Insulation Performance and Improvements (Leaving Cert Construction Studies): Revision Notes
Insulation performance and improvements
Improving thermal properties of existing houses
Due to rising energy costs, enhancing the thermal performance of homes has become essential for many homeowners. There are several effective approaches to achieve this improvement.
Modern insulation retrofitting can significantly reduce energy bills while improving comfort levels throughout the home, making it one of the most cost-effective home improvements available.
Cavity wall insulation methods
The most popular method for retrofitting existing properties involves increasing wall insulation. This can be accomplished through two main approaches:
Filling existing cavities When a cavity wall already exists, insulation material can be injected or blown into the space between the inner and outer walls. This method utilises the existing wall structure whilst significantly improving thermal performance.
Adding new insulation layers Where cavity walls don't exist or additional insulation is required, new insulation layers can be added to the external or internal surfaces of walls.
External wall insulation (EWI)
External wall insulation has become a preferred choice because it enhances the building's thermal properties without affecting internal room dimensions. The installation process involves several key steps:
Installation Process for External Wall Insulation
Step 1: Preparation
- Position starter board at damp-proof course (DPC) level
- Ensure walls are clean and dry for proper bonding
Step 2: Insulation Installation
- Fix insulation material (typically polystyrene) using chemical adhesive and mechanical fixings
- Maintain continuous coverage to prevent thermal bridges
Step 3: Finishing
- Apply special mesh render system
- Complete three coats of render followed by weatherproof paint
Materials used for EWI Common materials include mineral wool, polystyrene and wood fibre, each offering different thermal and practical properties.
Addressing building features To maintain insulation effectiveness, all breaks in the wall must be properly managed:
- Window and door cills are removed and replaced after rendering
- Pipework and cables are lengthened to accommodate the additional wall thickness
- Any gaps in the insulation are filled with expanding foam to prevent cold spots
The entire surface is rendered using a special mesh that allows the render to move slightly without cracking. This flexibility is crucial for preventing long-term structural issues and maintaining the weatherproof barrier.
Problems with ineffective insulation
Poor installation or insulation failure can create significant problems within the building structure, often causing more issues than having no insulation at all.
Critical Warning: Poorly installed insulation can trap moisture, create structural damage, and actually increase energy costs rather than reducing them. Professional installation and quality materials are essential.
Condensation and moisture problems
Surface condensation Condensation occurs when moist, warm air contacts a colder surface, or when air temperature drops below the dew point. This leads to water formation that can cause rot and mould growth.
Interstitial condensation This more serious problem happens within building materials rather than on their surfaces. When warm, moist air travels through building fabric and cools to dew point whilst still inside the material, condensation forms within the structure itself. This creates structural defects and renders insulation ineffective.
Interstitial condensation also occurs when rigid insulation becomes detached from the wall, creating a cold surface behind the insulation material. This detachment is often invisible from the interior but can cause significant damage over time.
Prevention methods
Vapour barriers Interstitial condensation can be prevented by installing a polythene sheet on the warm side of the insulation, typically on the inner surface of the wall next to the plasterboard. Alternatively, foil-backed plasterboard can be used. These measures prevent warm, moist air from passing through the wall structure.
The key principle is to stop moisture-laden air from reaching the cold surface where it would condense. Proper vapour barrier placement is critical - it must always be on the warm side of the insulation to be effective.
Thermal looping
Thermal looping significantly reduces insulation effectiveness and increases energy requirements. This problem occurs when air is allowed to circulate between the inner leaf of a cavity wall and the insulation within that cavity.
How thermal looping develops The circulation typically results from:
- Dropped mortar creating gaps
- Insufficient use of wall ties
- Poor installation practices
Impact on performance The air circulation draws heat from the inner leaf of the wall, substantially increasing the building's energy requirements and reducing the insulation's effectiveness.
Prevention is Key: Proper installation techniques and ensuring complete filling of cavities helps prevent thermal looping from occurring. Once established, thermal looping can reduce insulation effectiveness by up to 50%.
Summary
Key Points to Remember:
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Two main retrofit methods: Cavity filling and external wall insulation (EWI) are the primary approaches for improving existing building thermal performance
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EWI advantages: External insulation maintains internal room dimensions whilst significantly improving thermal properties through continuous insulation layers
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Moisture control is critical: Interstitial condensation within building fabric causes more damage than surface condensation and must be prevented using vapour barriers
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Proper installation prevents problems: Poor installation creates thermal bridges, condensation issues and thermal looping that can make insulation ineffective
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Continuous insulation matters: Any gaps, cold spots or air circulation paths significantly reduce overall insulation performance and increase energy consumption