Exterior Wall Insulation

Walls are responsible for around a third of all the unwanted losses or gains of heat and cold in a typical home. Exterior wall insulation may save you hundreds of dollars per year in heating and cooling bills (and your household will be more comfortable and produce less C02, helping fight climate change)..

Wall insulation is often underestimated. But due to their larger surface in the home's envelope, their insulation can be much more important for comfort and energy savings than insulating the attic or other rooms. The only disadvantage is... the higher cost (at least twice the cost of attic insulation).

Types of Exterior wall insulation

The type of exterior wall insulation depends on the type of walls. Cavity walls should include cavity insulation and, in many cases, insulated sheathing over the outer walls, behind the siding.

Solid walls should be insulated on their exterior surface or in some cases on their interior faces (see: Exterior vs. Interior Solid Wall Insulation).

Image, Cavity Wall Insulation: Energy Saving Trust Exterior Wall Insulation | Cavity Insulation

R-values

Whatever the type of walls or your climate zone, exterior wall insulation is always critical, except in some hot-tropical climates.

Too little wall insulation is also a common feature in newer buildings, and of most official guidelines. See: Official Recommended Insulation & Climate Zones.

New Types of walls

Besides traditional cavity insulation and insulated sheathing (of the surface of the walls), there are now new wall insulation technologies for new homes. These new technologies involve materials like SIP (Structural Insulated Panels) and ICF (Insulated Concrete Forms).

Checking the wall insulation

To know the amount of insulation in homes with cavity walls you may inspect their inside using some basic methods: see Simple tests to inspect the existing wall insulation.

If you don’t know whether your brick walls are solid or cavity walls, check the brick pattern. Solid walls have alternate shorter bricks, and they are also typically thinner than cavity walls: a cavity wall is around 12 inch/30 cm wide while a solid wall is around 9 inch/23 cm wide. In other words, typical solid walls involve a 9 inch/23 cm header brick without a cavity, while typical cavity walls involve two 4.5 inch/12,5 cm bricks and a 2.5 inch/6,3 cm cavity.

Costs

Exterior wall insulation is more expensive and more difficult to install than the ceiling-attic insulation. The costs and the economics of wall insulation depend on several elements: the type of wall, the existing insulation, climate, etc.

Cavity wall insulation around $1,50 per square foot is common. Wall sheathing and solid walls insulation may involve amounts of at least $1,500 - $2000 (medium-sized homes), without considering stuccoing, painting or other costs. But these are very broad references.

Cavity insulation and insulated sheathing

Cavity wall insulation is often insufficient in colder climates. In such climates, insulated sheathing is also very important to avoid thermal bridging and lower energy-efficiency.

See: Insulated Sheathing Basics

Solid walls

Solid walls aren’t energy-efficient without insulation. See: Solid Walls Insulation.

Types of materials used in wall insulation

See:
Types of Cavity Wall Insulation
Insulated Sheathing Basics
Materials for Solid Walls Insulation

Required Insulation Levels (R-values)

Exterior wall insulation requirements depend on climate. See: Insulation requirements and climate zones.

Reflective insulation

In hot climates, reflective materials (foil-faced paper, polyethylene bubbles, plastic films and cardboard) can also be used with advantage in exterior walls. See: Roof Cooling Reflective Insulation.