From Across the Pond
by: Paul Kando
Budapest, Hungary - I am on the lookout for practical ideas, especially when traveling. Here are two worth sharing. First, Hungarian laws now prohibit the sale of a house without an energy audit report that describes current conditions. Other countries in the region have similar rules. A seller is not required to fix any deficiencies, only to advise the buyer of the actual energy performance of the house. Since I hear many comments by Maine homeowners about how, now that oil costs more year after year, they didn't know what they were getting into, I consider this an excellent idea.
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Second, I am impressed by the way Hungarians (and other Europeans) now insulate existing houses, regardless of age or style, from the outside. The method is so simple that many home owners do the job themselves. Alternatively a two person crew gets the job done on the typical single family house in two to three working days, without in any way disrupting or inconveniencing life within. The method has been developed for masonry buildings, the most popular, highly airtight construction in Hungary, but I have seen it applied to wood framed houses as well. I will focus here to polystyrene panels applied to exterior walls, although other materials are also being used.
The handy size of the foam panels makes the job easy: 500 mm x 1,000 mm (approximately 3 feet by 1.5 feet). The thickness varies, usually between 100 mm and 150 mm (roughly 4" to 6"). Panels of this size are a child's play to handle - especially compared to our unwieldy 4' x 8' or 2' x 8' standard sizes. The R value is between 5 and 6 per inch thickness - R-20 for a 100 mm thick panel and R-30 for the 150 mm panel. I am especially impressed by the Austrian-made graphite-impregnated polystyrene panels, pictured, which have an improved R-value.
Installation is fast and easy: mortar-like, "high-grab" glue is applied to the back of each panel, which is then pressed into place on the wall in a brick pattern. Odd sizes are easily cut with a hand saw, using a straight edge as a guide. At corners the panels are run flush to the edge, then overlapped by panels on the adjacent wall, as shown. At windows and doors, strips of the same foam of appropriate thickness are installed in such as way as to insulate as much of the window frame as practicable. This minimizes thermal bridging through the framing. The result is a seamless insulating layer covering the surface of the house.
Once all the foam has been installed, a skim coat of the adhesive mortar is spread onto the whole surface. While this is still soft, a coarse-mesh (5 x 5 to 10 x 10 mm) fiberglass fabric is pressed into this mortar layer. This helps hold the finish layer of stucco which, once painted, completes the job. The time it takes to recover the initial investment typically ranges from 2.5 to 4.5 years. Locals reckon that each centimeter of foam thickness translates to a 2-3% reduction in a home's heating energy bill - 30-45% for a 150 mm installation.
Professionals can wrap a house in a couple of days, leaving only the paint job to be done. But a home owner couple can also do it - a wall at a time on consecutive Saturdays, if time is in short supply. On a single story house people work from ladders. On two story walls the most time consuming part of the job turns out to be erecting and later dismantling the scaffolding.
Could this system be adapted to existing Maine houses? Definitely. Clapboards or shingles would be removed and the foam panels glued to the outside wall sheathing. Care must be taken that the insulating layer is sufficient to prevent the inner surface of the sheathing from ever reaching the dew point - 4" of polystyrene minimum thickness here in Maine. This is important to prevent condensation of any stray moisture inside the wall cavity. With some extra work, clapboards may be added to the finished exterior, using furring strips - adding to the cost significantly.
Otherwise what is wrong with stucco? Not the traditional look, of course. Europeans are at an advantage: there houses come in all styles, sizes and ages. There are walls built by the Romans still in use in Hungary and gothic structures may be nestled next to art deco, baroque, rococo or ultramodern. Except for the rare "historic" structure, practicality wins out over nostalgia, as ancient buildings repeatedly get a new lease on life, war after war, century after century of use. Call me a heretic, but for my money, 9 out of 10 existing Maine houses wouldn't suffer any loss of "quaint New England appeal", were they clad in brightly painted, durable stucco instead of pealing clapboards - and let's not even to mention fake clapboards like vinyl and aluminum.
Interior storm windows described here will go well with this exterior insulation system, doubling the R value of double glass and tripling that of single glass windows - shaving maybe another 8-10% off the heating bill.