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It is proposed to design the external envelope of a dwelling house to be thermal bridge free - Leaving Cert Construction Studies - Question 9 - 2015
Question 9
It is proposed to design the external envelope of a dwelling house to be thermal bridge free. The drawing shows an outline section through a two-storey house having ... show full transcript
Worked Solution & Example Answer:It is proposed to design the external envelope of a dwelling house to be thermal bridge free - Leaving Cert Construction Studies - Question 9 - 2015
Step 1
Select any three locations from those circled on the drawing and, using notes and freehand sketches, show best practice design detailing that will prevent the formation of a thermal bridge at each location selected.
Answer
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Head of Window Opening:
- Use 250mm full-fill cavity insulation around the window to enhance thermal performance.
- Ensure the window frame allows for a 25mm external lintel to wrap around the window, preventing heat loss through the window reveal.
- The intersection between the window and wall must be treated with care to prevent thermal bridging, utilizing air-tight seals and proper insulation placement.
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Ground Floors Abutting External Walls:
- Integrate 100mm of insulation between the floor slab and the external wall.
- Use a continuous insulation strategy between the floor and subfloor to avoid heat loss under the ground level.
- Ensure that the insulation extends at least 300mm to counteract thermal bridging effectively.
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Junction of Upper Floors and External Walls:
- Install insulation on the inside of the wall to allow for no penetration of lead or cavity, maximizing airtightness.
- Reinforce the ceiling structure by using resilient channels or similar techniques to provide continuity of insulation and reduce sound transmission.
- Ensure that joists do not bridge the insulation layer and are thoroughly insulated around their surfaces.
Freehand sketches should depict the insulation details at these junctions to illustrate the prevention of thermal bridging.
Step 2
Discuss the importance of designing a building envelope that is thermal bridge free.
Answer
The design of a thermal bridge-free building envelope is critical for several reasons:
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Energy Efficiency: A thermal bridge increases heat transfer, leading to energy loss. This can result in higher energy bills, as heating and cooling systems work harder to maintain desired interior temperatures.
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Comfort: Thermal bridges can lead to uneven temperatures within a building, causing discomfort for occupants. Cold spots created by heat loss can result in a less enjoyable living environment.
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Moisture Control: Thermal bridges can lead to condensation issues, as surface temperatures drop below the dew point. This may promote mold growth and deterioration of building materials, affecting the building's longevity and occupant health.
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Environmental Impact: By reducing energy consumption through proper thermal bridge design, buildings can significantly minimize their carbon footprint, contributing positively to environmental sustainability.
In conclusion, a well-designed thermal bridge-free building envelope enhances energy efficiency, improves occupant comfort, mitigates moisture issues, and contributes to environmental conservation.