Climate ready measures: Exterior walls and siding

Exterior walls and siding

Your exterior wall and siding play a major role in shielding your home from extreme weather. The climate ready measures in this section can protect your exterior walls and the rest of your home from the following hazards.

Siding materials

The tabs below  provide a description of the relative resilience of each siding material to climate hazards, as well as a comparison of their cost relative to the least expensive option. Materials are listed from least to most expensive. 

Vinyl siding (standard)

Vinyl siding is not recommended. It is, however, the least expensive, and most common siding material in Calgary. Since vinyl is made of manufactured plastic, it quickly melts when exposed to the high heat of a wildfire.

Cheaper vinyl can also be damaged by extreme heat, crack with fluctuating weather, and can be easily damaged by hail and high winds. If you want to improve the resilience of your home, you should consider upgrading to a more resilient and durable material.

 

Aluminum siding

Aluminum siding is quite resilient to most hazards:

  • Hailstorms and debris driven by high winds can cause aluminum siding to dent or scratch but will not affect the integrity of your home.
  • Scratched and dented panels can be easily replaced.
  • Aluminum siding does not crack during freezing and thawing cycles.
  • As with vinyl, you can choose insulated aluminum with an increased R-value, providing greater protection against extreme heat.
  • It can withstand extreme heat, and will not easily ignite, burn or melt if exposed to wildfire. 

Aluminum siding can be environmentally friendly. Siding can contain up to 30% recycled content, and large quantities of aluminum siding can be brought to a City landfill for scrap metal recycling. Some private metal recyclers may buy scrap metal.

Installed costs*

+35% compared to standard vinyl siding

Engineered wood siding (wood composite)

Wood composite siding is a blend of wood fibre and resin that creates an aesthetic material that is resilient to most climate hazards. Wood composite siding has many benefits:

  • Fire-resistant, but less so than some other materials like fibre cement board, metal and brick.
  • Good impact resistance compared to other sidings like vinyl and aluminum. 
  • Handles extreme heat and freezing and thawing cycles without warping or deteriorating.
  • Has a high R-value and provides better insulation from extreme heat than natural wood.

Installed costs*

+45% compared to standard vinyl siding

Insulated vinyl siding

Insulated vinyl uses a foam board backing to fill what is otherwise gaps behind the material for airflow.

  • Provides some impact resistance against hail and high winds.
  • Greatly enhances R-value and performance in extreme heat, making your home more energy efficient.
  • Since vinyl is made of manufactured plastic, it quickly melts when exposed to the high heat of a fire.

Installed costs*

+60% compared to standard vinyl siding

Fibre cement board

Fibre cement board is one of the most resilient siding types for wildfire, hail and high wind.

  • Many fiber cement products carry a Class A fire rating and can withstand several hours of heat from fires before failing.
  • This siding is mostly unaffected by hot climates and won’t shrink, expand, melt or warp.
  • Fibre cement board has been proven to stand up to strong wind and hail storms without sustaining damage.
  • Water can accumulate from freezing and thawing cycles, damaging the siding if it is not correctly maintained by painting it with water-resilient paint.
  • The R-Value for fiber cement is fairly low (at 0.50) and is considered below average in terms of insulation.

Installed costs*

+65% compared to standard vinyl siding

Cementitious stucco

  • Stucco is fire resistant and will hold up well to flying debris in moderate wind and hail, but severe storms can cause damage.
  • Improvements in synthetic stucco (Exterior Insulation Finish Systems, or EIFS) significantly enhance water resistance, insulative value, and protection against cracking.
  • Stucco does not handle moisture well, and is not ideal for protection against heavy rain or winter storms; moisture and snow can cause stucco to shrink and crack.
  • Stucco typically has a lower R-value (around 0.2), unless you use a three-coat finish, in which case the R-value can go over 1.0 and provide protection against extreme heat.

Installed costs*

+70% compared to standard vinyl siding

Steel

Galvanized or coated steel siding is an extremely robust material and stands up well to wind, rain, hail, and winter storms.

  • Steel siding is non-combustible; it will not ignite and spread fires.
  • Steel siding on its own doesn’t provide a lot of insulative value, however, as with vinyl it is possible to purchase insulated steel siding which has an increased R-value, providing greater protection against extreme heat.
  • Steel siding will perform well in a wide range of climates, including in hot temperatures.
  • Like aluminum, steel siding can be made from recycled materials and old steel can be recycled.

Installed costs*

+100% compared to standard vinyl siding

Natural wood

Natural wood siding, common on older homes, is prone to damage by climate hazards, notably wildfire, high winds and hail.
  • Wood siding can be treated with chemical flame-retardant sprays to improve its fire-resistance, but fire can still penetrate.
  • If you choose wood siding, make sure to use high-quality wood, metal flashing on corners, seal the joints well, and use a water-resistant paint.
  • Natural wood has a relatively low R-value, and as it warps over time its insulating quality will diminish.

Installed costs*

+160% compared to standard vinyl siding

Brick

  • Brick cladding is highly resilient against fire, hail and high winds, as long as the fastening system or mortar is in good shape.
  • Brick also provides great protection against extreme heat, cooling your home and reducing your energy bills.
  • Bricks don’t become weak when they absorb water and so they hold up well in driving rain.

Installed costs*

+195% compared to standard vinyl siding

Stone

Stone siding is resistant to fire and will not damage in high winds. It is susceptible to cracks from freezing and thawing cycles. It is not very energy efficient unless insulated; with R-values for natural stone ranging from 0.01 to 0.41, depending on the type of stone. 

Installed costs*

+455% compared to standard vinyl siding

*Cost estimates are based on RSMeans Residential Cost Data 2020.  

Wall sheathing

Wall sheathing is the material (usually OSB or plywood) that forms the inner layer of your exterior wall, which the weather protecting membrane and siding material attach to. Walls that are sheathed completely and properly will provide greater resilience to multiple climate hazards. 

Consider the following:

  • Fire-rated sheathing can bolster the fire resistance of a wall assembly. 
  • Plywood has improved water resistance and drying ability compared to OSB. 
  • Rigid insulation should not be used alone as a wall sheathing. It does not provide protection from high winds. 
  • Wall sheathing should not be tightly sealed. Gaps between the panels are essential to permit breathability and allow any trapped moisture to dry out. 

Wall air barrier

A wall air barrier is the material (typically felt paper, or polyethylene or polypropylene wrap) that goes on the outside of your wall sheathing, before you put your siding material on. Air barriers stop air leakage between the inside and outside of your home while allowing vapour to move through.

An airtight home lowers heating bills, prevents cold drafts, and can help protect your home against extreme heat. If replacing your exterior siding, consider replacing or repairing the exterior air barrier too. Providing a continuous air barrier, with adequate structural support, will help resist wind and air pressure loads as well.

A reflective wall air barrier can be used to protect against extreme heat. However, if you want to reduce energy bills all year round, you should instead install more thermal insulation in the exterior walls. 

As per section 5.4.1 of the National Building Code – Alberta Edition, a permeable (breathable) air barrier is required to be installed on the exterior wall surface beneath the cladding to provide the principle resistance to air leakage, as well as a vapour barrier on the inside (warm side) of the wall. 

Disclaimer:  The content of this document is for informational purposes only and cannot be construed as technical advice with respect to any particular building(s) or construction project(s). The Handbook does not recommend or endorse specific products or companies. All products and measures should be installed by a professional contractor, according to manufacturer specifications and following all City Bylaws and codes.