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posted by cmn32480 on Saturday December 05 2015, @04:47PM   Printer-friendly
from the rebuilding-the-present dept.

For John Dulac, analyst at the International Energy Agency's (IEA) Sustainable Energy Policy and Technology directorate, retrofits represent an essential part of reducing Europe's energy consumption.

"Deep energy retrofits of the existing building stock are critical to meeting a sustainable, cost-effective, low-carbon pathway for the European building sector," he says.

Dulac estimates that around 70 percent of Europe's building stock in 2050 will be composed of buildings that already exist today.

"Even if you're building hundreds of thousand of these passive-style [energy efficient] new buildings, when you're talking about 225 million existing households, it's peanuts, it's nowhere near where we need to be," he says. "So there really needs to be a drive of taking these new technologies for new constructions and translating them to low-cost technologies for existing buildings."

Dulac says that the technologies that need to be applied to existing buildings in terms of insulation, air sealing and low-emissivity, double-pane windows are typically readily available in most markets in Europe for new construction and are often highly cost effective.


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  • (Score: 0) by Anonymous Coward on Saturday December 05 2015, @05:56PM

    by Anonymous Coward on Saturday December 05 2015, @05:56PM (#272213)

    Depends on where you live as to whether double or triple pane windows are worth the investment too. Here in Florida, the tiny amount of savings will not pay for the windows for decades, and it doesn't increase the resale value enough to cover the expense of the upgrade either. Unless you live in an area where property values are still high, you will never make back the money spent on energy efficient windows here.

  • (Score: 2) by Phoenix666 on Saturday December 05 2015, @06:24PM

    by Phoenix666 (552) on Saturday December 05 2015, @06:24PM (#272222) Journal

    Replacing your windows with triple-paned ones has a terrible ROI. They're so expensive and the resultant R-value is nothing to write home about. There are people who are working on transparent aerogels that will dramatically increase the R-value of single pane windows, but that's a long way off.

    Right now you're much better off with insulated roller shutters. They're common in Europe, rare in America. Some people don't like how they look, but they do confer much better insulation as well as better security and privacy and storm resilience.

    There's also the consideration that windows that get a lot of sun in the winter are good because of the solar gain, but windows that get a lot of sun in the summer are bad because of the solar gain. You'd want the extra radiation coming in the former but putting awnings or reflective film on the latter might be more desireable.

    --
    Washington DC delenda est.
    • (Score: 2) by gnuman on Saturday December 05 2015, @07:20PM

      by gnuman (5013) on Saturday December 05 2015, @07:20PM (#272243)

      Replacing your windows with triple-paned ones has a terrible ROI. They're so expensive and the resultant R-value is nothing to write home about.

      http://www.allweatherwindows.com/the-pros/architect/glass-performance-chart/ [allweatherwindows.com]
      http://homerenovations.about.com/od/windowsanddoors/f/doublepanewindow.htm [about.com]

      So 0.85 vs. 3.0, or about 4x better insulation. And you may say "but, but, hot place, who cares?"... What is your energy costs to heat and cool your living space? And sure, while an awning may be better for places like Florida than upgrading windows, most of Europe still has winters where temperatures drop to below 0C during the day. Having a temperature gradient of more than 20C between inside and outside, you really care if you have 0.85 R-value vs. 3.0 R-Value.

      https://en.wikipedia.org/wiki/Thermal_transmittance [wikipedia.org]

      So let's say you have 10 m2 of windows in your house. Single pane. Temperatures drop to 0C, and your inside is 20C. You are losing about 1000W through windows, and assuming your single pane windows are not leaky. So assuming this lasts for 3 months, that's about $300-$500 in lost heat, never mind cold spots near windows.. Now, you have good windows, same conditions, you are losing 200W through windows, 5x less. $60-$100. So let's say a saving of about $300 just for 3 months. Over 25 years, that's $7500, and I'm assuming very mild winters.

      For that much money, I can get new windows over that time period,

            https://www.homedepot.ca/en/home/p.5000-series-vinyl-left-handed-casement-window-23x38-3-14-inch-frame.1000526472.html [homedepot.ca]

      And this is in addition that old windows were leaky, have condensation, freeze, transmit more street noise, etc.

      There's also the consideration that windows that get a lot of sun in the winter are good because of the solar gain, but windows that get a lot of sun in the summer are bad because of the solar gain.

      Sun travels at a different angle between winter and summer. It's reasonably simple to have an awning that results in shade over window in summer and direct sun in winter. Heck, windows around here reflect most of the sun during the summer and transmit it in winter. Thin-film coatings and all that.

      Upgrading windows up from single pane is the best livability improvement you can do to your house after adding attic insulation so it's at least R-40 (yes, this is important in ALL places, including Florida).

      • (Score: 2) by frojack on Saturday December 05 2015, @07:40PM

        by frojack (1554) on Saturday December 05 2015, @07:40PM (#272252) Journal

        Wait, you seem to be mixing and matching numbers from single pane (which, unfortunately are still quite common in the US) with those of double and triple pane. You've totally glossed over the cost issue.

        Going to triple pane is usually not cost effective vs going to Double Pane.

        In cold regions, such as New England, triple-glazed windows can save 2 to 3 percent of your heating bill, compared with double-glazed windows. From a cost standpoint, it'll take a few decades to recoup the 10 to 15 percent upcharge to go from low-e double-glazed windows to triple-glazed. For example, if you pay $1,000 per year in energy bills, have 20 windows in your house, and 22 percent of your energy is lost through your windows (which is average), then each window is losing $11 worth of energy per year. A triple-glazed window will reduce that loss by about $1, so it'll take 35 years to cover a $35 upcharge for triple-glazing.

        See [familyhandyman.com]

        If you spend that extra money replacing failed double pane (fogged) you will save a lot more.

        New construction or broken window replacement? It probably pays. Arbitrarily replacing: You will never recoop.

        --
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