Building Science

Today just feels like a good day to talk about shiny stuff. Radiant barriers are a green building product with a lot of sex appeal, if that's possible for construction products. People get really crazy about attics, though. (Don't get me started about powered attic ventilators!) Maybe brains have a tendency to overheat when discussing them. The general category of radiant barriers is an area of great hype and misunderstanding, so I'll tell you what I know, explain the basic physics, and give you a couple of links to some great resources for more information.

Here's another rant that goes in my “drives me crazy” bin of articles. I'm in good company, too. Another article that ran at Green Building Advisor recently discussed making the choice between an air-source heat pump and a ground-source (a.k.a. “geothermal”) heat pump.

With the recent heat wave that set all kinds of records across the US, including an all-time high of 106° F here in Atlanta, air conditioning has become quite the topic of conversation. Why, just yesterday I overheard two little old ladies* on a park bench debating thermostatic expansion valves versus capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. tube metering devices — and almost coming to blows over it!

On the 1st of this month, the Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. new homes program moved fully (well, almost) into the much more rigorous set of guidelines called Version 3. There's been a lot of discussion on the the transition for the past three years, when the Energy Star team at the U.S. EPA first started vetting the update with HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5. raters and home builders. In case you've ignored or haven't heard much about it yet, here's a quick overview of what's new:

A lot of home builders and homeowners are getting certified home energy ratings to find out how efficient their homes are. There's also a lot of buzz about HERS ratings, with builders looking at them as a tool for marketing their homes.

Smart people in the home-building industry have a saying about codes: A code-built house is the worst house allowed by law. The implication behind that statement is that if all you're doing is meeting the code, you're probably short-changing the people who will live in the house. The folks at the International Code Council (ICC) are doing their best to make sure that that barely-legal house is worth living in.

We're making progress! With the all the emphasis on energy codes and energy efficiency programs like Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. New Homes, more homes are getting Manual J heating and cooling load calculations these days. The intent is for the heating and cooling systems to be sized properly because oversized systems have problems (poor dehumidification, short cycling...).

I grew up with really bad asthma. Not being able to get enough air into your lungs, in case you haven't experienced it, is pretty scary. I remember lying in bed during one asthma attack, gasping for air, wheezing loudly, and feeling like I was going to die. A trip to the hospital for a shot opened up my lungs again that night, but I continued to suffer asthma attacks even into my mid-twenties.

Let's get back to the Pretty Good House concept now. Last month I wrote part 1, called Is the Pretty Good House the Next Big Thing?

Whether you want to build a new home or fix an old one, the way to ensure that you get the best performance is to do the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials. right. That means installing the right amount of insulation and installing it well, and it means having an air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both. with minimal leakage. But how do you know when you've done enough air sealing? How tight is tight enough?