New siding can bring an added bonus - an opportunity to insulate.

Among certain traditionalists, especially those with links to the UK, the cladding material on a building’s exterior is sometimes referred to as “weatherboarding.” It sounds a bit like a form of torture—perhaps involving prolonged exposure to a wet Maritime spring. But the term aptly conveys the function of whatever material goes on the outside of your home

Siding, as it’s more commonly known in this part of the world, is supposed to provide protection from the elements—from precipitation in its myriad forms to wind—which can turn a bit of moisture into a meteorological assault.

It’s useful to think of siding as a raincoat. Additional layers worn underneath will keep you warm, as long as the outside shell keeps you dry. The challenge—and here’s where the analogy breaks down—is that this architectural jacket stays on year-round. The type of rubber slicker worn by fishermen would definitely shed water, but for everyday use most people would want a garment that is more breathable, and possibly something a little more elegant.

Installing new siding is sometimes viewed as a way of making your home warmer and more energy efficient, but generally the siding itself does not have that effect; it’s the insulation installed underneath that makes the difference.

Exterior remodeling is an excellent opportunity to add a layer. In the process you can dramatically change your home’s outward appearance—preferably for the better, though opinions vary widely on the aesthetic merits of various cladding materials.

Paul Pettipas, CEO of the Nova Scotia Homebuilders Association, says anyone considering new siding should also look at the options for adding some R-value, which is the capacity of an insulating material to resist heat flow. “The cheapest time to do things is when that wall’s open,” he points out.

Once old siding has been removed, it’s easy to apply rigid foam panels on the wall sheathing. Even old homes have usually had insulation installed inside the walls at some point—either fiberglass batts added during an interior reno job, or loose material blown in through holes in the outside wall—but that’s just between the studs. Direct contact between the studs and the sheathing creates a heat leakage problem. The new foam layer, by contrast, is continuous. Pettipas says this additional barrier against the cold could be characterized as “an envelope around your home.”

Exterior cladding can then be fastened using long nails that go through the foam. The type of siding material makes little difference to the wall’s overall insulation value, so other factors come into play.

Vinyl—technically polyvinyl chloride—is most popular for reasons of economics and ease of installation. Freedom from the tyranny of scraping and painting can also be achieved with aluminum, which gives a smooth finish, while fibre cement or hardboard products are typically embossed with a more-or-less convincing simulated wood grain.

The widespread adoption of these materials has almost made “siding” a dirty word among heritage building purists, but adding high-tech foam insulation does not preclude using historically accurate cladding.

Siding made of natural wood is available in a wide range of styles, and high-quality pre-finished wood siding products usually come with a warranty that ensures you will be able to forego painting for a good long time. Even wood shingles, the look that defines vernacular Atlantic Canadian homebuilding, can be used over foam if strapping is added to receive the shingle nails.

In fact, for any cladding other than vinyl, some type of strapping or spacing layer is recommended in order to avoid moisture problems. Pettipas recalls renovation jobs that revealed studs as squishy as a sponge due to improper siding installation 10 or 15 years previously. This kind of damage can be prevented by using strapping—a series of 1”x3” or 1”x4” boards installed at intervals to allow air passage behind the siding—or commercial back-venting products known as “rainscreen.” 

“All you need is something to leave a 10-millimetre air space behind,” says Pettipas. “When we get rain—and we get horizontal rain here—it drives in underneath the siding. If you’ve got that air space, it has time to dry.”

Vinyl siding is different because it is essentially hollow; it’s designed to hang on the wall instead of being nailed flat against it, which means air can move freely behind the cladding. This self-venting quality is one way vinyl comes out ahead on installation cost.

Pettipas advises buyers to do their homework. “Make sure it works here and it meets the building code,” he says. “If you possibly can, go see it installed—and even better, go see it after a couple years.”

Provincial energy efficiency programs offer rebates for insulation retrofits, so it’s worth checking out the eligibility requirements.

“Don’t get sucked into not putting anything on,” advises Mike Proud, manager of the Prince Edward Island Office of Energy Efficiency. He says a siding job is your perfect chance to add some serious insuation, “and we’ll give you a grant for it.”

Randy McAllen, with Efficiency Nova Scotia, also warns homeowners not to be enticed by siding offers that come with vague promises of thermal protection. “We always recommend three quotes, and a lot of discussion about what will benefit you and what won’t,” he says.

“You really are missing the opportunity by putting on anything thinner than R-4,” says Joe Waugh, with Efficiency New Brunswick. “Because when’s the next time you’re going to replace the siding? It’s probably a long time down the road.”

Green tradeoffs

Insulating your home saves energy, and in this respect it reduces negative impacts on the environment, but there are environmental effects associated with the production of insulation. Some extruded polystyrenes (XPS), have created controversy in the green building community because of hydrofluorocarbons (HFCs), which are used as blowing agents to manufacture the foam, and which are released over time. Experts anticipate that these greenhouse gases will soon be replaced by less harmful blowing agents. Until then, some have argued that added R-value achieved with XPS offers diminishing environmental returns.

There are also ecological ironies attached to various siding choices. Manufacturing some synthetic products like vinyl and cement board requires a high energy input, and involves potential contaminants such as dioxins. Wood is renewable, but it will require repeated treatment—painting or staining—over its lifespan.

Yuill Herbert, a director with Sustainability Solutions Group, says he still leans toward wood shingles or siding, especially if it can be obtained from local producers or sources certified by the Forest Stewardship Council (FSC). But he acknowledges wood tends to be a more expensive cladding option.

For Herbert, who is also a board member for the Atlantic Chapter of the Canada Green Building Council, another good choice is sheet metal. Though energy-intensive at the production end, it’s stable and durable over the long term, non-combustible, and resistant to Maritime weather. “And it’s fully recyclable,” he points out.

Renowned Nova Scotia architect Brian MacKay-Lyons has raised corrugated steel to new levels in his contemporary designs. While it may not appeal to the sensibilities of some heritage advocates in this region, anyone who has been to Iceland will appreciate that this utilitarian cladding is not incompatible with traditional homebuilding.