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

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.

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.”

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

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
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

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

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

Julie’s home is featured in Issue 54 of Sanctuary Magazine “Energy Efficiency Front and Centre – A renovation case study”, photographer Jill Haapaniemi

The whole rebuild took 3 and half months during the start of the pandemic.  It was only after the project was completed that I had the energy assessment by Tim Forcey and thermal imaging and blower door testing by EcoEVO.

Link to Tim Forcey website

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

Julie’s home is featured in Issue 54 of Sanctuary Magazine “Energy Efficiency Front and Centre – A renovation case study”, photographer Jill Haapaniemi

This was only because I was encouraged by a ‘town hall’ meeting in the lead up to the council elections – to see if the project was suitable for a case study and look at our data.  The post retrofit results were really good – so I approached Renew to see if it was something they were interested in and they were keen to publish the project – so I got the verification and energy assessment done.

If I was doing this again – I would get a NatHERS assessment of the original house and model the decisions to refine them.    Jenny Edwards – who is a building scientist – has a company in Canberra that does a lot of this sort of work (although the Lighthouse team weren’t engaged for Julie’s retrofit).

Link to Jenny Edwards of Lighthouse team

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

Julie’s home is featured in Issue 54 of Sanctuary Magazine “Energy Efficiency Front and Centre – A renovation case study”, photographer Jill Haapaniemi

The EcoEVO guys that did the thermal imaging and blower door testing have excellent videos on their website on insulation installation and comprehensive air sealing.

Link to EcoEVO website

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

Julie’s home is featured in Issue 54 of Sanctuary Magazine “Energy Efficiency Front and Centre – A renovation case study”, photographer Jill Haapaniemi

This is recent article in Renew – that shows how the NatHERS iterations can guide retrofit choices.

Link to Sanctuary Magazine article

Kind Regards

Julie”

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

Julie’s home is featured in Issue 54 of Sanctuary Magazine “Energy Efficiency Front and Centre – A renovation case study”, photographer Jill Haapaniemi

Julie has a 6.6kw PV solar on the roof and a household of three people which use on average 12kWh per day.

The household imports 6.9kWh per day (probably at night when the PV is not getting any sun), and consumes 5.1kWh from the PV solar generation.  By being able to export 13.5kWh during the day back to the grid the household is saving about $1900 per annum on previous bills.

The last time one of our client’s homes was included in the annual Sustainable House Day was back in September 2018 – here is a link to the blog posting:

Link to “Sustainable House mid-century style” blog post by Secret Design Studio fr0om September 2018

So I am really pleased to hear that Julie will be involved in this year’s Sustainable House Day on Sunday 17th October, although it won’t be an open house format as was in earlier years 2018 due to Covid restrictions.

If you would like to read more detail about Julie’s house then here is a link to her profile from the Sustainable House website:

Link to Sustainable House Day “Net zero Merchant Builders Retrofit” more detailed information

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

If you would like to see a short 7 minute video about her home then here is a link to YouTube:

Youtube video link to “Net Zero Merchant Builders Retrofit”

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

A really good resource to start to understand your climate zone and ways to improve your home is the independent Government website, Yourhome, which is Australia’s guide to environmentally sustainable homes, and is a resource that Secret Design Studio often refers to,

Link to Your Home website

 

The most important lesson to be learnt from Julie’s retrofit is that the individual initiatives taken to improve energy efficiency of a home should not be considered individually, and the whole house should be considered together as a complete system. Professional advice using various tools such as thermal imaging cameras,  energy monitoring systems and blower testing can work together to provide a more complete picture of your home.

Secret Design Studio’s thermal imaging camera can detect subtle changes in temperature to show cold spots and hot spots that are invisible to the naked eye. In this case the camera is picking up a leak that has been absorbed into the insulation above the plasterboard.

 

If you would to book in a 2-hour in-home consultation service to get some answers about your future renovations and improvements, then please fill in an enquiry form now, and Dr Retro will be in contact with his available dates, times and service fees.

Link to “Dr Retro House Call” availability enquiry form