High-Performance Dehumidification

Slideshow (click to launch)

The basement of our well-insulated and air-sealed 100+-year-old home is dry, but enough moisture (as vapor) makes its way through our concrete walls and slab that dehumidification is a must from about April through October. Dehumidification comes with a pretty big energy penalty, so I am proactive in managing this load: when I see that the weather and forecast is for a dry day, I start the day by opening up our half-dozen basement hopper windows, and then close them up at the end of the day (see Image #1 in the slideshow). This just takes a couple of minutes, and Mother Nature manages our basement humidity. But there are many non-heating-season days when we manage the basement humidity with our off-the-shelf 50-pint Whirlpool dehumidifier (see Image #2 in the slideshow). It has done a fine job, but I got to wondering just how old the unit was, and how its efficiency was faring. The unit also seemed quite noisy (but honestly, maybe it was always that way). I took the housing off the face of the dehumidifier unit to inspect the coils (see Image #3) and to check out the specs (see Image #4). The coils were a bit dirty, but easily cleaned. What really surprised me was that the unit was quite a bit older than I thought (manufactured in 2003, since the “P” in the serial number stands for a manufacturing date of 2003; see Whirlpool Date Codes) and its Energy Factor was just 1.35 (L/kWh: liters per kilowatt-hour) — not even Energy Star. How has this unit’s efficiency held up over the many years?

Benchtop measurement of a dehumidifier’s Energy Factor

There is of course a standard test for Energy Factor; it used to be ASTM C 749 (as cited on the Whirlpool unit’s spec label — Image #4) but now is ANSI/AHAM DH-1 (as detailed in Appendix X to Subpart B of Part 430 – Uniform Test Method for Measuring the Energy Consumption of Dehumidifiers). My version of the test was to hook up a Kill A Watt meter to the dehumidifier, and collect the condensate over a 24-hour period. I did that for the Whirlpool unit in our basement under these conditions:

• Initial basement temperature and relative humidity: 78°F/68% (as measured by a HOBO datalogger; see Image #5)
• Intermittent operation over the 24 hours, with constant operation “setting”
• Average operating power: 590 watts (see Image #6)
• Test period: 6 a.m. August 14 through 6 a.m. August 15
• Output: 6.3 liters
• Input: 4.32 kWh

Conclusion: The benchtop Energy Factor is 1.47 L/kWh. Wow – pretty impressive efficiency considering the unit's age. But it started out as pretty unimpressive. (A current version of this same Whirlpool dehumidifier would be the Whirlpool WHAD501AW. It’s EF is 2.0 and it retails for about $200.) There is a long list of conditions that make my benchtop test different than a laboratory test done to all the specifications of a standard. The most meaningful comparison will be to the new high-performance dehumidifier, coming up next.

High-performance dehumidifier

For the last twenty years at least, the U.S. company Thermastor has been a key contributor to the Building America program, quietly but steadily educating builders about the importance of managing latent load, particularly in efficient homes with longer shoulder seasons. As part of my work with Hanley Wood University’s Homebuilding Crossroads workshops , I have been doing a lot of tech-talk with Nikki Krueger at Thermastor. When she asked how I was keeping my own basement dry and I described my aged Whirlpool unit, she said, “Want to give our new Santa Fe Advance 100 a try?” I could see benchtop testing written all over this offer. So, earlier this week I installed the Santa Fe Advance 100 (a dehumidifier that retails for $1,799) in our basement (see Image #7). I did an identical benchtop Energy Factor test with the Advance 100:

• Initial basement temperature and relative humidity: 78F/68% (as measured by a HOBO datalogger; see Image #8)
• Intermittent operation over the 24 hours, with setting RH = 60%
• Average operating power: 660 watts (see Image 9)
• Test period: 6 a.m. August 15 through 6 a.m. August 16
• Output: 13.5 liters
• Input: 5.04 kWh

Conclusion: The benchtop Energy Factor is 2.68 L/kWh. Pretty impressive efficiency. And pretty much in line with the EF reported on the SF Advance 100 spec sheet. But how else is the Advance 100 different or better than an off-the-shelf standard dehumidifier, such as the Whirlpool I had in my basement for all those years?

Beyond straight dehumidification

You can go to the Santa Fe website and get their version of the differences, but here is what I found:

• Much quieter operation – the fan motors are higher quality, with less vibration;
• Made mostly of metal, not plastic – the Advance 100 is a sturdier (and heavier) unit;
• Includes air filtration – MERV 8 pleated filter is very easy to change out;
• Includes "circulation" mode – a mode that pushes the fan to high speed to increase mixing and to even out the space’s relative humidity and temperature;
• Can be ducted – the unit is designed for and capable of being ducted so that the unit can be in a different space than the space it serves;
• Accurate sensors – the LED readout-panel on the Advance 100 was always within 1°F and 1% RH of the Hobo data logger in my basement;
• Remote Internet-based operation (more on this below);
• Made in U.S.A. – pretty rare these days, and for me it translates into very responsive technical service.

As with most modern new appliances, the Advance 100 is tied to the Internet. You download the Santa Fe Connect app, and from your phone you can see and set the operation of your Advance 100. Every half hour it updates weather conditions for your zip code, and the app sends alerts if there is anything awry regarding your setpoint and current RH (see Images #10 and #11). Very cool! Now if I can just get an app that will open and close my basement windows when the weather is nice and dry….