OLD HOUSE INSULATION: Four Ways to Spend Less Heating (and Cooling) Your Old Home

If you live in a vintage home, chances are good that you have a love-hate relationship with the place. Many older houses have a charm that makes you feel good just being inside them. Newer architecture rarely delivers this same aesthetic experience. Trouble is, classic older homes are also quite likely to make your stomach churn whenever you see a new utility bill in your mailbox. Cold toes and extensive use of sweaters in winter, and too-hot rooms in summer may also be your regular experience as an owner of an older place. The good news is that there are effective strategies for improving the energy efficiency of your old house while also greatly reducing energy bills. The challenge is that you often need to work differently than with a newer home built in modern ways. You’ll probably never get your old place to be as economical as a new house built to today’s highest standards, but you can still do a lot to keep energy costs down and bank balances up.

Old House Insulation Strategy#1: Maximize Attic Insulation

This is simple and not particularly unique to older homes, but it’s also the easiest and least expensive energy upgrade you can do. Strictly speaking, there’s no practical upper limit for attic insulation depth. Where I live (Canada, with -30ºC winter lows), a minimum of about 20” of batts or loose-fill insulation makes sense in the attic. If you can fit 25” or 30” of depth under your roof, that’s even better. Besides inadequate attic insulation, many older homes also need more attic ventilation.

Ridge vents are more effective than the mushroom-style vents you see on roof tops, and they look much better, especially on older homes. It’s also relatively easy to retrofit ridge vents to an existing roof, even when you’re not installing new shingles everywhere.

Old House Insulation Strategy#2: Boost Wall Insulation

These 2″-thick sheets of extruded polystyrene foam delivered a tremendous boost in energy efficiency when applied to the outside of this older building. New siding went on over the foam. It’s technically challenging to increase wall insulation in older homes, but the results are usually worth it. That’s because most walls in older homes weren’t insulated to any significant level in the first place. Many old house walls are hollow, while others are simply stuffed with wood shavings, rags or old newspapers. When it comes to increasing wall insulation, you’ve got three options:

Boosting exterior R values: This makes the most sense when you’re already planning to replace exterior siding. The old siding comes off, rigid insulation sheets go on the wall sheathing (as above), then new siding over that.

Pros: Very effective insulation boost when using 2”-thick insulation board.

Cons: Only practical when you’re replacing siding. Also, window and door frames need to be extended in a weatherproof way over the added wall thickness. Custom-bent aluminum cladding is the best approach.

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Boosting interior R values:This makes sense if you’ve got ugly interior wall surfaces that you want to improve with new drywall. Rigid insulation sheets go on the interior faces of exterior walls, then new drywall on top. Longer-than-usual screws go through the new drywall, through the foam, through the old finished wall surface, then into the underlying wood frame.

Pros: Very effective insulation boost. No need to create exterior, weatherproof door and window frame extensions.

Cons: Only practical when you’re renovating interior walls. Reduces room size slightly and requires extension of interior door and window jambs.

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Boosting wall cavity R values: This approach is minimally disruptive and can be highly effective, but only if your wall cavities are truly hollow. The best approach uses slow-rise, two-part polyurethane spray foam injected into wall cavities. Injection from inside is easier and simpler, requiring only small patches in the drywall to cover injection holes. Foam can be injected from the outside, too. Foam gives off heat as it cures, allowing areas of missed foam coverage to be easily seen with an infrared camera.

Pros: Very significant boost in wall R values with no significant disruption of interior or exterior wall surfaces.

Cons: Only practical with hollow wall cavities. Use of infrared camera needed to verify presence of foam in all walls.

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Old House Insulation Strategy#3: Warm the Floors

Cold wintertime floors (and cold feet) are one of the biggest drawbacks of older homes, and the strategy for warming them up depends on the situation you’ve got. Are your floors cold because they exist over an unheated crawlspace? Don’t bother trying to heat the space. Crawlspaces are difficult to insulate and seal well, so they can suck up huge amounts of heat while offering only minimal benefit for your feet. Better to insulate the floor, but don’t use batt insulation stuffed between joists from underneath. This is a common approach that’s destined for trouble. Batts don’t add much warmth to floors, and they provide excellent conditions for rodent infestations. Spray foam insulation is far better on the underside of floors because it both seals and insulates. But even with spray foam in place, floors won’t actually get warm to the toes. For that you’ll need some kind of infloor heating. Electric infloor systems are easiest to install and don’t consume much power if used only to warm the floors.

Are your cold floors over a basement? You can follow the same procedure as when working over a crawlspace, or you can insulate basement walls and heat the basement like any other living space. Just be sure the basement is 100% dry, 100% of the time. Old homes are more likely to have basements that leak. Insulating the walls of a wet basement will almost inevitably lead to mold growth and poor indoor air quality throughout your home.

Old House Insulation Strategy#4: Use an Infrared Camera

Twenty years ago the magic bullet in energy efficiency tools was the infrared camera. It let you see areas of energy loss from the outside of a building, and the exact spot where this needed to be remedied. Trouble was, even the cheapest models cost a couple of thousand dollars back then. These days you can get very good infrared cameras for much less money, and there are enough of them around that you can probably borrow one if you’d rather not buy. Camera’s like these  let you see where heat is escaping from your old house so you know the best place to make improvements.

Bonus Old House Insulation Strategy: Optimize Your Energy Choices

The cost of heat energy varies wildly depending on what form you buy it and how it’s used.  The cost of a million BTUs of electricity used to power a baseboard heater in Ontario, Canada, for instance, is many times the cost of the same amount of heat energy in the form of natural gas burned in a high efficiency furnace. In regions where natural gas isn’t available, propane can be cheaper than the same amount of electricity used directly for heating. But propane is still twice as expensive as firewood even when you buy it cut, split and ready to burn.

One of the main things to remember as you choose the energy sources your home will use is the inherent inefficiency of grid electricity for heating. We certainly need grid electricity for lots of things, but you should never use it for the bulk of your heating needs. Go ahead and use it to warm floors here and there, or use it to operate a heat pump. Since the electricity used by a heat pump is employed to harvest heat from the air, the earth or a nearby body of water, energy efficiency shoots right up.  At current market prices, only natural gas offers a cheaper way to heat than an electric heat pump. It’s even cheaper than purchased firewood.

Energy costs aren’t going to get significantly lower and that’s a big deal if you own one of the many beautiful older homes in the world. Understand the options you’ve got for boosting energy efficiency and energy bills won’t be something you fear in the future.

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