Sustainability - A way forward

We create best-practice high quality low energy Passive Solar Design as our benchmark minimum standard at Matt Day Architects.
We guide our clients through a unique step-by-step process to create homes that are highly connected to nature, for people who appreciate simplicity, craftsmanship and innovation.

And we love a challenge!

We strive to go further than Passive Solar Design, to create:
- Passivhaus Standard homes
- Off Grid homes
- Net Zero homes, and
- Carbon Positive homes
How do we achieve these outcomes?

With extensive expertise across varied climate zones and diverse geographic locations, we design homes that combine :
- low operational energy across the lifetime of the home
- reduced energy and costs for maintenance, whilst
enhancing durability
- low embodied carbon materials
- carefully-considered construction methods and timelines
- rainwater collection and storage for reuse, and water saving appliances and taps
- energy efficient appliances and lighting
- Passive Solar design as a minimum, or Passivhaus
Standard
- generating renewable energy onsite (combined with
battery storage where appropriate)

We have developed two tired-and-tested methods for reducing operational energy for alterations and additions and new builds. They are :

- a building that pursues best-practice Passive Solar design
or
- a building designed to the Passivhaus Standard.

We work with our clients from the very beginning of the project to determine the best method to pursue. We outline outline our definitions of Passive Solar design and Passivhaus Standard.
In addition, active systems are incorporated to reduce energy consumption even further.

We incorporate computer modelling for all projects to maximise performance and to minimise risks.

Passive Solar Design
- taking advantage of what’s freely available

Passive Solar Design is the minimum benchmark standard that we implement in all of our projects.
Passive Solar design involves designing a building that takes advantage of the resouces that are freely available - namely the sun and the wind - to light, heat and cool a building.
This approach limits the need to mechanically heat or cool your home, and reduces the need for artifical light during daytime hours.

Passive systems influence the plan layout and building form.

There are 5 guiding principles for best practice Passive Solar design

- orientation
- natural ventilation
- thermal mass
- glazing performance, and
- insulation and air tightness

A feature of our practice is creating light-filled, thermally comfortable spaces, that are a delight to inhabit all year round.

Orientation
Choosing the right orientation is the basis of good building design. We do this by orientating windows and doors to maximise direct sunlight during winter months.
In summer, carefullly positioned eaves and external shading devices prevent too much direct sunlight from entering and overheating overheating internal rooms.
This approach also ensures the home enjoys shaded outdoor living areas in summer and sun bathed outdoor living spaces in winter.

Living spaces are best orientated to the north, where possible, with bedrooms facing north or east, and service rooms facing west or south.
Each site has its own unique conditions and we take these into account - balancing solar optimisation against views and privacy - to achieve the best outcomes.

Natural Ventilation
We positioning appropriate windows, doors, louvres, clerestories and skylights to maximise and contro the flow of cooling breezes during summer months, using both cross-ventilation and convection ventilation (the chimney effect). Promoting natural ventilation enab les residents to night-purge the building of unwanted heat build-up in summer, and also provides year-round fresh air.

Thermal Mass
Thermal mass is about a material’s ability to absorb, retain, and radiate heat, and all materials - as well as air - absorb heat.
Heavyweight materials such as concrete, brick and rammed earth take longer to heat up and longer to cool down. This is often called thermal time lag.
Interior rooms constructed with high levels of thermal mass are cooler than rooms with materials that have less thermal mass.
In Passive Solar design, direct sunlight is encouraged to enter the building during the winter months to heat the rooms. Additional heat is absorbed by the thermal mass and released in the evening when the temperature outside cools, effectively operating as a natural heater.
Conversely, in summer the high thermal mass materials absorb unwanted internal heat during the day, keeping the rooms cool. And at night, convection ventilation is used to flush this unwanted heat out of the building.
Lightweight materials respond more rapidly to temperature changes.
Our designs strike a balance between thermal mass and lightweight materials to achieve optimal possible Passive Solar design.

Glazing Performance
Glass performs in two ways, by
- bringing daylight, and heat in winter, and
- opening out to views, and allowing heat to escape during summer.
We calibrate the volume, position and shading of glazing - in windows, doors, louvres, clerestories and skylights - to achieve successful Passive Solar design.
Glass is a great conductor of heat that offers few insulative properties, which means it is excellent at letting in, but equally good at letting heat out.
So glass must be positioned carefully to gain the most benefit from winter sun, whilst avoiding too much heat gain during summer.
The best method for this is adequate and appropriate shading and orientation.
Heat loss through glazing in winter at night can often lead to cold interiors and the need for additional mechanical heating, so we aim for a balance between heat gain and heat loss in winter.

As a rule of thumb maximising glazing to the north, with slightly less to the east and west, and minimal glazing to the south usually works best.
In addition double-glazing , and insulated glass are effective means for limiting heat loss during winter months.

Insulation and Air Tightness
There are two type of insulation : bulk and reflective.
Bulk insulation is used to slow down heat transfer and reflective insulation is used to deflect heat.
Both work in unison to limit internal heat loss during the winter months and reduce heat gain during summer months.
We use computer modelling to measure the best levels of insulation in floors, walls, ceilings and roofs.
Windows such as double-glazing are also a form of insulation, one which reduces heat loss substantially.
Air tightness refers to the amount of air that flows in or out through the building envelope, and it is measured as air changes per hour.
A typical 1980’s house can have as many as 16 air changes per hour. In winter, this means you are heating air that is being replaced 16 times per hour.
Conversely, Passivhaus Standard limits air changes to 0.6 per hour, which provides more stable indoor temperatures across the course of the day and throughout changing seasons,
A house with less than 3 air changes per hour is required to have mechanical ventilation.
When considering whether a building should be fully sealed or not, its not always the case that greater airtightness results in a better outcome for occupants.
Breathable building envelopes are important to control humidity and hidden moisture build-up, so we achieve an appropriate level of airtightness for the climate and occupants needs, whether we are aiming for Passive Solar design or Passivhaus Standard.

Active Systems

Active systems are devices that can be incorporated into the dwelling to either further reduce energy consumption, to supply renewable clean energy, and to recycle waste.

These include:

- Solar, wind powered, geothermal systems for generating power.
- Rainwater tanks to collect and store water for re-use.
- Greywater and blackwater treament purification systems
- Stormwater detention systems to reduce runoff
- Energy efficient lighting and appliances
- Water saving taps and appliances
- Heat pumps for hot water and underfloor heating

We weigh the initial upfront costs associated with the installation of these systems against their energy saving benfits over the buildings expected lifespan. Advances in technology often result in systems that had been previously cost prohibitive being cost effective.

Onsite power generation is essential for Off Grid, Net Zero, and Carbon Positive buildings.

Passivhaus Standard

A Passivhaus Standard design is an alternative approach to creating an extremely low energy house, that is comfortable and healthy all year round.
The internal temperatures are more stable (the standard usually aims for 20 - 24 degrees internally) and varies little across day or night, summer and winter. Such well sealed environments do require mechanical ventilation to ensure adequate fresh air. Maximum heating and cooling requirements need to be met to comply with the standard and these electrical loads translate to very little energy usuage.
This makes achieving Net Zero and Carbon Positive houses a lot easier than via Passive Solar design methods.
A Passivhaus is often referred to as ‘Passive House’, and these shouldnt be mistaken for ‘Passive Solar House.’
Passivehaus Standard designs take a ‘fabric first’ approach, where the focus is on optimising the layer of the house that is between the outside and the inside, also known as the ‘thermal envelope’
First and foremost Passivhaus Standard designs are exceptionally well sealed; the ISO standard requires no more than 0.6 air changes per hour. This is referred to as an airtightness level.
Higher levels of airtightness (ie. fewer air changes per hour) means there is less heated air escaping the building, which reduces the amount of air that needs to be heated in winter. In summer, less heat enters the building, thereby rducing the need to cool internal air.

There are 7 guiding principles for best practice Passivhaus design

- orientation based off Passive Solar design principles
- air tight thermal envelope (0.6 or less air changes per hour)
- high performance windows
- mitigating thermal bridging
- appropriate levels of insulation
- mechanical heat recovery ventilation unit
- compact form (oftern referred to as ‘form factor’)

Passivhaus is modelled using the Passive House Planning Package. This package contains benchmarks for thermal performance that must be met in order for the house to be certified Passivhaus Standard.

The mechanically controlled internal air environment makes it very suitable for people who have allergies, or who are susceptible to dust and noise, and bugs.

Our Kazahana Ski Lodge project is the first Passivhaus Standard building designed by Matt Day Architects. This project posed addiitonal challenges arising from its location in Japan, where it is subject to winter temperatures as low as - 20 degrees Celsius. For more about this project see here

Material Choice

We select materials based on several key factors, including the energy consumption required to produce the material, thermal performance properties, longevity, and renewability.

Recycled materials - or materials that can be recycled in the future - have the lowest overall energy consumption to produce, and the greatest longevity.

Our guiding principles for choosing materials are

- what does the material need to do?
- can the material achieve more than one function?
- does the material come from a renewable source?
- is the process for manufacturing the material based on use renewable energy sources?
- can the material be recycled? What is its longevity and durability ?
- is the material healthy , low VOC, natural, raw? What about the safety data?
- is the material locally grown / harvested / produced?
- is the material a recycled material?
- are there any existing materials in the building that can be re-used?

Buildability

The act of building involves a great deal of energy consumption.
Transportation of materials contributes significantly to the overall energy consumed in building. We aim to reduce the number of deliveries, the amount of material and the amount of waste generated on our building sites.
We do this by specifying locally produced materials, typical construction methods, and local labour. We also incorporate modular systems based on supplier standard sizing to reduce off cuts and waste, while elevated floor plates and pad footings reduce soil disturbance.

We opt for sustainable, low-impact materials that are:
- Non-toxic
- Recycled and recyclable
- Renewable
- Local
- Available in standard sizes, or modular, or pre-cut
- FSC-certified wood
- Durable and long-lasting

Modular systems

Modular systems - based on supplier standard sizing - offer a wide range of benefits. Modular construction can reduce off-cuts, while elevated floor plates and pad footings can reduce soil disturbance. Modular construction can also be 30-50% quicker than traditional construction with the added benefit of avoiding weather delays.

Flexibility can be achieved through modular design throughout the design process with extra space and budget constraints easily factored into the process. Off-site construction using modular systems also means increased construction quality management and fewer disruptions.