Freeze Warning! The Admission of Incompetence
It's "Freeze Warning" time of year again. We had our first freeze of the winter here in Atlanta last week, and I saw the sign above. I cringe every time I see one of these signs that says "Let faucets…
design
Make It a Mechanical Room, Not Just a Closet
In our HVAC design work, we get sent projects where the client sometimes wants the impossible. They've read enough to know they want the mechanical systems in conditioned space, so they put a tiny little closet somewhere in the house…
![Design Temperature And Degree Days Are Different [Photo By NOAA ESRL, From Flickr.com]](https://www.energyvanguard.com/wp-content/uploads/2021/02/thermometer-cold-design-temperature.jpg)
Don’t Confuse Design Temperature With Degree Days
People new to building science and HVAC are confronted with a lot of terms for things that are related but different. Load and capacity. Energy recovery ventilator (ERV) and heat recovery ventilator (HRV). Hot water heater and cold water heater. …
The Real Reason for HVAC Design — It’s Not Sizing
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…
The Contractor’s Fear of Third-Party HVAC Design
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…
Duct Design 5 — Sizing the Ducts
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…
Duct Design 4 — Calculating Friction Rate
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…
Duct Design 3 — Total Effective Length
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…
Grading an Attempt to Get Ducts Inside Conditioned Space
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…
The Evolution of Passive House in North America
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…