Case Study House #29: Julie’s Net Zero Merchant Builders Retrofit

Alistair McLean

Category: Dr Retro House Calls, Renovations, Sustainability

Title: ‘The Courtyard House’ – for Merchant Builders Pty Ltd. Cnr. The Boulevard and Springvale Rd. Glen Waverley. Graeme Gunn. 1965-66 Author / Creator: Peter Wille 1931-1971 photographer. Contributor(s): Graeme Gunn Date: 1965-1966 Reproduction rights owned by the State Library of Victoria

Julie first approached Secret Design Studio in March 2019 for a Dr Retro House Call to help her with the next stage of her “renovation” of her Merchant Builder’s Courtyard house variation in one of Melbourne’s loveliest eastern suburbs. But renovation isn’t really the correct term to describe what Julie wanted to achieve. She loved the existing character and elegant, understated style of her Merchant Builder’s modernist inspired home, and it wasn’t going to meet the future needs of her household for comfort and future sustainability. Now, two and a half years later, looking at the work that has been completed Julie prefers the term “retrofit”, and going back to her original photos and her current photos you need to look carefully to pick the differences.

Original elevations by Merchant Builders. Julie’s home was derived from Merchant Builders popular “Courtyard House” design and was built in 1977, although the original design dated from the mid 1960’s.

Prior to our meeting she gave me some background to her home of 20 years:

“Thanks Alistair for speaking with me yesterday.
As I explained our home is a custom design loosely based on the Merchant Builders Courtyard House.
Ours is C shaped with a pergola over the courtyard and a double carport at the front – joined to the house via a pergola.
We have the Clifton grey bricks with struck mortar.
The brick panels have single brick returns at each end – with a full height recessed window to form the construction joins. It is a clever detail that means we have no cracks in the brickwork. The panels support long Oregon beams internally.
When we moved in 20 years ago – previous owners had painted all the beams and windows and plastered the timber lined raked ceilings when they put in down lights.
We repainted the house, put in hydronic heating, replaced the pergola. put in pale marmoleum floors, new laundry, new decking, PV panels, new landscaping, repaired the kitchen and replaced the wardrobe doors – as well as putting in small opening windows in the tall windows.
As I mentioned – the house is freezing in winter and we have serious maintenance issues with the external Oregon.
The to-do list is long. Matt is confident that he can restore the kitchen and it looks like we can install a heat pump HWS in the existing HWS place – by putting the condenser on the roof.”

Original section by Merchant Builders. Julie’s home was derived from Merchant Builders popular “Courtyard House” design and was built in 1977, although the original design dated from the mid 1960’s.

On meeting with Julie for her Dr Retro House Call consultation I was struck by her love for her home and the depth of research she had done prior to my visit about how best to make it work for her household for the next twenty or thirty years.

Looking back on my meeting notes from 2019 I can see that I answered a lot of her queries about a wide variety of broad ranging topics during the two and a half hour consultation. Such as:

The front carport, including the materials, lighting and flashing details,
the courtyard pergola, materials and repairs,
metal deck roof replacement,
profile and colour,
the issues with inadequate sized gutters and downpipes,
lack of roof space for electrical and ducting,
skylights, type and size,
insulation,
PV panels,
chimney repair,
heating cooling options,
removing downlights and lighting strategy,
entry door,
window style and window coverings,
ventilation to wet areas and
internal and external paint colours

Original floorplan by Merchant Builders. Julie’s home was derived from Merchant Builders popular “Courtyard House” design and was built in 1977, although the original design dated from the mid 1960’s.

I was thrilled last week when Julie contacted me out of the blue to say that not only had all the work been completed on her home early in 2020, but she had achieved a remarkable 10 star rating on the Residential Energy Efficiency Scorecard, and an all electric, net zero result for the housholds energy consumption. Due to the original careful orientation of her Courtyard House the roof was perfectly orientated for a large PV solar array, which generates 150% production of the households energy consumption. This is a remarkable result for a house that she described as “freezing in winter” back in 2019. After 12 months Julie says that her small household averages about 4kWh/per person/per day annual average.

I know from monitoring my own PV panels that working on averages over 12 months is perhaps the best yardstick as there is a big variation in the length of time that the sun shines between the middle of winter and the middle of summer in Melbourne, which has a huge impact on the amount of electricity generated.

Back to Julie:

“Hi Alistair,

Prior to the build – I worked through my priority list to determine the feasibility of all the elements. The most difficult to execute element was putting ducted air conditioning in a cathedral roofed home. I wanted to do this – so that not only could I go all electric but also reinstate the original indirect lighting. Wall hung units would have made doing the lighting this way difficult. I interviewed a company (Alpha Air) that was prepared to consider how to do this and they recommended the builder that we went with.

Link to alpha-air heating and cooling website