A Passive House for Vancouver Island #Passivehouse #Comox
Seeing the forest for the trees – Passive House in a remote setting on Vancouver Island #PassiveHouse #Comox
by Ayme Sharma
One of the most important first steps in designing a passive house (or any building for that matter) is the orientation of the building massing. Southern solar exposure is key. But how do you design for sun when the proposed site is surrounded by mature trees? Site has played a major factor in the design of this single-family residence set in a remote location on the east coast of Vancouver Island.
As artists themselves, the owners have a fine appreciation for design. They first approached us referencing a completed passive house in Bessancourt, France that inspired them. It has a very clean and contemporary aesthetic. At their request, the schematic design began with a similar massing: simple, farmhouse geometry, steep-pitched roof and open carport. The site has largely guided us in the refinement of the design from this starting point. For example, the building massing would never actually be seen in its entirety since the site is hidden from the road by dense trees and the driveway is not very long. The owners were concerned that since only the north façade would be viewed from the street, the house would appear quite stark if the design focus was on creating a uniform and minimalist object. For this reason we worked on refining the north elevation to add a sense of scale to the entry and the view from the driveway. We played with contrasting colours, material patterns and textures to define the entry as a picture that was framed to draw the eye of the viewer.
The 2-storey, 2-bedroom house has a modest footprint of 1030-sqft with some carefully considered space-saving features. The lower floor has an open-plan kitchen, dining, lounge and living space with generous south-facing windows and doors that open out to the backyard. Interior walls are shortened to share the daylighting. The upper level has the bedrooms as well as a central studio space with an 18-foot high vaulted ceiling.
Getting the southern shading right was a challenge. We used a combination of a shadow study and the Passive House Planning software (PHPP). The 0.4-acre site has over 50 trees, evergreen and deciduous ranging from 6m to 50m in height. The owners are interested in keeping as many trees as possible. The new house will even maintain a similar footprint and location to the existing house on the site so as to disturb the site as little as possible. Although the house is oriented so that the southern elevation faces a generous backyard, the heavily-treed site required further shadow studies. The owner carefully surveyed all of the site trees. We used this data to create a digital model of the site and the schematic massing. The shadow study revealed that by shifting the house as far to the east as possible and by tilting it by 3 degrees to the southeast, the south elevation could take advantage of a clearing in the trees for more solar gain.
When we entered the house details into the PHPP we realized that the roof eaves on the south side and the proposed upper-floor balcony were both casting too much shadow for too long on the southern glazing and limiting the potential solar heat gain from the windows. This was affecting the houses ability to meet the Passive House standard. We reduced the length of the eaves and converted the continuous balcony to a series of juliets. Although the PHPP tool is invaluable in testing shading at the level of design detail, it is quite primitive with regards to shading as a result of site obstructions such as trees.
The owner’s neighbour will mill cedar for the siding of this house. The neighbour suggested that it would be less wasteful to cut the boards in unequal widths, which we were only too happy to incorporate into the façade. This is a beautifully simple example of how the process of making can guide an aesthetic. And it is not only the cedar siding that is to be sourced locally. The owners’ will be taking on the role of general contractor during construction and have gone to incredible detail in sourcing local materials and suppliers for their new home. The existing house will be demolished and certain materials will be salvaged for reuse.
The owners have done a lot of work to balance the essential components of their future home with their budget and their commitment to attaining the Passive House standard. We hope that their hard work at the front-end will result in a predictable construction process and a house that they can be proud of.
- Total Sqf: ~ 1,620-sqft
- Design heat load: 13 Kwh/m2/year
- Design annual heating/cooling demand: 2,100 kWh/a
- Design Air tightness: less than 0.6 ACH
- High Performance Heat Recovery Ventilation: 93% efficiency
- Triple Pane Wood Windows: U-value 0.8; SHGC 52%
- Prefabricated Panelized Building Shell: R-value 39 (Walls), R 50 (Roof)
The project will also incorporate the following:
- Rainwater collection
- Low flow fixtures throughout
- Drain water heat recovery
- Native landscaping and permeable paving where necessary
- Lumber from FSC certified sources
- Flooring and millwork from sustainable sources
- Regionally sourced materials where possible and appropriate
- Use of recycled materials where possible
- No VOC to be used
Marken Projects have nearly completed the Building Permit Drawing Set for this Passive House. Construction will begin this spring. Watch this space for more updates. Contact us for more info: firstname.lastname@example.org | http://www.markenprojects.com