High Performance Case Study

Retrofit

North Rd, Newport

Project Brief:

As a family of 3, the client is looking to refurbish their current dwelling to increase its livability. They also find their current home to be difficult to heat in winter and cool in summer and would like to improve its thermal performance. No works are proposed beyond the existing building footprint.

Site Conditions:

The site is located in Newport with immediate access to parks and public transport. This is not your ideal passive solar house due to a north facing street frontage and living spaces facing a southern back garden.

Existing Building Conditions:

The existing building is a freestanding Inter-war weatherboard with a 90’s rear addition continuing the original tiled hip roof. As expected, this building performs very poorly with single glazing throughout, gaps in sash windows, timber flooring, wall vents (to name a few) plus almost no insulation. Existing heating is provided through a gas ducted system and ceiling fans had been retrofitted.

The building presents the capacity to house all of the functional requirements for this family, however the layout, especially the extension is poorly design, very dated and natural light is an issue. Thermal comfort in a house of this era is a constant battle.

Design Strategy:

Whilst improving the functional layout of the home, incorporate new wet areas and improving connection to outdoor spaces, we are challenged to improve the performance of this home. This is our strategy;

  • Provide new windows & doors to the living spaces and replace existing windows where appropriate

  • Alter the existing layout to introduce heating and cooling zones for the north (bedroom) and south (living) wings

  • Provide new cladding to the the south wing with additional wall, roof and subfloor insulation

  • Explore options to improve performance of the north wing, where cladding is to be retained


ArchiCAD View 1.JPG
ArchiCAD View 2.JPG

.Baseline Assumptions:

To assess the existing building performance we have input the following values into our software to create an annual baseline heating and cooling load.

Existing Envelope:

Floor: Timber flooring on 100mm joists - no insulation

Walls: 90mm Frame with no insulation

Roof: Pitched roof, R4.0 ceiling insulation

Existing Windows:

Timber framed single glazed (no thermal break)

No additional shade protection

Airtightness:

15 Air changes per hour (10 air changes per hour is assumed by NatHers for 6 star, but given the performance of existing building fabric we believe this is a more realistic and possibly conservative figure)

Energy required for annual operation of the building: 124.63 kWh/m²*

High Performance Strategy:

By using the Passive House tool - DesignPH - in conjunction with a SketchUp model of the building we are able to assess and dissect all of the elements that contribute to heating and cooling loads.

Sketchup View 1.JPG

Step by step

  • The first step is to analyse the existing building as currently constructed. During our initial assessment we  decide what sequence of modifications will attain best ‘bang for buck’ for the project, ie maximum energy reductions with minimal additional construction cost.

  • Our first identifiable issue was the lack of subfloor insulation and the opportunity to increase the roof insulation. Both these changes are affordable and can be implemented with no alterations to the existing building layout. We added R2.0 extra to both these areas which resulted in energy demand reduction of 10%. 

  • The next step was to look at upgrades that could be made to the south wing (living) of the existing as part of the floor plan changes. With the cladding to this section of the building being replaced there is an opportunity to install R2.7 insulation and building wrap to the external walls. Also, new double glazed timber windows are to be installed.

  • We then looked at the overall air tightness of the building, intending to reduce this from 15AC/h to 7AC/h. This would involve taping all windows, sealing existing walls where possible, penetrations and an air blower test to ensure the quality of workmanship.

  • The final round of analysis looks at the north wing (bedrooms) of the building for which we currently propose to retain the existing cladding and only refurbish the sash windows and external doors. Our final calculation(#4) shows that completing the final weak point in the thermal envelope make a big difference. We suggest to retrofit blow-in insulation as well as replacing the existing windows with double glazed timber frames. Floor and additional ceiling insulation had already been accounted for in step 1.


    As shown in the right hand column on the table below, Specific annual heat demand.

PH Results Table.JPG

Summary of features

Envelope:

Floor: Timber flooring on 100mm Joists - R2.0 insulation

Walls (South): 90mm Frame with R2.7 insulation

Walls (North): 90mm Frame with blow-in glasswool insulation

Roof: Pitched roof, R6.0 ceiling insulation

Windows:

Timber framed, double glazed throughout

No additional shade protection

Airtightness:

7ACH - Air changes per hour (10 air changes per hour is assumed by NatHers for 6 star)

PH Results Tracker.JPG

Results:

We would typically recommend implementing a mechanical heat recovery ventilation system (MHRV) to all homes that are improving airtightness. However in this ‘retrofit’ situation we only anticipate improvements to around 7ACH, which shouldn’t impact the indoor air quality enough to be a health risk. 

The diagram below compares the heat balance from the base  the the final high performance iteration.

PH Results Comparison.JPG

Some early analysis of the results provided the following:

Additional Construction Costs: $53,000**

Annual Energy Savings: 12,893 kWh (approx. 70% reduction)

Annual Carbon Reduction: 13.80 Tonnes***

Annual Savings: $3,868

Payback Period: 14 years

Although still far from a Passive House performance (we’d need to get down to 15 kWh/m2 & 1.0 ACH retrofit) there are some huge benefits from a high performing upgrades, especially at this scale, which we would t-shirt size as a medium-large sized house.

A reduced carbon footprint of 13.8 Tonnes per year is significant enough to make a difference in a time when reducing our carbon footprint is critical.

The additional construction costs include additional labour and materials that would otherwise be above and beyond the minimum spend for this renovation. 


Conclusion
Although still far from Passive House certified performance (we’d need to get down to 15 kWh/m² & 1.0 ACH retrofit) there are some huge benefits from a high performing upgrade, especially at this scale, which we would t-shirt size as a medium-large sized house.

The additional construction costs include additional labour and materials that would otherwise be above and beyond the minimum spend for this renovation. However this results in an estimated energy savings of almost $4,000 a year, which will eventually cover the cost of the extra upfront investment. On top of this there is a reduced carbon footprint of 13.8 tonnes per year, significant enough to make a difference in a time when reducing our carbon footprint is critical.

We all know that now is a critical time for us to reduce our environmental impact. We also know that this can be achieved without compromising our living standards. In fact an investment in high performance construction will actually result in an increase in livability!

Additional benefits from HP Building Method:

  • Comfortable year round climate (20-25C)

  • No more drafts!

  • Balanced indoor temp (no hot or cold spots)

  • Extremely low energy bills

  • Removal of gas guzzling heating and decommission of the gas meter, moving away from fossil fuel dependency 

*Our software makes the following assumptions; a baseline airtightness of 10 ACH; a thermal comfort level of 20-25 degrees is maintained 24/7; energy supply cost of $0.30/kWh; assume all energy supply is via electricity and not gas.

**We are not builders or quantity surveyors, this is an estimate only

***Carbon emissions calculated as per Carbon Calculator

This case study was prepared by Altereco Design in October 2019 to assist our client in understanding the viability of their upgrades. We hope that it assist others understand the cost versus benefit of improving the performance of their home.









High Performance Case Study

New Build

Stone Pine Court, Thirteenth Beach

Project Brief:

The brief is for a new 4 bedroom home including; second living area, 2 car garage and space to park a golf buggy. The new family home should be optimised to take full advantage of its lush views and include a swimming pool with visibility from all aspects of the home. Externally the building should present well to the street but be simple in architectural form. From the outset the client would like to avoid a gas connection and expects solar and heat pump technology will be required to achieve this.

Site Conditions:

The site is located at Thirteenth Beach, a new subdivision surrounding the 13th Beach golf course facilities. The new home will have great access to Barwon heads and surrounding beaches and amenities. The site itself is flat with N-S orientation and views of the existing practice fairway.

Design Strategy:

  • All electric home with no gas connection

  • Solar heated swimming pool centrally located to allow north facing windows into living area. Maximise visibility of the pool where possible

  • Living spaces oriented for fairway views and green outlook. Provide solar control through deciduous trees strategically planted on adjacent land to provide solar control.

  • Garage to act as a thermal buffer to the dwelling

  • Zoning of living and sleeping zones

Image 1.png

Steps

  • The first step is to analyse the existing design if constructed to 6-start minimum requirements. During our initial assessment we  decide what sequence of modifications will attain best ‘bang for buck’ for the project, ie maximum energy reductions with minimal additional construction cost.

  • Our first identifiable issue was the concrete slab and its connection with the ground. By decoupling this with an insulative layer of XPS board the transmission heat loss was almost halved. It appears that the benefits of insulating a concrete slab is grossly undervalued as it is common practice to avoid this as it can be difficult if not planned out correctly.

  • Secondly we addressed the transmission heat loss through the windows by replacing the aluminium frame with timber.

  • We then completed the improvements to the thermal envelope by increasing our walls to a 140mm stud frame, which allows for the installation of R4.0 insulation batts.

  • Lastly we addressed our ventilation heat loss improving our airtightness from 10AC/h to 5AC/h. This would involve taping all external membranes, around windows, penetrations and an air blower test to ensure the quality of workmanship.

As shown in the right hand column on the table below, Specific annual heat demand.

191015_Results Tracker.png


Summary of features

Envelope:

Floor: 100mm Concrete Slab on ground, 30mm XPS insulation, 80mm screed

Walls: 140mm Frame with R4.0 batt insulation

Roof: Truss roof R5.0 batts, Vaulted ceiling to living area R5.0 batts throughout

Windows:

Timber framed double glazed

Airtightness:

5 Air changes per hour (blower door test to ensure quality)

Airtight passage door to garage

Mechanical heat recovery ventilation unit (ensure high air quality and avoid sick building syndrome)

Energy required for annual operation of the building: 56.22 kWh/m²*
This diagram shows that we conducted 4 tests after our baseline was established, highlighting the sequence of our sequencing for this particular project.

191015_Results Tracker Chart.png

The diagram below shows the final test results directly compared with the standard construction baseline;

191015_Heat Balance Charts.png

Results:

Additional Construction Costs: $87,100**

Annual Energy Savings: 31,177.2 kWh (80% reduction)

Annual Carbon Reduction: 32.71 Tonnes***

Annual Savings: $9,353.2

Payback Period:9.31 years

Conclusion

Although still far from a Passive House performance (we’d need to get down to 15kWh/m2 & 0.6 ACH) there are some huge benefits from a high performing house, especially at this scale, which we would t-shirt size as a large house.

We found that by implementing some pretty simple strategies there are some serious economic benefits that can be expected. A payback period of only 10 years shows the significance of the operating costs of a building this scale. This makes sense from an economic perspective and the additional benefits listed below can be enjoyed by the occupant from day 1. Given that this is a family home, these added benefits of high performance construction would also continue to contribute to future generations.

A reduced carbon footprint of 36 Tonnes per year is significant in my book. In fact, it’s the equivalent to 26 Rhinos!

We all know that it’s no longer business as usual. By improving our designs and how they perform we can have a long lasting effect on the planet’s well being as well as our own.

Additional benefits from High Performance Building Method:

  • Indoor air quality, pollen and dust free

  • Comfortable year round climate (20-25C)

  • Balanced indoor temp (no hot or cold spots and draft free)

  • Extremely low energy bills

*Our software makes the following assumptions; a baseline airtightness of 10 ACH; a thermal comfort level of 20-25 degrees is maintained 24/7; energy supply cost of $0.30/kWh; assume all energy supply is via electricity and not gas.

**We are not builders or quantity surveyors, this is an estimate only

***Carbon emissions calculated as per Carbon Calculator









High Performance Case Study

Alterations & Additions

Hickford St, Brunswick

Project Brief:

As a growing family of 4, the client is looking to expand their current dwelling to allow for a second living area, guest bedroom and a space to work from home . They are also find their current home to be difficult to heat in winter and cool in summer and are keen to improve its thermal performance and general livability. The existing carport and significant trees are to be retained.

Site Conditions:

The site is located in Brunswick with good access to schools, parks and public transport. Main access is off Hickford St to the south with off street parking is by a double carport to a lane. Heritage overlays are in place to protect the existing character of the neighbourhood.

Existing Building Conditions:

The existing building is Bungalow with dated rear additions. As expected this building performs very poorly with single glazing throughout, gaps in the flooring and no insulation. Existing heating is provided through hydronic panels and water tanks and solar panels have already been installed.

Design Strategy:

  • A two story addition is proposed to the rear of the building. On the ground floor this is to become the primary living space, maximising the north orientation and connection to the backyard. The second story of the additions will contain additional bedrooms and a second bathroom. 

  • The additions are thermally separated from existing and are to be built to a high level of thermal performance.

  • The layout of the existing is to remain unchanged but the thermal performance will be upgraded as much as practically possible This will include include additional wall, roof and subfloor insulation.

  • The existing hydronic heating system is to be retained and extended into the new additions where practicable. Existing solar panels are to be relocated for increased performance.

ArchiCAD View 1.JPG
ArchiCAD View 2.JPG

Baseline Assumptions:

Envelope:

Floor: 100mm Concrete Slab on ground - No insulation

Walls: 90mm Frame with R2.7 batt insulation

Roof: Flat Roof R5.0 batts

Windows:

Aluminium framed double glazed (no thermal break)

No additional shade protection

Airtightness:

10 Air changes per hour (assumed by NatHers for 6 star)

Standard door to garage

Energy required for annual operation of the building: 82.90 kWh/m²*

High Performance Strategy:

By using the Passive House tool - DesignPH - in conjunction with a SketchUp model of our latest design we are able to assess and dissect all of the elements that contribute to heating and cooling loads.

Sketchup View 1.JPG

Steps

  • The first step is to analyse the existing design if constructed to 6-start minimum requirements. During our initial assessment we  decide what sequence of modifications will attain best ‘bang for buck’ for the project, i.e., maximum energy reductions with minimal additional construction cost.

  • Our first identifiable issue was the concrete slab and its connection with the ground. By decoupling this with an insulative layer of XPS board the transmission heat loss was more than halved. It appears that the benefits of insulating a concrete slab is grossly undervalued as it is common practice to avoid this as it can be difficult if not planned out correctly.

  • We then completed the improvements to the thermal envelope by increasing our walls to a 140mm stud frame, which allows for the installation of R4.0 insulation batts.

  • We then addressed our ventilation heat loss improving our airtightness from 10AC/h to 5AC/h. This would involve taping all external membranes, around windows, penetrations and an air blower test to ensure the quality of workmanship.

  • Given the relatively small amount of glazing in the design, windows were the last element to be addressed.  Through an upgrade to thermally broken windows and the addition of appropriate shading we were able to slightly reduce the solar heat gains.

As shown in the right hand column on the table below, Specific annual heat demand.


desingPH Results.JPG

Summary of features

Envelope:

Floor: 100mm Concrete Slab on ground, 30mm XPS insulation, 80mm screed

Walls: 140mm Frame with R4.0 batt insulation

Roof: Roof: Flat Roof R5.0 batts

Windows:

Timber framed double glazed (thermally broken)

Additional shade protection to north glazing

Airtightness:

5 Air changes per hour (blower door test to ensure quality)

Airtight door to existing

Mechanical heat recovery ventilation unit (ensure high air quality and avoid sick building syndrome)

Energy required for annual operation of the building: 23.94 kWh/m²*

The diagram below shows the progress from the baseline to the final performance solution. You can see that with each iteration the thermal performance in improved.


desingPH Tracker.JPG


Results:

The diagram below compares the heat balance from the base  the the final high performance iteration.

desingPH Comparison.JPG

Some early analysis of the results provided the following:

Additional Construction Costs: $45,000**

Annual Energy Savings: 7,487 kWh (approx. 70% reduction)

Annual Carbon Reduction: 8.01 Tonnes***

Annual Savings: $2,246

Payback Period: 20 years

Although still far from a Passive House performance (we’d need to get down to 15 kWh/m2 & 0.6 ACH to achieve that) there are some huge benefits from a high performing extension, especially at this scale, which we would t-shirt size as a medium project.

We all know that it’s no longer business as usual. We all have to make change for the well-being of the planets future. We believe that we can do this without compromising our living standards.. 

A reduced carbon footprint of 8 Tonnes per year is significant enough to make a difference. 


Conclusion

Although we are still far from Passive House certified performance (we’d need to get down to 15 kWh/m² & 0.6 ACH to achieve that) it is easy to see that there are clear benefits from undertaking a high performing extension, especially at this scale, which we would t-shirt size as a medium project.

Firstly there is the considerable cost savings for heating and cooling, well over $2000 a year. And while a payback period of 20 years seems quite long, the client would see an improvement in the comfort of their home from the day they move in. An investment in high performance construction is an investment in liability as much as anything else.

It is also worth keeping in mind that this study was undertaken without any consideration given to the existing heritage building, which is to be retained. This means that the analysis shown above only represents part of the total potential energy savings for the dwelling. In fact further savings could be made through improvements to the existing. That being said, an expected reduction in carbon footprint of 8 tonnes per year is still significant. We all know that it’s no longer business as usual and it is now time to make changes for the well-being of the plane.. We believe that we can do this without compromising our living standards.

Additional benefits from HP Building Method:

  • Indoor air quality, pollen and dust free

  • Comfortable year round climate (20-25C)

  • Balanced indoor temp (no hot or cold spots and draft free)

  • Extremely low energy bills

*Our software makes the following assumptions; a baseline airtightness of 10 ACH; a thermal comfort level of 20-25 degrees is maintained 24/7; energy supply cost of $0.30/kWh; assume all energy supply is via electricity and not gas.

**We are not builders or quantity surveyors, this is an estimate only

***Carbon emissions calculated as per Carbon Calculator













Negotiated Tender & Early Contractor Involvement (ECI)

Staying on top of costs and hitting our clients construction budget is of utmost importance. For most, it’s make or break.

As such, in most cases we have moved away from the traditional tender path, whereby we invite 2-3 builders to competitively price on a thorough and complete set of documents and hope that the tender price comes back on budget. As players in the custom-design market, ensuring the construction cost from the outset is becoming increasingly difficult. We don’t set construction costs, the construction industry, driven by supply and demand and ever increasing labour costs does.

A specialised residential custom-home builder can mitigate the risk of over design or over specification when involved in the project from an early stage. We believe that the collaborative approach with early contractor involvement will ensure we meet budget and a satisfactory outcome for all.

Our process is to recommend and/or interview (with our clients) to 2 to 3 builders early on in the project. We can either select builders that we’ve worked with before, who are already familiar with our documentation and detailing methods and whom have the technical ability to execute our design. Otherwise we are happy to provide recommendations for builders whom we’ve interviewed and are confident that they will be well suited for the project. When making recommendations, we also consider the personality types of each builder, and select builders that we feel both parties can have a successful working relationship with.

Be prepared to pay for a builders early involvement, as it’s their IP and experience that we’ve leveraged off to get this far. Most builders will deduct their fees from the tender figure should they win the job. If clients choose to go elsewhere then the builder is compensated for their time and expertise.

Depending on the nature of the project, we propose that builders have the opportunity to get involved at three key stages of the design and documentation process:

Feasibility/Sketch Design

As soon as we put pen to paper, ideas are flowing and we develop a concept and direction, collaborating with a builder to resolve the best approach to construction and lean on them to establish a budget.

Design Development

During this phase our builder can review the detailed design and make recommendations on construction methods and materials. By the end of this stage we will have a fully resolved concept and our builder can provide a more refined estimate taking into consideration the intricacies of the project.

Tender

Once we have compiled our extensive package of working drawings, specification and product selections, detailed interior design, structural engineering, energy rating; we will issue to the builder for formal quoting. This process is known as tendering. Based on our builders input to date there should be no surprises to the overall cost.

henry st construction.jpg