STEAM FURNACES DON’T EXACTLY “BLOW UP,” FYI

My husband didn’t hear me the first 200 times I said, “Add water to the steam boiler reallllly slowly.” He’s from a part of the country where the populace prefers less catastrophic methods of home heating. So when the boiler quit due to low water, he descended to the basement, located the cold water valve, and let ‘er rip.

Steam heat is one of those Northeastern traditions, born of cheap coal and hard winters. You shoveled coal into a boiler, and the resulting steam swarmed up through cast iron pipes to heat colossal, iron radiators. Sure, the radiator valves leaked a little, and the pipes hammered, and every week or so you had to add water to the boiler reallllly slowly, but… inertia. And in the 1970s when people began to give one tiny darn about fuel efficiency, it became apparent that steam boilers would never measure up… well… The heat was so nice, pulsing so steadily from those masses of iron.

Adding to the comfy inefficiency of steam, the radiators tend to be too big. They were installed in the early part of the 20th century, when houses had single-pane windows and no insulation. During the decade after the Spanish flu epidemic of 1918-1919, radiators got even huger: They were sized for houses in which the windows were left open at night, all winter, to blow away the germs.

As homeowners insulated and weatherized over the years, the mismatch chafed. Most steam radiators retain at least some flaking paint not because it’s pretty, but because slapping on metallic paint reduces a radiator’s effectiveness–intentionally. Ditto for those boxy radiator covers. In apartment buildings of a certain age, there’s an entire cottage industry bent on out-witting the infernal steam radiators.

Well, my husband has beaten ours decisively. Cold water struck the red-hot intestines of the iron boiler, which shattered just the way the manual said they would. A pool of rusty water spread like furnace-blood across the floor.

 

I made a quick survey of the inefficiencies in this system:

Inefficiency of the boiler itself: Steam boilers always waste at least 15% of their fuel. Because my house is well insulated, my boiler was actually too big, further eroding its efficiency.

Heat loss to basement from mammoth, cast iron pipes: A lot, even though I wrapped them in insulation.

Radiator inefficiency: Between the dust, the paint, and boxy covers, a ton. Maybe 30-40%.

These various losses are apples and oranges, but they add up to a rotten fruit salad.

This house turns 100 this year. I think a century is long enough for the original technology to prove itself. We’re giving it a 21st Century Viessmann 222F direct-vent gas boiler with 98% fuel efficiency, three pump speeds, outdoor temperature sensor, and built-in domestic hot water tank–along with some flat-panel radiators, each one a zone unto itself.

We’re leaping a hundred years in a week.

What could go wrong?

KNOB-AND-TUBE WIRING: REPUTATION RESTORED!

Electron eater. — wikimedia pd

Knob-and-tube wiring, the antique technology that strikes terror in the hearts of home buyers, is not a fire hazard! In theory. Technically. Much.

So says this report, which examined the rate at which the early 1900s wiring starts house fires. After studying a bunch of fires and fire-trap houses, these investigators concluded:

“Properly installed and unaltered K&T wiring is not an inherent fire hazard.”

Ta-Daaaaa!

But what the heck is knob and tube wiring, you ask?

It’s the aboriginal electrical wire, standard equipment from the 1880s to the 1940s. It carried electricity into your house in copper wire wrapped in cloth insulation. As they snaked through the walls, the hot wires were kept clear of the flammable wood with ceramic insulators, some shaped like knobs, some shaped like tubes.

Knob and Tube wiring. — Wikimedia pd

Although K&T has been rendered obsolete by wire that’s wrapped in a metal or plastic jacket, remnants of the “legacy wiring” remain alive and well in many older houses. And contrary popular perception, it’s not particularly hazardous! I’m pleased to have found this study, in part because my Dad always contended that K&T was actually safer than the new stuff. But because he was prone to skepticism in the face of most technological “advances,” including computers, vacuum cleaners, and the clothes iron, I wasn’t entirely sure I should trust him on this point. Apparently, I can.

So, yay! K&T is a much maligned and innocent technology!

Now, there are just a few minor GIANT caveats:

1: In an overhead light fixture, the heat of the bulb can slowly cook the cotton insulation off the copper wires. I stumbled upon this situation in my 1918 bungalow, and the black char marks on the ceiling plaster were legit scary.

2: Adding insulation over K&T can allow the warm wires to heat up and set things on fire. An awful lot of old houses have had insulation blown blindly into their walls and attics over the years.

3: Those pure and original K&T circuits have been tampered with over the years, pushing them WELL past their design specifications.

Now, how do you know if someone has twiddled around with your original K&T?

Oh, we just know they have: When these houses were built, electrical fixtures were limited to an overhead light in each room, and a couple of outlets for the Victrola and one of those crazy new toasters.

But since then, a tidal wave of electrical inventions has washed through the marketplace, and into the house. When the electric razor appeared in the 1930s, your Grandpa had to have one. He spliced a new wire into the old K&T circuit in the basement, and poked it up into the bathroom wall to power a new outlet. Electric refrigerator? Splice in another branch! Vacuum cleaner? New outlet! Washing machine? Electric iron, fan, coffee percolator, radio, television, microwave, clothes dryer, cook-stove?

So many splices!

Each with the risk of untwisting, or touching something flammable, or lacking sufficient insulating tape!

Each brighter light bulb and bigger fridge pulling more hot current through the humble wire wrapped in cotton!

So it’s mixed news, really: K&T is not inherently a fire hazard. But exherently, it really might be. It probably is. I’m glad mine is all gone. Sorry, Dad.

wikimedia pd

IT’S THE PERFECT WEATHER TO PLAY “READ THE ROOF”

White makes right: Snow shows that the right side is better insulated than the left.

White makes right: Snow shows that the right side is better insulated than the left.

With a fresh blanket of snow on the roofs, and the furnaces churning in the basements, it’s a fine time to play “read the roof.” This amusing/depressing game can reveal a number of secrets that your house might otherwise keep to itself.

Like, where is there insulation, and where is there not?

On the right side of this first example, you can see a clear line where the insulation ends, over the “knee wall” portion of the third floor. (See cross section below.) Escaping heat is melting the snow faster on the lower part than the upper. On the left side of that big dormer, there are a couple of rafter bays where escaping heat has melted the snow completely, suggesting no insulation; and between them, a pretty well insulated bay. Chimneys are almost always good at conducting heat from the inside to the outside, melting snow in a circle around their base.

 

Action shot: Thermal bridging under way.

Action shot: Thermal bridging under way.

Here’s a classic case of “thermal bridging.” On the left side of this roof, the wooden rafters that support the roof are allowing heat to escape faster than the insulated bays in between them. The migrating heat melts the snow over the rafters a bit faster, creating those parallel lines. It’s like an X-ray of the roof framing.

Extra credit: The overshot eave of the bungalow gets no heat from the interior, so see how the snow there is slightly deeper there?

 

Compare and contrast: An efficiency freak does not live in my neighbor's house. She may not have amazing insulation, but she has a life.

Compare and contrast: An efficiency freak does not live in my neighbor’s house. She may not have story-book insulation, but she has a life.

Can you spot the hot spots?

Can you spot the hot spots? (That line down the middle is ice on my windshield. Sorry.)

OK, that’s my house. I’m an energy efficiency geek. The home of my neighbor is more normal. In old houses, those rafter bays are only about 4 inches deep, which really limits the amount of insulation you can cram in there. Both these houses would have been built with no insulation, or perhaps a product from the “Yankee Ingenuity” line. (Newspaper isn’t uncommon; I have also seen sawdust and old clothing.) Updating of insulation tends to happen piecemeal, willy-nilly, as the years  and energy crises and remodeling projects go by. The result is usually not “blanket of snow,” but “crazy quilt of snow.”

 

This last one is frankly open to interpretation. It’s an odd pattern. We can see again that the cap of the house — the flat part of the third floor ceiling–is better insulated than the sloping part over the eave. On that lower part, those narrow white stripes suggest that the rafters under the roof are actually the most insulating element of the “roof assembly,” and the rafter bays between them are letting heat out faster. And both the chimney  and the sewer vent stack are acting as thermal bridges.

The puzzling part is that row of hot dots. Something about the insulation pattern directs rising heat to these distinct spots in the roofing structure. Those hot spots may not be very big, but once the black roof is uncovered, it heats quickly in the sun and enlarges the dot.

For reference purposes, a cross section of a basic roof. And the ice dams that occur when insulation is of the crazy-quilt variety.

Cross section. That swirly stuff is insulation, but only in new or really well renovated houses.

Cross section. That swirly stuff is insulation, but only in new or really well renovated houses.