same as Matt’s workshop.

Energy modeling:

I will do the energy model for the existing house; Mark A will do the new house. If we do seek Passive House certification, we can each obtain our “Certified Passive House Designer” designation having been the prime modeler and Passive House designer for one of the houses.

Existing house elements to retain to the extent possible:

• Hardwood floors
• Most exterior and interior framing
• Solid wood doors
• (Wonderfully long) clawfoot tub (add separate shower)
• Farmhouse sink (kitchen)
• Several interior walls (remove lathe + plaster)

Schedule:

We’re aiming to get the rezoning application submitted in February 2016, which is tight given that we have to present to the community association and collect signatures before that. If we can get it in by February, though, it is conceivable that we will have a building permit by the summer. Mark B advised that if he can start construction by early August at the latest, he can get the roof up before the rainy season (which for us is October-December). If we don’t get the permits by then, he advised waiting to start until the following January or February when the clouds lift again.

Sequencing of new and existing house construction: Ideally, we can complete both projects concurrently. It will be more efficient to pour the foundations at the same time, for example, since the main cost is getting the equipment on site. However, the sequencing will also depend on how our financing comes together and whether we need to move the existing house to register the new subdivision. If it costs us more to finance the project doing it all at once than we save through construction efficiencies, it will make more sense to do the new build first and then finance the renovation from the sale of the new house.