Sunday, March 4, 2012

Cap and Boots (VIII)

I'd like to bring this series, looking at older homes and their problems, back full circle to roofs (the cap) and foundations (the boots). So many of the problems besetting older buildings revolve around these two areas one way or another.

It's been a fairly mild winter around most of the New England area, other than a freak snowstorm back in October of last year, there has been no snow to speak of and milder than normal temperatures. I was beginning to wonder, now that the Maple sap is running, if we weren't going to be sliding right on into Spring with no further weather inconveniences, however we received a mild dusting of snow in the past week.

Whenever it snows here a fabulous opportunity is presented:  it is easy to see which buildings have good thermal performance and which do not. How? Just look at the roof. Buildings with poor insulation in the ceilings and under-roof areas of the structure, and more especially those buildings lacking a moisture barrier underneath that insulation, suffer from the heated air in the conditioned space making its way out and into the attic area, where it can warm the underside of the roof deck. That warming melts the snow off the roof. I took a few steps around the neighborhood to snap some shots of which might be described as fairly typical subdivision for New England in terms of building age (around 110 years) and building style. Here's a glace up a street in one direction:

Notice how the blue house in the foreground has snow still on the roof while the next one further down is bare of snow? Looking past that one you can see the roof on the next house has most of the snow but some bare patches on the ridge.

Turning 180˚, I snap a picture of the apartment complex two doors down, with a classic striated pattern of snow on the roof:

The snow is gone from the ridge, and what snow is left is in a pattern of thick and thin bands. What you are seeing is a wonderful demonstration of thermal bridging, albeit in a reverse form. The roof probably has no insulation, and the ceiling in the living space below, while it may have insulation, has no vapor barrier and thus warm air leaking out from the conditioned space is warming the roof deck. It warms those parts of the roof deck without rafters most rapidly, and thus the snow directly above the inter-rafter spaces is thinner.

In typical thermal bridging, where the spaces between the rafters or wall studs IS well insulated, the rafters and studs become the main conduits for thermal transfer through the wall or roof. In the above case, as there is no insulation at all, the rafters prove slightly more resistance to thermal transfer than the boarded-over portions of the roof between the rafters. Wood is an insulator, but not a great one.

Turning another 90˚ to look at the house across the street from the apartments:

Again, the roof is bare of snow from the ridge downward, to about halfway. The warm air that has risen into the attic space naturally rises to the peak of the roof, and that portion of the roof warms the fastest.

Another turn to look at the house across the street  from where I stood - this house is facing due east:

Again, it is obvious that the roof deck is getting warmed. Also note that the snow tenaciously remains in the dormer valleys. One of the principal negatives to placing dormers or having buildings in an 'L'-, 'U'- or -shaped form, is that this configuration generally introduces valleys into the roof. Valleys are always the first place to accumulate debris of any kind, and the slowest to dry or lose snow, and thus become a location in a roof most likely to leak at some point in time.

Continuing my rotation with camera, I spot a house next the the one shown above, one with snow still on the roof:

And that is what you ideally want: snow to stay on the roof. If snow stays on the roof, that means that the roof is cold, which means that the conditioned space below the ceiling is holding its warm air.

So in this neighborhood, at best 25% of the houses seem to have decent thermal performance. The rest, leak like a sieve. My in-laws have a large leaky house down in Connecticut and in the winter their heating bills can approach $1000/month. When I think about this sometimes and mentally multiply it out to the number of old houses in colder parts of the country that are wasting energy in such a gratuitous manner, and then consider the likely direction of energy prices, well, it is a most sobering thought. We do waste incredible amounts of energy in this country, and buying a few fancy mercury-laden light bulbs is not going to put much of a dent in that.

If we had an extended cold snap and a lot more snow, the problem with warmed roofs intensifies into ice-dam conditions. Snow, you see, is actually a bit of an insulating blanket on top of the roof, and when the under-deck of the roof is warmed, the snow immediately on top of the roof surface melts and that water moves downhill until it reaches the eaves of the buildings which are cold. The water re-freezes. Gradually, the ice builds up at the eaves, and a small pond of water begins to form up hill of the ice. This water then can find its way back into the building, for even the best roofs are not really designed for what are effectively underwater conditions. A bad example, in fact an 'award-winning' example of ice damns from hell, is this place:

A pretty house in some ways, a real charmer in its storybook-esque 'handcrafted' detailing - yet, what a monster lurks within! All that money spent to jazz up the outside, yet, for a fraction of the price and a small investment in a thermal retrofit they would save thousands on their heating bill. And notice how the large valley contributes to the glacial movements on the roof, and how deeply built up the snow is on the dormer valleys?

With old houses it is possible to do insulation retrofits, and in fact testing a house for energy performance is offered for free in Massachusetts through a government agency. Modern spray foam expanding insulation provides a ready means of both insulating difficult areas (like the meeting of the top of the wall and the edge of the roof) and stopping the migration of heat to the cold portions of the building envelope.

Another aspect of the heat leaking problem is that warm air is moisture laden air. and when that moisture laden air contacts the cold roof deck, condensation occurs. In some cases the roof deck is sufficiently cold that the condensed moisture immediately freezes. Once it warms up again however, you can guess what happens - that moisture moves back down. Condensation is most acute around metal, and most roof decks are sprinkled with nail penetrations from the cheap roofing installed above. Each of those nails forms a point where condensation accumulates, both corroding the nail and forming an intermittent water drip onto the plaster work or insulation below.

Moving from the general to the specific, the roof nails themselves are more than likely to be of the electroplated galvanized type, which the local big box store sells in in 30# buckets for about $32. Inexpensive to be sure and they are galvanized - what could be wrong with this picture? Well, the electroplating process produces a nail which IS galvanized, however the layer of zinc applied is incredibly thin, so thin in fact that the act of driving the nail, of hitting the nail head, tends to remove a good portion of the coating, making the nail essentially a steel nail, prone to corrosion. Slate roofs fastened with electroplated nails are on the fast track to early retirement - a common repair blunder. A well made roof would only employ hot-dipped galvanized nails, or, even better, copper or stainless fasteners.

So, an old house is likely to be an expensive house to heat, especially those older homes built in an age of larger families and having a fair amount of square footage. My in-laws house, for example, is 4 floors and 6400 sq.ft altogether, and is an absolutely typical house in the subdivision in which they live, constructed at the turn of the century. Two people living in 6400 square feet and having to heat it - think about it. Their neighbor lives in a very similar house, alone.

An old house, unless it was built prior to 1750 or so, is unlikely to have been sited on the property with any consideration given to where the sun shines, so passive thermal performance will likely be poor. You'd generally want to avoid buying an older home on a north-facing side of the street.

The good news about insulation however is that is provides great bang for the buck and is an investment fairly rapidly repaid by reduced energy costs, so it is very worthwhile to do - especially in regards to insulating the attic/ceiling. The argument is a little harder to make with the double-glazed windows, particularly in regards to the embedded energy tied up in their manufacture and their dubious lifespans. Old sash windows are often quite leaky, and if they have lead paint and rattle around in their frames when the wind blows, think of all the airborne lead particulates being released. Ah, time to slide the ole' window open, s-cr--e-e-e-ch-h-h! - let in a little 'fresh' air.

As I mentioned in the first thread in this series, besides the roof there is another Achilles heel with older homes: the foundation. As I noted, many of the homes in New England are built on brick foundations. Brick is not such a bad material, however maintenance is critical, and bricks need re-pointing once in a while. If this is neglected, as it often is, problems start to develop in the foundation support. Case in point, the foundation of this house:

The lack of maintenance extends to the front porch, immediately adjacent:

The entire porch is surmounted by a porous roof which has some intriguing mold within I am sure:

One spot where the roof releases its built up interior water is right here:

And that spot of roof happens to be directly above the front steps to the door, so you might expect the condition of the front steps to be suffering a bit:

Swinging around to the other front corner of the foundation, we see that it is in similar shape:

And in case you might be thinking this is in any way unusual, a 180˚ swing around to look at the adjacent house reveals a similar situation with it's brick foundation:

Now, old houses are expensive to operate, with all the warm air leaking out, but they are really expensive to maintain. Well, things tend to get that way when minor and comparatively inexpensive maintenance work is neglected. A lot of homeowners would appear to choose the following approach when it comes to the decaying condition of their houses:

Not such a great strategy, as each neglected area seems to compound on areas adjacent.

An entire industry however has sprung up in response to this crisis. These businesses will spare you from unpleasant issues with peeling lead paint and decaying siding by simply casing your house in vinyl or thin metal siding. This place is a case in point:

It looks quite tidy, as do many of the houses around here which have received this tart-up. But then a cancerous lesion would look a lot better with a bandaid® or some artfully done make-up to cover it up. Why, if I had a toothache, and could see that I had a rotten molar, the way to set my mind at ease would surely be to cap the sucker with some nice fiberglass or mercury amalgam. Out of sight, out of mind. On to other stuff....

Of course, like the covered-over lesion or the capped rotten tooth, eventually the problem comes back into the scene, usually in a much more horrifically-developed form. Where once you had a toothache and a hole that could be cleaned out and patched up, you now require your entire jaw to be removed. But of course, it could be replaced with a nice titanium one. Might be a little costly, but oh well.

The more I look at this problem, and the ways we build houses amount to really not much more than a largely decorative phenomenon. When I consider how our culture is becoming more and more like a reality tv program all the time, where our rides can be 'pimped', and our 8 year-olds want to dress like little 'hos', I can see why the theatrical set, the stage set, has in fact become the archetypal building form.  Flimsy, quickly changed, concerned with nothing other than conveying an impression, preferably of wealth or 'tradition', and ultimately often poisonous to its inhabitants. In a financialized, get rich quick culture of dreamers, the house is merely an investment, a springboard to a fancier place and an apparently brighter future. Why invest in building quality when even a decaying box is going to reward its owner with a cash windfall 5~7 years later (the typical length of time a North American resides in a house) in a real estate market which inflates like a balloon? Why make proper repairs to you house, to invest in your house, when you aren't investing in your community by living there for a long time? Our houses are as transient as our culture. Committing to a house is committing to a community, and those values have become very unusual.

While old houses have their problems, and I for one would tend to put the rosy-tinted glasses to one side and fight hard not to fall in love with an old house, at least older houses were built with decent materials in most cases. They may have been built quickly, and shoddily at times, but the wood was better back then. And yesterday's 'quick' and shoddy' does not often match the modern 'improved' forms of 'quick and 'shoddy' - if anything, we're much quicker and much shoddier. Housebuilding, as commonly practiced, is generally a financial enterprise not an expression of craftsmanship or an honoring of your forebears and descendants.

Even though the construction quality of older homes may not have been the greatest, and maintenance perhaps a rarity with a majority of houses, the 'good bones', materials-wise, and some luck have allowed them to survive for 100 years or more.

The same future may not apply to new houses built today, even though there have been advances in many areas. Foundations tend to be better. Plumbing and electrical systems are, well, can be better. But the 2x6's in the walls and roof are crap compared to what was used for framing in the 1800's. Instead of harvesting first growth trees with their tight growth rings and minimal sapwood, we now harvest juvenile second- or third-growth trees, fast grown, coarse grained, and with a high percentage of sapwood. Nail-gunned up, their recyclability is dubious indeed. What was a 120 year detour from natural bounty to the landfill is fast becoming a 40 year detour to the landfill. Eventually this must crash of course.

And while new homes are at least free of lead and asbestos (and I say that with the caveat that home building materials imported from China may not be free of such materials, and are not tested for some insane reason), houses today are often built with so many synthetic materials that they have to be 'dried out' for a week or so in order to off-gas as much poison as possible. Vinyl siding, railing,s and columns are now a feature topic in Fine Homebuilding magazine. Lessons about passive solar orientation seem to be still largely ignored, though the typical house of today is far more energy efficient than the older examples. Looking around at the roofs after the snowfall though, I can see more than a few newer buildings which don't hold their snow. In fact, the increased tightness of many structures only means that the air leaks into unconditioned space happen at higher velocities. or, as has been seen more often than not, the encapsulation of houses effectively in a plastic bag to obtain that vaunted tightness, often has created extreme problems with trapped moisture and mold. The lawsuits aren't done in that regard by a long ways yet.

While most of the older homes around here still have their original slate roofs, invariably the new homes have the asphalt shingles, some of which will fail inside of 15 years. The roofing material manufacturers offer 20-, 30- and even lifetime warranties, however if you read the fine print you will see that these warranties are usually not transferable to future owners. They are banking in the fact that the owner will move and thus nullify the warranty. In fact a large proportion of re-roofing work is done simply to pimp up a tired house for re-sale.

I wish I could say that most older homes are worth fixing up, but in truth, unless you really fall head over heels for the place, or for some reason have no choice in the matter, it is best to avoid them. Like a sailboat, all you need to remember is B.O.A.T.T.: bring out another ten thousand. New homes can be built which are modest users of energy, non-toxic, and gentle on the environment. That doesn't describe most of what gets built, but it remains a possibility, and one towards which I am hopeful about seeing a larger societal shift.

That's all for this series, I hope it was informative and worth the read. Thanks for coming by the Carpentry Way.


  1. Great post. I'm an old homeowner (my house is old, not so much me), and I found your post very informative. We insulated our placer soon after we bought it, but neglected to do an energy audit at the time. Last year we re-did some siding, and our contractor found a huge gap in the blown-in insulation...Should have spent the $$ up front on a before and after audit...Next time!

  2. Great series, Chris. I've forwarded many of them to builder/friends.
    When I built our house as an ignorant twenty-something luck was with me to have avoided most of the pitfalls you've described, with the exception of the bathroom mold mentioned before. Passive solar on a sandy rise, locally sawn timber, good air movement around the house, pretty good insulation, most of the basics are holding up great after now 32 years. For me money spent on, say, re-roofing when the time comes actually feels good.

  3. Mathew,

    thanks for your comment and good thing you discovered that insulation gap. Many older homes are so leaky that the heat loss is equivalent to that obtained by removing an entire window from the house.


    good to hear from you, and congratulations on building your own house! A great thing to do and I'm sure a tremendous learning experience and creative opportunity.



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