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Musings of an Energy Nerd

Ten Questions for Joe Lstiburek

I recently got a chance to interview one of the country's leading building scientists

Dr. Joseph Lstiburek is a principal at Building Science Corporation in Westford, Massachusetts. [Photo courtesy of Building Science Corp.]

Even back in 1999, when I was an unknown editor at the Journal of Light Construction, Joseph Lstiburek, a principal at the Building Science Corporation in Massachusetts, graciously answered my questions about heat flow, air flow, moisture movement, and building materials. Since those early years, I’ve interviewed Lstiburek dozens of times, and he’s never failed to enlighten me (and sometimes, surprise me).

Lstiburek’s answers to ten recent questions are presented below.

(1) Compared to 40 years ago, are residential builders in the U.S. doing a better job?

A. Yes and no. They have a much better understanding of how things work, but the skill set of people doing the work is not as good as it was. The business grew faster than the available school of skilled talent. We used to have apprenticeships, and people had time to learn fundamental skills. That’s not happening anymore. The builders are aware of that, but there is no easy answer that I can see. But builders have a better understanding of how things work—things like indoor air quality, combustion safety, water management, thermal management, and comfort. All of this is much better understood by the day-to-day builder than 40 years ago. I used to be a builder, and—I can’t believe I’m saying this about the 1970s—back then we were skilled at our skill sets. But we didn’t know how things worked. Today’s builder is very sophisticated in terms of financial management, scheduling, and how things work. The problem is delivering. We don’t have the skills to do it.

(2) What aspects of residential building in the U.S. are still frustratingly sloppy or wrong?

A. I’m very disappointed with mechanical systems—heating, cooling, and ventilation. We have insanely good pieces—we have good equipment. What we can…

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  1. Expert Member
    Malcolm Taylor | | #1

    Joe speaks sense. Too bad he's a Leafs fan though.

  2. William Hill | | #2

    Oh wow, two of my favorite Building Scientists/writers in one place! What a fantastic gift for the New Year! Thank you so much, Martin Holladay and Dr. Joe.

    The only thing I would disagree with is Martin referring to himself as "... an unknown editor at the Journal of Light Construction." Yeah, OK, but before that you were the first person I would go to for new information, opening up every issue of Energy Design Update with great anticipation.

    Please don't underestimate the impact you have had on the understanding of Building Science in this country, Martin. Yeah, Dr. Joe had an impact, but ya' know he's a Canadian. It took you, Martin, to make it possible for the gospel according to Joe to be spread in the USA.

    All the best to both of you!

    Bill Hill

  3. John Prospect | | #3

    Thanks to both Martin and Joe for a great interview. Always fun to read Joe's thoughts (on pretty much anything).

  4. qofmiwok | | #4

    Interesting that Joe says "as good of windows as you can afford, and more continuous insulation" because in other interviews he seems to support the "pretty good house" idea and being economically reasonable instead of taking things to the extreme. In CZ 6B I'm planning 2" exterior insulation over 2x6 walls, and R6-7 windows. I wonder if he'd think I should do 3" and R8. 4" and R9? 5" and R10? If I can afford it, what's the limit? (And let's face it, anyone building a custom house "can" afford it if it is the priority.)

    1. GBA Editor
      Martin Holladay | | #5

      Joe Lstiburek expressed his personal regret that he didn't include more exterior rigid foam on the walls when he remodeled his house. He could have afforded thicker foam, and he regrets his decision to choose thinner foam -- due in part to the fact that Joe Lstiburek is obsessed with home performance. Only you can decide whether you fall into that category.

      For more information on this topic, see "How Much Insulation Is Too Much?"

      1. qofmiwok | | #6

        Thanks for the link. But it really was focused on energy savings as opposed to comfort and building sciences issues like condensation and mold. My guess, after reading / watching Joe quite a bit, is that he isn't basing his responses on cost/benefit payback but on these other issues. it would be interesting to know for sure.

        1. Inger Peters | | #10

          So perhaps the premise of the original interview question is relevant? i.e. If you were building a "code compliant house" and suddenly "$30,000 fell in your lap"? Given that the question doesn't have any time component, I appreciate the focused answer: CI and good windows. (if they weren't already installed). Thanks

  5. Derek Maxwell | | #7

    Yes and No. As a young builder who got a late start I am here to learn and I am so grateful for the resources here and that Dr. Joe has published with BSC. It’s true, jobs are complicated but nobody seems to know what they are doing in a big picture sense. I also agree with Mechanical being one of the weakest links, like Lstiburek mentioned we aren’t training people as well as we need to and mechanical systems are only getting more complex.
    I live in Minnesota and I am currently working on a job with 2” of exterior insulation and no one who is on the job has ever done or barely even seen exterior insulation. That is really concerning to me, I mean it gets cold here and then it gets hot, seems like insulation would be a good idea.

  6. Doug White | | #8

    Thsi is why prefabbed walls and ceilings are the way to go

    As for the basement dictum, that assumes you have a large flat lot. While a good basement is hard/not cheap to build dry and warm, it really facilitates HVAC ducts . Wiring, etc. not to mention incalculable value for sequestering noisy teenagers and ones shop. And if you cant do a slab, do a full basement rather than crawl space-they are a disaster in multiple ways. THink of a basement a crawl space you cna stand up in, insulate and seal well, and a Cost effective unless you have low water table etc

  7. T. Barker | | #9

    (7) If a client who is building a new home, aiming at code minimum performance, suddenly discovers an extra $30,000 in his budget, where should he spend the money?
    J. Lstiburek:
    A. Continuous insulation and the best windows he can afford at the time. Everything else can be changed cheaply later.


    Unfortunately, in my experience, the whole windows and doors industry is a racket. Essentially three major glass/IGU manufacturers in all of North America, 10,000 so-called window manufacturers, and maybe 20 of those that are able to produce a better product than I could make in my garage if I bought the IGU. OK, I'm exaggerating the last point ... but not much.

    Then when you try to focus on high performance (I mean R8-10, not R3 or4) the list of reputable manufacturers with some history behind them and good distribution across the country drops almost to zero.

    First you wade through the marketing BS and try to figure out the different models and series for a particular manufacturer. Many times you're none the wiser until you call a sales person. Ask a few questions beyond price and color, and you have to be shuffled to the deepest echelons of technical support to maybe get an answer. They don't even have their jam details/drawings/options, etc. readily available in any organized form. Sure some of the bigger websites have some of that information, but most times it's half there and half correct. A "specialist" in Architectural support has to get back to you and dig up the information like it was the first time anyone ever asked. Yet everyone who designs/specs. or installs that window (properly) needs that information. It is shocking! Ask about performance specifications, and you get a smattering of information, none of it comprehensive.

    If you're already familiar with your favorite brand and order the same windows and doors every time, no problem. But try to look at some high performance options or design a different look for a finished jam extension or thick wall window and door package. Ask their Architectural support person (if they have one) the actual dimensions of their standard door slabs because you're going to specify a custom frame. These people are in the industry and they have no idea without digging and getting back to you later. I repeat, it is shocking.

    They won't let you buy direct, or have access to their online system so you can see where the price break points are for dimensions or shape ratios, or optional features. Yes, eventually you make contact with one of their better support people and sometimes they can give you some general guidelines. But you have to call a dealer to get the nitty gritty - which means you're going to talk to some dude at the contractor desk (if you're lucky) at a lumber supply store who may not have been on their system for a few months. I heard there was this thing called online ordering? I wonder when that will come to the window and door industry? Menards actually has a pretty good online window and door ordering system that anyone can use. But you can't get high performance at Menards.

    They want to support their legacy dealer network. One of the biggest weak spots in the industry in my opinion. For many of those dealers it's all about renovations and replacement windows. What can they sell to someone to replace their 1970 windows and update the vinyl siding and make a full time business out of installation fees. They would have you believe installing windows is like some highly intricate piece of surgery. But then the next day - and this is a true story - I go to my local lumber supply to pick up materials and they're short staffed in the yard because the two part time kids normally there got sent out on a window install. Seriously.

    End of rant. Joe is still right. Joe is always right. Continuous exterior insulation and the best windows you can afford.

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