Thermal Performance
The thermal performance of a home is dictated to by what happens at a construction phase. With innovative processes and advanced construction methodology we have a concentrated focus on optimizing thermal performance during the build process; creating a comfortable, sustainable living environment.
Fully Insulated Concrete Foundation
Outside cold can easily travel through a traditional concrete foundation, creating uncomfortable cold spots within the home. This is due to the foundation having no thermal break between its external edges and the natural elements.
A fully insulated foundation provides a complete thermal break between the foundation and the ground below, and around it. This helps retain heat within the home and therefore leads to a higher temperature at the junction point where wall and slab meet, allowing for a more consistent thermal performance across the foundation. Our preferred product is to use a MAXSlab insulated concrete foundation, which is designed and engineered specifically for each individual home to ensure that different environments and climates are considered. An insulated foundation surpass’ all New Zealand Building Code requirements, achieving R-values of R4.0 and above.
Framing Construction Details
Insulation effectiveness is compromised by thermal bridging where heat escapes through materials that conduct heat more easily – timber is one of those materials. As the amount of timber framing within the wall increases, less space is available for insulation.
We use the following solutions to help create a higher performing wall cavity:
The wall framing thickness is 140mm in depth, and there is no requirement for any horizontal timber components (dwangs) to be used; allowing more space for insulation.
Our preferred corner construction details allow for insulation to be installed to the exterior perimeter of the building envelope. This provides the opportunity for a near continuous layer of insulation within the wall cavity.
With additional space in the wall cavity this naturally allows for more insulation to be installed, thus achieving a higher R-value – to a maximum of R4.3. In conjunction with our airtight membrane and service cavity system, we also achieve an additional R1.2 insulation property on the inside of our membrane – taking the total finished wall cavity thickness to 185mm and the total potential wall insulation to R5.5.
Airtight Membrane
As a home is heated or cooled from the inside, the intention is to limit the ability of this energy to escape, ultimately retaining it. Traditional construction methods allow for the home to empty and refill with air on a regular basis (known as Air Changes), meaning energy is not retained for long periods of time.
An airtight membrane is an innovative solution that is applied to the inside of the external frame creating a seal around the entire building envelope (ceiling included), helping eliminate unwanted draughts and retaining heating and cooling within the home for longer. In conjunction with this, the use of a service cavity on the face of the membrane, means there are limited penetrations to the airtight layer and the air changes are further reduced. Once installed, an airtight membrane has a significant impact on the energy retention within the home, which also means there is a requirement for mechanical ventilation to ensure the air retained is kept fresh and healthy.
Our process involves air permeability (blower door) tests to be conducted to measure the air leakage (infiltration and exfiltration) of the home during the construction phase. With Air Changes per Hour (ACH) readings below 1.5ACH, the performance of the home in retaining energy is far superior.
Exterior Joinery
When the outside temperature is cold but its warm inside, most traditional New Zealand homes will find condensation on the inside of their windows. This is due to a number of components (some covered previously around our construction methods), but primarily it is a result of the exterior joinery and glazing that is used.
In comparison to wall framing, which has very minimal thermal bridging and a large capacity for insulation, exterior joinery units and glass are the areas where homes leak the most energy. Using an exterior joinery unit with a thermal break, in conjunction with a Low Emissivity (LowE) glazing option, increases the performance of the homes windows and doors.
We have two preferences; the first being Thermally Broken Aluminium joinery units – these have an insulated strip inserted into the aluminium frame creating a thermal break which reduces the temperature changes between the inside and outside of the home.
Secondly, uPVC (unplasticised Polyvinylchloride) joinery units – these are a highly resilient plastic product which combined with an internal air chamber technology, prevents heat or cold from travelling through the frame. In conjunction with these exterior joinery options, we also use a LowE high performance glass which further increases the insulation rating of the exterior joinery units – in most cases, these result in R-values upwards of four to five times that of conventional building (dependent on unit and glass selection).
Both of these options, in conjunction with our other high performing practices, help to retain heating and cooling within the home, whilst also removing condensation from forming on the inside of the joinery; resulting in a drier, healthier home.
VENTILATION AND MOISTURE CONTROL
High performing homes aim to retain as much energy as possible; however, there is a risk of internal air becoming musty or moisture being trapped in the building envelope. Introducing a positively balanced mechanical ventilation system helps us ensure the removal of any generated moisture, as well as reticulation of fresh air and temperature control; resulting in a healthier and drier home.
Mechanical Ventilation
Traditional construction methods allow for a home to naturally ventilate, as its primary focus is not on energy retention. However, once an airtight membrane is installed within a high performing home and a low ACH reading is achieved, there is a requirement for ventilation and moisture control to ensure air quality is optimized.
There are a number of positively balanced mechanical ventilation systems available, and each home has differing requirements. With options available to not only ventilate and moisture control, but to also temperature and zone control within the home, the right fit is hugely important. The system best suited to each individual build is specially designed to meet the requirements of the home, ensuring a healthier, more comfortable living environment.
SUSTAINABILITY
High performing homes have a fundamental ethos of allowing energy naturally generated to be utilized in its maximum capacity. Ultimately ensuring the home requires less additional energy inputs, making it a more self-sustainable living environment. Not only do we ensure the final product is sustainable, but also that the environmental impact across the construction phase is limited as well.
A Sustainable Future
The world is rapidly moving to a stage where we are all accountable for the longevity of where it is we live and the ability to hand over a sustainable future to the next generations. The construction industry has its part to play and high performing homes are part of that conversation.
Construction methods that limit the environmental impacts of a building project are a great way to contribute at a ground level stage. The selective use of materials and products that are less harmful to the environment, as well as an accountability for the amount of refuse generated across a build, are all areas that can be controlled from a construction perspective.