## The Real Reason for HVAC Design — It's Not Sizing

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...

## The Contractor's Fear of Third-Party HVAC Design

Posted by Allison Bailes on September 28, 2017
What if a builder refused to build from plans drawn by an architect? What if a tile installer refused to implement designs handed to them and instead did their own thing? What if an HVAC contractor told a potential client they wouldn't install a system designed by a third party to ACCA protocols?...

## Duct Design 5 — Sizing the Ducts

Posted by Allison Bailes on June 9, 2017
To this point in our little series on duct design, we've been calculating intermediate quantitites: available static pressure, total effective length, and friction rate. Today we use all that to find out how big the ducts need to be. We're following the Manual D protocol for duct design, a standard...

## Duct Design 4 — Calculating Friction Rate

Posted by Allison Bailes on June 1, 2017
Today's installment in the duct design series is a simple one. It's just a straightforward calculation that gives us the design friction rate from the two quantities I discussed in my last two articles. In part 2, I told you about available static pressure (ASP). In part 3, I covered total...

## Duct Design 3 — Total Effective Length

Posted by Allison Bailes on May 30, 2017
Today we move another step down the road of duct design. I started the series with a look at the basic physics of air moving through ducts. The short version is that friction and turbulence in ducts results in pressure drops. Then in part 2 I covered available static pressure. The blower gives us a...

## Grading an Attempt to Get Ducts Inside Conditioned Space

Posted by Allison Bailes on September 7, 2016
There's a ton of new construction and remodeling going on in Atlanta. On a lot near where I live, a developer tore down the old house and is building two new ones. This weekend, I took the opportunity to check out their progress on the first one and saw the mechanical system roughed in on the first...

## The Evolution of Passive House in North America

Posted by Allison Bailes on July 1, 2016
In 2002, Katrin Klingenberg introduced the passivhaus program to North America when she built the Smith House in Urbana, Illinois. She had come to the US from Germany, where she studied architecture and got involved with passivhaus. But is this really where it all began?

## Design Flaws That Can Rot Your House

Posted by Allison Bailes on May 2, 2016
Most of the moisture management problems I've written about here are ones that occur because of poor installation. When builders don't integrate window flashing with the drainage plane, for example, water can find its way in and rot out the window framing. Sometimes, however, architects make it...
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## The Surprising Building Science History Behind the Revolving Door

Posted by Allison Bailes on January 29, 2016
Revolving doors have been around for a century and a half. You see them at the bottom of tall buildings, which tells you something right there. They weren't invented merely to function as a way to enter and exit these buildings. There's a building science reason behind their invention. In fact, the...