Let’s Talk About Performance - Chatfield Project

Early in 2019, we were engaged by the amazing team from Altereco Design in Seddon to work through their pre-tender and negotiated tender phase. This process was completely new to us, but in the end, it made the project a lot easier to tender for. We were happy adapting to the plans and balancing items to keep within the client’s budget. It gave us a chance to discuss any potential issues we may face onsite and iron them out early. We felt there was a higher level of trust going into the construction phase between the Builder, Client and Designer - which also made the job run a lot smoother.  

So what makes this job different? Brooke and Andrew's focus was to create a sustainable house that was going to perform better than the majority of homes that are built. Too many people forget what happens behind the plaster, but on this project, extra care was taken to maximise the future performance of the home.  

Rather than have a sustainable approach, we decided to move towards the construction of the house with a passive approach. In the early stages of the design, I spent a week at Box Hill Institute studying the internationally recognised Passive House Course. This opened my eyes to many potential issues with the way we currently build houses. It scared me and made me sit back and re-assess how we go about things as an industry. I will go into more detail around Passive House in a future post, but I recommend that you do your own research if you’re interested in learning about a new standard of building. I am proud to say that I am now an accredited Passive House Tradesperson and it has transformed the way I now build homes.  

What this course did teach me is that if you are going to do something, do it properly. As builders, we are already installing windows, insulation, sarking etc. so why not do this to a higher standard? All it takes is a few tweaks to change old habits, but the results are exponentially better. 

Of the five key Passive House principles, the one that stood out to me the most and is the easiest to implement, is ensuring your building is as airtight as possible. For our Chatfield Project, the extension of the house was made as airtight as possible. We used a membrane called Solitex Extasana to wrap the house like a present and substituted traditional blanket insulation on the roof for Solitex Mento. This product does a great job at providing weather protection against wind and water but also allows any internal moisture to escape. We also taped every corner and opening using specific tapes that will prevent air leaking out from the home in the future. 

An airtight home will perform measurably better for efficiency and thermal comfort. The average new house in Australia has an air change rate of 15.4 ACH@50pa whereas a traditional, poorly sealed house will have a rate of 30 ACH@50pa. To achieve the Passive House Standard, you need to achieve a rating of 0.6ACH@50pa. Although our Chatfield Project was not tested, we are confident that we have done enough to get it closer to the Passive House Standard than a traditional home. This will allow the house to perform better by reducing the heat lost during winter and making the home less reliant on space heating.

We also made a conscious effort to insulate even better than we did before. I found that by tweaking a few more things, this process could be significantly improved. There are 3 methods that have now become second nature to my team when installing insulation. 

1.    They no longer cut out holes for down lights and power points in the insulation. 

We use to do this to prevent the insulation catching fire from the heat that down lights used to produce, however as technology has changed and you can purchase down lights that are IC Rated.  

2.    Spray foaming around windows. 

This is one of the greatest leakage points in a home. Just put your hand near your window on a cold day and you will feel the cool breeze coming through. We have been foaming around our windows for years, but we knew this could be done better. The use of specific tapes helps give the foam a point to stick to so it does not expand out all over the frame. 

3. Always have a bag of insulation ready to go.

This is something that I challenge all builders to follow. When we wrap a house, certain corner junctions can only be accessed before we wrap the house. Go around with a bag and insulate every corner that is going to be covered in ply or with sarking. These little gaps add up. If you miss them, drill a few holes in your corner studs and fill it up with spray foam. 

Within the design, Altereco opted to use Double Glazed Timber Windows with Low E coating on the required windows. These guys are going to perform so well, as they have such a low u value and SHGC which helps to increase the thermal efficiency and reduced thermal conductivity. There is an argument that timber windows rot out. This can be true is true, however, we went above and beyond on this project, using special flashing tapes and coating them in 3 layers of external Cutek oil to minimise the wear and tear of the timber. This will only do so much, and like every house, you will still need to maintain it. No matter what windows you use, they need to be looked after or they will not perform or last as long as they should. Think of it like a car - if you don't regularly service it, you may end up having major problems that can be extremely expensive to fix or requires the car to be replaced altogether. So if you service your car, it also makes sense to service the greatest asset in your home! We did look into alternative options for windows such as hybrid timber and aluminium, thermally broken aluminium and UPVC, however in this case we found that timber windows were going to provide the best performance for the dollar spent. 

We also removed gas from the property completely as there was no longer any need for it. Andrew and Brooke have solar panels on their existing roof and are looking to increase the number of panels in the future, plus with all-electric appliances and a Sanden Heat Pump to provide hot water, it was something that they were able to go without. 

So why is this a better option? Gas is not a renewable source; it contributes to carbon emissions compared to using solar panels, it is expensive to run when you incorporate the daily charge of gas and the cost of gas continues to rise. If you are renovating your house, you can easily design it without the need for gas. It may baffle some people as to why you would remove gas, but I encourage you to do some research into it. Reports have shown that homeowners will be $9000-$16,000 better off over 10 years if they have an all-electric house with solar rather than stick to an out-dated gas-electric house. You can read more about this here.

In addition to the above, we also implemented the below practices to enhance the performance of our Chatfield Project:

· Increased external walls to have an R-Value of 2.7

· All ceilings were increased to the maximum R-value that would suit the depth of the rafters

· The existing subfloor was insulated

· All external walls were battened out to allow for moisture to drain but also provide an air gap that will assist with the R-value of the home

· A water tank was installed to catch rain from the new roof area

· All timber cladding was from a sustainable source

We are so happy with the final result of this home. You can see the final pictures on our website or through our Instagram feed. It was such a pleasure to work with our clients Brooke and Andrew throughout the project and we can't wait to hear all about the improved performance in their new home.