Blowing Hot and Cold

Preface of incentive

At the time when we signed up to Porter Davis, they had an incentive running that ‘Paid the stamp duty’ for first home buyers, as they didn’t want people to hold out a few more months while the new laws came into effect on the 1st July 2017. Instead of taking up the stamp duty offering, we were given free Evaporative cooling, we were then able to exchange this for a WOS credit as we chose not to go with Evap cooling. This was noted as a $6,979 credit in our contract which will come off our final payment to Porter Davis.

Gas Heating

All Porter Davis homes come with at least a 3-star Brivis Gas heating system. It’s part of the 6-star energy requirements for Victoria.

When working with Porter Davis on heating and cooling options, you have to deal with the team at Brivis who are sometimes referred to as “Liveability  consultants” (read my other blog called “Getting the structure  right.” to understand what I really think of Liveability  consultants.)

We had many discussions with the Brivis reps, this included the weekend, weekday and off-site managers. The below photo sums it up quite nicely – empty with no one working.


Moving on…

They have set up in their computer system the default heating and cooling points of each home.

Forsyth 35

Because we added on more rooms to square off the back of the house, Porter Davis said we had to upgrade our Brivis unit to adequately heat and cool our home, this was going to be an additional $1,257.00 for a medium Brivis unit, this was a 5-star unit.

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However, we did not want to go with Evaporative cooling but instead run with refrigerated cooling.

Brivis informed us that we would need to upgrade our Heating unit from the 3 Star in our standard inclusions to a 6 Star unit if we wanted to add zoning and/or refrigeration. Probably it was possible to upgrade to 5 Star unit that could handle the add-on aircon unit, however, the 6 star unit had far better cost savings over time and more efficiency.




With the Brivis 6 star unit, we can have up to 4 zones for BOTH heating and cooling.

To run heating and cooling through the same ducting system you need to increase the size of the heating ducts provided, from 6 inches to 9 or 10 inches. This allows for the greater airflow required for your refrigerated cooling.

Photos of 1st story voids with heating and cooling ducts


Once this is done, you can create zones with 2 or more outlets.
It is not usually possible to zone just one room unless you have 2 separate outlets in that room. We have this situation in our downstairs guest bedroom, there is already a void placed in our upstairs master wardrobe to allow for the ventilation ducts in the guest room, however, to have the room zoned off by itself, we needed to add a 2nd separate vent, we did this by including its ensuite in the zone. Unfortunately, it meant that a void was needed above this area, requiring a 2nd void in our master bedroom wardrobe.


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On the plus side, because refrigerated cooling air runs in the same ducts as the heating air, only one duct is needed, this means the internal space requirements for the voids are smaller and we were able to reduce the size of all the voids down to 250mm wide x 600mm deep.

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To create additional zones their pricing is very expensive (no surprise)

Upgrade to 2 Zones is $1001.00
Upgrade to 3 Zones is $1394.25
Upgrade to 4 Zones is $2200.00


Costing below taken from our tender doc. These are not our final costings.

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The 4th Zone

We want the maximum 4 zones in our house to help with efficiency and ongoing costs but are only getting 3 through PD. we are creating 2 zones in our downstairs area and one zone upstairs. The upstairs zone is controlled via a network controller in our Games room which runs back to the main unit in the ceiling. One of the downstairs zones is the Guest bedroom and Guest Ensuite, and the other downstairs zone is all the open-plan living area. The large zone will be controlled by a fancy touchscreen controller (upgrade) and the other zone has a thermostat only which will be upgraded to a controller later.

The 4th zone will be our master bedroom and ensuite, which can easily be added after handover during the refrigerated cooling install for no additional cost.  Allowing us to create our own atmosphere and not effect anyone else in the house.




Having come from New Zealand we have never heard about Evaporative cooling, but appears to be something quite common here in Victoria.  The system only really lowers the temperature by 10 degrees and does not work effectively in the height of summer.  For the units to work you are required to leave doors and windows open and this is not appealing.

My husband is a hotty, which is fantastic on cold winter nights however he overheats in summer and would prefer temperatures in the low 20’s.  To achieve this we will need to install refrigerated cooling.

The Porter Davis cost for adding on a refrigerated cooling system is outrageous. We are building a 38 Square house and the quote was $16,366.00 for 13 outlets of refrigerated cooling addon and still required us to upgrade our Heating unit from 3 star to 6 star.




Doing it Post-handover

We found a great company (Dale Air) who will do this for us post-handover and will only cost us $8,315 for everything we want done.

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More pricing from Dale Air later on.

There are a few things you need to get PD to do during the build, as changes cannot happen downstairs after handover. However, your external 3rd party installer can do anything upstairs after handover.

This is all much easer if you are in a single story house… just leave it all out and do everything post handover 🙂

As mentioned earlier, the main thing you need to get PD to provision for is the increased sizes of your heating ducts to allow for greater airflow for your refrigerated air.
You will also need to get an additional outdoor power point installed for the external cooling unit that lives normally outside near your hot water cylinder.  This needs to be adequately rated to cope with the type of unit you decide to go with. i.e. single or 3 phase outlet, more about this later.


All downstairs ductwork must be done during the build, so you must make sure you have thought about where you want heating and cooling in your downstairs areas, like creating a drying room in your laundry.  Upstairs is much easier for them to add in extra outlets should you decide later on you need extras.

We have decided to get PD to install all our ductwork during the build, as we have a 22.5-degree pitch on our roof and the ceiling space starts to get very congested with all the ducts, insulation. cabling etc.  The last thing we want is for the poor air-con installation guy struggling to get around and accidentally stick his foot through our brand new ceiling.

Additional outlets and costs

Additional 6″ Heating Duct is $150.00
Additional Evaporative Cooling duct is $227
Cost to upgrade 6″ heating duct to larger 10″ is $115

To work out the cost to provision for ducted cooling, add up the total number of heating outlets in your house design and multiply by $115.
If you wish to add extra outlets, each outlet will cost you $150 plus $115 to upgrade size. (2 step process)


According to the Australian Government on their “YourHome” website you should insulate ducts to at least R1.5 and make sure all joints are well sealed.

Control units

There are a range of different controllers available for the Brivis system.  Here is the link to Brivis website to see what options are available
However, I don’t think PD offer all these options.  We choice the Brivis Touch and a network controller

With a double story build, if you require 2 downstairs zones and want separate control for each, you need to make sure you have this organised with PD and your 3rd party contractor prior to the build.  We discovered that PD will only allow you to install 2 control units even if you have 4 zones.  This would mean one upstairs and one downstairs, however, our friendly heating and cooling expert, at Dale Air, told us that we can have up to 4 separate controllers for 4 zones if we want, despite what the Porter Davis Brivis rep told us. Porter Davis will not install a second controller downstairs, so you need a control cable run into that second zone so that post-handover it is easy to convert to a controller.  This controller will cost us $220.  We just had to make sure that a cable was installed where we wanted the controller located.  To get around this we asked Porter Davis to install a remote temperature sensor in that position where we will later swap it for a controller.

temp sensor.jpg


The App

We were told by the PD Brivis rep that upgrading to the Brivis Touch controller would allow us to control the whole system without even being at home via an app for our Smartphone.  This was a huge selling point as it meant we could pre-heat or cool the house before we even got home.
Unfortunately, this was a complete lie, as there currently is no such app available.  Our Dale Air representative told us that it is something that has been in the pipeline for years, but is not currently live because of privacy reasons around ex-owners still having control of your heating/cooling unit or some such palaver.  We are hopeful that this will be rectified shortly and that it will be rolled out and that our current touch unit will just require a firmware update rather than having to be replaced with a new unit.


We cannot get 100% confirmation on when this App will actually be launched so we have opted for the manual controls in each zone just in case this App never eventuates.


Return Air Vent

In a ducted system, hot air is circulated through the roof or underfloor ducts, supplying convective heat.

Well-designed ceiling outlets can work well particularly when rooms are sealed from draughts to the outdoors. Cold air entering under outside-facing doors can form a layer above the floor and stop the less dense warm air from ceiling vents heating the air near the floor, creating a ‘cold feet–warm head’ problem.

A return air path from every outlet back to the central system is very important. Without it, the warm air escapes and the system sucks cold air in, dramatically reducing its effectiveness. In each room that has a duct outlet installed, a gap under the door between the room and the central return air inlet creates this return path.

With ducted gas systems, a fan moves the air around the home, using electricity as well as gas. High-efficiency ducted gas systems use more efficient motors/fans and control the fan speed, to reduce electric running costs.


Electrical requirements

Most ducted refrigerated air conditioners only require single phase power for the outside unit to run, however, we did spend some time toying with the idea for a 3 phase unit as these units have a higher output rating and we already have 3 phase power to the house so there were no additional costs there.

There are pros and cons for both options but a large pro for the single phase units over the 3 phase units was the advances in the inverter technology.  These units will save you lots of money in running costs.  The inverter models can adjust their power consumption as your cooling requires increase or decrease.  Whereas, the larger, non-inverter style units only have a full-on power mode and the temperature control is managed via the volume of airflow.


Access for indoor unit

Once I have handover from PD, I will ring my Air Con guy and have him come and install a 17kW refrigeration unit which will bolt onto the heating unit in my upstairs ceiling space. This unit is too large to fit through your manhole so the installer will remove roof tiles or Colourbond sheets to gain access to the area where your current heating unit lives.

Outdoor unit

Included in our Dale Air quote is a large and somewhat noisy external unit.  This is placed on a concrete slab and should be located away from any bedroom windows.  The concrete slab is including in our Dale Air quote.  This outdoor unit must connect via a couple of conduits to the internal unit in the ceiling space.  To avoid having these run externally and destroying the aesthetics of your new home it is important that you get along with your site supervisor.  You will need to gain access to site just after framing stage so that these conduits can be run through the external wall frame and into the ceiling space.

Display home

In most PD display homes they have provisioned for Evap cooling, you can see the 2nd larger ducts in the ceiling. However, in some display homes, they also have a sneaky refrigerated cooling unit sitting out by the garage and piped into the sales office and through the rest of the home. A few time we have stood under evap cooling outlets and there is no way its evap cooling coming out of it – we have even tested this by closing all the doors and windows to do the pressure test.



Extra extra Air

We went off on a tangent when considering extra airflow to assist with the refrigerated cooling.  We noted on the Brivis website that they had a SP635 heating unit and it had better airflow than the 630IN with the extra air add-on.

Below is a copy of the quote we received and an exert from an email explaining each line item and it’s associated cost.

I will break down the quote for you by item number:

Item 1: SP535IN, this reflects us upgrading to a 35kW heater at a 5-star efficiency level, this would cost $3370.00
Item 2: this is to upgrade from a 5-star efficiency heater to a 6 star, this would cost $950.00
Item 3: I did zoning as 2 zones upstairs/downstairs since we can no longer have that guest room on its own zone due to the outlets. For two zones it is $1001.00
Item 4: This is the Brivis Touch controller which we relocated into the nook in your kitchen, while the standard networker will remain upstairs. The Brivis Touch is $364.65
Item 5: Provisions for future add-on cooling to 13 outlets, including upgraded duct work to suit future cooling.
Item 6: Upgrade to downstairs outlet size as these will need to be 10” outlets to suit the space while upstairs will have 8” outlets, this will cost $320.00
Item 7: is just reflecting the additional outlets that were needed in your master bedroom and downstairs lounge & I put the ensuite and bathroom outlets in this item also they are worth $600.00 altogether (this is their worth before the future cooling provisions which I priced in previous items.)

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We were very taken back by the costs quoted to upgrade to the SP635 unit.  Dale Air, who will be installing the refrigerated system, indicated that the cost increase should be in the vicinity of $300 – $400.  However, the above quote would end up costing us $2,283 more than to upgrade to the SP630IN.  We did note that the cost to upgrade the ducting worked out cheaper in this quote ($70 each) as opposed to the original quote @ $115 each.  This, however, did not offset the outrageous cost difference between an upgrade to SP630 vs SP635.

I just couldn’t believe that to upgrade from 3 star to 6 star SP630 would cost $2037.75, but to upgrade from 3 star to 6 star SP635, I would need to pay $4320.  That just seems absolutely preposterous.

Dale Air pricing below


The PD price was way outside of our justified budget for a heating and cooling system.  Therefore we reverted back to the SP630in-XA and options.

Below is what we signed off on.

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Dale Air

Dale Air was recommended to us from the Home One forum, there is great feedback about their work on the site.  From the 3 visits to their showroom (it wouldn’t take a normal person 3 visits – we are just a little over the top in an obsessive-compulsive way) and his presence at the Home Show, we feel we are in good hands.




Co-written by my husband Dave, who wanted me to hurry up and publish this blog so it will help others who keep asking questions on the subject.

6 thoughts on “Blowing Hot and Cold

Add yours

  1. Thanks for the blog series thus far and this one too…luckily we had the free Refrigerated cooling offer when we started our build, so it seemed like a no brainer to go ahead with it. The only change we made was to add an additional zone in the upstairs void area – which we were able to arrange directly with PD’s supplier (just sneaked this in when they called me to confirm a few details) at a cost of $550 for the additional zone.

    Please keep this blog series coming. Although we are just a few weeks from handover (hopefully!), I’m sure it will help countless others. I think more or less we made some other design decisions similar to you folks, but had we had the inputs from your blog, we may have changed a few minor things here and there. Too late for the shower heads though…but we are short people and the standard heights should be ok for us 😝

    Selfishly seeking – If you have thought of preparing any handover checklists/ things to double check prior to handover, please do publish them. I’ll share the key items that I will be looking out with a fine tooth comb prior to handover myself and will publish them on my build thread on the Homeone forum (Sinbox & my build thread is here:

    Liked by 1 person

    1. Ho Sachin, we have been following your blog as Sinbox, I can empathise wiht your drawn out build process, and hope you get to PCI soon. Yes ​I will keep going with the blog – slow and steddy. We have not got to handover yet so I dont ​have enough to write a blog about that one yet lol cheers C.


  2. Great information! Have you looked into a NEST controller instead of the Brivis default options…I think they have a remote control option (mobile app) along with other neat features and can be retro fitted providing wiring is compatible. Anyhoo, Enjoy your new build!

    Liked by 1 person

  3. Thanks for the great advice on your adventures of heating cooling, just to confirm your prices on cooling you spend $6156 at WOS plus $8315 at Dale air ?


      1. Thanks Charly , did you end up working out what the cooling would actually be with PD, not just what the tender quote of $16k approx that we got ?


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