Building science and performance

32 terms in building science and performance

Thermal performance

Thermal performance is how well a home resists unwanted heat flow, keeping it comfortable with less heating and cooling. It is what the energy efficiency provisions of the National Construction Code and schemes such as BASIX and NatHERS set out to measure and require, and it is built from the insulation, glazing, orientation and sealing of the home together. BASIX and energy efficiency reference. See also: NatHERS.

R-value

R-value measures how well a material or building element resists heat flow, with a higher value meaning more resistance. Insulation is specified by R-value, and the values a home must achieve are set by the energy efficiency requirements, so confirm the current requirements with the relevant source. General information, not compliance advice. BASIX and energy efficiency reference. See also: U-value.

U-value

U-value measures how readily heat flows through a building element such as a window, the inverse idea to R-value, with a lower value meaning better performance. Windows are commonly rated by U-value together with their solar heat gain, and the required values are set by the energy provisions, so confirm the current requirements with the relevant source. General information, not compliance advice. BASIX and energy efficiency reference. See also: R-value.

Thermal bridging

Thermal bridging is heat flowing through a conductive path that bypasses the insulation, such as a metal frame or a slab edge, undercutting the performance the insulation was meant to give. Managing it is part of designing a home to actually reach its rated thermal performance rather than only on paper. BASIX and energy efficiency reference. See also: Thermal performance.

Thermal mass

Thermal mass is the capacity of heavy materials such as concrete and masonry to absorb, store and release heat slowly, smoothing temperature swings through the day. Used well with orientation and shading it improves comfort, and used poorly it can work against a home, which is why it is a design decision rather than a default. BASIX and energy efficiency reference. See also: Thermal performance.

Bulk insulation

Bulk insulation resists heat flow through the still air trapped in its fibres or cells, such as batts in walls and ceilings, and is rated by R-value. It works whichever way the heat is moving, in contrast to reflective insulation, and installing it without gaps or compression is what lets it deliver its rated value. BASIX and energy efficiency reference. See also: Reflective insulation.

Reflective insulation

Reflective insulation resists radiant heat with a reflective surface, such as a foil facing, and needs an adjacent air gap to work. It is often used with bulk insulation and sarking rather than instead of them, and it must face the right way and stay clean to perform. General information, not compliance advice. BASIX and energy efficiency reference. See also: Bulk insulation.

Sarking

Sarking is a pliable membrane laid under the roof covering or behind cladding that helps shed water, manage condensation and, where it is reflective, reduce radiant heat. Which type is used and where depends on the climate and the assembly, and it works alongside the insulation rather than replacing it.

Vapour permeable membrane

A vapour permeable membrane is a wrap that resists liquid water from outside while letting water vapour escape from within the wall, helping manage condensation in the building fabric. Its correct use has become more important as homes are built more airtight, and the right membrane depends on the climate and the wall build-up. General information, not compliance advice. See also: Condensation management.

Condensation management

Condensation management is designing and building a home so moisture does not accumulate inside walls, roofs and other elements, where it can cause mould and decay. It has become a distinct concern as homes are sealed more tightly for energy performance, and the National Construction Code now addresses it, so confirm the current requirements with the relevant source. General information, not compliance advice. See also: Vapour permeable membrane.

Air tightness

Air tightness is how well a home resists uncontrolled air leaking in and out through gaps in the fabric. Reducing leakage improves comfort and energy performance, but a tighter home also needs deliberate ventilation and condensation control, so the three are designed together rather than in isolation. BASIX and energy efficiency reference. See also: Condensation management.

Whole-of-home rating

A whole-of-home rating assesses a home’s overall energy use across its major equipment, heating, cooling, hot water and the like, alongside the thermal performance of the building fabric. It is part of how the energy provisions have moved beyond the fabric alone, and the current settings and thresholds should be confirmed with the relevant source. General information, not compliance advice. BASIX and energy efficiency reference. See also: NatHERS.

Site classification

A site classification grades a building site by how reactive its soil is to moisture change, which drives the footing and slab design. The Australian standard for residential slabs and footings uses classes from stable through to problem sites, and the classification comes from a soil investigation, so confirm it against the current standard and a qualified engineer. General information, not engineering advice. See also: Reactive soil.

Reactive soil

Reactive soil is ground that shrinks and swells significantly as its moisture changes, moving the footings it supports and, if not designed for, cracking the structure above. The more reactive the site, the more substantial and expensive the required footing system, which is why the site classification belongs in the feasibility. General information, not engineering advice. See also: Site classification.

Wind classification

A wind classification grades the wind a building must be designed and braced to withstand, running through a set of non-cyclonic and cyclonic categories under the relevant Australian standard. The classification depends on region, terrain, shielding and topography, and it drives tie-down and bracing, so confirm it against the current standard. General information, not engineering advice. See also: Site classification.

Ember attack

Ember attack is the shower of burning debris a bushfire drives ahead of and around itself, a leading cause of homes igniting. It is one of the exposures a Bushfire Attack Level accounts for, and lower BAL construction focuses heavily on sealing gaps and screening openings against embers. General information, not compliance advice. Bushfire and BAL reference. See also: Bushfire Attack Level.

Radiant heat flux

Radiant heat flux is the intensity of heat a building would receive from a bushfire, measured in kilowatts per square metre, and it is the basis on which the higher Bushfire Attack Levels are set. The higher the exposure, the more demanding the construction required, and the assessed figures come from the bushfire standard. General information, not compliance advice. Bushfire and BAL reference. See also: Bushfire Attack Level.

Flame Zone(BAL-FZ)

Flame Zone, written BAL-FZ, is the highest Bushfire Attack Level, where a building could be exposed to direct flame contact as well as extreme radiant heat and ember attack. It carries the most demanding and costly construction requirements of any BAL, which is why the rating is confirmed early against the bushfire standard. General information, not compliance advice. Bushfire and BAL reference. See also: BAL construction levels.

BAL construction levels

The BAL construction levels are the graded categories the bushfire standard assigns a site, running from BAL-LOW through BAL-12.5, BAL-19, BAL-29 and BAL-40 to BAL-FZ, each mapping to progressively more demanding construction. The level for a site comes from a bushfire assessment, so confirm it and its requirements against the current standard. General information, not compliance advice. Bushfire and BAL reference. See also: Bushfire Attack Level, AS 3959.

Waterproofing

Waterproofing is the system of membranes, falls and detailing that stops water penetrating wet areas, balconies, roofs and below-ground elements. It is a leading source of defects when done poorly because it is concealed and hard to fix later, which is why it is a hold point and is built to the relevant Australian standard. General information, not compliance advice. Quality assurance reference. See also: Wet area.

Wet area

A wet area is a part of a home designed to be subject to water, such as a bathroom, laundry or kitchen, with specific waterproofing and finish requirements. The falls, membranes and junctions in a wet area are built to the relevant standard, and the inspection of them is a common hold point. General information, not compliance advice. Quality assurance reference. See also: Waterproofing.

Termite management

Termite management is the system that protects a home from subterranean termites, through physical barriers, chemical treatments or a combination, together with a durable notice recording what was installed. It is required in many areas to the relevant Australian standard, and the approach depends on the site and the construction, so confirm the current requirements. General information, not compliance advice. See also: Termite barrier.

Termite barrier

A termite barrier is the specific physical or chemical protection installed to deter or detect termites reaching a building, part of a termite management system. Barriers need maintaining and periodic inspection to keep working, which is why a durable notice records what was installed and what upkeep it needs. General information, not compliance advice. See also: Termite management.

Damp proof course(DPC)

A damp proof course is a barrier built into masonry to stop moisture rising or crossing from one part of the construction to another. Placed correctly it keeps damp out of walls and floors, and a bridged or missing damp proof course is a common cause of rising damp problems later. See also: Weep holes.

Weep holes

Weep holes are the deliberate gaps left in the outer leaf of masonry to let water that gets into the cavity drain out and the cavity breathe. Blocking or rendering over them traps moisture in the wall, which is why they are kept clear even though they look like missing mortar. See also: Damp proof course.

Subfloor ventilation

Subfloor ventilation is the airflow provided beneath a suspended floor to keep the space dry and prevent moisture damaging the structure above. Adequate cross-flow through vents is what stops a damp, poorly ventilated subfloor becoming a source of decay and mould. See also: Suspended slab.

Articulation joint

An articulation joint is a deliberate vertical joint in masonry that lets a wall move with the small foundation movements of a reactive site without cracking randomly. Placing articulation joints is part of designing masonry for the site classification, so the movement goes where it is allowed for rather than through the wall. General information, not engineering advice. See also: Reactive soil.

Acoustic rating

An acoustic rating measures how well a building element resists the transmission of sound, used for separating walls and floors between dwellings. The ratings required between attached homes are set by the National Construction Code, so confirm the current requirements with the relevant source. General information, not compliance advice. See also: Fire separation.

Fire resistance level(FRL)

A fire resistance level expresses how long a building element withstands fire against structural adequacy, integrity and insulation, written as three periods in minutes. Which elements need an FRL, and what it must be, is set by the National Construction Code from the building’s class and layout, so confirm the current requirements. General information, not compliance advice. See also: Fire separation.

Fire separation

Fire separation is construction that resists the spread of fire between parts of a building or between attached homes, such as a fire-rated separating wall between townhouses. The requirements come from the National Construction Code and depend on the building’s class and layout, so confirm the current requirements with the relevant source. General information, not compliance advice. See also: Fire resistance level.

Livable housing design

Livable housing design is building homes that are easier for people of all ages and abilities to enter, move around and live in, through features such as step-free access, wider doorways and reinforced bathroom walls. Accessibility provisions for new homes have been introduced through the National Construction Code, so confirm the current requirements and their adoption in the relevant state. General information, not compliance advice. See also: Building classification.

Respirable crystalline silica

Respirable crystalline silica is the fine dust released when cutting or grinding materials such as concrete, brick, stone and tiles, which can cause serious lung disease when inhaled. It is a significant work health and safety hazard on building sites with strict controls, and the current rules should be confirmed with the relevant regulator. General information, not safety advice. Site safety feature. See also: Safe Work Method Statement.