Insulation (Leaving Cert Construction Studies): Revision Notes

Insulation

Understanding heat loss in buildings

Heat loss is a major problem that significantly affects the cost of heating homes, offices and other buildings. When oil and energy prices continue to rise, preventing heat from escaping becomes crucial for economic and environmental reasons.

Research shows that heat escapes from buildings through different pathways in predictable patterns. The largest heat loss occurs through general ventilation, which accounts for 35% of total heat loss. The roof is responsible for 25% of heat loss, making it the second largest source. Walls and floors each contribute 15% to heat loss, whilst windows account for 10%. Understanding these percentages helps builders and homeowners prioritise where to focus their insulation efforts.

The build-up of heat and moisture in buildings also creates condensation problems. This makes proper insulation and ventilation systems essential for maintaining comfortable, healthy living conditions.

What is insulation and why is it important

Insulation works by preventing heat from being lost through the building fabric. It consists of high-density materials that do not allow heat to pass easily through them. This creates a barrier that keeps warm air inside during winter and helps maintain comfortable temperatures year-round.

The primary purpose of insulation is to reduce the amount of energy required to maintain comfortable temperatures in buildings. This directly translates to lower heating bills and reduced environmental impact from energy consumption.

Evolution of insulation standards

Building insulation requirements have changed dramatically over the decades as understanding of energy efficiency has improved.

In the 1970s, builders had limited knowledge about the value of insulation, so it was not commonly installed in cavity walls of new buildings. This meant many homes from this era have poor thermal performance.

During the 1980s and 1990s, regulations began requiring insulation with a thickness of 50mm to be installed against the inner leaf of cavity walls. By the early 2000s, this thickness had increased to 60mm as standards became more demanding.

Currently, regulations require a minimum of 100mm of insulation within cavity walls for standard construction. For passive houses, which aim for extremely high energy efficiency, insulation thicknesses can reach 200mm. This progression shows how building standards have evolved to create more energy-efficient homes.

The comparison between current insulation standards and passive house requirements demonstrates significant differences in U-values (heat transfer rates). Passive houses require much lower U-values, meaning better insulation performance across all building elements including roofs, windows, walls and floors.

Proper insulation placement techniques

Effective insulation requires careful placement in multiple locations throughout a building. The goal is to create a continuous thermal envelope that surrounds the entire heated space.

Wall insulation

Cavity wall insulation is placed vertically inside the cavity along the inner leaf of the cavity wall. This insulation layer is held securely in place using wall ties, which connect the inner and outer leaves of the wall whilst maintaining the insulation's effectiveness.

Floor insulation

For ground floors, insulation is placed horizontally under the floor slab. When suspended floors are used as the ground floor, insulation is positioned between the joists and secured using netting or timber battens to prevent it from sagging or moving out of position.

Attic and roof insulation

The attic space requires particular attention because significant heat loss occurs through the roof area. Double-layered insulation is often used in attics, with the second layer laid perpendicular to the first. This cross-laying technique closes any gaps that might exist in the first layer, creating a more complete thermal barrier.

Understanding thermal bridging

Thermal bridging, also known as cold bridging, represents areas where heat can transfer directly from inside the building to the outside without passing through insulation. These thermal bridges create weak points in the building's thermal envelope and can lead to condensation problems.

Common locations for thermal bridging include areas where structural elements pass through the insulation layer. Without proper treatment, these bridges allow heat to flow along continuous materials like concrete or steel, bypassing the insulation entirely.

Preventing cold bridges

Modern construction techniques focus on eliminating thermal bridges through careful design and insulation placement. Key strategies include:

• Installing insulation at window and door jambs to prevent heat transfer around openings
• Using insulated lintels over windows and doors
• Placing insulation behind cills and other horizontal elements
• Ensuring continuous insulation coverage around structural connections

Vertical insulation around floor slabs prevents heat transfer between the external building layers and the internal floor structure. This technique is particularly important where concrete floors meet external walls.

Key insulation locations throughout buildings

Comprehensive insulation coverage requires attention to multiple building areas beyond just walls and roofs.

Structural elements

Ceiling joists and floor joists require insulation to prevent heat loss through these structural pathways. These timber elements can create thermal bridges if not properly addressed during construction.

Internal partitions

Internal partition walls are not always insulated, but when thermal performance is important, insulation can be fitted before the wall is covered with plasterboard. This approach is particularly useful for walls separating heated and unheated spaces.

Service installations

Pipework and other building services need insulation protection for two reasons: to protect against cold temperatures that could cause freezing, and to retain heat within distribution systems. Proper insulation of pipes, ducts and other services prevents energy losses and maintains system efficiency.

Around service penetrations through walls and floors, special attention prevents air gaps that could compromise the thermal envelope. These areas often require custom insulation solutions to maintain continuity around pipes, cables and other building services.

Attic spaces

Attic insulation deserves special consideration because substantial heat loss occurs through roof areas. The materials used here are typically laid between and across ceiling joists, creating multiple layers for maximum thermal protection.