Ask The Guru: Energy Savings
OK, so you want to know more about Energy Savings. First check the questions and answers below and see if your question is already here. There's a good chance that it is. If not, no problem, just use the form at the bottom of the page to send me your most burning question about Radiant Barrier and Energy Savings and I'll send you an answer shortly.
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I live in Atlanta, GA and am considering installing AtticFoil. I have a large home and am trying to compute the energy savings and payback period if I invest in attic foil. My existing electric bill averages $468/month in the winter months when NO AC is used. Therefore, all other months I'm figuring the excess over $468 is due to AC, which in my case is $2,082 annually. My understanding is that most of the energy savings comes from saving on AC and that while attic temps may be reduced by up to 40% only 25% of the AC load is due to the loss of cool air through the ceiling. Therefore, .40x.25= a 10% annual savings or, in my case $200 plus whatever savings I get from reduced heating costs. Am I correct with these assumptions?
Trying to predict savings from installing radiant barrier is kind of like nailing jello to the wall. Here are just a few variables that make predicting savings a challenge: geographic location, size of home, number of stories, shape of home, air infiltration, sun exposure, shading, condition of HVAC system, window exposure, lifestyle, etc. The list can go on and on...
I'm building a new home in souh georgia where the summers get really hot and humid. From what I have read on line I can see that a ridge vent with vented soffits is probably the best way for me to go as far as attic ventalation. Do you agree with that? And what insulation do you recommend?
Without knowing the exact specifics of your attic space and home, I can tell you that many, many people choose to use a combination of soffit venting with a ridge vent. It's a good system ant it requires little to no maintenance. As far as insulation up in the attic - I recommend a radiant barrier closest to the roofline and then either traditional fiberglass or cellulose insulation on the attic floor, between the joists up to the recommended level for your area. This is the most common way to do a vented attic.
In reading your "About" section you mention "I also have knowledge and experience working on new construction projects that are either very high performance or near-zero energy usage." I would enjoy your expertise on this. How about a new section for new construction?
Thank you for the suggestion - I will keep it in mind for future development of this blog. I appreciate the feedback!
Re: Foil wrapped bubble wrap and windows Thanks in advance for answering this. I saw question 83 regarding foil wrapped bubble wrap for insulating windows against heat loss from the inside. My questions are: 1. To keep the heat out, cool in, does the foil wrapped bubble wrap need to be on the outside of the window? 2. If it can be on the inside of the window should there be a space between it and the glass or can it be pushed against the glass and be just as effective? I was thinking perhaps, maybe, the bubble wrap is what provides the space? 3. Regarding products such as Warm Window Insulated Shade System http://www.warmcompany.com/wwtech.html that has a barrier inside it, do you think it is the thickness of the material and it being sealed against the wall that is doing the work or is the product really doing something special? Thanks again.
1. No, it can be on either side.
2. It can be pushed up against the glass.
3. They aren't clear on the layering and I don't see testing on this product. For windows, it's best to go with a tint-like product to preserve the light.