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Don’t Do HVAC to Me

Henry Gifford Wearing A Psychrometric Chart T-shirt

One talk at the 2012 Building Science Summer Camp stood out above all the others. The last speaker on Tuesday was Henry Gifford. (Yes, that Henry Gifford!) When he was done, the majority of the audience stood and applauded. The next morning, camp counselor Joe Lstiburek told us there have been four standing ovations at Summer Camp. Henry Gifford has gotten two of them.

His talk this year wasn’t about the US Green Building Council (USGBC), their LEED program, or his lawsuit against them, although someone did ask about it during the Q&A. He did start with a list of acronyms and definitions, though, which included the new designation, LEED PP, for LEED Plaque Peddler.

No, he spoke mainly about the need for radical simplicity in the world of HVAC. He showed and discussed many problems in the world of HVAC and some of the ways he solves problems for his clients in New York City.

A little background: Henry didn’t come into the world of heating, ventilating, and air conditioning system design the normal way. He began as an owner of apartment buildings. A common feature of NYC buildings in winter is open windows because of overheating rooms. That bothered him, especially as a building owner.

It bothered him enough that he started solving problems so that the people in the buildings didn’t have to open the windows on those cold days. Now he’s one of the most highly regarded mechanical systems designers and installers in the country. In fact, I had lunch a few weeks ago with a retired engineer who wrote a book on psychrometrics, and he said he’d probably lose a debate on thermodynamics with Henry. That’s high praise! (Speaking of psychrometrics, did you notice Henry’s T-shirt in the photo above?)

In his talk, he spent a while discussing thermostats. “If you don’t have a thermostat in every room, you’re not even in the ballgame,” he said about large buildings with boilers and hydronic distribution. But that’s not enough because he showed plenty of examples of thermostats set up to fail: sensors installed near heat sources, set up incorrectly, outdoor sensors in the sun, and on and on.

He attributes the problem to a lack of design. No one shows on the plans where the thermostats go, so the people with the least training and pay make decisions that don’t turn out well. He wasn’t blaming them, though. “People stoop to the level of the expectations that society puts on them,” he said. There’s no expectation of how to do this properly, no guidance, and evidently most people just accept the poor results without question.

Radical simplicity. Noticing the obvious is hard to do, you know. But it makes improvement easy. That’s Henry’s game in New York.

He ended his session with a call for separating heating, ventilating, and air conditioning systems. He claims that when we combine these three separate functions, we introduce all kinds of problems. For cooling, he discussed ductless mini-splits and radiant cooling ceiling tiles. To be clear, Henry focuses on apartment, commercial, and institutuional buildings, not single-family homes.

This is the first conference I’ve ever been to where a speaker led the audience in a cheer. Near the end, Henry took us through the cheer in the slide below to hammer home his point. (Note: You have to read the words in a heavy New York accent to get the full effect.)

building science summer camp 2012 hvac cheer henry gifford

I do think separating ventilation from heating and cooling is a good idea, but here in the Southeast, if you’re installing a duct system for forced-air distribution, it makes sense to use it for both heating and cooling. Of course, the type of building you’re looking at makes a big difference, and some things that work in larger buildings like the ones Gifford spoke about won’t work in single-family homes. Or they might work but not be cost effective.

What do you think? This is a big, important discussion. Yes, he was talking mainly about larger buildings, but it’s good to take a step back and look at what’s the best way to do things in different climate zones, different sizes and types of buildings, new versus existing homes, and different types of enclosures.


Allison A. Bailes III, PhD is a speaker, writer, building science consultant, and the founder of Energy Vanguard in Decatur, Georgia. He has a doctorate in physics and writes the Energy Vanguard Blog. He also has a book on building science coming out in the fall of 2022. You can follow him on Twitter at @EnergyVanguard.


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This Post Has 22 Comments

  1. Tough crowd to impress….any
    Tough crowd to impress….any videos available of the presentation?

  2. It would be interesting to
    It would be interesting to hear his arguments about his mantra for the southeast climate. In some crawl spaces I’ve been in, there’s hardly enough room to crawl around the dual-duty ductwork that’s already there! And zoning every individual room (especially with what some folks see as eyesore mini-split air handlers) seems excessive…but, then again, most advancements that eventually become routine started out as crazy-talk…

  3. Dixie Mantra 
    Dixie Mantra 
    GIVE ME AN E (enclosure)  
    GIVE ME SOME V (ventilation) 
    GIVE ME SOME D (dehumidification) 
    GIVE ME SOME HAC (minisplits) 

  4. I work leaky brownstones in
    I work leaky brownstones in Brooklyn where it is difficult to separate out the three. How you do you feel about using the mini splits for both heating and cooling where you have to oversizethe units for heating? Should they still be able to operate  
    efficiently in the cooling mode and  
    still remove the humidity?

  5. What the heck are radiant
    What the heck are radiant ceiling cooling tiles? I think there’s a blog entry in that. 
    As a previous comment mentioned, the next thing always starts as crazy talk. (Horseless carriages – those noisy things?) 
    That said, radical simplicity to me is not completely separate heating and cooling systems (the ventilation can be separate). Who’s going to pay for this? In NYC high rises I can see making it work, but in single family houses if you already have a duct system, why not run both? I’m open to being persuaded, but I definitely need some persuasion. 
    One thing that would be good is better load balancing. I don’t care how good you are, it’s tough to get heating and cooling exactly right in the same house with the same duct system because the load varies depending on the season. 2 systems would help this. 
    As usual, I feel like the theory is being discussed without enough regard to cost. As a shell contractor there are some improvements I don’t really bother with because I don’t feel them to be cost effective (bang for the buck). The new home industry definitely keeps an eye on this. 
    Fiberglass insulation is still used in walls because it’s cheap. HVAC is just that because it’s cheap. Blown insulation beats batts because, well, it’s cheap (it also performs better).  
    On the flip side, a few people have houses like me with radiant heat. If I eventually install AC over the howling protests of my wife, it will be a mini split system with separate thermostats. 
    Still, how do we make this cost effective on single family homes? Is it really? Is there a long term payback to splitting heating and cooling? 
    PS Once again, jealousy at not hearing something at BSCamp is turning me green.

  6. Allison, 

    Could you please expand on the thermostats set to fail and locations? or maybe a new blog?

  7. and the additional cost per
    and the additional cost per home for seperating the H, the V, and the AC would be…..? I have a feeling this would cost alot of money up front.  
    You know, we can design cars that would enable you to live after hitting a wall at 100 mph. I truly appreciate advancements in vehicle safety but who could afford a miniature tank that costs a hundred grand? Likewise, I enjoy most great home improvement ideas but I always ask, at what cost?

  8. Separating two systems will
    Separating two systems will often allow each to perform better, at a price. Heating and cooling via the same ducts, results in airflow which is non-optimum because the heating problem often has a different solution (measured in CFM) from the cooling problem. The result is a compromise which usually shortchanges one or the other. 
    Some problems can be traced to low ACH (air changes/hour) with the symptom being inferior control of heating, cooling, and/or dehumidification. Thinking about ventilation separately from heating/cooling would be a solution for this real world problem.  
    Thermostats in every room? Tell me more. It starts out sounding like theory trumping economy and practice. Perhaps moveable wireless stats are some kind of real world solution.

  9. Not surprising that someone
    Not surprising that someone with a background in multifamily buildings would note separating systems and issues with T-stat locations as primary concerns. On a recent multifamily audit we found the only T-stat for the 10hp swamp cooling system located inside a cramped apartment in the SE corner of the building. The ventilation system was separate and dismally undersized. The systems were also, not surprisingly, installed by two different contractors. In cases like these, minisplits make a lot of sense, with the added benefit (to the building owner) of shifting the cooling costs over to the tenants. Now the ROI is looking pretty enticing.

  10. I think everyone is
    I think everyone is misinterpreting the talk. Henry was not talking about single family homes — he was talking about multifamily and small commercial buildings. It makes a lot of sense with a central boiler in a 60 unit building to have thermostats on the radiators. But this has nothing to do with a single family house.

  11. I built my own place in ’85,
    I built my own place in ’85, 2050 sq ft, single story ranch, “S” side faces Ohio River so for pan view, lots of dble-pane glass doors, full length windows, hi ceilings, 2X6 walls, attic FG batts + blo ins. I just knew, intuitively that ducts in attic was out, vented crawl was out. HVAC in gar was out, ht pmps out, any open flame in gar out. So…the crawl is concrete floor, also used as return plenum , HVAC in crawl, hi E cond furn,bills always lower than comparable ftage, added on ’04, now have 3500 sq ft, 2 furns in crawl, 2 AC’s, mo hi ceilings, 3 stats, still do’n betta anybody, I’m so dang smart it hurts my big head to hear the piddly stuff. moedad71, call me!

  12. “If you don’t have a
    “If you don’t have a thermostat in every room, you’re not even in the ballgame” 
    Easy to say… (especially when in cooling dominated climates) 
    Michael B wrote: 
    > I think everyone is misinterpreting the talk. Henry was not talking about single family homes — he was talking about multifamily and small commercial buildings.  
    Thanks for clarifying.

  13. Michael Blasnik<
    Michael Blasnik: Yeah, that’s my fault. I tried to give the context by discussing Henry’s background in NYC apartment buildings, but I didn’t tie that well enough to the Don’t do HVAC to me theme. Once I’m done with the comments here, I’ll go back and fix that in the article. 
    Lance: I haven’t seen one posted yet, but John Brooks posted the link to the video of his earlier Summer Camp talk a few years ago: Henry Gifford 2008 Summer Camp video 
    Bradley: True. In new homes where you can make a really good enclosure, the heating & cooling can be greatly downsized, though, and that solves some of those problems. 
    John B.: I like your cheer! And thanks for the link to the video of his earlier talk, which I embedded above. 
    Bob G.: Yeah, I like mini-split heat pumps that can both heat and cool. With variable refrigerant flow, oversizing the cooling system isn’t as big a deal because the capacity changes to meet the load. 
    Nate A.: Yes, I’ll be writing about radiant cooling. I’ve been stewing on that one for a while. Good points about separating things out. As Michael pointed out, I didn’t really give the proper context and it doesn’t make as much sense for single-family homes. Cost-effectiveness is great for larger buildings, though. 
    Armando: I don’t remember all the examples, but one was near an electrical box that gave off a lot of heat. One building had 3 t-stats right next to each other but serving 3 different parts of the building. Another was inside housing of baseboard radiator. 
    dave: Cost is very important for most of us, of course. In big, poorly performing buildings, there’s a quick payback. In smaller buildings and single-family homes, maybe not. 
    M. Johnson: Thermostats in every room is for homes/buildings with boilers and hydronic distribution. Sorry, I should’ve had that in the article. The radical simplicity refers to Henry’s looking at how things are in buildings and trying to figure out the best way to get them where they need to be. 
    Thomas A.: Great point, and the kind of stuff Henry does. 
    moedaddy71: Glad that works for you, but I’d worry about using the crawl space as a return plenum. 
    David B.: Sorry, as I said to M. Johnson above, Henry was talking about large buildings with boilers and hydronic distribution. 

  14. Give me a D (Deferential to
    Give me a D (Deferential to historic import…) 
    Give me an E (Energy, of course…) 
    Give me an R (Reduction…the end result, not the treatment) 
    But don’t do DER (Deep Energy Retrofit…or more precisely, the conventional work methods often used in achieving deep energy reductions) to me! 
    There. That’s my cheer. Will you be sending me a psychrometric tee shirt? 😉

  15. Hi – 

    Hi – 
    Yes, I was specifically talking about large buildings, “large” meaning it is hard to avoid overheating or overcooling parts of the building, at least partly because the mechanical system gets very complicated as the building gets larger. But, I know of several single family homes, including some I have had some influence on, which have mini splits on the wall for cooling, or in the case of a high end brownstone mini splits hidden behind grills in the ceiling for cooling, and hot water to radiators for heating. Yes, thermost in each room. Yes, the mini splits could do heating also, but partly because of cheap gas and 25 cent electricity in NYC, and partly to avoid hot air heat, people pay for seperate heating and cooling. And, yes, a separate ventilation system. I also showed valences, which are baseboards upside down on the ceiling, which do both heating and cooling with water, and mentioned a 101 family building I am designing with mini splits for both heating and cooling, but that building will be very airtight and very well insulated, and low income, not luxury conditions, in which case the cost of another heating system might be justified.  
    Another way of radically simplifying things is to simplify the controls, because if you need all that fancy digital stuff, probably the mechanical stuff is also way too complicated to have a high chance of working, or working well for long. One great way to not need digital controls is to not do HVAC into combined systems – let the ventilation run 24 hours, or on/off or hi/lo on motion or CO2. (I usually do code minimum CFM, which means smaller and quieter and cheaper equipment, and requires 24 hour operation). After that, no more ducts, just Copper pipes for heating and cooling, usually heating by hot water, cooling by either cold water or by freon. Yeah, simple, cheap, easy, and zero square footage taken out of offices for fan rooms. 
    Henry Gifford

  16. Hi Allison Bailes…was
    Hi Allison Bailes…was wonder’n why the worry ’bout using crawl as return plenum?

  17. Seriously, though: All my
    Seriously, though: All my wise-assery aside, I thought this was an excellent article, and I’m intrigued by Henry’s reasoning.  
    In planning my own solutions for updated HVAC systems in two single family homes of mine (cold climate), I’ll be giving some serious thought to separating HVAC subsystems out, and see if it makes sense for my situation. Thanks!

  18. Great summary, Allison. The
    Great summary, Allison. The Northern California attendees of BSCamp especially loved Henry’s acronyms: 
    KWH/M2/YRm= Energy Use/Yr (Measured) versus 
    KWH/M2/YRm= Energy Use/Yr (Modeled).  
    Did everyone catch the difference? Yep, out here in CA, they actually don’t think there is any, either. We live in an imaginary state, so we might as well use the same acronym, right?  
    Oh and runner up was: 
    ATRst= Average Truth Ratio (solar thermal) and 
    ATRpv= Average Truth Ration (Photovoltaic) 
    Great talk, Henry. I’m the guy who asked you why you were wearing the Psych shirt, and where I can get one. I’m still hoping one shows up someday. 🙂

  19. We have had good luck with
    We have had good luck with reversible geothermal chillers. Radiant floor heat with water dicoil air handlers, you just have to have a a/h you can slow the cfm way down to allow for dehumidification

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