Energy Performance FAQs

• Should I replace my windows?
• My attic and basement aren't part of my living space; do I really need to insulate them?
• Doesn't cellulose insulation settle over time, leaving my walls under-insulated?
• Isn't it a bad thing to have a tight house? Doesn't a house need to breathe?
• When should I install a PV system or wind turbine?
• Are there any rebates or financial aid for weatherization work?

Should I replace my windows?
The short answer is "probably not"—at least not as your first energy improvement measure—or possibly even second or third. Damaged or rotten windows should be replaced if they can't reasonably be repaired, and steel-framed windows are also usually good candidates for replacement. Although windows are a source of substantial heat loss (often representing around 20% of the heat loss of an older home), the difference in performance between an old window with a storm (R-2.5, roughly) and a new double-pane replacement window with low-e glass and argon infill (roughly R-3.5) is relatively small and the cost per square foot is high. Often old, wood-framed, double-hung windows can be weatherstripped to perform pretty well. Storm windows will offer a further improvement, especially if you go to the extra effort of specifying low-e glass in the storms (which will yield a slight blue tint to the windows, but a quick pay back for the extra expense). Replacement windows, if installed carelessly, may yield very little improvement in performance. The best choice for window replacement, triple-glazed with two low-e coatings, is still very expensive in the US but will likely go down as demand increases.

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My attic and basement aren't part of my living space; do I really need to insulate them?
It's no longer adequate to focus solely on insulation as a means of reducing heat loss. 30%-50% of a home's heat loss is a result of air infiltration alone. By thinking "insulation and air-sealing," instead of just "insulation," it becomes more understandable why you often get better results from insulating the rafters rather than the attic floor, and the basement walls rather than the basement ceiling. Your attic floor has dozens if not hundreds of holes in it—pipe and wire chases, ductwork, access hatches, chimneys, vent pipes. Your roof, however, has very few holes in it—probably just a vent or two and a chimney or two. It's going to be far easier to air-seal the rafter plane than the attic floor plane as a result. Additionally, this strategy will move any mechanical equipment—furnace or boiler, air handler, and pipes and ductwork—from "outdoors" (outside the insulation) to "indoors" (inside the insulation), which will improve their operating efficiency considerably. This holds true for the basement as well—insulating your basement ceiling is roughly analogous to moving your furnace and water heater into the backyard.

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Doesn't cellulose insulation settle over time, leaving my walls under-insulated?
Cellulose is a great insulation material that has been used in residences since the 1930's. Made of recycled newspaper, it provides an excellent thermal barrier while staying one of the most environmentally friendly insulation materials available, and it is fire, mold, and pest resistant. Dense-packed cellulose (meaning about 3.5 pounds of material per cubic foot of volume) can also act as a very effective air barrier. During the 70's and 80's, cellulose developed a slightly damaged reputation for "settling" over time—that is, the material in the wall cavity appeared to sink, leaving uninsulated voids at the top of the cavity. Today's cellulose is manufactured by breaking recycled newspaper down into a fibrous material, which interlocks as it's blown or sprayed into a cavity, providing much more effective coverage. In addition, the cellulose is (or should be) packed into the cavities at a higher density; the wall or ceiling is actually under a slight pressure from the amount of material in the space. The cellulose cannot settle because there is no air space left for it to settle into. In this day and age, if there is any settling of cellulose, it is due to a poor installation job, not a property of the insulation material.

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Isn't it a bad thing to have a tight house? Doesn't a house need to breathe?
The tighter the house, the greater the energy savings. At the same time, houses also need adequate ventilation to provide fresh air for occupants and to remove excess moisture and pollutants. In a leaky house, the "natural" air change is unreliable, varying with wind and temperature, and can even stop at times. In addition, since there is no control over the source of ventilation through air leaks, the outdoor air entering a home's living space often infiltrates through areas that are potentially dirty, damp, moldy, and possibly contaminated with soil gases such as radon, or toxins such as pesticides and herbicides. As a house becomes more air-sealed, it can no longer rely on the air leaks in the building envelope to ventilate the living space. So, yes, houses do need to "breathe," but they need to "breathe" in a controlled, engineered fashion. As you tighten your home, at some point you will need to install a mechanical ventilation system. This system should both provide clean fresh air from a controlled source, and exhaust stale air, pollutants, and excess moisture, while staying appropriately sized to the home. Heat recovery ventilation systems (HRV) have the added benefit of recovering some of the heat from the exiting old air, further reducing energy loads.

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When should I install a PV system or wind turbine?
In most instances, installation of a renewable energy source system, such as solar hot water or PV, should only be considered after the building has been renovated to reduce its energy load as much as possible. A very rough rule of thumb is that you should get your household energy usage down to about 40,000 Btu per square foot per year before considering renewables (Byggmeister can provide help in calculating your Btu/sf/yr energy usage if you'd like). Many houses are poor candidates for photovoltaic systems or solar thermal because of poor solar orientation or significant tree coverage; even more houses are poor candidates for wind turbines. So-called "geothermal" systems (ground-source heat pumps) are not always as green as they seem—they can be expensive; it's often hard to verify the operating efficiencies, which means those efficiencies are sometimes over-stated; and because they often replace a gas- or oil-fired system with an electrically powered system, they can increase household greenhouse gas emissions by as much as 40%, as a recent Minnesota study indicated.

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Are there any rebates or financial aid for weatherization work?
National and state governance bodies are beginning to provide financial incentives to help homeowners improve their home's energy efficiency. By state mandate, NSTAR and National Grid offer 75% off (up to $2,000) the total cost of insulation upgrades and air sealing for their natural gas and electric customers. Federal tax credits for energy efficiency measures are available at 30% of the cost, up to $1,500, in 2009 and 2010 (for existing homes only) for: windows and doors, insulation, roofs (metal and asphalt), HVAC, non-solar water heaters, and biomass stoves. Additional federal tax credits for energy efficiency are available at 30% of the cost, with no upper limit through 2016 (for existing homes and new construction) for: geothermal heat pumps, solar panels, solar water heaters, small wind energy systems, and fuel cells. You should also work with your tax advisor for other possible credits for energy improvements to your home and to confirm your eligibility to take advantage of each credit (check out www.irs.gov for new credits or developments). Finally, National Grid and NSTAR are both developing pilot programs that provide more substantial funding (on the order of $35,000 for one such program, for instance) for deep energy retrofits on existing homes. Byggmeister is on the approved contractor list for these programs; if you believe you have a qualifying project we'd be happy to work with you to develop the plans and the application.

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