Thermal insulation of walls, doors, windows, roofs

Thermal comfort is a state in which a person feels neither hot nor cold. The thermal performance of a building component is its ability to resist heat flow, measured by its U-value (transmittance, W/m²°C) or its thermal resistance $R$ (m²°C/W). A low U-value means better performance. For a composite element

$$U = \frac{1}{R_{si} + \sum \frac{t}{k} + R_{so}}$$

Insulation of exposed walls

1. Cavity wall: Two leaves with a 50 mm air gap; the still air resists heat flow. Filling the gap with insulation (glass wool, thermocole, polyurethane foam) improves it further.
2. Insulating material on the wall: Boards of thermocole (EPS), cork or mineral wool fixed on the outer face (external insulation, best for using thermal mass) or the inner face.
3. Hollow blocks / AAC / fly-ash bricks: Walls built from low-conductivity units.
4. Thick walls and reflective surfaces: Light-coloured paint or lime wash reflects solar radiation.

 Out |brick|air gap|insulation|brick| In

Doors and windows

• Use double glazing (two panes with a 6 to 12 mm air space) or low-E coated glass.
• Use timber or uPVC frames instead of metal, because metal conducts heat.
• Fit weather stripping to stop air leakage.
• Shading: chhajja, louvres, curtains, and trees on the east and west sides.
• Use insulated, solid-core flush doors.

Roofs

The roof receives the most solar heat, especially in the plains.

1. Terracing / brick-bat coba on the RCC slab, with 75 mm lime concrete.
2. Insulation layer: Thermocole, glass wool or foam concrete on the slab, covered by waterproofing.
3. False ceiling with an air space and insulation.
4. Ventilated double roof, or a roof over the slab to give shade.
5. Reflective finish: white china mosaic or white paint.
6. Green roof or water spray / pond: evaporative cooling.

  Waterproofing + tiles
  Mud/lime concrete 75 mm
  Insulation (EPS)
  RCC slab