Henry Gifford Publishes a Book

musingsheader image

Henry Gifford Publishes a Book

In Buildings Don’t Lie, Gifford explains how to read the clues provided by building stains

Posted on Sep 29 2017 by Martin Holladay

Henry Gifford is a plumber with a New York accent, working-class roots, and deep erudition. He’s also a well-known designer of heating, cooling, and ventilation systems.

Gifford is smart, provocative, funny, and ubiquitous. He’s been profiled in The New Yorker; he’s given a presentation at the Building Science Corporation Summer Camp; he was featured in the “Legends of Home Performance” series created by Home Energy magazine; he has published a guest blog on GBA; and he’s been the subject of a GBA interview.

Gifford’s latest accomplishment: he has published a 571-page hardback book called Buildings Don’t Lie. It’s an excellent book.

Stains provide clues

Many of the books I review for GBA (including, for example, Residential Energy by Krigger and Dorsi and Essential Building Science by Racusin) start the same way: with a discussion of how heat, moisture, and air move through building assemblies. Gifford’s book is no exception. You know the drill: the difference between conductionMovement of heat through a material as kinetic energy is transferred from molecule to molecule; the handle of an iron skillet on the stove gets hot due to heat conduction. R-value is a measure of resistance to conductive heat flow., convection, and radiation; how buildings become pressurized or depressurized; and a discussion of vapor diffusionMovement of water vapor through a material; water vapor can diffuse through even solid materials if the permeability is high enough. .

After the obligatory “introduction to building science” chapters, Gifford gets down to the business at hand: teaching us how to look at buildings. His book includes dozens of photos of buildings with a variety of stains — stains caused by water, mold, dust, and efflorescence. The photo captions help train the reader’s eye, leading readers to understand how subtle clues reveal how buildings work — or don’t. Gifford has taken some great photos, and his explanations all ring true.

[Photo credit: Henry Gifford, Buildings Don't Lie.]

For example, Gifford noticed that the pattern of efflorescence on a brick parapet exhibited a “sine wave” shape, or what Gifford calls a “W pattern.” The stain was caused by water leaking through seams in the coping (the cap stones at the top of the parapet). The photo clearly shows that the coping seams occur at regular intervals; each seam in the coping corresponds with a low point of the sine curve wave below the coping. Aha!

As Gifford walks down a New York sidewalk, I imagine the he’s always looking at open windows, the position of window blinds, and the stains running down the sides the brickwork. If Gifford has a walking companion, and if he chooses to share his observations, I can imagine the companion rolling his eyes.

(My mind runs along similar tracks. My wife has told me, “I’m glad I don’t have your brain. When you look at a building, all you see is the roof algae.”)

Laser pointers and mastic

Gifford provides a few excellent tips:

  • On page 46, Gifford explains how you can use a laser pointer to check whether window glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. includes a low-e coatingVery thin metallic coating on glass or plastic window glazing that reduces heat loss through the window; the coating emits less radiant energy (heat radiation), which makes it, in effect, reflective to that heat; boosts a window’s R-value and reduces its U-factor. .
  • On page 120, Gifford suggests that an electrical box can be air sealed by coating the back of the box with duct mastic and fiberglass tape.

The book also makes good use of historical documents. For example, Gifford tells us (on page 143) that “Willis Carrier himself” — the grandfather of air conditioning — “designed the cooling system for the UN building in the late 1940s, just before he died in 1950.”

He also recounts (on page 9) the following anecdote: “When Amelia Grimes married James Joule [the famous English physicist] in 1847, he was still curious about heat and energy, so on their honeymoon in Switzerland he measured the temperature of water at the tops and bottoms of waterfalls. What his measurements showed is not known, but the two of them remained married until Amelia’s death in 1854.”

Points of agreement

Gifford isn’t shy about expressing his opinions, most of which make sense. Like Gifford, I agree that simple window-mounted air conditioners are a good cooling solution in many situations. I agree that shutters and awnings should be functional rather than merely decorative. I agree that most walls need to be protected from rain by a cornice or roof overhang. I agree that in a hot climate, where cooling loads dominate, most windows should face north and south rather than east or west.

Here are some more examples of statements I agree with:

  • “The importance of protecting windows from summer sunlight cannot be overemphasized” (page 44).
  • “The largest portion of a building’s peak cooling load is usually sunlight entering windows.”
    (page 45).
  • “The saying ‘walls need to breathe’ is just an excuse for carelessness” (page 103).
  • “Liquid water’s tendency to cling to surfaces can make it maddeningly difficult to find a roof leak because, when liquid water travels through a building, it usually clings to one surface, then another, on and on down through the building…” (page 131).
  • “Most existing and new buildings are not very airtight and would do a much better job of keeping people comfortable … if they were retrofitted with a good air barrier” (page 146).
  • When it comes to managing the entry of liquid water, “it is always better to rely on gravity than on adhesive” (page 188).
  • “All soil should be considered wet all the time” (page 206).
  • “No air handling equipment, including ducts, should be located in a garage” (page 433).
  • “All ducts should be located completely indoors, which means they should not be in an [unconditioned] attic or [an unconditioned] crawl space” (page 456).

Gifford’s seven commandments

Like Gifford, I often provide advice to architects and builders. I have a reputation for being cranky and opinionated. But it turns out that I’m a wishy-washy lamb compared to Gifford. I may be somewhat cranky, but Gifford is definitely crankier.

Here are some of Gifford’s rules:

  • Never use a crawl space foundation for a new building.
  • Insulate basement walls on the exterior, not the interior.
  • Don’t include a vented unconditioned attic. Instead, design an unvented insulated roof with exterior rigid foam.
  • Never distribute space heat through ducts.
  • Single-family homes should be heated with a boiler; the same boiler should also provide domestic hot water.
  • Design a heating and cooling system that includes room-by-room zoning, and provide a thermostat for every room.
  • ERVs are preferable to HRVs.
  • It’s possible to build an excellent house by following Gifford’s rules. But his advice is much too rigid. Other approaches exist, and work just fine.

    It’s possible to build a good crawl space. It’s possible to insulate basement walls on the interior. It’s possible to design a high-quality forced-air heating system. It’s possible to design a vented unconditioned attic that performs well. You don’t really need a thermostat in every room as long as your building has a good thermal envelope and you avoid excessive solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss.. And an HRV sometimes makes more sense than an ERV.

    Gifford doesn’t explore these options. He failure to do so represents a lost opportunity.

    The Bronx, Brooklyn, Manhattan, Queens, and Staten Island

    For better or worse, much of Gifford’s experience derives from commercial buildings in New York City. He lives in a world of multi-story apartment buildings with elevators, flat roofs, and steel-stud partitions.

    If you live in New York City, you’ll feel right at home with Gifford’s descriptions and advice. But to residential builders working elsewhere in the U.S., Gifford’s urban perspective will seem foreign. Let’s face it: New York City (like New Orleans) isn’t really part of the U.S. It’s a separate country.

    Many of Gifford’s prejudices — his love of hydronic heating systems, his preference for low-slope unvented roof assemblies, his disdain for ventilated unconditioned attics — are based on his New York City roots rather than scientific principles.

    If his book had included a warning — something like, “Most of this advice applies only to commercial buildings” — readers would at least know what they were getting into. But the book includes lots of anecdotes about, and photos of, single-family homes. Readers can only conclude, therefore, that Gifford intended his generalizations to apply to all buildings.

    Hydronic heat and exterior insulation

    Gifford hates forced-air heating systems. It’s a topic he returns to often.

    Because of Gifford's idiosyncratic vocabulary, his arguments against forced-air heating systems are sometimes hard to follow. HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. system designers and HVAC system installers are responsible for a building’s heating system, ventilation system, and cooling system. But Gifford uses the term “HVAC system” to mean “forced-air system.” In this way, he manages to divorce many types of heating systems (for example, hydronic systems or systems that incorporate ductless minisplits) from the HVAC universe. This enforced exile will come as a surprise to most engineers and contractors.

    In one confusing passage, Gifford writes (on page 455), “While HVAC systems” — he is actually talking about forced-air systems, not HVAC systems — “can filter incoming air, they are generally not a good choice because they are complicated and expensive, circulate used air, require a lot of energy, and often require connections to sophisticated fire and smoke alarm systems.”

    Even readers who realize that Gifford is talking about a certain subset of HVAC systems — namely, forced-air systems — will note that his generalization is unsupported. Not all forced-air systems are complicated and expensive. Some are simple and inexpensive.

    Gifford suggests that radiant ceilings are a useful way to cool a building. But unless you’re talking about a narrow subset of commercial properties, this advice doesn’t make sense.

    Gifford also loves exterior insulation. This love affair often leads to unrealistic advice, as when he writes (on page 394), “Digging up a yard to install insulation on the outdoor side of an existing basement wall can be expensive, but it is usually the best way to make the basement healthy and comfortable and the only way to avoid chronic dampness that can otherwise be treated only by operating a dehumidifier. … The house in the photos on this page has an uninsulated basement floor and uninsulated basement walls. The masonry walls conduct a lot of heat to outdoors during the winter, which is why the basement is white in the infrared photo below. … This problem can only be solved by digging up the basement floor and insulating underneath it, and by digging up the soil around the perimeter of the house and insulating the outdoor side of the basement walls.”

    Actually, the problems at this house can all be solved from the interior of the building — at a much lower cost than the suggested solution, which requires an excavator and a jackhammer.


    Unfortunately, Gifford’s book is marred by a number of errors. Some of them are simple misidentifications, as when he misidentifies an awning window as a casement window (page 69), or when he misidentifies rafters as joists (page 401). On page 460, Gifford misidentifies a register as a “grill.” Even if this word were spelled correctly (“grille”), it would still be a misidentification. Registers include integral dampers; grilles do not. (In a typical forced-air system, the supply ducts are usually connected to registers or diffusers, while the return ducts are usually connected to grilles.)

    A roof with eaves but no overhang. [Photo credit: Ecocor]

    The limitations of Gifford's technical vocabulary also arise on page 159, when he writes that “Roof overhangs [are] also known as eaves.” Well, no. Virtually every pitched roof has an eave, but not all pitched roofs have an overhang. If the pitched roof has no overhang, the bottom of the roof slope — where the water leaves the roof and dribbles down the wall — is still called an eave.

    On page 394, Gifford describes troweled-on asphaltic dampproofing as a barrier to liquid water. It isn’t.

    On page 419, Gifford writes that it is “unrealistic” to think that it’s possible to design a vented unconditioned attic that isn’t at risk of ice dams. He goes on to say (on page 423) that the only solution to ice dams is to install rigid foam above the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. . While the installation of exterior rigid foam is a great solution, it’s not the only solution. A well-detailed vented unconditioned attic will not be plagued by ice dams.

    On page 447, Gifford implies that an ERV is a cooling device: “The ERV not only saves a lot of energy — the incoming fresh air is being cooled by the exhaust air — but also is much simpler, smaller, and quieter than an air conditioner of a similar capacity.” In fact, you can’t compare the cooling capacity of an air conditioner with the cooling capacity of an ERV, because an ERV has no cooling capacity. Operating an ERV during the summer raises rather than lowers the temperature of the indoor air. The longer you run the ERV, the more heat you introduce into the house.

    On page 436, Gifford writes that “HVAC systems” — from context, I’m assuming that Gifford is talking about forced-air heating and cooling systems — “are primarily found in office buildings and hospitals.” Actually, forced-air heating and cooling systems are quite common in single-family homes.

    On page 448, Gifford writes that “HVAC systems usually take air from roofs, where equipment is often located.” That may be true in New York City, but it isn’t true for most residential ventilation systems.

    On page 479, Gifford writes that “Air based [heating] systems are often perceived as being inexpensive. But most such systems lack air return ducts. … Most air-based systems have air supply ducts only. They lack ducts to return air to the air handler.” I have no idea why Gifford wrote those words. I first began designing forced-air heating systems back in 1975. At that time I was working for a plumbing and heating system wholesaler in rural Vermont — not a cutting-edge region of the country, by any means. Every forced-air heating system we designed included return air ductwork. This was common practice for residential systems 40 years ago, and it has been common practice all over the country ever since.

    Almost there but not quite

    In some of this book’s passages, Gifford comes tantalizingly close to providing specific guidance to designers and builders — and then backs away before providing essential details. For example, on page 399, he almost delves into the question of determining the minimum R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of continuous exterior wall insulation when you’re trying to keep the wall sheathing above the dew point in winter. He dances around the question, but at the last moment fails to provide the type of detailed, climate-specific advice that builders crave. Instead, he writes, "The more insulation on the outdoor side, the greater the amount of insulation that can be safely added to the indoor side. And the colder the climate, the greater the amount of insulation that needs to be on the outdoor side." Although these sentences are true, as far as they go, they fail to provide enough guidance to designers or builders.

    On page 488, Gifford suggests that a partition stud space can be used as a vertical duct to provide a return air pathway for a forced-air system. He illustrates two transfer grilles — one high on the wall, and the other near the floor, on the other side of the partition. The stud space is 3 1/2 inches deep and 14 1/2 inches wide. But there’s a problem that Gifford doesn’t mention: The dimensions of the stud space are too small; such a stud space can only convey a maximum of 52 cfm — much less than the amount of supply air delivered to the average bedroom.

    On page 430, he advises that central vacuum cleaners should be connected to canisters that are located outside of a building’s thermal envelope — without warning readers that this approach will depressurize the building, putting combustion appliances at risk of backdraftingIndoor air quality problem in which potentially dangerous combustion gases escape into the house instead of going up the chimney..

    Gifford can be wordy and repetitive. He devotes a four-page spread (on pages 388-391) to a series of cartoon-like images showing how workers install exterior rigid foam and new windows — without providing any real architectural details. Gifford could easily have used a single sentence to make the same point.

    [Photo credit: Henry Gifford, Buildings Don't Lie.]

    Some of the book’s stumbles brought a smile to my face. For example, on page 459, there is a photo of a construction worker who evidently visited a manicurist before showing up on the job site. She displays her painted nails with pride. Here’s the punchline: she is shown installing duct mastic without gloves.

    A plague of vagueness

    As I read this book, I wondered, “Who does the author imagine that he’s writing for? Who is the audience?” It appears that Gifford is writing for readers who are ignorant about buildings. He probably isn’t writing for builders, because most builders reading this book will be frustrated by Gifford's unwillingness to use conventional job-site vocabulary or to mention brand names.

    Here are some examples of Gifford’s vagueness:

    • A photo that shows a concrete foundation coated with asphaltic dampproofing (page 41) is described this way: “The basement walls … are both coated on the outdoor side with a black barrier material that is a barrier to both liquid water and water vapor.”
    • A photo that shows the installation of a liquid-applied WRB (page 107) — probably a Sto product — has this caption: “A yellow material is being rolled onto a concrete block wall.”
    • A photo showing Zip sheathing (page 108) describes the material as “wall sheathing panels with a factory-applied material that is a barrier to air and to liquid water but not to water vapor.”
    • The caption for a photo of Georgia Pacific DensGlass panels (page 108) describes the panels as “yellow sheathing panels.”
    • XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation. insulation manufactured by Alside (page 111) is described as “silver-colored foam insulation.”
    • Rather than clearly explaining that most duct insulation consists of fiberglass covered with a polyethylene jacket, Gifford writes (on page 456), “To prevent warm humid air from passing through the duct insulation and condensing on whichever side of the insulation is cold at the moment, the insulation should be covered with barriers to air and to water vapor.” He’s used a lot of words, and the reader is still unsure what he’s talking about.
    • When it comes time to describe different types of ducts, Gifford becomes positively tongue-tied. On page 456, he writes, “Many ducts are made of thin sheets of steel … Other ducts are flexible like vacuum cleaner hoses…” Can you imagine a reader approaching a Home Depot clerk and asking for “ducts made of thin sheets of steel”?
      • This type of writing comes off as cute rather than helpful. Black barrier material? Silver-colored foam? This is obfuscation, not description. What’s wrong with “dampproofing” and “XPS”? Rather than muddying the waters with “thin sheets of steel” and “ducts that are flexible like vacuum cleaner hoses,” it would have been clearer to just say “galvanized ducts” and “flex ducts.”

        Buy this book

        If you’re like me, you’ll find yourself talking back to the author as your read this book, muttering counterarguments. But you’ll also recognize a kindred spirit. Gifford has an intuitive grasp of important building science principles, and an unequaled ability to evaluate building performance from a few subtle clues.

        If you're interested in learning (from an expert) what to look for when your are investigating building mysteries, you should definitely buy this book. (You can buy a copy for $75 by visiting the Buildings Don't Lie website.)

        Study Gifford's photos and captions. If you do, you’ll probably find yourself looking at buildings with a fresh eye.

        Martin Holladay’s previous blog: “Bathroom Design.”

        Click here to follow Martin Holladay on Twitter.

Tags: , ,

Image Credits:

  1. Henry Gifford

Sep 29, 2017 4:56 PM ET

The duct mastic picture rocks!
by Dana Dorsett

The fully-manicured with nail polished look is always what I'm looking for in construction instruction manual! :-)

I wonder how long she managed to keep it out of her hair? (It's a GREAT hair setting gel- lasts for weeks! )

The disconnect reminds me a bit of German automotive repair & maintenance manuals published by the manufacturers back the 1960s & 1970s where the hand model with the shiny-new wrench is wearing a suit coat, complete with cuff links, working on something too clean to have ever been in service. I always dressed to the nines when going to change the oil or adjust the valves on an air-cooled VW, just so I could look as cool the mechanic in the pictures... didn't everybody? :-)

Henry Gifford is a pretty cool customer though, very low key and understated in his delivery. I really liked his presentation here:


"I'm a believer in the theory that air is lighter than water"

Just tellin' it like it is, I guess!

Sep 29, 2017 6:41 PM ET

Anyone know a good editor?
by Charlie Sullivan

I suspect Martin has plenty to do already, but I can't help but think that it would be better for everyone if they'd hire him to do a pass at editing these books before printing the first edition. But I'm glad to hear there's plenty of good stuff in there.

It's taken more than 150 years, but someone finally followed up on Joule's waterfall measurements: a careful-sounding study in 2015 found a 1 to 4 C rise in temperature for a 350 m drop, of which 0.8 C can be accounted for by the analysis Joule invented.


Sep 30, 2017 6:06 AM ET

Response to Dana Dorsett
by Martin Holladay

The well-dressed European worker is not just a relic from the 1960s. He's still alive in Switzerland.

There's at least one guy like that left -- I call him "Vest Man." Siga hired Vest Man for almost all of their photos. I think he started out in a three-piece suit, but perhaps the photographer decided that was overkill. He took off his jacket -- maybe it was Casual Friday in Zurich -- and he became Vest Man.


SIGA interior 3 - membrane seam.jpg

Sep 30, 2017 6:09 AM ET

Response to Charlie Sullivan
by Martin Holladay

I'd like to imagine that somewhere, James Joule is smiling. I'm glad someone was able to confirm his hunch about waterfall temperatures. Thanks for the link.

Oct 5, 2017 5:44 PM ET

source your photo?
by user-6930238

Hi Martin:
The photo of "where water leaves the roof and dribbles down the wall" is not in Gifford's book. Would you clarify that it's your own illustration so as to not be misleading?
Thank you!
Leah Kreger, RA

Oct 5, 2017 8:00 PM ET

Photo credit
by Martin Holladay

The photo credit for the roof photo was inadvertently dropped. I've corrected the omission.

Oct 29, 2017 12:37 PM ET

"A stumble"?
by Anne Lawrence

Why is a photograph of a woman applying duct mastic, "a stumble"? If it were a photo of a man not wearing gloves, would that be worthy of inclusion as "the punchline"? As a woman who has worked many years in construction, including applying duct mastic (with gloves), what is the point of dedicating ~10% of the length of this review to this one photo? Is it illustrating a pitfall that is repeated throughout the book? I don't see that, as there are few photos of "hands-on" installation in the book. Does it help the reader decide fairly whether to read or buy this book? I think not.

I see this as possibly private job site humor, not worthy of a book review intended for an inclusive audience. Perhaps instead, Gifford was the one who was inclusive, using a variety of models.

Oct 29, 2017 1:57 PM ET

Edited Oct 29, 2017 1:59 PM ET.

Response to Anne Lawrence
by Martin Holladay

I can assure you that I was simply making a mastic joke, which is famously messy to apply. I was also making a dig at posed photos that don't involve actual construction workers.

I have the utmost respect for women who work in construction. When I needed help finishing my own house, due to compelling life circumstances, I hired Polly Jerome, one of the best finish carpenters in northern Vermont, to help me. Polly wears gloves on the job site.

Oct 29, 2017 4:18 PM ET

by Malcolm Taylor

As a woman in the construction trades I'm sure you have encountered a fair amount of lamentable sexism during your career, but you are fishing up the wrong river on this one. Martin is a vociferous defender of women. Read everything you can of his writings. You won't find anything to reproach him with.

i've put my fair share of mastic, acoustical sealant and roof goo on while not wearing gloves. But that's just me being stupid.

Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!