Fix up, warm up

By - , Build 132

The first house in Beacon’s Build Back Smarter project shows how earthquake repairs offer a golden opportunity to improve performance.

The 1960s Huntsbury-2 home.
The 1960s Huntsbury-2 home.
Removing plastered concrete block veneer.

THE BUILD BACK SMARTER PROJECT in Christchurch is upgrading 10 homes while they are undergoing earthquake repair. Beacon aims to demonstrate how performance interventions can be included in the wider Canterbury repair programme, improving home's thermal performance, energy and water efficiency and indoor environment at the same time.

The repair and upgrade plans

The first house in the Beacon project is Huntsbury-2, a large 1960s concrete block and stucco house with a first-floor extension built in the 1970s and a basement garage. The Build Back Smarter upgrade plan built off the Project Management Office’s (PMO) scope of works and was developed in consultation with the homeowners, PMO and the Energy Efficiency and Conservation Authority (see Table 1).

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Plans evolved during renovation

As happens with renovations, plans changed as work proceeded.

The builder’s first step was to remove the stucco veneer. However, as blocks came down from the outside of the lounge wall, the builder found there was no building paper but, surprisingly, there was some 1970s insulation retrofitted to two of the lounge walls.

Bad weather meant building wrap had to be fitted progressively as sections of veneer were removed and the coordination needed and the health and safety risk with workers on scaffolding meant wall insulation was not added from the exterior as planned.

However, most interior linings on ground-floor external walls were removed because of cracking and sheet bracing and new plasterboard fitted. This change of plan allowed the poorly fitted and slumping existing insulation to be taken out and nearly all the downstairs external walls to be insulated, more than first planned.

Insurance assessors had limited upstairs work to the minimum possible with no opportunity to install wall insulation. However, once the builder was on site, he noticed more cracks. Because of the difficulty in removing wallpaper, he removed and replaced plasterboard as the quickest repair option in some rooms.

Again, there was an unexpected find – some of the extension had perforated foil in the wall behind the plasterboard.

With the linings off, the first-floor external walls were also insulated. Building wrap inserts were fixed between the new insulation and the back of the exterior fibre-cement board cladding.

Due to these changes, most of the house now has wall insulation installed, and it was decided not to replace the hot water cylinder in order to keep the project within budget.

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Learning from the process

  1. Consider the PMO’s scope of works as the minimum repair work required. It has been assessed by non-intrusive inspection.
  2. Earthquake damage is often more extensive than expected. Scope change is typical in the repair process.
  3. The extended scope of insurance work caused hold-ups on this house, not the Build Back Smarter upgrade process.
  4. Insulation and building wrap can only be confirmed once claddings and linings are removed – there may be surprises.
  5. Insulation installers need to be on call and able to respond to the main contractor’s pace of work and expanding scope, returning to site as required to complete insulation installation.
Table 1
Ceilings Replace internal ceiling linings. Top up ceiling insulation.
Floor   Add underfloor insulation and install vapour barrier.
Wall cladding and linings Downstairs – replace all stucco veneer and some wall linings. Install insulation in walls downstairs.
  Upstairs – patch stucco cladding only.  
Heating Replace 2001 wood burner. Add heat transfer system to warm upstairs.
Windows   Install double glazing in two south-facing bedrooms.
    Add draught stripping to wooden windows and doors.
Unvented rangehood   Replace and add external venting.
Old hot water cylinder   Replace with solar or heat pump-compatible cylinder.
Removing plastered concrete block veneer.

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The 1960s Huntsbury-2 home.
The 1960s Huntsbury-2 home.
Removing plastered concrete block veneer.