Photo AI
A dwelling house built 40 years ago, as shown in the sketch, has a 300 mm external concrete block wall with a 100 mm un-insulated cavity - Leaving Cert Construction Studies - Question 2 - 2011
Question 2
A dwelling house built 40 years ago, as shown in the sketch, has a 300 mm external concrete block wall with a 100 mm un-insulated cavity. The owner intends to refurb... show full transcript
Worked Solution & Example Answer:A dwelling house built 40 years ago, as shown in the sketch, has a 300 mm external concrete block wall with a 100 mm un-insulated cavity - Leaving Cert Construction Studies - Question 2 - 2011
Step 1
Injecting insulation into the cavity of the external wall
Answer
- Drilling the Holes: Holes of 22 mm diameter are drilled through the external leaf, typically spaced at 800 mm horizontally and at 1350 mm vertically.
- Additional Holes: Additional holes are drilled beneath window cills and above window and door heads to ensure proper filling of the cavity.
- Injecting the Insulation: Insulation material, usually a type of polystyrene or cellulose, is pumped into the cavity through the drilled holes.
- Coating for Strong Adhesion: Ensure a light coating of strong glue is applied to facilitate adherence of the insulation to the cavity walls.
- Finishing: As the injection completes, it is ensured that the new insulation binds well with the existing wall finish.
- Material Specification: The typical insulation material used includes polystyrene or cellulose.
Step 2
Fixing an internal insulation system to the external wall
Answer
- Material Preparation: The internal insulation consists of softwood battens sized 50 mm x 50 mm fixed to the insulation side of the wall.
- Spacing: Battens are spaced 400 mm apart.
- Insulation Placement: Insulation material such as fibreglass or polystyrene is placed between the battens.
- Vapour Barrier Installation: A vapour barrier may be included on the warm side of the insulation to prevent moisture accumulation.
- Plasterboard Fixation: A 12 mm thick plasterboard is fixed directly to battens.
- Finishing Touch: A skim coat of plaster is then applied, completing the internal insulation process.
Step 3
Discuss one advantage and one disadvantage of injecting the insulation
Answer
Advantage: Injecting insulation substantially reduces heat loss, resulting in a warmer house with decreased energy bills and better U-values. Disadvantage: The cavity is fully bridged, which may create complications in exposed sites, such as potential dampness and cold spots.
Step 4
Discuss one advantage and one disadvantage of internal insulation
Answer
Advantage: Internal insulation effectively improves the U-value of the external wall and allows for aesthetic adaptations, such as re-painting the surfaces to the owner's preference. Disadvantage: One major drawback is that it reduces the floor area of the rooms, which may lead to spatial constraints.