Building Science

Proper Sizing Isn’t the Real Reason for HVAC Design

Posted on May 9, 2018 by Allison A. Bailes III, PhD

Many people seem to think HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. 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).

But there's so much more to real HVAC design than simply finding out how much heating and cooling a building needs when it's at design conditions. And we might as well start with the fact that my first statement is incorrect: The load calculation does not tell you what size system you need.

Understanding and Measuring Mean Radiant Temperature

Posted on April 26, 2018 by Peter Yost

All the way back in 1993, one of my first research projects at the NAHBNational Association of Home Builders, which awards a Model Green Home Certification. Research Center was assessing the performance of radiant ceiling panels for the Department of Energy’s Advanced Housing Technology Program. (The final report was titled )

Sweaty Southern Slabs

Posted on April 25, 2018 by Allison A. Bailes III, PhD

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 concrete? Could it be condensation from the water vapor in the air? Let's take a look.

HVAC Design Requirements in the International Building Codes

Posted on April 11, 2018 by Allison A. Bailes III, PhD

Building codes, especially those related to energy efficiency, have improved a lot over the years. With building enclosures, this has made a big difference. We now have more insulation, less thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. , and tested air barriers. On the mechanical side, the improvements are significant — reduced duct leakage and mechanical ventilation in airtight homes — but there's still a gap between some code requirements and what's being installed.

Converting Heating and Cooling Loads to Air Flow Needs

Posted on March 28, 2018 by Allison A. Bailes III, PhD

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 projects.) That's why we do . We enter all the details of the building, set the design conditions, and get the heating and cooling loads for each room in the building.

Wingnut Real-World Testing of Basement Waterproofing

Posted on March 22, 2018 by Peter Yost

Back in May 2017 I wrote a blog about negative side waterproofing (NSW). But I was still feeling troubled. The standardized test for NSW from the U.S. Army Corps of Engineers (“Standard Test Method for Water Permeability of Concrete”) is frankly really complicated; the schematic seems impossible to decipher (see the Image #1 at the right). Instead of using this test, could we do a real-world, Wingnut-style test for negative-side waterproofing?

Is a Ventless Fireplace More Efficient Than a Condensing Furnace?

Posted on March 14, 2018 by Allison A. Bailes III, PhD

One of the primary benefits of a ventless gas fireplace is that you don't lose any heat up the flue. That's because there isn't a flue, of course. (The potential problems with indoor air quality, however, outweigh any benefits, so don't run out and buy one just yet. Or ever.) That ought to make it a winner for heating efficiency in comparison to any vented heating appliance, such as furnace or boiler. Even the highest efficiency condensing furnaces still lose some heat in the exhaust gases that go up the flue.

Advice for Getting the Most Out of Your Insulation Contract

Posted on February 28, 2018 by Allison A. Bailes III, PhD

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-installed insulation is the best. I like fiberglass. I like cellulose. I like spray foam. I like mineral wool. I like blown, sprayed, batt, and rigid insulation.

Installing Insulation With the X-Floc Ventilated Dry Injection System

Posted on February 22, 2018 by Peter Yost

At the end of my recent blog on Kooltherm rigid phenolic foam insulation, I mentioned that the roof and wall assemblies at an energy retrofit project in Brattleboro, Vermont, were insulated with cellulose by a company called .

Is R-8 Duct Insulation Enough?

Posted on February 14, 2018 by Allison A. Bailes III, PhD

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.

I've written about ducts quite a bit here and have shown problems resulting from poor design and installation. We all know how stupid some of those problems are. So today I'm going to talk about a problem that doesn't get nearly enough attention: duct insulation — even when the design and installation are perfect.

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