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Key points

  • In hot climates choose windows with a low solar heat gain coefficient (SHGC) and reasonable visible transmittance (VT).
  • An aluminium frame without a thermal break is a bridge that carries heat indoors.
  • A radiant barrier can cut attic heat flow by about 40%, but that equals only 8% to 12% of annual cooling cost according to PNNL.
  • In an inverted roof, XPS insulation above the waterproofing protects it from temperature swings and UV.
Written for:OwnerContractor

In our climate the sun is the biggest load on air conditioners. Heat enters first through the roof, then the windows, then walls facing the west and south sun. This guide orders the options and links to the detailed articles.

1) The roof: the largest sun-exposed area

  • Roof insulation is the foundation; compare materials in roof insulation and thermal insulation.
  • In an inverted roof the waterproofing goes on the slab, XPS boards above it, then a protective layer; the insulation protects the membrane from mechanical damage, extreme temperature swings and UV1.
  • White single-ply membranes such as TPO are an option in some systems2. See roof waterproofing.

2) Windows: glass and frame

  • SHGC is the share of solar energy passing through the window (0 to 1), and lower is better in hot climates, with a reasonable VT for daylight3.
  • A Low-E coating reflects infrared and ultraviolet radiation3.
  • Aluminium conducts heat very well; a polyamide thermal break interrupts the heat path and reduces cooling costs4.

Details: windows and glazing.

3) Radiant barriers: real but limited benefit

According to PNNL and the U.S. DOE, a radiant barrier can reduce attic heat flow by about 40%, but this equals only 8% to 12% of annual cooling cost, not 40% as some adverts claim5. It is a complement, not a substitute for ceiling insulation5. See radiant barriers.

4) External shading

Practical advice: external shade (canopies, sun breakers, trees away from foundations) stops the sun before it reaches the glass, which works better than internal curtains that block light after the heat is inside. Mind municipal rules for shades: car shades and screens. For trees: water around the building.

5) A suggested order of priorities

  1. Roof insulation and sound waterproofing.
  2. Windows facing the west and south sun: low-SHGC glass or external shading.
  3. Sealing air leaks around windows and doors. See indoor air and dust.
  4. AC maintenance and clean filters. See the preventive maintenance plan.
  5. Add-ons such as radiant barriers after the above, with realistic expectations.

The order is general practical advice; for a new build or major renovation, an engineer's thermal calculation decides what pays off for your house.

Sources

The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.

  1. 15 Reasons to Choose an Inverted Roof (Protected Membrane Roof with XPS) — DuPont Performance Building Solutions
  2. 2Types of Roof Membranes for Flat or Low-Slope Roofs — Archtoolbox
  3. 3High-Performance (ENERGY STAR) Windows — U-factor, SHGC, VT, low-e — Building America Solution Center — Pacific Northwest National Laboratory (PNNL) / U.S. DOE
  4. 4Polyamide Thermal Breaks for Aluminum Windows: An Overview — Gabrian International
  5. 5Attic Radiant Barriers — Building America Solution Center — PNNL / U.S. DOE
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This guide is for general information and planning, based on standards and technical guides. Standards are revised periodically; in Saudi Arabia the binding reference is the Saudi Building Code and the instructions of the competent authorities. For design and execution, use a licensed engineer or technician. Found an error? Tell us.