FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In
Job Site Diaries

Revolutionary New HVAC Equipment – A Split Dehumidifier!

By Matt Risinger
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

I grew up in Pennsylvania without an Air Conditioner, and I vividly remember when we got central AC installed when I was in High School (1987 to be exact).  Fast forward 10 years to my first trip to Texas in the late 1990’s (I married a Texas girl) and I remember thinking how COLD most houses were in Texas.  Freaking boiling outside, and an icebox inside.

Why do many Southern US homes keep their thermostat at 68 degrees?  I think it’s because they’re using the AC to deal with humidity issues much of the year.  I’m very comfortable in my house with the T-stat set to 78 as long as the humidity is low.

So…What’s the main purpose of an HVAC system?
1. To Deliver Comfort
2. Delivery that everywhere & evenly in the house (and do it quietly)
3. Be efficient with Electricity (cooling is greater than 50% of energy use for Southern US Homes)

If you’ve followed my blog you’ll know that I think standard HVAC systems are far from delivering on those three goals above. In fact, I think most HVAC systems are missing something.  HVAC+D.  The D stands for De-humidification. You might say, doesn’t the Air Conditioner coil take care of dehumidifying the air? Yes it does, AC’s take care of sensible and latent cooling. Latent refers to the water vapor that’s in the air. However, your AC will only dehumidify when it’s running. (Remember, the air conditioner needs to run longer than 10 minutes before it starts to remove moisture from the air). With today’s building codes requiring a tighter envelope (in Austin we require 5ACH50 on the blower door test), and with the tendency for HVAC contractors (and builders) to choose the next size up in equipment I believe a stand-alone dehumidifier is required.

The “Gold Standard” Dehumidifier I install in my houses has been the Ultra-Aire XT105. This is my favorite model from Ultra-Aire’s great lineup of equipment and works for about 75% of the houses I build.

Ultra-Aire XT105H Dehumidifier I use in most of my houses.

The XT105H is super efficient and removes 105 pints per day while only using 4.9Amps of electricity! But, the one down-side of a Dehum inside your house is that it will heat up the space where it’s running. A Dehum works like a mini-AC all in one box. It uses refrigerant & a compressor just like your AC except that the condenser coil (The “AC” box outside your house) is inside the same box as the cold evaporator coil. Fine Homebuilding has a terrific “How it Works” article I’d recommend reading in the May 2014 issue. When the XT105 runs it brings down the humidity inside the house but it also adds some heat.

Ok, so what makes the new Ultra-Aire SD12 so revolutionary? The big deal about the SD12 is that they’ve moved the Condenser coil outside the house! That means that there is no added heat inside the house. It also means that the SD12 provides some sensible cooling and basically acts as a first stage Air Conditioner! The SD12 removes 184 pints/day while providing 4300 BTU/hour of cooling. That’s equivalent to a 1/3rd Ton AC which is super helpful in the hot/humid South.

I’m about to install my first SD12 in a house I’m building on Lake Austin. The house is primarily a weekend and vacation house which makes it the ideal candidate for the SD12. I’ll coach my clients to keep their house thermostat set to 90-92 degrees while they aren’t there, and the SD12 will be set for 50%RH (all year). The SD12 will keep the house air dry/dehumidified, and will provide some cooling too! This house where I’m using the SD12 is a super-insulated & super-tight house so there will be little hot/humid air leaking inside and the house will ride the summer temp spikes with little AC. It’s actually my first Timber Frame project with Bensonwood Homes from This Old House fame.

The stable humidity (thanks to the SD12) in the house will keep mold & dust mite activity low, it’ll keep the hardwoods stable, it’ll keep the caulk in the house stable (greatly reducing cracking), the sheetrock/paint/studs more stable, their piano tuned, and it’ll smell fresh/clean when they arrive on a Friday for the weekend. I’m installing Nest Thermostats so they can grab their iPhone on Friday morning and set the Nest Thermostat to 76 and the house will cool from the 90 it’s been at all week to 76 prior to their arrival. 76 Degrees and 50% RH is ideal for the Hot/Humid South. This SD12 is a game changer and I’m excited to install my first one. I’ll post a video review after we get it installed.

If you’d like to see an XT150 review video here’s one I did two years ago.

Thanks for hanging with me on this long post. I’d love to hear your comments. Drop me a line below and I’ll respond quickly.

Best,
Matt Risinger
– Risinger Homes in Austin, TX

Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.
Be sure to check out my video blog on YouTube, and follow me on Twitter @MattRisinger

Fine Homebuilding Recommended Products

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

A House Needs to Breathe...Or Does It?: An Introduction to Building Science

Allison Bailes is great at explaining complex building science topics in simple terms that anyone can understand. If your goal is a new house or remodel that embodies the best practices that building scientists have to offer, buy this book right away.
Buy at Amazon

Musings of an Energy Nerd: Toward an Energy-Efficient Home

Fine Homebuilding readers know Martin Holladay well and love his practical, cost-effective approach to energy-efficiency and green building. In this book, he walks you through every step of planning an energy-smart home that is healthy, durable, and comfortable.
Buy at Amazon

Pretty Good House

For anyone interested in a sensible and cost-effective approach to designing and building a home that is comfortable, healthy, efficient, and durable, this book is a fantastic starting point (really, it may be all you need!).
Buy at Amazon

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

×

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

New Feature

Fine Homebuilding Forums

Ask questions, offer advice, and share your work

  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

View Comments

  1. ChuckB | Mar 10, 2014 05:41pm | #1

    Hey Matt - I love hearing someone talk about hot weather! And thanks for the review - does any other manufacturer make a similar model, or is Ultra-Aire the only one?

    Chuck Bickford, FHB

  2. Matt Risinger | Mar 13, 2014 08:29am | #2

    @ChuckB: This is the only split degum I know of in the marketplace. Ultra-Aire is the leader in Dehum's for residential use and this new SD-12 is unique out there. I'm excited to get a few installed so I can review them further. It's really first-stage cooling as well as dehumidification. Come visit anytime Chuck! It's going to be 70 today in Austin...
    Best, Matt

  3. ejkessler | Mar 13, 2014 10:02pm | #3

    Matt,

    I am excited about your Blog and especially this Ultra-Aire SD-12 and all your other equipment recommendations. I am building a house in the Virginia near the Potomac river, which is in area 4 so our areas are different, and we sure do get humidity & rain in summers & cold winters. The house is an ICF full basement Cape Cod style with an open floor plan great room and a 1 bath and 2 BR's in the 2nd floor room truss (I know not the best for efficiency but looks great in the river community).

    I am working very hard on the design to radically air-seal/spray foam insulate the home as well as the top cord or the roof so that any plumbing is in conditioned air space (goal is <2.0 ACH@50 Pa). I was taking notes during one of your presentation on the HVAC systems (or better yet "HAC +V+H"). However I would like your opinion on how, and even were, to place some of the equipment. My equipment selection based on you and others are: VRF mini-split; Venmar HRV or ERV (not sure since I will also use Dehumidifier for summer but need to retain humidity for the winter, to complicated for me, my head hurts); Ultra-Aire SD-12; and also perhaps an Aprilaire Media Cleaner #2210 (not sure about UV Light). So... how do I connect all this stuff. I know the VRF is basically separate; but since I will be using the ERV to remove stale air and feed fresh air ... can I somehow use the ERV distribution tubes to distribute and connect the Dehumidifier into the how deal and also the media cleaner??? Are they best kept entirely separate? Aarrgg... V/r, Eric Kessler

  4. looselumber | Mar 17, 2014 10:59am | #4

    I realize this question is the antithesis of the basis of your article, but up here in the north, humidification during the winter is a necessity. Any suggestions for a system that is compatible with a Unico high velocity forced air system?

  5. humperdink | Mar 17, 2014 02:29pm | #5

    Matt, I live in the Florida Panhandle so dehumidification is necessary every month of the year. I have a relatively new single stage heat pump with variable speed blower which normally does a good job of controlling indoor humidity, except during those periods when there is not much call for heating or cooling. Some of the literature that came with the thermostat warns against running the cooling cycle when the outdoor temperature is 50 or below. Would the split Ultra-Aire system have a similar caution? Also, are the other Ultra-Aire units as noisy as portable dehumidifiers?

  6. rickrobson | Mar 17, 2014 04:12pm | #6

    Great info, Thanks !!!

    The home we built is super energy efficient and also tight (0.02 exchanges per hour by blower door test). We heat and cool with radiant driven by a ground source heat pump. Dehumidification is copper tubing on the walls over windows with a gutter below for drainage. Refrigerant runs through the copper tubes. Cool water in the floor tubing. Nice system but, dehumidification only works when system is running. It runs very little so we don't have enough dehumidification. Now, with your info, I'm weighing these options: 1) changing my controller to run the GS heat pump on dehumidification demand rather than temp so it will run more (will need to valve off hydronic tank so it doesn't get too cold) or, 2) putting in a separate Ultra-Aire. We don't have typical ducting, except, we do have an HRV pulling from 4 location and returning to 1. Could couple into this system I think. It's in the conditioned attic and has a drain line.

    Thoughts?

  7. Matt Risinger | Mar 19, 2014 09:38pm | #7

    @ejkessler: Dang, great questions. First, it sounds like a cool house you are building. Under 2ACH50 is a great goal for air tightness. My initial recommendation would be to run your HRV separate from your HVAC system (go VRF!). Your HVAC+D system is easier to run as a system with the filtration and the Ultra-Aire Dehum in line. Your climate is a bit on the border with needing the cooling benefit of the SD-12. You might be better served with an XT105 as the waste heat inside your conditioned space may not be as big of a deal. That being said I lived outside of DC for seven years and I remember summers being HOT and HUMID! Austin Summers are HOT but not as humid, it's the spring/fall that's a bear hear. 90 degrees outside and 85% RH isn't much fun.
    I hope this helps.
    Matt

  8. ejkessler | Mar 20, 2014 06:44am | #8

    Thanks Matt,

    You really helped push me toward another decision ... the water heater. I was really struggling with the two piece SD-12 and another hole in my foundation plus the added cost, vice the XD105 simplicity and it too was making my head hurt. While I did not want the added heat from the XD105 in my equipment room I was also thinking about a Heat Pump water heater (in combo with a modest PV array) and how it sucked heat out of a room. So perhaps between the added heat of the XD105 and the heat robbing Heat pump water heater all in the same closed equipment room, perhaps it will balance out. thanks.

    But I do have a follow-on regarding the HRV vice ERV issue if I am using the "Ultra-Aire Dehum in line."
    - Which is correct or best, the HRV or the ERV since in the winter the humidity is low and I likely want to retain that at some controlled level in such a tight house (say the 50-60% range)? If I understand the ERV helps retain humidity ... but won't that create problems in line with Ultra-Aire?
    - Do really tight houses really need to worry about too much retained humidity?

    Thanks again!

  9. Matt Risinger | Mar 20, 2014 09:22am | #9

    @looselumber: I've never used a high velocity HVAC system before. I'm not sure about integration. These Ultra-Aire dehums and specifically the SD-12 are pretty simple to duct as a stand-alone system however. You just need a good return and supply grille. Humidity inside a house is generally pretty even (unlike temperature) so one location ducting for the Dehum and you'll be able to handle the whole house easily. Hope that helps. Best, Matt

  10. Matt Risinger | Mar 20, 2014 09:25am | #10

    @rickrobson: I'm not sure I've got much advice on your current system. I'm not a GSHP expert. I would however tell you that a stand-alone application for a Dehumidifier would work very well. The Ultra-Aire SD12 or the all-in-one Dehums like the XT105 are pretty easy to install in a stand-alone duct fashion. One return grille, and one supply and you can easily dehumidify the whole house. That might be the simplest installation for your house. Best, Matt Risinger

  11. Matt Risinger | Mar 20, 2014 09:30am | #11

    @humperdink: I see no reason why this SD-12 would have any problems running below 50 outside. You might call them to verify before purchase, but I don't see why it would have a problem at that outdoor temp. Regarding your sound question, yes these units when running do make noise. The SD-12 is much quieter because the compressor is outside so it's mainly fan noise. The other all-in-one units like the XT105 make more noise as the compressor/condensor is all in one package. Debra Judge Silber did a great "How it Works" article in this months' issue that shows the inner workings of the Ultra-Aire XT105. Here's the link https://www.finehomebuilding.com/how-to/departments/how-it-works/dehumidifiers.aspx
    I've been putting Dehums in my houses for about 4 years now and I've yet to get a noise complaint. Best, Matt

  12. Matt Risinger | Mar 20, 2014 09:37am | #12

    @ejkessler : ERV vs HRV is a frequent question for people in the middle 1/3rd of America like you. North of you is all HRV country, South is all ERV. You probably could go either way. Remember that an ERV is not dehumidifying your inside air. It's simply rejecting SOME of the incoming moisture from the air stream coming from outside. If you are dealing with humidity issues the stand alone Dehum is the way to go. Martin Holiday has a great article on GBA about this topic.
    http://www.greenbuildingadvisor.com/blogs/dept/musings/hrv-or-erv
    Regarding the heat pump water heater and the XT105 Dehum, I think those would work well together in your basement. The Dehum will produce "some" heat and the HPWH will product some cool air when running. Depending on the model you can get 1/3-3/4 Ton of AC when it's making hot water, but remember that it's going to run mainly after hot water events like showers/baths/laundry/etc.
    Hope this helps, Matt

  13. ejkessler | Mar 30, 2014 09:35pm | #13

    Wow Matt,
    That is excellent. I've read a fair number of articles but never heard it stated so clearly that the ERV did not dehumidifying my inside air but that it was only rejecting SOME of the Incoming humidity moisture. Thanks you!

    - So its best to just get the HRV and somehow connect it to the XT105 Dehumidifiers?
    - Do the Venmar HRV and XT105 output/input tubes the same size?
    - should the XT105 be in line Before or After the Venmar HRV ?

    Thanks so much again,
    Eric

  14. ejkessler | Mar 30, 2014 09:55pm | #14

    Sorry Matt,
    in my above question, I forgot to include the Aprilaire Media Cleaner #2210 (not sure about UV Light) and what order/arrangement the media cleaner, Dehumid & HRV all connect?
    Thx,
    Eric

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

More Job Site Diaries

View All
  • Advantages of a High-Performance Heat-Pump Water Heater
  • Wall-Mounted Fan Coil Unit for an Air-to-Water Heat Pump
  • Efficient Home Heating and Cooling
  • HVAC System for a High-Performance Home
View All

Up Next

Video Shorts

Featured Story

Fast, Accurate Wall Framing

A rear addition provides a small-scale example of how to frame efficiently.

Featured Video

SawStop's Portable Tablesaw is Bigger and Better Than Before

The 10-in. Jobsite Saw PRO has a wider table, a new dust-control port, and a more versatile fence, along with the same reliable safety mechanism included in all SawStop tablesaws.

Related Stories

  • FHB Podcast Segment: Finding Hazardous Materials in a Fixer-Upper
  • FHB Podcast Segment: Embodied Greenhouse Gas Emissions and the Building Codes
  • FHB Podcast Segment: Roofing on Commercial vs. Residential Buildings
  • Preservation and Renewal for a Classic

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

Video

View All Videos
  • FHB Podcast Segment: Finding Hazardous Materials in a Fixer-Upper
  • FHB Podcast Segment: Embodied Greenhouse Gas Emissions and the Building Codes
  • FHB Podcast Segment: Roofing on Commercial vs. Residential Buildings
  • A Drip-Free, Through-Window Heat Pump
View All

Design and Planning

View All Design and Planning Articles
  • A Postwar Comeback
  • With Swedish Arts & Crafts Precedent
  • Natural Simplicity
View All Design and Planning Articles

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2025
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data