HERITAGE HOUSE CONVERSION to modern office

An EnerPHit first in Nova Scotia

By Lorrie Rand, Habit Studio

Nova Scotia’s first Passive House retrofit in Halifax, designed by Habit Studio and under construction by Root Developments, is near completion. The project involves converting a two-storey 1850s home into office space for the Habit Studio’s eightwoman architecture firm led by owners Judyann Obersi and Lorrie Rand.

Habit Studio specializes in Passive House design and sustainable whole home renovations, projects that deliver healthy and highly energy efficient buildings. Motivations for the project came from a desire for the team to be as comfortable at work as their clients are in their homes and to demonstrate a Passive House retrofit. While Habit has completed several deep retrofits that achieve nearly net-zero performance, none of their previous renovations has met the Enerphit targets.

When Habit Studio purchased the house, it was in nearoriginal condition. It was uninsulated with antique wiring and had a wood burning fireplace in nearly every room. The structure is very representative of old Nova Scotia homes with a timber frame structure supported on a fieldstone foundation. The windows were single glazed with wood frames, including some with original sashes and frames. The initial blower door test result was 24 ACH50. Electrical bills from the previous owner were not available but the modelled primary energy for the building, which includes all electric loads, is 924kWh/m2/ yr with 641kWh/m2/yr strictly for space heating.

The EnerPHit standard has relaxed performance targets compared with a new-build Passive House project because of the limitations of working with an existing building’s geometry.

Designers can choose between two modelling approaches: the energy demand method and the component method.

The energy demand method works like a classic Passive House project, with heating demand and primary energy targets. These targets vary based on climate zone and for Halifax the space heating demand is 25 kWh/m2a. The component method outlines requirements for individual building components and does not limit energy demand. Both options have an airtightness target of 1.0 ACH50.

While the form of the building is simple, site conditions added complexity to the retrofit. A fundamental requirement of the Passive House building enclosure is the continuity of the insulation and air barrier system. It is much easier to accomplish this by adding insulation to the outside of the walls, however the Falkland house is attached to the adjacent building by a party wall and both the north and east walls are at the property lines.

External insulation was not a viable option at Falkland, so it was designed as an internal retrofit.

The amount of insulation that can be added in an internal insulation is typically less than adding it outside because of the limitations of working around existing building elements and because it decreases usable floor area. For example, the house has a side hall plan layout with the stairs located on an outside wall. Space for insulation at the stair could be increased by only 2 inches. The component method offers more flexibility in meeting the targets when installing internal insulation, so this was the approach taken.

The existing wood shingles and board sheathing were retained, as such the retrofitted perimeter walls were designed to be vapour open.

They have been furred out, with staggered studs to make a 7-inch cavity, then filled with dense-packed cellulose insulation held in place with Intello Plus variable permeability vapour control membrane. The walls have a u-value of 0.24 W/m2K or RSI-4.1 (R-23).

Most window dimensions and locations were retained, however south- and east-facing window area was increased to optimize solar gains. The new windows and most doors are wood frame, aluminumclad, triple-pane. They have a g-value of 0.53 and an average u-value of 0.93W/m2K (RSI-1.08, R.6). The new front entry wood door with transom and sidelights emulates the original entrance but does not meet Passive House specifications, however, sourcing the door locally guaranteed the best fit. Despite the lower performance of this door, the average performance of all windows and doors in the building allows the window component target to be met.

PROJECT CREDITS

SITE | LANDSCAPING | RAINWATER HARVESTING

>ACO Systems

>Filterra Bioretention Systems/Langley

Concrete Group

>Molok North America Ltd.

>Roth North America

>Wishbone Site Furnishings

STRUCTURE & EXTERIOR ENVELOPE

>475.Supply

>Airfoam Industries

>Arriscraft

>Architek SBP Inc.

>CAYAKI Charred Wood/ CFP Woods

>CBC Specialty Metals and Processing

>Engineered Assemblies

>Fraser Wood Siding

>International Timberframes

>Kalwall

>LP SmartSide

>Live Roof Ontario

>N.A.T.S. Nursery Ltd.

>Radon Environmental

>Siga

>Thames Valley Brick & Tile