10 Titus Road
P. O. Box 438
Energy Efficient Retrofits
While renewable energy equipment (solar, wind, geothermal) is exciting and worth considering, the mundane truth is that the biggest payback for most houses is in conservation of energy, achieved by insulation, control of air infiltration, and higher performing windows.
A building envelope upgrade is not cheap; but when your goal is to increase energy and material efficiency, you will also enhance your home's value and lower its operating costs. If, instead of an ordinary paint job requiring extensive preparation of the old surface, you stripped the siding, considered the vapor barrier and added a good air infiltration barrier and rigid foam insulation on furring, then re-sided and painted or sealed, you would end up spending many times the cost of painting. But you would also have new siding with zero depreciation, a reduction in the use of heating energy, weather and even interior surfaces that are likely to last longer due to better control of moisture-laden air in the wall, and perhaps better indoor air quality if there had previously been a mold problem associated with moisture in the wall cavity.
Insulating and air sealing must be done with proper care for interior moisture control. During heating season in the northeast, indoor air usually holds more moisture than outdoor air. If any of the indoor air is allowed to pass far enough into the insulation, it will cool down to the dew point, dropping beads of water into the insulated cavity, and thereby setting up conditions for rot, mold, and reduced insulation performance. The warm moist air must hit a moisture barrier near or at the warm inside face of the building in order to prevent this. At the same time, the cool outside face of the building, while it must stop wind and shed water, also needs a high enough permeability rating to "breathe," allowing any moisture that does exist in the wall cavity to eventually dry out.
When a building is super-insulated and properly air- and moisture-sealed, a controlled method of exchanging the indoor air for fresh outdoor air should be selected for control of excess humidity and for occupant health. This can be done with a relatively inexpensive heat exchanger which uses the heat from exhaust air to preheat the incoming fresh air. It is also possible to incorporate bathroom fans into this system.
Before doing any significant work on your house involving envelope components, consider putting energy and durability upgrades into the planning mix. But remember that some building science is involved in building envelope upgrades for management of moisture, air infiltration, energy use and indoor air quality. And bear in mind that some costs can be partially offset by federal and state incentive programs and rebates.
This project presented an interesting insulation history. Built around the 1920's, the house had originally employed an even older and more outdated form of insulation that involved creating a second barrier of plaster over lath boards. This method was called "back plastering", as written by Francis C. Moore in his book , "How to Build a Home", published in 1897 and described as, "an extra coat of rough brown plaster on lath between the outer sheathing and the inner or finish plaster, thus securing two air spaces."
The walls of this house were constructed with clapboard siding nailed directly to the studs (not recommended), then a layer of lath boards nailed to blocks between each stud bay, with a layer or two of plaster applied directly to the lath. Subsequently, the stud bays were filled (if at all) by sprayed in cellulose (shredded newspaper) which had only partially served its purpose. In many areas the insulation had not even reached stud bays that were cut off by blocking. Even a small void in an insulating barrier can cause great loss of its overall value.
Our crew removed all of the old blown-in cellulose, as well as the barrier of plaster and lath, to create as much space as we could to fill with foam insulation (we got an average thickness of 4 1/2" of foam), creating an R-value of between 24 and 25 well above code requirements. Along with adding insulation, plywood, and new siding, the crew was able to uncover and address rot issues that were rampant in the sill of the aging house, and inaccessible prior to stripping the siding. So not only have we been able to upgrade the quality of insulation, but also fix the framing issues and protect it with new plywood and siding and secure the house's sill.
This all added a good deal to the workload, and raised the cost of the project, however the owner is getting the security of a fully and well insulated house that will prove more efficient and economical as energy costs rise. As Mr. Moore said of the outdated insulation method, "...it will keep out the heat of the summer and the cold of winter, while the extra expense will not be great and will be fully justified by the comfort secured for the entire lifetime of the building." He had the right idea, but building techniques have come a long way since then. Now this house, properly maintained, will stand the test of time.
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