Building Science

Heating Degree Days Drop Again in 2017

Posted on May 24, 2017 by Allison A. Bailes III, PhD

We've had some beautiful cool weather here in Atlanta this spring. It's about 50°F outdoors as I write this, one week into the month of May. The high yesterday was only about 70°F.

We're getting a few more heating degree days (HDDThe difference between the 24-hour average (daily) temperature and the base temperature for one year for each day that the average is below the base temperature. For heating degree days, the base is usually 65 degrees Fahrenheit. For example, if the average temperature for December 1, 2001 was 30 degrees Fahrenheit, then the number of heating degrees for that day was 35.) in the middle of May. (Heating degree days are really just another way at looking at temperature, which I explained in more detail in a look at the fundamentals of degree days.) We occasionally pick up some HDD even in July and August. But it's the winter HDD that matter for heating — and that give us a clue about the climate.

Installing Basement Waterproofing from the ‘Negative’ Side

Posted on May 18, 2017 by Peter Yost

Negative-side waterproofing (NSW) is a tough topic that I have frankly been dancing around for quite some time. Manufacturer claims and homeowner anecdotes of successful interior waterproof solutions for basement walls and slabs did not completely add up. But I did not think that I understood the topic or the physics well enough to challenge the claims or explain my skepticism.

Three Easy and Essential Advanced Framing Techniques

Posted on May 17, 2017 by Allison A. Bailes III, PhD

Most new homes in North America are built with sticks. The early home builders used bigger pieces of wood — timbers — and when the smaller dimensional lumber that we use so much today hit the market, they scoffed at those new-fangled little woody things, calling them sticks. Now our home construction industry is full of people who do stick building and the home you live is most likely stick-built. And sadly, many of the techniques used to build many of those homes are the same used before we started insulating them.

The Difficulty of Updating Georgia’s Energy Code

Posted on May 10, 2017 by Allison A. Bailes III, PhD

Seven years ago, Georgia led the nation. Yep. We were the first state to adopt an energy code that made blower door testing mandatory. All new homes built in the state had to show through performance testing that they had an air leakage rate of less than 7 air changes per hour at 50 Pascals of pressure difference (ach50).

The Energy Conservatory’s New Blower Door Kit

Posted on April 27, 2017 by Peter Yost

I don’t do blower door work every day, but I do enough of it to appreciate the attention to detail that The Energy Conservatory (TEC) built into its new blower door kit. The kit features a digital pressure and air flow gauge, the DG1000.

Questions to Ask Your Prospective Builder

Posted on April 26, 2017 by Allison A. Bailes III, PhD

You're having your dream house built. You're into the design phase, working with an architect or looking through collections of house plans. You're doing your homework, trying to find out how to ensure you get a top quality house. And that's when you run into all this stuff about building science, high performance homes, HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. design, blower door testing, and the like. Now you're hooked.

The Hidden Flaw in Some High-Efficiency Furnaces

Posted on April 19, 2017 by Allison A. Bailes III, PhD

You can tell how energy-efficient a furnace is by its official efficiency rating, the Annual Fuel Utilization Efficiency(AFUE) Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. (AFUEAnnual Fuel Utilization Efficiency. Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. ). It's a measure of how much of the heat originally in the fuel that's being burned is available for delivery to the home. The more heat that gets lost up the flue or through the cabinet, the lower the AFUE.

But that rating doesn't capture all the ways a furnace can lose efficiency. Some, like how well the heat gets distributed to the house, aren't related to the furnace itself. But there's one big one that is related to the furnace.

Five Ways to Do Balanced Ventilation

Posted on April 12, 2017 by Allison A. Bailes III, PhD

Ventilation is a great thing. Bringing outdoor air into the home and exhausting stale indoor air improves indoor air quality. Well, most of the time, anyway. Sometimes the outdoor air quality is worse than indoor air. Sometimes you bring in too much humidity and start growing mold. And sometimes you bring in the wrong outdoor air. But the issue of outdoor air vs. indoor air is a topic for another article.

The Home Performance Forum Has Launched!

Posted on March 29, 2017 by Allison A. Bailes III, PhD

The Internet age has made it easy to find information. Occasionally you can find some that's even true. That's where it becomes helpful to have someone more knowledgeable than yourself to be able to ask for advice and input on stuff you read online, get feedback on ideas you'd like to try on a project, or discover what cool things other home energy pros are doing.

Pete’s Puzzle: Fanciful Fuel

Posted on March 16, 2017 by Peter Yost

A new client called me, saying that his insulation contractor urged him to contact me about some moisture problems in the home before they actually embarked on a major energy upgrade. (That was gratifying.) The home was actually moved many years ago off of a failing rubble foundation to a new concrete masonry unit (CMUConcrete masonry unit. Precast concrete block used to build walls. CMUs have hollow cores that can be filled with concrete onsite for additional reinforcement. The use of stronger, more lightweight types of concrete such as autoclaved aerated concrete (AAC) is becoming increasingly popular in CMU manufacture. ) foundation on a different site.

Image #2 (bottom of page) shows the home from the front. Image #3 shows the bare CMU on the above-grade portion of CMU foundation.

But it is Image #1 (right) that is the real puzzle. Here are the puzzle pieces:

Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!

Syndicate content