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Sample Manual J heating and cooling load calculation report
Posted by Allison Bailes on May 23, 2018
When you enter the world of building science — whether through building a house, becoming a home energy rater/building analyst, or just hanging out in cyberplaces like this — everyone talks about the importance of getting actual heating and cooling load calculations based on ACCA Manual J.  A great...
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Oversized air conditioner
Posted by Allison Bailes on May 8, 2018
Many people seem to think HVAC design means you get a load calculation (Manual J in the ACCA protocols) so you know what size system to put in. Hey, that's a great start. It's way better than just using a rule of thumb or Manual E (for eyeball). You don't really want to end up with a ginormous...
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Condensation on stone steps in New Orleans on a February morning
Posted by Allison Bailes on April 18, 2018
If you live anywhere in a warm, humid coastal area, you're no doubt familiar with wet concrete in winter. Some days you walk outside and find the carport slab is soaking wet. How did it happen? Did rain blow into the carport? If it's not rain, is it moisture from the ground that came up through the...
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air conditioner heat pump furnace supply vent register
Posted by Allison Bailes on March 28, 2018
When you embark on the project of educating yourself about building science, one of the first things you encounter is the concept of heating and cooling loads. Every building has them. (Yes, even Passive House projects.) That's why we do heating and cooling load calculations. We enter all the...
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Gas log fireplaces are more efficient - and more dangerous - when they're not vented. But are they more efficient than a condensing furnace?
Posted by Allison Bailes on March 13, 2018
One of the primary benefits of an unvented gas fireplace is that you don't lose any heat up the flue. That's because there isn't a flue, of course. That's one of the main reasons supporters of unvented gas fireplaces use to sell a product that's banned in California and Canada. "Hey, 100% beats 95...
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loaa 2 insulation blown cellulose complete coverage energy vanguard
Posted by Allison Bailes on February 27, 2018
I love insulation. It's a wonderful thing because it saves energy. It makes buildings more comfortable. And it's pretty inexpensive considering how long it lasts (or should last). I get asked a lot for my opinion on the best insulation to put in a building and my answer is straightforward: A well-...
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Insulation on flex duct (Photo by Mike MacFarland, used with permission)
Posted by Allison Bailes on February 13, 2018
If you know a little building science, you've no doubt seen a lot of problems that occur with air distribution systems. Ducts just don't get anywhere near the attention they deserve in most homes, partly because they're hidden from view. I've written about ducts quite a bit here and have shown...
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Condensation in the bathroom after the morning shower
Posted by Allison Bailes on January 22, 2018
You may have heard or read somewhere that you should run your bathroom exhaust fan whenever you take a shower and then let it run for a while after you're done with the shower. Showers increase the humidity in the bathroom. Sometimes it gets high enough to cause condensation to appear on the mirror...
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Water vapor and cool surfaces are a bad combination
Posted by Allison Bailes on January 17, 2018
Because I've written so much about moisture in buildings, I get a lot of questions on the topic. Some are about walls. Some are about the attic. Some are about windows. Some are about the crawl space (which generates the most questions on this topic). The key to answering a lot of those questions...
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ventilation energy enthalpy recovery ventilator erv humidity
Posted by Allison Bailes on January 9, 2018
When I woke up Saturday morning, the temperature outdoors was -40 degrees†. The wind chill was -100 degrees! It was just unbelievably, impossibly, inhumanly cold outside. Fortunately, that was on a mountaintop in New Hampshire and not where I was. I happened to have woken up on a mountaintop in...
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