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Open Cell vs Closed Cell in Atlanta, GA.

- Gil Morelle
Alpharetta, ga

This is a very complicated problem that can have different answers depending on the remaining life of the roof, leakiness of the roof, average relative humidity of the conditioned space, and etc. Luckily, in Atlanta you really only need to worry about making sure the roof won't leak. Condensation shouldn't be a big concern unless you have a really shaded roof that allows snow to collect for extended periods of time. Southface, an organization in Atlanta, may be a local resource for you, too.

- Adam Lee, Boone, NC

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Commercial Energy Star Metal Windows

- Robert Sheriff
Dover, nj

Most companies like Pella or Anderson make windows in 1" increments at no additional charge so custom windows do not always mean more money. Trim details can accomplish any minute differences in window sizes. I would be interested to see what you are calling a "commercial metal window" If you mean a glazed storefront system that is totally different from an operable metal window. Good luck!

- Tony Griffy, Chattanooga, TN

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Wind vs. Solar and Passive Solar Design

- Jared W., Portland, OR

Jared - There is an organization called Passive House Northwest that could provide benefit to you. Also, the Passive House US conference will be held in Portland November 5th and 6th - it is focused on the new Passive House certification standard, but will offer many resources regardless of certification issues. For a community near Yakima WA that I recently designed, there is substantial wind, but we are most likely going with grid-tied, free-standing solar as a lower-cost-and-maintenance option for the residents. It will also follow proper orientation and build-tight-insulate-right recommendation of Steve above - essential. Agree with Tony - it depends on your site.

- Robin Rogers, Kirkland, WA

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How can I tell if solar hot water would be good for my home?

- John B., Richmond, VA

Pretty accurate information, but I've seen some of the numbers play out a little bit less optimistically in some real world applications.

- Adam Lee, Boone, NC

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How can I tell if solar panels would be good for my home?

- Sandi H., Sacramento, CA

There are a number of factors that impact the feasibility of installing solar panels for a home. These include site factors such as sun exposure, orientation and tilt. Also, average monthly utility costs and the percentage of these that you would like to be provided by solar power need to be considered. An average home can typically generate around 50% of its energy consumption from solar PV without too many major changes. However, making energy efficiency improvements first can result in additional savings and decreased system size. Last but not least, cost varies greatly from location to location based on the local market as well as available federal, state, and local incentives. You can find more information on these incentives in the Tax Credits section of the Resources page of the GPD website. It's always a good idea to contact a solar panel professional in your area for specific recommendations.

- Renee J., Los Angeles, CA

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What is an infrared camera?

- Jim T., New York, NY

Human eyes are able to see only a small fraction of the electromagnetic spectrum know as visible waves. Other parts of this spectrum include x-rays, UV, infrared and radio waves. Whereas human eyes and digital cameras pick up the images from the visible portion, an infrared (IR) camera picks up images from the infrared portion of the spectrum. The hotter a material is, the more infrared it emits. As such, infrared images are an excellent way of locating where heat is flowing that otherwise would be invisible. This information is crucial when making decisions on home or building energy conservation decisions because it gives your a picture of the building's weak spots. For example, this information can be used to see behind walls where insulation is missing or additional insulation is needed.

- Jeremiah A., Charlotte, NC

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What is a blower door?

- Jim T., New York, NY

A blower door is a fan that is used by energy auditors to locate and quantify air leakage in a home or building. It works by pressurizing or depressurizing the building in a controlled manner while measuring the flow through the fan. Air leakage, total hole size and other values can be derived from this flow. A number of other tests can be performed in conjunction with the blower door that can measure and test for duct leakage, air quality problems, and more. After weatherization work is complete, the blower door test can be performed again to demonstrate the improvement made and ensure adequate natural ventilation.

- Jeremiah A., Charlotte, NC

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Green Insulation: spray foam or dense packed cellulose?

- Megan A., Atlanta, GA

This is another question that has attracted a lot of interest in recent years. The answer depends on what you mean by "better." Dense packed cellulose often has a slightly higher R value (the measure of how well a material performs at blocking heat flow) than open cell spray foam. Closed cell spray foam has an R value well above both dense packed cellulose and open cell spray foam. When it comes to the sustainability of the material itself, cellulose will break down much more easily than spray foam. It can also have more potential to be converted/recycled to other uses. Other variables that can come into play are how the material responds to fire, moisture and pests. Many of these factors have varying degrees of significance depending on your location. Consult with a local green insulation contractor to see which insulation material is best for your application.

- Kevin T., St. Louis, MO

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Spray foam: open cell vs. closed cell?

- Tommy D., Santa Fe, New Mexico

This question is becoming a classic debate in the spray foam world. The R value of closed cell spray foam insulation is higher than that of open cell, meaning you would need less to achieve the same degree of thermal protection. Open cell can allow air and moisture to pass through whereas closed cell does not. Which of these scenarios is preferable will depend on a number of factors such as your climate zone (e.g. hot, hot and humid, etc), and the location of the insulation (e.g. attic, walls, crawlspace, etc). I'd consult with a local spray foam insulation contractor to see which is best for your application.

- Aaron S., Austin, TX

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