Glossary

TERM DEFINITION
Air-sealing

The method of creating an airtight building envelope in order to separate a comfortable indoor environment from any external extremes.

ACH

ACH stands for Air Changes per Hour.
It is a commonly used unit of measure with regard to building airtightness.
One air change is the total volume of a building's internal space.

For example: if a building's internal volume is 500m3 and a test indicates 1,000m3 of infiltration air leakage in an hour. It would be said to have an airtightness of 2 air changes per hour (2 ACH). Meaning that the space is losing two times its internal volume worth of air every hour.

Blower Door Testing (BDT)

A Blower Door Test is a method used to identify and quantify air leakages in a building envelope.
In short, it measures building airtightness.

Centralised (Ducted) Unit

Centralised (Ducted) ERV systems consist of a single unit which moves large volumes of air throughout the building from a single main unit. The necessity of ducting for the air flow makes these systems most appropriate for new houses or existing houses with adequate space available in the roof or floor cavities for duct installation.

Decentralised (Non-Ducted) Unit

Decentralised (Non-Ducted) ERV systems are standalone units which provide high-efficiency and quiet operation. As these units require no ducting, they are ideal for retrofit installation into existing buildings, particularly when there is insufficient space to install a complex ducting system or large centralised unit.

Dew-Point Analysis and Modelling

The computational process used for regulating the point at which condensation is expected to occur within a building environment.
This process ensures that condensation does not occur within the building fabric, and avoids the resulting structural damages such as mould and rot.

Energy Recovery Ventilation (ERV)

Energy Recovery Ventilation (ERV) units are able to exchange both sensible heat (Temperature) and latent heat (Moisture). The ability to regulate moisture as well as temperature makes ERV systems better at maintaining higher levels of air quality than the less advanced Heat Recovery Ventilation (HRV) systems which are only capable of regulating temperature.

Fluid Dynamic Modelling

The computational process of designing, simulating and evaluating fluid flow problems and solutions.Namely, the process we use to design the perfect ventilation system for your building.

Heat Recovery Ventilation (HRV)

Heat Recovery Ventilation (HRV) units recover sensible heat i.e. Temperature from hot or cold air and uses it to preheat or precool air which improves energy efficiency.

Moisture Vapour Transmission Rate (MVTR)

MVTR is a measure of a materials resistance to water vapour diffusion.It is measured in MNs/g.Efficacy:In general, the LOWER the MVTR value, the LOWER the resistance to water vapour transmission.A low MVTR value indicates a material that readily allows the passage of water vapour.

R-value

An R-value is a measure of a material's thermal resistance.It is measured in m2K/W.Efficacy:In general, the HIGHER the R-value, the HIGHER the level of thermal resistance, and the less heat will be transferred through the material.Note: Generally, an R-value is the inverse of the U-value (R=1/U)

Structural Thermo-breaking

Structural Thermo-breaking refers to the elimination of thermal bridges in structural connections.
(It is important to note that in reality the term elimination refers to a massive reduction, as complete elimination would be physically impossible!)

SHGC (Solar Heat Gain Coefficient)

The measure of how much energy (specifically solar heat) from the sun passes through a window.

Efficacy:
In Australia's hot climate regions, lower SHGC values are preferred when no external shading is available. However, this also reduces the amount of visual light passing through the window.
In cooler climates, windows which have a high SHGC allow a greater amount of solar heat to pass through, offering much appreciated solar heating for the home. Low-E coatings are very important in keeping the warmth indoors.

Solar Heat Gain Control

Solar Heat Gain Control refers to various methods of regulating the incoming solar heat from the sun.
Methods include fixed and passive shading, as well as building orientation.

Thermal Bridge

The term thermal bridge is used to refer to any structure, design or material that acts as a conductor of heat between two different temperature differentials (usually, between the inside of a building's thermal envelope to the outside).Common examples include: - a concrete slab with a cantilever balcony (where the slab acts as thermal bridge - or a thermodynamic fin) - a steel I-beam that passes through the thermal envelope.

Thermal Envelope

The thermal envelope is the boundary between the regulated living space and the external environment (for insulation and airtightness purposes).

Note: the thermal envelope often differs to the external building envelope.
For example, an adjoining garage or basement sits inside the building envelope, but if the designer so chooses, may be outside of the thermal envelope (as it does not require regulated heating/cooling/humidity control).

Thermal Break or Thermal Barrier

An element or point of low thermal conductivity, which massively reduces the flow of thermal energy between conductive materials.

U-value

The U-value is the overall heat transfer coefficient, and is a measure of the rate of heat transfer through a material.
It is measured in W/m2K.

Efficacy:
In general, the LOWER the number, the LOWER the amount of total heat transfer.
Uf is commonly used to refer to a window frame.
Ug is commonly used to refer to a glazing unit.
Uw is commonly used to refer to a window unit (glazing and frame combined).

Note: Generally, a U-value is the inverse of the R-value (U=1/R).