What an Exterior Renovation Does to BC Winter Heating Bills

Every January, someone in a 1970s Coquitlam two-storey opens a $600 BC Hydro bill and decides the old stucco has to go. They may be right about the stucco. Replacing it on its own will take somewhere between $10 and $25 off the next January bill.

What changes your winter heating bills is the work done to the wall while the cladding is off: the air barrier, insulation on the outside of the sheathing, the windows, and the joints between them. That is where exterior renovation energy efficiency in BC is won or lost, and it gets decided when the scope is written, months before anyone picks a stucco colour.

Does an exterior renovation lower heating bills in BC?

Only the parts of it that deal with heat loss. New stucco or siding by itself cuts space heating by 2 to 5 percent. Add air sealing and 2 inches of exterior mineral wool while the walls are open, and an older Metro Vancouver house typically uses 30 to 40 percent less heat: about 7,000 kWh a year, or roughly $1,000 on electric baseboard and $500 on gas.

Where the heat goes in an older BC house

Before pricing anything, it helps to know what you are paying to heat. On a typical pre-1980 house in the Lower Mainland, winter heat loss splits roughly like this:

• Air leakage: 25 to 35 percent
• Walls: 20 to 25 percent
• Windows and doors: 15 to 20 percent
• Attic and ceiling: 10 to 15 percent
• Basement walls, slab, and floors over crawlspaces: 15 to 20 percent

An exterior renovation reaches the walls, the windows if they are being replaced, and the share of air leakage that runs through the walls, sill plate, and rim joists. Together that is about half of the heat the house loses. It cannot reach the attic or the slab. A contractor who promises to halve your heating bill with a re-clad is counting attic and mechanical work they haven't mentioned, or guessing.

The split shifts by era. A 1990s house with plywood sheathing and interior poly loses less through its walls and more through windows and penetrations. A 1920s character home in East Vancouver, with board sheathing and often no wall insulation at all, can lose a third of its heat through the walls alone. Those are the houses where an exterior renovation with insulation pays off fastest.

Why new cladding alone barely moves the bill

Stucco, fibre cement, and vinyl siding add almost nothing to a wall's thermal resistance. Seven-eighths of an inch of cement stucco is worth about R-0.2, and fibre cement is in the same range. The rainscreen gap behind the cladding is vented on purpose, so it adds little.

The small saving a plain re-clad does deliver comes from the new weather barrier. Housewrap or membrane that is lapped and taped stops some of the air that used to blow through the old building paper. That is the 2 to 5 percent, and it happens mostly by accident, because nobody detailed the barrier for airtightness or tested it.

This is the most common mistake we see on exterior jobs. A homeowner budgets $50,000 to $60,000 for new cladding expecting lower bills, and the scope they sign has no air-sealing details, no insulation line, and no blower door test. The wall gets a new face and keeps its heat loss for another 30 to 40 years.

The parts of the job that change the winter bill

Air sealing the walls from the outside

With the old cladding off, the crew can seal the sheathing seams, the sill plate, the rim joists, and every pipe, duct, and wire that passes through the wall, then confirm the result with a blower door test before anything covers it. On an older house, that typically takes the result from 8 to 12 air changes per hour at 50 pascals (ACH50) down to 3 or 4. Space heating drops 15 to 25 percent, for $3,000 to $7,500 on a single-family house. Our guide to air sealing an older BC home walks through the sequence and the three tests.

Per kWh saved, air sealing is the cheapest item on this list.

Insulation outside the sheathing

A 2x4 wall with R-12 batts performs closer to R-10 once you count the studs, plates, and headers that bridge the insulation. Two inches of mineral wool board outside the sheathing adds about R-8 and covers every one of those bridges. During a re-clad, it adds roughly $8,000 to $13,000 on a 2,200 sq ft house, and together with air sealing it puts the heating cut in the 30 to 40 percent range. Our exterior insulation retrofit article covers materials and R-values in detail.

There is a moisture benefit too. Insulation on the outside keeps the sheathing warmer through a wet BC winter, so less indoor moisture condenses on it.

Windows, and the honest math on them

Replacing single-glazed aluminum windows with good double-glazed low-e units cuts whole-house heat loss by about 10 to 15 percent. On a house with 18 to 22 windows, that costs $22,000 to $40,000. Per kWh, windows are the most expensive item here by a wide margin, and they pay back in comfort and condensation control long before they pay back on the bill.

Timing matters more than the glass. If window replacement is anywhere in your next ten years, do it during the exterior renovation, while the rough openings are exposed and the flashing is being rebuilt. Doing it later in a finished stucco wall means cutting back new stucco around every opening. Our triple-glazed windows guide covers when the step up from double glazing is worth paying for.

Drying out a wall that has been wet

This one rarely shows up in energy calculations. Many older stucco and siding walls we open in Burnaby, Surrey, and Richmond have taken water for years at the window corners and the base of the wall. Damp batts and sheathing conduct heat far better than dry ones, and batts that have slumped to the bottom of a cavity leave the top of the wall with no insulation at all.

Repairing and drying that wall restores insulation the house was paying for and not getting. Nobody can put a clean number on it before demolition. It is part of why measured savings on leaky old walls sometimes beat the model.

What the numbers look like on a 1975 Coquitlam house

Take a 1975 two-storey in Coquitlam, about 2,200 sq ft, with 2x4 walls, original single-glazed aluminum windows, and a blower door result of 9 ACH50. A house like this needs around 21,000 kWh of heat a year, roughly 75 GJ. November through March accounts for about three quarters of that, and January alone for about a sixth.

Here is how the annual heat demand changes as the scope grows:

What that means in dollars depends on how the house is heated. At the 35 percent mark, which is air sealing plus exterior insulation, the house saves about 7,400 kWh of heat a year:

• Electric baseboard: about $1,000 a year, assuming roughly 14 cents per kWh. A January heating cost near $490 drops by about $170.
• Gas furnace: about $500 a year at around $16.50 per GJ delivered, assuming an older furnace at 85 percent efficiency.
• Heat pump: about $380 a year, because the heat pump already turns each kWh of electricity into two or three kWh of heat.

For context, that house starts near 100 kWh of heat per square metre per year. After air sealing, exterior insulation, and new windows, it lands around 55. EnerPHit, the Passive House standard for retrofits, asks for 25 in our climate, which also takes attic work, a heat recovery ventilator, better windows, and attention to the foundation. We are Passive House Certified, and we will tell you plainly that an exterior renovation gets an older house about halfway there.

Payback, by fuel

Energy efficiency work inside an exterior renovation is priced as an increment: what it adds on top of a re-clad you are doing anyway. For air sealing plus 2 inches of exterior mineral wool on the example house, the increment runs about $11,000 to $20,000.

On electric baseboard, that pays back in 11 to 20 years on energy alone. On gas, closer to 22 to 40. On a heat pump it takes longer still, unless the envelope work lets you buy a smaller unit. Windows on their own take 70 years or more to pay back on baseboard heat, so nobody should buy them for the bill.

We put those numbers in front of clients plainly. A re-clad wall should last 40 years, which is the right horizon for judging them, and the bill is only part of the return. Rooms stop feeling cold near the exterior walls, bedroom windows stop streaming with condensation in January, and the wall assembly dries out after a storm instead of holding water against the sheathing.

There is also a saving the energy models leave out. People in drafty houses keep the thermostat a degree or two higher to feel comfortable next to cold walls. When the wall surfaces warm up, most turn it down without thinking about it, and each degree is worth a few percent of heating energy.

Rebates shorten the payback, and they change often. Check current CleanBC Better Homes and utility offers before demolition. Several programs have required a pre-retrofit EnerGuide evaluation, and nobody can produce a valid baseline once the walls are open.

Plan the envelope before the heat pump

Many BC homeowners are replacing gas furnaces and baseboards with heat pumps, often with rebate money attached. The order matters. A heat pump sized for the example house as it stands would be oversized once air sealing and insulation cut its heat load by a third. Oversized units short-cycle, dehumidify poorly, and cost more up front. A 35 percent drop in heat loss often takes about a ton off the required size, which is $2,000 to $4,000 off the equipment price.

Cold snaps are where this shows up on the bill. When Arctic outflow winds come down the Fraser Valley and across Coquitlam and Burnaby, wind pressure on a leaky house rises just as the temperature falls toward minus 10. Infiltration jumps. An air-source heat pump loses capacity at the same moment demand peaks, and the backup resistance heat comes on. A tighter, insulated envelope keeps the heat pump within its range for more of those hours, which is the difference between a high January bill and a shocking one.

If you already own a heat pump sized for the old house, the envelope work still pays. It runs fewer hours on backup heat and cycles more evenly.

Step Code, permits, and what your municipality asks for

The BC Energy Step Code sets airtightness and energy targets for new homes. Renovations of existing houses mostly sit outside it, so a typical re-clad permit sets no energy efficiency target. Whether the wall gets air sealing and insulation is your decision.

In the City of Vancouver, larger home renovations can come with energy-upgrade requirements attached to the permit, so confirm with the city before the scope is final. On tight lots anywhere in Metro Vancouver, 2 or 3 inches of exterior insulation thickens the wall and can raise a setback question, which we check before design.

Townhouses and strata buildings

Owners in a 1980s or 1990s townhouse complex usually pay their own heating bills, often on electric baseboard, while the envelope belongs to the strata. When a depreciation report calls for re-cladding, the council decides whether air sealing and exterior insulation go into the specification. If they stay out of the tender, every bidder leaves them out, and the lowest bid wins a job that does nothing for anyone's January bill.

Write a target airtightness number and an insulation line into the spec so every contractor prices the same wall. Owners can raise it at the AGM before the special levy goes to a vote.

How we scope energy work on an exterior renovation

MV Construction has completed 200+ renovations across Greater Vancouver and Vancouver Island over more than 10 years. Our crews are fully licensed and WCB-insured, and our workmanship is warranty-backed. As a building envelope contractor, we price the energy items on separate lines in the written estimate: air sealing, exterior insulation, windows, and the blower door tests, each with its cost and the heating reduction we expect. You see the increment for each one and decide which make sense for your house and your fuel.

Where to start

If your stucco or siding is due in the next few years, get a baseline blower door test and your last 12 months of BC Hydro or FortisBC bills together before anyone prices the job. Those two numbers tell us which of the items above will move your winter heating bills.

Then call (778) 375-5672 or request a fixed-scope estimate for your exterior renovation. We will walk the house, look at the wall assembly, and put each energy item, with its cost and expected saving, into the written estimate before work starts.